|HOOPES, CARLA - Montana State University|
Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2009
Publication Date: 6/1/2009
Citation: Sheley, R.L., Vasquez, E.A. 2009. Functional Group Responses to Reciprocal Plant Litter Exchanges between Native and Invasive Plant Dominated Grasslands. Journal of Invasive Plant Science and Management. 2:158-165.
Interpretive Summary: Enduring invasive plant management will require that managers modify the ecological processes that direct successional dynamics and invasion. Plant litter affects many of those processes and managing litter could provide many practical ways of directing plant communities toward those that are desired. To the limits of our knowledge litter amount, the type of litter, and the size of the litter fragments and their associated processes can be modified to achieve land use objectives. In this study, we found that low amounts of native plant litter doubled native grass biomass in areas where St. Johnswort dominated. Native forbs were also favored with specific levels of litter. In the future, it may be possible to use management tools, such as fire, grazing, and mowing to alter litter amount, type, and size of fragments to facilitate plant community dynamics away from invasive species and toward native plant communities.
Technical Abstract: Manipulating litter in an attempt to direct successional trajectories is rarely considered as a management strategy. Our objective was to determine the influence of litter collected from an intact native plant community on a community dominated by an invasive species within the same habitat type as well as the influence of litter collected from a community dominated by an invasive species on an intact native plant community. We hypothesized that litter amount, type (source), and fragment size would influence various functional groups within a native plant community differently than within a weed dominated plant community. Treatments were 2 litter types (native, weedy), 2 litter amounts (454 and 908 g/m2), and 2 sizes of litter fragments (fine, coarse). We used reciprocal plant litter exchanges between native and invasive plant dominated grasslands to gain an initial understanding of litter’s influence on the density and biomass of native grasses, native forbs, St. Johnswort, and cheatgrass. Litter addition treatments were structured factorially and a no-litter treatment was included as a control. Treatments were replicated 4 times and placed in a randomized-complete-block design inside and outside an exclosure. St. Johnswort was not influenced by any treatment. Native grass density increased with application of low (454 g/m2) amounts of litter where the grasses were subordinate to St. Johnswort, and adding native plant litter to the weedy site nearly doubled native grass biomass. Low amounts of finely fragmented litter and high amounts of coarse litter induced native forbs to produce about twice the biomass as found in the non-litter amended controls. Our study suggests that plant litter may be a characteristic of vegetation that can be managed for to shift the plant community toward those that are desired.