Soil resource availability impacts microbial response to organic carbon and inorganic nitrogen inputs

Article type: Research Article

Authors: ZHANG, Wei-jian^; | ZHU, W. | HU, S.

Affiliations: Department of Agronomy, Nanjing Agricultural University, Nanjing 210095, China | Department of Plant Pathology, North Carolina State University, Raleigh, NC 27605, USA | Department of Biological Sciences, State University of New York-Binghamton, Binghamton, NY 13902, USA

Note: [] Corresponding author. E-mail: zwj@njau.edu.cn

Abstract: Impacts of newly added organic carbon (C) and inorganic nitrogen (N) on the microbial utilization of soil organic matter are important in determining the future C balance of terrestrial ecosystems. We examined microbial responses to cellulose and ammonium nitrate additions in three soils with very different C and N availability. These soils included an organic soil (14.2% total organic C, with extremely high extractable N and low labile C), a forest soi1 (4.7% total organic C, with high labile C and extremely low extractable N), and a grassland soil (1.6% total organic C, with low extractable N and labile C). While cellulose addition alone significantly enhanced microbial respiration and biomass C and N in the organic and grassland soils, it accelerated only the microbial respiration in the highly-N limited forest soil. These results indicated that when N was not limited, C addition enhanced soil respiration by stimulating both microbial growth and their metabolic activity. New C inputs lead to elevated C release in all three soils, and the magnitude of the enhancement was higher in the organic and grassland soils than the forest soil. The addition of cellulose plus N to the forest and grassland soils initially increased the microbial biomass and respiration rates, but decreased the rates as time progressed. Compared to cellulose addition alone, cellulose plus N additions increased the total C-released in the grassland soil, but not in the forest soil. The enhancement of total Creleased induced by C and N addition was less than 50% of the added-C in the forest soil after 96 d of incubation, in contrast to 87.5% and 89.0% in the organic and grassland soils. These results indicate that indigenous soil C and N availability substantially impacts the allocation of organic C for microbial biomass growth and/or respiration, potentially regulating the turnover rates of the new organic C inputs.

Keywords: cellulose, inorganic nitrogen, microbial biomass, microbial activity, carbon sequestration

Journal: Journal of Environmental Sciences, vol. 17, no. 5, pp. 705-710, 2005