GIS and Remote Sensing Data-Based Methods for Monitoring Water and Soil Objects in the Steppe Biome of Western Siberia

Abstract

This article considers the original techniques based on GIS and remote sensing data (RSD) that permit the short-term and retrospective monitoring of lakes (water bodies) and Solonchaks (soils). These components of landscapes in the steppe biome of Western Siberia (WS) are indicators of ecosystem dynamics. The testing methods were consistently performed first at key sites, then over large areas of the steppe biome. Four key sites were selected for space-time monitoring of lakes and solonchaks of the south of the West Siberian Plain based on a series of multi-temporal satellite image. The plots are located submeridionally to reflect the change in climatic conditions from north to south, especially moisture, and their influence on the parameters of the objects investigated. The monitoring of lakes and Solonchaks was conducted on the basis of various satellite systems depending on the research scale. On the medium scale, Landsat and Spot imagery were used over a chronological interval of 20 years. The dynamics of indicators were studied on a small scale on 250 m Moderate Resolution Spectroradiometer images (MODIS). Special indices were developed to delineate the Solonchaks and water bodies on MODIS images. For the purposes of retrospective monitoring, ancient lake basins (50–60 thousand years old) were mapped using a complex method based on a combination of various data: geologic and topographic maps and RSD. The morphometric analysis was carried out on the basis of a Shuttle radar topographic mission (SRTM) digital model. Lakes of the mid-1970s and 1980s were also digitized from topographic maps. The results of the delineation of lakes on MODIS images were also used. The obtained monitoring results allow us to plot the increasing degradation of lakes and an increasing area of Solonchaks in the steppe biome of WS and, as a consequence, an increase in aridity. Combining paleogeographic data based on the analysis of SRTM, topographic maps of the last century, and more recent satellite imagery led to the conclusion that large bodies of water in arid became fragmented and then gradually dried out. Thus, the dynamics of ecosystems based on the selected indicator objects (lakes and Solonchaks) can be described not by a model of gradual change from south to north, but by a model of focal and discrete transformations throughout the area studied, regardless of their position on the submeridional transect. However, the analysis of the spatial distribution of objects-indicators in the region allows us to assess the situation more adequately and go from simplified models of the spatiotemporal dynamics of ecosystems due to the aridization of climate to more complex ones. The obtained results show that the methods based on GIS analysis of digital elevation models in conjunction with the processing of remote sensing data on all scales are effective for retrospective and current monitoring of ecosystem dynamics under the influence of global environmental changes. Proven technologies are promising to construct historical and current maps showing the status of individual objects (e.g., water and soil) of ecosystem by means of medium- and small-scale ecological mapping and environmental monitoring.