Trend Analysis of Soil Salinity in Different Land Cover Types Using Landsat Time Series Data (Case Study Bakhtegan Salt Lake)

Abstract

ABSTRACT:Soil salinity is one of the main causes of desertification and land degradation which has negative impacts on soil fertility and crop productivity. Monitoring salt affected areas and assessing land cover changes, which caused by salinization, can be an effective approach to rehabilitate saline soils and prevent further salinization of agricultural fields. Using potential of satellite imagery taken over time along with remote sensing techniques, makes it possible to determine salinity changes at regional scales. This study deals with monitoring salinity changes and trend of the expansion in different land cover types of Bakhtegan Salt Lake district during the last two decades using multi-temporal Landsat images. For this purpose, per-pixel trend analysis of soil salinity during years 2000 to 2016 was performed and slope index maps of the best salinity indicators were generated for each pixel in the scene. The results of this study revealed that vegetation indices (GDVI and EVI) and also salinity indices (SI-1 and SI-3) have great potential to assess soil salinity trends in vegetation and bare soil lands respectively due to more sensitivity to salt features over years of study. In addition, images of May had the best performance to highlight changes in pixels among different months of the year. A comparative analysis of different slope index maps shows that more than 76% of vegetated areas have experienced negative trends during 17 years, of which about 34% are moderately and highly saline. This percent is increased to 92% for bare soil lands and 29% of salt affected soils had severe salinization. It can be concluded that the areas, which are close to the lake, are more affected by salinity and salts from the lake were brought into the soil which will lead to loss of soil productivity ultimately.

Thermography for soil salinity assessment

“…The trend in soil salinity increase over time we showed was in most of the cases in accordance with other studies (Taghadosi and Hasanlou, 2017;Wang et al, 2008).…”

“…The maps have been produced for six time steps: 1986, 2000, 2002, 2005, 2009, 2016. These years have been selected to correspond with other studies describing temporal changes in soil salinity (Fan et al, 2012;Taghadosi and Hasanlou, 2017;Wang et al, 2008).…”

“…According to Taghadosi and Hasanlou (2017) Bakhtegan Salt Lake region in Iran. According to Taghadosi and Hasanlou (2017) soil salinity increased in this area. On contrary to the cases described previously, our map of the Yellow River Delta is not in complete accordance with the reference.…”

Monitoring land use and soil salinity changes in coastal landscape: a case study from Senegal

“…These indices were chosen because they have given better correlation in the analysis of salt-affected areas and constitute good indicators for salinity classification and quantification (Poenaru et al, 2015 ). They were recently used in various regions to predict soil salinity distribution (Zhang et al, 2011 ; Taghadosi & Hasanlou, 2017 ; Yossif, 2017 ; Allbed et al, 2017 ). Elevation and TWI were derived from DEM (i.e., 30 m × 30 m resolution); DEM was obtained from the Directorate of Geographic and Cartographic Services in Senegal.…”

“…Among them are LANDSAT, SPOT, IKONOS, and Terra-ASTER with the resolution ranging from medium to high as well as hyperspectral sensors (Metternicht & Zinck, 2003 ; Azabdaftari & Sunar, 2016 ). In recent years, various salinity and vegetation indices such as normalized difference vegetation index (NDVI), normalized difference salinity index (NDSI), salinity index (SI), and soil-adjusted vegetation index (SAVI) have been used to delineate salt-affected areas (Zhang et al, 2011 ; Taghadosi & Hasanlou, 2017 ; Yossif, 2017 ; Allbed et al, 2017 ). By integrating multi-temporal imagery with biophysical data, these remote-sensing indices and soil properties may provide an accurate estimation of soil salinity changes.…”