• Effects of land use and cover change on surface wind speed in China

    分类: 地球科学 >> 地理学 提交时间: 2019-06-20 合作期刊: 《干旱区科学》

    摘要: The surface wind speed (SWS) is affected by both large-scale circulation and land use and cover change (LUCC). In China, most studies have considered the effect of large-scale circulation rather than LUCC on SWS. In this study, we evaluated the effects of LUCC on the SWS decrease during 1979–2015 over China using the observation minus reanalysis (OMR) method. There were two key findings: (1) Observed wind speed declined significantly at a rate of 0.0112 m/(s•a), whereas ERA-Interim, which can only capture the inter-annual variation of observed data, indicated a gentle downward trend. The effects of LUCC on SWS were distinct and caused a decrease of 0.0124 m/(s•a) in SWS; (2) Due to variations in the characteristics of land use types across different regions, the influence of LUCC on SWS also varied. The observed wind speed showed a rapid decline over cultivated land in Northwest China, as well as a decrease in China's northeastern and eastern plain regions due to the urbanization. However, in the Tibetan Plateau, the impact of LUCC on wind speed was only slight and can thus be ignored.

  • Land use and cover change and influencing factor analysis in the Shiyang River Basin, China

    分类: 地球科学 >> 地理学 提交时间: 2024-02-21 合作期刊: 《干旱区科学》

    摘要: Land use and cover change (LUCC) is the most direct manifestation of the interaction between anthropological activities and the natural environment on Earth's surface, with significant impacts on the environment and social economy. Rapid economic development and climate change have resulted in significant changes in land use and cover. The Shiyang River Basin, located in the eastern part of the Hexi Corridor in China, has undergone significant climate change and LUCC over the past few decades. In this study, we used the random forest classification to obtain the land use and cover datasets of the Shiyang River Basin in 1991, 1995, 2000, 2005, 2010, 2015, and 2020 based on Landsat images. We validated the land use and cover data in 2015 from the random forest classification results (this study), the high-resolution dataset of annual global land cover from 2000 to 2015 (AGLC-2000-2015), the global 30 m land cover classification with a fine classification system (GLC_FCS30), and the first Landsat-derived annual China Land Cover Dataset (CLCD) against ground-truth classification results to evaluate the accuracy of the classification results in this study. Furthermore, we explored and compared the spatiotemporal patterns of LUCC in the upper, middle, and lower reaches of the Shiyang River Basin over the past 30 years, and employed the random forest importance ranking method to analyze the influencing factors of LUCC based on natural (evapotranspiration, precipitation, temperature, and surface soil moisture) and anthropogenic (nighttime light, gross domestic product (GDP), and population) factors. The results indicated that the random forest classification results for land use and cover in the Shiyang River Basin in 2015 outperformed the AGLC-2000-2015, GLC_FCS30, and CLCD datasets in both overall and partial validations. Moreover, the classification results in this study exhibited a high level of agreement with the ground truth features. From 1991 to 2020, the area of bare land exhibited a decreasing trend, with changes primarily occurring in the middle and lower reaches of the basin. The area of grassland initially decreased and then increased, with changes occurring mainly in the upper and middle reaches of the basin. In contrast, the area of cropland initially increased and then decreased, with changes occurring in the middle and lower reaches. The LUCC was influenced by both natural and anthropogenic factors. Climatic factors and population contributed significantly to LUCC, and the importance values of evapotranspiration, precipitation, temperature, and population were 22.12%, 32.41%, 21.89%, and 19.65%, respectively. Moreover, policy interventions also played an important role. Land use and cover in the Shiyang River Basin exhibited fluctuating changes over the past 30 years, with the ecological environment improving in the last 10 years. This suggests that governance efforts in the study area have had some effects, and the government can continue to move in this direction in the future. The findings can provide crucial insights for related research and regional sustainable development in the Shiyang River Basin and other similar arid and semi-arid areas.