Effects of stand structure and soil nutrient status on tree growth and forest production: evidence from a forest management experiment in a mixed oak forest

Forest management aims to improve the growing conditions of trees to ensure the sustainable utilization of forest resources. This study compares the effects of different forest management practices on tree growth, forest production, stand structure, and soil nutrient status. We selected a mixed oak forest in the western part of the Qinling Mountains range in China and implemented three forest management practices: target tree forest management (TTFM), structure-based forest management (SBFM), and secondary forest comprehensive silviculture (SFCS). As expected, all three management practices significantly reduce stand mortality rate compared to the unmanaged plots. And these three management practices mainly influenced biomass by affecting soil available potassium, basal area by adjusting tree species diversity, and stand mortality rate by varying spatial structure and tree size diversity. Stand structure and soil nutrient status explained 63.1% and 36.5% of the variation in tree growth and forest production, respectively. Spatial structure, tree size diversity, and tree species diversity explained 34.5%, 26.6%, and 26.6% of the variation in tree growth and forest production, respectively. The results show that managed plots, especially the SBFM, had a positive impact on tree growth and forest production compared with the unmanaged plots. Furthermore, compared to soil nutrient status, stand structure, especially spatial structure, plays a more significant role in tree growth and forest production.