Site Evaluation Of Pine And Oak Mixed Forest In Qinling Mountains

Permanent and temporary inventory data, as well as stem analysis data, were collected from pine-oak stands in Qinling Mountains to evaluate site quality for secondary forests and plantation using site index, site form models and conversion equations. Dynamic of site quality was assessed with established models.Methods for formulating site index and site form tables, such as ratio method, standard deviation adjustment, and coefficient variation adjustment were applied by species. Homogeneity of variance test and analysis of variance were used for selecting stand factors influenced site form. Suitable site form conversion equations were validated by residual analysis. Site class, site index and site form were applied in site quality evaluation with 1958, 1990, 2005 and 2013 inventory data to analyze improving of site productivity. Limited values of DBH growth of various site index or site form, DBH growth before and after closing hillsides, data of stands productivity and soil properties from references were used in validating site quality change. Trend-surface was an approach to analysis stands succession. Results are:(1) Site form appears superior for secondary forests, while site index for plantation. In general, site index and site form were more accurate than site class in evaluating site quality.(2) Simultaneous equations are more accurate than liner regression equations in site form prediction of target specie.(3) Site class, site index, site form are uptrend form 1990 to 2000, and lower than 1958, significantly. Limited values of DBH growth reveal same tendency with site quality fluctuation. DBH growths after 1990 are higher than before, except for larch.