| Using an artificial rainfall simulator to conduct field experiments, effect of forest tree on canopy interception was analyzed, as well as effect on runoff and sediment yield on the ground surface on the slope scale. Effect of canopy’s structure on interception by individual small trees was also analyzed. The researched tree species included Platycladus orientalis, Pinus tabuliformis, Acer elegantulum, and Quercus variabilis, which are the main tree species in the local in earthy and rocky mountainous area in North China. All these were done to find out forest vegetation types or species and the corresponding structure configuration with the most protective benefits for resources such as water and soil, to investigate quantitative relations between some kind of forest stand structure and the spatial distribution of water resource, to explore the optimal crown type for interception of precipitation. Thus, some theoretical basis for the construction and management of protection forest for the research area could be supplied. Main research conclusions are as follows:(1) Rainfall conditions, vegetation and structure configuration of the vegetation all influence runoff characteristics on the slope surface, such as runoff depth in unit time, the duration of the whole process of runoff yield, the gross runoff volume and the runoff coefficient.(2) With increase of the rainfall intensity, gross sediment yield increased significantly, and rangeability of the gross sediinent yield for bare plot was greater than that for other plots with vegetation; Generally, the smaller plant spacing and rainfall intensity, the better effectiveness of reducing sediment yield, and sequence of plots for that effectiveness in the same rain condition was Im×1m P. tabulaeformis> lmxlm P. orientalis>1.5m×1.5m P. orientalis>1.5m x1.5m P. tabulaeformis; When rainfall intensity was greater, the impact on the soil aggregate bodies was more powerful, which could lead to more sediment yield in per unit time and greater rangeability, yet less duration required to reach a stable state; Within60minutes of rainfall duration, relationship between accumulative sediment yield and duration with runoff could be described by an increasing quadratic polynomial; The order related to content of sediment in runoff under three levels rainfall intensity was 48.40mm/h>78.48mm/h>25.92mm/h.(3) With development of rainfall duration, accumulative canopy interception of forest stand increased linearly with corresponding precipitation, obviously; Changing trend of canopy interception rate for different forest stands with increase of the rainfall duration accorded with power function curve; In a general way, interception percentage decreased with increase of rainfall intensity and relationship between the amount of forest canopy interception and the leaf area index or the coverage of the forest stand was not closely related or obvious.(4) Canopy interception rate of an individual tree declined with the increase of the rainfall intensity drops. Variations in the process of canopy interception for individual trees could be divided into periods of increasing which shortened as rainfall intensity increased, slightly decreasing in some species, and stable levels of interception when the rainfall intensity kept the same but precipitation increased; Interception rate of the coniferous was significantly greater than rate of the deciduous, and rate of the coniferous changed more obviously when the rainfall intensity changed; For the whole canopy of a tree, the superstructure was more important than the substructure regarding the ability of the canopy to intercept precipitation and thus prevent sediment yield; Furthermore, exponential and logarithmic functions could be used to describe the relationships between interception of coniferous, deciduous species, and their own canopy area in per unit canopy depth, respectively; Besides, canopy interception of individual trees and their leaf area index were closely related. |
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