Reseach On Effects Of Larix Principis-Rupprechtii Mayr. Plantation In Different Thinning Intensity In Guandi Forset Area

North China larch (Larix principis-rupprechtii Mayr.) is the most widespread North China, our main forest ecological species. North China larch plantations to North China water conservation, windbreak and sand-fixation as well as the formation and maintenance of forest ecosystem play a role instead. North China larch plantations sand dust storm not only alleviate the from Inner Mongolia plateau, in Beijing, Shanxi region,make the green barrier of Beijing, Shanxi ecological security. North China larch as the main tree species of Guandi Foresry Bureau business, Loess Plateau region is directly related to the overall quality of ecological environment construction. North China larch as the research object, this paper comprehensively analyses the theory related to forest tree growth under different intensity and the change of the plant diversity and so on, in order to control effect of the cradle, promote scientific and reasonable thinning the region competition in theory as well as related tending measures. Main conclusions are as follows:Under a certain site conditions, different intensity of tending thinning measures to close the emperor mountain forest young north China larch plantations have significantly improve DBH growth, of which strength thinning effect is best, seven years after the cut, the average DBH of trees can be up to 11.18 cm, the average annual growth rate of 4.79%;Thinning measures in the short term could promote the growth of stand to keep wood tree height, but in the long run under different thinning intensity difference influence on the growth of tree height was not significant, thinning seven years later, contrast, weak, moderate, intensity thinning forests under the condition of high order to an average of 11.5 m,11.4 m,11.7 m,11.6 m.Under certain conditions, the thinning method can improve the average annual growth rate of the stand unit area and the average annual growth rate, and to strength the thinning effect is best, after seven years in the thinning and thinning intensity of average annual growth rate and the average annual growth rate reached 6.53 m3/ha,6.89%;And thinning method in the short term will not be able to improve the stand volume per unit area, but in the long run, moderate thinning is able to improve the stand volume per unit area, thinning seven years later, the stand volume per unit area from big to small in turn is 99.32 m3/ha and 99.32 m3/ha, the intensity is 93.49 m3/ha, low degree of 92.28 m3/ha.Under certain conditions, different intensity of thinning density will make the understory shrubs and herbs ascend, species richness, diversity, of which strength thinning effect is best.After seven years in the thinning and thinning intensity increased 17 plant species in the sample area, thinning intensity sample understory shrubs of Simpson, diversity index, Shannon Wiener diversity index, Jsw evenness index, respectively, comparing to increased by 20.65%,20.65%,19.61%;Thinning intensity sample forests of herb Simpson, diversity index, Shannon Wiener diversity index, Jsw evenness index respectively than still increased by 23.39%,23.39% and 23.18%.After seven years in the thinning and thinning intensity within the sample area within the undergrowth biomass than as usual to increase by 19.10%.(1) Under certain conditions, undergrowth thinning measures can improve soil structure, with the increase of thinning intensity, soil moisture content and soil porosity also increase, thinning seven years later, after a severe thinning forests of 0 to 10 cm soil soil moisture content and soil porosity can be 48.44%, 564%, reach the range of light loam, is helpful to keep the growth of the wood.Thinning of undergrowth can also improve the soil nutrient structure, accelerate forests soil nutrient cycling, and the thinning intensity, the greater the effect more apparent,7 years later, in the thinning intensity thinning forests under the condition of soil total nitrogen content, soil organic matter content were increased 104.21%,139%.(2) Soil density of fine root biomass and soil depth correlation relationship, but the size and density of forest land is thinning intensity had no obvious correlation between relations.In the stand density of 3600 plants/hm2, that is, under the condition of moderate thinning, fine root biomass, soil density, the highest can reach 6 x 10-3g/cm3.Undergrowth thinning method significantly reduces the surface layer of soil is longer than the root, and no significant influence on 20-30 cm soil layer. With the increase of soil depth, the influence of stand density contrast root gradually reduced.For the initial density of 5000-5500 plants/hm2 close emperor mountain forest region for 20 years in north China larch plantation, when stand used for timber forest, with moderate thinning measures, which would hold density of 3800-3500 plants/hm2, after seven years in the thinning and can effectively increase the stand volume per unit area; When stand used for ecological cemetery, USES the thinning intensity, which would hold density of 2800-2500 plants/hm2. can effectively improve forest undergrowth biodiversity, soil quality, improve forest ecosystem stability, and maintain the best effect on the improvement of the ecological.