Ren Zhuobing, Li Changjia, Fu Bojie, Zhou Wenxin, Chen Xinli, Wang Shuai, Stringer Lindsay C
State Key Laboratory of Earth Surface Processes and Disaster Risk Reduction (ESPDRR), Faculty of Geographical Science, Beijing Normal University, Beijing, China.
Faculty of Geographical Science, Institute of Land Surface System and Sustainable Development, Beijing Normal University, Beijing, China.
Glob Chang Biol. 2025 Aug;31(8):e70427. doi: 10.1111/gcb.70427.
Growing concerns about the accelerating global changes in drylands have intensified interest in understanding the impacts of diverse environmental factors on various soil carbon components, particularly their potential threshold effects, which may lead to abrupt nonlinear changes in both the quantity and composition of soil carbon. However, most research has predominantly focused on identifying key environmental drivers of either organic or inorganic carbon separately, often neglecting the presence and range of multiple critical thresholds. This study addresses this gap by analyzing extensive field data, including soil carbon measurements and ecosystem variables, collected across a ~4000 km transect in China's drylands. Utilizing a gradient forest model combined with threshold analyses, we assess the impacts of key drivers, including sand content, total nitrogen, aridity, and cation exchange capacity, on soil carbon pools. Our findings indicate that nitrogen content is the most influential factor for soil organic carbon, which was sensitive to low levels of nitrogen (0.07%-0.08%), with a slower response observed at higher levels. Aridity significantly affects both organic and inorganic carbon pools, with identified threshold zones for organic carbon at aridity levels of 0.48-0.52 and 0.75-0.85, and for inorganic carbon at 0.82-0.88. Threshold zones of sand content for total carbon are identified at lower levels and a wider range (51.4%-64.1% and 87.3%-88.1%), due to its negative effects on both organic and inorganic carbon, impacting 20% of the dryland area. Spatial variations in threshold effects revealed a trade-off between nitrogen and pH in regulating soil total carbon. The combined threshold effects of climate warming and aridification may pose a greater threat to soil organic carbon in high-latitude regions. This research enhances understanding of soil carbon dynamics in arid environments and offers novel approaches and insights for identifying thresholds in ecosystems that are increasingly at risk of reaching tipping points.
对旱地全球变化加速的日益担忧，增强了人们对理解多种环境因素对各种土壤碳组分影响的兴趣，特别是其潜在的阈值效应，这可能导致土壤碳的数量和组成发生突然的非线性变化。然而，大多数研究主要集中在分别确定有机碳或无机碳的关键环境驱动因素，常常忽略了多个临界阈值的存在和范围。本研究通过分析在中国旱地约4000公里样带上收集的大量实地数据来填补这一空白，这些数据包括土壤碳测量和生态系统变量。利用梯度森林模型结合阈值分析，我们评估了包括砂含量、总氮、干旱度和阳离子交换容量在内的关键驱动因素对土壤碳库的影响。我们的研究结果表明，氮含量是土壤有机碳最具影响力的因素，土壤有机碳对低水平氮（0.07%-0.08%）敏感，在较高水平时响应较慢。干旱度显著影响有机碳库和无机碳库，确定的有机碳阈值区干旱度水平为0.48-0.52和0.75-0.85，无机碳阈值区为0.82-0.88。由于砂含量对有机碳和无机碳均有负面影响，影响了20%的旱地面积，因此确定了总碳砂含量的阈值区在较低水平且范围更广（51.4%-64.1%和87.3%-88.1%）。阈值效应的空间变化揭示了氮和pH值在调节土壤总碳方面的权衡。气候变暖和干旱化的综合阈值效应可能对高纬度地区的土壤有机碳构成更大威胁。这项研究增进了对干旱环境中土壤碳动态的理解，并为识别日益面临达到临界点风险的生态系统中的阈值提供了新方法和见解。
