不同连作年限设施农用地土壤有机碳与细菌群落功能特征

为探明不同连作年限设施农用地土壤有机碳(Soil organic carbon, SOC)与细菌群落功能变化及其动态响应关系，以北京市南郊设施农业集中地为研究区，采用时空替代法系统分析了未种植(CK)、连作年限0～5年(0～5 a)、5～10年(5～10 a)、10～20年(10～20 a)和20年以上(20 a+)SOC、细菌群落结构及其代谢功能的变化。结合冗余分析(RDA)、典型相关分析(CCA)、PICRUSt2功能预测及Mantel test探究了SOC及其活性组分与细菌优势菌群的动态响应，以及与细菌代谢功能的相互关系。结果表明：连作使研究区微生物生物量碳(Microbial biomass carbon, MBC)、易氧化有机碳(Easily oxidizes organic carbon, EOC)、SOC含量及土壤有机碳密度(Soil organic carbon density, SOCD)均随种植年限先增后减，可溶性有机碳(Dissolved organic carbon, DOC)含量在20 a+时最高，微生物熵(Q)随连作年限增加而减小。连作降低了土壤细菌的多样性...

Characteristics of Soil Organic Carbon and Bacterial Communities Functional in Agricultural Lands of Facilities with Different Continuous Cropping Periods

To investigate the changes in soil organic carbon (SOC), bacterial communities and metabolic functions, as well as the dynamic response relationships with each other in facility agricultural land with different cropping periods, organic carbon, bacterial community structure and metabolic functions in soil were systematically characterized in unplanted (CK), 0 to 5a (0~5a), 5a to 10a (5~10a), 10a to 20a (10~20a) and more than 20a (20a+) of continuous cropping by using temporal-spatial substitution method in a centralized area of facility agriculture in the southern suburb of Beijing as the study area. The dynamic response of SOC and its active components to the bacterial dominant communities and their interrelationships with bacterial metabolic functions were explored with redundancy analysis (RDA), typical correlation analysis (CCA), prediction of PICRUSt2 function, and Mantel test. Based on the results, continuous cropping caused the contents of microbial biomass carbon (MBC), easily oxidizes organic carbon (EOC), SOC and soil organic carbon density (SOCD) all showed an increasing and then decreasing trend with the increase of cropping period. Dissolved organic carbon (DOC) content was the highest at 20a+. Microbial entropy (Q) was decreased with the increase of cropping period. Continuous cropping decreased the diversity of soil bacteria and increased the differences among bacterial species. PICRUSt2 prediction showed that the functions of soil bacteria in different continuous cropping period were dominated by metabolism, and the abundance of secondary metabolism functions of bacteria was significantly higher in the soil from 5~20a than that in the soil from 0~5a, 20a+, and CK. Among the bacterial groups in the top 10 relative abundance, the Acidobacteriota were negatively correlated with both SOC and its active components. The key bacterial groups dominating and participating in SOC accumulation and cycling showed a shift from eutrophic to oligotrophic and pathogenic taxa after 20a+ of continuous cropping. Mantel analysis showed that a total of 53 classes of functions in the third tier were significantly correlated (p<0.05) with SOC and its components. Among them, totally 23 classes were affiliated to metabolic functions in the first tier, and as many as 51 classes were significantly correlated with EOC. The finding can provide scientific references for optimizing carbon cycle-related bacterial functional groups and enhancing the carbon sink function of small-scale facility agricultural soils.