Hydrological functions of tropical forests: not seeing the soil for the trees?
Hydrological functions of tropical forests: not seeing the soil for the trees?
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DOI：
10.1016/j.agee.2004.01.015
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发表时间：
2004-09-01
影响因子：
6.6
通讯作者：
Bruijnzeel, LA
中科院分区：
文献类型：
--
作者：
Bruijnzeel, LA
对热带森林砍伐和转换为其他土地用途对水文功能的影响的不同看法，引起了越来越多的，往往是激烈的辩论，在东南亚的公共环境政策的方向。为了使这一争论更加平衡和清晰，本文回顾了关于良好森林覆盖的存在或缺乏对区域气候的影响的广泛的现有科学证据（降雨量）、总水量和季节水量（洪水，低流量），以及在潮湿热带条件下，特别是在东南亚，不同形式的侵蚀和集水区产沙量。得出的结论是，森林干扰和转化对降雨量的影响将小于东南亚完全转化为草原时预测的平均减少8%，因为二次再生的辐射特性很快又与原始森林的辐射特性相似。此外，在普遍的“海洋”气候条件下，陆地覆盖物变化对气候的影响预计不如海面温度变化的影响那么明显。总的年水量被认为是增加的森林生物量的百分比删除，与最大收益的水产量后，全部清除。由于降雨量和地表扰动程度的差异，不同地点和年份的实际数量不同。只要地表扰动仍然有限，每年增加的水量大部分以基流（低流量）的形式出现，但降雨渗入的机会往往减少到雨季地下水储量补充不足的程度，结果旱季流量大幅下降。虽然重新造林和土壤保持措施能够减少与土壤退化有关的高峰流量和暴雨流量的增加，但没有充分记录的案例表明这也造成了低流量的相应增加。在某种程度上，这反映了新种植树木的用水量较高，但不能排除土壤蓄水机会可能由于清理后阶段的土壤侵蚀而下降太多，从而无法产生净积极影响。良好的植被通常能够防止地表侵蚀，如果树木覆盖良好，也能防止浅层滑坡，但更深层（>3米）的滑坡则取决于地质和气候因素。对东南亚60多个流域产沙量研究的调查表明，选择性伐木和农业或种植园清理等常见森林干扰的影响非常可观，最重要的是，城市化，采矿和道路建设。“低流量问题”被确定为一个最重要的“流域”问题，需要进一步的研究，沿着的时间间隔之间的评价高地土壤保持措施和任何由此产生的变化，在越来越大的距离下游产沙量。建议今后在传统的成对集水区方法的范围内开展此类工作，并辅之以基于过程的测量和建模技术。最后，在分析土地利用变化对（低）流量或沉积物产生的影响时，应更多地注意流域水文行为的基本地质控制。(C)2004 Elsevier B.V.保留所有权利。
Differing perceptions of the impacts on hydrological functions of tropical forest clearance and conversion to other land uses have given rise to growing and often heated debate about directions of public environmental policy in southeast Asia. In order to help bring more balance and clarity to such debate, this paper reviews it wide range of available scientific evidence with respect to the influence exerted by the presence or absence of a good forest cover on regional climate (rainfall), total and seasonal water yield (floods, low flows), as well as on different forms of erosion and catchment sediment yield under humid tropical conditions in general and in southeast Asia in particular. It is concluded that effects of forest disturbance and conversion on rainfall will be smaller than the average decrease of 8% predicted for a complete conversion to grassland in southeast Asia because the radiative properties of secondary regrowth quickly resemble those of the original forest again. In addition, under the prevailing 'maritime' climatic conditions, effects of land-cover change on climate can be expected to be less pronounced than those of changes in sea-surface temperatures. Total annual water yield is seen to increase with the percentage of forest biomass removed, with maximum gains in water yield upon total clearing. Actual amounts differ between sites and years due to differences in rainfall and degree of surface disturbance. As long as surface disturbance remains limited, the bulk of the annual increase in water yield occurs as baseflow (low flows), but often rainfall infiltration opportunities are reduced to the extent that groundwater reserves are replenished insufficiently during the rainy season, with strong declines in dry season flows as a result. Although reforestation and soil conservation measures are capable of reducing the enhanced peak flows and stormflows associated with soil degradation, no well-documented case exists where this has also produced a corresponding increase in low flows. To some extent this will reflect the higher water use of the newly planted trees but it cannot be ruled out that soil water storage opportunities may have declined too much as a result of soil erosion during the post-clearing phase for remediation to have a net positive effect. A good plant cover is generally capable of preventing surface erosion and, in the case of a well-developed tree cover, shallow landsliding as well, but more deep-seated (>3 m) slides are determined rather by geological and climatic factors. A survey of over 60 catchment sediment yield studies from southeast Asia & demonstrates the very considerable effects of such common forest disturbances as selective logging and clearing for agriculture or plantations, and, above all, urbanisation, mining and road construction. The 'low flow problem' is identified as the single most important 'watershed' issue requiring further research, along with the evaluation of the time lag between upland soil conservation measures and any resulting changes in sediment yield at increasingly large distances downstream. It is recommended to conduct such future work within the context of the traditional paired catchment approach, complemented with process-based measuring and modelling techniques. Finally, more attention should be paid to the underlying geological controls of catchment hydrological behaviour when analysing the effect of land use change on (low) flows or sediment production. (C) 2004 Elsevier B.V. All rights reserved.