荒漠化是中国当前面临的主要生态环境问题之一。本文以长时间序列的遥感数据NDVI为基础，关注其年际动态变化特征，选取植被降水利用率作为评价指标，利用时间序列分析方法和残差法，评价陕甘宁地区1999-2010年的荒漠化发展态势以及人类活动在土地退化中所起的作用，并初步讨论荒漠化逆转问题。结果表明：近12年，陕甘宁地区大部分地区植被功能显著增强，生态环境状况趋于好转，尤其在研究区域的中部以及黄河沿岸生态环境趋于好转较明显，只有极少数地区出现退化现象。陕甘宁地区植被生态功能适宜年降水量在300~500 mm区间，当年降水量大于500 mm时，植被功能恢复能力会出现衰退趋势。在研究区，人类活动主要表现为正作用，只有1.65%表现为负作用较少，且为不显著负作用，分布零散。干旱区、半干旱区荒漠界线不稳定，容易造成荒漠化逆转的假象，误导人们对荒漠化逆转评价。因此，判断荒漠化逆转问题要在特定的时空尺度上，同时要结合当年的气候以及人类活动的因素影响进行分析。
Desertification is one of the main ecological environment problems in current. The paper discussed development situation of desertification in the Shanxi-Gansu-Ningxia Region from 1999 to 2010 and the role of human activities on land degradation, discussed the reverse of desertification problem based on the long time series of NDVI remote sensing data, focused on the characteristics of its annual dynamic change, selected the vegetation precipitation utilization as evaluation index by using time series analysis and residuals method.The results showed that most areas the vegetation function is significantly enhanced, and the ecological environment improved in nearly 12-years, especially in the middle area of Shanxi-Gansu-Ningxia region, only a handful areas appeared degradation phenomenon. The annual precipitation in 300-500 mm is suitable for vegetation ecological function in the most areas of Shanxi-Gansu-Ningxia Region. The main human activities present positive influence, the negative effect is less and account for only 1.65%. It's easy to improperly judge reversion of the desertification because the arid and semi arid desert line is not stable. Therefore, the reversion of the desertification need to be discussed in a specific time and space scales. At the same time, It is necessary to combine the climate and human activity factors.
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