水氮控制对荒漠草原中小型土壤动物的影响

Effects of water and nitrogen control on soil meso-and micro-fauna communities in desert steppe

为了解模拟氮沉降和降雨变化对短花针茅荒漠草原中小型土壤动物的影响,本试验设计主区为自然降雨(CK)、增雨30%(W)和减雨30%(R)3个水分处理,副区为0(N0),30(N30),50(N50)和100(N100)kg/(hm^2?a)4个氮素处理共12个处理.研究表明:在相同的水分处理中随着氮浓度的不断增高,表层土壤中中小型土壤动物的个体密度呈先上升后下降趋势.W-N30处理下中小型土壤动物个体密度高于其他处理(P<0.05),类群数随着氮浓度升高呈下降趋势,减雨与过量施氮对表层土壤中中小型土壤动物个体密度具有抑制作用.短花针茅荒漠草原中小型土壤动物在土层中具有明显的表聚特性.另外,冗余分析(RDA)表明,研究区内中小型土壤动物的优势类群与常见类群受环境因子影响较显著,土壤pH值、温度、含水量、有机质和植物全C、全N、C/N对中小型土壤动物个体密度影响均较大,但短期内对类群数的影响不显著.当短花针茅荒漠草原面临全球变化时,随着氮沉降量逐渐增加,表层土壤中中小型土壤动物个体密度先逐渐增加,当达到不同水分条件下氮浓度阈值时,则对表层土壤中中小型土壤动物产生抑制作用.

An experiment with split-plot design which is water treatment as(3 levels:natural rainfall,increasing 30%of rainfall,and decreasing 30%of rainfall)main treatment and nitrogen treatments(4 nitrogen levels:0(N0),30(N30),50(N50)and 100(N100)kg/(hm2?a)as sub-region in Stipa breviflora desert steppe,was conducted to understand the effects of simulated nitrogen deposition and rainfall changes on soil meso-and micro-fauna communities.Our results showed that soil fauna individual density in the surface soil was increased at first and then was decreased with nitrogen concentration increase in same water treatment.Soil meso-and micro-fauna communities individual density in W-N30treatment was significantly higher than that in other treatments(P<0.05),and group number decreased with nitrogen concentration.Rainfall reduction and excessive nitrogen application decreased the individual density of soil meso-and micro-fauna communities in the surface soil.Soil meso-and micro-fauna individual of the surface in Stipa breviflora desert steppe was significantly higher than that of subsurface soil.In addition,redundant analysis(RDA)showed the most obvious responsive to environmental factors soil fauna was the dominant and common groups in the study area.Soil meso-and micro-fauna communities individual density,rather than group number,was greatly influenced by soil pH,temperature,water content,organic matter and total C,total N and C/N ratio in short period.Soil fauna individual density in surface soil increased with nitrogen deposition increased under future projected climate change.However,soil fauna communities in surface soil were restricted when nitrogen reached threshold under different conditions.