Partitioning of rainfall into throughfall, stemflow and interception: effect of forest type, ground cover and climate

This paper reviews current knowledge of the effect of forest type, ground cover and climate on rainfall partitioning into throughfall, stemflow and interception. It considers the variety and reliability of measurement techniques that have been used and interprets the results of interception studies in relation to methodological, vegetational and climatic factors. The review illustrates that it is difficult to draw general conclusions about interception losses by particular forest types because they almost always depend on the type of rainfall and other meteorological conditions during the study period. Characteristics of a forest that affect interception are not always easy to identify and quantify. Characteristics such as trees/ha, branch angle, the uniformity or lack of uniformity in crown height, the nature and thickness of the bark layer, leaf shape and inclination, and leaf area index will all influence interception. The major difficulty is reliable estimation of throughfall. It is not unusual for measured throughfall to exceed the rainfall value, causing interception to be negative. The difficulty in estimation of throughfall is discussed. while also addressing the need for accurate measurement of rainfall. In forests where stemflow volumes are large enough to significantly influence the interception values, the methodological approach is even more difficult. Measurement of interception on a periodic basis presents fewer problems than estimation on an individual event basis because the variables that affect the values of throughfall and stemflow can change over very short periods, for example the intensity and angle of rainfall, and wind speed and direction. However, carefully conducted event-based studies can quantify the influence of a number of the variables. Copyright (C) 2000 John Wiley & Sons, Ltd.