荒漠草原土壤线虫对氮沉降及降雨变化的响应

为了解氮沉降和降雨变化对短花针茅荒漠草原土壤线虫的影响，试验设计采用主区为增雨30%（W）和减雨30%（R）、自然降雨（CK）3种水分处理，副区为0（N0）、30（N30）、50（N50）和100（N100） kg/（hm²·a）4个氮素梯度共12个处理.结果表明：研究区共鉴定土壤线虫隶属41属，群落优势属为丽突属（Acrobeles）和拟丽突属（Acrobeloides），增雨较氮添加显著增加了线虫数量，且在10月份尤为明显，减雨下N50梯度更利于线虫数量增加；从功能类群来看，土壤0~10cm食细菌线虫数量最多（占总数41.00%~45.56%），并随季节动态呈上升趋势，捕杂食线虫数量最低，食细菌和食真菌线虫与氮梯度呈负相关关系；从生态指数来看，仅增雨抑制了土壤线虫多样性，单一氮添加没有改变线虫群落多样性和稳定性，但较低的氮添加会显著降低了线虫丰富度.不同季节动态处理下，土壤矿化途径受食微线虫的影响，有机质以真菌降解通道为主，减雨施氮下提高了土壤抗干扰能力；pH值、有机质、铵态氮含量是影响土壤线虫群落重要的环境因子，土壤氮含量增多及pH值降低增加了偏K策略者类群数量，降低R对策者类群数量，土壤线虫群落结构的变化，表明短花针茅荒漠草原生态系统地下食物网稳定性渐趋增强.

Response of soil nematodes in desert steppe to nitrogen deposition and rainfall changes

A twelve-treatment experiment with the main plot(three water treatments: 30% increase (W), 30% reduction (R),and natural rainfall (CK) and split-plot (0 (N0), 30 (N30), 50 (N50) and 100 (N100) kg/(hm²·a)4nitrogen gradients was designed in Stipa breviflora desert steppe to investigate the impact of nitrogen deposition and rainfall changes on soil nematodes. A total of 41 genera of soil nematodes were identified in the study area, and the dominant community genera were Acrobeles and Acrobeloides. Compared with nitrogen addition, the number of nematodes wasincreased significantly in precipitation and that influences were especially obvious in October. N50 gradient was more beneficial to increase the number of nematodes under the situation of reduced rain. In terms of functional groups, the largest part bacterial-eating nematodes in the 0~10cm soil were 41.00% to 45.56% of the total and an upward trend was shown in the seasonal dynamics, while the lowest part was the number of omnivorous nematodes. Bacteria-eating and fungus-eating nematodes were negatively correlated with nitrogen gradients. According to the ecological index, soil nematode diversity would be inhibited by only increasing rainfall, and the nematode community diversity and stability was not changedby single nitrogen addition. However, the abundance of nematodes was terrifically cut down by lower nitrogen addition. Under dynamic treatments in different seasons, the soil mineralization pathway was affected by micro-nematodes, and the organic matter was mainly degraded by fungi. Under reduced rainfall and nitrogen application, soil anti-interference ability was improved. Important environmental factors affecting soil nematode communities were pH, organic matter, and ammonium nitrogen content. The number of K-strategist groups was increased in increasing soil nitrogen content and decreasing in pH, while the number of R-strategist groups was reduced. Changing in soil nematode community structure was indicated that the stability of the underground food web in the Stipa breviflora desert steppe ecosystem was gradually increased.