Interception of rain and snow by second‐growth ponderosa pine

Abstract

This paper reports the results of a six‐year study to determine interception loss in a fully stocked 65‐ to 75‐year‐old second‐growth ponderosa pine stand situated near Bass Lake, California. Interception loss was computed as the difference between measured precipitation and the sum of measured throughfall and stemflow.The average annual precipitation was 47 inches, of which about 84 pct reached the forest floor as throughfall and four per cent as stemflow. Twelve per cent was interception loss. Throughfall, stemflow, and interception loss were directly related to storm size. Regression graphs and equations based upon this relation are given, which permit estimates of interception loss from storm precipitation. An average of four per cent more precipitation reached the forest floor during snow than during rainstorms. However, estimates of annual interception loss are not appreciably improved by use of separate regressions for snowstorms and rainstorms. The interception process is illustrated by rate graphs showing when and how interception loss occurred during a typical storm. Interception loss consisted principally of the water retained by the vegetation during its initial wetting plus that lost by evaporation from the vegetation during storm intervals without precipitation.