径流形成机制研究在水文学领域中具有十分重要的意义,且受到越来越广泛的重视。水文环境以及水文通量的空间异质性和时间变化性导致了水文过程的尺度依赖性和非线性特征,没有对水文过程较为清晰的认识,就不能将某一地区某一流域森林植被变化水文生态效应的研究结果简单地外推到其他地区和其他流域。开发基于物理过程分布式参数水文模型可以为认识森林植被变化的生态学后效和客观评价森林植被水文生态效益提供可行的工具。但是要实现这一目标,研究森林植被影响径流形成机制是问题的核心所在。另一方面,认识森林影响径流形成机制有助于研究水文学中的尺度问题。研究森林植被影响径流形成机制的主要方法包括水文测验、同位素示踪和动力水文学计算等,研究的空间尺度则为坡面与流域相接合。从已有的研究成果来看,森林植被影响径流形成机制可以概括为:①森林流域径流形成为变动源区产流机制;②森林流域径流形成主要受饱和地表径流、亚表层径流和地下径流的控制;③森林流域径流形成机制是相互作用和相互转化的;④优先流在森林流域径流形成中起到了至关重要的作用。

Runoff generation mechanism is one of the key research focuses in the hydrological study on which more and more attention is concentrated.The complexity of hydrological processes such as scale dependence and nonlinear behavior resulted from the widespread spatial heterogeneity and temporal variability of hydrological environment and fluxes makes it very difficult,given that without detailed understanding of the physical processes,to extrapolate the information from one area to another or from one scale to another.Current generation of physically based,distributed parameter models could accommodate the assessment of hydrological impacts of forest vegetation changes to certain degree in comparison with traditional approaches.However,the confidence of such models and the scale issues highlights current and future research needs in the forest vegetation influences on the runoff generation and delivery mechanisms.Three major research methods being adopted are hydrometry,tracer/isotope tracing,and dynamic calculation at the spatial scale from hillslopes to watershed.The current understanding of forest vegetation influences on the runoff generation could be summarized as (a)runoff is controlled by variable source area mechanisms for forested watershed,(b)major runoff components for forested watershed are saturated surface runoff,subsurface runoff,and groundwater runoff,(c)co existing and shifting of different runoff generation mechanisms,and (d)preferential flow is a key factor in controlling runoff generation for forested watershed.