Grass invasion and drought interact to alter the diversity and structure of native plant communities

Understanding the interactive effects of species invasions and climate change is essential for predicting future shifts in biodiversity. Because multiple stressors can interact in synergistic or antagonistic ways, it is notoriously difficult to anticipate their combined effects on species assemblages. However, some hypotheses predict that plant invasions will become increasingly problematic as climate change improves conditions for invaders or lowers the biotic resistance of native communities. In a four-year field experiment, we quantified the individual and interactive effects of invasion by a globally problematic C4 grass, Imperata cylindrica, and chronic simulated drought imposed by rainout shelters on the whole plant communities of regenerating longleaf pine forest. Invasion both inhibited plant colonization and enhanced plot-level extinctions, resulting in a severe (60%) loss of plant diversity across all functional groups, including perennial grasses and forbs, annual forbs, and ...