不同时限氮沉降和降水变化对荒漠草原中小型土壤节肢动物群落结构与多样性的影响

Effects of nitrogen deposition and precipitation changes in different time spans on community structure and diversity of soil meso-and micro-fauna in Stipa breviflora desert steppe

全球背景下的氮沉降和降水变化对荒漠草原生态系统产生巨大影响。为探究不同时限氮沉降和降水变化对荒漠草原中小型土壤节肢动物群落结构与多样性的影响,于2015年在内蒙古四子王旗短花针茅荒漠草原设置主区为减雨(R)、自然降水(CK)、增雨(W)3个水分梯度,副区为N_(0)、N_(30)、N_(50)、N_(100)4个氮素梯度的模拟试验,对比分析2016、2020年土壤节肢动物变化。结果表明:2016年在样地内共捕获并分离中小型土壤节肢动物553只,隶属节肢动物门的10目46科;2020年在样地内共捕获并分离中小型土壤节肢动物1211只,隶属节肢动物门的13目41科,其中24科与2016年不同;R处理下2016年N_(30)处理下捕获数量最多,2020年N_(50)处理中捕获数量最多;2016年中小型土壤节肢动物个体数量0~10 cm与10~20 cm土层比值为3.98,2020年比值为1.83,相比2016年下降了54%;WN_(50)、WN_(100)处理下2020年多样性指数、丰富度指数明显高于2016年,CKN_(50)、CKN_(100)处理下2020年优势度指数低于2016年,PCoA分析结果显示水分处理对荒漠草原中小型土壤节肢动物群落分布影响更为显著(P<0.05);冗余分析结果表明5年的水氮变化后土壤pH值与土壤节肢动物多样性及数量指标相关性增强。综上所述,在全球变化的大背景下,精确调控土壤pH值可以进一步影响土壤节肢动物在土壤生态系统中的功能。

Nitrogen deposition and precipitation changes have great impacts on desert steppe ecosystems.In order to investigate the different effects of nitrogen deposition and precipitation changes in different time frames on the structure and diversity of soil meso-and micro-fauna communities under desert steppe,simulation experiments were set up in 2015 in the Stipa breviflora desert steppe of Siziwangqi,Inner Mongolia,with three moisture gradients of reduced rainfall(R),natural precipitation(CK),and increased rainfall(W)as main plots,and N_(0),N_(30),N_(50),and N_(100) nitrogen levels as subplots in a split-plot experiment.Soil fauna changes were analysed by comparing data for 2016 and 2020.It was found that 553 soil meso-and micro-fauna,belonging to 10 orders and 46 families of Arthropoda,were captured and isolated in the sample plots in 2016;1211 soil meso-and micro-fauna,belonging to 13 orders and 41 families of Arthropoda,were captured and isolated in the sample plots in 2020,of which 24 families were different from those in 2016.Under the R treatment the highest number of captures were made under the N_(30) treatment in 2016,and the highest number of captures were made under the N_(50) in 2020.The ratio of individual density of soil meso-and micro-fauna in the 0-10 cm soil layer to that in the 10-20 cm soil layer was 3.98 in 2016,and was 1.83 in 2020-a decrease of 54%compared with 2016.The diversity index and richness index in 2020 under the WN_(50) and WN_(100) treatments were higher than those in 2016,and the dominance index in 2020 under CKN_(50) and CKN_(100) treatments was lower than in 2016.The results of principal coordinates analyses showed that moisture treatments had a more significant effect on the distribution of soil meso-and micro-fauna in the desert steppe(P<0.05);and the results of redundancy analyses showed that the correlation between soil pH and soil fauna diversity and quantity indicators was enhanced after 5 years of changed water and nitrogen availability.In summary,under the background of global change,precise regulation of soil pH can further influence the ecological functions of soil fauna in soil ecosystems.