Ecological scale and forest development: squirrels, dietary fungi, and vascular plants in managed and unmanaged forests.

Abstract

Understanding ecological processes and their spatial scales is key to managing ecosystems for biodiversity, especially for species associated with late-seral forest. We focused on 2 species of squirrel (Sciuridae: northern flying squirrel, Glaucomys sabrinus, and Townsend's chipmunk, Tamias townsendii) in a crosssectional survey of managed and natural stands in southwestern Oregon during 1985-89. We measured vegetation and abundances of squirrels at >2,000 points in 19 stands in 3 seral stages. We described the diets of the squirrels in the stands. We analyzed data at point, stand, and stage scales to identify key processes contributing to biodiversity and scales at which emergent properties (synergistic effects) appeared.

Four factors (crown-class differentiation, decadence, canopy stratification, and understory development) accounted for 63% of variance in vegetation structure. Decadence contributed to variation mostly in late seral forest. Within stands, most habitat variables were poorly correlated. Across stands many variables were highly correlated, suggesting forests developed emergent properties above the point level but at or below stand level (16 ha). Plant species composition was summarized by 21 vegetation site types. Stands had 7-19 site types arrayed in fine scale (point and groups of points 40 m apart). Site types were used to measure habitat breadth (within-stand heterogeneity resulting from disturbance and forest development). Vegetation structure varied on a 0.5 ha scale. Stand-level characteristics were more influential than nominal seral stage for a variety of organisms. Late-seral forests were more moist and complex with greater habitat breadth than 40-70-year-old managed stands.

Structural factors, moisture-temperature gradient values (MGV), and habitat breadth were used to describe the habitat space potentially available to squirrels. Correlations between squirrels and habitat variables within stands were low. Linear regressions explained

Citation

Carey, A.B.; Kershner, J.; Biswell, B.; Dominguez de Toledo, L.S. 1999. Ecological scale and forest development: squirrels, dietary fungi, and vascular plants in managed and unmanaged forests. Wildlife Monographs. 142: 1-71