Analysis of Chinese farmland under different altitude based on GIS and RS

While farmland less is recognized as a global farmland resource problem, little is known on a wide scale about the relationships between farmland and altitude. This study analyzes the dynamic distribution of Chinese farmland from mid-1980s to 2000 for different altitudes. Farmland dynamic coverage is obtained by visual interpreting mid-1980s and 2000 TM images under MGE environment and other data. All data are changed into 100m*100m grid format. Then we overlay it with DEM data with scale 1:250000 in ARC/INFO GRID module. During the last 15 years, some people think that farmland in China has been reduced drastically with increasing population pressure and agricultural activities. This paper announces that in some districts the farmland was reduced, yet in some other districts the farmland was enhanced. For paddy field, the area below 100 meters is reduced. From 100 to 200 meters, the area is increased with great speed. From 200 to 500 meters and from 1000 to 1500, the area is becoming bigger although the range is small. From 500 to 1000 meters and above 1500 meters, the area is, almost unchanged. For dry land, the area below 100 meters is reduced no more than the paddy field´s. Above 100 meters, the area is increased. From 200 to 500 meters and from 1500 to 2000 meters, the range of increased area is great. Except that, the change is not obvious.