作 者 ：孙敬松,周广胜*,韩广轩
期 刊 ：生态学报 2010年 30卷 21期 页码：5925~5932
关键词：土壤呼吸；太阳辐射；散射辐射；土壤温度；生物因子；玉米；
Keywords:soil respiration, solar radiation, diffuse radiation, soil temperature, biological factors, maize(Zea mays L.),
摘 要 ：水热因子通常被认为是影响土壤呼吸作用的主导因子。对2004-2005年东北地区玉米农田土壤呼吸作用的观测资料分析表明：太阳辐射对土壤呼吸作用有促进作用，使得白天的土壤呼吸速率高于夜间，并导致土壤呼吸作用与土壤温度的关系发生变化。太阳总辐射对玉米（Zea mays L.）生长后期的土壤呼吸作用具有显著影响（9月7日:R2＝0.80，P＜0.0001；9月29日:R2＝0.82，P＜0.0001）。地上生物量和叶面积指数制约着太阳总辐射对土壤呼吸作用的贡献，可解释太阳总辐射与土壤呼吸作用关系变异的83.5%。在玉米生长初期，散射辐射间接地促进了土壤呼吸作用，但随着叶面积指数的增加，散射辐射的透射作用减弱，使得直射辐射对土壤呼吸作用的影响超过散射辐射；进入玉米生长后期，由于叶子枯黄，叶面积指数减小，散射辐射又对土壤呼吸起到促进作用。
Abstract:Soil moisture and temperature are often regarded as main controlling factors of soil respiration. This paper analyzed different responses of soil respiration to solar radiation during daytime and nighttime, based on the observing data of soil respiration and its corresponding environmental factors in a maize ecosystem during growing seasons in 2004 and 2005. The results indicated that total solar radiation could enhance soil respiration. Solar radiation enhanced leaf photosynthesis of maize (Zea mays L.) during daytime, which lead to more photosynthetic product being carried to roots so as to promote soil respiration indirectly, and finally resulted in higher soil respiration rates during daytime than nighttime under the same temperature. Thus, solar radiation could induce the change of the relationship between soil respiration and soil temperature. There was significant exponential relationship between soil respiration rate and 5cm soil temperature during nighttime, but at late growth stage, the exponential relationship between soil respiration and soil temperature was not obvious during daytime. During daytime, soil respiration enhanced with 5cm soil temperature increasing, but to a certain extent, soil respiration decreased with 5cm soil temperature increasing. Total solar radiation had significant effect on soil respiration at late growth stage (September 7th: R2＝0.80, P＜0.0001; September 29th: R2＝0.82, P＜0.0001). Further studies showed that aboveground biomass and leaf area index controlled the effects of soil temperature on soil respiration of the maize ecosystem, and these could explain about 83.5% of the variation of the relationship between soil temperature and soil respiration. The effects of solar radiation on soil respiration were different with the seasonal variations of biomass and leaf area index (LAI). The increase of biomass could strengthen the indirect effects of solar radiation on soil respiration, but with the increase of biomass and LAI increased to a certain level, leaves of the maize ecosystem would shelter solar radiation from inner maize canopy, and decreased the whole community photosynthesis, which could indirectly reduce soil respiration. The increments of biomass were helpful to improve the indirect effects of solar radiation on soil respiration rate. However, extremely high LAI could produce negative influence on soil respiration. This was one of the main reasons that at late growth stage, total solar radiation had significant effect on soil respiration with LAI decreasing. Diffuse radiation could penetrate more into inner canopy, which not only improved the whole community photosynthesis and indirectly increased soil respiration, but also increased soil temperature and promoted soil microorganism activities, thus resulted in the increase of soil heterotrophic respiration under lower canopy density (early and late growth stages), therefore, effects of diffuse radiation on soil respiration were more than direct radiation did. But with the increase of LAI (vigorous growth period), because of high canopy density (high LAI), sheltering almost influenced total radiation (direct and diffuse radiation), the penetration effect of diffuse radiation would be reduced. Because the effects of direct radiation on leaf photosynthesis of canopy crown were more than diffuse radiation, and enhanced more of soil respiration indirect effect, made the effect of direct radiation on soil respiration higher than that of diffuse radiation. At late growth stage, leaf withered and yellow result in LAI decreasing, diffuse radiation enhanced soil respiration again. In this paper, nonlinear regression equation was used to analyze the relationship between soil respiration rate and soil temperature, solar radiation (direct and diffuse radiation), and linear regression equation apply to analyze the relationship between the parameters of nonlinear regression and biomass or LAI.
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