Wang Zhenghong, Liu Xiang, Zhou Wenjun, Sinclair Fergus, Shi Lingling, Xu Jianchu, Gui Heng
Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Centre for Mountain Futures (CMF), Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; Institute of Plant and Food Science, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Grassland Agro-Ecosystems, Institute of Innovation Ecology, Lanzhou University, Lanzhou 730000, China.
Sci Total Environ. 2022 Dec 15;852:158397. doi: 10.1016/j.scitotenv.2022.158397. Epub 2022 Aug 30.
Conversion of abandoned land (mainly savanna) into cropland generally occurs in fragile ecosystems such as dry-hot valleys (DHVs) in southwest China, with the intent of increasing land productivity and conducting ecological restoration. However, the effects of conversion on soil microbial communities and carbon turnover of savanna ecosystems remain unclear, since savannas could be a vital but overlooked carbon sink. To illustrate the ecological consequences of land-use change (LUC) for savanna ecosystems, a 1-year field experiment was conducted in DHVs of southwest China. The soil properties, microbial respiration, and metagenomics from two different land-use types (grassland and mango plantation) were examined to reveal the effects of regional LUC on soil C turnover and microbial traits. Conversion from degraded grassland into cropland increased the contribution of soil microclimate to the microbial community composition, reduced the constraints of soil water content (SWC), and further decreased nutrient availability. LUC reshaped the composition and structure of soil bacterial communities. Specifically, soil dominant microbes that belonged to Actinobacteria and Proteobacteria were significantly enriched by conversion, while rare microbes that belonged to a wider range of phyla were generally depleted, leading to an overall decrease in community diversity. In addition, LUC-induced changes in soil characteristics and microbial communities further decreased soil multifunctionality as well as the carbon use efficiency of microbes. Intensified microbial respiration and a significant increase in the soil CO efflux were observed following LUC, which could drive changes in soil microbial community composition and functions (such as growth and regeneration). In summary, through simultaneously reducing constraints on SWC and decreasing nutrient availability, conversion from degraded grassland to cropland in a DHV decreased soil microbial diversity and multifunctionality, and increased microbial respiration and soil CO efflux. Our study provides new insights for understanding the role and mechanisms of LUC in soil carbon turnover in ecologically fragile areas such as DHVs.
在中国西南部的干热河谷（DHV）等脆弱生态系统中，废弃土地（主要是稀树草原）向农田的转化普遍发生，目的是提高土地生产力并进行生态恢复。然而，由于稀树草原可能是一个重要但被忽视的碳汇，这种转化对稀树草原生态系统土壤微生物群落和碳周转的影响仍不清楚。为了阐明土地利用变化（LUC）对稀树草原生态系统的生态后果，在中国西南部的干热河谷进行了为期1年的田间试验。研究了两种不同土地利用类型（草地和芒果种植园）的土壤性质、微生物呼吸和宏基因组学，以揭示区域土地利用变化对土壤碳周转和微生物特性的影响。从退化草地转变为农田增加了土壤小气候对微生物群落组成的贡献，减少了土壤含水量（SWC）的限制，并进一步降低了养分有效性。土地利用变化重塑了土壤细菌群落的组成和结构。具体而言，属于放线菌和变形菌门的土壤优势微生物通过转化显著富集，而属于更广泛门类的稀有微生物普遍减少，导致群落多样性总体下降。此外，土地利用变化引起的土壤特性和微生物群落变化进一步降低了土壤多功能性以及微生物的碳利用效率。土地利用变化后观察到微生物呼吸增强和土壤CO₂通量显著增加，这可能推动土壤微生物群落组成和功能的变化（如生长和再生）。总之，通过同时减少对土壤含水量的限制和降低养分有效性，干热河谷中从退化草地向农田的转化降低了土壤微生物多样性和多功能性，并增加了微生物呼吸和土壤CO₂通量。我们的研究为理解土地利用变化在干热河谷等生态脆弱地区土壤碳周转中的作用和机制提供了新的见解。
