Non-native grass invasion alters native plant composition in experimental communities |
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Authors: | S Luke Flory Keith Clay |
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Institution: | (1) Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA |
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Abstract: | Invasions of non-native species are considered to have significant impacts on native species, but few studies have quantified
the direct effects of invasions on native community structure and composition. Many studies on the effects of invasions fail
to distinguish between (1) differential responses of native and non-native species to environmental conditions, and (2) direct
impacts of invasions on native communities. In particular, invasions may alter community assembly following disturbance and
prevent recolonization of native species. To determine if invasions directly impact native communities, we established 32
experimental plots (27.5 m2) and seeded them with 12 native species. Then, we added seed of a non-native invasive grass (Microstegium vimineum) to half of the plots and compared native plant community responses between control and invaded plots. Invasion reduced native
biomass by 46, 64, and 58%, respectively, over three growing seasons. After the second year of the experiment, invaded plots
had 43% lower species richness and 38% lower diversity as calculated from the Shannon index. Nonmetric multidimensional scaling
ordination showed a significant divergence in composition between invaded and control plots. Further, there was a strong negative
relationship between invader and native plant biomass, signifying that native plants are more strongly suppressed in densely
invaded areas. Our results show that a non-native invasive plant inhibits native species establishment and growth following
disturbance and that native species do not gain competitive dominance after multiple growing seasons. Thus, plant invaders
can alter the structure of native plant communities and reduce the success of restoration efforts. |
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