模拟氮沉降对草甸草原中小型土壤节肢动物群落的影响

为了解析氮沉降对草甸草原中小型土壤节肢动物群落结构的影响,于2010年在内蒙古呼伦贝尔市鄂温克旗贝加尔草甸草原设计了模拟氮沉降试验,研究了在8个氮沉降梯度N0(对照)、N15、N30、N50、N100、N150、N200和N300下土壤动物群落结构和多样性的变化以及与环境因子之间的关系。土壤动物于2019年牧草返青期(5月)、生长期(8月)和枯黄期(9月末)分别采集。结果表明,中小型土壤节肢动物具有明显的表聚特征,但随着施氮量的增加土壤动物群落有向深层土壤迁移的趋势。试验区植被生长期良好的水热条件更适合中小型土壤节肢动物群落发展。N200和N300处理下的土壤动物个体数、类群数及多样性指数均显著高于对照与氮沉降较低处理(P0.05)。依据土壤动物优势类群和常见类群分布情况,采用主成分分析(PCA)将氮梯度划分为3组,N0～N150处理一组,N200和N300各为一组,研究表明N200分布类群最多。冗余分析(RDA)表明,速效钾、全氮、NO–3–N、p H、有机质和含水量是影响土壤动物群落分布的主要环境因子。总体而言,氮沉降对土壤动物群落发展有促进作用,但是存在阈值,本研究中氮沉降对土壤动物群落水平影响的阈值为N 200 kg/(hm2·a)。

Effects of Simulated Nitrogen Deposition on Meso-micro Soil Fauna Communities in Meadow Steppe

Soil fauna play a key role in maintaining the biogeochemical cycle and ecological function of terrestrial ecosystems. In order to understand the effect of nitrogen deposition on the community structure of meso-micro soil fauna in meadow steppe, a simulated nitrogen deposition experiment was designed in 2010 in Baikal meadow steppe, Ewenke Banner, Hulunbuir City, Inner Mongolia. The changes of soil fauna community structure and diversity and their relationship with environmental factors were studied under 8 nitrogen deposition gradients N0 (control), N15, N30, N50, N100, N150, N200 and N300. Soil fauna were collected in 2019 in the grass turning green period (May), the growing period (August) and the withering period (the end of September). The results showed that meso-micro soil fauna had obvious surface aggregation characteristics, but the soil fauna community tended to migrate to deep soil with the increase of nitrogen application. The good hydrothermal conditions in the growing period of vegetation in the experimental area are more suitable for the development of meso-micro soil fauna community. The individual number, group number and diversity index of soil fauna under N200 and N300 treatments were significantly higher than those of the control and lower nitrogen deposition treatments (P<0.05). According to the distribution of dominant groups and common groups of soil fauna, the nitrogen gradient was divided into three groups by principal component analysis (PCA), one group treated with N0-N150, N200 and N300 respectively. Redundancy analysis (RDA) showed that available potassium, total nitrogen, nitrate nitrogen, pH, organic matter and water content were the main environmental factors affecting the distribution of soil fauna communities. Generally speaking, nitrogen deposition can promote the development of soil fauna community, but there is a threshold. In this study, the threshold of the effect of nitrogen deposition on the level of soil animal community is 200 Kg N hm-2 yr-1.