摘要
森林土壤呼吸是全球碳循环的重要流通途径之一 ,其动态变化将直接影响全球 C平衡。森林土壤呼吸由自养呼吸和异养呼吸组成 ,不同森林类型、测定季节和测定方法等直接影响其所占比例。土壤温度和湿度是影响森林土壤呼吸的最主要因素 ,共同解释了森林土壤呼吸变化的大部分。因树种组成、生产力和枯落物数量等不同而使不同森林类型土壤呼吸速率表现出明显差异。采伐对森林土壤呼吸的影响结果有增加、降低或无影响 ,因采伐方式、森林类型、采伐迹地上植被恢复进程和气候条件等而异。火烧一般导致土壤呼吸速率降低。因肥料种类、施用剂量和立地条件不同 ,施肥对森林土壤呼吸的影响出现增加、降低或无影响等不同结果。大气 CO2 浓度升高和升温均可促进森林土壤呼吸。 N沉降有可能刺激了土壤呼吸 ,而酸沉降则可能降低了土壤呼吸。臭氧浓度和 UV-B辐射强度亦会在一定程度上影响森林土壤呼吸。但目前全球变化对森林土壤呼吸的综合影响尚不清楚 ,深入探讨森林土壤呼吸的调控因素及其对全球变化和营林措施的响应等仍是今后努力的主要方向。
Soil respiration in forest ecosystems is one of the major pathways of C flux in the global C cycle, second only to the gross primary productivity, and is markablely affected by the global change. The review summarized the important role of forest soil respiration in global carbon cycle, its components, its controlling factors, and its response to the global change. Forest soil respiration is the sum of heterotrophic (microbes, soil fauna) and autotrophic (root) respiration. The contribution of each group needs to be understood to evaluate the implications of environmental changes on soil carbon cycling and carbon sequestration. There is a large variation in the relative contributions of autotrophic and heterotrophic respiration to total soil CO_2 efflux, and the estimated contributions from root respiration range from 10% to as high as 90%. Some of this variation may come from differences in methodology and from differences in forest and soil types. The critical factors influencing forest soil respiration include soil temperature, soil moisture, forest types (substrate quality, net ecosystem productivity, the relative allocation of NPP above- and belowground) and forest management (land-use and/or disturbance regimes, fertilization). The temperature effect is always described as an exponential function. The effect of soil moisture, in contrast, has been described by numerous equations including linear, logarithmic, quadratic, and parabolic functions. Soil respiration is frequently maximized when soil is at an intermediate water content. Soil temperature and soil humidity together explain a large part of variations in soil respiration. Forest types may affect soil respiration by influencing the soil microclimate and structure, the quantity and quality of substrate, and the overall rate of root respiration. At the global scale, soil respiration rates in forests are correlated positively with litterfall rates. Despite this complex array of factors that affect forest soil respiration, soil respiration is typically modeled either as a simple Q_(10) function or as a step relationship based on temperature response curves. Harvest cutting could stimulate, suppress, or show no effect on soil respiration, depending on harvest methods, forest types, speed of regeneration and climate conditions. Slash burning usually decrease soil respiration rate. Fertilization might enhance, reduce or show no effects on soil respiration, depending on fertilizer types, loading levels and site conditions. The elevated atmospheric CO_2 could increase the eflux of CO_2 from soils, while simultaneously leaving a greater store capacity of carbon in the soil. Rising temperature increases the eflux of CO_2 from soils with a net release of soil carbon and, thus, will further global warming. Nitrogen deposition may promote the sequestration of carbon in vegetation and soils. The integrated effects of these global changes is unknown yet, but it seems unlikely to mitigate the rise of atmospheric CO_2 in this century through a large increase in the soil carbon pool. Ozone concentration and radiant intensity of UV-B could somehow influnce soil respiration directly or indirectly. Despite intensive researches in recent years, there still need some efforts before we can make an understanding of the interactions between global changes and forest soil respiration: (1) developing appropriate methods for separating various components of soil respiration; (2) implementing long-term in situ research on the effects of anthropic disturbance, particularly those of intensive disturbances (e.g. clearcutting, fire); (3) understanding mechanisms on responses of forest soil respiration to global changes in different climatic zone; (4) developing techniques for the data to scale up from a small chambers to a stand or ecosystem level, and even to a regional or global level; and (5)establishing a global research network on forest soil respiration and perfecting the global CO_2 FLUX web.
出处
《生态学报》
CAS
CSCD
北大核心
2004年第3期583-591,共9页
Acta Ecologica Sinica
基金
高等学校优秀青年教师教学科研奖励计划资助项目
福建省重大基础研究资助项目 ( 2 0 0 0 F 0 0 4 )~~
