Revegetation Guidelines for Western Montana - Global Restoration ...
Revegetation Guidelines for Western Montana - Global Restoration ...
Revegetation Guidelines for Western Montana - Global Restoration ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Appendix C. Understanding succession to direct successful revegetation<br />
<strong>Revegetation</strong> can be most successful when it works with successional processes to direct<br />
communities toward a desired plant community. Three components can influence the direction of<br />
succession (defined below) and can be modified to direct predictable successional transitions. These<br />
are:<br />
1. Site availability (disturbance) – plays a central role in initiating and altering successional<br />
pathways. Site availability can be a designed disturbance such as seedbed preparation to<br />
produce seed safe sites or herbicide applications <strong>for</strong> weed removal to open niches <strong>for</strong><br />
occupation by desired species. Site availability is important <strong>for</strong> the persistence of many<br />
native species, but can also facilitate noxious weed invasion (Kotanen 1997);<br />
2. Species availability (colonization) – the intentional alteration of seed availability by<br />
influencing seed banks and propagule pools of desired plants and weeds and the regulation<br />
of safe sites <strong>for</strong> desired plant germination and establishment. Weed seed banks can be<br />
depleted through attrition if seed production is prevented or significantly reduced each<br />
growing season. For example, Olson et al. (1997) found the number of spotted knapweed<br />
seeds in the soil was reduced after three years of intensive sheep grazing directed at buds<br />
and flower heads, resulting in decreased weed density.<br />
3. Species per<strong>for</strong>mance – the manipulation of the relative growth and reproduction of plants<br />
in an attempt to shift the plant community in the desired direction. Domestic sheep can shift<br />
a plant community toward desired grasses by selectively grazing <strong>for</strong>bs. In contrast, cattle can<br />
shift a plant community toward <strong>for</strong>bs (e.g. weeds) by selectively grazing grasses. Herbicide<br />
applications can alter resource availability and increase desired species per<strong>for</strong>mance through<br />
competitive weed removal. In other words, soil resources become available <strong>for</strong> neighboring<br />
desired plants through careful herbicide treatment.<br />
Pioneer species (e.g. annual <strong>for</strong>bs or early seral species) are usually the first plant types to begin<br />
growth on a disturbed site. These pioneer species are eventually replaced by later seral species such<br />
as grasses that are replaced over time by shrubs and trees. The replacement of early seral species,<br />
such as <strong>for</strong>bs, by mid-seral species, such as grasses, and eventual replacement by late-seral species,<br />
such as shrubs, to a “climax state”, is plant succession. Noxious weeds act as pioneer species but<br />
interfere with or arrest succession be<strong>for</strong>e it reaches the mid- or late-seral stage most landowners<br />
hope to attain (Munshower 1994). In response, the development of a plant community that is more<br />
mature than the classic pioneer stage can help ensure that noxious weeds do not become<br />
established at the disturbed site with proper weed management.<br />
The first manipulation to a site to make it capable of supporting later seral species is topsoiling, if this<br />
layer is absent. The process of providing or replacing salvaged topsoil upon the subsoil strata can<br />
move the successional process from the primary level to secondary succession given topsoil is<br />
generally “mature” enough to support mid-seral stage plants. Seeding later-successional species can<br />
further accelerate the process of plant succession. However, in some cases, the topsoil may lack the<br />
maturity needed to support late successional or climax communities. Such plant communities<br />
require mature soils with intact and complex nutrient cycles, essential mycorrhizal associations, and<br />
proper surface litter distribution and soil microtopographies that can be easily damaged following<br />
disturbance (Munshower 1994). Care in selecting the proper species that compliment site soil<br />
maturity is recommended. Also, the introduction of early successional species can direct changes in<br />
soil properties that would facilitate later successional species.<br />
58