Trunk drain
In hydrology, trunk runoff is the term used to describe the proportion of precipitation that is diverted from the treetops to the trunk. The water flows down along the trunk. By concentrating at one point, considerable amounts of water can infiltrate into a small area (funnel effect). With regard to the soil hydrology, this heterogeneity is an essential difference to evenly distributed precipitation: For example, many studies suggest that the stem runoff increases the formation of new groundwater . The change in the chemistry of the water draining off the trunk is another important influence of trunk runoff on their environment. In many trees, chemical substances are released into the water running along the trunk through the bark and bark, through epiphytes and through the deposition of dust.
Together with the crown passage , the so-called Through case , the precipitate obtained under a forest stand, also stand precipitation called. The stand precipitation is usually less than the field precipitation above the stand, as it is reduced by interception . Notable exceptions are cloud forests , in which positive interceptions are possible due to the formation of dew. Trunk runoff can even become the dominant transport route here.
Trunk runoff is very variable and depends on the properties of the precipitation (e.g. wind speed, size of the raindrops, length and intensity of the rain) and the vegetation (e.g. bark structure, tree species, age of the tree population, angle of the branches). In a 2015 review article, Levia and Germer presented the parameters that were considered important and significant.
In Central European forests, when looking at trunk runoff, the tree species is the decisive factor: in the case of smooth-barked trees, they are large, e.g. B. beech and hornbeam, but very low in rough bark, z. B. with pine and English oak, with some conifers (spruce, larch) they are even completely negligible. In tropical regions, the trunk runoff tends to be higher, which is particularly due to the precipitation properties: Rain events in the tropics are often stronger and shorter, so that the flow paths necessary for trunk runoff can be formed and evaporation from interception is low.
In contrast to the crown passage, the flow of the trunk is relatively difficult to measure. Typically, collecting collars are placed around the tree, which forward the trunk runoff to collecting bins or tipping bins.
Individual evidence
- ↑ Navar, J. (2011). Stemflow variation in Mexico's northeastern forest communities: Its contribution to soil moisture content and aquifer recharge. Journal of Hydrology 408, pp. 35-42.
- ↑ Tanigushi, M., Tsujumura, M., & Tanaka, T. (1996). Significance of stemflow in groundwater recharge, I: Evaluation of the stemflow contribution to recharge using a mass balance approach. Hydrological Processes 10, pp. 71-80.
- ↑ D. Levia, S. Germer: A review of stemflow generation dynamics and stemflow-environment interactions in forests and shrublands. In: Reviews of Geophysics . 53, 2015, pp. 673-714. doi : 10.1002 / 2015RG000479 (free full text).