Drought and shrub cover differentially affect seed bank composition within two sagebrush steppe communities

Soil seed banks are critical biodiversity repositories for dryland plant communities. Understanding how environmental factors alter seed bank composition provides valuable information on ecological processes within a community and can be useful for creating land management strategies. We assessed seed bank response to drought and microsite within an Artemisia arbuscula dominated community and a directly adjacent (similar to 60m apart) A. cana dominated community, and characterized the similarity between these two seed banks and the corresponding aboveground vegetation. We found that drought increased exotic grass seed density and decreased seed species diversity and evenness within the A. arbuscula community, whereas shrub microsites enhanced seed species diversity and native forb seed density. In contrast, there were only minor drought effects within the A. cana community. Within both plant communities, there was low similarity between the seed bank and existing vegetation (<28%), and both seed banks were comprised of over 50% exotic annual grass seeds. Our study suggests that seed banks of drylands similar to A. arbuscula dominated plant communities (with heterogenous landscapes and low soil moisture availability) may experience more drought induced impacts than adjacent sagebrush communities, and highlights the role of shrub canopies as beneficial microsites for seeds in some drylands.

Automated summary

Soil seed banks are important biodiversity resources for dryland plant communities. The response of seed banks to environmental factors provides valuable information on ecological processes and can be used for land management strategies.