根系和凋落物去除对3种人工林土壤CO_(2)通量日变化的影响

Effect of root and litter removal on diurnal variation of soil CO_(2) flux in 3 typical coastal plantations

[目的]探究不同碳输入下,滨海人工林林地CO_(2)通量的昼夜动态变化和土壤CO_(2)的日排放量。[方法]采用Li-8100碳通量自动测量系统对尾巨桉、纹荚相思、湿地松3种滨海人工林土壤CO_(2)排放速率进行了监测,同时测定了0~10 cm土层土壤温湿度。[结果]土壤CO_(2)通量日变化幅度较小,尾巨桉和纹荚相思林地白天土壤的CO_(2)排放量高于夜晚,湿地松林地则相反。非生长季纹荚相思和尾巨桉、湿地松林地土壤CO_(2)通量日动态变化均存在显著差异(P<0.05),生长季不同人工林间的土壤CO_(2)通量日动态变化均存在显著差异(P<0.05);非生长季3种人工林去除根系或凋落物后土壤CO_(2)通量降低幅度较小,而生长季去除根系或凋落物后土壤CO_(2)通量均显著降低(P<0.05)。土壤CO_(2)通量与土壤温度呈指数相关关系,土壤CO_(2)通量与土壤湿度呈二次曲线相关关系。[结论]林地土壤CO_(2)排放量因树种和季节而异,土壤CO_(2)通量对根系或凋落物去除的响应也有差异,与植物根系、凋落物输入的数量和质量以及土壤温湿度的影响有关。

[Purpose]The study aimed to explore the diurnal variation of soil CO_(2) flux in coastal shelterbelts under different carbon inputs.[Method]Soil CO_(2)emission rates under 3 types of coastal shelterbelt plantations,including Eucalyptus urophylla×E.grandis,Acacia aulacocarpa and Pinus elliottii,were monitored using Li-8100 automated soil CO_(2) flux measurement system,together with soil temperature and humidity at the depth of 0-10 cm.[Result]The results showed that the diurnal variation of soil CO_(2) flux was overall slight in the study area.E.urophylla×E.grandis and A.aulacocarpa plantations had greater soil CO_(2) emissions in the daytime than the nighttime,but it was the opposite situation in P.elliottii plantation.During the non-growing season,A.aulacocarpa plantation differed significantly from E.urophylla×E.grandis and P.elliottii regarding the diurnal variation of soil CO_(2) flux(P<0.05),while all the 3 plantations differed significantly from each other during the growing season(P<0.05).After being removed with root or litter,soil CO_(2) fluxes were slightly reduced during the non-growing season,while the reductions were significantly higher during the growing season(P<0.05).Generally,daily soil CO_(2) flux followed an exponential function with soil temperature,and a quadratic function between soil humidity.[Conclusion]Tree species and growing season were 2 factors influencing the rates of soil CO_(2) emissions from coastal plantations,and how it changed in response to root or litter removal was also different,which was related to plant root system,quantity and quality of litter input,and its effect on soil temperature and humidity.