Rainfall redistribution of different vegetations in Taihang Mountain, China

With the implementation of ecological restoration projects, vegetation cover in the Taihang Mountains has increased, but the current situation of water shortages has still not been effectively improved. The impact of increased vegetation on hydrological processes is unknown. As the first action layer of rainfall reaches the terrestrial ecosystem, the vegetation canopy divides rainfall into throughfall, stemflow, and canopy interception. This changes the spatial distribution of the rainfall. Therefore, studying rainfall redistribution processes is important for exploring the relationship between vegetation and water. This study selected eight typical forests, natural Vitex negundo, and artificial froests of Robinia pseudoacacia, Pinus bungeana, Pistacia chinensis, Eucommia ulmoides, Cerasus pseudocerasus, Fraxinus chinensis, and Garcinia multiflora. Field monitoring and indoor experiments were conducted to explore the rainfall redistribution characteristics of different forest stands of the Taihang Mountains. The results of the study were as follows: 1) During the study year (2022), the rainfall amount was 480.0 mm, rainfall in the rainy season was 283.25 mm, the number of rainfall events in the rainy season was 20, the average amount per rainfall was 14.16 mm, and the variation range of rainfall intensity was 0.05−0.72 mm∙h⁻¹, mainly consisting of rainfall events less than 5 mm∙h⁻¹. The hypo-rainfall in the rainy season of 2022 fluctuated greatly, and the uneven distribution of rainfall time was mainly concentrated in July and August. 2) The proportion of total throughfall to total rainfall was greater than 60%. The lowest threshold of rainfall amount among eight vegetations for producing throughfall was 0.77 mm; E. ulmoides forest has the largest proportion of total stemflow in total rainfall, with a value of 13.94%, followed by G. multiflora forest (6.78%), and the proportion of total stemflow in the remaining species was less than 5%. The lowest threshold of rainfall amount for eight vegetations for producing stemflow was 3.35 mm; the proportion of total canopy interception of total rainfall was the largest in F. chinensis forest, accounting for 32.97%, and the smallest in P. bungeana forest, accounting for 7.53%. The overall performance was as follows: throughfall>canopy interception>stem flow. 3) Throughfall, stemflow, and canopy interception increased significantly with rainfall. Throughfall rate, stemflow rate, and funneling ratio increased rapidly and then leveled off with increasing rainfall amount. The canopy interception rate decreased rapidly and then leveled off with increasing rainfall. Rainfall redistribution characteristics were greatly affected by rainfall amount and leaf water absorption capacity. It was found that the canopy interception rate of P. bungeana, R. pseudoacacia, E. ulmoides, and G. multiflora forests was significantly smaller than that of natural V. negundo, which was important for reducing rainfall canopy interception evaporation and increasing effective rainfall. These four forests could therefore be considered for planting in water-shortage areas. Thus, reasonable selection of stand type and adjustment of stand proportions can reduce canopy interception and improve the efficiency of precipitation utilization. The results of this study provide a theoretical basis and data support for the selection of tree species in reforestation projects in the Taihang Mountains.