Forest productivity, leaf area, and terrain in southern Appalachian deciduous forests

Leaf area index (LAI) is an important structural characteristic of forest e cosystems which has been shown to be strongly related to forest mass and en ergy cycles and forest productivity. LAI is more easily measured than fores t productivity, and so a strong relationship between LAI and productivity w ould be a valuable tool in forest management. While a linear relationship h as been observed between LAI and forest productivity, most of these data ha ve been collected in needle-leaved evergreen stands. The generality and con sistency of the relationship between LAI and productivity has not been as w ell established for deciduous forests. Leaf area index (LAI) and aboveground net primary production (ANPP) were me asured on 16 forest stands in the southern Appalachian Mountains. These sta nds span a range of elevation, slope position, temperature, and moisture re gimes. LAI averaged 5.8 m(2) m(-2) and ranged from 2.7 to 8.2. ANPP average d 9.2 Mg ha(-1) yr(-1) and ranged from 5.2 to 11.8 Mg ha(-1) yr(-1). LAI and ANPP decreased significantly from cove to ridge sites, and ANPP dec reases significantly from low to high elevation (P < 0.05, linear regressio n slope). Elevation-related differences in ANPP do not appear to be due to changes in precipitation, leaf nitrogen content, or site N mineralization r ates. Linear ANPP-LAI equations fit to the data measured in this study were signi ficant (P < 0.05). These relationships were not significantly different (P > 0.1) from linear relationships based on data reported in most other studi es of ANPP and LAI in eastern deciduous forests of North America. However, the slope of a linear regression model based on North American eastern deci duous forests was significantly different (P < 0.05) from one based on data collected in temperate deciduous forests for the rest of the globe. The di fferences were slight over the range of observed data, however, and the dif ference may be due to a narrower range of data for North American deciduous forests.