The Scale of Land Conversion and Its Effect on the Grain Production in Loess Plateau Area

The conversion of cultivated land back into forest or pasture is an important campaign to improve the ecosystem and protect the environment in the Loess Plateau,but the key is how to improve grain productivity in the remaining arable land and ensure the grain self-sufficiency in the process of ecosystem construction and water conservation,which concerns the ecological environment recovery and socioeconomic development of the area.Based on land use statistics and on-spot survey data,and using the models of target programming and pressure index,the paper analyzes the possible scale of converting cultivated land back into forest or pasture and its pressure on Loess Plateau,suggesting that when 0.1 hm+2 per capita cultivated land is ensured,the farmland converted on the slopes above 15 degrees will be 236.46×104 hm+2,meaning a little over a fifth of the present area of the arable land,that the corresponding reduction of grain will be 195.26×104 t,accounting for 12.69% of average annual grain production from 1996 to 2000,and that the pressure index based on per capita grain possession will be 0.20 for the whole area,making the Loess Plateau Area in Shanxi,Shaanxi,and Gansu Provinces the most heavily impacted area by the conversion.