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Short-term effects of night warming and nitrogen addition on soil available nitrogen and microbial properties in subalpine coniferous forest, Western Sichuan, China

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Author(s): CHEN Zhi | YIN Hua-Jun | WEI Yun-Yan | LIU Qing

Journal: Chinese Journal of Plant Ecology
ISSN 1752-9921

Volume: 34;
Issue: 11;
Start page: 1254;
Date: 2010;

Keywords: available nitrogen | microbial biomass | nitrogen addition | subalpine forest | warming

ABSTRACT
Aims The subalpine coniferous forest in eastern Qinghai-Tibet Plateau provides a natural laboratory for studying effects of climate change on terrestrial ecosystems. Research on responses of soil nitrogen availability and microbial properties to experimental warming and nitrogen addition can provide insights into their C resource/sink function under future climates.Methods We used an infrared heater combined with nitrogen addition to determine the short-term influences of two level of air temperature (ambient and warmed) and nitrogen addition (0 and 25 g N·m–2·a–1) on soil chemical properties, available nitrogen and microbial biomass.Important findings The warming manipulation increased mean air temperature and soil temperature at 5-cm depth by 1.93 and 4.19 °C, respectively, and the temperature increment was larger in summer and winter. Warming generally had no significant effects on soil pH, organic C, total N and microbial biomass, but it decreased soil ammonium nitrogen and increased nitrate nitrogen content. The warming effect was reduced with time. Nitrogen addition significantly increased available nitrogen and microbial biomass, but decreased soil pH, acidifying the soil. Compared with individually warming or adding nitrogen, the interaction of the two factors significantly increased organic C, available N and microbial biomass. Results suggest that soil nitrogen availability and microbial properties were sensitive to N status. Although soil nitrogen availability and microbial properties may adapt to temperature increase to some extent, the interaction of the warming and nitrogen addition significantly changed their response mode. Therefore, nitrogen deposition and multiple factors have interacting effects on the ecosystem and these should be further studied in this region.
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