Catchment scale spatial variability of soil salt content in agricultural oasis, Northwest China

Soil salinization is a serious environmental problem in the world, especially in arid and semi-arid regions. Therefore, estimating spatial variability of soil salinity plays an important role in environmental sciences. Aiming at the problem of soil salinization inside an oasis, a case study was carried out at the Sangong River catchment in Xinjiang province, northwest China. Methods of classical statistics, geostatistics, remote sensing (RS) and geographic information system (GIS) were applied to estimate the spatial variability of soil salt content in the topsoil (0-20 cm) and its relationship with landscape structure at catchment scale. The objective of this study was to provide a scientific basis to understand the heterogeneous of spatial distribution of soil salt content at a large scale. The results revealed that (1) elevation of landform was a key factor for soil salt content's spatial variability, and soil salt content had a strong spatial autocorrelation, which was mainly induced by structural factors. (2) Mapping of soil salt content by Kriging and comparing it with landscape maps showed that area of soil salinization in old oasis was smaller than that in new oasis, and degree of soil salinization in old oasis was also lower than that in the new one. Among all landscapes, cropland was mostly affected by salinity, with 38.8% of the cropland in new oasis moderately affected by soil salinity, and 8.54% in old oasis

Dynamic characteristics of land degradation development in agricultural oasis of desert-oasis ecotone

To explore the evaluation of land degradation in agricultural region of desert-oasis ecotone, the spatial heterogeneity of topsoil (0-20 cm) and the relationship of such heterogeneity and land use type were studied using a combination of semivariogram and GIS methods. Results show that the development of oasis can be divided into four stages, i.e., excessive land reclamation, moderate land use, land abandonment, land integrated management; human activities are the key factor that results in the increasing of landscape diversity and the fractionizing of the landscape in the last 23 years; from 1983 to 2005, the extent of land degradation was heavier in the area near desert resign than that in oasis; the area of land degradation in gray desert soil was larger than that in solonchak soil and aquert soil, and land degradation was weaker in the regions of bad quality than that in the regions of good quality. (31 refs.

Temporal-spatial change in soil degradation and its relationship with landscape types in a desert-oasis ecotone: a case study in the Fubei region of Xinjiang Province, China

Desert-oasis ecotone is an interactive area between desert and oasis ecosystems which plays an important role in ensuring oasis ecological security and maintaining oasis internal stabilization. The studied region had experienced dramatic landscape change and soil degradation during the 20th century, especially in the last two decades. To document the status and evaluate this degradation process, geostatistics and GIS map algebra were used to quantify the temporal-spatial changes in landscape pattern and soil degradation from 1983 to 2005. The results showed that: (1) the change of landscape pattern due to human activities was the key reason responsible for the increasing of landscape diversity and fragmentation; (2) the extent of soil degradation was higher near desert ecosystem than oasis, and human activities were the major driving forces in ameliorating the soil properties; and (3) soil degradation is weaker in regions of bad soil quality than regions of good soil quality due to both human activities and natural processes

Corridor effect of the spatial changes of landscape patterns in and areas: A case study of the river corridor areas in the middle and lower reaches of Tarim River

The river corridor areas in the middle and lower reaches of the Tarim River are dominated by the traditional green corridors along the river section from the Qara Reservoir in Yuli County to the Taitema Lake in Ruoqiang County, which plays an important role in the social and economic development in the Tarim River Watershed with a extremely significant ecological functions. The buffer zones perpendicular to the watercourse were defined along both riversides at a 5-km interval beginning from the watercourse (10 km wider) using the method of the buffer zone analysis. The landscape pattern indexes of each buffer zone were calculated, and the indexes of the main landscape patterns were analyzed so as to reveal the radiative effect and the characteristics of the river corridors on landscape and patch levels. The results show that the radiative width is generally 30 km in the study area, and can be up to 50-70 km in sub-region FG1 because the study area is located in two drainage basins, with an ecological interstitial zone between them. The landscapes of woodlands and wetlands are generally distributed within the 10 km buffer zone (it means that the buffer zone is 5 km away from the watercourse; the same hereafter) along both riversides. Moreover, the closer the buffer zone is to the watercourse, the higher the patch density and the largest patch index are. In the ecological and environmental regeneration for the study area, the extent of ecological effect of the river corridors must be fully considered, and the projects must be scientifically and rationally planned and designed