黄土台塬不同林型土壤主要温室气体通量特征

Characteristics of soil greenhouse gas fluxes under different forest types in the Loess Plateau tableland,China

为研究纯林、混交林土壤二氧化碳(CO_2)、甲烷(CH_4)和氧化亚氮(N_2O)排放特征,有效评估不同林型组成所产生的温室气体差异。本文以黄土台塬7种典型纯林及其混交林为研究对象,采用静态箱-气相色谱法,比较各林型土壤CO_2、CH_4和N_2O的排放规律及其对环境因子的响应。结果表明:研究区各林型土壤均为CO_2、N_2O的排放源,CH_4的吸收汇。不同林型土壤温室气体排放差异显著,在土壤CO_2年均排放中,沙棘刺槐混交林最高(130.73 mg·m^(-2)·h^(-1)),油松最低(51.33 mg·m^(-2)·h^(-1));在土壤CH_4年均吸收中,油松最高(60.82μg·m^(-2)·h^(-1)),侧柏最低(36.67μg·m^(-2)·h^(-1));在土壤N_2O年均排放中,沙棘刺槐混交林最高(4.42μg·m^(-2)·h^(-1)),油松最低(-0.06μg·m^(-2)·h^(-1))。各林型土壤CO_2与土壤温度呈正相关,与土壤含水量呈负相关;侧柏和沙棘刺槐混交林土壤CH_4吸收与土壤温度呈正相关,随0～5 cm土壤含水量的增加呈先增加后减少的规律;刺槐和油松土壤N_2O与土壤温度为显著正相关,其他林型与土壤温度及含水量无明显相关性。研究表明:土壤温室气体排放与林型组成有关,受环境因子影响,各温室气体表现出不同的排放特征。

The study of characteristics of CO2, CH4,and N2O fluxes in soils of pure forest and mixed forest has great significance for evaluat. ing the differences in greenhouse gas fluxes under different forest types. In this study, the flux laws and major influential factors of CO2, CH4, and N2O were compared using a static chamber and gas chromatography method based on seven typical pure forests and their mixed forests in the Loess Plateau tableland. The results showed that all forest types were sources of CO2 and N2O and sinks of CH4, and the differ. ences in greenhouse gas fluxes among different forest soils were significant. Among the annual fluxes of soil CO2 and N2O, the mixed forest of Hippophae rhamnoides and Robinia pseudoacacia had the highest fluxes(130.73 mg·m^-2·h^-1 and 4.42 μg·m^-2·h^-1, respectively), while the Pinus tabuliformis pure forest(51.33 mg·m^-2·h^-1 and -0.06 μg·m^-2·h^-1, respectively)had the lowest. For the fluxes of soil CH4 uptake, the absorption flux of the P. tabuliformis pure forest was higher(60.82 μg·m^-2·h^-1)than that of any other forest, and that of the Biota orien. talis pure forest(36.67 μg·m^-2·h^-1)was the lowest. The soil CO2 flux was positively correlated with soil temperature and negatively correlated with soil moisture content. Soil CH4 uptakes of the B. orientalis pure forest and mixed forest of H. rhamnoides and R. pseudoacacia were significantly positively correlated with temperature, and first increased and then decreased with the increase in 0~5 cm soil water content. Only the R. pseudoacacia pure forest and P. tabuliformis pure forest soil N2O fluxes were positively correlated with soil temperature. The results showed that the fluxes of greenhouse gases in soil were related to forest type, and that the flux characteristics were different under the influence of environmental factors.