Regeneration and Restoration — Abstract of Paper


Riparian Valley Oak (Quercus lobata) Forest Restoration on the Middle Sacramento River, California
F. Thomas Griggs¹ and Gregory H. Golet²


In 1989 The Nature Conservancy initiated a riparian horticultural restoration program on the floodplain of the middle Sacramento River, California. At nearly all restoration sites Valley oak (Quercus lobata Nee) comprised a major component of the planting design. Valley oaks are a keystone tree species of lowland floodplain habitats in California's Central Valley, contributing greatly to the structural and biological diversity of riparian forests in the region. Here we present preliminary comparisons of survival and structural development of oaks planted as acorns at six sites from 1990 to 1994. Our focus is on how the plants responded to natural site conditions following the cessation of maintenance activities (including irrigation and weed control). Initial comparisons demonstrate considerable variability among sites in survival and structural development (i.e., stem diameter, canopy cover, and dominance). Although we were able to ascribe some of this variability to known physical and biological differences in site conditions (e.g., soil type, herbivore pressure), furthering our understanding of factors that affect valley oaks on the Sacramento River floodplain will require additional study and more detailed assessments of site conditions.