大流通背景下北京外埠蔬菜供应时空格局及效应分析

大流通背景下,随着城市化的推进,城市的食品空间供应格局已发生根本性变化,其中外埠蔬菜的供应不仅成为主力,且直接影响到城市居民的多元化蔬菜消费和生活的保障。以北京为案例,对外埠蔬菜时空格局及其效应进行研究,结果表明：①时间上,外埠蔬菜上市量剧增,其所占市场份额成对数增加;②空间上,外埠蔬菜供应类型具有空间分异,供应地空间格局的圈层结构明显,呈东北—西南走向,且主要供应地随季节发生南北转移。北京外埠蔬菜时空格局所产生的效应是：城市食品保障得到更高程度的保障,但随之而来的是城市食物供应半径越来越大,自给能力下降,同时时空转换过程中的季节性断茬,均为城市的食品保障和安全带来潜在的威胁和风险。

Analysis of Tempo-Spatial Patterns of Beijing External Vegetable Supply and its Effects Under Massive Logistical System

With the development of urbanization and logistic system,food supply pattern has been changed fundamentally in city region,of which external vegetable supply hasnot only become the majorsupplier,but also affected the vegetable diversified consumption and basic livelihood of the residents.This paper,taking Beijing as an example,analyses the tempo-spatial patterns of Beijing external vegetable supply and its effects.Two findings are identified.Firstly the amount of external vegetable supply has increased dramatically since 1990s with its market shareincreasing in a logarithm curve.Secondly the spatial pattern in vegetablespecies,supplying hinterland and seasons are explored,i.e.supplying hinterlandremaining a NW-SE directionwith an obviouscircling structure,and its main supplier varies with the season-from north to south.The effect of this pattern brings a better urban food supply because of the diversified vegetable source,but meanwhile increase the food miles dramatically with high carbon emissions.The long-distance transportation suffersfrom extreme events a lot,while the supply failure during the transition of production bases and seasonal change will also bring potential threat and risk for urban food security.Based on this analysis and conclusions,the paper puts forward some policy-oriented suggestions in the last part.