He Mei, Fang Kai, Tang Meng, Feng Xuehui, Qin Shuqi, Chen Leiyi, Yang Yuanhe
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
China National Botanical Garden, Beijing, 100093, China.
Sci China Life Sci. 2025 May 8. doi: 10.1007/s11427-024-2898-x.
Subsoils hold a substantial reservoir of organic carbon (C), and its dynamics can be greatly influenced by fresh C inputs through priming effect, potentially altering the magnitude of soil C-climate feedback. Despite the importance of soil C dynamics in regulating this feedback, our understanding of how soil C release and the priming effect vary along the soil profile remains limited, especially in alpine grasslands on the Tibetan Plateau. In particular, the relative importance of abiotic and biotic factors, such as soil physicochemical properties, aggregate and mineral protection, substrate quantity and quality, and plant and microbial properties (e.g., microbial biomass and diversity), in mediating vertical variations in soil C release and the priming effect is still unclear. Using 1-meter-deep soil profiles from five sites on the plateau, our C isotope labeling incubation experiments revealed a significant decline in both C release and the priming effect with increasing soil depth. We found that variations in soil C release along the profile were primarily influenced by soil properties (soil moisture and pH), mineral protection (the molar ratios of amorphous Fe/Al oxides to soil organic C (SOC) and soil mineral specific surface area), and hydrolase activity. In addition, vertical variations in the priming effect were dominantly affected by soil properties (soil moisture and pH), mineral and aggregate protection (the molar ratio of exchangeable Ca to SOC and the proportion of C occluded in clay+silt fractions), and microbial properties (oxidase activity and the copy number of bacterial ribosomal RNA gene operons). These findings provide valuable insights into the complex soil C cycling across profiles and its feedback to climate change.
土壤下层储存着大量的有机碳（C），其动态变化可能会受到通过激发效应输入的新鲜碳的显著影响，这有可能改变土壤碳 - 气候反馈的强度。尽管土壤碳动态在调节这种反馈方面很重要，但我们对土壤碳释放和激发效应如何沿土壤剖面变化的理解仍然有限，特别是在青藏高原的高寒草原地区。具体而言，非生物和生物因素，如土壤理化性质、团聚体和矿物保护、底物数量和质量以及植物和微生物特性（如微生物生物量和多样性），在介导土壤碳释放和激发效应的垂直变化中的相对重要性仍不明确。利用来自高原五个地点的1米深土壤剖面，我们的碳同位素标记培养实验表明，随着土壤深度增加，碳释放和激发效应均显著下降。我们发现，沿剖面的土壤碳释放变化主要受土壤性质（土壤湿度和pH值）、矿物保护（无定形铁/铝氧化物与土壤有机碳（SOC）的摩尔比以及土壤矿物比表面积）和水解酶活性的影响。此外，激发效应的垂直变化主要受土壤性质（土壤湿度和pH值）、矿物和团聚体保护（可交换钙与SOC的摩尔比以及粘土+粉砂级分中碳的闭蓄比例）和微生物特性（氧化酶活性和细菌核糖体RNA基因操纵子的拷贝数）的影响。这些发现为跨剖面的复杂土壤碳循环及其对气候变化的反馈提供了有价值的见解。
