气候暖化对解冻期不同纬度兴安落叶松林土壤氧化亚氮释放的影响

Effects of climate warming on the N_2O emission from Larix gmelinii forest soils at different latitudes during soil thawing period

春季解冻期北方森林土壤释放出大量的N2O,是大气温室气体的主要来源之一.本研究将分布于塔河(52°31′N)、松岭(50°43′N)、孙吴(49°13′N)和带岭(47°05′N)4个纬度上林分状况相似的兴安落叶松林样地(包括幼树、地被物和A、B层土壤)移置至其自然分布区南缘,模拟气候暖化,分析春季解冻期土壤N2O通量的时间动态及其影响因子.结果表明:各处理的土壤N2O释放高峰均出现在解冻中后期.带岭、孙吴、松岭和塔河样地土壤解冻期的土壤N2O平均通量分别为(66.5±9.3)、(54.3±5.6)、(44.3±5.3)和(33.5±3.7)μg.m-2.h-1;土壤N2O通量与5cm土壤温度和0～10cm土壤微生物生物量碳呈显著正相关,但与土壤含水率的相关性不显著.解冻期4个处理的土壤N2O释放差异显著,其平均通量和累积释放量均随纬度升高而下降.这种差异主要是由于不同纬度土壤的微生物活性和土壤物理性质的差异引起的.

During the soil thawing period in spring, large amount of N2O was emitted from the forest soils in North China, being a major source of atmospheric greenhouse gases. However, the contribution of the emitted N2O and its responses to climatic change are unclear. In this paper, sampling plots of Larix gmelinii forest （including sapling, ground vegetation, and soil A and B horizons） with similar stand conditions in Tahe （52°31′ N）, Songling （50°43′ N）, Sunwu （49°13′N）, and Dailing （47°05′N ） were displaced to the south boundary of L. gmelinii natural distribution area to simulate that the plots were under climate warming, and their N2O fluxes were measured during the soil thawing period in spring 2007. For the four plots, the N2O fluxes all peaked at the midor late stage of soil thawing. The N2O flux of the plots from Dailing, Suwu, Songling, and Tahe during soil thawing period was averagely 66. 5 ± 9. 3, 54.3± 5.6, 44. 3 ±5.3, and 33.5±3.7 μg·m^-2·h^-1, respectively, and significantly positively correlated to the soil temperature at 5 cm depth and the soil microbial biomass carbon at 0-10 cm depth. No significant relationship was observed between the N2O flux and soil moisture content. The soil N2O emission during soil thawing period differed significantly among the plots. Both the mean N2O flux and the cumulative N2O emission decreased with increasing latitude, mainly due to the differences in soil microbial activities and soil physical properties.