| The research and practice concerning the restoration of vegetation has been carried out for several years. However, owing to the differences of region, inference types and intensity, the form, reason, degree and responding mechanism of the vegetation degradation also vary from each other. Therefore, the mountain vegetation restorations in different regions have various goals and emphasis, as well as the supporting key technology. It is very strong of Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla in drought-tolerant and barren resistence and the two shrubs are very important in water and soil conservation and vegetation recovery in North hilly and mountainous area. But the attention is insufficient and the research on them is few. This thesis focuses on the two typical shrub Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla in the mountain area of North China, depending on the Thermal Dissipation Probe System and automatic meteorological station, which conduct continuous and simultaneous monitoring of the sap flow and environmental affecting factors of the Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla in Sijia Gou, Gangnan Town, Pingshan County of Hebei Province during2008to2009, and identifies the dominant environmental factors affecting the start and cease of the flow and also its transient changes and the changes of its mean value, finds out the changing process of sap flow under weather and seasonal changes, leading to the establishment of the environmental factors regression model of the flow rate; get the best scaling parameter by the investigation of the sample tree measurement factors, anatomical structure and the biomass; gain the best scaling parameter and the drought resistance and water saving vegetation configuration model at the quadrat level.1.The dominant environmental factors affecting the sap flow:different weather conditions will lead to great differences in the start, increase and decrease or other daily processes; all the environmental factors exert an influence on the trunk flow rate by different degrees, whose weighted average results demonstrated that solar radiation is the main factor affecting the flow rate; the average sap flux value of each day of each month has a direct relationship with the yearly growing regularity of the plants, which manifests as the large water consumption during the period of blooming, fruit setting and fruit enlargement, and small water consumption during other periods; the average cumulative monthly and daily sap flux of Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla exhibits different trends with that of the average value of the environmental factors, but the former shows the same trend with that of the relative humidity, increasing and decreasing with the relative monthly humidity. While it has certain differences with the temperature and precipitation, and has presents complicated variation tendency with the solar radiation.2. The daily and seasonal model of flow rate The model choice under different weather conditions is the MLR (Multiple Linear Regression) Model in the sunny day; the MLR model choice of Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla in different months is the representative model of the whole year. The model of diurnal variations are:Zizyphus jujuba var.:Y=0.65809+0.00282tmp+0.04125vwcc-0.00042hmd+0.00138wng+6.19*10-5smsa-1.65*10-5srdVitex negundo var.Y=0.67552+0.00199tmp+0.04325vwcc+7.16*10-5smsa-0.00061hmd-5.88*10-6srdThe model of seasonal variation are:Zizyphus jujuba var.:Y=0.93073+0.00283tmp+0.00087tmpb+0.00221vwcc-0.00022hmd+0.00134wng+0.01259rnfVitex negundo var.:Y=0.92314+0.00290tmp+0.00225vwcc+0.00838rnf-0.00018hmd+0.00112tmpb+0.00138wng+0.00001srd3. The continuous variation characteristics of flow after rainfalls After the rain, the flow rate and sap flux of Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla increase first and then decrease generally and decrease to the lowest before the rain on29th, July, even with the water consumption of Vitex negundo var. heterophylla larger than that of Zizyphus jujuba var. spinosus Hu; after the rain, with the water content of the soil being high, the plants have enough water for evapotranspiration. As the water content decreases, the water for evapotranspiration also become limited, and then the correlation between the flow rate and the water content of soil strengthens gradually; the correlation between the flow rate and the solar radiation enhances by degrees, and the correlation between the former and the temperature and humidity dwindled gradually; after the rain, the value of the sap flux of Zizyphus jujuba var. spinosus Hu at night shows a increase-decrease-increase movement, while the value of the sap flux of Vitex negundo var. heterophylla at night shows no obvious change, and the two values and the average value of the temperature, humidity and soil water content at night has no distinct movement over time.4. Scaling parameter choice It is seen from the seven parameter simulations, which are the sapwood diameter, tree height, diameter, tree biomass, aboveground biomass, sapwood catheter area, the catheter number per square centimeter, that the parameter simulation differs from different types of trees and the model simulation has large differences. The parameter choices of Zizyphus jujuba var. spinosus Hu are:diameter, tree biomass (intermediate model for the whole plant:biomass and ground diameter), aboveground biomass (intermediate model:aboveground biomass and ground diameter); the choices of Vitex negundo var. heterophylla are:sapwood diameter, diameter, tree biomass (intermediate model:the whole plant biomass and ground diameter), aboveground biomass (intermediate model:aboveground biomass and ground diameter).5. The scaling parameter of stand and the drought resistance and water saving vegetation configuration:After using the sapwood area model with the four parameters of the diameter, tree biomass, aboveground biomass and tree height to calculate the sapwood area of the stand, and using the method of calculating the flow flux to calculate the water consumption of the stand, comparing the results by the Penman’s formula to calculate the same quadrat, the tree biomass is selected as the best stand scaling parameter, the tree biomass and the sapwood area model selected as the best quadrat water consumption calculating model; it is calculated by the fitting models of the age, diameter, height and canopy width to forecast the water consumption and the canopy closure time, by which to determine the planting density and allocation ratio of Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla. The year when the canopy density of Zizyphus jujuba var. spinosus Hu reaches0.8(the canopy area exceeds8000m2) is the7th year, and the average water consumption of the preceding seven years is17921.d-1.hm-2, which is the lowest amount of water consumption among the five densities. Therefore, the planting density of Zizyphus jujuba var. spinosus Hu forest is10000trees/hm2. Seen from the five densities of Vitex negundo var. heterophylla,10000trees/hm2reach closure time at the fourth year with an average water consumption of28171.d-1.hm-2;6667trees/hm2reach closure time at the fifth year with an average water consumption of26831.d-1.hm-2, and the comprehensive choice of the planting density of Vitex negundo var. heterophylla is6667trees/hm2. The mixed forest of Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla reaches the closure time almost at the same time, which is6to8years, but the lowest average water consumption (19291.d-1.hm-2) when reaching the closure time is with a proportion of3Zizyphus jujuba var. spinosus Hu to1Vitex negundo var. heterophylla. Therefore, the best mixed model configuration is3:1for Zizyphus jujuba var. spinosus Hu and Vitex negundo var. heterophylla. The mixing ratio of tree and shrub in drought resistance and water saving vegetation is tree1shrub3, the density of tree is2*2m that is 500in one hm", the densitys of shrub are Zizyphus jujuba var. spinosus Hu3750in one hm2and Vitex negundo var. heterophylla1250in one hm2. |
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