Quality Assessing And Key Adjusting Technologies For Scenic-recreational Forests In The Lower Mountains Of Suburbans In Beijing

As toruism and travel aroud the city become more and more popular and the infrastructure has being improved, the forests in suburbans of Beijing have become a more important space for the residents to refresh and exercise. However, the poor quality of forest landscape and the shortage of recreational facilities can rarely meet the recreational needs. So, how to restore and improve the forest landscape becomes the key problem of the forest management in suburbans of Beijing. In this paper, firstly, the resource of scenic-recreational forest in suburbans of Beijing was systematically investigated from four landscape scales, including single trees landscape, in-forest landscape, foreground landscape and prospect landscape. Secondly, single tree quality and growth dynamics, stand quality and growth dynamics, and the arrangement of landscape patches were also studied. Thirdly, a comprehensive evaluation system of landscape elements was constructed on the four scales mentioned above. And the comprehensive quality of forest landscape in suburbans of Beijing was assessed. Lastly, some adjusting technics for improving the quality of scenic-recreational forests of diverse scales was put forward respectively.The main conclusions are as follows:(1) The crown characters of Pinus tabulaeformis and Prunus davidiana were studied. The results show that the elongation growth of branches of both average trees and dominant trees in different stock densities of Pinus tabulaeformis stands were following the curve as S. But the amount and interannual change of elongation growth of dominant trees were significantly higher than the average trees. And the crown structure character and flowers of Prunus davidiana were affected by stand density. Crown development was restrained in high density stand, so the height of the first live branch increases and caused the crown ratio to decrease, however, because of the competition between different individual trees, the crown width decreases as a result of the increase of stock density. Even though the differences of 1st branch with various stock density were not significant, the branch length, branch angle, basal diameter of branch and lateral branch density of other order branches were evidently influenced by stock density. And basal diameter increases with the increasing stock density. Length of branch significantly increased with its basal diameter but decreases with branch angle. Low stock density has a relatively reasonable proportion of branches and spurs. And the branch structure had more advantages for the photosynthesis of leaves in different crown depth and had a large quantity of flowers. Accordingly, the stock density of scenic forest of Prunus davidiana should be less than 2500 trees/hm2.(2) The reasonable competition indices of Pinus tabulaeformis plantation, Platycladus orientalis plantation and Prunus davidiana plantation were stuied. The result shows that the competition index of RCS was proper to construct the crown growth models of Pinus tabulaeformis plantation and Platycladus orientalis plantation, while the competition index of CI_CV is proper to construct the crown growth models of Prunus davidiana plantation.(3) Based on the analysis of the diameter and height growth of Pinus tabulaeformis plantation and Platycladus orientalis plantation, the crown diameter growth of the two type of forest was developed. And the stand density table for different cite indices in different competition indices was constructed respectively. Taking Pinus tabulaeformis plantation for example, the start time for tinning, the tinning intensity and the tinning plastochrone were proposed.(4) The main landscape elements of Pinus tabulaeformis and Platycladus orientalis on the three scales of single tree, in-forest landscape and foreground landscape were studied by principal component analysis. Using principal component score of each research object as the new classification indices, the qualities of Pinus tabulaeformis and Platycladus orientalis single trees were divided into 4 types, the in-forest of higher scenic beauty were divided into 5 types, and spring scenic forest and autumn scenic forest are divided into 4 types and 6 types respectively by cluster analysis. And 5 types of in-forest landscape construction models,4 types of spring scenic forest construction models and 6 types of autumn scenic forest construction models were also proposed.(5) By taking analytic hierarchy process on single trees landscape, in-forest landscape, foreground landscape and prospect landscape, a comprehensive evaluation system was constructed. By using the system, the quality of the forest landscape in Changhua was assessed. The result shows that the quality of forest landscape was little less than fair average quality and the overall value is 32.33 points, so the forest in the zone should be modulated.(6) The techniques for adjusting single tree quality, stand quality and landscape patches arrangement were proposed.The results not only provide the theoretical and technical support for assessing and modulating the quality of scenic-recreational forest in the Suburban Mountains in Beijing, but also help to improve and assess the scenic beauty of forest landscape in other regions.