植被覆盖变化过程中土壤有机碳库动态及其影响因素研究进展

土地利用和土地变化改变了1/3~1/2的陆地面积。森林砍伐、造林、木本入侵等植被变化通常伴随草本、木本植物类型的改变,是植被变化的主要表现形式。通常认为森林破坏导致土壤有机碳(SOC)流失,也有研究发现,林地转化为草场后也可具有极大的碳增汇潜力。由于农田、草场是人类主要食物来源地,比较研究草本与木本植被类型的土壤碳吸存潜力及影响因素对全球变暖和食物安全都具有重要意义。本研究综述了国内外近年来的有关研究进展,结果表明,植被变化过程中SOC的变化方向和数量大小不仅取决于变化前后植被类型,还主要与土地利用的历史、现状及管理活动强度有关。另外,原始土壤条件、土地利用变化前SOC含量、土壤质地、植被生产力等也都对SOC动态具有重要影响。这为特定立地条件下选择相应的植被类型或植被类型组合,进行有效的管理以提高土壤碳吸存提供了依据。目前许多关于植被变化的研究并没有把植被类型转换对土壤碳库的影响从其他因子的影响中分离出来,对2种植被类型下土壤碳库特征、碳汇潜力、动态特征以及影响因子的比较研究有待进一步深入,关于土壤活性碳库动态特征及影响因素的研究也有待加强。

Review of soil organic carbon dynamic progress and the impact factors during herbaceous and woody vegetation types conversation

About one-third to one-half of the land surfaces have been transformed by land-use and land-cover change.Deforestation,afforestation,and woody plant encroachment are the main forms of vegetation change,which are always accompanied with shifting of the abundance of woody and herbaceous vegetation types(e.g.,grasses,shrubs,and trees).Generally,deforestation was thought to induce soil organic carbon loss.However,some research has indicated that farms transformed from forest sequestrated more soil organic carbon.Because farm and pasture are the main source of peoples food,comparing the carbon carrying capacity of the two different vegetation types(herbaceous vs.woody) was important both to globe climate warming and food safety.Results of recent research suggested that,after the transformation of vegetation type,whether the soil sequestrated or lost carbon and by how much depended not only on vegetation types before and after the transformation but also intensity of land management and the history and actuality of land use.Soil texture and plant productivity have an important effect on carbon sequestratation.Therefore for a given condition,selecting the correct vegetation types or combinations and improving the level of land management are both useful for improving soil organic carbon sequestration.So far,there is little research to separate the impact of vegetation type on soil organic carbon sequestration from other factors,so soil organic carbon characteristics,soil carbon carrying capacity,carbon turnover dynamics,and the impact factors of carbon sequestration under the two vegetation types need more work.Labile carbon is the more sensitive carbon fraction to land use and land cover change,and should receive more attention.