Forest Productivity Enhancement Over the Past Two Decades Is Associated With Plant–Microbial Interactions

Improving forest productivity is a key natural strategy for mitigating climate warming; however, the role of soil microbiomes in large-scale temporal trends in forest productivity has been largely overlooked. Here, we conducted a national-scale survey across China's forests to explore spatial variation in the temporal trend in forest productivity over the past two decades (2001-2023) and its covariation with soil microbiomes. The forest productivity in China (72 sites) showed an increasing trend over the past two decades, especially in temperate forests with high soil phosphorus availability. Moreover, our random forest analysis revealed that soil microbial traits were the most important factors that correlated with the temporal trend in forest productivity. Specifically, the enhancement of forest productivity was positively associated with high microbial diversity, abundant plant growth-promoting microbial genes, stronger mycorrhizal associations, and a microbial life history strategy of high yield, whether or not climates, soil properties, soil nutrients, forest age, and global change factors were controlled. Overall, our findings suggest that long-term co-adaptation between plants and microbes is likely to enhance forest productivity, which may provide a negative feedback to climate change by promoting forest carbon sinks.