| This dissertation takes typical forest vegetation in rocky mountain area of north china as the research object relying on forest ecosystem positioning observation station in the capital region. According to the principle of water balance, positioning observations of canopy interception, evapotranspiration, surface runoff, soil moisture content, soil flow at each level were conducted on slope scale. The research combined with synchronous observations of the forest vegetation structure indexes, and simulated the hydrologic process on slope scale based on eco hydrological models. It has revealed the influence mechanism of forest vegetation to the water formation, and has evaluated influences of forest vegetation to the runoff forming process and its components quantitatively. According to the influence mechanism of different slope vegetation to the eco hydrological processes, the study screened optimal vegetation type which has best features on regulating volume and water quality purification, it also puts forward to the suitable vegetation types and the reasonable configuration mode to control effective water yield relying on the principle of soil vegetation bearing capacity.The main results were as follows:(1) Study on the characteristics of different forest leaf area index shows that, leaf area index of four stands act out a consistent trend throughout the growing season, as the trend of "increase-smooth-reduce". The increasing time of shrub forest leaf area index is shorter compared to the three arbor stand, and the variation coefficient of shrub forest leaf area index is higher than others in each month and the entire growing season. The coefficient variation of leaf area index in June is significantly higher than the other three months in terms of the three arbor forest. The leaf area index coefficient variation of three stand in June were different obviously. The regression equation was established according to the relationship between leaf area index, crown density, biomass and forest density in different forest stand and structure.(2) The precipitation in forest and out of forest had a great linear positive correlation. Canopy interception correlated a positively relationship with rainfall amount and it tend to be saturated with the increasing of precipitation. Changes of litter water absorbing capacity slowde down at around4h. Litter absorption capacity had experienced a rapid growth to a slow growth and end at a stabilization process. Forest soil infiltration law of different tree species have certain differences. Overall, soil infiltration ability of mixed broadleaf-conifer forest was higher than other forest stand. Soil moisture subsided of5catchment areas reflects the characteristics of evapotranspiration after the massive rainfall. Transpiration of different stand on growing season is diversity. Litter evaporation of each tree species’changing process is roughly same, it can be divided into three stages, the first phase is rapid evaporation, the second is the slow decline stage, and the third is the stable stage. Average soil daily evaporation under the condition changes between0.58mm and1.84mm. Soil evaporation is higher than litter evaporation, and below than the plant transpiration.(3) The runoff volume in shrub runoff plot was the largest in5runoff plots at the two growing season in2011and2012, followed by the mixed pine and oak runoff plot, and then the platycladus orientalis runoff plot, while the runoff volume in pinus tabulaeformis runoff plot is minimal. The main forms of runoff in platycladus orientalis and shrub catchment area were surface runoff, they accounted for95.61%and95.61%of the total runoff respectively. The main form in mixed pine and oak runoff plots was interflow, accounting for90.86%of the total runoff.Slope runoff components in Chinese pine plot was well-proportioned, the volume of surface runoff and interflow accounted for61.99%and38.01%respectively. At the7.21extraordinary rainstorm in Beijing, in terms of total flow in four vegetation types of slope runoff plots, shrub runoff plot outputted the maximum flow, followed by platycladus orientalis and mixed pine and oak runoff plots, and pinus tabulaeformis runoff plot has the minimum total flow. The runoff producing time and lag time in each runoff plot were obviously diverse. The research established two regression equations based on the observed data from2011to2012in Beijing mountain area. One of the equation based on the structure index of different vegetation and surface runoff, and the other based on interflow and soil moisture before rain.(4) The simulation of the slope hydrological processes was using the Brook90model, and its parameter estimation had achieved a good level. With increasing of LAI and canopy density, the soil infiltration and runoff decreased. For all parts of the rainfall distribution, soil infiltration was the main part, followed by the forest interception, and the surface flows were the smallest. In all stand, the total evapotranspiration increased with the increasing of LAI and canopy density. When the canopy density was depressed, the total evapotranspiration (TE) was less than rainfall. With canopy density increasing, the TE increased below, and the increment is much more than rainfall. That means the supply of natural water had been unable to meet the growth potential of plants. And the plant began to suffer a certain degree of water stress for growth. The simulation of different forest structures showes that, the marginal canopy density of platycladus to meet ecological water demand is0.72, the shrubbery is0.74, pinus tabulaeformis is0.71, and the mixed pine and oak is0.7. When the canopy density changed between0and0.7, the runoff decreased with the increasing of canopy density,while the density reached0.8, the effects of forest decreasing runoff was much weaker. When the density was much higher, a large number of precipitation was consumed by forest in various forms, and only small slope runoff could emerge.(5)The soil water storage accounted for the largest proportion through the analysis of the water balance, followed by transpiration. Based on the water balance, we got the formula of vegetation carrying capacity (LAI) calculated relying on the growing season rainfall. The average rainfall of the growing season in2011and2012was448.23mm. The LAI carried by Platycladus is2.99was calculated, the shrubbery is2.55, the Pinus tabulaeformis is3.91, and the mixed pine and oak is4.08. In order to complete slope vegetation configuration, the first step was dividing the site factors, and then choosing the species of low water consumption. At last, the suited vegetation density and canopy density calculated to finalize the configuration. |
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