The influence of vegetation on the microstructure and erosivity of precipitation

Abstract

The process of precipitation interception, in which vegetation retains precipitation, has a major influence on natural processes such as soil erosion. Assessing this influence requires measurements of the microstructure of precipitation using modern instruments that allow measurements of the velocity, size, and number of raindrops. The precipitation microstructure data were obtained using 1-minute measurements from three optical disdrometers placed under the birch canopy, under the black pine canopy and above the canopies. In the period under consideration between 12 July 2022 and 16 February 2023, 48 rainfall events were recorded, for which the duration, the amount of precipitation, the average intensity of precipitation, and the characteristics of the raindrops (size, velocity, and number of drops) were calculated. Additionally, the kinetic energy (KE), the maximum 30-minute intensity (max I30), and the rainfall erosivity factor (R) were calculated. All these variables were calculated for measurements above and below the tree canopies. The results show that the proportion of intercepted precipitation decreases with the duration of the events for both birch and pine. Droplets increased on average during the leafed period, as they passed through the tree canopy, and decreased during the leafless period. During the entire period, the diameter of the droplets increased on average by 46% under birch and by 26% under black pine. The droplet velocity decreased on average by 38% under the pine, while it increased minimally under the birch by 1%, which is the result of an increase in the average velocity under the birch during the leafless period by 7%. The analysis of the results shows that the rainfall interception has a large impact on soil erosion, as, for example, the rainfall erosivity factor (R) under birch decreased by 43% and under pine by 90%.