Forest Type Impacts Productivity in Karst Forests More Than Soil Nutrient Stocks and Multi‐Trophic Biodiversity

ABSTRACT Current research has confirmed that forest productivity in non‐karst regions is closely related to biodiversity. However, the relationship between forest productivity and multi‐trophic biodiversity remains unclear in karst habitats, characterized by thin soil layers and limited soil nutrients. To better understand the productivity of natural and planted forests in karst regions and main impact factors on the forest productivity, we selected restored karst forests in the southwest of China. By using methods such as high‐throughput sequencing, the Mantel test, random forest model, and structural equation model, we analyzed the differences in productivity, habitat factors, and multi‐trophic biodiversity between natural forests and planted forests and explored the key influencing factors for productivity of karst forests. The findings indicated that the aboveground, belowground, and total productivity of planted forests were significantly higher than those of natural forests. Conversely, the soil nutrient stocks, multi‐trophic biodiversity, and plant diversity of natural forests were significantly higher than those of planted forests. Moreover, the complexity of the multi‐trophic co‐occurrence network in planted forests was higher than that in natural forests. The Mantel test revealed significant positive correlations between soil nutrient stocks, soil moisture content, altitude, slope position, soil layer thickness, multi‐trophic biodiversity, and forest aboveground productivity, belowground productivity, and total productivity. The random forest model identified soil nutrient stocks as the most significant factor influencing the karst forest productivity. The structural equation model showed that stand characteristics, soil nutrient stocks, and multi‐trophic biodiversity collectively explained 69% of the total productivity variation. Forest type could not only directly impact the total productivity but also affect the total productivity along with the changes in soil nutrient stocks. This study is conducive to a deeper understanding of the formation mechanism of productivity in Southwest karst forests.