Regeneration and Restoration — Abstract of Paper


Soil Moisture Availability as a Factor Affecting Valley Oak (Quercus lobata Nee) Seedling Establishment and Survival in a Riparian Habitat, Cosumnes River Preserve, Sacramento County, California
Virginia C. Meyer¹


The lack of valley oak (Quercus lobata) regeneration throughout much of its historical range appears to be related to both habitat destruction and soil moisture availability. The water relations, growth and survival of greenhouse potted seedlings, field-planted and natural seedlings were monitored through the growing season, 1989. The age structure of the valley oak population of a riparian forest at the Cosumnes River Preserve was determined. The history of fluvial events of the Cosumnes River was ascertained to determine whether such fluvial events are associated with past seedling establishment within the forest. Natural and non-irrigated field-planted seedlings exhibited considerable water stress, little stem growth and leaf loss, while greenhouse potted and irrigated field-planted seedlings displayed limited water stress. Irrigated field-planted seedlings grew vigorously. Past seedling establishment within the forest showed a positive relationship with historical fluvial events. These studies suggest that soil moisture availability is fundamentally important for successful establishment of valley oak seedlings. Significant recruitment of valley oak seedlings may be limited to years in which plentiful soil moisture is available into the growing season, i.e. with the natural flooding of unconfined riparian systems.