Driving forces of "poplar expansion and cropland shrinkage" in the North China Plain:A case study of Wen'an County,Hebei Province
华北平原“杨上粮下”现象的驱动机制——以河北省文安县为例

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.