Preservation of old‐growth forests: a case study of Big Timber Park,Whistler, BC

This paper explores the concepts of old‐growth forests, preservation and natural disturbance and demonstrates how contemporary biogeographic theory contributes to successful preservation of old‐growth forests. The case study analyzes the composition, structure, age and growth histories of trees in Big Timber Park, Whistler, British Columbia. Composition. The structure of the forest was diverse and tree ages ranged from 122 to 305 years. The densities of large old Douglas‐fir, shade‐tolerant trees and all snags are indicative of old‐growth forests; however, maximum tree diameters and densities of large snags and logs do not meet quantitative criteria for old‐growth forests. The abundance of tree regeneration and understory vegetation are relatively low. We conclude that some aspects of Big Timber Park are transitional between the mature and old‐growth stages of forest development. In the future, fine‐scale canopy gaps caused by tree senescence and interactions among insects, pathogens and wind are expected to dominate stand dynamics. Forest structure will become increasingly complex, exemplifying the dynamic nature of old‐growth forests. To successfully preserve Big Timber Park and La préservation des forêts other old‐growth forests in Canada requires understanding of natural disturbances. Preservation and the criteria and indicators used to measure successful preservation must explicitly include elements of natural change.     

基于理性选择理论的“蚁族”居留意愿研究——来自北京市的实证调查

蚁族是否定居在一线城市是基于自身效用最大化的结果。本文使用课题组2016年12月北京蚁族的调研数据,对京蚁地理空间分布进行分析,在此基础上,参照理性选择理论分类标准,从生存理性、经济理性和社会理性三个维度出发,对影响蚁族居留意愿的因素进行实证考量。研究发现,蚁族是否定居北京主要受性别、教育程度、居住状况、社会保障以及社会交往情况等因素的影响,社会理性相较于经济理性和生存理性对蚁族居留意愿的影响更为显著,并从社会空间理论视角对影响因素的显著性原因进行分析,从而为相关政策制定提供参考。