Leaf area-productivity relationships among mixed-species hardwood forest communities of the Central Hardwood region

Abstract

A study was conducted to quantify the influence of environmental factors on the leaf area-productivity relationships of Ecological Land Type Phases (ELTPs) representing Central Hardwood forest communities. Forest inventory data were collected from 83 plots taken along a moisture gradient, stratified within recognized ELTPs in the Hoosier National Forest in southern Indiana. Density (standing basal area, volume, and biomass), annual production, leaf area index (LAI), and water balance indices were determined for each ELTP. Ecological Land Type Phases showed marked differences in density and growth measures which were positively correlated with leaf area index. Leaf area index, in turn, exhibited strong correlations with site and environmental factors. Further, a reduction in canopy-average specific leaf area with decreasing soil moisture and LAI was observed. In general, maximum growth efficiency (measured as growth per unit of LAI) was attained at a LAI of approximately 3.5, after which it decreased. However, no significant differences in growth efficiency were found among ELTPs, suggesting that the communities were adjusting to differences in resource availability, particularly water. Thus, these mixed-species forest communities adjust both species composition and canopy morphology to compensate for changing environmental gradients.