Haoru Yan, X H Liu, Bernhard Schmid, Yi Li, Kristina J. Anderson‐Teixeira, Sabine Both, Norman A. Bourg, David F. R. P. Burslem, Chengjin Chu, Keith Clay, Hu Du, Nathaly R. Guerrero‐Ramírez, Hua Huang, Daniel J. Johnson, Guangze Jin, Luxiang Lin, Feng Liu, Yankun Liu, William J. McShea, Xiangcheng Mi, Jonathan A. Myers, Jinyao Nie, Michael J. O'Brien, Richard P. Phillips, Xiujuan Qiao, Glen Reynolds, Guochun Shen, Marko J. Spasojevic, Hongxin Su, Shangwen Xia, Xuehong Xu, Yan Enrong, Xiaodong Yang, Jie Yang, Yan Zhu, Keping Ma, Yann Hautier
Soil organic carbon (SOC) plays an essential role in carbon sequestration and climate change mitigation in forest ecosystems. While experimental studies have shown that plant diversity usually increases SOC, it remains unclear whether this positive relationship holds in natural ecosystems across varying climatic conditions. Using a global dataset of 15 large and long-term monitored natural forest sites spanning a wide latitudinal range, we assess the relationship between tree diversity and SOC within and across sites in temperate, subtropical, and tropical regions. We found an overall positive relationship between tree taxonomic diversity and SOC. The relationships between tree taxonomic or functional diversity and SOC became stronger under colder and more arid conditions. Additionally, tree functional composition was linked to SOC only within a subset of sites in more arid climates. These findings suggest that warmer and more humid conditions increase decomposition, offsetting diversity-driven carbon inputs, while colder and more arid conditions enhance SOC through low decomposition and increased inputs through abiotic facilitation and biotic interactions in high-diversity communities. Our findings indicate that conserving plant diversity is critical for enhancing carbon sequestration and mitigating the effects of climatic conditions, particularly in cold climates and regions facing an increase in arid conditions.