Spatio-temporal changes in oases in the Heihe River Basin of China: 1963–2013

Abstract

Artificial oases have flourished as human activities have intensified. Changes in oases in the Heihe River Basin are typical for the arid areas of China. Based on images from 14 separate periods during 1963-2013 that were compiled from multi-sensors, data on the boundaries of oases were extracted using the methods of object-oriented image segmentation and Normalized Difference Vegetation Index thresholds as well as visual interpretation. Based on extracted data, the spatio-temporal changes in oases were analyzed using models i.e. grid transformed model for rate of change. The drivers were analyzed based on data from Statistics Yearbooks and field surveys. The results show that from 1963 to 2013 sprawl dominated oasis evolution and occurred not only in the surroundings but also in interior patches. Oasis evolution patterns of "unchanged," "expanding," "shrinking" and "oscillating" were observed.

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

“…This study showed that the total oasis area increased in the Hexi Corridor over the past 30 years. This result is consistent with the results reported in HHRB [9], in SYRB [35] and in SLRB [53]. The trend was similar in other arid areas such as the Sangong River basin and the Hotan oasis [54] of Xinjiang in north-west china [55].…”

“…Changes in oases over time are characterized by the rate of change between the start and end times [34,35]. LULC change models, such as the single dynamic degree (SDD) model and the bidirectional dynamic degree (BDD) model, are widely used to analyze changes in oases [2,9,34]. The SDD model describes the rate of net change, but it neglects the increasing and decreasing components during the evolution.…”

“…As a result, this program played a certain positive role with regards to groundwater resource recovery [17]. In order to protect ecological balance and to realize sustainable development, conservation policies, such as the 'Three North Shelterbelt', the 'Grain for Green' project, the 'natural forest protection project' and the 'comprehensive management plan for the ecological protection and construction' of the Qianlian mountains proposed in recent years, have been and will continue to have a profound impact on the sustainability of oases [9,23,24,35,57,60]. After 2000, the 'Great Western Development strategy', the 'Canceling Agricultural Tax', the 'New Rural Development strategy', and the 'National Ecological Civilization' construction have had a profound impact on the regional economy and sustainability of oases in the Hexi Corridor.…”

“…Oases are unique landscapes in the context of the desert environment that occur in dry climates and supported natural or artificial rivers. Oases, which have greater productivity than the surrounding deserts, are a land type that is adequate for human settlements because of the availability of fertile soil, fresh groundwater and surface runoff from nearby mountains [9]. The oases in China are concentrated in the arid regions west of the Helan Mountain-Wushaoling line, and they are connected with other oases in central Asia.…”

Spatiotemporal Changes of Vegetation in the Middle Draa Valley Oasis: A Study Case of M’hamid El Ghizlane Oasis (Morocco)

“…An oasis is an isolated green fertile land in a desert that often surrounds a water source such as a spring; it provides habitat for animals, and sometimes humans (Xie et al, 2015). The main landscapes of oases in Morocco are vegetation especially palm trees, rivers and settlements.…”