Abstract
ABSTRACT: An incubation experiment was conducted to examine the effects of nitrogen (N) applications in different forms (NH 4 NO 3 , NH 4 Cl, and KNO 3 ) on microbial respiration considering 3 different alpine meadow soils (C poor soil, pH = 8.1, 1.6% C; C moderate soil, pH = 6.0, 5.0% C; C rich soil, pH = 7.1, 7.4% C) in the Tibetan Plateau. The addition of NH 4 NO 3 and NH 4 Cl increased the microbial respiration in C poor soil, but KNO 3 had no effect. The inorganic N forms had no effects on C rich soil, but decreased microbial SOIL AND PLANT NUTRITION - Article Differential response of microbial respiration to supplied nitrogen forms in 3 contrasting alpine meadow soils on the Tibetan Plateau Xiaoyang Zeng* Sichuan College of Architectural Technology - Department of Landscape Architecture - Chengdu (Sichuan), China. *Corresponding author: zengxy@sina.cnReceived: Apr. 26, 2016 – Accepted: Oct. 3, 2016 respiration in C moderate soil. Soil microbial respiration levels across the different types were ordered as follows: C poor soil < C rich soil < C moderate soil, regardless of N addition. These results suggest that the effect of N on microbial respiration in alpine meadow soils is more dependent on the initial soil pH than on soil C availability.
Highlights
Soil microbial respiration, i.e. the production of carbon dioxide (CO2) through soil organic carbon (C) decomposition by microbes, is an important component of the global C cycle (Schlesinger and Andrews 2000; Kaštovská et al 2010)
The negative effects of N on soil microbial respiration are generally believed to be due to the reduction of soil pH following N addition, inhibiting soil microbial activity (Ouyang et al 2008; Ramirez et al 2012)
This study showed that the application of NH4NO3 and NH4Cl significantly reduced soil pH, but KNO3 had no significant effects on it, suggesting that pH cannot fully account for the negative effects of N on soil microbe respiration
Summary
I.e. the production of carbon dioxide (CO2) through soil organic carbon (C) decomposition by microbes, is an important component of the global C cycle (Schlesinger and Andrews 2000; Kaštovská et al 2010). The studies have shown disparate results, but most suggest that N application inhibits the biological activity of soil microbes and reduces soil microbial respiration rates (Bowden et al 2004; Craine et al 2007; Ouyang et al 2008, Kaštovská et al 2010; Ramirez et al 2012) It is still unclear whether the response of soil microbial respiration is directly due to the increased C availability following N application, or indirectly caused by changes in chemical properties (such as pH) of soils resulting from N application (Khalil et al 2007; Ramirez et al 2012). Most studies were conducted on soils in the temperate or northern climatic zones (Craine et al 2007; Kaštovská et al 2010; Ramirez et al 2012), and little information is available for soils in alpine areas
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