Driving mechanisms of biomass mean annual increment in planted and natural forests in China

Deciphering the mechanisms driving biomass mean annual increment (MAI) in planted and natural forests subject to complex environmental constraints is useful for understanding carbon cycling in forest ecosystems. Based on a large-scale biomass growth dataset, this study used partial least squares path modeling to quantify the differential impacts of the coupling effects of climate, soil properties, site conditions, stand characteristics, and species richness on the MAI of planted and natural forests in China. The results showed that the degree of regulation of MAI by the stand and environmental factors was related to the specificity of forest origin. Increases in leaf area index, clay, and pH had a direct positive effect on MAI in natural and planted forests, while latitude had an indirect negative effect. In contrast, MAI in natural forests was indirectly negatively affected by increases in clay and pH, whereas MAI in planted forests was indirectly positively affected by them. Increases in temperature and precipitation had a positive effect on MAI in natural forests but an indirect negative effect on MAI in planted forests. Furthermore, MAI in natural forests was positively influenced by species richness, both directly and indirectly. We recommend deep plowing and fertilization to increase clay content and neutralize soil pH during intensive forest management practices and implementing multi-species silvicultural regulations to mitigate biodiversity loss and improve productivity.