RELATIONSHIPS OF OVERSTORY TO UNDERSTORY COVER VARIABLES IN A PONDEROSA PINE GAMBEL OAK ECOSYSTEM

Many studies have indicated relationships between individual species, but none have related combinations of overstory variables to understor y herbaceous vegetation in a Ponderosa pine/Gambel oak ecosystem. Our objective was to determine not only the general relationships between the two sets of variables, but also identify the highest contributing variables. We used canonical correlation analysis to relate overstory variables (canopy cover, basal cover and density) to herbaceous vegeta tion cover variables. Canopy, basal, and ground cover were measured by the line intercept method using a 12.2 m tape as a sample unit. Tree density was measured by the Point-Center-Quarter method. The analysis was made with selected overstory variables and 5 understory herbaceous cover variables. This analysis revealed a significant canonical corre lation between the two canonical variables (r = 0.69). The analysis sh owed that among herbaceous cover variables, Oregon grape, Kentucky blu egrass, sedge, and foxtail barley; and among overstory variables, the density and the basal cover of Ponderosa pine indicated the highest po sitive contribution to the correlation of the two linear combinations while the density and canopy of Gambel oak negatively affected the can onical correlation.