秦岭火地塘林区不同海拔森林土壤NO通量

选取秦岭火地塘林区不同海拔(1 560~2 160 m)的有代表性的5个森林样地,从2014年10月到2015年10月对其土壤NO通量采用静态箱—氮氧化物分析仪法进行1 a的监测。结果表明,土壤NO排放主要集中在植物生长季(2015年5月—2015年9月),但整个观测期NO排放保持在较低水平。在非生长季(2014年10月—2015年4月),大部分样地的NO排放先减少后增加,而且监测有NO吸收。不同海拔NO年排放总量分别为2 160m红桦林0.06 kg·ha~(-2)·a~(-1),2 040 m青杄林0.08 kg·ha~(-2)·a~(-1),1 963 m华山松林0.02 kg·ha~(-2)·a~(-1),1 585 m油松林0.11 kg·ha~(-2)·a~(-1),1 560 m锐齿栎林0.19 kg·ha~(-2)·a~(-1)。除华山松外,NO年排放总量随海拔的升高而减少。不同海拔5个样地土壤NO通量均与地温显著相关(P0.05)。华山松林土壤NO排放与土壤孔隙充水率呈负相关(P0.05)。油松林土壤NO排放与土壤铵态氮质量分数负相关(P0.05)。除油松林外,各样地的土壤孔隙充水率都低于60%,可以推断,硝化反应是本地区NO的重要生成源,但受到降雨和土壤有机质等理化性质的影响又伴随有反硝化过程。

NO Flux in Forest Soil at Different Elevation of Huoditang Area in the Qinling Mountains

We reported the results of continuous measurements of NO emissions at different elevation(1560-2160m)from Huoditang Area in the Qinling Mountains from October 2014 to October 2015 by using the static chamber technique and NOx analyzer(ML 9841 B Nitrogen Oxides Analyzer).The majority of NO fluxes occurred during growing season from May 2015 to September 2015,but NO emitted at a low level.During non-growing season from October 2014 to April 2015,NO emission in most of the sample plots was decreased first and then increased,and NO uptake was found during the detecting period.Annual NO fluxes were 0.14kg·ha-2·a-1 at 1560m,0.22kg·ha-2·a-1 at 1585m,0.02kg·ha-2·a-1 at 1963m,0.13kg·ha-2·a-1 at 2040m,and 0.06kg·ha-2·a-1 at 2160m.Annual NO fluxes were decreased with increasing altitude except for the Pinus armandii forest.Across elevations,NO fluxes were significantly correlated with soil temperature(P<0.05).NO emission in the P.armandii forest(1963m)was negatively correlated with WFPS(P<0.05).NO emission in the P.tabulaeformis forest(1585m)was negatively correlated with NH+4 concentrations(P<0.05),while the rest were not related.Soil WFPS in all sampling pots was always below 60％except for the P.tabulaeformis forest(1963m),suggesting that nitrification was the important source of NO in this region.But the denitrification was accompanied with the influence of precipitation and soil physicochemical properties.