| Pinus tabulaeformis is the important afforesting tree species,and it is wildly distributed in Beijing,especially in mountain areas.Most Pinus tabulaeformis is located at the altitude between 200 and 1500metres,and most of them are Pinus tabulaeformis plantation.Since 1960s,the growths of Pinus tabulaeformis generally had been weak caused by high initial planting density,poor site conditions and human disturbance.This study used the data of Beijing Forest Resources Inventory combined with various literatures in the past years and utilized principal component analysis and Pearson correlation analysis methods to analyze the impact of site factors and density on forest growth in Beijing mountainous area.This study analyzed the problems of Pinus tabulaeformis plantation resources and discussed the solution of the problems.The study is also helpful to fully understand the current status of Pinus tabulaeformis plantation resources in mountainous area of Beijing,guide the practice of forest management and further improve the stand quality,ecological and landscape benefits.The following main conclusions were drawn:(1)The distribution area of Pinus tabulaeformis plantation forest resources in the mountainous area are different.Basing on the size of areas,the order is Age IV,Age III,Age I and Age II.The distribution area of shady aspect is obviously higher than the sunny aspects.The Pinus tabulaeformis plantation is mainly distributed in slope?35°and the area distribution of slope>35°is very small.The quality of Pinus tabulaeformis plantation forest is not high,and the tree structure is single.Majority are pure forest and relatively pure forest.(2)The dominant site factors affecting the growth of Pinus tabulaeformis plantation in mountain areas of Beijing mainly include altitude,slope,aspect,soil type,soil thickness,and soil texture.Different site factors have different effects on the growth of Pinus tabulaeformis plantations with different ages.The growth range of the Age?&Age?is affected by site factors to the greatest extent.(3)Based on the average stand volume of Pinus tabulaeformis plantations of various ages,the most suitable site factors are shady aspects,flat slopes,mountain brown soil,loam and thick soil layers.The Pinus tabulaeformis plantations of Age?and Age?are more suitable for growth in the low mountain area,and their suitable altitudes are 200?400m and 400?600m,respectively.The Age?&Age?are more suitable above 800m,and the best is around 1000m.(4)Most of the Pinus tabulaeformis plantations in Beijing mountainous areas are below 2000plants/hm~2,and more than 90%of the small classes are between 300plants/hm~2?1500plants/hm~2.The effect of the stand density on the average tree height of Pinus tabulaeformis plantations with different ages is in the order of:Age?>Age?>Age?>Age?;the effect on the mean DBH is:Age?>Age?>Age?>Age?;the effect on the average stand volume is:Age?>Age?>Age?>Age?.(5)The effect of stand density on the average tree height and average DBH on shady slopes was significantly higher than that on sunny slopes.The impact on the average stand volume is lower on shady slopes than that on sunny slopes.The effect on average height,mean DBH and average stand volume in the low mountain area is higher than that in the middle medium area. |
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