CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of, Biology, Chinese Academy of Sciences, Chengdu 610041, China; Zoige Peatland and Global Change Research Station, Chinese Academy of Sciences, Hongyuan 624400, China.
CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of, Biology, Chinese Academy of Sciences, Chengdu 610041, China; CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China.
Sci Total Environ. 2022 Nov 20;848:157539. doi: 10.1016/j.scitotenv.2022.157539. Epub 2022 Jul 29.
Peatlands are vital soil carbon sinks, yet this function is jeopardized by plant carbon which could change the decomposition rate of soil organic carbon, knowing as "priming effect". How the priming effect depends on depth is a critical question in drained peatland given the heterogeneity of soil layers defined by the water table, which include the surface acrotelm, inter-mesotelm and deep catotelm. Here, through incubation, we quantified the response of these three soil layers to addition of C-labeled oxalate, glucose, cellulose, or cinnamic acid under anoxic or oxic conditions on the Zoige Plateau in Tibet. Soil carbon in the inter-mesotelm showed the greatest decomposition, with the highest humification index and lowest microbial biomass carbon, while the soil carbon at the surface acrotelm was least decomposed. Under anoxic conditions, exogenous carbon addition reduced CO emission by 12.2% at the surface acrotelm but increased by 59.8% in the inter-mesotelm and 23.5% in the deep catotelm. In the inter-mesotelm, oxalate addition significantly increased CO emission by 63.9%, while cinnamic acid significantly increased it by 92.9%. In the deep catotelm, cinnamic acid significantly increased CO emission by 55.3%. These results suggested that deeper soil organic carbon was more sensitive to plant carbon, particularly complex or recalcitrant carbon, than surface acrotelm soil. Under oxic conditions, carbon addition increased surface soil CO emission by 18.9%, and triggered even greater increase at inter-mesotelm and deep catotelm soil, with proportions of 48.3% and 32.0%, respectively. Under both conditions, peat profile CO release increased by 17.2-31.4% after exogenous carbon addition, and more than 77.8% of the increase came from the deeper two layers. These findings highlighted the need to take full account of priming effect of deeper soil in order to assess and predict the stability of carbon stocks in drained peatland.
泥炭地是重要的土壤碳汇，但植物碳会危及这一功能，因为它可能改变土壤有机碳的分解速率，这种现象被称为“激发效应”。鉴于水位定义的土壤层具有异质性，包括表层腐殖质层、中层中间层和深层腐殖质层，了解激发效应对深度的依赖关系是排水泥炭地中的一个关键问题。在这里，我们通过培养，在青藏高原的佐格高原上，在缺氧或有氧条件下，定量研究了这三个土壤层对添加 C 标记草酸盐、葡萄糖、纤维素或肉桂酸的反应。在缺氧条件下，表层腐殖质层中添加外源碳减少了 12.2%的 CO 排放，但中层中间层增加了 59.8%，深层腐殖质层增加了 23.5%。在中层中间层，草酸盐的添加显著增加了 63.9%的 CO 排放，而肉桂酸则显著增加了 92.9%。在深层腐殖质层中，肉桂酸显著增加了 55.3%的 CO 排放。这些结果表明，与表层腐殖质层土壤相比，更深层的土壤有机碳对植物碳，特别是复杂或难分解的碳更敏感。在有氧条件下，添加碳增加了表层土壤的 CO 排放，中层中间层和深层腐殖质层的 CO 排放也增加了更多，分别为 48.3%和 32.0%。在这两种情况下，添加外源碳后，泥炭剖面的 CO 释放增加了 17.2-31.4%，增加的部分有超过 77.8%来自更深的两层。这些发现强调，为了评估和预测排水泥炭地中碳储量的稳定性，需要充分考虑深层土壤的激发效应。
