Influence of Aboveground Vegetation on Seed Bank Composition and Distribution in a Great Basin Desert Sagebrush Community

The quantity, composition, and spatial dispersion of seed banks can greatly affect community dynamics. While seed banks of hot deserts have been studied extensively, little is known about seed banks in cold deserts, in particular the relationship between the seed bank and the aboveground vegetation. We investigated the relationship between the seed bank and aboveground vegetation and the effect of microhabitat (shrub interspace or beneath shrub) and aboveground community phase (high or low perennial bunchgrass cover) on the seed bank of a Great Basin Desert sagebrush community. The seed bank and aboveground vegetation differed in their most dominant species, resulting in moderately dissimilar species compositions as determined by Sørensen\u27s similarity index and Bray–Curtis distance. In contrast, comparing the seed bank species composition to the aboveground vegetation structure (functional groups) using non-metric multidimensional scaling (NMDS) revealed a correspondence between the two communities. Shrub seed densities were higher beneath shrubs. Neither microhabitat nor community phase explained variation in total seed density or species richness. Therefore, our measures of the aboveground vegetation did not influence seed density across functional groups or species richness, and the similarity between the seed bank and aboveground vegetation varied depending on the aboveground organizational level used in comparisons

Seed Pool Dynamics of a Great Basin Sagebrush Community in the Context of Restoration

Restoration of Great Basin sagebrush communities is often attempted without understanding the potential impacts of either restoration treatments on the seed pool or the seed pool on restoration efforts. In addition, few studies have examined seed pools of the Great Basin and the role of vegetation in structuring seed pool communities. I evaluated soil seed pool dynamics of a Great Basin sagebrush community in a restoration context. In Chapter 1, I determined the relationship between the compositions of the seed pool and aboveground vegetation and the effect of shrubs (microhabitat effects) and perennial bunchgrass cover (community phase effects) on the seed pool community composition, seed density, and seed pool species richness. To evaluate the relationship between the two communities and the effects of microhabitat and community phase, the aboveground vegetation and the soil seed pools of different community phases and microhabitats were sampled prior to restoration. Similarity and distance metrics and non-metric multidimensional scaling (NMDS) were used to asses the relationship between the two communities. NMDS and analysis of variance (ANOVA) were used to determine the effects of aboveground community phase and microhabitat on the seed pool community. Results suggest that the relationship between the aboveground vegetation and seed pool community compositions varied according to the organizational level used for vegetation. In addition, microhabitat and community phase did influence seed density but not species richness. I sought to evaluate the effects of restoration treatments on the seed pool community in Chapter 3. To assess the impacts of restoration treatments, the seed pool community before and after treatments was censused. NMDS of the seed pool community and ANOVA on dominant species of the seed pool were performed to determine treatment effects. Results from this research suggest seed pool community composition and seed density varied temporally and spatially. Tebuthiuron and Plateau may have altered community composition whereas prescribed burn affected seed density. This research is applicable for land managers by helping determine the most effective restoration treatment, which will include effects on the seed pool