Predicting plant establishment in dryland restoration relies on understanding how the environment restricts viable plant strategies. Functional traits mediate plant response to environmental filtering and restoration sites often have strong abiotic filters resulting from bare ground and degraded soil that hinder plant establishment. In summer of 2018, we planted perennial species with a range of functional trait values across a dryland region of Arizona and Utah to elucidate broad patterns of abiotic filtering. This experiment occurred at eight sites within the RestoreNet Biodiversity-Ecosystem Functioning experiment where temperature and precipitation are expected to drive patterns in plant community assembly. Baseline functional trait data include both above- and belowground measurements from each species grown in a greenhouse setting. After the first year of establishment, we compared the traits of all planted species (null distribution) to the traits of surviving species to determine if the environment is “filtering” out sub-optimal trait values in a predictable way across the region.
Results/Conclusions
Community-weighted trait values were significantly different from a null distribution for nearly all traits at all sites, indicating that there is strong environmental selection towards optimal trait values at the community level. We found that there was a similar functional strategy (low leaf dry matter content and low specific root length of fine roots) shared by species that failed, but that across successful species there was a broader range of functional strategies. Overall, successful plants tended to have higher leaf dry matter content than expected by chance, as well as higher specific root length and lower root dry matter content. Additional factors in restoration such as bare soil may select for certain traits in the first stage of succession – species with low survival in our study may be better suited for a next stage of restoration after initial colonization by other species with traits better suited for early succession. These results allow researchers and managers to understand what traits promote species survival and abundance, especially in post-disturbance early successional communities where restoration action may be needed.