Limited understanding of the effects of enhanced nitrogen (N) addition and grazing exclusion (E) on greenhouse gases fluxes (GHGs: CO₂, CH₄, and N₂O) in grasslands constrains our ability to respond to the challenges of future climate change. In this study, we conducted a field experiment using a static closed opaque chamber to investigate the response of GHG fluxes to N addition (69 kg N ha⁻¹ year⁻¹ applied in 3 splits) and grazing exclusion in an alpine meadow on the Tibetan Plateau during the growing seasons from 2011 to 2013. Our results showed that winter grazing significantly raised soil temperature (ST), while grazing exclusion (E) had no effect on soil moisture (SM), and N fertilizer (F) had no effect on ST or SM. Aboveground biomass (AB) and root biomass (RB) were not significantly affected by E in 2011-2013 (p > 0.05), but F significantly affected AB and RB (p < 0.05). Compared with winter grazing, only E substantially reduced seasonal mean CO₂ emissions (by about 20.1%) during the experimental period. E did not significantly directly affect CH₄ uptake, whereas N addition reduced seasonal mean CH₄ uptake by about 6.5%, and N addition changed seasonal average absorption of N₂O into an emission source. CO₂ flux is the major contributor to CO₂ equivalent emissions in this area. Our results indicate that exclosure from livestock grazing might be a promising measure to reduce CO₂ emissions, while enhanced N addition might reduce CH₄ uptake and increase N₂O emission in the alpine meadow under future climate change.

中文翻译：

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添加和放牧对青藏高原高寒草甸CO 2，CH 4和N 2 O通量的影响

对增强氮（N）和放牧排除（E）对草原温室气体通量（GHGs：CO ₂，CH ₄和N ₂ O）的影响的有限了解限制了我们应对未来气候变化挑战的能力。在这项研究中，我们使用静态不透明密闭室进行了田间试验，以研究温室气体通量对氮添加（69 kg N ha - ¹ 年^-1在2011年至2013年的生长季节中，在青藏高原的高寒草甸进行了3次分裂）和放牧排除。我们的结果表明，冬季放牧显着提高了土壤温度（ST），而放牧排除（E）对土壤没有影响水分（SM）和氮肥（F）对ST或SM没有影响。地上生物量（AB）和根系生物量（RB）在2011-2013年不受E显着影响（p  > 0.05），但F显着影响AB和RB（p  <0.05）。与冬季放牧相比，在实验期间，只有E大大减少了季节性平均CO ₂排放量（约20.1％）。E不会显着直接影响CH _4的摄取，而氮的添加会降低季节性平均CH ₄氮的吸收量约为6.5％，氮的添加改变了N ₂ O向排放源的季节性平均吸收。CO ₂通量是该区域中CO ₂当量排放的主要贡献者。我们的结果表明，放牧对牲畜放牧可能是减少CO ₂排放的一种有前途的措施，而增加N的添加可能会在未来气候变化的情况下降低高寒草甸CH _4的吸收并增加N ₂ O的排放。