Zhou Sha, Wang Jieying, Chen Lan, Wang Jun, Zhao Fazhu
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Northwest University, Xi'an, Shaanxi 710127, China; College of Urban and Environmental Sciences, Northwest University, Xi'an, Shaanxi 710127, China.
Shaanxi Key Laboratory of Earth Surface System and Environmental Carrying Capacity, Northwest University, Xi'an, Shaanxi 710127, China; College of Urban and Environmental Sciences, Northwest University, Xi'an, Shaanxi 710127, China; State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China.
Sci Total Environ. 2022 Jun 15;825:153925. doi: 10.1016/j.scitotenv.2022.153925. Epub 2022 Feb 23.
Afforestation substantially modifies native soil organic carbon (SOC) decomposition via plant carbon inputs (the priming effect), and in turn, triggers vital biogeochemical processes that influence the regulation of soil carbon dynamics. Soil microbes are crucial in regulating the direction and magnitude of the priming effect. In the present study, we performed metagenomic sequencing and C-glucose labeling analyses of microbial communities and priming effects across a Robinia pseudoacacia afforestation chronosequence (14-, 20-, 30-, and 45-year-old stands) in the Loess Plateau in China, with adjacent farmland being selected as a control. Our results revealed that the cumulative priming effect across five sites along the afforestation chronosequence initially increased and approached a peak value in the 20-year-old stand, after which it declined. The priming effect was predominantly driven by the microbial community structure (i.e., the fungal-to-bacterial ratios and relative abundances of Proteobacteria and Actinobacteria), and stable C decomposition genes and C-degrading enzymes. Specifically, among the key functional genes correlated with priming effect, which were identified in orders Rhizobiales and Pseudonocardiales, considerably promoted SOC priming. Overall, our findings indicate that afforestation alters soil microbial community structure and function, particularly with respect to enhancing stable soil C decomposition genes, which may promote SOC priming. The findings of the present study could enhance our understanding of fresh C input-induced changes associated with C mineralization in the context of the revegetation of ecologically fragile areas.
造林通过植物碳输入（激发效应）极大地改变了原生土壤有机碳（SOC）的分解，进而引发了影响土壤碳动态调节的重要生物地球化学过程。土壤微生物在调节激发效应的方向和强度方面至关重要。在本研究中，我们对中国黄土高原刺槐造林时间序列（14年、20年、30年和45年林龄的林分）中的微生物群落和激发效应进行了宏基因组测序和C-葡萄糖标记分析，并选择相邻农田作为对照。我们的结果表明，沿着造林时间序列的五个地点的累积激发效应最初增加，并在20年林龄的林分中接近峰值，之后下降。激发效应主要由微生物群落结构（即真菌与细菌的比例以及变形菌门和放线菌门的相对丰度）、稳定的碳分解基因和碳降解酶驱动。具体而言，在与激发效应相关的关键功能基因中，在根瘤菌目和假诺卡氏菌目中鉴定出的基因显著促进了SOC激发。总体而言，我们的研究结果表明，造林改变了土壤微生物群落结构和功能，特别是在增强稳定的土壤碳分解基因方面，这可能会促进SOC激发。本研究的结果可以增进我们对生态脆弱地区植被恢复背景下新鲜碳输入引起的与碳矿化相关变化的理解。
