Global climate change models predict an increase in precipitation patterns in desert ecosystems of the American Southwest, which might enhance the susceptibility of arid ecosystems to invasions by non-native exotic plants. Resource availability and habitat modification (i.e. disturbance) have been identified as possible underlying mechanisms for invasibility of plant communities. In the eastern Mojave Desert, habitat disturbance has increased due to increased human activities, and water availability is considered to be the main limiting resource for plant production. To elucidate the effects of soil disturbance and water on plant invasions, we created experimental patches that varied in levels of soil disturbance and resource availability (i.e. water) in a fully crossed factorial experiment, and documented responses of native and non-native winter annuals over two years.
Results/Conclusions
Our treatments had no effects on the density (seedlings m 2) of the non-native herb, Brassica tournefortii. However, water and soil disturbance positively influenced silique production. Density (seedlings m2) of the non-native Mediterranean grass (Schismus spp.) increased in watered and disturbed plots, and seedling density was associated with time in disturbed plots. In contrast, experimental manipulations influenced density (seedlings m2) of winter native annuals differently. Seedling density increased in watered plots and decreased in disturbed plots in 2009 but not in 2008. These results suggest that habitat invasibility may be species specific, and the establishment of native and non-native winter annual plants in arid systems can be influenced by the state of the habitat and by the level of resource availability which are expected to change due to climate change.
