scholarly journals Study on streamflow response to land use change over the upper reaches of Zhanghe Reservoir in the Yangtze River basin

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Yuqi Chen ◽  
Jun Niu ◽  
Yuqing Sun ◽  
Qi Liu ◽  
Sien Li ◽  
...  
Author(s):  
Rui Han ◽  
Luo Guo ◽  
NuanYin Xu ◽  
Dan Wang

The Eastern Sichuan Region (ESR) is one of the key pilot regions for Grain for Green Program (GGP) implementation in the upper reaches of the Yangtze River basin in China. Therefore, monitoring the effect of the GGP on the ecosystem in the ESR is important. In this study, the Mann–Kendall Trend Test Model was used to ascertain the changes in vegetation coverage. The transfer matrix was used to explore the changes in Land Use/Land Cover (LULC). LULC change direction model (LCDM) was used to preliminarily assess the impact of LULC changes on the ecosystem. The Pressure–State–Response model (PSR), reflecting the human pressure and the ecosystem state, was applied to analyze the spatial–temporal characteristics of the ecosystem health index (EHI). The time span of this study was from 1990 to 2015. The results show that the vegetation coverage changed significantly (p < 0.05), and ecosystem function developed towards positive because of the increase in the coverage of forestland and water land and decrease in the coverage of farmland. The spatial distribution of the EHI was influenced by the pattern of land use. The eastern region, associated with a large area of forestland and grassland, has a low population density and a low degree of land use exploitation, resulting in a high EHI value. The situation was completely opposite in the western region. Regarding the temporal scale, in spite of the decreasing pressure indicator, most counties had experienced an increase in the EHI. There was a clear correlation between the increased EHI values and the restored areas at the third stage (2000–2005) (p < 0.05, r2 = 0.164), but this correlation disappeared at the latter stage (2005–2015) (p > 0.05). The changes showed significant variations in time and area because of differences in the process and the intensity of the implication of the GGP.


2020 ◽  
Author(s):  
Wei Li ◽  
Lu Li ◽  
Jie Chen ◽  
Qian Lin ◽  
Hua Chen

Abstract. Land use and cover has been significantly changed all around the world during the last decade. In particular, the Returning Farmland to Forest Program (RFFP) have resulted in significant changes in regional land use and cover, especially in China. The land use and cover change (LUCC) may lead to the change in regional climate. In this study, we take the Yangtze river basin as a case study and analyze the impacts of LUCC and reforestation on summer rainfall amount and extremes based on the Weather Research and Forecasting model. Firstly, two observed land use and cover scenarios (1990 and 2010) were chosen to investigate the impacts of LUCC on the summer rainfall during the last decade. Secondly, two hypothetical reforestation scenarios (i.e., scenarios of 20 % and 50 % cropland changed to be forest) were taken based on the control year of 2010 to test the sensitivity of summer rainfall (amount and extremes) to reforestation. The results showed that LUCC between 1990 and 2010 decreased average summer rainfall, while increased extreme summer daily rainfall in the Yangtze River basin. The extreme summer daily rainfall increased up to 50 mm, which was mainly observed in the midstream and downstream. Reforestation could increase summer rainfall amount and extremes, and the effects were more pronounced at the local scale where suffered reforestation than at the whole basin. Moreover, the effects of reforestation were influenced by the reforestation proportion. In this study, the average summer rainfall increased more for the scenario of 20 % croplands changed to forests than that for the scenario of 50 %, while the high-intensity short-duration rainfall increased more for the scenario of 50 % croplands changed to forests than that for the scenario of 20 %. Although a comprehensive assessment of the impacts of LUCC on summer rainfall amount and extremes was conducted, further studies are needed to better investigate the uncertainty.


2021 ◽  
Vol 25 (8) ◽  
pp. 4531-4548
Author(s):  
Wei Li ◽  
Lu Li ◽  
Jie Chen ◽  
Qian Lin ◽  
Hua Chen

Abstract. Land use and cover have been significantly changed all around the world during the last decade. In particular, the Grain for Green (GG) program has resulted in significant changes in regional land use and cover, especially in China. Land use and cover change (LULCC) may lead to changes in regional climate. In this study, we take the Yangtze River basin as a case study and analyze the impacts of LULCC and reforestation on summer rainfall amounts and extremes based on the Weather Research and Forecasting model. Firstly, two observed land use and cover scenarios (1990 and 2010) were chosen to investigate the impacts of LULCC on summer rainfall during the last decade. Secondly, two hypothetical reforestation scenarios (i.e., scenarios of 20 % and 50 % cropland changed to forest) were taken based on the control year of 2010 to test the sensitivity of summer rainfall (amounts and extremes) to reforestation. The results showed that average summer rainfall and extreme summer daily rainfall decreased in the Yangtze River basin between 1990 and 2010 due to LULCC. Reforestation could increase summer rainfall amount and extremes, and the effects were more pronounced in populated areas than over the whole basin. Moreover, the effects of reforestation were influenced by the reforestation proportion. In addition, the summer rainfall increased less conversely, with the transform proportion of cropland to forest increased from 20 % to 50 %. By analyzing the changes in water vapor mixing ratio, upward moisture flux, and 10 m wind, it is suggested that this result might be caused by the horizontal transportation processes of moisture. Although a comprehensive assessment of the impacts of LULCC on summer rainfall amounts and extremes was conducted, further studies are needed to investigate the uncertainty better.


Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 731
Author(s):  
Zhuoqing Hao ◽  
Jixia Huang ◽  
Yantao Zhou ◽  
Guofei Fang

The Yangtze River Basin is among the river basins with the strongest strategic support and developmental power in China. As an invasive species, the pinewood nematode (PWN) Bursaphelenchus xylophilus has introduced a serious obstacle to the high-quality development of the economic and ecological synchronization of the Yangtze River Basin. This study analyses the occurrence and spread of pine wilt disease (PWD) with the aim of effectively managing and controlling the spread of PWD in the Yangtze River Basin. In this study, statistical data of PWD-affected areas in the Yangtze River Basin are used to analyse the occurrence and spread of PWD in the study area using spatiotemporal visualization analysis and spatiotemporal scanning statistics technology. From 2000 to 2018, PWD in the study area showed an “increasing-decreasing-increasing” trend, and PWD increased explosively in 2018. The spatial spread of PWD showed a “jumping propagation-multi-point outbreak-point to surface spread” pattern, moving west along the river. Important clusters were concentrated in the Jiangsu-Zhejiang area from 2000 to 2015, forming a cluster including Jiangsu and Zhejiang. Then, from 2015–2018, important clusters were concentrated in Chongqing. According to the spatiotemporal scanning results, PWD showed high aggregation in the four regions of Zhejiang, Chongqing, Hubei, and Jiangxi from 2000 to 2018. In the future, management systems for the prevention and treatment of PWD, including ecological restoration programs, will require more attention.


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