Water conservation capacity of forest ecosystems in Taihang Mountain

Water conservation is a comprehensive water resources regulatory function of forest ecosystems through various hydrological processes, including canopy interception, litter containment and soil retention. As a typical northern rocky mountain area, Taihang Mountain is characterized by low rainfall with uneven seasonal distribution, shallow soil, low soil water-holding capacity and fragile environment. In spite of this, Taihang Mountain is an important ecological security shelter for the water sources belt in the North China Plain. Water has become one of the key limiting factors for the protection and restoration of vegetation in the region. Therefore, comparative analysis of water conservation capacities of main forest vegetation types is needed for development of feasible measures for water conservation and sustainable water security in the region. In this paper, we selected 196 records of canopy interception, litter and soil water carrying capacity in the natural deciduous broad-leaved forest, artificial deciduous broad-leaved forest, mixed forest, natural coniferous forest, coniferous forest and shrubs in the mountain region. We integrated water storage capacity with canopy rainfall interception, litter and soil water-holding capacity and then analyze water carrying capacities of main forest vegetation types in the area. Forest integrated water conservation capacity was calculated using a water conservation function for forest ecosystems. The results showed that:1) soil non-capillary porosity had positive correlation with integrated water holding capacity of the ecosystem and the maximum soil water-holding capacity accounted for over 90% of the total water capacity of forest ecosystems in the region. It was revealed that soil layer, as the main water reservoir, was the most important layer for hydrological processes in the forests. 2) Coniferous forests such as Pinus tabuliformis and Platycladus orientalis were more suitable for regional meteorological conditions. Redistribution capacity of precipitation by coniferous forest is significantly higher than that of other forest types. 3) Low canopy density of mixed forest was beneficial to shrub growth and its litter holding was also higher than that of pure forest. 4) Although comprehensive water storage capacity of natural forest was higher than that of plantation forest, water storage capacity of P. orientalis plantation and P. tabuliformis plantation ranked inferior to that of natural forests of Robinia psendoacacia, P. orientalis and P. tabuliformis. In summary, it was important to take afforestation measures for soil erosion, long-term forest enclosure and appropriate stand density in order to fulfill the goals of ecosystem restoration and ecological reconstruction. In order to increase water conservation capacity, plantation forest with tree species such as P. tabuliformis and P. orientalis was recommended in afforestation. This study provided the basis for the evaluation of water conservation capacity of vegetation along with rational management of forest and water resources. It laid the foundation for environmental protection and disaster prevention and mitigation in Taihang Mountain.