Changes in climate are expected to alter native plant communities and influence their susceptibility to exotic plant invasions, with important ramifications for the services that these communities provide to humans (e.g., pollination, air purification, etc.). Yet how climate change will shift the balance and competition between plant species, including exotics and natives, is largely speculative. In this study, Forest Service scientists explored whether the outcomes of plant competition in response to simulated climate change could be predicted as a function of plant life-history strategies. Plant life-history theory predicts that “fast” species (those using high-resource uptake strategies to achieve rapid population growth) should outperform “slow” species (those using low-resource uptake and slow population growth strategies) under high resource conditions, but that slow species should win under low resource conditions. They competed spotted knapweed, a highly invasive exotic forb with a "fast" (hare) strategy that has taken over western United States grasslands, with the dominant native, a grass which exhibits a "slow" (tortoise) strategy.
1. The fast invader dominated under normal precipitation conditions.
2. The slow native won when precipitation declined.
3. While the research approach requires replication across more species, the findings suggest that life history theory may help predict which plant species, including exotics versus natives, will excel under future climate scenarios.
4. In plant communities where the natives are adapted to stressful conditions, climate-driven shifts toward more stressful conditions can favor natives over exotic plant invaders.