Patterns of plant invasion along an environmental stress gradient
Tóm tắt
Do stressful environments facilitate plant invasion by providing refuges from intense above‐ground competition associated with productive areas, or prevent it by favouring locally adapted native species?
An invaded and fragmented oak savanna ecosystem structured along a landscape‐level stress gradient associated with soil depth, elevation, and canopy openness.
Vegetation and environmental data were collected from 184 plots in seven savanna remnants along the gradient. Using multivariate (CCA) and
46 of 119 species were naturalized exotics. CCA indicated the importance of environmental variation (mostly soil depth) for community structure but not for invasion; invasive species richness was similar in all areas. However, the abundance of invasives and their impacts on native diversity appear to increase significantly in less stressful habitats. Deeper soils had lower evenness and significantly fewer native species. This result was associated with dominance by exotic perennial grasses and large increases in vegetation height, suggesting strong above‐ground competition.
Low‐stress environments were not more invasible
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