近年来的黄土高原耕地时空变化与口粮安全耕地数量分析

基于遥感调查数据集定量分析了1990—2015年中国黄土高原地区耕地的时空变化特征和口粮绝对安全最小耕地保障面积的数量变化。结果表明:黄土高原耕地面积从1990年的192 529.65 km²至2015年的182 688.50 km²,净减少了9 841.14 km²,幅度达5.11%,其中2000—2010年的减幅最大,净减少8 483.00 km²;较大的耕地动态变化图斑主要分布于中部和西部区域,细碎的变化图斑广泛分布;耕地地类转出面积(31 875.82 km²)大于转入面积(21 815.25 km²),耕地面积的增加主要由草地和林地转化而来,主要分布在灌溉农业区和东南部平原区,减少的耕地主要转化为草地和林地,主要分布在中部沟壑区的雨养农业区。此外,该时期耕地转化为建筑用地和交通用地等人工表面的面积逐渐增加,主要分布在东南部低海拔平原地区;黄土高原口粮绝对安全所需最小耕地保障面积呈明显减少特征(从1990年的70 913.37 km²

Spatial and temporal changes of cultivated land and quantitative analysis of ration safe cultivated land on the Loess Plateau in recent years

Based on land cover mapsand the survey data, this paperquantitatively analyzed the spatial and temporal characteristics of cultivatedland on the Loess Plateau, northwest China from1990 to 2015,and evaluated the changes in the minimum cultivated land area forgrain safety. The results showedthat the area of cultivated land decreased from 192 529.65 km² in1990 to 182 688.50 km² in 2015 (decreased by 5.11%),of which theperiod 2000—2010 witnessed thelargest change rate, with a net decreaseof 8 483.00 km².The largest decrease in cultivated land was mainlydistributed in central and western area of the Loess Plateau, and the finely-changed pixels were widely scattered. The areas converted from croplands (31 875.82 km²)was larger than that converted to cultivated lands (21 815.25 km²)in the period 1990—2015.The increasedcultivated lands were mainly converted from grasslands and woodlands, which primarily occurred in the irrigated agriculturalareas and southeastern plains of the Loess Plateau; while the decreased cultivated lands were mostlyconverted to grasslands and woodlands, and it was concentrated on the middle rain-fed farm areas of the Loess Plateau. In addition, the area of cultivated land converted to build landgradually increased during this period, and mainly distributed in the low-altitude plains in the southeast of the Loess Plateau. The minimum cultivated land area for grain safetydecreased from 70 913.37 km² in 1990 to 33 981.64 km² in2015, and the corresponding percentage (accounted for totalcultivated land) decreased from 36.83% to 18.60%.However, the decrease of cultivated land has negligible impacton grain safety on the Loess Plateau.