不同干扰因素对森林和湿地温室气体通量影响的研究进展

森林和湿地是CO2、CH4和N2O等温室气体重要的源、汇和转换器,在全球气候变化过程中起着重要作用。森林和湿地温室气体通量受到诸多因子的作用,其中干扰便是一个重要的因素。不同干扰因素对于森林和湿地生态系统温室气体通量的影响,国际上已经开展了相应的研究。基于人为和自然两大类干扰方式,分别从采伐、施肥、垦殖等人为干扰因素和火烧、台风(飓风)等自然干扰因素综述了干扰对于森林和湿地生态系统CO2、CH4和N2O通量的影响。根据目前研究中存在的不足,提出了今后应需加强的领域,以期更好地揭示干扰对于森林和湿地生态系统温室气体通量的影响及作用机制,为今后深入开展相关研究提供一定的参考价值。

Greenhouse gas flux from forests and wetlands: a review of the effects of disturbance

Forest and wetland ecosystems are significant carbon and nitrogen sinks at the global scale, and play an important role sequestering greenhouse gases and regulating climate. The three greenhouse gases fluxes from forest and wetland ecosystems are influenced by many factors,including disturbance. Here, we review the effects of disturbance on greenhouse gases fluxes from forest and wetlands. We separate the effects due to disturbance into two types: disturbance brought about by human activity and through natural means. The former includes forest-harvesting, fertilization, reclamation and tillage, and the latter includes fire, typhoon and hurricane. We discuss the impacts of these different disturbances on the fluxes of CO₂, CH₄ and N₂O from both forest and wetland ecosystems. In many cases the conclusions from the literature were not consistent. Harvesting increased forest soil respiration in most studies; however, there was also one report showing that soil respiration dropped markedly because of a reduction in carbon input after forest removal. The response of three greenhouse gases to harvesting was also not consistent. Reclamation, a major disturbance in wetlands, tended to produce large impacts on the carbon and nitrogen dynamics. Some studies demonstrated an increased CO₂ emission when marshlands were transformed to farmland, whereas another reports concluded that marsh reclamation caused the drop in CO₂ emission. CH₄ flux often decreased, and N₂O flux generally increased when the marshes were reclaimed. The effects of fertilizer nitrogen input on greenhouse gases production and emission from marshes soil were complex with differences induced by different nitrogen fertilizers (NH₄NO₃, (NH₄)₂SO₄, KNO₃ and urea). The intensity of fire appeared to have an important influence on CH₄ flux; a low-intensity fire increases CH₄ flux, whereas a high-intensity fire will decrease CH₄ flux. The CO₂ flux-responses were also complex; some studies showed that fire inhibited CO₂ flux, but others showed promotion effects. Tropical storms (typhoons and hurricanes) are a common disturbance feature in tropical and subtropical coastal forest and wetland ecosystems. CO₂ emission generally dropped after the storm and N₂O flux often increased.We concluded our review with an analysis of trends in current research, and pointed out some urgent and key directions in future. A major suggestion was that it is becoming increasingly necessary to understand the mechanism through which the different types of disturbance influence greenhouse gases fluxes from forest and wetland ecosystems, and in particular to assess the effects at different spatial and temporal scales.