Quantifying the relationship between soil seed bank and plant community assemblage in sites harboring the threatened Ivesia webberi in the western Great Basin Desert

Questions The soil seed bank is an important ecosystem component that can be pivotal for long-term persistence of many plant species, especially after disturbances followed by the invasion of alien weeds. However, many Great Basin Desert perennials produce relatively few viable seeds, while large areas of the Great Basin are currently invaded by alien weeds. This could result in dissimilarity in floristic composition between the above-ground vegetative community and the soil seed bank, causing abrupt plant community shifts following disturbance. Therefore, we asked what is the relationship in the floristic composition between the above-ground communities and the soil seed bank in sites where the threatened Ivesia webberi occurs? Location The Great Basin Desert, United States. Methods We used Dice-Sorensen's similarity index to estimate similarity between the standing vegetation and the soil seed bank. Redundancy analysis and variation partitioning were used to quantify the relationship between the total abundance of the sampled above-ground flora and the soil seed bank, accounting for effects of spatial processes and environmental variables describing climate, soils, and vegetation in the 10 sites. Results Findings reveal high dissimilarity in species assemblage and abundance between the above-ground plant communities and the soil seed bank. Most of the dominant native plant species sampled in the standing vegetation were absent in the soil seed bank, and the soil seed bank was dominated by invasive alien weeds. Conclusions Divergence in the floristic composition between the above-ground communities and the soil seed bank in Ivesia webberi habitat indicates low resilience and high risk of native species loss following perturbation. Post-disturbance succession in these plant communities may be largely dominated by invasive annual species; therefore, reduction of invasive species and native plant seeding may be necessary to sustain the ecological legacies of the desert ecosystem.