Effects of Stimulated Nitrogen Deposition on the Bacterial Community Structure of Semiarid Temperate Grassland

Abstract

With the development of economics, the deposition of available nitrogen in the terrestrial ecosystem is increasing dramatically due to anthropic activities, which negatively impacts the sustainability of the ecosystem ecology. In this study, the effect of long-term stimulated nitrogen deposition[with nitrogen addition of 0, 1, 4, 8, and 32 g·(m2·a)-1] on the microbial community structure of soil was investigated in a temperate steppe in Inner Mongolia using a pyrosequencing technique targeting the bacterial 16S rRNA gene. The results show that the available nitrogen in soil increases with increasing nitrogen addition, resulting in the decrease of the soil pH. The results of pyrosequencing indicate that soil bacterial OTU (operational taxonomy unit) numbers increase with increasing nitrogen deposition, while bacterial α diversity indices show an initial increase and subsequent decrease. Non-metric multidimensional scaling (NMDS) analysis indicates that the bacterial community structure significantly varies among treatments, which can be largely attributed to the changes in the soil pH and nitrogen content due to nitrogen deposition. At the class level, the relative abundance of different bacterial groups shows a varying trend depending on the nitrogen deposition. This study indicates that long-term nitrogen deposition significantly impacts the bacterial community by changing the soil properties.