Roles of Birch Forest Shelter-Belts in Stormwater Runoff Regulation

The effects of across-slope birch forest shelter-belts on the stormwater runoff retention were investigated. The research studies were carried out in Kursk oblast in 2021–2024. The leached black heavy-loamy soils moderately thick on the loess-like loam layer occupied the slopes. The ground investigations were carried out on the hazardous erosion-related arable lands on the slopes of opposite exposures in two catchment areas, where the forest shelter-belts of an airflow canopy design for stormwater runoff regulation were located. The forest shelter-belts were single-species stands represented by the warty birch (Betula pendula) also commonly known as silver or white birch planted out in three and two rows across the southern and northern slopes, respectively. The absorption capacity of soils in the forest shelter-belts and on the adjacent fields was estimated with the method of the overhead sprinkling irrigation of the runoff plots with the use of a mobile laboratory. At simulating the rainfall-runoff processes in the two birch forest shelter-belts for natural water management, the similar equilibrium intensity of water absorption with the error limits in calculations comprising 1.01 ± 0.02 mm/min were revealed. The curves of the soil-absorption intensity in the forest shelter-belts had two-dimensional shapes relative to the rainfall erosivity index, which were different from the curves of absorption intensity on the fields. The forest leaf litter can additionally retain to 371 ± 53% water runoff of its mass, regardless of slope exposure. The values for equilibrium intensity of water absorption by soils in the birch forest shelter-belts across the southern and northern slopes were 3.5 and 3.8 times higher, respectively, than that on the fields. The prediction results indicate that the loss of soils from sites on the northern slope with a two-row forest shelter-belt for stormwater runoff regulation can be below the permissible limit set, comprising 0.8 t/ha in sloping areas down the forest shelter-belt and 1.5 t/ha at the bottom of the slope.