Effects of nitrogen addition on soil microbes and their implications for soil C emission in the Gurbantunggut Desert, center of the Eurasian Continent

• Published in: The Science of the total environment 2015-05, Vol.515-516, p.215-224
• Main Authors: Huang, Gang, Cao, Yan Feng, Wang, Bin, Li, Yan
• Format: Article
• Language: English
• Subjects: Bacteria; Biomass; Carbon; Carbon - analysis; Carbon Cycle; Carbon utilization; China; Deposition; Desert Climate; Desert ecosystem; Deserts; Ecosystem; Environmental Monitoring; Microbial biomass; Microbial community composition; Microbial respiration; Microorganisms; Nitrogen - analysis; Nitrogen deposition; Respiration; Soil (material); Soil - chemistry; Soil Microbiology; Soil Pollutants - analysis; Soil respiration
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2015.01.054

Nitrogen (N) deposition can influence carbon cycling of terrestrial ecosystems. However, a general recognition of how soil microorganisms respond to increasing N deposition is not yet reached. We explored soil microbial responses to two levels of N addition (2.5 and 5gNm−2yr−1) in interplant soil and beneath shrubs of Haloxylon ammodendron and their consequences to soil respiration in the Gurbantunggut Desert, northwestern China from 2011 to 2013. Microbial biomass and respiration were significantly higher beneath H. ammodendron than in interplant soil. The responses of microbial biomass carbon (MBC) and microbial respiration (MR) showed opposite responses to N addition in interplant and beneath H. ammodendron. N addition slightly increased MBC and MR in interplant soil and decreased them beneath H. ammodendron, with a significant inhibition only in 2012. N addition had no impacts on the total microbial physiological activity, but N addition decreased the labile carbon substrate utilization beneath H. ammodendron when N addition level was high. Phospholipid fatty acid (PLFA) analysis showed that N addition did not alter the soil microbial community structure as evidenced by the similar ratios of fungal to bacterial PLFAs and gram-negative to gram-positive bacterial PLFAs. Microbial biomass and respiration showed close correlations with soil water content and dissolved carbon, and they were independent of soil inorganic nitrogen across three years. Our study suggests that N addition effects on soil microorganisms and carbon emission are dependent on the respiratory substrates and water availability in the desert ecosystem. •Effects of N addition on soil microbes were studied in a temperate desert in 2011–2013.•N addition decreased soil respiration beneath shrubs of H. ammodendron in 2012.•N addition inhibited microbial biomass and respiration beneath H. ammodendron in 2012.•N addition had no effects on microbial community composition.•N addition decreased soil respiration with no alteration of soil carbon stability.