剔除杂草对山核桃林地土壤温室气体排放的影响

Effects of understory removal on soil greenhouse gas emissions in Carya cathayensis stands

森林土壤是CO2、N2O和CH4等温室气体的重要排放源,山核桃是中国特有的高档干果和木本油料树种,林下杂草管理对山核桃林地温室气体排放具有重要影响.采用静态箱-气相色谱法在浙江临安山核桃主产区进行了为期1年的原位试验,研究剔除林下杂草对山核桃林地土壤温室气体排放的影响.结果表明:剔除杂草和留养杂草山核桃林地土壤CO2排放通量呈现一致的季节变化规律:夏秋季高、冬春季低;N2O排放在夏季较高,其他季节变化平稳;CH4的排放无明显季节变化规律.剔除杂草显著降低了土壤CO2排放,促进了N2O排放和CH4吸收.剔除杂草对土壤水溶性有机碳和微生物生物量碳没有显著影响.剔除杂草的山核桃林地土壤排放温室气体的综合增温潜势为15.12 t CO2-e·hm-2·a-1,显著低于留养杂草处理(17.04 t CO2-e·hm-2·a-1).

CO2,N2 O and CH4 are important greenhouse gases,and soils in forest ecosystems are their important sources. Carya cathayensis is a unique tree species with seeds used for high-grade dry fruit and oil production. Understory vegetation management plays an important role in soil greenhouse gases emission of Carya cathayensis stands. A one-year in situ experiment was conducted to study the effects of understory removal on soil CO2,N2 O and CH4 emissions in C. cathayensis plantation by closed static chamber technique and gas chromatography method. Soil CO2 flux had a similar seasonal trend in the understory removal and preservation treatments,which was high in summer and autumn,and low in winter and spring. N2 O emission occurred mainly in summer,while CH4 emission showed no seasonal trend. Understory removal significantly decreased soil CO2 emission,increased N2 O emission and CH4 uptake,but had no significant effect on soil water soluble organic carbon and microbial biomass carbon. The global warming potential of soil greenhouse gases emitted in the understory removal treatment was 15.12 t CO2-e·hm^-2·a^-1,which was significantly lower than that in understory preservation treatment（ 17.04 t CO2-e·hm^-2·a^-1）.