Spatio-Temporal Changes of Oases in the Hexi Corridor over the Past 30 Years

Abstract

In recent decades, the oases in the Hexi Corridor have gone through a tremendous transformation, which has caused a series of social and environmental problems. We aim to explore quantitatively the characteristics of the oasis expansion and their dynamic mechanism(s) in the Hexi Corridor, and their implications and impact on current and future policies. The spatial distribution pattern and dynamic changes experienced by the oases are examined using Landsat imagery. Their spatio-temporal changes are analyzed using the grid-transformed model and the dynamic-degree model. The model drivers are analyzed based on data from statistics yearbooks and field surveys. The total area of oases in the Hexi Corridor has expanded tremendously during the last 30 years from 10,709 km2 to 14,950 km2, almost 40% of the original value. Oasis evolution patterns of ‘unchanged’, ‘expanding’, ‘shrinking’, and ‘oscillating’ are observed at different periods in the three basins. In terms of area, almost half of the oases experienced some change, where most of the changes took place in the ecotone between oases and deserts, and the interior of oases due to the reclamation of abandoned land. Oasis expansion is mainly determined by the human instincts for survival and well-being, which are generally governed by population growth, agricultural policies and economic development. These changes reflect the need to find a balance in the relationship between ecological protection and increasing the well-being of local residents, because unreasonable or excessive development and utilization will cause damage to the local ecological environment.

Detecting Patterns of Vegetation Gradual Changes (2001–2017) in Shiyang River Basin, Based on a Novel Framework

“…A large part of farmlands around the cities and towns had been transformed into urban areas, which caused significant logistic decreasing patterns during 2001-2017. Since there are obvious spatial differences in time at which agricultural oases expended [39], different increasing patterns were found in the newly reclaimed oases. The logarithmic increasing patterns were found in the north part of the transition zones between Liangzhou oasis and Tengger Desert (Site g in Figure 8), and the southern edge of Tengger Desert where were continually reclaimed as oases since 1990s.…”

“…76.48% of vegetation changes in the logistic pattern lasted less than 4 years. Areas with a duration over 8 years (5.38%) were mainly concentrated in the continuously reclaimed agricultural oases [39].…”

“…More than half (51.19%) of logistic patterns possessed a continuous change interval of two years ( Figure 6. b and histogram below b). The longer vegetation changes lasted, the smaller the propouously reclaimed agricultural oases [39].…”

Understanding the attributes of the dual oasis effect in an arid region using remote sensing and observational data

“…The oases of the HCOD are beaded along a long and narrow passage, with a width of 40-100 km and stretching for 1,120 km from east to west, with an area of 27.6 × 10 4 km 2 ( Figure 1). The Hexi Corridor had a population of 4.92 million spread over 19 counties in 2014 (Xie et al 2018). The HCOD is in a convergence zone of monsoon and continental climates, which is characterized by its distinct cold and arid landscapes, which contain scattered settlements, shrubland, grassland, cropland, water bodies, and deserts, as illustrated in Figure 1(b).…”

“…The HCOD is in a convergence zone of monsoon and continental climates, which is characterized by its distinct cold and arid landscapes, which contain scattered settlements, shrubland, grassland, cropland, water bodies, and deserts, as illustrated in Figure 1(b). The region has an arid continental climate with an annual rainfall reaching no more than 200 mm that mainly occurs in summer; whereas the annual potential evaporation is between 1,500 and 3,200 mm (Xie et al 2018). The altitude of the HCOD decreases from the southern mountains (over 3,000 m) toward the northern convergence zone (2,000-1,300 m) (Figure 1(a)).…”