Separating the contribution of habitat filtering and dispersal mechanisms in forming species distribution remains a challenge in community ecology. Despite the effect of environmental variables in structuring communities, only restricted numbers of them were considered as a habitat dissimilarity. In Chapter 2, I used topography and soil properties to define habitats within the Yosemite Forest Dynamics Plot (YFDP). The soil enzymes were added in soil samples due to their important role in releasing nutrients into the soil environment. The preference of eleven species to a specific habitat were examined. Also, the relative importance of habitat filtering and dispersal limitation were examined. I found that more species associated with habitats defined by soil properties compare to those associated with topographically defined habitat. In addition, the contribution of dispersal process was greater in explaining change in species composition. In Chapter 3, I studied the underlying processes in shaping four abundant species spatial arrangement in YFDP. I examined the effect of habitat heterogeneity, dispersal process, fire event, interaction of adults on juveniles, and negative density dependence (as a result of increasing density) in shaping species spatial distribution. My results suggest that dominant species spatial patterns are partially explained by topographic variables, dispersal limitation, biotic interactions, and fire history. Advisors/Committee Members: James A. Lutz, Bonnie Waring, Megan Nasto, ;.