As novel climates arise in the following century, understanding the climate tolerance of a landscape is critical to ecosystem conservation. Over the last 20,000 years, North American plant biomes persist for a median of 230-460 years before transitioning to a new biome. Landscape resilience, calculated as biome residence and recovery times, changes across time and space, driven by biodiversity, rate of temperature change, and human activity. However, one of the most important variables that leads to different levels of landscape resilience, is the biome present at a site. To try to understand the mechanisms that lead to different patterns of landscape resilience, we examine the climate tolerance of 11 North American plant biomes over the past 20,000 years. We performed a meta-analysis of climate tolerance using 358 high-quality sediment cores that contain a total of 14,189 pollen samples from across the continent of North America. Climate tolerance measures the climate change that a biome can absorb before changing to another state. We analyzed the changing patterns of climate tolerance among landscape biome types and across time. We also explored the roles that biodiversity and the rate of climate change play on climate tolerance.
Results/Conclusions
We find not only that different biome types exhibit different climate tolerances, but that climate tolerances of an individual biome shift over time. Spruce parkland and mixed parkland have the broadest climate tolerance, while prairies have the narrowest climate tolerance. Species richness increases the climate tolerance of biomes. Climate tolerances were narrower before 12,000 years ago, when the climate changed abruptly, and increased as climate became stable. These changing patterns are consistent with landscape residence times, which were short during the deglaciation under abrupt climate change.
Our work demonstrates that biomes are not climatically static entities, as suggested by biome classification schemes, but rather their realized niches shift substantially over time. Thus, we should take care in using climate-based landscape classification schemes if we wish them to continue to be biologically relevant as climates change. Our work also implicates the importance of high biodiversity for promoting landscape resilience in conservation ecology. Abrupt climate change or substantial environmental disturbance may result in narrow climate tolerances and low landscape resilience. Because we observe changes in biome niches through time, we should understand the ecological niches over a long time scale and be wary of ecological niche models trained on modern climate alone.