The Effects of Nitrogen Deposition on Soil Respiration in an Alpine Meadow in Northern Tibet

doi:10.3969/j.issn.1000-6362.2019.04.002

Abstract

Abstract:

The increase of nitrogen deposition in the world resulted increases of nitrogen input to terrestrial ecosystems and affects soil CO2 emissions. NH₄NO₃ was used to simulated nitrogen deposition to determine the effect of nitrogen deposition on soil respiration during the growing season (June-August) in 2014 in alpine meadow in northern Tibet. The nitrogen deposition rate is 40kgN·ha^-1·y^-1 (N40) according to the distribution pattern of nitrogen deposition in China, the added nitrogen was sprayed onto the N40 plots monthly, while CK plots received the same amount of water. Plant community biomass was measured regularly during the growing season. Meanwhile, the LI-8100 Automated Soil CO₂Flux System was used to measure soil respiration rates periodically from late June to early September, and measured in two Typical Clear Days as the diurnal dynamics of the soil respiration rate. The main results are showed as follow: (1) nitrogen deposition significantly increased the above-ground biomass in alpine meadow (P<0.05). (2) The soil respiration rate had obvious diurnal and monthly pattern in both treatments. And the diurnal dynamics of soil respiration showed a double peak curve and the peak values were assumed at about 13：00–14：00 and 16：00, respectively. The monthly dynamics of soil respiration showed a single-peak curve, and the maximum appeared in August and lower at early and end of growing season. (3) Nitrogen deposition significantly increased the average soil respiration by 66.1% (P<0.001) compared with control plots in growing season. (4) Soil respiration rates showed a significant positive correlation with soil temperature, soil moisture and above-ground biomass (P<0.001). (5) Nitrogen deposition had no significant effect on temperature sensitivity of soil respiration. The results showed that the increase of soil respiration due to the increase of above-ground and below-ground biomass caused by nitrogen deposition in the alpine meadow.

Key words: Alpine meadow, Nitrogen deposition, Soil respiration, Above-belowground biomass, Sensitivity of soil respiration

GE Yi-qing, YAN Yu-long, LIANG Yan, HASBAGAN Ganjurjav, HU Guo-zheng,YANG Jie, GAO Qing-zhu, HE Shi-cheng, DANJIU Luobu. The Effects of Nitrogen Deposition on Soil Respiration in an Alpine Meadow in Northern Tibet[J]. Chinese Journal of Agrometeorology, 2019, 40(04): 214-221.

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