| The Platycladus orientalis, which was one of the most extensive forest planting inYan’an city and occupies an important place in the suburban forest configuration. This studywas carried out in some sample plots of the outskirts of Yan’an city and the objective was toassess naturalness of Platycladus orientalis in this region. On this basis, through sensitivityanalysis of22indexes which describes the community characteristics,12indexes werefiltered out and used to establish an assessment index system. Integrated indexes wereanalyzed with the analytic hierarchy process (AHP) to build an index system for assessing thenaturalness. Sorting and dividing integrated indexes value of naturalness of differentcommunities. According to the naturalness index of Platycladus orientalis, we also discussthe late reformation and technical measures, which will play its important role as a suburbforest. The results showed that:(1) According to the survey on the12representative standard lots in the suburb of Yan’an, the regeneration of under canopies did not affect. The overall benefit of forest is low, andthe average tree age is29.5, average diameter at breast height is11.6cm, the average treeheight is7.0m, the canopy density is0.63on average, the average seedlings updated is34.3N/hm2.(2) To constructe the index system for assessing the naturalness of Platycladus orientalisin Yan’an suburb through sensitivity analysis, we set up two class indexes: one class indexwas vegetation composition, soil fertility, and succession stage and two class index was theaverage diameter of constructive trees, high classes of constructive trees, the averageseedlings updated, arbor layer species richness, arbor layer Pielou eveness index, shrub layerMargalef index, organic matter content, organic matter, total nitrogen, available phosphorus,available potassium, CI and hemeroby.(3) Sorting and dividing integrated indexes value of naturalness of different communitiesin Yan’an suburb. The integrated indexes of naturalness of Platycladus orientalis and Quercuswutaishannice mixed plantation, Platycladus orientalis and Populus hopeiensis mixedplantation, Platycladus orientalis and Robinia pseudoacacia mixed plantation, Platycladusorientalis plantation were0.78,0.76,0.38,0.19and their naturalness classifications were2,2,4,5respectively. Platycladus orientalis and Quercus wutaishannice mixed plantation, Platycladus orientalis and Populus hopeiensis mixed plantation were were semi-natural forest,Platycladus orientalis and Robinia pseudoacacia mixed plantation was near-plantation andPlatycladus orientalis plantation was plantation, respectively.(4) Discussing the model of different Platycladus orientalis configuration, according toassess naturalness of Platycladus orientalis and analysis of the existing problems of the stand,follow the principles of plant configuration space. Some corresponding measures of urbanforest ecological system building and management were proposed. |
