Rodents, Ungulates, and Water, oh my! A Story of Community Assembly in the Soil Seed Bank

Many plant species store viable seeds in the soil, forming a seed bank that facilitates community level resilience and awaits suitable germination conditions. Seed banks can inform our understanding of community assembly, and ultimately restoration potential, through abiotic and biotic filters. Via experimental manipulation, we assessed the effects of two biotic filters (ungulate and rodent presence and absence) , and an abiotic filter (water amount) on soil seed bank species. As important drivers of community assembly, for our biotic filters, ungulates influence plant communities through selective grazing and rodents influence plant communities through seed predation. For our abiotic filter, water availability influences seedling emergence, recruitment, and survival. These filters are found across nearly every restoration project and their influence impacts restoration outcomes. Our study is in a temperate grassland in Western Montana, USA , and had five geographically different sites each with paired ungulate, rodent, and watering treatments installed in the summer of 2020 and watering treatments starting the following growing season of 2021. While site-level soil seed bank density and diversity variability existed, a high density of forbs related to different filters were observed in the soil seed bank that were not reflected in the aboveground plant community. Our results illustrate which filters are influencing the species that are present in the seed bank to inform future seed-based restoration actions and native seed mixes. This study contributes knowledge that can help land managers optimize the use of soil seed banks in restoration efforts.