Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/18/2011
Publication Date: 11/15/2011
Publication URL: www.ars.usda.gov/sp2UserFiles/Place/53482500/TemporaryPublicationFilepubswithnohandle/Impacts of altitude and position on the rates.pdf
Citation: Zhang, S., Chen, D., Sun, D., Wang, X., Smith, J.L., Du, G. 2011. Impacts of altitude and position on the rates of soil nitrogen mineralization and nitrification in alpine meadows on the eastern Qinghai-Tibetan Plateau, China. Biology and Fertility of Soils. DOI 10.1007/s00374-011-0634-5. Interpretive Summary: It is now mostly agreed that global surface temperatures are increasing. The increase in surface temperatures will cause soils to warm affecting the nitrogen cycle. These effects need to be documented because nitrogen can leak into the atmosphere as a greenhouse gas or move through soil water into the groundwater, both pathways are contamination. We found that in alpine meadows soil temperature and moisture controlled soil nitrogen cycling as elevation increased. This implies that as surface temperatures rise more nitrogen will be released from the soil to potentially become a contaminate. Thus, it will become very important to manage alpine grasslands, in terms of inputs and grazing, to minimize the effects of rising soil temperatures on the cycling of nitrogen.
Technical Abstract: Alpine and tundra grasslands constitute 7% world terrestrial land but 13% of the total global soil carbon (C) and 10% of the global soil nitrogen (N). Under the current climate change scenario of global warming, these grasslands will contribute significantly to the changing global C and N cycles. It is important to understand the controlling factors on soil N cycling in these ecosystems. To evaluate climate effects on N cycling, soil N mineralization and nitrification rate (0-15 cm) were measured using an in situ closed-top tube incubation across altitudes and aspects from 2006 to 2008 in alpine meadows. The data indicated that soil N mineralization and nitrification rates decreased with increasing altitude but only significantly (P<0.05) between the lowest and the two higher altitudes, soil N mineralization and nitrification rates of South Facing (SF) slope were higher than North Facing (NF) slope at each altitude, which suggested soil temperature and soil water content were the controlling factors for soil N mineralization and nitrification rates across altitude and soil water content was the main regulated factor at aspect. Soil N nitrification rate was dependent on soil N mineralization rate and therefore have exhibited the same response as soil N mineralization trends. Meanwhile, soil N nitrification rate was higher than soil N mineralization rate in this meadow area which indicated that soil N mineralization and nitrification rates will increase in response to regional warming of the alpine meadow on the eastern Qinghai-Tibetan Plateau.