Influence of light and soil moisture on Sierran mixed-conifer understory communities

摘要: Sierra Nevada forests have high understory species richness yet we do not know which site factors influence herb and shrub distribution or abundance. We examined the of an old-growth mixed-conifer Sierran forest its in relation to microsite conditions. The has (98 sampled), most are herbs with sparse cover relatively equal Shrub is highly concentrated discrete patches. Using overstory tree environmental conditions, four habitats were identified; cluster, partial canopy, gap, rock/shallow soil. Herb strongly linked habitats. Soil moisture, litter depth diffuse light significant gradients influencing plant distribution. was influenced by soil moisture. associated more light, less direct sites lower affected conditions Richness positively correlated depth, negatively cover. Disturbance management practices change floor shallow moisture likely strongest effect on abundance richness.