AN ABSTRACT OF THE THESIS OF
Michael Amaranthus for the degree of Doctor of Philosophy in Forest Science presented on March 31. 1989
Title: THE ROLE OF ECTOMYCOR}IIZAL FUNGI IN ECOSYSIEM RECOVERY
FOLLOWING FOREST DISTJRBAN
Abstract annroved
(
Dave Perry
The effect of the abundance and rapidity of ectomycorrhiza and root tip formation on conifer seedling survival and growth was investigated on disturbed forest sites in southwest Oregon and northern California. Experiments were conducted over a range of community types and environmental conditions. A range of sources of transfer soil were evaluated to offset disturbance-related reductions in ectomycorrhiza formation.
We established different levels of native mycorrhizae by growing seedlings in soils from either (a) a poorly restocked clearcut in southwest Oregon, or (b) forest adjacent to the clearcut.. At the time of outplanting, only 4% of root tips were mycorrhizal on seedling grown in clearcut soils, while 42% were mycorrhizal on seedlings grown in forest soils. There were significant differences in growth following outplanting. Seedlings greenhouse-grown in clearcut soil averaged nearly 44% less basal area growth and
14% less height growth than those greenhouse-grown in forest soil.
Survival and mycorrhiza formation differed among Douglas-fir seedlings planted in three adjacent community types-whiteleaf manzanita, annual grass meadow, and an open stand of Oregon white oak. Second-year survival averaged 92%, 43%, and 12% for seedlings planted on the manzanita, meadow, and oak sites, respectively. Growth differences generally paralleled survival differences. Growth of seedlings on the manzanita site was substantially increased by the addition of unpasteurized machone soil, nearly tripling the number of mycorrhizal root tips formed.

Mycorrhiza formation and conifer seedling performance was examined over a range of sources of transfer soils and environmental conditions on three old and unsucessfully reforested clearcuts. At Cedar Camp, a high elevation (1720m) southerly slope with sandy soils, transfer of plantation soils increased 1 st-year Douglas-fir seedling survival 50%, doubled mycorrhiza formation and tripled seedling basal area growth. Soil from mature forest did not improve growth and survival. Less dramatic effects owing to soil transfer were evident on the other sites, which were lower in elevation had greater water holding capacity, and where woody shrubs had apparently preserved mycorrhizal fungi.
In another study, seedlings receiving plantation soil transfer at Cedar Camp had
62% more root tips than controls six weeks after ouplanting; however differences were no longer statistically significant 15 weeks after planting. Seedlings receiving transferred soil had the most mycorrhizal colonization. Of seedlings receiving transfer soil, 36.6% survived the first growing season, compared to 11.3% of control seedlings.

The Role of Ectomycorrhizal Fungi in Ecosystem Recovery
Following Forest Disturbance by
Michael Amaranthus
A THESIS submitted to
Oregon State University in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
Completed March 31, 1989
Commencement June 1989

ACKNOWLEDGEMENTS
I wish to express my gratitude to the many people who have helped me during the course of my thesis research. I would like to thank Dr. David Perry for his friendship, guidance and support. My special appreciation to Drs. Jim Trappe, Randy Molina and
Mike Castellano for their encouragement and fellowship and the generous use of their excellent facilities at the Forest Sciences Laboratory, Corvallis. My thanks to Deborah
Parrish and Carolyn Choquette for their many contributions and enthusiaism for the project. My thanks to Gretchen Bracher for her excellent graphic support. My thanks to my family for their understanding and support throughout my graduate career. I appreciate the cooperation of the Siskiyou National Forest without which this research could have never been accomplished.
Some final thoughts on this research project and the people that made it possible.
Just as forest communities often contain attributes not easily predicted from separate studies of individual species, so too an emerging view of the forest ecosystem does not occur from the workings of an individual scientist. No forest scientist could be possibly competant enough in the ecology, life history and taxonomy of the members of a forest community to thoroughly understand them as a unit. An open research environment greatly aids the scientist in understanding the elaborate mechanisms by which forest communities originate, develop and maintain themselves. In the Forest Sciences Laboratory, Corvallis, this sort of research succeeds, as an attribute of a synergism between
Oregon State University and the Forest Service Research and Management. We generally are fully cognizant of the complex interrelationships of nature. Often, however, we do not fully appreciate the commensurate interrelations needed for the purpose of its investigation. Complex interactions at the ecosystem level can only be understood at the human level. My thanks to you all.
I dedicate this thesis to my grandfather, Ernesto Amaranthus, who spawned and nurtured my interest in the natural world and to my sons, Nicholas and Zachary, for a forest vision through children's eyes.

TABLE OF CONTENTS
INTRODUCTION
CHAPTER I
REDUCED MYCORPJ{JZA FORMATION INFLUENCES FIRST-YEAR GROWTH
OF OUTPLANTED SEEDLINGS ON A SOUTHWEST OREGON CLEARCUT
Page
Abstract
Introduction
Methods
Site description
Field procedure
Results
Number of mycorrhizae and seedling size prior to outplanting
Growth survival and mycorrhiza formation after outplanting
Discussion
Acknowledgements
Literature Cited
4
6
6
5
6
8
8
8
13
14
15
CHAPTER II
INTERACTING EFFECTS OF VEGETATION TYPE AND PACIFIC MADRONE
SOIL INOCULA ON SURVIVAL, GROWTH AND MYCORR}IZA FORMATION OF
DOUGLAS-FIR
Abstract
Introduction
Methods
Site description
Field procedure
Analysis
Results
Discussion
Acknowledgements
Literature Cited
Page
17
19
21
21
21
23
24
32
34
35

CHAPTER III
EFFECT OF SOIL TRANSFER ON ECTOMYCORRHIZA FORMATION AND
SURVIVAL AND GROWTH OF CONIFER SEEDLINGS ON OLD NONRE-
FORESTED CLEARCUTS
Page
Abstract
Introduction
Methods
Site description
Soil transfer
Soil nutrients and moisture
Statistical analysis
Results
Soil transfer
Soil nutrients and moisture
Discussion
44
47
47
48
48
40
42
44
44
48
Acknowledgements
Literature Cited
55
58
59
CHAPTER IV
RAPID ROOT TIP AND MYCORRITJZA FORMATION AND INCREASED
SURVIVAL OF DOUGLAS-FIR SEEDLINGS AFTER SOIL TRANSFER
Page
62
Abstract
Introduction
Methods
Site description
Planting methods
Statistical analysis
Results
Discussion
Acknowledgements
Literature Cited
63
64
64
64
65
66
68
70
71

CONCLUSIONS AND SYNTHESIS
Type and severity of disturbance
Diversity of soil organisms
Climatic conditions
Biotic conditions
Effect of non-hosts over time
Bibliography
Page
74
76
76
77
79
81

LIST OF FIGURES
Figure
CHAPTER I
I-i.
Numbers of mycorrhizal and nonmycorrhizal root tips before outplanting for seedlings grown in soils from clearcut and forest
Page
9
1-2.
Basal area and seedling height before outplanting for seedlings grown in soils from clearcut and forest 10
1-3.
Basal area growth, leader growth, and percentage survival of seedlings greenhouse-grown in soils from clearcut and forest, 7 months after outplanting to the clearcut
11
1-4.
Mycorrhizal and nonmycorrhizal root tip formation of seedlings greenhousegrown in soils from clearcut and forest, 8 months after outplanting to the clearcut
12
IT-i.
CHAPTER II
Soil nutrients and pH for the four study sites. Seedlings were planted on the manzanita, meadow, and oak sites; soil was transferred from the madrone site 25
11-2 Soil moisture during the 1985 growing season (year 1) on the manzanita, meadow, and oak sites 26

11-3 Percent of seedlings surviving in years 1 and 2, by vegetation type and, within each type, by soil transfer treatment 27
11-4 Average basal-area growth per seedling in years 1 and 2, by vegetation type and, within each type, by soil transfer treatment 28
11-5 Average seeding height growth in years 1 and 2, by vegetation type and, within each type, by soil transfer treatment 29
11-6 Average seedling mycorrhiza formation at the end of the 1985 growing season
(year 1) by vegetative type and within each type by soil transfer treatment 31
111-1
CHAPTER III
Mean 1st-year basal area growth, survival, number of mycorrhizal root tips, and degree of mycorrhizal branching of Douglas-fir seedlings following soil transfer at Cedar Camp 50
111-2 Mean 1st-year basal area growth, survival, number of mycorrhizal root tips, and degree of mycorrhizal branching of Douglas-fir seedlings following soil transfer at Crazy Peak
51
111-3 Mean 1st-year basal area growth, survival, number of mycorrhizal root tips, and degree of mycorrhizal branching of Douglas-fir seedlings following soil transfer at Wood Creek 52
111-4 Soil moisture at the 35-cm depth and precipitation at Cedar Camp and
Crazy Peak throughout the 1985 growing season 54

LIST OF TABLES
Table
CHAPTER III
Ill-i Site characteristics of the three clearcut and broadcast-burned study sites in southern Oregon and northern California.
Page
45
111-2 Mean pH and nutrient levels from unreforested clearcut, plantation and mature-forest soils.
53
IV- 1
CHAPTER IV
Response of Douglas-fir seedlings to soil transferred from an established plantation 67

Successful reforestation depends on the capacity of tree seedlings to rapidly capture site resources. Early growth assures space, resources, and hence the vigor to survive climatic stress and resist pests and pathogens. Mycorrhizae improve seedling survival and growth by enhancing nutrient uptake, water, lengthening root life and protecting against pathogens (Harley and Smith 1983). Trees forming ectomycorrhizae include most of the important commercial species in temperate and boreal zones and 70% of the species planted in the tropics (Evans 1982). Ectomycorrhizae are generally thought to be crucial, if not for survival, at least for acceptable growth. Pines and oaks planted on sites that have not previously supported ectomycorrhizae die or do not grow well (Mikola 1970, 1973; Marx 1980).
Most studies find fewer mycorrhizae formed on highly disturbed than undisturbed sites (Reeves et al. 1979; Allen and Allen 1980; Loree and Williams 1984). Ectomycorrhiza formation is sometimes reduced in soils of clearcuts, particularly where logging slash has been burned (Wright and Tarrant 1958; Harvey et al. 1980, 1983; Perry et al. 1982; Parke et al. 1984; Perry and Rose 1983). Reduction can persist for years. In the most extensive study to date, in which Douglas-fir and ponderosa pine seedlings were grown in soils from 10- to 20-year-old poorly reforested clearcuts in the Klamath Mountains of California and Oregon, fewer mycorrhizae formed on seedlings grown in soil from clearcuts than in forest soils, and reductions were greatest in soils from slash-burned areas (Parke et al. 1984).
Ectomycorrhiza formation is not always reduced by clearcutting. It may be enhanced and impacts may vary by tree species. The number of mycorrhizae on
Douglas-fir seedlings did not differ in 1-year-old burned and unburned clearcuts and

adjacent forest soils in the Oregon Cascade Moutains (Pilz and Perry 1984). In another study in the Oregon Cascades, Douglas-fir seedlings formed significantly more mycorrhiza in soil from an unburned clearcut than in forest soil, although clearcutting and burning reduced mycorrhiza formation on western hemlock growing in the same soil
(Schoenberger and Perry 1982).
Recovery of ecosystems after disturbance includes resestablishing the energy source for below-ground organisms and processes thus stablizing the soil ecosystem before key elements are lost (Perry et. al., in press, Amaranthus and Perry, in press).
Little is known how rapidly the makeup of the soil community changes following the removal of trees but it is likely mycorrhizaJ inoculation potential of sites declines rapidly in the absence of living hosts (Perry and Rose, 1983; Parke et al. 1984). Loss of mycorrhizal fungi and other rhizosphere organisms will probably have the greatest negative impact on droughty or otherwise stressful sites where seedling survival depends on rapid exploitation of soil (Perry et al. 1987). In some habitats, the timing of mycorrhiza formation may be critical to seedling establishment. The rate of mycorrhiza formation on outplanted seedings is likely to be at least as important as the numbers on harsh sites where the window for seedling establishment is
Rapid establishment of hosts preserves fungal populations on disturbed sites and assists them to build to predisturbance levels. In southwest Oregon and northern California, species in the families Ericaceae, Fagaceae, Pinaceae, Pyrolaceae, Rosaceae, and
Betulaceae form ectomycorrhizae and share at least some fungal species (Largent et al.
1980; Molina and Trappe 1982). Ericaceous manzanitas (Arctostap halos spp.) and
Pacific machone (Arbutus menziesii Pursh) are early pioneers after disturbance such as clearcutting and fire and regenerating conifer seedlings often associate with them
(Amaranthus and Perry, in press). Regenerating seedlings may "plug into" the network of compatible mycorrhzal hyphae supported by the surrounding ericoids, thereby gaining the opportunity for early mycorrhiza formation.
2

3
Seedling survival has been enhanced by mycorrhizal inoculation or, particularly, by soil inoculation in mountainous areas (Mikola, 1973, Valdes 1986). In the Himalayan foothills of northeast India, inoculation with soils from established forests enhanced rehabilitation of sites degraded by intensified shifting agriculture (Sharma 1983). Inoculation with soils may have the potential to enhance mycorrhiza formation and seedling performance on other degraded sites as well. Soil adds a diversity of organisms, including not only mycorrhizal fungi but bacteria, actinomycetes, and perhaps pathogenic fungi
(Marx 1980). The type and abundance of these organisms likely varies by source of soil inocula.
Important questions emerge from the studies cited here. Why is mycorrhiza formation reduced in some cases and not others? Does the abundance and rapidity of mycorrhiza formation affect seedling growth and survival? What factors influence abundance and rapidity of mycorrhiza formation on disturbed sites? What techniques can be used to enhance mycorrhiza formation, seedling survival and growth on disturbed sites?
These studies were undertaken to examine (a) whether reduced mycorrhiza formation influenced growth and survival of outplanted seedlings (Chapter I), (b) whether growth, survivial and mycorrhiza formation differed among Douglas-fir seedlings planted in differing community types (Chapter II), (c)whether soil inoculation could enhance mycorrhiza formation and conifer seedling performance over a range of sources of transfer soils and environmental conditions (Chapter III), and (d) the influence of soil transfer on the rate of root-tip and mycorrhiza formation by planted seedlings (Chapter
IV).

CHAPTER I
MICHAEL P. AMARANTHUS AND DAVID A. PERRY
Department f iorest Science. Oregon State University.
Corvallis., OR, U.S.A. 97331,
ABSTRACT
Numerous studies have shown that seedlings grown in clearcut soils may form fewer mycorrhizae than those grown in forest soil, but it is unclear how, or if, this affects seedling performance. In this study, different levels of mycorrhizae were induced by growing seedlings in soils from either (a) a poorly restocked clearcut in southwest
Oregon, or (b) forest adjacent to the clearcut. Previous work had shown reduced mycorrhiza formation in the clearcut soils. After 12 months in the greenhouse, seedlings were outplanted to the clearcut. At the time of outplanting, only 4% of root tips were mycorrhizal on seedling grown in clearcut soils, while 42% were mycorrhizal on seedlings grown in forest soils. Seedlings from the two soils, however, did not differ in either diameter or height. Differences in numbers of mycorrhizae had disappeared after one growing season in the field, probably because seedlings were colonized by ectomycorrhizal fungi supported by nearby hardwoods. Nevertheless, there were significant growth differences following outplanting. Seedlings greenhouse-grown in clearcut soil averaged nearly 44% less basal area growth and 14% less height growth than those greenhousegrown in forest soil. Survival did not differ. Results suggest that, in the droughty environment of this study, planting seedlings with well-developed myconthizae and protecting native populations of mycorrhizal fungi are likely to aid reforestation.
4

In western North America, various studies have found that seedlings grown in clearcut soils form fewer mycorrhizae than those grown in forest soils (Wright and
Tarrant 1958; Harvey et al. 1980; Perry et al. 1982; Perry and Rose 1983; Parke et al.
1984), although this is not always the case (Schoenberger and Perry 1982, Pilz and Perry
1984). Parke et al. studied mycorrhiza formation by Douglas-fir (Pseudotsuga menziesii
(Mirb.) Franco) and ponderosa pine (Pinus ponderosa Dougi. ex Laws.) seedlings grown in soils from 36 "difficult to regenerate" clearcuts in northern California and southern
Oregon. Compared to seedlings in adjacent forest soils, 40% fewer mycorrhizae formed on seedlings in soils from clearcuts that had been broadcast burned, and 20% fewer in soils from clearcuts with unburned slash.
Ectomycorrhizal trees planted in the tropics often grow poorly and may not survive without their fungal symbiont (Marx 1980), but little is known about how reduced mycorrhiza formation affects growth and survival of outplanted seedlings in temperate zone clearcuts. Amaranthus and Perry (1987) increased first-year seedling growth in two out of three poorly reforested clearcuts in southwest Oregon by adding small amounts of soil from vigorous young plantations to planting holes. In one of the clearcuts, survival increased by nearly 50%. Although improved seedling performance was accompanied by enhanced mycorrhiza formation, transferred soil may have contained other chemical and biotic factors that influenced results.
The study reported herein was conducted on a clearcut with soils previously shown to produce fewer mycorrhizae on seedlings than soils of the adjacent forest (Perry and Rose 1983). Our objective was to determine whether the reduced mycorrhiza formation influenced growth and survival of outplanted seedlings. We induced different levels of mycorrhizae by growing seedlings in a greenhouse, in either clearcut or forest soils, and then outplanted them to the clearcut. Survival, growth, and mycorrhiza formation were measured after one growing season in the field.
5

METHODS
Site description
The study site is located at 500 m elevation in the Kiamath Mountains of southwest Oregon. The site has a western exposure, with a slope averaging 40%. Mean annual precipitation is 260 cm and mean annual temperature 48°F. Less than 5% of the precipitation occurs between June and September, when surface soil temperatures ofover
130°F are common. Soils are clayey-skeletal derived from meta-sedimentary parent materials. Surface soils are thin, gravelly loams, and subsoils are thin to moderately thick, very gravelly clay barns. Soil depths range from 15 to 28 in. Soil nutrient analyses are given in Table 111-2.
The site, which had been clearcut and broadcast-burned 8 years before our study, is dominated by Pacific machone (Arbutus menziesii Pursh), tanoak (Lithocarpus densflorus (Hook. and Am.) Rehd.), canyon live oak (Quercus chrysolepis Liebrn.), white manzanita (Arctostaphylos viscida Parry), and chinkapin (Castanopsis chrysophylla
(Dougi.) A.DC.). There are about 250 Douglas-fir and sugar pine (Pinus lambertiana
Dougl.) seedlings per ha. The adjacent forest, dominated by Douglas-fir and sugar pine, is in the Lithocarpus densz:florus/Gaultherja shallon Pursh/Berberis nervosa Pursh plant association (Atzet and Wheeler 1984).
Field procedure
We collected 25 mineral soil samples (to approximately 15-cm depth) at random locations in the clearcut and another 25 from the adjacent forest. Samples were composited by clearcut or forest and stored at 2°C. Greenhouse planting media were prepared by mixing two parts sieved (1 cm2) field soil (either clearcut or forest) with one part vermiculite and one part peat that had been pasteurized by steaming for 30 mm at 100°C.
Douglas-fir seeds were surface sterilized with 30% 11202 and rinsed with sterile water.
6

7
On February 6, 1985, we planted two seedlings in each of 250 Ray Leach pine cells, half in clearcut soil and half in forest soil. Seedlings, thinned to oneper tube, were grown in a greenhouse for 12 months (14-h minimum daylength, with supplementary lights providing an intensity of 1200 lx). Seedlings were watered three times a week until their third month, then once a week until outplanting, and fertilized twice (4th and 11th month) with
Peters solution.
In March 1986, four blocks within the clearcut were cleared of vegetation. In each block, we planted 25 greenhouse-grown seedlings from each of the two soils
(clearcut or adjacent forest) in a 5 x 5 array at 35-cm spacing. At least 1 m separated seedlings from surrounding vegetation, and seedlings from the two soil types were also separated by 1 m. The same person planted all seedlings in a block. Prior to outplanting, heights and stem diameters were measured on all seedlings, and numbers of root tips and mycorrhizae were recorded on a random sample of 24 seedlings from each soil type.
Survival was recorded, and stem diameters (1 cm above the soil surface) and height were measured on surviving seedlings in October 1986. In November, after fall rains had recharged soil moisture, 12 live seedlings from each soil treatment (3 randomly chosen from each block) were excavated for root examination. Seedlings were placed on ice in the field and then stored at 2°C until examined (within 14 days of excavation). Roots were gently washed and subsampled in two 2-cm transverse sections, one selected randomly from the upper one-half of the root and one from the lower onehalf (Pilz and Perry 1984). Mycorrhiza types were distinguished using a 2X by 5X binocular microscope. Questionable tips were examined for presence of a Hartig net.
Differences in seedling survival, growth, and mycorrhiza formation were tested using Student's t test. We log-transformed tip counts to account for log-normal distribution (Steele and Tome 1980). Percentage survival data were transformed using inverse sine.

RESULTS
Number of myconhizae and seedling size prior to outplanting
After 12 months in the greenhouse, only 4% of root tips were mycorrhizal on seedlings grown in clearcut soil, while 42% were mycorrhizal on those grown in forest soil (Fig. I-i). Total root tips also averaged less on the former, but differences were not significant. Two mycorrhiza types predominated. Type A was 1 to 8 mm long, simple to variously branched, with the Hartig net and mantle well developed. The mantle was brown, tightly interwoven, and 40 to 60 mm thick. Type B was 3 to 20 mm long and rarely branched, and also had a well-developed Hartig net and mantle, the latter white, tightly interwoven with loose outer hyphae, and 3 to 25 mm thick. No type B mycorrhizae formed on seedlings grown in clearcut soil. At the time of planting, seedlings grown in the two soils did not differ significantly in basal area or height (Fig. 1-2).
Growth, survival, and mycorrhiza formation after outplanting
8
Seedlings that were greenhouse-grown in clearcut soil averaged nearly 44% less basal area growth and 14% less height growth during the first field season than seedlings greenhouse-grown in forest soil (Fig. 1-3). Survival was similar for both groups, averaging 62% for seedlings from the clearcut soil and 59% for those from the forest soil. By
November 1986, after 8 months in the field, seedlings initially grown in the two soils no longer differed in either number or type of mycorrhizae. Mycorrhizal colonization averaged 84% for seedlings greenhouse-grown in clearcut soil and 75% for those greenhouse-grown in forest soil (Fig. 1-4).

Numbers of mycorrhizal and nonmycorrhizal root tips before out planting for seedlings grown in soils from clearcut and forest
80
Cl) ci60
I0
0
LL
0
40 w z
0
CLEARCUT FOREST
Numbers of mycorrhizal root tips differed significantly (p<O.O5). Standard errors: forest-type A mycorrhizae=5.5, type B mycorrhizae=1.O, nonmycorrhizal=8.9; for clearcut type A=1.5, type B=O, nonmycorrhizal=9.2
9

1-2.
Basal area and seedling height before outplanting for seedlings grown in soils from clearcut and forest
2.8
E
2.6
<2.4
w
_J
Cl)
2.O
1.8
150
130
110
I
10
50

1-3.
Basal area growth, leader growth, and percentage survival of seedlings greenhouse-grown in soils from clearcut and forest, 7 months after outplanting to the clearcut
E
2.25
11.75
w ci
0.75
C,)
0
0 cr a
I
E
0.25
-
18
16
14
80
60
CLEARCUT FOREST
Basal area growth differs significantly (p <_O.05)
11

1-4.
Mycorrhizal and nonmycorrhizal root tip formation of seedlings greenhouse-grown in soils from clearcut and forest, 8 months after outplanting to the clearcut
I-
0
0
40 z
0
CLEARCUT FOREST
= 10.8, type B mycorrhizae = 2.6, nonmycorrhizal = 3.9; for clearcut--type A = 10.0, type B = 1.7, nonmycorrhizal = 2.3.
12

13
DISCUSSION
Although mycorrhiza formation was the same for seedlings from both soil types by the end of the growing season, differences at the time of outplanting had a clear effect on seedling growth.
On the hot, dry sites characteristic of this area, rapid mycorrhiza formation allows seedlings to exploit soil resources quickly in the spring when they are most available, resulting in rapid early growth. The seedlings are then better able to withstand the summer drought. In 1986, the summer was relatively wet and cool; had it been dry, we might have seen effects on seedling survival as well as on growth.
Seedlings that had formed few mycorrhizae when grown for 12 mo in the greenhouse formed many mycorrhizae when outplanted into the same soils in the field, whereas in the central Cascades of Oregon, mycorrhiza formation of pot-grown seedlings is similar to that of field-grown seedlings (Pilz and Perry 1984). Unlike the Pilz and
Perry sites, our clearcut was colonized by several species of hardwood trees and woody shrubs (tanoak, Pacific madrone, white manzanita, canyon live oak) that are ectomycorrhizal (Largent et al. 1980; Molina and Trappe 1982; S. Borchers and D.A. Perry, unpublished). Read et al. (1985) have shown that hyphae radiating from ectomycorrhizae of one plant will colonize roots of adjacent plants. Work on other southwest Oregon sites suggests that at least some hardwood trees and shrubs are important sources of ectomycorrhizae for conifer seedlings (M.P. Amaranthus and D.A. Perry;
M.P. Amaranthus; S. Borchers and D.A. Perry, all in preparation). Because of low density, conifer seedlings already established on the clearcut were unlikely to be an important source of inocula for newly outplanted seedlings.
Our results show that reduced mycorrhiza formation may affect the performance of outplanted seedlings, particularly on droughty sites where rapid early growth is important. On these sites, planting seedlings with well-developed mycorrhizae and protecting native populations of mycorrhizal fungi are likely to aid reforestation. Why mycorrhiza

formation is reduced in some clearcuts is incompletely understood. Consumption of inocula by burning could be a contributing factor, as could changes in the physical and biotic environment that influence the process of mycorrhiza formation rather than the availability of propagules (Perry et al. 1987). One factor that appears to be important is the presence of ectomycorrhizal host plants. On many sites in southwest Oregon and northern California, nonconmiercial plants may serve as reservoirs of ectomycorrhizal fungal inocula while conifers are becoming established.
14
ACKNOWLEDGEMENTS
We thank Deborah Parrish and Carolyn Choqueue for their assistance. This research was funded by National Science Foundation grant no. BSR-8400403.

Atzet T.A., and D.L. Wheeler 1984. Preliminary plant associations of the Siskiyou Mountain province. U.S. Dep. Agric. For. Serv. Region 6, Portland,
OR.
Harvey, A.E., M.F. Jurgenson, and M.J. Larsen. 1980. Clearcut harvesting and ectomycorrhizae: survival of activity on residual roots and influence on a bordering forest stand in western Montana. Can. J. For. Res. 10:300-303.
Largent
, D.L., N. Sugihara, and C. Wishner. 1980. Occurrence of mycorrhizae on ericaceous and pyrolaceous plants in northern California. Can. J.
Bot. 58:2274-2279.
Marx, D.H. 1980. Ectomycorrhiza fungus inoculations: a tool for improving forestation practices.
Tropical mycorrhiza research. Edited b
P. Mikola. Oxford University Press, Oxford, U.K.
pp. 13-7 1.
Molina, R.J., and J.M. Trappe. 1982. Patterns of ectomycorrhizal host specificity and potential among Pacific Northwest conifers and fungi. For. Sci.
28:423-458.
Parke, J.L. 1982. Factors affecting the inoculum potential of V.A. and ectomycorrhizal fungi in forest soils of southwest Oregon and northern California.
Ph.D. thesis, Oregon State University, Corvallis, OR.
Perry, D.A., M.M. Meyer, D. Egeland, S.L. Rose, and D. Pilz. 1982.
Seedling growth and mycorrhizal formation in clearcut and adjacent undisturbed soils in Montana: a greenhouse bioassay. For. Ecol. Manage. 4:261-273.
Perry, D.A., and S.L. Rose. 1983. Productivity of forest lands as affected by site productivity. j11 Proceedings, Conference on Forest Nutrition. South
Lake Tahoe, CA. Edited R. Powers and T. Robson. U.S. Dep. Agric. For. Serv.
Southwest For. Range Exp. Stn., Berkeley, CA. In press.
15

16
Perry, D.A., R. Molina, and M.P. Amaranthus. 1987. Mycorrhizae, mycorrhizospheres, and reforestation: current knowledge and research needs. Can. J.
For. Res. In press.
Pilz, D., and D.A. Perry. 1984. Management impacts on first year ectomycorrhizal associations of Douglas-fir seedlings: field and greenhouse bioassays. Can. J. For. Res. 14:94-100.
Read, D.J., R. Francis, and R.O. Finley. 1985. Mycorrhizal mycelia and nutrient cycling in plant communities.
Ecological interaction in soil. Edited b
A.H. Fitter. Blackwell Scientific Publications, Oxford, U.K. pp. 193-2 17.
Schoenberger, M.M., and D.A. Perry. 1982. The effect of soil disturbance on growth and ectomycorrhizae of Douglas-fir and western hemlock seedlings: a greenhouse bioassay. Can. J. For. Res. 12:343-353.
Steel, R.G.D., and J.H. Torrie. 1980. Principles and procedures of statistics. McGraw-Hill, New York, NY.
Wright, E., and R.F. Tarrant. 1958. Occurrence of mycorrhizae after logging and slash burning in the Douglas-fir forest type. U.S. Dep. Agric. For. Serv.
Res. Pap. PNW-160.

17
CHAPTER II
SOIL INOCULA ON SURVIVAL, GROWTH, AND MYCORRHIZA FORMA-
TION OF DOUGLAS-FIR1
MICHAEL P. AMARANTHUS AND DAVID A. PERRY
Department Forest Science.
Oregon State University Corvallis. Oregon 97331
ABSTRACT
Douglas-fir seedlings were planted in cleared blocks within three adjacent vegetation typeswhiteleaf manzanita, annual grass meadow, and an open stand of Oregon white oakin southwest Oregon. Within subplots in each block, either pasteurized or unpasteurized soil from a nearby Pacific madrone stand was transferred to the planting holes of the seedlings; control seedlings received no machone soil. Second-year survival averaged 92%, 43%, and 12% for seedlings planted on the manzanita, meadow, and oak sites, respectively. Growth differences generally paralleled survival differences. Added machone soil, whether pasteurized or unpasteurized, did not influence survival, but growth of seedlings on the manzanita site was substantially increased by the addition of unpasteurized machone soil. Unpasteurized machone soil did not influence growth of seedlings in the meadow and the oak stand. Pasteurized machone soil did not affect growth in any of the vegetation types. When added to the manzanita site, unpasteurized machone soil'nearly tripled the number of mycorrhizal root tips forming on seedlings and resulted in formation of a new mycorrhiza type not seen otherwise. As with growth, unpasteurized machone soil had little or no effect in the other vegetation types. These

results suggest that manzanita and madrone impose on soils a biological pattern that stimulates Douglas-fir growth and survival, and they add to the growing body of literature showing that root symbionts and rhizosphere organisms mediate interactions among plant species.
18

19
Numerous researchers have suggested that mycorrhizal fungimutualists with roughly 90% of plant speciesplay key mediative and integrative roles in plant communities (Bowen 1980; Janos 1980, 1983; Malloch et al. 1980; Pirozynski 1981; St. John and Coleman 1983; Harley and Smith 1983; Brownlee et al. 1983; Read et al. 1985;
Perry et al. 1987). Mycorrhizal fungi may allow trees to compete successfully with grasses and herbs for resources (Bowen 1980) and perhaps detoxify allelochemicals produced by those competitors (Perry and Choqueue 1987). The results of pot tests suggest that mycorrhizae can decrease competition between plant species (Perry et al. in press) and increase the productivity of species mixtures, especially in soils where available phosphorus is limited (Puga 1985). Mycorrhizal hyphae can connect plants of different species and facilitate the transfer of carbon and nutrients (Bjorkman 1960; Reid and Woods 1969; Heap and Newman 1980; Francis and Read 1984; Finlay and Read
1986a,b; Chiarello et al. 1982; Francis et al. 1986). However, the existence and implications of these and other integrative roles of mycorrhizal fungi remain largely unexplored outside the laboratory.
In southwest Oregon and northern California, species in the families Ericaceae,
Fagaceae, Pinaceae, Pyrolaceae, Rosaceae, and Betulaceae form ectomycorrhizae and share at least some fungal species (Largent et al. 1980; Molina and Trappe 1982). Encaceous manzanitas (Arctostaphylos sp.) and Pacific madrone (Arbuz'us menziesii Pursh) are early pioneers after fire, and regenerating conifer seedlings often associate with them.
In the hot, droughty environments that are common in this area, conifer seedlings establishing beneath the cover of other vegetation can benefit from the shade. More importandy, however, seedlings may "plug into" the network of compatible mycorrhizal hyphae supported by the surrounding ericoids, thereby gaining the opportunity for early mycorrhiza formation. In some habitats, the timing of mycorrhiza formation is critical to seedling survival (Chapter III; Perry et al. 1987). On the other hand, conifers in this area

20 regenerate poorly beneath Oregon white oak (Quercus garryana Dougl. ex Hook.) (Atzet and Wheeler 1984), apparently benefiting neither from its shade nor from its ectomycorrhizae.
The objective of this study was to determine whether growth, survival, and mycorrhiza formation differed (a) among Douglas-fir (Pseudotsuga menziesii [Mirb.]
Franco) seedlings planted in cleared areas within three adjacent but different vegetative communities, and (b) between seedlings within each community that were planted with or without small amounts of soil from a nearby madrone stand. We hypothesized that conifers would form the greatest numbers of mycorrhizae, and would grow and survive best on soils previously occupied by manzanita; and that machone soil, acting as mycorrhizal inoculum, would improve conifer seedling performance in the meadow and oak stand.

21
METHODS
Site Description
The study site is in a small valley at 385 m elevation in the Siskiyou Mountains of southwest Oregon. Annual precipitation averages 65 cm, less than 10% of which falls from mid-May through mid-September. Soils are fine loamy, mixed mesic Ultic Haploxeralfs, 60 to 100 cm deep, formed in granitic colluvium and underlain by weathered granitic bedrock. Three distinct vegetation types occur within the valley: annual grass meadow (an old homestead), oak savannah, and a conifer-ericoid community. In the last, a fire in 1938 created a mosaic of differing ages and mixtures of Douglas-fir, ponderosa pine (Pinus ponderosa Dougl. ex Loud.), whiteleaf manzanita (Arctostaphylos viscida
Pany), and Pacific madrone.
Our study area was on a southwest-facing, gentle (<10%) toe slope just above the valley bottom, and it included portions of the meadow, the oak stand, and a dense, virtually pure stand of whiteleaf manzanita. The meadow was stocked primarily with hedgehog dogtail (Cynosursas echinatus L.), catchweed bedstraw (Galium aparine L.), roughstalk bluegrass (Poa trivialis L.), and Anthricus sp. Tree height in the open oak stand averaged 10 to 12 m, and the sparse understoiy consisted of various grasses and herbs.
Soils in all three vegetation types are classified in the Holland series (Soil Conservation Service 1979). Surface layers (to 18 cm) are dark greyish brown to brown sandy barns. Percentages of sand, silt, and clay, respectively, were 52, 24, 24 in the manzanita stand; 54, 24, 22 in the meadow; and 40, 31, 29 in the oak stand.
Field Procedure
One-year-old, nonmycorrhizal Douglas-fir seedlings were planted in spring 1985 when soil moisture was at field capacity on each site (vegetation type). No more than
3 days before planting, five blocks were prepared within each site. Manzanita were

22 felled with a chainsaw, oaks were left standing, and low vegetation and surface organic layers were removed with hoes in all blocks. Three plots were planted 1 m apart within each block, each plot consisting of nine seedlings at 40-cm spacing in a 3X3 array.
Seedling diameter 1 cm above the soil surface was recorded at the time of planting.
Seedlings within each plot received one of three soil-transfer treatments when planted: UM (unpasteurized machone soil), PM (pasteurized machone soil), or NT (no soil transfer). Soil for the UM and PM treatments was collected in the Pacific machone stand from the feeder-root zones of 12 trees that had no conifers nearby. PM soil was pasteurized with steam at 70°C for 3 hours and kept in a sealed container until planting.
Treatment consisted of transferring 100 to 120 ml of machone soil into the excavated planting holes of the Douglas-fir seedlings within 24 hours of soil collection.
Seedling survival was monitored at 4-week intervals throughout the study period.
Stem diameter (again at 1 cm height) and leader growth were measured for all surviving seedlings at the end of the first and second growing seasons. Tn November 1985, after fall rains and soil-moisture recharge, 45 live seedlings on each site were excavated, placed on ice, and transported to the laboratory, where they were stored at 2°C for no more than 14 days before root examination.
To monitor soil water content, soil samples to 35 cm depth were collected from all sites at 2- to 3-week intervals throughout the first growing season. Samples were packed in airtight containers and taken to the laboratory, where they were weighed, ovendried for 24 hours at 105°C, and then reweighed.
Percentage of the day's potential solar radiation received was measured with a
Solar Pathfinder (Amaranthus 1984) at the center of each block and calculated for each month during the monitoring period.
In June 1986, four soil samples to 15 cm depth were collected at random spacing along each of three transects in each of the three vegetation types where seedlings were planted and in the Pacific machone stand from which transfer soils were collected (12

23 samples per site). All samples were analyzed for pH (50:50, soil:distilled H20), total N and P (Kjeldahl digest with ammonia and orthophosphate read on an autoanalyzer), and extractable K, Ca, and Mg.
Analysis
Soil and extraneous material were gently washed from roots, and roots were subsampled from three
1.5
cm-thick cross-sections (upper, middle, and lower positions) of the entire root system. All active root tips in each section were tallied and identified as mycorrhizal or nonmycorrhizal, and many cross-sections were examined for the presence of a Hartig net to aid in determination of ectomycorrhizal root colonization.
Mycorrhizal tips were separated by type according to characteristics observable through a binocular microscope (2x to 5x magnification). Information gathered for each ectomycorrhiza type included color, surface appearance, branching, morphology, degree of swelling, length, and characteristics of rhizomorphs. Two mycorrhiza types were dominant on each site on the first-year outplanted seedlings. Types that occurred less frequently were grouped into a "minor" category. Where short roots were colonized by more than one fungal type, the type nearest the root apex was tallied as the mycorrhiza.
Data were subjected to analysis of variance. Before analysis, root-tip counts
(mycorrhizal and nonmycorrhizal) were log-transformed to compensate for lognormally distributed values (Steel and Tome 1980), percentage survival data were converted to an inverse sine, and stem-diameter measurements were transformed to basal area. Differences in seedling survival, height, basal area, and mycorrhizal colonization were examined with Tukey's multiple range test.

24
RESULTS
Soil pH did not differ significantly among sites (including the machone stand from which soil was transferred), nor did nutrients except for potassium, which was higher in oak and machone than in manzanita soils (Fig. 11-1). Soil moisture content (based on ovendiy weight) was also similar among sites throughout the growing season, although the higher clay content in oak soils apparently held slightly more moisture than did soils on the other two sites (Fig.II- 2). Beginning about May 17, all sites exhibited a rapid reduction in available soil moisture, and by July 1 soil moisture was below 15% on all sites. Some replenishment was evident by the end of September. Solar radiation was somewhat lower under the shade of the oaks, averaging 74.8% of mean total potential; solar radiation on the manzanita and meadow sites averaged 89.6% and 8 8.4%, respectively.
First-year survival on plots receiving no soil transfer (NT) averaged 100%, 72%, and 73% on the manzanita, meadow, and oak sites, respectively (Fig. II-3A). By the end of the second growing season, survival had chopped to 42% in the meadow and 12% in the oak stand but remained high (92%) in the manzanita (Fig. II-3B). Soil transfer from the machone stand did not significantly influence seedling survival in any community type.
At the end of the first year, basal-area increment of NT seedlings on the manzanita site averaged more than twice that of NT seedlings in the meadow and four times that of NT seedlings under the oaks (Fig. 4A), a pattern that continued in the second year
(Fig. II-4B). By the second year, height growth (which was not affected by any treatment in the first year) for NT seedlings was also greatest on the manzanita site (Fig. II-
5). On an area basis (roughly calculated as two-year basal-area growth of the average NT seedling times the number of NT survivors), Douglas-fir in the NT treatment grew 0.017,
0.004, and 0.0006 m2/m2 on the manzanita, meadow, and oak sites, respectively.

TI-i.
Soil nutrients and pH for the four study sites. Seedlings were planted on the manzanita, meadow, and oak sites; soil was transferred from the madrone site
0.12
0.10
0.08
0.06
0.04
0.02
0
(A)N
260
(E)K
240
220
200
'
E
160
140
0
10
1
0
8-
0) o 6-
(D) Mg
E
2
6.2
0)
86.1
6.0
E
0
6.5
6.4
6.3
(F) pH
5.8
5.7
0
=SE
0
0"_
4
.
0'
25

11-2 Soil moisture during the 1985 growing season (year 1) on the manzanita, meadow, and oak sites
26
30 w
:,-
F-F 20-
Ow z
00
Cl)
0
APRI MAY1 JUNE 1 JULY 1
1985
AUG 1 SEPT 1 OCT 1

11-3 Percent of seedlings surviving in years 1 and 2, by vegetation type and, within each type, by soil transfer treatment
100
A YEAR 1
40
0
?
100
> cr
B YEAR 2
U NO SOIL TRANSFER
E: UNPASTEURIZED MADRONE
O PASTEURIZED MADRONE
=SE
27

11-4 Average basal-area growth per seedling in years 1 and 2, by vegetation type and, within each type, by soil transfer treatment
12
A YEAR 1
8 c'J
E
E
0)
0
0
w
'ci)
0
I a)
0
60
BYEAR2
40
Ct
20
N NO SOIL TRANSFER
UNPASTEURIZED MADRONE
0 PASTEURIZED MADRONE
=SE
10
OAK
28

11-5 Average seedling height growth in years 1 and 2, by vegetation type and, within each type, by soil transfer treatment
80
1 60
40
0
B YEAR 2
200
1 80
NO SOIL TRANSFER
UNPASTEURIZED MADRONE
O PASTEURIZED MADRONE
=SE
1 00
80
MANZANITA MEADOW OAK
29

30
Machone soil transfer did not affect seedling growth in the meadow or the oak stand. On the manzanita site, however, second-year basal-area growth of UM seedlings was nearly twice that of either PM or NT seedlings (Fig. II-4B), and second-year height growth of UM seedlings was 40% greater (Fig. II-5B). During the second growing season, UM seedlings in manzanita averaged roughly four times more basal-area growth per seedling than those in meadow and eight times more than those under oaks. On an area basis (calculated as above), UM seedlings grew 0.034 m2/m2 net basal area over two years on the manzanita site and only 0.004 and 0.0004 m2/m2 on the meadow and oak sites, respectively. Height growth also differed significantly, though less dramatically
(Fig.11-5B).
Seedlings on the manzanita and meadow sites formed equal numbers of myconhizae; those on the oak site formed fewer (Fig 11-6). However, mycorrhiza types differed between manzanita on the one hand and meadow and oak on the other. Type "A" (whose color, structure, and rhizomorph development suggested that it was Rhizopogon vinicolor rdominated on seedlings from the manzanita site, whereas type "B" (tentatively identified as Pisolithus tinctorius) dominated on the meadow and oak sites. Fruiting bodies of
Pisolithus tinctorius were observed in the meadow, probably originating from mycorrhizae on bordering trees or shrubs.
On the manzanita site, unpasteurized machone soil greatly enhanced total mycorrhiza formation. This resulted from the greater abundance of R. vinicolor, and also from the appearance of an unidentified yellow mycorrhiza which we designated type "C" (Fig.
11-6). Although small numbers of type "C" formed on UM seedlings in the meadow, overall mycorrhiza formation on those seedlings was not enhanced. UM and PM seedlings on the oak site, though they formed no type "C" mycorrhizae, formed a greater proportion of R. vinicolor.

11-6 Average seedling mycorrhiza formation at the end of the 1985 growing season
(year 1) by vegetative type and within each type by soil transfer treatment.
31
240
220 -
200 -
180 -
160
140 -
120
100 -
80 -
60 -
40 -
20 -
0 o
MYCORRHIZA TYPE A
MYCORRHZA TYPE B
MYCORRHIZA TYPE C
NTUM PM NT UMPM NT UMPM
MANZANITA MEADOW OAK
Within a given vegetation type, lowercase letters indicate statistically significant differences (p <0.05) from the NT treatment: a) for total root tips, b) for type A mycorrhizae, c) for type C mycorrhizae.
Type B mycorrhizae differed significantly among vegetation types but were not influenced by soil transfers.

32
DISCUSSION
Douglas-fir seedlings, when planted in soils previously occupied by whiteleaf manzanita, grew and survived better than seedlings planted either in an adjacent, cleared meadow or beneath open stands of Oregon white oak that were cleared of surface vegetation. Small amounts of unpasteurized soil from a nearby Pacific machone stand improved seedling growth on the manzanita site, but not on the other sites. Taking into account both mortality and basal area growth of surviving individuals over the two years,
Douglas-fir inoculated with unpasteurized machone soil occupied space within the manzanita site at a rate roughly 10 times greater than in the meadow and 100 times greater than under the oaks.
We detected no differences in soil physical structure, water content, or macronutrients that could explain these results. In this droughty environment, the moderate shade of the oaks should benefit rather than inhibit seedlings. Undetected variation in micronutrients or other inherent site factors cannot be ruled out.
The differing proportions of mycorrhiza types among treatments strongly suggest that the influence of manzanita is biological. However, numerous abiotic factors can affect the types of mycorrhizae that form on seedlings (Schoenberger and Perry 1982;
Pilz and Perry 1984). The effect of machone soil transferred to seedlings on the manzanita site was almost certainly biological; it induced a new mycorriza type, and pasteurization rendered it ineffective. Increased formation of Rhizopogon mycorrhizae and appearance of the new mycorrhiza type on seedlings with added machone soil could result either from direct transfer of mycorrhizal inocula in machone soils or from stimulation of mycorrhiza formation by bacteria or actinomycetes in machone soil. Several studies have shown that rhizosphere bacteria influence mycorrhiza formation (Shemakhanova 1967;
Bowen and Theodorou 1979; Perry and Rose 1983; Meyer and Linderman 1986; Garbaye and Bowen 1987). Elsewhere we report that rhizosphere nitrogenase activity was signifi-

33 cantly greater for seedlings on the manzanita site than for those in the meadow (seedlings planted in the oak stand were not tested). That effect was greatly enhanced by addition of machone soil and is related to the presence of Azospirillum sp. on or within mycorrhizae
(Amaranthus et al. 1987).
On the other hand, relative ineffectiveness of machone inocula on the meadow and oak sites indicates that more is involved in Douglas-fir response than simple presence or absence of the "right" organisms. Theodorou and Bowen (1971) showed that grasses inhibited mycorrhiza formation by Rhizopogon luteolus Fr. Nordh. on racliata pine (Pinus radiata D. Don), and suggested that this was due to lower soil P in the presence of grass.
Stimulation of Rhizopogon formation in oak soils by both pasteurized and unpasteurized machone soil may indicate nutrient limitation, although we detected no difference in macronutrients between any of the soils. Some organisms, particularly actinomycetes and other spore-forming bacteria, survive pasteurization (Shemakhanova 1967;
R. Linderman, personal communication) and might influence mycorrhiza formation
(Shemakhanova 1967; Perry and Rose 1983).
Our work in clearcuts of this area supports the findings of this study. In the field, the rate of Douglas-fir root tip formation correlates positively with proximity to manzanita (Amaranthus and Perry in review). In the greenhouse, small amounts of soil (100 ml) taken from the vicinity of the ectomycorrhizal hardwoods machone, tanoak (Lithocarpus dens jflorus [Hook. & Am.] Rehd.), and canyon live oak (Quercus chrysolepsis
Liebm.) stimulate growth of Douglas-fir (Borchers and Peny 1987). As in this study, increased growth is accompanied by a higher proportion of Rhizopogon mycorrhizae.
A wide variety of nonconiferous plant species may support conifer mycorrhizal fungi (Molina and Trappe 1982). In southwest Oregon and northern California, plants in six families are ectomycorrhizal. This does not mean that all of them harbor rhizosphere organisms that stimulate conifer growth, as demonstrated by our results with seedlings planted in Oregon white oak stands. However, of five broadleafed ectomycorrhizal plant

34 species tested in this study and by Borchers and Perry (1987), soils collected from the
Douglas-fir growth. This phenomenon may extend to plant species that are not usually thought of as ectomycorrhizal. In Australia, ectomycorrhizal fungi have been shown to colonize the roots of various "nonectomycorrhizal" plant species (Theodorou and Bowen
1971; Kope and Warcup 1986). Theodorou and Bowen (1971) suggest that this facilitates survival and spread of ectomycorrhizal fungi. In greenhouse bioas says of soil from the Oregon Cascades, the number of Rhizopogon vinicolor mycorrhizae formed by
Douglas-fir seedlings correlates positively with the cover of VA mycorrhizal vine maple
(Acer circinatwn Pursh) and snowbrush (Ceanothus velutinus Dougi.) on plots where soils were collected (R. Brainerd and D. Perry, unpublished). This could be a nutrient effect, as soil nitrogen and phosphorus concentrations also correlate positively with cover of these species.
Foresters frequently view noncrop plant species as undesirable competitors for light, water, and nutrients, and there is little doubt that such competition occurs. However, our results and those of others indicate that plant species may interact positively as well as negatively (Hunter and Aarsen 1988). Better understanding of ecological relationships within early successional communities may have much to offer forestry.
ACKNOWLEDGEMENTS
Research was funded by National Science Foundation grant number BSR-
8400403. We thank Jim Trappe, Randy Molina, Mike Castellano, Jummane Maghembe,
Jacob Freidman, and Peter Vitousek for helpful suggestions and critical review of an earlier version. Special thanks to Deborah Parrish for considerable assistance in field and laboratory analysis.

35
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37

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39

40
CHAPTER ifi
THE SURVIVAL AND GROWTH OF CONIFER SEEDLINGS ON OLD, NON-
MICHAEL P AMARANTHUS & DAVID A. PERRY
Department f Forest Science% Oregon State
University Corvallis. Q, 97331. USA
ABSTRACT
Small amounts (l5OmL) of soil from established conifer plantations and mature forest were transferred to planting holes on three clearcuts on southwest Oregon and northern California to enhance mycorrhiza formation. The clearcuts, 8-27 years old and unsucessfully reforested included a range of environmental conditions. At Cedar Camp, a high elevation (1720m) southerly slope with sandy soils, transfer of plantation soils increased 1st-year Douglas-fir (Pseudotsuga menziesii (Mirb.) Francó) seedling survival
50%. Notably, soil from a plantation on a previously-burned clearcut doubled mycorrhiza formation and tripled seedling basal area growth. Soil from mature forest did not improve growth and survival. Less dramatic effects owing to soil transfer were evident on the other sites, which were lower in elevation and had clayey soils with greater water holding capacity, and where woody shrubs had apparently preserved mycorrhizal fungi.
At Crazy Peak (1005m), seedling survival was uniformly good, and soil from a previously burned plantation increased Douglas-fir mycorrhiza formation. At Wood Creek
(500m), soil from a plantation on a previously unburned clearcut increased mycorrhizal branching on sugar pine (Pinus lambertiana Dougl.) seedlings, but there were no other effects. Results suggest that adequate mycorrhiza formation is critical to seedling growth and survival on cold, droughty sites. Populations of mycorrhizal fungi, and perhaps other

beneficial soil biota decline if reforestation is delayed or other host plants are absent.
These declines can be offset by soil transfer from the proper source; in this study, soil from vigorous young plantations.
41

42
Most forest tree species of the Pacific Northwest are ectomycorrhizal (Molina and
Trappe 1982a). Benefits to the host plants include increased water and nutrient uptake, resistance to root pathogens, and increased tolerance to environmental extremes (Marx and Krupa 1978). Formation of ectomycorrhizae depends on a source of inocula but is also influenced by environmental variables and soil properties such as soil moisture, temperature, pH, fertility and organic matter (Slankis 1974). Harvest and site preparation alter these factors and therefore potentially impact microbial numbers and diversity.
Reduced mycorrhiza formation on seedlings in clearcut soils (especially where slash has been burned) has been reported by numerous researchers (Wright and Tarrant 1958;
Harvey et al.1980; Perry et at 1982; Parke et al. 1984). Moreover, harvest-related changes in forest floor and soil (Amaranthus and McNabb 1984) may affect not only ectomycorrhizae but other soil microorganisms with which they interact (Perry and Rose,
1983)
Little is known of the persistance and distribution of ectomycorrhizae in the absence of living hosts. It has been suggested (Hacskaylo 1973) that ectomycorrhizal fungi do not persist long in the absence of host-supplied substrates. Total elimination of active ectomycorrhizae was reported 1 year after clearcutting a high-elevation site in western Montana (Harvey et. al. 1980). Ectomycorrhizae from an adjacent undisturbed stand did not occur beyond 4.5 m into the clearcut and numbers of ectomycorrhizae were reduced 7.5 m into the adjacent stand. Recolonization of this clearcut would depend on external inoculum (Maser et al. 1978).
Myconhiza formation may be of primary importance in water uptake and drought resisitance (Reid 1979: Parke et al. 1983a), and early mycorrhiza formation is particularly important to seedling growth and survival in dry areas (Mikola 1970). However, drier climates may limit the activity of mycorrhizal fungi as well as decrease the time in which conditions for spore germination and mycelial growth are optimal, thus decreasing the

43 chances for planted seedlings to be colonized. In contrast, seedlings in wetter climates are exposed to available moisture for a longer period and can thus survive longer without mycorrrhizae and increase their probability of eventually becoming colonized.
Because relatively small amounts of inocula are adequate for effectively colonizing seedlings (Pilz and Perry 1984), reduced ectomycorrhiza formation owing to disturbance might be offset by transferring soil from the feeder-root zones of actively growing, compatible host species to impacted sites. In our study, we transferred soil from the feeder root zones of burned and unburned plantations, as well as pasteurized and unpasteurized soil from adjacent undisturbed mature forest, into planting holes on three old clearcut and burned sites that had not been sucessfully reforested. The study was designed to (1) investigate mycorrhiza formation and conifer seedling performance after soil transfer, (2) examine a range of sources of transferred soil to determine the most effective, and (3) assess the environmental conditions under which soil transfer contributes to seedling growth and survival.

44
METHODS
Site characteristics
Three sites representing a range of elevations, soils and vegetation (Table 111-1) were selected in the Klamath Mountain region of northern California and southern Oregon. The Kiamath Mountains are characterized by rugged, steeply dissected terrain with shallow, skeletal soils. The forests are typically mixed evergreen. Summers are hot and dry, winters are wet.
Sites had been clearcut and broadcast burned between 8 and 27 years before study installation. Cedar Camp (site 1) and Crazy Peak (site 2) have a history of reforestation failure and are poorly stocked despite repeated planting with conifers. Conifer regeneration at Wood Creek (site 3) has been more successful than that on the other two sites; however, large unstocked areas are common within the clearcut. Previous work at Cedar
Camp and Wood Creek had shown reduced ectomycorrhiza formation relative to that in the adjacent, undisturbed forest (Perry and Rose, 1983).
Soil transfer
At each site, five replicate blocks (3x3 m) were cleared of preexisting vegetation with chainsaws and hoes 1 week before soil treatment and seedling planting in spring
1985. Seedlings to be planted were nonmycorrhizal 1-0 Douglas-fir and 1-0 sugar pine stock grown in Ray Leach fir cells at Dean Creek Nursery, Oregon.
Each seedling was placed in a planting hole to which l5OmL of soil was simultaneously added from one of four soil-transfer treatments: soil from a Douglas-fir plantation established on a previously burned clearcut (BC), soil from a plantation established on an unburned clearcut (UC), unpasteurized soil from undisturbed mature forest (MF), or pasteurized soil from undisturbed mature forest (PMF). The fifth treatment, no soil transfer (NT), was the control. Plantations, ranging from 10 to 15 years of age, were on the same soil type and at similar elevations as the study sites.

Table UI-i.
Site characteristics of the three clear-cut and broadcast-burned study sites (Kiamath Mountain region, southern
Oregon. and northern California)
Characteristic
Cedar Camp
(site 1)
Crazy Peak
(site 2)
Wood Creek
(site 3)
Age after clear-cut (years)
Elevation, aspect, slope
Precipitation and air temperature
Soil
Classification
16
1720 s. SW. 5O
0
165 cm (5O is snow). 5 C
27
1005 m.
S.
15
230 cm 5O
0 is snow. 7 C
8
500 m. W. 4O
0
260 cm (lOs is snow. 9 C
Parent material
0 temperature C). 35-cm depth
(
April 28. 1985
May 28. 1985 a
Plant association
(adjacent, undisturbed forest)
Dominant vegetation
Clear-cut
Sandy skeletal, excessively drained-, mixed Entic
Cryumbrept
Quartz diorite
2.2
4.4
ABCO/ABMAS/SYMO
-
Clayey skeletal. mesic
Ultic Haploxeralf
Serpentinized gabbro
5.6
7.8
L1053/RMCA
Clayey skeletal, mixed sesic
Ultic Haploxeralf
Metasedimentary
7.2
10.6
LIDE3/GASM/BENE
Adjacent, undisturbed forest
Annual grasses, herbs.
bracken fern, red elderberry. greenleaf manzanita
White fir, Douglas-fir,
Shasta red fir
Creenleaf manzanita. pinemat manzanita. coffeeberry.
huckleberry oak. tanoak.
golden chinkapin, ponderosa pine. knobcone pine.
Douglas-fir
Douglas-fir. sugar pine.
white fir, incense cedar
Pacific madrone. tanoak.
canyon live oak, white mansanita. golden chinkapin
Douglas-fir. sugar pine a
ABCO/ABMAS/SYMO, Abies concolor/Abies magnifica var. shastensis/Symphoricarpos mollis: LIDE3/RHCA. Lithocarpus densiflorus/Rhamnus californica: L1053/GASM/BENE. Lithocarpus densiflerus/Gaultheria shallon/Berberis nervosa (From Atzet and
Wheeler 1984).
b
Bracken fern. Pteridium aquilinium CL.) Kuhn.: red elderberr,y. Sambucus racemosa L.: greenleaf isanzanita, Arctostaphylos patula Greene: pinemat manzanita. Arctostaphylos nevadensis Gray: white manzanita. Arctostaphylos viscida Parry: coffeeberry.
Rhamnus californica Esch. var. occidentalis (How.) Jeps.: Douglas-fir. Psedotsuga menziesii (Mirb.) Frartco: white fir. Abies concolor (Gord. & Clend.) Hildebr.: shasta red fir. Abies magnifica war. shastensis Less.: sugar pine. Pinus lambertiana Dougl.l
huckleberry oak. Quercus vaccinifolia Kellogg: canyon live oak.
Quercus chrysolepis Liebs.: Tanoak. Lithocarpus densiflorus
(Hook. & Am.) Rehd.: golden chinkapin, Chrysolepis chrsophylla (Dougi.) DC.: Pacific madrone (Arbutus menziesii Pursh): Ponderosa pine. Pinus ponderosa Laws.: knobcone pine.
pinus attenuata Lemm: incense cedar
(Libocedrus decurrens Torr.).

46
Soil and air temperature, humidity, and wind speed were measured at planting; no seedlings were planted when air temperature exceeded 15.5°C Soil moisture was at field capacity at planting.
Transfer soil, collected within 7 h of planting, was taken form the feeder-root zone (top
20 cm of mineral soil) of 12 randomly selected Douglas-fir trees per plantation for the
BC and UC treatments and one crown width from the base of twelve randomly selected mature conifers (white fir at Cedar Camp, Douglas-fir at Crazy Peak, Douglas-fir and sugar pine at Wood Creek for the MF and PMF treatments. Undisturbed-forest soil used for the PMF treatment was steam heated for 3 h at 70°C, sealed, and returned to the field for transfer within 48 h. Twenty-five seedlings per treatment per block were planted 40 cm apart in a 5x5 array, at least 1 m separating treatments from one another, in a randomized block design. One worker planted all five treatment units in a block.
Basal diameter 1 cm above the soil surface was measured with calipers within 1 week of planting. Seedling survival was monitored at 4-week intervals throughout the study period (one growing season). At the end of the growing season, diameters and leaders were measured on all surviving seedlings Fifty live seedings per site were carefully excavated in November 1985 following fall rains and soil moisture recharge, placed on ice in the field, and transported to the laboratory where they were stored at 2°C Seedling roots were examined for numbers and types of mycorrhizal tips wihin 14 days of excavation.
Soil was gently washed from roots and roots were subsampled in three 1.5-cm.
sections cut across the entire root system in upper, middle and lower positions. All short roots and the number of active root tips per short root were tallied in these sections and tips identified as nonmycorrhizal or mycorrhizal. Throughout, the terms "branching ratio" and "mycorrhizal branching" are used to denote the average number of tips per short root. Numerous root cross sections were examined for the presence of a Hartig net to aid in determining mycorrhizal root colonization. Tips that appeared inactive or dead were not counted.

47
Soil nutrients and moisture
In May 1986, soil was collected from Cedar Camp, Crazy Peak, and Wood Creek and from the plantation and mature-forest sites used as soil-transfer sources. At each site, soil was randomly sampled from four points along each of three transects: samples were composited by four points along each of three transects: samples were composited by transect. Soil samples were analyzed at the Oregon State University Soils Laboratory for
PH; phosphorous (P, molybdate blue method); and total nitrogen (N).
Soil moisture was determined gravimetrically from samples taken at 2- to 3-week intervals throughout the growing season at 10-, 35-, and 60cm depths at Cedar Camp and
Crazy Peak. Samples were packed in airtight containers and transported to the laboratory, where they were weighed, oven-dried for 24 h at 105°C, and reweighed. For each sampling interval and depth, available soil moisture was determined by calculating the difference between the observed and the minimum (peak of the summer drought) moisture content. Precipitation amounts were recorded at 2-to 3-week intervals from rain guages on the two sites. Soil moisture and precipatation were not measured at Wood
Creek.
Statistical analysis
Data were subjected to analyis of variance. Root-tip counts were log transformed to compensate for lognormally distributed values (Steel and Tome 1980). Percentage survival data were transformed to an inverse sine and diameter measurements were converted to basal area. Tukey's mutiple range test was used to compare differences
(pO.O5) among treatment means for seedling basal area growth, survival, mycorrhizal and nonmycorrhizal root tips and branching, and also for soil nutrient and pH levels.

48
RESULTS
Soil transfer
At Cedar Camp, Douglas-fir seedlings receiving BC, UC, and PMF treatments had significantly greater 1 st-year basal area growth, survival, numbers of mycorrhzal root tips, and mycorrhizal branching than seedlings receiving no soil transfer (Fig. 111-1).
Soil from the BC treatment had a particularly striking effect: it doubled the number of mycorrhizal tips, almost tripled basal area growth, and increased survival by 50% (from
42 to 62%) relative to the controls. The MF treatment also increased basal area growth relative to the controls but did not influence the other variables.
Patterns were similar but less definitive at Crazy Peak (Fig. 111-2). BC, UC, and
PMF treatments increased basal area growth by 40-50% relative to controls. Numbers of mycorrhizal tips and degree of mycorrhizal branching averaged higher in all treatments in which soil was transferred than in the controls: however, differences were statistically significant only for BC (mycorrhizal numbers and branching) and PMF (branching).
Survival exceeded 95% in all treatments.
Other than increasing mycorrhizal branching in the UC treatment, soil transfer did not affect seedling performance at Wood Creek (Fig. 111-3). Survival was high (>85%) in all treatments. Lower numbers of mycorrhizae and generally greater mycorrhizal branching on this site relative to the other two probably reflect differences in seedling species
(sugar pine at Wood Creek vs. Douglas-fir at Cedar Camp and Crazy Peak).
Soil nutrients and moisture
Levels of soil macronutrients did not vary significantly among unreforested clearcut (Cedar Camp, Crazy Peak, Wood Creek), plantation (BC, UC), and mature forest
(MF, PMF) soils at each study site, nor did pH (Table 111-2). Levels of N, probably the most limiting nutrient in these soils, were moderate at Cedar Camp but low at the other two sites. P levels were quite low at Crazy Peak.

49
Available soil mositure was greater at Crazy Peak than Cedar Camp, and soils at the former remained moist longer into the growing season (Fig. ffl-4). Both sites experienced 80 days (mid-June to early September) when virtually no rain fell; however, Crazy
Peak still had available soil mositure an additional 2 weeks into this droughty period. In
1985, seedlings at Cedar Camp had approximately 28 days, whereas those at Crazy Peak had approximately 95 days, when soil temperatures exceeded 4°C at the 35-cm depth and when soils had available water.

Ill-i Mean 1st-year basal area growth, survival, number of mycorrhizal root tips, and degree of mycorrhizal branching of Douglas-fir seedlings following soil transfer at Cedar Camp.
A
=SE
50
80
60 -
40 -
20 -
0
C
140
01 120-
a
100-
80-
60-
:.
z
40
D
1.6
ab
BC UC MF
TREATMENT
PMF NT
BC, soil from plantation on a previously broadcast-burned clear-cut: UC, soil from plantation on a previously unburned clear-cut; MF, soil from adjacent mature forest; PMF, pasteurized soil from adjacent mature forest; NT, no soil transfer. Bars with the same lowercase letters are not significantly different (p<0.05), Tukey's multiple range test; SE, standard error.

51
111-2 Mean 1st-year basal area growth, survival, number of mycorrhizal root tips, and degree of mycorrhizal branching of Douglas-fir seedlings following soil transfer at Crazy Peak
I-
I
0
100
B a
40
20
80
60 a a a a
/
/
tX(I) 140
ø:c1 o 120-
-
100-
80
LL
0
60 g
40
3.0-
D
2.8
2.6-
2.4
2.2-
2.0-
1.8-
1.6
BC UC MF
TREATMENT
PMF NT
See site 1 fig. for soil-treatment descriptions. Bars with the same lowercase letters are not significantly different (p 0.05), Tukey's multiple range test; SE, standard error.

111-3 Mean 1 st-year basal area growth, survival, number of mycorrhizal root tips, and degree of myeorrhizal branching of Douglas-fir seedlings following soil transfer at Wood Creek.
C
U
J
I) a a
100
80
-J
60
:, x
40
20
-J
0
C
50-
40
30-
10
52
UC MF
TREATM ENT
PMF NT
See site 1 fig. for soil-treatment descriptions. Bars with the same lowercase letters are not significantly different (p <0.05), Tukey's multiple range test; SE, standard error.

Table 111-2.
Mean pH and nutrient levels (. SE) from various soil sources.
Values did not vary significantly (p< 0.05) among unreforested clear-cut, plantation.
and mature-forest soils.
Soil Source pH
P
(ppm)
Ca
(mequiv./loog)
Mg K
(mequiv./100g) (mequiv./lOOg)
Total N
()
Cedar Camp
Unref ores ted clear-cut tIC
6.05
54
(+0.39) (+14.2)
Transferred soils
MF
BC
5.8
(.0.22)
6.1
(.0.29)
5.9
(.0.19)
38
(+8.2)
28
(.9.6)
32
(.8.9)
Unreforested clear-cut 5.89
(.0.26)
36
(.12.0)
Transferred soils
HF 6.09
BC
UC
(.0.40)
5.93
(.0.18)
5.48
(.0.42
34
(. 6.8)
21
(.6.5)
26
(.3.6)
16.4
(+3.2)
12.0
(+4.3)
12.7
(.2.6)
12.6
(.3.2)
Crazy Peak
Unreforested clear-cut 5.6
(.0.38)
9
(.3.6)
Transferred soils
HF
5.4
(.0.30)
BC 5.9
UC
(.0.16)
5.8
(.0.14)
-
7
(.1.8)
5
(+1.2)
6
(.0.6)
2.6
(.0.46)
,
3.4
(.0.53)
2.9
(.0.81)
3.0
(.0.18)
Wood Creek
2.8
(.0.42)
3.9
(.0.99)
2.7
(.0.43)
1.8
(.0.89)
1.7
(+0.43)
2.1
(.0.27)
1.6
(.0,28)
1.7
(.0.32)
2.1
(.0.40)
2.2
(.0.28)
2.4
(.0.42)
3.4
(.0.83)
0.75
(.0.14)
0.93
(.0.23)
0.84
(.0.29)
0.59
(.0.30)
164
(.23.0)
203
(.27.4)
245
(.38.2)
230
(.16.4)
0.16
(.0.028)
0.19
(.0.042)
0.13
(.0.032)
0.15
(.0.036)
104
(.14.9)
-
0.07
(.0.008)
145
(.42.1)
105
(.16.0)
126
(.38.2)
117
(.22.0)
0.08
(.0.021)
0.07
(.0.014)
0.07
(.0.006)
0.09
(.0.038)
174
(.51.3)
117
(.20.8)
138
(.18.0)
0.11
(.0.012)
0.09
(.0.009)
0.12
(.0.008)
Note:
HF. soil from adjacent mature forest; BC.
soil from plantation on a previously broadcast-burned clear-cut; UC. soil from plantation on a previously unburned clear-cut.
53

111-4 Soil moisture at the 35-cm depth and precipitation at Cedar Camp and
Crazy Peak throughout the 1985 growing season.
54 z
0
0
0
0
CEDAR CAMP
[] CRAZY PEAK t =TRACE
0
5/16 6/4 6/27 7/15 7/31 8/20
DATE
I
U
10/1 10/29

55
DISCUSSION
Soil transfered from well-stocked plantations increased seedling basal area growth and mycorrhza formation on two clearcut sites and increased mycorrhizal branching on a third. In general, soil from plantations on sites that had been broadcast burned produced greater effects than that from plantations on unburned sites. Soil from mature forest adjacent to each of the study clearcuts had relatively little effect, increasing basal area growth on only one site. However, in some cases, pasteurizing adjacent forest soil increased the magnitude of its effect.
At Cedar Camp, soil transferred from both burned and unburned plantations increased 1st -year seedling survival from 40 to 60 %. Although growth of the previous stand on this clearcut, and of the adjacent mature stand, is quite good, seedling establishment is difficult; four previous reforestation attempts have failed. Soils are coarse textured (<3% clay) loamy sands with low water-holding capacity; they remain frozen late into spring because of the high elevation and lose moisture early to summer drought, giving seedlings a very short time in which to become established. Rapid, extensive mycorrhiza formation is perhaps most critical on this site where seedlings must rapidly attain the necessary nutrients and water not only to survive severe summer drought but to come through in sufficiently good condition to also survive a long winter. Observations of another soil-transfer experiment on this site (Chapter 4) show that seedlings growing in transferred plantation soil form root tips at a significantly higher rate in early spring than those growing without transfer soil.
Although soils on the other two sites have higher water-holding capacity than those at Cedar Camp, sunm-ier drought is nevertheless a factor. The importance of early mycorrhiza formation in dry areas has previously been emphasized (Parry 1953; Mikola
1970; Slankis 1974). Rhizopogon mycorrhizae, common mycosymbionts in clearcuts of the Pacific Northwest, have been shown to reduce drought stress of Douglas-fir seedlings

56
(Parke et al. 1983a) Drier climates may limit the activitiy of mycorrhizal fungi as well as decrease the time in which conditions for spore germination and mycelial growth are optimal, thus decreasing the chance that a planted seedling will quickly become colonized (Slankis 1974). Under such conditions, factors that enhance the rapidity of mycorrhiza formation, whether related to density of fungal inocula, ability of seedling roots to quickly explore a large soil volume, or other biotic or physical influences, will probably produce more vigorous seedlings. Both Crazy Peak and Wood Creek clearcuts were occupied by ericaeous shrubs that form mycorrhizae with at least some of the same fungi as conifers (Largent et al.. 1980; Molina and Trappe 1982b); hence, in contrast with
Cedar Camp, viable fungus populations were present despite the absence of conifers.
Even so, growth of seedlings at Crazy Peak benefited from transfers, and this early boost in growth could influence tree growth and vigor well into the future. Lack of response to soil transfer at Wood Creek may have been due to incompatibility of the sugar pine seedlings with the flora of Douglas-fir plantation soil (no sugar pine platations were available in the area).
We cannot now say why soil from well-stocked plantations stimulated mycorrhiza formation and seedling growth. Taken from the feeder-root zone, transferred soil was undoubtedly rich in mycorrhizal inocula; however it also contained components that could have stimulated mycorrhiza formation by fungi indigenous to the clearcuts. Numerous abiotic and biotic soil factors influence mycorrhiza formation ( see reviews by
Bowen 1973;Slankis 1974). Other than direct addition of fungal inocula, the factors most likely to have stimulated mycorrhia formation by our seedlings are as follows: (1) nutrients; (2) organic compounds such as hormones, vitamins, humic compounds, and amino acids, and (3) nonmycorrhizal biota.
Very small amounts of nutrients were added with the transferred soils, e.g., only
0.1-0.2 g of N and even less P, K, Mg, and Ca per planting hole. Moreover, levels of these nutrients in transferred soils did not differ significantly from those in the clearcuts.

57
We cannot be sure that some limiting micronutrient was not included; however, macronutrient fertilization is unlikely to explain differences in seedling survival and growth.
Organic matter and various root exudates have long been known to stimulate, and occasionally inhibit, mycorrhiza formation (Slankis 1974; Alvarez et al. 1979;Schoenberger and Perry 1982; Parke et al. 1983b; Rose et al. 1983). Rhizosphere organisms may either stimulate or inhibit formation of the symbiosis (Slankis 1974; Bowen and
Theodorou 1979; Chakraborty et al. 1985). Clearcutting followed by slash burning (all three of our sites were burned) reduces organic matter and alters the nature of the soil microbial community
, in some cases increasing the proportions of pathogens or other biota that negatively impact seedlings (Widden and Parinson 1985; Perry and Rose 1983)
Soils from the root zone of healthy trees probably have numerous biotic and abiotc components not present in clearcuts, at least some of which are likely to stimulate root tip and mycorrhiza formation.
In our experiment, mycorrhiza formation and seedling growth were generally stimulated by soils from established plantations and, following plasteurization, mature forest. If we assume that the same factor(s) are operative in each case, the effect of pasteurized soil implies inorganic nutrient (s) or organic compound(s) that for some reason were rendered ineffective by soil boita of the mature forests. There is no reason, however, to assume that the same factor(s) were operative. Succession of mycorrhizal fungi is now firmly established (Mason et al. 1983), and it is possible that mycorrhizae transferred in plantation, as opposed to mature forest, soils were more compatible with seedlings in a clearcut environment. Hence mycobiont inocula probably played an important role in seedling response to plantation soil inocula, whereas physical or biochemical properties of pasteurized mature-forest soils could have stimulated seedling mycorrhiza formation.
Although the underlying biology is uncertain, the study results nevertheless provide useful insights into refore sting clearcuts in southwest Oregon and northwest

58
California and, perhaps, on other difficult to reforest sites. Reduced mycorrhiza formation following disturbance can restrict the ability of seedlings to become established, particularly in physically rigorous environments where the period favorable for growth is relatively short. Under such conditions, transfer of soil from the appropriate source (in our case, well-stocked plantations) can dramatically stimulate mycorrhiza formation as well as seedling survival and growth.
ACKNOWLEDGEMENTS
This research was funded by National Science Foundation grant No.BSR-
8400403

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59

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Molina, R., and J.M. Trappe. 1982a. Patterns of ectomycorrhizal host specificity and potential amonst Pacific Northwest Pacific Northwest conifers and fungi. For. Sci.
28:423-457.
Molina, R., and J.M. Trappe. 1982b. Lack of mycorrhizal specificity by the ericaceous hosts Arbutus menziesii and Arctostaphylos uva-ursi. New Phytolo-
90:495-509.
Parke, J.L. 1982. Factors affecting the inoculum potential of VA and ectomycorrhizal fungi in forest soils of southwest Oregon and northern California.
Ph.D. thesis. Corvallis, Ore.: Oregon State University.
Parke, J.L., Linderman, R.G. and Trappe, J. M. 1983a. The role of ectomycorrhizas in drought tolerance of Douglas-fir seedlings. New Phytol. 95:83-
95.
Parke, J.L., Linderman, R.G. and Trappe, J. M. 1983b. Effects of forest litter on mycorrhiza development and growth of Douglas-fir and western red cadar seedlings. Can
J. For. Res 13:666-671.
Parry, M.S. 1953. Tree planting in Tanganyika: methods of planting.
East African Agricultural Journal 18:102-115.

61
Perry, D.A., M.M. Meyer, D. Egeland, S.L. Rose, and D. Pilz. 1982.
Seedling growth and mycorrhizal formation in clearcut and adjacent undisturbed soils in Montana: a greenhouse bioassay. For. Ecol. Manage. 4:26 1-273.
Perry, D.A., and Rose, S.L. 1983. Soil biology and forest productivity: opportunities and constraints, in R. Ballard and S. P. Gessel (eds.) I.U.F.R.O. Symposium on Forest Site and Continuous Productivity. USDA Forest Service. Pac.
NW For. Rang. Exp. Sta. Gen. Tech. Rep. PNW-163. Portland, OR. pp. 229-237.
Pilz, D.P., and Perry, D.A. 1984. Impact of clearcutting and slash burning on ectomyconhizal associations of Douglas-fir. Can. J. For. Res. 14: 94-
100.
Reid, C.P.P. 1979. "Mycorrhizae and water stress." In Root physiology j ymbiosis, edited by A. Riedacker and M.J. Gagnaire-Michard, 392-408.
Nancy, France: IIJFRO Symposium.
Rose, S.L., Perry, D.A., Pilz, D. and Schoenberger, M.M. 1983. Allelopathic effects of litter on the growth and colonization of mycorrhizal fungi. J. Chem. Ecol 9(8): 1153-
1162.
Slankis, V. 1974. Soil factors influencing formation of mycorrhizae.
Annu. Rev. Phytopathol. 12:437-457.
Steel, R.G.D., and Torrie, J.H. 1980. Principles and procedures of statistics. McGraw-Hill Book Co., New York, NY.
Widden, P., and Parkinson, d. 1975. The effects of forest fire on soil microfungi. Soil
Biol. Biochemistry. 7:125-138.
Wright, E., and R.F. Tarrant. 1958. Occurrence of mycorrhizae after logging and slash burning in the Douglas-fir forest type. U.S. Dep. Agric. For. Serv.
Res. Pap. PNW-160.

CHAFFER IV
MICHAEL P. AMARANThUS & DAVID A. PERRY
Department f Forest Science. Oregon State
University., Corvallis.,
QB.
97331 USA
62
ABSTRACT
In order to reinoculate soil with mycorrhizal fungi, small amounts (about 150m1) of soil from an established Douglas-fir plantation were added to planting holes when
Douglas-fir seedlings were planted on a old, unrevegetated clearcut in the Kiamath
Mountains of Oregon. Seedlings were lifted throughout the growing season to determine the influence of soil transfer on the rate of root tip initiation and mycorrhiza formation.
Six weeks after planting, seedlings receiving plantation soil had formed 62% more root tips than controls; however differences were no longer statistically significant 15 weeks after planting. By this time, a small percentage of root tips were visibly mycorrhiza: seedlings receiving transferred soil had the most colonization (13.6 vs 3.5 per seedling, pO.O5). Of seedlings receiving transfer soil, 36.6% survived the first growing season, compared to 11.3% of control seedlings At this high elevation, soils often remain frozen into the spring, leaving only a brief period between the time that soils are warm enough for root growth and the onset of suimner drought. Under these conditions, rapid root growth and mycorrhiza formation stimulated by plantation soil transfer increases the ability of seedlings to survive the first growing season.

63
In the Kiamath Mountains of southwest Oregon and northwest California, clearcut sites are planted with nursery-grown conifer seedlings after site preparation. On many sites in this area, low water-holding capacity of the soil, infrequent summer precipitation, and temperature extremes limit the period during which tree seedlings can establish.
Mortality is often high in the first year after outplanting (Hermann 1965; Hobbs et al.
1980; Parke et aL 1984; Chapter III).
Reduced mycorrhiza formation has been reported on seedlings of Douglas-fir
[Pseudotsuga menziesii (Mirb.) Franco] grown in soil from unreforested clearcuts in the
Kiamath Mountains (Perry and Rose 1983; Parke et al., 1984; Amaranthus et al. 1987).
Rapid formation of mycorrhizae may be especially critical to seedling survival in harsh environments (Perry et al. 1987), and poor mycorrhiza formation probably contributes to high seedling mortality. Seedling survival was significantly enhanced on an unreforested site in southwest Oregon (Cedar Camp) when small amounts of soil from established conifer plantations were added to planting holes (Chapter III). Here we report the results of a second study to determine the influence of soil transfers on the rate of root-tip and mycorrhiza formation on planted seedlings.

64
METHODS
Site characteristics
Cedar Camp (T4OS, R6W) is in the Klamath Mountains of southwest Oregon, an area characterized by rugged, steeply dissected terrain and shallow skeletal soils. Summers are hot and dry; most of the annual precipitation occurs in the cold winters. The site is 1720 m above sea level, with a southwest aspect and 50% slope. Soils are sandyskeletal, excessively drained, mixed Entic Cryumbrepts; the parent material is quartz diorite. At the time of the study, the adjacent undisturbed forest was dominated by white fir [Abies concolor (Gord. & Glend.) Lindi. ex Hildebr.], Douglas-fir, Shasta red fir
(Abies magnfica A. Murr.) and incense-cedar [Calocedrus decurrens (Torn) Florin].
The clearcut, logged in 1969, had a sparse cover of annual grasses, herbs, bracken fern
[Pteridium aquilinum (L) Kuhn] and red elderberry (Sambucus callicarpa Greene).
Although the site had been replanted several times, only a few scattered seedlings survived (fewer than 10 ha-1).
Planting methods
Five replicate blocks (3 X 3 m) were scalped of preexisting vegetation on
April 15, 1986, and planted immediately with nonmycorrhizal 1-0 Douglas-fir container stock. In each block, sixteen seedlings per treatment were planted 40 cm apart in a
4 X 4 array in a randomized block design; at least 1 m separated treatments. One worker planted all seedlings in a block. Each seedling was planted in a hole to which
(1) 150 ml of soil from an 15 year-old Douglas-fir plantation was added simultaneously
(PS) or (2) no transferred soil was added (control, C). The 15-year-old plantation was on a soil type similar to that of Cedar Camp and was at a similar elevation. Transferred soil was collected 5 h or less before planting from the feeder-root zone (top 20 cm of mineral soil) of 12 randomly selected Douglas-fir trees. Basal diameter 1 cm above the soil

65 surface was measured with calipers at the time of planting. Six, 8, and 15 weeks after planting, 10 live seedlings per treatment (2 per block) were carefully excavated, placed on ice in the field, and transported to the laboratory, where they were stored at 2°C.
At the end of the growing season (October 15, 1986), diameters and leaders of remaining seedlings were measured. Seedling roots were examined for numbers and types of mycorrhizal tips within 14 days of excavation. Soil was gently washed from roots, and roots were subsampled in three 1.5-cm cross-sections of the upper, middle and lower root system. All active root tips in these sections were tallied and identified as nonmycorrhizal or mycorrhizal. Root cross-sections were examined for the presence of a
Hartig net indicating mycorrhizal colonization. Tips that appeared inactive or dead were not counted.
Statistical analysis
Root tip and mycorrhizal counts were log-transformed to compensate for log normally distributed values (Steel and Torrie 1980). Percentage survival data were transformed to an inverse sine, and basal diameters were converted to basal area.
Student's 1-test was used to compare differences among treatment means for seedling basal-area growth, survival, and root-tip and mycorrhizal formation.

66
RESULTS
Six and 8 weeks after outplanting, seedlings receiving plantation soil had significantly more root tips than controls (Table IV-1), but after 15 weeks, differences were no longer significant. Mycorrhizae were not apparent until the final lifting (July 25), when they still formed a small proportion of total tips (Table IV-1). Seedlings receiving transferred plantation soil averaged nearly four times more mycorrhizal tips than controls.
Mycorrhizae in both treatments were formed by Rhizopogon sp., as identified by color and morphology. Survival at the end of the growing season was more than three times higher for PS seedlings than for controls (Table IV-1). Basal area and leader growth of surviving PS and control seedlings did not differ significantly.

67
Table IV-1 Response of Douglas-fir seedlings to soil transferred from an established plantation (PS).a
Control PS
Root tips/seedling after:
6 weeks
8 weeks
15 weeks
61.0 (5.5)
85.2 (7.9)
75.4 (13.2)
98.8 (20.5)*
109.8 (8.9)*
94.2 (14.2)
Mycorrhizal tips/seedlingb
3.5 (1.4) 13.6 (5.1)*
Survival (%)
Growth
Basal area (mm2)
Height (mm)
11.3 (0.4)
0.97 (0.10)
53.0 (12.0)
36.6 (47)*
2.06 (0.92)
61.0 (7.4) a
Values are means (standard error).
* designates values differing significantly from the control by Student's t-test (cx < 0.05).
b
Measured 15 weeks after outplanting, when tips first became apparent.

68
DISCUSSION
We observed increased seedling survival after soil transfer from well-stocked plantations. The low survival values in this study reflect the difficulties in seedling establishment at Cedar Camp, where four previous reforestation efforts have failed. At this high elevation, soils often remain frozen well into spring, leaving only a brief period between the time that soils are warm enough for vigorous root growth and the onset of summer drought. Under these conditions, rapid root growth is essential if seedlings are to survive the first growing season.
The importance of mycorrhizae for seedling establishment on droughty sites is well-documented (Mikola 1970; Slankis 1974; Reid 1987). Rhizomorph-formers, such as
Rhizopogon sp., are particularly important in water transport (Parke et al. 1983). Where rapid capture of soil resources is necessary for survival, decline of mycorrhizal fungi and associated rhizosphere organisms in the absence of host plants may initiate a self-reinforcing trend in which reduced populations of rhizosphere organisms lead to poor seedling survival, leading in turn to further loss of rhizosphere organisms (Perry et al. 1987).
This is apparently what happened at Cedar Camp, where ectomycorrhizal plants have been absent since 1969, and mycorrhiza formation on conifer seedlings is reduced (Chapter III).
Both biotic and abiotic factors in the transferred soil may have enhanced root-tip and mycorrhiza formation. Root-tip formation could have been stimulated by the presence of mycorrhizal inocula, and tips may have been colonized before the characteristic morphology and color of ectomycorrhizae appeared. Rhizosphere bacteria, almost certainly abundant in plantation soil, can stimulate root-tip and mycorrhiza formation, a poorly understood effect that apparently depends on complex interactions between biotic and abiotic soil factors (Bowen and Theodorou 1979; Garbaye and Bowen 1987). Associative nitrogen-fixing bacteria, nonnodule formers found in plant rhizospheres, also

69 could have played a role in our results. Improved growth and survival of Douglas-fir seedlings receiving soil transfers from ectomycorrhizal Pacific madrone (Arbutus menziesii Pursh) was associated with relatively high levels of associative N fixation in
Douglas-fir rhizospheres on another site (Amaranthus et al. 1987a).
Organic matter and root exudates stimulate or, occasionally, inhibit root tip and mycorrhiza formation (Slankis 1974; Alvarez et al. 1979). Compounds released by roots, mycorrhizal fungi, or other rhizosphere organisms could have enhanced root production by seedlings receiving transferred soil. Ethylene, a hormone produced by some rhizosphere bacteria, stimulates or inhibits root-tip production, depending on concentration (Graham and Linderman 1981). Siderophores, important iron chelators produced by mycorrhizal fungi and rhizosphere bacteria, are reduced in some clearcuts (including
Cedar Camp), and preliminary evidence indicates that seedlings grown in siderophoredeficient soils are iron-limited (Perry et al. 1984).
Other soil nutrients can influence formation of mycorrhizae (Slankis 1974), but only 0.1 to 0.2 g N and less P, Ca, Mg, and K were added to each planting hole with transferred soils (Chapter III). These small amounts are unlikely to have influenced either root tip or mycorrhiza formation, particularly since macronutrient concentrations of plantation and clearcut soils did not differ (Chapter III). Although micronutrient effect cannot be ruled out, it seems likely that our results were produced by biotic, rather than abiotic, factors
Diminished root and mycorrhiza formation after disturbance can reduce the ability of a seedling to become established, especially in environmentally rigorous areas where the period favorable for seedling growth is short. Under these conditions, soil transfer from well-stocked plantations rapidly stimulates root-tip production, more abundant mycorrhiza formation, and seedling survival. This may provide useful insights into the reforestation of difficult sites, not only in southern Oregon but also in other degraded forest ecosystems. This study adds to the growing evidence demonstrating close linkage be-

tween the above-ground forest community and the biological properties of soil. Further study is needed in order identify the effects and interactions of specific microorganisms in transfer soils.
70
ACKNOWLEDGEMENTS
Research was funded by National Science Foundation grant number BSR-8400403.
Special thanks to Deborah Parrish for considerable assistance in field and laboratory analysis.

71
Alvarez, I.F., Rowney, D.W. and Cobb, F.W., Jr. 1979. Mycorrhizae and growth of white fir seedlings in mineral soil with and without organic layers in a
California forest. Can. J. Forest Res. 9:311-315.
Amaranthus, M.P. and Perry, D.A. 1987. Effect of soil transfer on ectomycorrhiza formation and the survival and growth of conifer seedlings on old, nonreforested clearcuts. Can. J. Forest Res. 17:944-950.
Amaranthus, M.P., Li, C.Y. and Peny, D.A. 1987a. Nitrogen fixation within mycorrhizae of Douglas-fir seedlings. p. 79. In: Sylvia, D.M., Hung, L.L.
and Graham, J.H. (Eds) Mycorrhizae in the Next Decade: Practical Applications and
Research Priorities. Univ. of Florida, Gainesville.
Amaranthus, M.P., Perry, D.A. and Borchers, S.L. 1987b. Reduction of native mycorrhizae reduce growth of Douglas-fir seedlings p. 80. In: Sylvia, D.M.
and Graham, J.H. (Eds) Proceedings of the North American Conference on Mycorrhizae. Univ. of Florida, Gainesville.
Bowen, G.D. and Theodorou, C. 1979. Interactions between bacteria and ectomycorrhizal fungi. Soil Biol. Biochem. 11:119-126.
Garbaye, J. and Bowen, G.D. 1987. Effects of different microflora on the success of ectomycorrhizal inoculation of Pinus radiata. Can. J. Forest Res.
17:941-943.
Graham, J.H. and Linderman, R.G. 1981. Effects of ethylene on root growth, ectomycorrhizal formation, and fusarium infection of Douglas-fir. Can. J
Bot. 59: 149-155.
Hermann, R.K. 1965. Survival of planted ponderosa pine in southern
Oregon. Forest Research Laboratory, Oregon State Univ., Corvallis. Res. Pap. 2.

72
Hobbs, S.D., Byars, R.H., Henneman, D.C. and Frost, C.R. 1980.
First-year performance of 1-0 containerized Douglas-fir seedlings on droughty sites in southwestern Oregon. Forest Research Laboratory, Oregon State Univ., Corvallis.
p.
Mikola, p. 1970. Mycorrhizal inoculation in afforestation. Int. Rev.
Phytopathol. 12:437-457.
Parke, J.L., Linderman, R.G. and Trappe, J. M. 1983. The role of ectomycorrhizas in drought tolerance of Douglas-fir seedlings. New Phytol. 95:83-
95.
Parke, J.L., Linderman, R.G. and Trappe, J.M. 1984. Inoculum potential of ectomycorrhizal fungi in forest soils of southwest Oregon and northern California.
Forest Sci. 30:300-304.
Perry, D.A., Molina, R. and Amaranthus, M.P. 1987. Mycorrhizae, mycorrhizospheres and reforestation: Current knowledge and research needs. Can. J
Forest Res. 17:929-940.
Perry, D.A. and Rose, S.L. 1983. Soil biology and forest productivity:
Opportunities and constraints. p. 229-238. In: Ballard, R. and Gessel, P. (Eds)
IUFRO Symposium on Forest Site and Continuous Productivity. USDA Forest
Serv., Pacific NW Forest and Range Exp. Sta., Portland, Oregon. Gen. Tech. Rep.
PNW- 163.
Perry, D.A., Rose, S.L., Pilz, D. and Schoenberger, M.M. 1984.
Reduction of natural ferric iron chelators in disturbed forest soils. Soil Sci. Soc. Am.
J. 48:379-382.
Reid, C.P.P. 1987. Mycorrhizae and water stress.
Riedacker, A. and Gagnair-Michard, J. (Eds) Root Physiology and Symbiosis.
IUFRO Symposium Proceedings.
Slankis, V. 1974. Soil factors influencing formation of mycorrhizae.

Annu. Rev. Phytopathol. 12:437-457.
Steel, R.G.D. and Torrie, J.H. 1980. Principles and Procedures of
Statistics. McGraw-Hill, New York.
73

74
CONCLUSIONS AND SYNTHESIS
Much of the research on reductions in populations of beneficial organisms after disturbance has focused on ectomycorrhizae. Although information on other organisms is scanty in the Pacific Northwest, mycorrhizal fungus populations may serve as indicators of the health and vigor of other associated beneficial organisms. Mycorrhizae provide a biological substrate for other microbial processes. For example, in a Douglas-fir system, mycorrhizae provided 50% of the annual biomass returned to the soil and 42% of the annual nitrogen release (Fogel and Hunt 1983). Microbial activity generally is stimulated in soil surrounding ectomycorrhizae (Oswald and Ferchau 1963, Rambelli 1973) an effect that likely extends along the vast expanse of ectomycorrhizal fungal mycelia in the soil.
Because most forest-tree species in the Douglas-fir Region require ectomycorrhizae for nutrient and water uptake, the importance of understanding the relationship between disturbance, site conditions, and mycorrhiza impact cannot be overstated. Numerous authors have reported reductions in mycorrhiza populations due to forest disturbance (Harvey et al. 1980, Parke 1982, Perry et al. 1982, Chapter I). However, the degree of reduction and its impact on forest productivity vary widely and depend on many factors.
Type and Severity of Disturbance
The most widespread activities which alter both the aboveground and belowground environments and which therefore potentially impact populations of soil organisms are timber harvest and site preparation. In the Pacific Northwest, clearcutting and prescribed burning are the common harvesting and site-preparation practices. Soil nutrient status, moisture, temperature, pH, and organic matter content, litter inputs, and species composition affect the growth and occurrence of soil organisms (Harvey et al.

75
1980)and all of these are influenced by harvesting and site preparation. Clearing vegetation and disturbing the forest floor remove nutrients and reallocate them within the ecosystem. Harvesting host trees eliminates the photosynthate source for dependent ectomycorrhizal fungi and associated microbes. Converting a mature forest to a clearcut typically increases soil temperatures once the protective canopy is gone. Prescribed broadcast burning increases soil pH, creates a nutrient flush, and can reduce litter and duff levels (Amaranthus and McNabb 1984). Soil organic matter, humified material, and decaying wood are centers of microbial activity and can substantially diminish as a result of intense fire. Changes in aboveground community composition alter the form of root exudates and litter leachates.
Wright and Tarrant (1958) found fewer ectomycorrhizae on Douglas-fir seedlings growing in burned, compared to unburned, clearcuts. The greatest reductions were associated with the hottest burns. Thus, not only the type of activity, but its severity, is critical. Parke (1982) compared mycorrhiza formation in soils from burned and unburned clearcuts of 36 "difficult to regenerate" sites in northwest California and southwest
Oregon. Douglas-fir and ponderosa pine (Pinus ponderosa Laws.) seedlings grown in soils from the burned clearcuts formed 40% fewer ectomycorrhizae, and seedlings grown in soils from the unburned clearcuts 20% fewer ectomycorrhizae, than seedlings grown in undisturbed forest soil. Yet it is difficult to generalize about effects of burning on microbial populations because they are highly dependent on duration and intensity of fire as well as soil and site conditions (Perry and Rose 1983).
Because ectomycorrhizae predominate in the organic layers of the soil (Trappe and Fogel 1977, Harvey et al. 1979), the degree of organic matter lost from a site can influence mycorrhiza populations. Harvey et al. (1979) found more than 87% of the active ectomycorrhizal fungus types in humus and decaying wood in a mature Douglasfir/larch (Larix) forest. Moreover, the physical consumption of humidified material affects not only ectomycorrhizae but an array of other beneficial organisms tied to site

productivity. Habitat for small mammals that are important in distributing fungal spores of several belowground mycorrhizal fungi (Maser et al. 1978) also can be lost. Thus, numbers, diversity, and activity of beneficial soil organisms can be reduced by repeated removal of organic matter from a site.
76
Diversity of Soil Organisms
The diversity of organisms within the soil buffers the impact of disturbance on forest sites. Disturbance did not reduce ectomycorrhiza formation on Douglas-fir seedlings grown in soil from extremely productive sites in the Oregon Cascades, where diversity of ectomycorrhizal fungi is high (Schoenberger and Perry 1982, Pilz and Perry
1984). However, the proportion of each mycorrhizal fungus type shifted significantly with soil disturbance and plant community (Chapter II); different soil environments reduced ectomycorrhiza formation by some fungus types and apparently opened niches for others. In contrast, clearcutting significantly lowered ectomycorrhiza formation on
Douglas-fir seedlings grown in soil from a harsh, less productive site in southwest Oregon, where soil contained few ectomycorrhiza types (Chapter I). Reduced ectomycorrhiza formation correlated positively with decreased basal area Douglas-fir growth after outplanting. The southwest Oregon soil, with low fungus diversity, was poorly buffered against disturbance, compared to the Cascades soils.
Climatic Conditions
Climate influences seedling growth and ectomycorrhiza formation (Harvey et al.
1980, Pilz and Perry 1984). The importance of early mycorrhiza formation in dry areas has been emphasized (Parry 1953, Mikola 1970). Dry climates may limit the activity of mycorrhizal fungi by decreasing the length of time for spore production, germination, and optimal mycelial growth, which in turn can decrease the chances for planted seedlings to become colonized (Chapter III). Seedlings in moist climates may be able to survive

77 longer without mycorrhizae than those in dry climates, increasing their chances of becoming colonized. Moisture content also affects uptake of certain nutrients by mycorrhizae (Gadgil 1972).
Seedlings growing in cold climates may also require rapid, early mycorrhizal colonization to take advantage of the short growing season and obtain the necessary nutrients and water to survive the long cold season and early frosts. In studies in the
Kiamath Mountains of northwest California and southwest Oregon, Amaranthus and
Perry (Chapter III, IV) found that mycorrhiza formation most strongly influences seedling survival and growth on sites limited by both moisture and temperature.
Biotic Conditions
The importance of aboveground species composition and arrangement to belowground biological functioning is unclear. It is increasingly apparent, however, that an ectomycorrhizal fungus can link some plant species with fungal mycelia (Bjorkman 1970,
Read et al. 1985, Finlay and Read 1986). In the natural forest environment, ectomycorrhizal fungi supported by nonconiferous hosts can actively colonize conifer seedlings.
Root-chamber analysis of the development of ectomycorrhizal mycelium has shown that expanding hyphal fans not only act as nutrient-absorbing structures but also colonize nonmycorrhizal feeder roots in host-plant combinations within and among species. Using radioactive labeling, Finlay and Read (1986) have demonstrated the free movement of carbon among plants connected by mycorrhizal mycelia. Clearly, the existence of "pipelines" for distributing materials among plant species has important implications for forest regeneration.
Little is known of the persistence and distribution of ectomycorrhizae in the absence of living hosts. It has been suggested (Hacskaylo 1973) that ectomycorrhizal fungi do not persist long in the absence of host-supplied substrates. In the Klamath
Mountains of northwest California and southwest Oregon, sites that have been logged

78 and burned are often rapidly invaded by woody shrubs (Gratkowski 1961). Many of these shrubs, members of the Ericaceae and Fagaceae, form mycorrhizae with many of the same fungi as do members of the Pinaceae (Molina and Trappe 1982). This mechanism of natural redundancy preserves mycorrhiza diversity during periods of rapidly changing community structure.
In Chapter II we transferred small amounts of soil from a Pacific madrone (Arbutus menziesii Pursh) stand to planting holes at three localesa site cleared of whiteleaf manzanita (Arctostaphylos viscida Parry), a meadow cleared of annual grasses, and under
Oregon white oak (Quercus garryana Hook)on which Douglas-fir seedlings were grown. In the first year, they found more rapid mycorrhizal colonization of Douglas-fir feeder roots, and dramatically improved seedling survival and growth, on the site cleared of manzanita than in the meadow under similar soil, moisture, and temperature conditions. In the second year, Douglas-fir seedling performance continued to increase dramatically on the site cleared of manzanita compared to the other two locales. If mortality and basal-area growth of surviving individuals are taken into account, on an area basis
Douglas-fir inoculated with soil from the Pacific machone stand and growing on the site cleared of manzanita was roughly 10 times that of seedlings growing in the meadow and
100 times that of seedlings growing under oak. The effect of the machone inoculum on the manzanita site was almost certainly biological: it introduced a new mycorrhiza type and was ineffective when pasteurized. On the other hand, relative ineffectiveness of the machone inoculum in the meadow and under oak indicates that more is involved in the
Douglas-fir response than the simple presence or absence of the "right" organism. Rapid mycorrhiza formation, especially on sites that are difficult to regenerate, increases the chances that succeeding species will become established.
Some woody shrub species may act as reservoirs not only of mycorrhizal fungi but of other microflora as well. Significantly higher rates of nitrogen fixationand increased seedling survival and growthwere found in association with the roots of

79
Douglas-fir seedlings in a stand cleared of whiteleaf manzanita than in a meadow cleared of annual grass (Amaranthus et al. 1987). Azospirillium, an N2-fixing bacterium, was isolated within the mycorrhizae of Douglas-fir at the manzanita site. Whiteleaf manzanita occupies particularly hot, dry sites where fire is frequent. Because high N losses can accompany intense fire, natural mechanisms by which N is returned to the soil are important to long-term site productivity. Quite likely, the N fixed and gradually accumulated in association with mycorrhizae is biologically important for individual conifers over their long life.
We suggest that conifers and some woody shrubs form successional guilds, in which the rapidly sprouting pioneer members of the guild maintain the guild's shared soil microflora, forming a biological time bridge between old and new conifer stands. In the long run, maintaining diversity of soil microflora by pioneering shrubs may optimize conifer performance during the varied conditions likely over a rotation.
Effect of nonhosts over time
Many grass species and shrub species such as Ceanothus and Rubrus (e.g., blackberry, salmonberry) form vesicular-arbuscular mycorrhizae (YAM) with fungi incompatible with members of the Pinaceae (Rose and Youngberg 1981; J.M. Trappe, unpublished data, USDA Forest Service, Pacific Northwest Research Station). On sites long dominated by YAM species, the ectomycorrhizal fungi needed by members of the Pinaceae may gradually disappear, and the soil microbial complex associated with ectomycorrhizae will shrivel. Invasion of sites by nonectomycorrhizal plants over years can seriously affect reforestation (Amaranthus and Perry Chapter III) and long-term yield, particularly in the case of ectomycorrhizal tree species growing on difficult sites where seedlings must establish ectomycorrhizae early to survive. Long-term changes in soil microflora associated with nonhost species could affect patterns of decomposition; nutrient and water retention, availability, and uptake; and the balance between pathogens and patho-

80 gen-inhibiting organisms.
How long soils retain their mycorrhizal colonization potential in the absence of living hosts is unknown. Ectomycorrhizal spores and hyphal fragments have remained metabolically active after 2 years in Scandinavian forests, though the number of active fragments dropped dramatically over that period (Persson 1982, Ferrier and Alexander
1985). In the Pacific Northwest, mycorrhiza formation generally decreases as the length of time between disturbance and reforestation increases (PiIz and Perry 1984, Perry et al.
1987).
The importance of soil to primary productivity is well known. Soils are banks of nutrients and water, and provide the matrix for biological processes involved with nutrient cycling. Mycorrhizae are key mediators in the close coupling of soils and plants.
The picture emerging from this thesis suggests that, in some cases, this coupling is more intimate and more vunerable than generally believed.

81
Allen, E.B., and M. F. Allen, 1980. Natural reestablishment of vesicular-arbuscular mycorrhizae following strip-mine reclamation in Wyoming J. Appi. Ecol. 17:139-
147.
Alvarez, I.F., Rowney, D.W. and Cobb, F.W., Jr. 1979. Mycorrhizae and growth of white fir seedlings in mineral soil with and without organic layers in a
California forest. Can. J. Forest Res. 9:311-315.
Amaranthus, M. P., and McNabb, D. H. 1984. Bare soil exposure following logging and prescribed burning in southwest Oregon. In New forests for a changing world.
Proceedings, 1983 Society of American Foresters National Convention, Portland,
Oregon. pp. 234-237.
Amaranthus, M.P. 1984. Monitoring forest shade utilizing the Solar
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