Plant invasion influenced by spatial heterogeneity of soil nutrients

Background/Question/Methods

The increasing prevalence of invasive plant species threatens the function of ecosystems and the organisms that rely on those functions and resources. Hence, it is important for us to improve our understanding of the factors that influence invasibility. Recent development in invasion theory indicates that environmental heterogeneity plays a key role in plant invasions. Coexistence theory predicts heterogeneous environments should support more species than homogeneous ones because heterogeneous habitats have more variable patches which would allow more different species to coexist. These same attributes would also facilitate new opportunities for invading species. Consistent with this theory, we hypothesize that spatially heterogeneous habitats offer greater availability of variable patches thereby facilitating native species to coexist and for new species to invade. To test this, we manipulated the level of fine scale spatial heterogeneity of soil nutrients in a grassland community. Nutrient amendments were used to create treatments of differing levels of spatial heterogeneity and then invaded with two new species. Plant surveys were conducted to address two main questions: (1) How does fine scale spatial heterogeneity of soil nutrients influence plant invasion success? (2) How does changing fine scale spatial heterogeneity of soil nutrients affect plant community structure over time? 

Results/Conclusions

Preliminary results show that nutrient amendments in general increase species richness. Consistent with our prediction that heterogeneous environments will have greater number of species coexisting, we found evidence that the spatially heterogeneous treatment had greater species richness than our control treatments. Although we also predicted greater species diversity in heterogeneous treatments, our results suggest the spatial heterogeneity of soil nutrients had no clear affect on species diversity. While, our findings do not strictly follow the predictions of invasion and coexistence theory, our study indicates that spatial heterogeneity can have variable effects on community structure. This study will help us better understand the role that environmental heterogeneity plays in shaping our community structure.