Effects of Nitrogen Deposition on Biocrust Aggregates

Nitrogen (N) deposition affects various aspects of terrestrial ecosystem structure and function, and microbial communities may be particularly sensitive to anthropogenic N inputs. However, our knowledge of the effects of nitrogen deposition on microbial communities is far from complete, especially in drylands where data are relatively scarce. Biological crust is the most important part of the dryland ecosystem, which maintains the stability of the dryland ecosystem. For example, affecting soil hydrological cycle, reducing high solar radiation to soil, improving soil cation exchange capacity and porosity. To better understand the response of dryland biocrusts to nitrogen deposition, we conducted a year-long experiment with different nitrogen sources in the Gurbantunggut Desert in northwestern China. We evaluated the effect of different nitrogen sources on the bacterial community composition, enzyme activity and physicochemical properties in the aggregate structure of biological crusts: our results showed that the addition of ammonium nitrogen and nitrate nitrogen reduced the sheath microbes in single and compound grains. The relative abundance of Coleopsis, and at the same time, under the microscope, the proportion of Microcoleella fascicles in complex grain aggregates also decreased significantly. On the whole, the relative abundance of M. sheathis in single grains was lower than that in complex grains. On the other hand, the addition of nitrate nitrogen and ammonium nitrogen significantly reduced the physicochemical properties and enzyme activities of biocrust aggregates.