| In order to study the wind protection effectiveness of shelter forests in the area above Chengde Dam.Selecting the shelter forest of Pinus sylvestris var.in Yudaokou as the research object.Through field investigation and wind tunnel test.Study on the law of wind speed after the protection of different tree heights and different degrees of erosion.Analysis of shelter forest windproof performance;Select the Pinus sylvestris var.Drawing on the traditional forest density control chart drawing method.Develop a density control chart for the wind-proof efficiency of Pinus sylvestris var.Analyze the relationship between stand factors and wind protection performance.The main conclusions are as follows:(1)Through the wind tunnel test combined with the field survey results,the wind-proof efficiency of different trees of Pinus sylvestris var.With the increase of tree height,the wind speed and relative wind speed of the protective forest belt are gradually decreasing.Windproof performance is directly proportional to tree height.6m is 16.19%,10 m is 21.02%,14 m is 25.16%,and 18 m is 31.37%.There were significant differences in wind-proof performance between different tree-sorghum pine forests.The windproof performance of the protective forest after the forest belt decreased with the increase of the horizontal distance.The windproof performance was the highest at 1H and the smallest at 20 H.The windproof performance of the protective forest after the forest belt decreases with the increase of the vertical distance.The windproof performance is the largest at 30 cm and the smallest at 300 cm.(2)Through wind tunnel test,the wind-proof performance of different sag of Pinus sylvestris var.After the forest belt,the wind speed and relative wind speed increase with the increase of horizontal distance and vertical distance.Windproof performance decreases as horizontal and vertical distances increase.The horizontal wind distance is 1H and the vertical distance is 30 cm.The windproof performance of compact,permeable and ventilated shelter forests,there are significant differences between the two.The permeable type(0.5-0.6)protection forest has the highest windproof performance,the worst ventilation type,and the tight windproof performance is between the permeable type and the ventilated type.(3)Use the trunk to analyze the data and combine the second type of survey data.The relationship between the factors and forest stand factors of Pinus sylvestris var.In terms of forest factors,four empirical equations of Logistic,Gompertz,Richards and Korf were used to fit the height and DBH growth of Pinus sylvestris var.and the relationship between height and DBH was studied.The high growth law of Pinus sylvestris var.accords with the Gompertz model,and the height of the tree is positively correlated with the age change,that is,the tree height increases with age;The DBH growth pattern is similar to the tree height,which is consistent with the Gompertz model.The DBH is positively correlated with age change;There is a positive correlation between the DBH and the height of the tree,which is consistent with the trend of the quadratic function.In terms of stand factors,the growth curves of Pinus sylvestris var.forest stands were established by the empirical equations such as tree height line,equal diameter line,maximum density line and natural sparse line.(4)Drawing method based on traditional forest density control chart.Developed a forest density control chart for Pinus sylvestris var.Fitting the model and parameters of the stand volume of Pinus sylvestris var.plantation.Based on the stand density control chart,the model and parameters of the stand volume and wind protection efficiency are fitted.Based on the factors such as the height of the stand,the diameter of the forest,and the density,the density control chart of the wind-proof efficiency of Pinus sylvestris var.And analyze the relationship between the forestry factors,and introduce the application method of windproof density control chart. |
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