Characteristics of annual greenhouse gas flux and NO release from alpine meadow and forest on the eastern Tibetan Plateau

编号 030019101

推送时间 20190617

研究领域 森林经理 

年份 2019 

类型 期刊 

语种 英语

标题 Characteristics of annual greenhouse gas flux and NO release from alpine meadow and forest on the eastern Tibetan Plateau

来源期刊 AGRICULTURAL AND FOREST METEOROLOGY

期 第191期

发表时间 20190408

关键词 Alpine ecosystem;  Meadow;  Forest;  Non-CO2 greenhouse gas;  Nitric oxide; 

摘要 The importance of the world's largest plateau (i.e., the Tibetan Plateau) as a source/sink for atmospheric greenhouse gases (GHGs) still remains uncertain as field observations covering entire years and contrasting ecosystems are scarce. Here we report on year-round measurements of methane (CH4), nitrous oxide (N2O) and nitric oxide (NO) fluxes from two representative ecosystems (cattle-grazed meadow and natural forest, >3300 m a.s.l) on the eastern Tibetan Plateau. In our study, the alpine soils generally functioned as sinks for atmospheric CH4. The pronounced seasonality of CH4 uptake, with higher uptake in the growing season and lower uptake in the non-growing season, was mainly regulated by the combined changes in soil moisture and temperature. Soil CH4 uptake was lower at the meadow site due to high soil moisture and grazing-induced soil compaction reducing gas diffusivity and hampering CH4 uptake. For the alpine meadow pulses of N-oxide fluxes were observed during the freeze-thaw period, while freeze-thaw related pulses did not occur at the forest site, where the seasonality of N-oxide fluxes was primarily regulated by changes in soil temperature (Q(10) = 3.0). Annual cumulative fluxes for the meadow and forest ecosystems ranged between -1.15 and -2.24 kg CH4-C ha(-1) yr(-1), 0.13-0.65 kg N2O-N ha(-1) yr(-1) and 0.022-0.047 kg NO-N ha(-1) yr(-1). Non-growing season fluxes contributed 34-45% and 21-51% to the annual budgets of CH4 and N-oxides, respectively. Multiple regression analyses showed that soil N-oxide fluxes were significantly positively correlated to concentrations of soil dissolved organic C (DOC) and inorganic N, with DOC and inorganic N concentrations being higher at the forest site. Our study also shows that alpine forest is a stronger source for non-CO2 GHGs relative to alpine meadow (higher by 195 kg CO2-eq ha(-1) yr(-1)). This difference in GHG fluxes significantly offsets the net climate benefits due to increased C-sequestration associated with afforestation/reforestation.
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