Facilitating Plant Community Development on Anthropogenic Disturbances Using Seed and Appropriate Gr

1
Facilitating Plant Community Development on
Anthropogenic Disturbances Using Seed and
Appropriate Growth Media
Dot Helm, Palmer Research Center, Agricultural
and Forestry Experiment Station, University of
Alaska Fairbanks
Introduction
2001
1997
Goals of revegetation following mining
disturbance include ground cover and water
quality in the short- and long-term. Wildlife
habitat is frequently a long-term goal in Alaska.
Revegetation efforts range from doing nothing to
actively providing seed, transplants, and/or
selected growth media to facilitate plant
community development. Time frame is also
important for objectives. These images summarize
years of active experimentation or observation
with various plant material treatments (none,
seed, woody transplants) on several growth media
to determine what treatments facilitate plant
community development under what time frames and
conditions.
Growth Media
Natural Colonization
Growth media can be topsoil, overburden, or mixes
of multiple materials. The characteristics can
affect success of revegetation and need to match
the project goals. An abandoned mined site in
southcentral Alaska was revegetated with seed and
fertilizer in mid-1990s. Two overburden materials
"brown" (left side of images) and "gray" (right
side) had little cover in 1997. After 5 years,
the brown material (pH 5.8, CEC 25.1) has had
better growth of seeded grasses and local
colonizers than that on the gray material (pH
8.2, CEC 12.2).
This site was furrowed to increase seed
catchment, but otherwise depended on natural
colonization. After 5 yr, this site had 6
stems/m2 of woody seedlings, mostly Populus
balsamifera but some Betula papyrifera and
occasional Populus tremuloides. Nearby sites that
were seeded and fertilized had only 2 stems/m2
1997
2001
Seed and Fertilizer
In contrast, this site on overburden materials
was heavily seeded and fertilized in 1995. Within
7 yr, most of the grass has died, but the
remaining litter is still protecting the soil.
Native woody species are colonizing, although
with different species, primarily Alnus sinuata.
A study in interior Alaska compared seeding
different species on different growth media AB
horizons (topsoil) and sandstone (overburden).
Left half of plots were initially seeded and
fertilized, and the right half was seeded only
(left, center, treatments on sandstone). Grass
did not establish in unfertilized half, and that
half was reseeded and fertilized in year 5.
Shrubs colonized the initially fertilized halves,
but the reseeded areas had only grass cover in
year 8 (center). Ground cover was limited on AB
materials in year 8 since grasses had died but
comparatively little colonization had occurred
(right), although more cover was present earlier,
emphasizing the importance of longer term studies.
Unseeded vs Seeded on "Topsoil"
On topsoil experimental plots for the proposed
Wishbone mine in southcentral Alaska, some plots
were not seeded to determine natural colonization
trajectories, some were seeded, and others were
planted with woody transplants. By year 7,
grasses had died and colonization on seeded plots
was similar to that on unseeded plots.
Matching plant materials and growth media to
project goals is critical. Salix alaxensis is
frequently used for moose browse, but it
establishes on floodplain soils with pH near 7,
whereas the proposed growth media had pH near
5.2. S. barclayi is an upland species, grows on
soils with pH values near 5, and is also browsed
heavily by moose. S. barclayi tolerated the low
pH and moose browsing after 7 years whereas S.
alaxensis was did not tolerate browsing and low
pH.
Seeded
Unseeded
Use of different species of grasses can alter
successional timing. Nortran tufted hairgrass
persisted longer than many other grasses. While
it slowed the amount of desirable colonization in
the short term, it reduced the undesirable plants
Calamagrostis canadensis and Epilobium
angustifolium, thus facilitating moose habitat
establishment.
Salix barclayi
Salix alaxensis
Conclusions

• Although seeding may slow colonization slightly,
  not seeding does not guarantee establishment of
  vegetation and can result in erosion, salt
  crusting, and colonization by undesirable plants.
• Different growth media have different potentials
  for revegetation.
• Woody species transplants facilitated
  colonization by desirable shade-tolerant
  understory species.
• Use of appropriate plant species on appropriate
  growth media can facilitate establishment of
  target plant communities.
• Seeded grasses may help reduce soil loss in the
  short term and initiate soil building processes
  where natural colonization is too slow.
• Seeded grasses may help reduce colonization of
  undesirable species in the short term.
• Although some seeded grasses may slow
  colonization by desirable species, most grass
  species will die within about 7 years, and
  natural colonization can proceed.

Nortran
Most other grasses
Where woody plants were transplanted on this
project, a closed canopy was created in about 7
years for most plots, thus favoring the
establishment of forest understory species,
another desirable goal of the project.
Natural colonization (stems / m2) by woody
species was not reduced by seeding in the
Wishbone plots.
I thank the following organizations for their
support in the several studies contributing to
this summary Alaska Department of Natural
Resources (Div of Mining, Land, Water Management
AML) Agricultural Forestry Exp. Sta., U. of
Alaska Fairbanks USDA Mcintire-Stennis Forestry
Research Program' Usibelli Coal Mine, Inc.
Alaska Science Technology Foundation
Idemitsu-Alaska, Inc. Alaska Department of
Environmental Conservation Silverado, Inc. U.S.
Department of Interior (U.S. Bureau of Mines)