Characterizing nitric oxide emissions from two typical alpine ecosystems

Fei Lin , Chunyan Liu , Xiaoxia Hu , Yongfeng Fu , Xunhua Zheng , Rui Wang , Wei Zhang , Guangmin Cao


Received March 16, 2018,Revised , Accepted August 30, 2018, Available online September 18, 2018

Volume 77,2019,Pages 312-322

A portion of alpine meadows has been and will continue to be cultivated due to the concurrent increasing demands for animal- and crop-oriented foods and global warming. However, it remains unclear how these long-term changes in land use will affect nitric oxide (NO) emission. At a field site with a calcareous soil on the Qinghai-Tibetan Plateau, the authors measured the year-round NO fluxes and related variables in a typically winter-grazed natural alpine meadow (NAM) and its adjacent forage oat field (FOF). The results showed that long-term plow tillage, fertilization and growing forage oats significantly yielded ca. 2.7 times more (p < 0.01) NO emissions from the FOF than the NAM (conservatively 208 vs. 56 g N/(ha·year) on average). The spring freeze–thaw period and non-growing season accounted for 17%‐35% of the annual emissions, respectively. The Q10 of surface soil temperature (Ts) was 8.9 in the NAM (vs. 3.8 in the FOF), indicating increases of 24%–93% in NO emissions per 1–3 °C increase. However, the warming-induced increases could be smaller than those due to land use change and management practices. The Ts and concentrations of ammonium, nitrate and water-extractable organic carbon jointly explained 69% of the variance in daily NO fluxes from both fields during the annual period (p < 0.001). This result indicates that temporally and/or spatially distributed NO fluxes from landscapes with calcareous soils across native alpine meadows and/or fields cultivated with forage oats can be predicted by simultaneous observations of these four soil variables.

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