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中国亚热带人工林处于全球氮沉降高值区,土壤氮素相对富集,土壤氧化亚氮(N_2O)产生与排放对外源性氮素输入响应敏感。然而,现有氮沉降模拟控制实验多采用单一氮肥类型,没有原位区分氧化态氮与还原态氮素影响的差异。以千烟洲亚热带湿地松林为研究对象,增氮控制实验采用随机区组设计,包括2种形态(NO_3~-、NH_4~+)和3个施氮水平(0、40、120 kg hm~(-2) a~(-1))。利用静态箱—气相色谱法高频(8次月~(-1))测定土壤N_2O净交换通量以及温度、水分、溶解性氮含量等相关环境变量,分析土壤N_2O通量对外源性氮素输入的响应特征及主控因子。结果表明:施氮不影响亚热带人工林土壤温度和水分,显著增加了土壤NO_3~--N、NH_4~+-N和总溶解性氮(TDN)的含量,对溶解性有机氮(DON)含量无显著影响。施氮显著促进亚热带人工林土壤N_2O排放,增幅为378%~847%,施加NH4Cl的促进效应显著高于Na NO_3。土壤N_2O通量与10 cm土壤温度、10 cm土壤体积含水量呈正相关,土壤N_2O通量的变化量与土壤无机氮含量的变化量呈正相关。上述研究结果表明,虽然水热因子驱动着亚热带人工林土壤N_2O的排放,但是氮素富集条件下土壤N_2O的增加主要由底物可利用性的变化所致,并且还原态NH_4~+的促进效应显著高于氧化态NO_3~-。
The subtropical plantations in China are in a high value area of global nitrogen deposition, and the soil nitrogen is relatively enriched. The production and emission of soil nitrous oxide (N 2 O) are sensitive to the exogenous nitrogen inputs. However, the existing nitrogen deposition simulation control experiments mostly adopt a single type of nitrogen fertilizer, and there is no difference between the in situ oxidation of oxidized nitrogen and the reduced nitrogen. Taking Qianyan subtropical wetland pine forest as the research object, the experiment of increasing nitrogen control was designed by random block design including two forms (NO_3 ~ -, NH_4 ~ +) and three nitrogen application levels (0, 40, 120 kg hm ~ -2) a ~ (-1)). The net exchange fluxes of N_2O and the related environmental variables such as temperature, moisture and dissolved nitrogen content were determined by static box-gas chromatography (8 times monthly -1), and the effects of soil N_2O flux on the exogenous nitrogen Enter the response characteristics and master factor. The results showed that nitrogen application did not affect the soil temperature and water content in subtropical plantations, and significantly increased the content of NO_3 ~ -N, NH_4 ~ + -N and total dissolved nitrogen (TDN) in soils. The contents of dissolved organic nitrogen (DON) No significant effect. Nitrogen application significantly promoted soil N 2 O emission in subtropical plantations, with an increase of 378% -847%. The promotion effect of application of NH 4 Cl was significantly higher than that of NaNO 3. Soil N 2 O flux was positively correlated with 10 cm soil temperature and 10 cm soil water content, and soil N 2 O flux was positively correlated with soil inorganic nitrogen content. The results of the above studies show that, although hydrothermal factors are driving soil N 2 O emission in subtropical plantations, the increase of N 2 O in soil is mainly caused by the change of substrate availability, and the promotion of reduced NH 4 + The effect was significantly higher than the oxidation state NO_3 ~ -.