The spatial distribution of plant populations is an important feature of population structure and it de- termines the population＇s ecological preferences, biological characteristics and relationships with environment...The spatial distribution of plant populations is an important feature of population structure and it de- termines the population＇s ecological preferences, biological characteristics and relationships with environmental factors. The point pattern analysis method was adopted to study the distribution pattern of Picea schrenkiana indi- viduals of different size classes and the correlations between two size classes as well as the impact of topog- raphical attributes on the population distribution. With increasing diameter at breast height, the plant density of the P. schrenkiana population showed a declining trend. Old trees showed a random distribution at a small spatial scale （0-12 m）, whereas saplings, small trees and big trees all had an aggregated distribution at all scales. With the increase of tree age, the scales at which maximal aggregation occurred gradually increased and the aggregation strength decreased. At a small scale （0-16 m）, all size classes showed a negative correlation and the larger the difference between tree size, the more significant the negative correlation. The number of medium, big and old trees had a significantly positive correlation with elevations, whereas the number of saplings and small trees was not significantly correlated with elevations. The numbers of saplings, small and medium trees showed a significant positive correlation with slope gradient, whereas the number of big trees was not significantly correlated, and the number of old trees was negatively correlated with gradient. With the exception of old trees, saplings, small, me- dium and big trees showed negative correlations with convexity index. The study provides a theoretical basis for the conservation, rehabilitation and sustainable management of forest ecosystems in the Tianshan Mountains.展开更多
物流服务供应链(Logistics Service Supply Chain,简称LSSC)以"物流服务分包商→物流服务集成商→物流服务需求方"为基本结构,其中物流服务集成商是整个供应链的主导,从物流服务分包商处订购物流能力并满足最终物流需求客户...物流服务供应链(Logistics Service Supply Chain,简称LSSC)以"物流服务分包商→物流服务集成商→物流服务需求方"为基本结构,其中物流服务集成商是整个供应链的主导,从物流服务分包商处订购物流能力并满足最终物流需求客户的要求。关于LSSC的研究近些年才引起学者重视。本文从一个新的视角研究LSSC,即基于社会网络分析方法从网络结构和关系两种属性角度,剖析物流服务供应链的网络属性,给出了物流服务供应链网络模型,并提出从网络属性角度研究LSSC的新思维,及LSSC网络属性对各成员企业成长作用机理,扩展了物流服务供应链的研究范围。展开更多
基金funded by the 12th Five-year Science and Technology Support Program(2011BAD38B0505)the Forestry Industry Research Special Funds for Public Welfare Projects (200804022C)the CFERN & GENE Award Funds on Ecological Papers
文摘The spatial distribution of plant populations is an important feature of population structure and it de- termines the population＇s ecological preferences, biological characteristics and relationships with environmental factors. The point pattern analysis method was adopted to study the distribution pattern of Picea schrenkiana indi- viduals of different size classes and the correlations between two size classes as well as the impact of topog- raphical attributes on the population distribution. With increasing diameter at breast height, the plant density of the P. schrenkiana population showed a declining trend. Old trees showed a random distribution at a small spatial scale （0-12 m）, whereas saplings, small trees and big trees all had an aggregated distribution at all scales. With the increase of tree age, the scales at which maximal aggregation occurred gradually increased and the aggregation strength decreased. At a small scale （0-16 m）, all size classes showed a negative correlation and the larger the difference between tree size, the more significant the negative correlation. The number of medium, big and old trees had a significantly positive correlation with elevations, whereas the number of saplings and small trees was not significantly correlated with elevations. The numbers of saplings, small and medium trees showed a significant positive correlation with slope gradient, whereas the number of big trees was not significantly correlated, and the number of old trees was negatively correlated with gradient. With the exception of old trees, saplings, small, me- dium and big trees showed negative correlations with convexity index. The study provides a theoretical basis for the conservation, rehabilitation and sustainable management of forest ecosystems in the Tianshan Mountains.
文摘物流服务供应链(Logistics Service Supply Chain,简称LSSC)以"物流服务分包商→物流服务集成商→物流服务需求方"为基本结构,其中物流服务集成商是整个供应链的主导,从物流服务分包商处订购物流能力并满足最终物流需求客户的要求。关于LSSC的研究近些年才引起学者重视。本文从一个新的视角研究LSSC,即基于社会网络分析方法从网络结构和关系两种属性角度,剖析物流服务供应链的网络属性,给出了物流服务供应链网络模型,并提出从网络属性角度研究LSSC的新思维,及LSSC网络属性对各成员企业成长作用机理,扩展了物流服务供应链的研究范围。
