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,1e Root Decomposition and Organic Hatter in Forest Soils.
and J. M. Helillo, Marine Biological Lab.
C. A. HcClaugherty,* J.
D. Aber, Univ. of Wisconsin-'ladison,
Decomposition of fine roots (less than 3.0 mm diam) was studied in an 80 y ear old mixed hardwood stand
and a 54 year old red pine-white spruce plantation in north central Massachusetts.
Weight loss and changes
in total N, lignin(acetyl bromide method)
and total non-structural carbohydrates
time using litter bags of two mesh sizes and at two soil depths.
(TNC) were followed through
After one year, 77 to 89% of the original
weight remained, N conc entrations remaine d the same or increased slightly, lignin changes were insignificant,
snd TNC decreased significsntly,accounting
for 19 to 48% of the total weight lost.
of fine roots combined with high estimates of annual fine root mortality (4
t/ha)
The
low decomposition rate
in the forest floor indicate
t hat 14.3 t ( 40%) of the hardwood fares t floor and 10 .1 t ( 26%) of the plants tion fares t floor mass is
derived from roots less than 3mm diam.
Site Preparation and Weed Control Treatments Influence Total Above-ground Dry Matter in' 16-year-old Yellow-Poplar Planta­
tions. R.A. Mclaughlin*, and P·.E. Pope, Purdue University.
Yellow-poplar (liriodendron tulipifera l.) plantations est;blished under two leve.ls of 'site preparation treatments
and three levels of weed control· are cQmpared for total above-ground dry matter 16 years after planting. Prior to plant­
in9, site preparation treatments consisted of either disking alone or in combination.with fertilization (448 kg/ha, 12-12­
12) and green manuring. Two-year-old yellow-poplar seedlings were planted at a 3by 3m spacing in the spring of 1965.
Weed control treatments, implemented for three years following planting, were Amizine (8 kg/ha) applied once per season,
cultivatio
. n (rototilled to 8 em) three times per season, and a control which received no weed control. Sample trees were
r·cut and weighed in June, 1980. Total above-ground dry matter yields ranged from 5148 kg/ha for the control plots, which
received neither site preparation nor weed control, to 10,500 kg/ha for the plots receiving both site preparation and
weed control by cultivation. Site prepared plots yielded significantly ·more dry matter (9,085 kg/ha) than disked-only
plots {6,150 kg/ha). Weed control yield increases were substantial (26% av.) but not statistically significant.
F ifteen -Year Response of 35-Year-Old Douglas-fir to Amm onium Nitrate.
Oregon State Un iv
|
R.E. Miller*, and R.F. Tarrant, USDA-FS and .
The effects of varying amounts of ammonium· nitrate fertilizer on diameter, height, and volume growth of a'poor-site
plantation of Pseudotsuga menziesii were measured at various times during a 15-year.period after a ·single .fertilization.
Dosages of 157, 314, and 470 kg N/ha increased gross volume growth by 40, 91, and 103 percent, respectively (54, 123, and
138 m3/ha); the response surface was curvilinear.
Volume growth on fertilized plots exceeded that on unfertilized plots
in all periods; a statistically nonsignificant treatment x period interaction indicated that resporise try the several N
dosages has remained constant over time.
The large magnitude and the long-term duration of this response emphasize the
attractiveness of ammonium nitrate and the importance of direct comparisons of this fertilizer with urea, the' ore
conventional N source for forest fertilization in the Pacific Northwest.
A. Horris*, W.L.
Windrow Composition. L.
Pr:itchett, Unlv. of Florida, and B.F.. Swlndel, USD A-FS.
Nutrient redistribution resulting from windrowing operations was examined on a pine flatwoods site in north central
Sol1, fine branch and root,
and coarse bolewood components were weighed and subsampled for nutrient analysts
Florida.
The quantity of organlc materials and nutrients In the 5.2 kilometers of windrow on the 36
at 101 m wide cross sections.
ha study site was determined from extensive field measurements of cross sectional' area using
egression analysis. lOtal
w lght of the soil, fine branch and root, and·coarse bolewood components were 153, 12, and 14 .metric tons/ha, respectively
Total N and Pcontent of the windrows were determined to be 375 and 17.7 kg/ha.
-
j
Agrowth chamber experiment t•as conducted to determine the effect of rock phosphate (RP), dlcalclum phosphate (DCP)
and phosphoric acid (PA) phosphorus sources on mycorrhizal Infection and subsequent phosphorus uti1 izatlon In Douglas-fir
and western hemlock seedlings. Fungal species tested Included Hebeloma crustullnlforme, Laccarla laccata and Cenococcum
gran Iforme. Seedlings were grown in Leach cell containers which were filled wl th a peat/vermlcul ite mixture to which
inoculum was added. Results from samples taken 180 days after sowing show that mycorrhlza formation ·was enhanced by the RP
and OCPtreatments as compared to the PA treatment. Seedling weight was greatest In the RP treatment. %N did not differ
Seedlings treated with PAhad a greater %P than did those treated with RPor
significantly among the three treatments.
OCP. Douglas-fir seedlings mycorrhizal with L. laccata had greater %P than did seedl lngs mycorrhizal with
H. crustulinlforme or C. granlforrne. Non-mycorrhizal seedlings In the DCP treatment had significantly lower %Pas
compared t0 the mycorrhizal seedlings.
Periodic Leaf Fall and Nutrient Returns in Three Southern Forest Types.
C.E. Pehl* and D.M. Moehring, Texas A&M Univ.
Cumulative· leaf fall and nutrient returns per 4 week periods were measured two consecutive years in an East Texas
beech-magnolia stream forest
(SF) and upland forests of pine-mixed har
. dwood (PH) and planted loblolly pine (PP),
leaf fall averaged 6.4, 8. 7, and 9.5 thousand kg/ha for SF,PH, and PP forest types, respectively.
amount was similar between years, but periodic deposition varied relative to chance storm events.
.Annual
Within types leaf fall
Peak depositions
coincided during late fall, but PH and PP late wiriter and late summer depositions were twice that of the SF primarily
because of the pine in the two former types.
Foliage comprised 75% of the leaf fall in all types;
11% of the SF leaf fall bu,t less than 3% in the others.
ively, for SF, PH, and PP.
fruits contributed
g
and 24.9 k /ha, respect­
Annual cumulative nutrient returns to the forest floor as a percent of the nutrient content
in the forest floor were N,59;
Ca,SO;' Mg,40;
and P,3.
The PH was intermediate.
nutrients in the SF typ e
.
Forest floor weights were .14.1, 12.4,
K,lOO;
and P,SO in the SF.
Values in the PP were
N,30;
Ca,30;
Mg,SO;
K,7;
The differences are explained by more rapid decomposition rates and higher tissue
·