LEAF AREA-PRODUCTIVITY RELATIONSHIPS AMONG MIXED-SPECIES HARDWOOD FOREST COMMUNITIES OF THE CENTRAL HARDWOOD REGION

A study was conducted to quantify-the influence of environmental facto rs on the leaf area-productivity relationships of Ecological Land Type Phases (ELTPs) representing Central Hardwood forest communities. Fore st inventory data were collected from 83 plots taken along a moisture gradient, stratified within recognized ELTPs in the Hoosier National F orest in southern Indiana. Density (standing basal area, volume, and b iomass), annual production, leaf area index (LAI), and water balance i ndices were determined for each ELTP. Ecological Land Type Phases show ed marked differences in density and growth measures which were positi vely correlated with leaf area index. Leaf area index, in turn, exhibi ted 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 approxima tely 3.5, after which it decreased. However, no significant difference s in growth efficiency were found among ELTPs, suggesting that the com munities were adjusting to differences in resource availability, parti cularly water. Thus, these mixed-species forest communities adjust bot h species composition and canopy morphology to compensate for changing environmental gradients.