Key Laboratory for Subtropical Mountain Ecology, College of Geographical Sciences, Fujian Normal University, Fuzhou, China.
Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada.
Glob Chang Biol. 2018 Mar;24(3):1308-1320. doi: 10.1111/gcb.13939. Epub 2017 Oct 30.
Controlled experiments have shown that global changes decouple the biogeochemical cycles of carbon (C), nitrogen (N), and phosphorus (P), resulting in shifting stoichiometry that lies at the core of ecosystem functioning. However, the response of soil stoichiometry to global changes in natural ecosystems with different soil depths, vegetation types, and climate gradients remains poorly understood. Based on 2,736 observations along soil profiles of 0-150 cm depth from 1955 to 2016, we evaluated the temporal changes in soil C-N-P stoichiometry across subtropical China, where soils are P-impoverished, with diverse vegetation, soil, and parent material types and a wide range of climate gradients. We found a significant overall increase in soil total C concentration and a decrease in soil total P concentration, resulting in increasing soil C:P and N:P ratios during the past 60 years across all soil depths. Although average soil N concentration did not change, soil C:N increased in topsoil while decreasing in deeper soil. The temporal trends in soil C-N-P stoichiometry differed among vegetation, soil, parent material types, and spatial climate variations, with significantly increased C:P and N:P ratios for evergreen broadleaf forest and highly weathered Ultisols, and more pronounced temporal changes in soil C:N, N:P, and C:P ratios at low elevations. Our sensitivity analysis suggests that the temporal changes in soil stoichiometry resulted from elevated N deposition, rising atmospheric CO concentration and regional warming. Our findings revealed that the responses of soil C-N-P and stoichiometry to long-term global changes have occurred across the whole soil depth in subtropical China and the magnitudes of the changes in soil stoichiometry are dependent on vegetation types, soil types, and spatial climate variations.
控制实验表明，全球变化使碳（C）、氮（N）和磷（P）的生物地球化学循环解耦，导致生态系统功能核心的化学计量比发生变化。然而，对于具有不同土壤深度、植被类型和气候梯度的自然生态系统中，土壤化学计量对全球变化的响应仍知之甚少。基于 1955 年至 2016 年从 0-150cm 深度的土壤剖面中获得的 2736 个观测值，我们评估了中国亚热带地区土壤 C-N-P 化学计量随时间的变化，该地区土壤磷贫化，植被、土壤和母质类型多样，气候梯度广泛。我们发现，在过去的 60 年中，所有土壤深度的土壤总 C 浓度显著增加，土壤总 P 浓度降低，导致土壤 C:P 和 N:P 比值增加。尽管平均土壤 N 浓度没有变化，但土壤 C:N 在表土中增加，而在深层土壤中减少。土壤 C-N-P 化学计量的时间趋势因植被、土壤、母质类型和空间气候变化而不同，其中常绿阔叶林和高度风化的赤红壤的 C:P 和 N:P 比值显著增加，而在低海拔地区土壤 C:N、N:P 和 C:P 比值的时间变化更为明显。我们的敏感性分析表明，土壤化学计量的时间变化是由氮沉降增加、大气 CO 浓度升高和区域变暖引起的。我们的研究结果表明，中国亚热带地区整个土壤深度的土壤 C-N-P 和化学计量对长期全球变化的响应已经发生，土壤化学计量的变化幅度取决于植被类型、土壤类型和空间气候变化。
