Abstract: Plant distributions are strongly influenced by both climate and topography. In an analysis of geographic and topographic distributions for selected tree species in California, we found that tree populations are increasingly restricted to extreme topographic positions as they approach the edge of their geographic ranges, occupying cooler, pole‐facing slopes (at the warm and dry edge) and warmer, equator‐facing slopes (at the cool and moist edge). At a local scale, species distributions across topographic gradients also correlate with species geographic ranges (species that occupy cooler locations within the landscape have cooler, moister geographic distributions, and vice versa). Model outputs indicated that species found on pole‐facing slopes and equator‐facing slopes will experience population declines and population increases, respectively, in response to a warmer and drier future. As such, tree species occupying cooler landscape locations, which are viewed as refugia in some contexts, may be most threatened by anthropogenic climate change.
In a nutshell:
- Understanding how climate and topography influence plant and animal distributions has taken on a renewed urgency as the planet continues to warm in the 21st century
- Different locations on a landscape, such as pole‐ and equator‐facing slopes, create local microclimates with distinct plant communities
- Species that live in a cool location (eg a north‐facing slope, in the northern hemisphere) are often adapted to cooler climates and may be near the edge of their geographic range; this would make them especially vulnerable to a warmer and drier future climate
- Recognizing these patterns will prove important to identify “climate‐smart” conservation priorities and strategies