华北平原“杨上粮下”现象的驱动机制——以河北省文安县为例

Driving forces of "poplar expansion and cropland shrinkage" in the North China Plain:A case study of Wen'an County,Hebei Province

以Landsat5TM遥感影像、农户调查数据和统计数据为基础数据,运用3S技术提取了案例区河北省文安县1995～2007年土地利用变化信息,分析了杨树扩张的时空格局;并从农户杨树种植决策行为视角,运用数理统计、投入产出法分析了杨树扩张占地的驱动因素。结论如下:(1)杨树林地扩张幅度大、速率快。(2)杨树扩张所用土地92.14%来源于耕地,"杨上粮下"现象突出。(3)杨树扩张速率的空间差异显著。杨树扩张受生产要素、土地产品市场及政策因素的综合驱动,其中劳动力因素和经济因素起主要作用。(4)非农从业人员比率和农民年人均收入越高,杨树扩张速度越快。在劳动力由富余转为相对稀缺的情况下,农户为提高经济收益,倾向选择耗工少,劳动生产率较大的杨树,是杨树扩张占地的根本原因。

This paper extracts information of land use change in the study area of Wen＇an County,Hebei Province in the period of 1995～2007,and analyzes the spatial-temporal pattern of poplar woodland expansion by using TM images of Landsat5.In the view of farm household tree-planting decision-making,it examines driving forces of conversion of arable land to woodland by using mathematical statistics and input-output approach.The results are shown as follows.（1） Woodland of poplar expands substantially and fleetly.（2） Some 92.14% of poplar woodland is originally arable land.Such a conversion is one of the major land use changes in the area.（3） There is a significant spatial difference of expansion speed of poplar woodland.The expansion of poplar is driven by market signals and government policies as well.Change of the labor force resources of farm household plays a leading role in the expansion of poplar.（4） The higher the percentage of non-agricultural employment and per capita annual income of farmers in rural areas,the higher the expansion speed of poplar.Today there is a decreasing trend of labor force in agriculture.In these circumstances,farm households tend to choose land use types with higher labor productivity.Labor productivity of poplar planting is higher than that of field crops,such as wheat and corn,because there is less labor input of poplar planting than that of field crops,which is the main reason for the conversion from arable land to forest land.