Abstract: Aims Tropical and subtropical areas are hotspots for the distribution of artificial forests in our country. Clarifying the status and influential factors of plant biomass in typically mixed artificial forests in these areas is important. This can help to uncover the limiting factors for stand productivity and guide the management of artificial forests. Methods In this study, the conifer-broadleaf forest, being transformed from a Chinese fir plantation in Yunyong forestry station located in Foshan city, Guangdong province, was selected as the object. First, we compared the difference in biomass of each plant organ among tree species configuration models at the early recovery stage (8-16 year). Second, the shifts in soil physicochemical properties and community-level plant functional traits under changes in tree species configuration were characterized. Finally, we explored the relative contributions of tree species configuration, soil properties and plant leaf traits to plant biomass variations, and evaluated their influential pathways. Based on these analyses, we aimed to evaluate the key influential factor for plant biomass in artificial forests in south subtropical areas. Important findings Our results showed that the total plant biomass and biomass in each organ both differed significantly across tree species configuration models. Tree species configurations affected plant biomass mainly via regulating leaf functional traits and soil nutrients content. Moreover, the leaf functional traits had greater influence on foliage and branch biomass, while the variation in soil nutrients content was the main factor driving the changes in truck, roots and total biomass. More specifically, tree species configurations characterized by a higher ratio of leaf nitrogen : phosphorus (P) and a higher functional diversity also had greater biomass in plant communities. An increase in soil total P content significantly promoted the increase in plant biomass, while an excess in soil total potassium would suppress the growth in biomass. This study compared the relative effects of leaf functional traits and soil nutrients content on plant biomass in the typically mixed artificial stands in south subtropical forests, and explored the key influential factor for the biomass in total and in each organ. These results provided the theoretical bases for restoration, operation and management of the artificial forests in south subtropical areas.

Key words: stand biomass, conifer-broadleaf mixed, tree species configuration, functional traits, soil nutrients, vegetation restoration