Evaluation of potential versus realized site productivity of Larix principis-rupprechtii plantations across northern China

Abstract

Site quality evaluation is a fundamental component of forest management and is also vitally important towards improved understanding of forest growth processes and optimizing silviculture practices. However, most site quality studies have focused on site index which cannot predict potential site productivity. In this study, a methodology that incorporates volume-related potential increment which accounts for optimal stand density index was used for site productivity assessment of Larix principis-rupprechtii plantations across Northern China. Based on 152 permanent sample plots, the models of potential and realized productivity of L. principis-rupprechtii plantation were established, and percentage of available growing space close to potential productivity in different regions were analyzed in different site classes. Growth models of stand dominant height and volume were developed by site classes based on biological and statistical rationality. The potential productivity was between 3.93 m3/ha/year and 6.84 m3/ha/year. The realized productivity was always lower than potential productivity, and the gaps between the two types of productivity measures decreased with increasing stand age. The available growing space percentage of volume productivity was between 0% and 94.52%, and this was higher in stands in the middle and young stage of stand development compared to the mature stage. The available growing space increased with the decline of site class. The values of potential productivity and available growing space could be used to effectively assess forest site productivity, and also provide highly reliable and valuable information for L. principis-rupprechtii plantation management.