2003-2008年甘肃民勤绿洲土地荒漠化动态监测

Monitoring of Dynamic Change of Land Desertification in the Minqin Oasis during the Period of 2003-2008

通过对2003年和2008年2期覆盖民勤的TM影像解译,对民勤绿洲及其外围20 km范围内8 355.20 km2土地进行荒漠化动态监测。结果表明:民勤绿洲土地荒漠化严重,荒漠化土地占到监测区的80%以上。荒漠化类型分为风蚀和盐渍荒漠化2种,呈带状分布在绿洲外围或镶嵌于绿洲内部。2003年监测区内共有荒漠化土地671 333.08 hm2,占监测区总面积的80.35%;2008年监测区内共有荒漠化土地670 396.13 hm2,占监测区总面积的80.24%。5年间荒漠化土地面积减少了936.95 hm2,占监测区总面积的0.11%,其中风蚀荒漠化土地减少了0.49hm2,盐渍荒漠化土地减少了936.45 hm2。从荒漠化程度看,重度荒漠化土地减少了4 347.15 hm2,中度荒漠化土地增加了3 582.21 hm2,轻度荒漠化土地减少了172.00 hm2。减少面积主要分布在绿洲、绿洲外围0～2 km和4～6km范围内,其中绿洲外围0～2 km范围内减少幅度最大,其次是绿洲,绿洲外围4～6 km范围内减幅最小;增加面积主要分布在绿洲外围2～4 km和6～20 km范围内,且增幅较小。2003年和2008年民勤的荒漠化指数分别为2.256 5和2.249 3,荒漠化指数处于中度和重度之间,且偏向中度,荒漠化指数略有下降,整体的荒漠化发展得到了初步遏制。

On the basis of TM image interpretation,this study was to monitor the dynamic change of land desertification with an area of 8 355.20 km2 in Minin Oasis and its peripheral areas during the period from 2003 to 2008.The results show that land desertification was serious and its area accounted for more than 80% of the monitored area.The desertification land in Minqin Oasis was divided into two types,i.e.the wind-eroded desertification and salinized desertification,and it was distributed in the oasis and its peripheral areas in a zonal way.In 2003,the total area of land desertification in the monitoring area was 671 333.08 hm2.and accounted for 80.35% of the total area;in 2008,it was reduced to 670 396.13 hm2.and accounted for 80.24% of the total.During the period from 2003 to 2008,the area of land desertification was reduced by 936.95 hm2.and occupied 0.11% of the total in the monitoring area,in which the areas of wind-eroded desertification land and salinized desertification land were 0.49 hm2.and 936.45 hm2.respectively.Viewing from the desertification degree,the areas of serious desertification land and slight desertification land were reduced by 4 347.15 hm2.and 172.00 hm2.respectively,but the area of moderate desertification land was enlarged by 3 582.21 hm2.The reduced desertification land was mainly distributed in the oasis and its peripheral zonal regions of 0-2 km and 4-6 km in width,in which the area of reduced desertification land was the largest in the peripheral zonal region of 0-2 km,then in the oasis,and it was the smallest in the peripheral zonal region of 4-6 km;the enlarged desertification land was mainly distributed in the peripheral zonal region of 2-4 km and 6-20 km in width,and the enlarged extent was small.The desertification index of the Minqin Oasis was 2.256 5 in 2003 and 2.249 3 in 2008 respectively,it was between the moderate index and the serious one,and it was slightly decreased.Therefore,the development of land desertification was holistically kept within limits.