جستجوی مقالات مرتبط با کلیدواژه « Man-Kendall trend test » در نشریات گروه « آب و خاک »

Aired areas are often affected by rapid soil erosion, land degradation, and desertification. Therefore, continuous monitoring of land cover changes is required. Remote sensing data with spatial and temporal information are suitable for this purpose. In the present study, the time series of TGSI and Albedo remotely sensed indexes were used to monitor desertification in the center of Khuzestan province. After constructing the above-mentioned indexes for the period of 1999-2019 using ETM+ sensor images, the values of 411 randomly selected samples on the images were used to construct the Albedo-TGSI feature space model for each year and the correlation between the variables was calculated 0/48-0/83 in different years. The DDI (Desertification Degree Index) was then obtained based on the slope of the fitted line, and the value of DDI was calculated for each sample in each year. By applying a natural break classification on DDI, different levels of desertification and the break values were obtained and considered as the representative of the class in each year. Therefore, five time series of five desertification degrees were formed. Finally, a Man Kendall trend test was carried out with %95 and %90 confidence levels. The results showed that none of the series, except for the high desertification degree, showed a significant trend at the level of 5%. However, severe and high desertification degrees time series with p-value, 0.090 and 0.050 values showed a significant trend at the level of 10%, respectively. Also, the spatial distribution map of the average changes in the trend of desertification index in different classes, showed that in total, about 81% of the region was in severe and high desertification classes with a significant increasing trend of desertification.The results showed a high desertification degree at %5 significant level, and a sever desertification degree at %10 significant levels, showing increasing desertification trend. Furthermore, the spatial distribution of average DDI index indicated that about %81 of the study area was in severe and high desertification classes with a significant increasing trend.