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spatial-temporal dynamics of desert vegetation and its responses to climatic variations over the last three decades:a case study of Hexi region in Northwest China

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Journal of Arid Land 2016年第4期8卷 556-568页

作者： YANG Xuemei LIU Shizeng YANG Taibao XU Xianying KANG Caizhou TANG Jinnian WEI Huaidong Mihretab G GHEBREZGABHER LI Zhiqi State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating Gansu Desert Control Research Institute Institute of Glaciology and Ecogeography College of Earth and Environmental SciencesLanzhou University Eritrea Institute of Technology College of Education Wuwei Natural Protection Station the Management Bureau of Gansu Qilianshan National Nature Reserve

Analysis of spatial-temporal variations of desert vegetation under the background of climate changes can provide references for ecological restoration in arid and semi-arid areas. In this study, we used the Global Inventory Modeling and Mapping Studies （GIMMS） NDVI data from 1982 to 2006 and Moderate Resolution Imaging Spectroradiometer （MODIS） NDVI data from 2000 to 2013 to reveal the dynamics of desert vegetation in Hexi region of Northwest China over the past three decades. We also used the annual temperature and precipitation data acquired from the Chinese meteorological stations to analyze the response of desert vegetation to climatic variations. The average value of NDVImax （the maximum NDVI during the growing season） for desert vegetation in Hexi region increased at the rate of 0.65x10-3/a （P〈0.05） from 1982 to 2013, and the significant increases of NDVImax mainly appeared in the typical desert vegetation areas. Vegetation was significantly improved in the lower reaches of Shule and Shiyang river basins, and the weighted mean center of desert vegetation mainly shifted toward the lower reaches of the two basins. Almost 95.32% of the total desert vegetation area showed positive correlation between NDVImax and annual precipitation, indicating that precipitation is the key factor for desert vegetation growth in the entire study area. Moreover, the areas with non-significant positive correlation between NDVImax and annual precipitation mainly located in the lower reaches of Shiyang and Shule river basins, this may be due to human activities. Only 7.64% of the desert vegetation showed significant positive correlation between NDVImax and annual precipitation in the Shule River Basin （an extremely arid area）, indicating that precipitation is not the most important factor for vegetation growth in this basin, and further studies are needed to investigate the mechanism for this phenomenon.

关键词： desert vegetation NDVI global warming spatial-temporal variations Hexi region

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Seasonal variations in glacier velocity in the High Mountain Asia region during 2015–2020

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Journal of Arid Land 2023年第6期15卷 637-648页

作者： ZHANG Zhen XU Yangyang LIU Shiyin DING Jing ZHAO Jinbiao School of Geomatics Anhui University of Science and TechnologyHuainan 232001China Institute of International Rivers and Eco-Security Yunnan UniversityKunming 650091China

Velocity is an important component of glacier dynamics and directly reflects the response of glaciers to climate *** a result,an accurate determination of seasonal variation in glacier velocity is very important in understanding the annual variation in glacier ***,few studies of glacier velocity in the High Mountain Asia(HMA)region were *** these lines,in this work,based on Sentinel-1 glacier velocity data,the distribution of glacier velocity in the HMA region was plotted and their seasonal variations during 2015-2020 were systematically *** average glacier velocity in the HMA region was 0.053 m/d,and was positively correlated with the glacier area and *** in the Karakoram Mountains had the fastest average flow velocity(0.060 m/d),where the glaciers exhibited the largest average area and average ***,glaciers in the GangdisêMountains had the slowest velocity(0.022 m/d)and the smallest average glacier *** glacier flows were the fastest in spring(0.058 m/d),followed by summer(0.050 m/d),autumn(0.041 m/d),and winter(0.040 m/d).In addition,the glacier flows were the maximum in May,being 1.4 times of the annual average *** some areas,such as the Qilian,Altun,Tibetan Interior,Eastern Kunlun,and Western Kunlun mountains,the peak glacier velocities appeared in June and *** glacier velocity in the HMA region decreased in midsummer and reached the minimum in December when it was 75%of the annual *** results highlight the role of meltwater in the seasonal variation in glacier flows in late spring and early *** seasonal velocity variation of lake-terminating glaciers was similar to that of land-terminating ones,but the former flowed *** velocity difference close to the mass balance line between the lake-and land-terminating glaciers was obviously greater in spring than in other *** summer,the difference between the lake-and land-terminating glaciers at a normalized distance

关键词： glacier velocity spatial-temporal variations High Mountain Asia synthetic aperture radar offset-tracking climate change

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Using hydrochemical signatures to characterize the long-period evolution of groundwater information in the Dagu River Basin,China

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Frontiers of Environmental Science & Engineering 2021年第5期15卷 311-323页

作者： Ziyue Yin Qing Lin Shaohui Xu School of Environmental Science and Engineering Qingdao UniversityQingdao266071China

The evolution of hydrochemical compositions influenced by long-period interactions between groundwater and the geo-environment is a fundamental issue for exploring groundwater quality and *** study systematically investigated the hydrochemical processes and anthropogenic interference occurring in the river basin by bivariate plots,Gibbs diagrams,saturation index,and the major ions *** changes in groundwater hydrochemistry have been observed in the study area,illustrating the origins of major ions are affected by various internal and external *** highlighted that TDS varied from freshwater to brackish water,ranging between 187.90 and 2294.81 mg/***^(2+)and HCO_(3)^(−)are the dominant ions in the studied *** results gained by Gibbs diagrams,bivariate plots,saturation index,and the major ions ratios demonstrated that minerals dissolution/precipitation,cation exchange,and human inputs play crucial roles in the unconfined ***,the overuse of nitrogen fertilizer,livestock manure,and industrial/domestic sewage led to nitrate and nitrite contamination and brought significant challenges to the surrounding *** present study could make an unambiguous identification of natural processes and anthropogenic interventions influencing groundwater hydrochemistry’s long-period evolution and create a preliminary strategy for groundwater resources management.

关键词： Groundwater quality Hydrochemical signatures spatial-temporal variations Water-rock interactions Anthropogenic interventions

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Statistical characteristics of chlorophyll-a concentration in Hong Kong's coastal waters

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Journal of Geographical Sciences 2002年第3期12卷 331-342页

作者： CHEN Xiaoling, Yok Sheung Li, LI Zhilin(1. Dept. of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, China 2. National Laboratory for Information Engineering in Surveying, Mapping and Remote Sensing (LIESMARS), Wuhan Uni Dept. of Civil and Structural Engineering The Hong Kong Polytechnic University 香港 Wuhan University National Laboratory for Information Engineering in Surveying Mapping and Remote Sensing (LIESMARS) Wuhan 430072 Dept. of Land Surveying & Geo-Informatics The Hong Kong Polytechnic University 香港

In this paper seven of the ten Water Control Zones (WCZs) in Hong Kong's coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors. Cluster analysis was employed to group the monitoring stations based on the structure of the data set. Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level. The results suggest that all the monitoring stations could be grouped into two clusters. Cluster Ⅰ with frequent red tide incidents comprises two WCZs which are semi-enclosed bays. Cluster Ⅱ with less red tide occurrence comprises the other five WCZs in an estuarine environment in the west. For both clusters, the organic contents indicator, BODS, was a common significant influencing factor of the chlorophyll-a level. Nitrogen and light penetration condition related to turbidity, total volatile solids and suspended solids had more influence on the cholophyll-a level in Cluster Ⅰ than in Cluster Ⅱ, while phosphorus and oceanographic conditions associated with salinity, temperature, dissolved oxygen and pH were more important in Cluster Ⅱ than in Cluster Ⅰ. Generally, there was a higher average chlorophyll-a level in winter and autumn in a year. The chlorophyll-a level was much higher in Cluster Ⅰ than in Cluster Ⅱ among all seasons. Although the chlorophyll-a concentration had great variations from place to place in Hong Kong's coastal waters, it seemed to have a common long term fluctuation period of 8-10 years with a high-low-high variation in the period in the whole region, which might be influenced by other factors of global scale.

关键词： Hong Kong's coastal waters chlorophyll-a concentration spatial-temporal variations

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Dominant Macroalgae in Bahía de Cochinos, Matanzas, Cuba

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American Journal of Plant Sciences 2022年第6期13卷 797-814页

作者： Yusimí Alfonso Patricia González Sánchez Hansel Caballero Aragón Pedro Chevalier Jhoana Díaz-Larrea Ruben Cabrera Acuario Nacional de Cuba La Habana Cuba Unidad Iztapalapa Departamento de Hidrobiología Universidad Autónoma Metropolitana Cd de México México Gabinete de Arqueología Oficina del Historiador de la Ciudad Habana Vieja Cuba

spatial-temporal variations of macroalgae were analyzed in a study conducted in Cueva de Los Peces (CP) and Punta Perdiz (PP), two dive sites located on the eastern coast of Bahía de Cochinos. The most conspicuous species found from 3 to 20 m depths were present in the biotopes of ridges and shallow and deep terraces. Sampling was carried out in September 2014, and March and October 2016 by autonomous diving and direct methods. Qualitative visual censuses and quantitative analyzes were used to estimate the coverage (%) of the genera according to the AGRRA methodology with the use of the 10 m linear transect and quadrats as the sampling unit. The first list of macroalgae for the area is offered that includes 49 taxa of which 10 were Rhodophyta, 10 Ochrophyta (Phaeophyceae), and 29 Chlorophyta. The dominant genera during the study period were Halimeda, Dictyota, Lobophora, and Udotea. spatial differences were found regarding the specific composition. temporal variations were evidenced in terms of the relative abundance of the genera present, which reveals temporal changes in the qualitative structure, where some species replace others. The information obtained is pioneering and can serve as a comparative baseline for future monitoring of the area.

关键词： Cuba Macroalgae spatial-temporal variations Species List

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