Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; Jixian National Forest Ecosystem Observation and Research Station, CNERN, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China.
Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; Jixian National Forest Ecosystem Observation and Research Station, CNERN, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China.
Sci Total Environ. 2022 Mar 25;814:152687. doi: 10.1016/j.scitotenv.2021.152687. Epub 2021 Dec 30.
The grasslands of the Tibetan Plateau store approximately 2.5% of global soil organic carbon (SOC) and considerable soil inorganic carbon (SIC) and have the potential to become a vast carbon source or sink as climate change progresses. However, the soil carbon (C) sequestration mechanisms that occur across large-scale natural gradients remain unclear. Here, humic substances (HS) were utilized to trace soil C turnover at 0-20 cm, and we compared divergences among three main grassland types (alpine meadow, alpine steppe, and artificial plantation) using structural equation modeling (SEM). The results showed that the alpine meadows sequestered the most soil C (63.99 ± 4.41 g kg SOC and 4.11 ± 0.63 g kg SIC), sequestering 2-3 times more than the alpine steppe ecosystems (19.78 ± 1.98 g kg SOC and 9.21 ± 0.66 g kg SIC). The alpine steppe and artificial plantation regions have strong C sink potential due to their low C/N ratios (P < 0.05). Importantly, SIC played an important role in the alpine steppes, accounting for nearly 26-37% of soil C. The ratios of recalcitrant HS to SOC were estimated as 46.50%, 65.09%, and 78.17% in the alpine meadow, alpine steppe, and artificial plantation ecosystems, respectively, indicating that SOC in the alpine meadow was the most sensitive to climate change. Fulvic acid (FA) accounted for 50.86% of SOC in the 0-20-cm interval, contributing most to the formation of SOC in all vegetation types. In addition, in contrast to climatic controls on soil C turnover in the alpine meadow, climate conditions rarely controlled C turnover in the alpine steppe. Moreover, sand and silt were the main soil minerals involved in C turnover in alpine meadow and alpine steppe ecosystems, respectively. Our study improves understanding of the mechanism by which soil C sinks form on the Tibetan Plateau under warming and wetting conditions.
青藏高原的草原储存了大约全球土壤有机碳 (SOC) 的 2.5%和大量的土壤无机碳 (SIC)，随着气候变化的发展，它们有可能成为巨大的碳源或碳汇。然而，在大尺度自然梯度上发生的土壤碳 (C) 固存机制尚不清楚。在这里，我们利用腐殖质 (HS) 来追踪 0-20 cm 土壤的 C 周转，并用结构方程模型 (SEM) 比较了三种主要草地类型（高山草甸、高山草原和人工林）之间的差异。结果表明，高山草甸固存了最多的土壤 C（SOC 为 63.99 ± 4.41 g kg，SIC 为 4.11 ± 0.63 g kg），是高山草原生态系统的 2-3 倍（SOC 为 19.78 ± 1.98 g kg，SIC 为 9.21 ± 0.66 g kg）。由于其低 C/N 比（P < 0.05），高山草原和人工林地区具有很强的碳汇潜力。重要的是，SIC 在高山草原中起着重要作用，占土壤 C 的近 26-37%。在高山草甸、高山草原和人工林生态系统中，难降解 HS 与 SOC 的比值分别估计为 46.50%、65.09%和 78.17%，表明高山草甸的 SOC 对气候变化最敏感。在 0-20 cm 范围内，富里酸 (FA) 占 SOC 的 50.86%，对所有植被类型 SOC 的形成贡献最大。此外，与高山草甸土壤 C 周转受气候控制不同，气候条件很少控制高山草原的 C 周转。此外，在高山草甸和高山草原生态系统中，沙子和粉砂分别是土壤 C 周转的主要土壤矿物。我们的研究提高了对青藏高原在变暖增湿条件下土壤碳汇形成机制的理解。
