ABSTRACT Methane (CH4) and nitrous oxide (N2O) are two greenhouse gases with much more warming potential than carbon dioxide (CO2). However, there have been less studies on their responses to climate warming and land use practices, such as hay harvest in grasslands. Especially, their fluxes are not well estimated during the nongrowing season. In this study, we investigated year-round (August 2015–August 2016) continuous measurements of CH4 and N2O fluxes in response to simulated warming, clipping (as a mimic of hay harvest), and their interaction in an alpine meadow on the Qinghai-Tibetan Plateau. Compared to the control, warming alone and in combination with clipping significantly increased CH4 uptake by 42% and 51%, respectively, on the annual basis. Warming alone also significantly decreased year-round N2O emission by 57% relative to that under control. However, clipping alone did not affect CH4 and N2O fluxes during the study period, and no significant interactive effect of clipping and warming was detected. Furthermore, warming had larger effects on CH4 uptake but smaller effects on N2O emission in the growing than nongrowing season. We also found that the responses in CH4 and N2O fluxes to different treatments were regulated by changes in soil temperature and moisture. Based on sustained global warming potential approach and expressed as CO2-equvalents, the ecosystem switched from a net source of these two gases in the control (1.2 g CO2-eq m-2) to a net sink in warming (-11.3 g CO2-eq m-2) and its combination with clipping (-9.9 g CO2-eq m-2). The findings highlight the importance of understanding greenhouse gas fluxes in the nongrowing season and suggest the increase of CH4 uptake and reduction in N2O emission under climate warming will benefit ecosystem feedback and help mitigate climate change.

中文翻译：

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气候变暖和气候变化对高寒草甸 CH4 和 N2O 通量的影响

摘要 甲烷 (CH4) 和一氧化二氮 (N2O) 是两种温室气体，其变暖潜力比二氧化碳 (CO2) 大得多。然而，关于它们对气候变暖和土地利用实践的反应的研究较少，例如在草原收割干草。特别是，在非生长季节，它们的通量不能很好地估计。在这项研究中，我们调查了全年（2015 年 8 月至 2016 年 8 月）对 CH4 和 N2O 通量的连续测量，以响应模拟变暖、修剪（作为干草收获的模拟）及其在青海高山草甸中的相互作用。青藏高原。与对照相比，单独变暖和结合消减每年显着增加 CH4 吸收量，分别为 42% 和 51%。与控制下的排放量相比，仅变暖一项就使全年的 N2O 排放量显着降低了 57%。然而，在研究期间，单独的削峰不影响 CH4 和 N2O 通量，并且没有检测到削峰和变暖的显着交互作用。此外，与非生长季节相比，变暖对生长季 CH4 吸收的影响较大，但对 N2O 排放的影响较小。我们还发现 CH4 和 N2O 通量对不同处理的响应受土壤温度和水分变化的调节。基于持续的全球变暖潜势方法并以 CO2 当量表示，生态系统从这两种气体的净来源（1.2 g CO2-eq m-2）转变为变暖的净汇（-11.3 g CO2- eq m-2) 及其与剪切的组合 (-9.9 g CO2-eq m-2)。