分类： 地球科学 >> 地理学 提交时间： 2024-05-15 合作期刊: 《干旱区科学》
摘要： Weihe River basin is of great significance to analyze the changes of land use pattern and landscape ecological risk and to improve the ecological basis of regional development. Based on land use data of the Weihe River basin in 2000, 2010, and 2020, with the support of Aeronautical Reconnaissance Coverage Geographic Information System (ArcGIS), GeoDa, and other technologies, this study analyzed the spatial-temporal characteristics and driving factors of land use pattern and landscape ecological risk. Results showed that land use structure of the Weihe River basin has changed significantly, with the decrease of cropland and the increase of forest land and construction land. In the past 20 a, cropland has decreased by 7347.70 km2, and cropland was mainly converted into forest land, grassland, and construction land. The fragmentation and dispersion of ecological landscape pattern in the Weihe River basin were improved, and land use pattern became more concentrated. Meanwhile, landscape ecological risk of the Weihe River basin has been improved. Severe landscape ecological risk area decreased by 19,177.87 km2, high landscape ecological risk area decreased by 3904.35 km2, and moderate and low landscape ecological risk areas continued to increase. It is worth noting that landscape ecological risks in the upper reaches of the Weihe River basin are still relatively serious, especially in the contiguous areas of high ecological risk, such as Tianshui, Pingliang, Dingxi areas and some areas of Ningxia Hui Autonomous Region. Landscape ecological risk showed obvious spatial dependence, and high ecological risk area was concentrated. Among the driving factors, population density, precipitation, normalized difference vegetation index (NDVI), and their interactions are the most important factors affecting the landscape ecological risk of the Weihe River basin. The findings significantly contribute to our understanding of the ecological dynamics in the Weihe River basin, providing crucial insights for sustainable management in the region.
分类： 地球科学 >> 地理学 提交时间： 2021-06-04 合作期刊: 《干旱区科学》
摘要： Changes in atmospheric aerosols have profound effects on ecosystem productivity, vegetation growth and activity by directly and indirectly influencing climate and environment conditions. However, few studies have focused on the effects of atmospheric aerosols on vegetation growth and activity in the vulnerable arid and semi-arid regions, which are also the source areas of aerosols. Using the datasets of aerosol optical depth (AOD), normalized difference vegetation index (NDVI) and multiple climatic variables including photosynthetically active radiation (PAR), surface solar radiation (SSR), surface air temperature (TEM) and total precipitation (PRE), we analyzed the potential responses of vegetation activity to atmospheric aerosols and their associated climatic factors in arid and semi-arid regions of Asia from 2005 to 2015. Our results suggested that areas with decreasing growing-season NDVI were mainly observed in regions with relatively sparse vegetation coverage, while AOD tended to increase as NDVI decreased in these regions. Upon further analysis, we found that aerosols might exert a negative influence on vegetation activity by reducing SSR, PAR and TEM, as well as suppressing PRE in most arid and semi-arid regions of Asia. Moreover, the responses of atmospheric aerosols on vegetation activity varied among different growing stages. At the early growing stage, higher concentration of aerosol was accompanied with suppressed vegetation growth by enhancing cooling effects and reducing SSR and PAR. At the middle growing stage, aerosols tended to alter microphysical properties of clouds with suppressed PRE, thereby restricting vegetation growth. At the late growing stage, aerosols exerted significantly positive influences on vegetation activity by increasing SSR, PAR and TEM in regions with high anthropogenic aerosols. Overall, at different growing stages, aerosols could influence vegetation activity by changing different climatic factors including SSR, PAR, TEM and PRE in arid and semi-arid regions of Asia. This study not only clarifies the impacts of aerosols on vegetation activity in source areas, but also explains the roles of aerosols in climate.
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