模拟降雨减少对刺槐人工林土壤养分和微生物群落的影响

降雨是黄土高原地区土壤水分的最主要来源。为探明降雨减少对黄土高原半湿润区土壤养分和土壤微生物群落的影响，以刺槐人工林为研究对象，通过搭设透光遮雨板将部分穿透雨导流至样地外，实施了4年减少总降雨输入约47%的处理，测定了在不同降雨条件下林地的土壤养分含量、土壤微生物多样性及群落结构特征，分析了土壤养分和土壤微生物对降雨减少的响应。结果表明：减雨处理4年后(1)处理样地土壤有机碳、全氮、全磷含量均低于对照样地，全氮含量差异达到显著水平(P<0.05)。(2)对照样地生长季和非生长季土壤微生物多样性差异不显著，减雨处理样地非生长季的细菌均匀度显著低于处理样地生长季和对照样地非生长季(P<0.05);降雨减少对细菌和真菌的群落结构有显著影响(P<0.05),降雨减少显著降低了酸杆菌门(Acidobacteria)的相对丰度，提高了放线菌门(Actinobacteria)、绿弯菌门(Chloroflexi)、子囊菌门(Ascomycota)和被孢霉门(Mortierellomycota)的相对丰度(P<0.05)。(3)土壤有机碳、全氮含量与部分细菌相对丰度显著相关，土壤...

Effects of simulated rainfall reduction on soil nutrients and microbe community in Robinia pseudoacacia plantation

Rainfall is the main source of soil moisture in the Loess Plateau, China. In order to investigate the impact of rainfall reduction on soil nutrients and soil microbial communities of a Robinia pseudoacacia plantation in the sub-humid area of Loess Plateau, a rainfall reduction experiment was conducted. Rainfall exclusion was conducted by installing translucent panels to divert part of the throughfall outside the treatment plot. Rainfall partitioning investigation and the panel area for throughfall exclusion estimated that the treatment plot received about 47% reduction of the total rainfall input. After 4 years of treatment, soil nutrient content, soil microbial community structure and diversity were measured in the sample plots with and without rainfall reduction. The main results are as follows:(1) The contents of soil organic carbon, total nitrogen, and total phosphorus in the treated plot were lower than those in the control plot, and the difference in the total nitrogen content reached a significant level (P<0.05). (2) There was no significant difference in soil microbial diversity between growing and non-growing seasons in the control plot. The Simpson index of the treated plot during non-growing season was significantly lower than that in growing season and that of the control plot in non-growing season (P<0.05). Rainfall reduction had a significant effect on the community structure of bacteria and fungi (P<0.05). The rainfall reduction treatment significantly decreased the relative abundance of Mcidobacteria, but increased the relative abundance of Actinobacteria, Chloroplexi, Ascomycota, and Mortierellomycota (P<0.05). (3) Both soil organic carbon and total nitrogen contents were significantly correlated with the relative abundance of some bacteria, and soil total nitrogen content was significantly positively correlated with the relative abundance of Mortierellomycota fungi (P<0.05). In brief, the 4-year treatment of rainfall reduction resulted in a weak impact on soil nutrient content, but had significant effects on bacterial diversity, and the structure of bacterial and fungal community. There was also a correlation between soil nutrient content and the relative abundance of soil microorganisms. The results provided theoretical reference for further study on the impact of potentially continuous rainfall reduction on forest ecosystems in the sub-humid area of Loess Plateau, China.