剔除林下灌草和添加翅荚决明对尾叶桉林土壤温室气体排放的影响

EMISSIONS OF SOIL GREENHOUSE GASES IN RESPONSE TO UNDERSTORY REMOVAL AND CASSIA ALATA ADDITION IN AN EUCALYPTUS UROPHYLLA PLANTATION IN GUANGDONG PROVINCE,CHINA

森林土壤是CO2、CH4和N2O等温室气体的重要排放源。采用静态箱/色谱分析技术对中国科学院鹤山丘陵综合开放试验站的尾叶桉(Eucalyptus urophylla)林土壤CO2、CH4和N2O排放通量进行了原位测定,研究剔除林下灌草和添加翅荚决明(Cassiaalata)对尾叶桉林土壤温室气体排放的影响。结果表明:尾叶桉林土壤CO2排放通量在湿季维持在较高水平,在旱季则明显降低。CH4和N2O在湿季波动幅度较大,在旱季则相对稳定。土壤CO2和CH4通量峰值均出现在湿季,但N2O峰值出现在旱季的12月。尾叶桉林土壤在不同处理下可能是CH4的源,也可能是CH4的汇,而对于CO2和N2O则主要是源。尾叶桉林下剔除灌草及添加翅荚决明能显著增大土壤CO2和N2O的排放,但林下灌草剔除后有利于CH4的吸收,添加翅荚决明有利于CH4的排放。表层土壤温度和湿度是影响土壤温室气体排放的首要因子。呼吸底物(氮源)和土壤微生物量也是影响土壤温室气体排放的重要因子。

Aims CO2,CH4 and N2O are important greenhouse gases,and they mainly come from soils in forest ecosystems. Our objective was to analyze the effects of removal of the understory and ad-dition of Cassia alata on soil CO2,CH4 and N2O emissions in Heshan Hilly Land Interdisciplinary Ex-perimental Station,Chinese Academy of Sciences,Guangdong Province,China. Methods CO2,CH4 and N2O fluxes in a Eucalyptus urophylla plantation were measured in situ using the static chamber technique from June 2007 to May 2008. Important findings CO2 fluxes stayed at a relatively high level during the rainy season and a lower level in the dry season,while CH4 and N2O fluxes varied widely in the rainy season and were stable in the dry season. Peak values of CO2 and CH4 appeared in the rainy season,while the peak value of N2O flux was in the dry season （December）. The E. urophylla plantation soil was a sink or source for CH4 while consistently a source for CO2 and N2O. Understory removal and C. alata addition significantly enhanced CO2 （p0.01） and N2O fluxes （p0.01）,while decreasing or increasing CH4 fluxes under the same treatments. Results indicated that soil temperature,soil moisture,NO3-N and microbial biomass carbon （MBC） might be important variables for soil CO2,CH4 and N2O fluxes.