氮沉降对内蒙古典型草原地表节肢动物的影响

Effects of nitrogen deposition on ground-dwelling arthropods in a temperate grassland of Inner Mongolia

了解氮沉降增加背景下草原生态系统结构和功能的响应特征,是研发草原可持续管理措施的基础。目前内蒙古典型草原有关氮沉降增加的研究主要集中在植物群落,而对土壤动物影响的研究较少。通过在内蒙古典型草原连续5年的养分添加实验,研究了地表节肢动物对不同氮添加(N_0、N_(2.5)、N_5、N_(10))处理的响应,并分析了4种氮添加处理下地表节肢动物与环境因子之间的关系。结果表明,氮输入增加后,地表节肢动物群落的多样性并没有显著降低(P>0.05),群落多度也没有显著增加(P>0.05),仅在低氮处理下,群落生物量显著高于对照(P<0.05)。不同地表节肢动物功能群对各水平N添加的响应均不太敏感,捕食性、杂食性、腐食性功能群动物的生物量对N添加都没有显著响应(P>0.05),仅植食性动物的生物量在低氮和高氮处理显著高于对照(P<0.05)。回归分析表明,植食性节肢动物的多度和生物量主要受植物叶氮含量显著影响(P<0.05),而腐食性节肢动物的多度、生物量和类群数受土壤有机碳显著影响(P<0.05)。研究表明,温带典型草原地表节肢动物对氮添加的响应受其食物来源影响,明显滞后于植物群落;不同功能群对氮添加有不同响应形式,是群落水平响应较弱的主要原因。

Understanding the features of response of the structure and function of grassland ecosystem to nitrogen deposition is fundamental for developing sustainable management systems. For the typical steppe of Inner Mongolia, there exist many studies on the response of plant communities to the increase of nitrogen deposition, but reports about the grounddwelling arthropods are less available. An investigation on grounddwelling arthropods in response to different nitrogen additions （N0 （i.e., control）, N2.5, N5, N10） was carried out for 5 years in a typical steppe of Inner Mongolia. Furthermore, the relationship between grounddwelling arthropods and environmental factors under four levels of nitrogen addition was analyzed. It was found that there were no significant changes in the diversity and abundance of grounddwelling arthropod community under nitrogen addition treatments （P〉0.05）. A significantly greater arthropod biomass was found only under low nitrogen addition treatment compared to the control （P〈0.05）. There was generally no sensitive response of functional groups of grounddwelling arthropods to N addition treatments. The arthropod biomass of predatory, omnivorous and saprophagous groups did not respond significantly to N addition （P〉0.05）, whereas the biomass of herbivorous was found significantly greater in low and highnitrogen treatments than in the control （P〈0.05）. Regression analysis showed that the number and biomass of phytophagous arthropods were determined by plant leaf nitrogen content （P〈0.05）, whereas those of saprophagous arthropods were influenced by soil organic carbon （P〈0.05）. In conclusion, the responses of grounddwelling arthropod community to nitrogen addition in temperate grassland were mainly affected by their food sources, with an obvious delay compared to plant community. Different functional groups of arthropod had different forms of response to nitrogen addition, which is the main reason for the weaker response at the level of arthropod community.