Stoichiometric responses of soil microflora to nutrient additions for two temperate forest soils
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The ratios of soil carbon (C) to nitrogen (N) and C to phosphorus (P) are much higher in Chinese temperate forest soils than in other forest soils, implying that N and P might limit microbial growth and activities. The objective of this study was to assess stoichiometric responses of microbial biomass, enzyme activities, and respiration to N and P additions. We conducted a nutrient (N, P, and N + P) addition experiment in two temperate soils under Korean pine (Pinus koraiensis) plantation and natural broadleaf forest in Northeast China and measured the microbial biomass C, N, P; the activities of β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG), and acid and alkaline phosphomonoesterase (AP); and the microbial respiration in the two soils. Nitrogen addition increased microbial biomass N and decreased microbial biomass C-to-N ratio and microbial respiration in the two soils. Nitrogen addition decreased NAG activity to microbial biomass N ratio, P addition decreased AP activity to microbial biomass P ratio, and N, P, and N + P additions all increased BG activity to microbial biomass C ratio. These results suggest that microbial stoichiometry is not strictly homeostatic in response to nutrient additions, especially for N addition. The responses of enzyme activities to nutrient additions support the resource allocation theory. The N addition induced a decline in microbial respiration, implying that atmospheric N deposition may reduce microbial respiration, and consequently increase soil C sequestration in the temperate region.
KeywordsEnzyme Microbial biomass Microbial respiration Nitrogen addition Phosphorus addition Stoichiometry
We thank Dr. Paolo Nannipieri and two anonymous reviewers for their constructive comments, Taidong Zhang for his field assistance, and the Maoershan Forest Ecosystem Research Station for field logistic support. This work was financially supported by the National Key Research and Development Program of China (2016YFD0600201) and the Program for Changjiang Scholars and Innovative Research Team in University (IRT_15R09) to C.K. Wang and the Fundamental Research Funds for the Central Universities (2572016AA08) to Z.H. Zhou.
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