College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, Ministry of Education, China Agricultural University, Beijing 100193, China.
Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia.
Sci Total Environ. 2022 Apr 10;816:151645. doi: 10.1016/j.scitotenv.2021.151645. Epub 2021 Nov 10.
Land-use changes may dramatically disturb underground microbial biodiversity, especially in the fragile ecological areas. However, the impact of conversion of grassland to cropland on soil nitrogen (N)-related microbial communities is not fully understood in the farming-pastoral ecotone of northern China. Therefore, 24 paired grassland and cropland soil samples were collected in this region to investigate the community structure and assembly processes of soil N-related microorganisms via amplicon sequencing of nifH, archaeal and bacterial amoA, and nxrB genes. The results showed higher ammonia-oxidizing bacteria (AOB) alpha diversity but a lower nitrite-oxidizing bacteria (NOB) diversity in cropland soil compared to grassland soil. Non-metric multidimensional scaling ordinations revealed that diazotroph, AOB and NOB communities differed considerably between grassland and cropland soil. Soil microbial co-occurrence networks showed that conversion of grassland to cropland significantly lowered the average degree, average clustering coefficient, total nodes and links, resulting in less complex microbial networks in cropland soil. Land-use change altered AOB community assembly processes, resulting from a stochasticity-dominated process in grassland soil to a determinism-dominated process in cropland soil. In contrast, deterministic processes were dominant in diazotroph community assembly, whereas stochastic processes were dominant in constructing ammonia-oxidizing archaea and NOB communities in both grassland and cropland soil. These results provide novel evidence that the conversion of grassland to cropland altered the diversity and assembly processes of soil microbial communities involved in soil N-cycling processes, which has important implications for the potential changes in soil functions under land-use changes.
土地利用变化可能会极大地破坏地下微生物多样性，尤其是在脆弱的生态区域。然而，在中国北方农牧交错带，草原开垦为耕地对土壤氮（N）相关微生物群落的影响尚未完全了解。因此，本研究在该地区采集了 24 对草原和耕地土壤样本，通过扩增子测序 nifH、古菌和细菌 amoA 以及 nxrB 基因，研究了土壤 N 相关微生物的群落结构和组装过程。结果表明，与草原土壤相比，耕地土壤中的氨氧化细菌（AOB）多样性较高，但亚硝酸盐氧化细菌（NOB）多样性较低。非度量多维尺度排序表明，固氮菌、AOB 和 NOB 群落在草原和耕地土壤中存在显著差异。土壤微生物共生网络表明，草原开垦显著降低了耕地土壤的平均度、平均聚类系数、总节点和连接数，导致耕地土壤中微生物网络的复杂性降低。土地利用变化改变了 AOB 群落的组装过程，使草原土壤中以随机性为主的过程转变为耕地土壤中以确定性为主的过程。相比之下，在固氮菌群落组装过程中，确定性过程占主导地位，而在草原和耕地土壤中，氨氧化古菌和 NOB 群落的构建则以随机性过程为主。这些结果为草原开垦改变了土壤氮循环过程中土壤微生物群落的多样性和组装过程提供了新的证据，这对土地利用变化下土壤功能的潜在变化具有重要意义。
