This file was created by scanning the printed publication.
Errors identified by the software have been corrected;
however, some errors may remain.
Revegetating Riparian Trees in Southwestern Floodplains1
Edwin A. Swenson 2
Charles L. Mullins 3
Abstract.--Riparian areas continue to be drastically
altered, usually by man's activities. Managers have generally been unsuccessful in using conventional techniques
to replace riparian trees. Our experiments with Rio Grande
cottonwood, narrowleaf cottonwood, and Gooding willow have
shown that a simple and inexpensive method for their reestablishment is now available.
INTRODUCTION
levels, elimination of flooding, low precipitation, grazing, and invasion by saltcedar (Tamarix
chinensis) (Anderson et al., 1977, Campbell and
Dick-Peddie 1964, Horton 1972, and McKinney 1981).
Riparian trees of the Southwest are important to
wildlife, as studies have shown (Carothers et al.,
1974, Freehling 1982, Hink and Ohmart 1984, Hubbard 1977, and Stamp 1978). Many major Southwest
floodplains, however, no longer support viable
riparian stands. Agricultural drainage, channelization, flood control, livestock, irrigation
diversions, and control of phreatophytes have
taken a heavy toll (Carothers 1977, Engel-Wilson
and Ohmart 1979, Graf 1980, Johnson 1970, Johnson
and Carothers 1975, and Platts 1979).
From 1981 to 1983, we studied the feasibility of
using Rio Grande cottonwood (Populus fremontii),
narrowleaf cottonwood (!. angustifolia), and Gooding willow (Salix nigra var. vallicola) to restore
riparian stands. Our method was to place large
pole cuttings in holes drilled to deep water
tables or in lysimeters. Our objectives were:
(1) to determine if tree cuttings would become
established where groundwater was 7 to 12 feet
below ground surface, (2) to determine if survival
was related to time of taking and setting the cuttings, and (3) using lysimeters to establish relationships between tree survival and the depth of
cutting placement above constant water tables.
Older relict stands are dying and little natural
reproduction is occurring because of dry surface
soils, low precipitation, grazing pressure, and
drastic reductions in flooding (Anderson and
Ohmart 1976, Engel-Wilson and Ohmart 1979, and
Glinski 1977). Managers of these riparian ecosystems have generally been unsuccessful in using
conventional techniques to replace trees: site
conditions are too dry for the use of rooted seedlings, and irrigation is too costly. New technologies are being developed to reclaim degraded or
destroyed riparian woodland (Anderson and Ohmart
1976, Anderson et al., 1978). Tree establishment,
however, has been hampered by lowered groundwater
STUDY AREA AND METHODS
Study plots were established within ,the historic
floodplain of the Rio Grande at locations south
of Albuquerque, New Mexico. Groundwater was monitored by observation wells during the period of
the study. Some study plots were placed where
water fluctuated naturally; others were located in
lysimeters where water tables were stabilized
mechanically.
1Paper presented at the Interagency North
American Riparian Conference, Riparian Ecosystems
and Their Management: Reconciling Conflicting
Uses, Tucson, Arizona, April 16-18, 1985.
2Edwin A. Swenson is the State Biologist,
U.S.D.A., Soil Conservation Service, Albuquerque,
N.M.
3Charles L. Mullins is a Fish and Wildlife
Biologist, U.S.D.I., Fish and Wildlife Service,
Albuquerque, N.M.
The soils are deep sandy loams; some have narrow
clay lenses scattered throughout the profile.
Groundwater contains 700 to 900 ppm of dissolved
solids and is considered suitable for crop irrigation. Annual precipitation averaged slightly
under 6 inches during the 3 years of the study.
135
solids and is considered suitable for crop irrigation. Annual precipitation averaged slightly
under 6 inches during the 3 years of the study.
We found little difference in survival or growth
rates by species. Not all cuttings produced the
desired top growth; however, some produced ground
level growth, which is undesirable because it
would be accessible to livestock.
Poles were cut from individual saplings growing
locally within leveed river sections where controlled flooding had provided for natural reproduction. Saplings with a basal diameter of 2 to 3
inches and a height of up to 20 feet were used.
All side branches were removed and the top was cut
back to a 3/8-inch diameter.
A number of study plot locations failed to grow
living trees for reasons worth describing. Flooding for periods longer than 3 weeks killed all
established poles. Beaver cut living poles at
ground line and the subsequent low sprouting was
browsed by livestock. Cattle are able to walk
down substantial sized poles, breaking them off at
ground level. Plantings made in the Pecos River
Valley of eastern New Mexico were consistent failures, possibly because of high ground-water salinity (up to 4,000 ppm).
Among all the plots, groundwater depth ranged from
7 to 12 feet. Groups of cuttings (5 to 50 each)
were placed in drilled holes so that the butts
were: (1) at groundwater depth, (2) 2 feet above,
and (3) 4 feet above groundwater. All cuttings
were sized so that 4 to 6 feet of the cutting was
above ground. All holes were backfilled to the
surface. To stimulate top growth, buds on the
lower half of the cutting were wiped off when they
first appeared in the spring (usually April).
Because our goal was a simple, inexpensive planting technique with wide applicability, we did not
use rooting hormones or sealants on the cut surfaces.
Poles exhibited no obvious insect problems and
only slight girdling damage from rodents or lago~
morphs. On the few plots where girdling was a
problem, we installed a plastic netting cylinder
around each cutting.
MANAGEMENT IMPLICATIONS
Plots were divided so that each replication had
equal numbers of dormant poles (cut and planted in
December or January) and greenwood poles (cut and
planted in March after bud development had started).
Placing large dormant cuttings into holes predril·led to known depth of the growing season water
table can be a simple and inexpensive method of
revegetating floodplains.
The manager must
determine, however, that prolonged flooding will
not occur at the site and that beaver and livestock can be controlled.
RESULTS
Excavation of root systems indicated that placing
the poles into the water table will produce better
results where the water table is higher during the
winter planting season (December, January) than
during the growing season. Therefore, it is
essential that water table depth be monitored at
proposed planting sites. We recommend establishing observation wells at proposed sites for at
least one growing season prior to planting. This
monitoring allows better selection of a planting
depth for improved establishment.
Our results indicate that cottonwood and willow
poles can successfully be used to revegetate
floodplains with deep (7 to 12 feet) water tables
during the period of active plant growth. In general, large cuttings (13 to 20 feet long) of all
three native tree species became established.
Vertical growth averaged 30 inches each year.
For dormant poles set with the butts at constant
water tables of 7, 8, 8, and 12 feet, survival
rates were 60, 90, 100, and 77 percent, respectively. Survival was lower for dormant poles
placed 2 and 4 feet above the water table. It was
also lower for greenwood cuttings (table 1).
Use of dormant cuttings is recommended. The suitable time for taking them is almost 90 days, from
November to February. By contrast, the optimal
period for taking greenwood cuttings is 15 to 20
days and their survival is lower. Planting the
cuttings at anticipated growing season water table
depth rather than above it will enable the poles
to have the best chance of success.
Poles in plots with naturally fluctuating water
tables had lower rates of survival than those in
plots with constant water tables (table 2). Fluctuating water tables dropped as much as 20 inches
from April to September, the period of active
growth. Relationships of survival to depth of
cutting placement and to time of taking the cuttings were similar to those in the constant water
table plots (table 2).
Restocking of depleted riparian areas is not a
permanent solution, however. Without periodic
flooding, on a frequency of once every 20 to 40
years or so, adequate natural reseeding will not
occur.
136
Table 1.--Survival of Cuttings at Constant Groundwater Levels
Type of
Cutting
Method of
Controlling
or Monitoring
Water Table
Planting
'Date
Dormant
Lysimet e r 2
12/80
9/81
9/82
9/83
Dormant
Lysimeter
12/81
9/82
9/83
Dormant
Well 4
1/83
9/83
Greenwood
Lysimeter
3/82
9/81
9/82
9/83
Greenwood
Lysimeter
3/82
9/82
9/83
Survival bl: DeEth (ft.) of
Water
Water Table
7.3 ft.
8.3
I7 ft. 5 ft. 3 ft. I8 ft. 6
Date of
Measurement
Cutting Placement
Table
Water Table
ft.
11 ft.
1 11 • 5 ft.
ft. 4 ft.
------------------------Percent------------------------__ 3
70
80
100
0
80
60
60
100
40
50
50
0
60
50
90
0
50
30
100
100
40
40
30
30
77
100
40
40
70
50
50
0
0
0
100
100
100
50
20
20
60
20
10
90
90
50
50
0
0
IDepth of planted cuttings.
2Ten cuttings placed within each lysimeter; water table artificially controlled at 7.3 ft. or 8.3 ft.
3Das hes mean no cuttings placed at the given depth.
4Water table level monitored by observation well; 20 cuttings placed in each area monitored by a well.
Depth to constant water table averaged 11 ft.
Table 2.--Survival of Cuttings at Fluctuating Groundwater Levels
Type of
Cutting
Plot
Number 1
Planting
Date
Date of
Measurement
Survival bl: DeEth (ft.) of Cutting Placement
Water Table
Water Table
7.0 ft. - 9.4 ft.
7.5 ft. - 9.2 ft.
27 ft. 5 ft. 3 ft. L8 ft. 6 ft. 4 ft.
------------------------Percent-----------__ 3
84
24
0
65
20
0
28
15
0
Dormant
2
12/80
9/81
9/82
9/83
Dormant
3
12/81
9/82
9/83
Greenwood
2
3/81
9/81
9/82
9/83
Greenwood
3
3/82
9/82
9/83
73
60
50
35
30
60
60
55
40
5
5
80
56
55
30
24
20
10
0
0
0
1plot 2 had five replications, five poles per treatment (dormant and greenwood), and a
fluctuating water table at depths of 7.5 ft. to 9.2 ft. Plot 3 had three replictions, ten
poles per treatment, and a fluctuating water table at depths of 7.0 ft. to 9.4 ft.
2Depth of planted cuttings.
3Dashes mean no poles were placed at the given depth.
137
We believe that cottonwoods and willows can be
successfully established in small openings within
existing stands of saltcedar. Further study is
needed, but our observation of natural stands suggest that these trees will overtop and shade out
the saltcedar.
Freehling, M. D. 1982. Riparian woodlands of the
Middle Rio Grande Valley, New Mexico: a
study of bird populations and vegetation.
U.S. Fish and Wildlife Service, Office of
Environment, Albuquerque, New Mexico. 35 pp.
Glinski, R•. L. 1977. Regeneration and distribution of sycamore and cottonwood trees along
Sonoita Creek, Santa Cruz County, Arizona.
Pages 123-166. In Importance, Preservation,
and Management of Riparian Habitat: A Symposium. R. R. Johnson and D. A. Jones
(tech. coord.). U.S. Forest Service General
Technical Report RM-43 , Rocky Mt. Forest and
Range Exp. Sta., Fort Collins, Colorado.
LITERATURE CITED
Anderson, B. W., A. Higgins, and R. D. Ohmart.
1977. Avian use of saltcedar communities in
the Lower Colorado River Valley. Pages 128136. In Importance, Preservation, and Management of Riparian Habitat: A Symposium.
U.S. Dept. of Agriculture, Forest Service,
Tucson, Arizona. 217 pp.
Graf, W. L. 1980. Riparian management: a flood
control perspective. J. of Soil and Water
Conservation. 35:158-161.
Anderson, B. W. and R. D. Ohmart. 1976. A vegetation management study for the enhancement
of wildlife along the Lower Colorado River.
Contract No. 7-07-30-V0009. Bureau of Reclamation. Lower Colorado Region. 190 pp. plus
appendices.
Hink, V. C. and R. D. Ohmart. 1984. Middle Rio
Grande biological survey. Contract No.
DACW47-81-C-0015. Corps of Engineers, Albuquerque District. 112 pp. plus appendices.
Horton, J. S. 1972. Management problems in phreatophyte and riparian zones. J. of Soil and
Water Conservation. 27:57-61.
Anderson, B. W., R. D. Ohmart, and J. Disano.
1978. Revegetating the riparian floodplain
for wildlife. Pages 318-331. In Strategies
for Protection and Management of Floodplain
Wetlands and Other Riparian Ecosystems.
U.S. Dept. of Agriculture, Forest Service,
Calloway Gardens, Georgia. 410 pp.
Hubbard, J. P. 1977. Importance of riparian
ecosystems: biotic considerations. Pages
14-18. In Importance, Preservation, and
Management of Riparian Habitat: A Symposium. U.S. Dept. of Agriculture, Forest
Service, Tucson, Arizona. 217 pp.
Campbell, C. J. and W. A. Dick-Peddie. 1964.
Comparison of phreatophyte communities on the
Rio Grande in New Mexico. Ecology 45:492502.
Johnson, R. R. 1970. Tree removal along southwestern rivers and effects on associated
organisms. Amer. Phil. Soc. Yearbook.
1970. Pages 321-322.
'
Carothers, S. W. 1977. Importance, preservation,
and management of riparian habitats: an
overview. Pages 2-4. In Importance, Preservation, and Management ~ Riparian Habitat:
A Symposium. R. R. Johnson and D. A. Jones
(tech. coord.). U.S. Forest Service General
Technical Report RM-43, Rocky Mt. Forest and
Range Exp. Sta., Fort Collins, Colorado~
Johnson, R. R. and S. W. Carothers. 1975. The
effects of stream channel modifications of
birds in the southwestern United States.
Symposium on Stream Channel Modification
Proceedings. Harrisburg, Virginia.
Carothers, S. W., R. R. Johnson, and S. W. Aitchison. 1974. Population structure and social
organization of southwestern riparian birds.
Amer. Zool. 14:97-108.
McKinney, M. 1981. Learning to manage southwestern riparian ecosystems. In Forest
Research West, U.S. Forest Service.
Engel-Wilson, R. W. and R. D. Ohmart. 1979.
Floral and attendant faunal changes on the
Lower Rio Grande between Fort Quitman and
Presidio, Texas. In Strategies for Protection and Management of Floodplain Wetlands
and Other Riparian Ecosystems. R. R. Johnson
and J. E. McCormick (tech coord.). U.S.
Forest Service General Technical Report
WO-12, Washington, D.C. Pages 139-147.
Platts, W. S. 1979. Livestock grazing and riparian/stream ecosystems: an overview. Pages
39-45. In Forum-Grazing and Riparian/Stream
Ecosyste;S. Trout Unlimited, Denver, Colorado. 94 pp.
Stamp, N. E. 1978. Breeding birds of riparian
woodlands in southcentral Arizona. Condor
80:64-71.
138