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A novel model to evaluate spatial structure in thinned conifer-broadleaved mixed natural forests

林业研究:英文版 2023年第6期34卷 1881-1898页

作者： Hui Liu Xibin Dong Yuan Meng Tong Gao Liangliang Mao Ran Gao Key Laboratory of Sustainable Forest Management and Environmental Microorganism Engineering of Heilongjiang Province Northeast Forestry UniversityHarbin 150040People’s Republic of China

In order to ensure the effective analysis and reconstruction of forests,it is key to ensure the quantitative description of their spatial *** this paper,a distance model for the optimal stand spatial structure based on weighted voronoi diagrams is *** particular,we provide a novel methodological model for the comprehensive evaluation of the spatial structure of forest stands in natural mixed conifer-broadleaved forests and the formulation of management decision *** applicability of the rank evaluation and the optimal solution distance model are compared and assessed for different standard sample plots of natural mixed conifer-broadleaved *** effect of crown width on the spatial structure unit of the trees is observed to be higher than that of the diameter at breast ***,the influence of crown length is greater than that of tree *** are nine possible spatial structure units determined by the weighted voronoi diagram for the number of neighboring trees in the central tree,with an average intersection of neighboring crowns reaching 80%.The rank rating of natural forest sample plots is correlated with the optimal solution distance model,and their results are generally consistent for natural ***,the rank rating is not able to provide a quantitative *** optimal solution distance model is observed to be more comprehensive than traditional methods for the evaluation of the spatial structure of forest *** can effectively reflect the trends in realistic stand spatial structure factors close to or far from the ideal structure point,and accurately assesses the forest spatial *** proposed optimal solution distance model improves the integrated evaluation of the spatial structure of forest stands and provides solid theoretical and technical support for sustainable forest management.

关键词： weighted voronoi diagram Optimal distance model Spatial structure quantifi cation Thinning intensity Conifer-broadleaved mixed natural forests

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Spheres of Urban Influence and Factors in Beijing-Tianjin-Hebei Metropolitan Region Based on Viewpoint of Administrative Division Adjustment

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Chinese Geographical Science 2017年第5期27卷 709-721页

作者： ZHU Jianhua CHEN Xi CHEN Tian School of Geographic Sciences Northeast Normal UniversityChangchun 130024China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China Northeast Asian Studies College Jilin UniversityChangchun 130012China

The coordinated development of Beijing, Tianjin and Hebei has been elevated as China's important strategy. And, the priority in considering how to bring the maximum effect of their coordinated development into play is to delineate the spheres of urban influence with regard to the cities in the Beijing-Tianjin-Hebei Metropolitan Region. By building an evaluation index system of urban comprehensive strength, this paper applies the principal component analysis method to determine centrality strength of the cities, and the breakpoint theory and weighted voronoi diagram to identify the spheres of urban influence in all central cities of the region. Results show that 13 central cities within the region greatly differ in strength, which can be classified into four tiers and that the spheres of urban influence do not have a high goodness of fit with administrative jurisdiction scope. Cities like Beijing, Tianjin, Shijiazhuang and Handan have larger spheres of urban, spheres of urban influence in Tangshan and Qinhuangdao are basically consistent with their administrative jurisdiction scopes, and seven cities including Langfang and Baoding have smaller spheres of urban influence. So according to these cities' comprehensive strength and spheres of influence, the region can be divided into five plates: Beijing, Tianjin, Shijiazhuang, Tangshan and Handan. The major influence factors for inconsistency between spheres of urban influence and spheres of jurisdiction include difference in urban administrative ranking, small number of central cities with weak strength, discrepancy in the number of counties under jurisdiction, unreasonable spheres of jurisdiction and diversity in topographical conditions. In order to solve the imbalance in the spheres of urban influence and those of jurisdiction and better facilitate the coordinated development of the region, it is advised to adjust administrative areas so as to obtain more optimized urban spatial layout and more reasonable urban scale

关键词： spheres of urban influence urban comprehensive strength adjustment of administrative divisions weighted voronoi diagram Beijing-Tianjin-Hebei Metropolitan Region

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