The effects of stand structure on specific needle area in closed-canopy Chinese pine plantations

The specific leaf area (SLA) is an important variable reflecting the carbon gain strategy of tree growth, but the relationships between SLA and other environmental factors have not been studied extensively at the stand level. The aim of this study was to define the relationships between stand structure and SLA in order to improve the predictive value of SLA for forest management models. Various parameters of stand structure and specific needle area (SNA) were measured in 14 different even-aged and closed-canopy stands of Chinese pine (Pinus tabulaeformis Carr.). Correlation and regression analysis revealed several significant relationships between stand structure and SNA. Stand density exerted a significant effect on mean-canopy SNA (SNA(mean)). Stand density was also strongly correlated to mean-layer SNA (SNA(L)), especially at lower canopy layers. SNA(L) increased at lower canopy layers within each stand, and the increase was greater in higher density stands. Within the range of stand densities examined in this study, the SNA(mean) initially increased sharply with increasing stand density, but the rate of rise declined as the density increased. Finally, it reached stability when the stand density was above about 3,000 trees ha(-1).