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The impacts of ‘05.6’ extreme flood event on riverine carbon fluxes in Xijiang River

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Chinese Science Bulletin 2007年第6期52卷 805-812页

作者： SUN HuiGuo HAN JingTai ZHANG ShuRong lu xixi Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Department of Geography National University of Singapore 117570 Singapore

An extreme flood event with a frequency of nearly 200 year occurred in June of 2005 in the Xijiang River, the main trunk stream of the Zhujiang River. Samples were systematically collected during the flood event, and water quality parameters, including total suspended sediment (TSS), dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) were analyzed, and riverine carbon concentrations associated with its changing pattern through the flood process were discussed. These parameters reflect the changes in basin surface flow and subsurface flow dur-ing the flood. This flood event influenced annual flux estimations of POC, DOC, and DIC to great extents. Based on carbon flux estimations for the year 2005 and the flood event (June 21-28) in the Xijiang River, it was found that DIC, DOC, and POC fluxes during ‘05.6’ flood event are 1.52×106 ***?2.a?1, 0.24×106 ***?2.a?1, and 0.54×106 ***?2.a?1, and account for 14.87%, 24.75% and 44.89% of the annual fluxes in 2005, respectively. The results suggested that carbon exports during extreme flood events had great contributions to the total carbon fluxes and composition of various carbon components, be-ing important for accurate estimates of annual carbon fluxes in rivers with frequent floods.

关键词：西江珠江洪水河流碳通量碳循环

Carbon sequestration in biomass and soil following reforestation:a case study of the Yangtze River Basin

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Journal of Forestry Research 2022年第5期33卷 1663-1690页

作者： Jianyu Wang Claudio O.Delang Guolong Hou Lei Gao Xiankun Yang xixi lu Department of Geography National University of Singapore1 Arts LinkKent RidgeSingapore 117570Singapore Department of Geography Hong Kong Baptist UniversityBaptist University RoadKowloon TongHong Kong 26679People’s Republic of China School of Geography South China Normal UniversityShipai CampusGuangzhou 510631People’s Republic of China Inner Mongolia Key Lab of River and Lake Ecology Inner Mongolia UniversityHohhot 010021People’s Republic of China School of Geographical Sciences Guangzhou UniversityGuangzhou 510006People’s Republic of China

The effect of reforestation on carbon sequestration has been extensively studied but there is less understanding of the changes that stand age and vegetation types have on changes in biomass carbon and soil organic carbon(SOC)after *** this study,150 reforested plots were sampled across six provinces and one municipality in the Yangtze River Basin(YRB)during 2017 and 2018 to estimate carbon storage in biomass and *** results illustrate that site-averaged SOC was greater than site-averaged biomass *** was more carbon sequestered in the biomass than in the *** carbon accumulated rapidly in the initial 20 years after *** contrast,SOC sequestration increased rapidly after 20 *** addition,evergreen species had higher carbon density in both biomass and soil than deciduous species and economic species(fruit trees).Carbon sequestration in evergreen and deciduous species is greater than in economic *** findings provide new evidence on the divergent responses of biomass and soil to carbon sequestration after reforestation with respect to stand ages and vegetation *** study provides relevant information for ecosystem management as well as for carbon sequestration and global climate change policies.

关键词： Biomass carbon Soil organic carbon Stand age Vegetation type Yangtze River Basin(YRB)

Runoff sensitivity to climate changes in the Longitudinal Range-Gorge Region （LRGR）： An example of the Longchuan Basin in the Upper Yangtze

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Chinese Science Bulletin 2006年第B11期51卷 88-96页

作者： ZHU Yunmei lu xixi ZHOU Yue LIONG Shie-Yui Department of Environmental Science Kunming University of Science & Technology Kunming 650093 China Department of Geography National University of Singapore 119260 Singapore Institute of Tropical Marine Science National University of Singapore 119260 Singapore

The sensitivity of runoff to the climate change in the Longitudinal Range-Gorge Region (LRGR) in southwest China was investigated with a case study in the Longchuan Basin of the upper Yangtze River, where the climate change is more complex due to the influences from both global warming and local topography. Non-updating artificial neural networks were calibrated and validated at the baseline condition and were used to predict the response of runoff under 25 hypothetical climate scenarios, which were generated by adjusting the baseline temperature by -1, 0, 1, 2 and 3 degrees C and by scaling rainfall by 0%, +/-+/- 10% and +/- 20%. The results indicated that runoff is more sensitive to the increase in rainfall. The annual and seasonal runoff changes were determined by the interaction between temperature and rainfall. At seasonal scale, the direction of change in runoff is more determined by temperature in winter and spring;whereas it is more determined by rainfall in summer and autumn. The LRGR in southwest China may experience a higher frequency of floods in the wet season and more serious droughts in the dry season, if a wetter summer and warmer winter is the trend of future climate change, as predicted by many GCMs.

关键词：径流气候变化人工神经网络中国西南部水文学

Spatiotemporal characteristics and driving mechanisms of land use/land cover(luLC)changes in the Jinghe River Basin,China

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Journal of Arid Land 2024年第1期16卷 91-109页

作者： WANG Yinping JIANG Rengui YANG Mingxiang XIE Jiancang ZHAO Yong LI Fawen lu xixi State Key Laboratory of Eco-hydraulics in Northwest Arid Region of China Xi'an University of TechnologyXi'an 710048China State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing 100038China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Department of Geography National University of SingaporeSingapore 117570Singapore

Understanding the trajectories and driving mechanisms behind land use/land cover(luLC)changes is essential for effective watershed planning and *** study quantified the net change,exchange,total change,and transfer rate of luLC in the Jinghe River Basin(JRB),China using luLC data from 2000 to *** trajectory analysis,knowledge maps,chord diagrams,and standard deviation ellipse method,we examined the spatiotemporal characteristics of luLC *** further established an index system encompassing natural factors(digital elevation model(DEM),slope,aspect,and curvature),socio-economic factors(gross domestic product(GDP)and population),and accessibility factors(distance from railways,distance from highways,distance from water,and distance from residents)to investigate the driving mechanisms of luLC changes using factor detector and interaction detector in the geographical detector(Geodetector).The key findings indicate that from 2000 to 2020,the JRB experienced significant luLC changes,particularly for farmland,forest,and *** the study period,luLC change trajectories were categorized into stable,early-stage,late-stage,repeated,and continuous change *** the stable change type,the late-stage change type predominated the luLC change trajectories,comprising 83.31% of the total change *** period 2010-2020 witnessed more active luLC changes compared to the period *** luLC changes exhibited a discrete spatial expansion trend during 2000-2020,predominantly extending from southeast to northwest of the *** driving factors on luLC changes included slope,GDP,and distance from *** interaction detection results imply either bilinear or nonlinear enhancement for any two driving factors impacting the luLC changes from 2000 to *** comprehensive understanding of the spatiotemporal characteristics and driving mechanisms of luLC changes offers valuable insights for the planning and sustainable management

关键词： land use/land cover(luLC)changes driving mechanisms trajectory analysis geographical detector(Geodetector) Grain for Green Project Jinghe River Basin

Greenhouse gas emissions from Daihai Lake,China:Should eutrophication and salinity promote carbon emission dynamics?

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Journal of Environmental Sciences 2024年第1期135卷 407-423页

作者： Xiangwei Li Ruihong Yu Jun Wang Heyang Sun Xinyu Liu Xiaohui Ren Shuai Zhuang Zhiwei Guo xixi lu Inner Mongolia Key Laboratory of River and Lake Ecology School of Ecology and EnvironmentInner Mongolia UniversityHohhot 010070China Key Laboratory of Mongolian Plateau Ecology and Resource Utilization Ministry of EducationHohhot 010070China Autonomous Region Collaborative Innovation Center for Integrated Management of Water Resources and Water Environment in the Inner Mongolia Reaches of the Yellow River Hohhot 010018China Department of Geography National University of Singapore117570Singapore

Greenhouse gases(GHGs)emitted or absorbed by lakes are an important component of the global carbon ***,few studies have focused on the GHG dynamics of eutrophic saline lakes,thus preventing a comprehensive understanding of the carbon ***,we conducted four sampling analyses using a floating chamber in Daihai Lake,a eutrophication saline lake in Inner Mongolia Autonomous Region,China,to explore its carbon dioxide(CO_(2))and methane(CH_(4))*** mean CO_(2)emission flux(FCO_(2))and CH_(4)emission flux(FCH_(4))were 17.54±14.54 mmol/m^(2)/day and 0.50±0.50 mmol/m^(2)/day,*** results indicated that Daihai Lake was a source of CO_(2)and CH_(4),and GHG emissions exhibited temporal *** mean CO_(2)partial pressure(p CO_(2))and CH_(4)partial pressure(p CH_(4))were 561.35±109.59μatm and 17.02±13.45μatm,which were supersaturated relative to the *** regression and correlation analysis showed that the main influencing factors of p CO_(2)were wind speed,dissolved oxygen(DO),total nitrogen(TN)and Chlorophyll a(Chl.a),whereas the main influencing factors of p CH_(4)were water temperature(WT),Chl.a,nitrate nitrogen(NO_(3)^(-)-N),TN,dissolved organic carbon(DOC)and water *** regulated carbon mineralization and organic matter decomposition,and it was an important influencing factor of p CO_(2)and p CH_(4).Additionally,the trophic level index(TLI)significantly increased p CH_(4).Our study elucidated that salinity and eutrophication play an important role in the dynamic changes of GHG ***,research on eutrophic saline lakes needs to be strengthened.

关键词： Eutrophication Salinity Greenhouse gas emissions Inland lake Inner Mongolia Autonomous Region

Changes of Water Discharge and Sediment Fluxes in Yunnan Mountains:With Reference to Longchuang River,Upper-stream of the Yangtz River

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Changes of Water Discharge and Sediment Fluxes in Yunnan Mou...

Pollution assessment of heavy metals along the Mekong River and dam effects

2004’全国土地资源态势与持续利用学术研讨会

作者： Zhou Yue lu xixi Huang Ying Faculty of Environmental Science and Engineering Kunming University of Science and Technology Department of Geography University of Singapore

Analysis indicates the lower reach of the Longchuangjiang produces lower water discharge but much higher sediment *** is mainly due to the dry-hot climate and the dissected terrain and the sparse vegetation downstream the ***,the basin as a whole has an unexpected lower sediment yield(luxes in recent 10 years,notably in the lower reach of the *** available evidences suggest that the water discharge and sediment fluxes increase in the wet seasons is due to local rainfall increase as a consequence of significant human activities such as expanding the irrigated land and increasing the reservoir storage capacity.

关键词： Water discharge sediment fluxes land use climate change Longchuangjiang China

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Journal of Geographical Sciences 2012年第5期22卷 874-884页

作者： FU Kaidao SU Bin HE Daming lu xixi SONG Jingyi HUANG Jiangcheng Asian International Rivers Center Yunnan University Kunming 650091 China Yunnan Key Laboratory for International Rivers and Transboundary Ecology Security Kunming 650091 China Department of Geography National University of Singapore 119260 Singapore

The resource development and changes of hydrological regime, sediment and water quality in the Mekong River basin have attracted great attentions. This research aimed to enhance the study on transboundary pollution of heavy metals in this international river. In this study, eight sampling sites were selected to collect the bed sand samples along the mainstream of the Mekong River. In addition, the contents of 5 heavy metal elements and their spatial variability along the mainstream of the river were analyzed. The geoaccumulation index （l^eo） and potential ecological risk analysis were employed to assess heavy metal pol- lution status in the mainstream of the Mekong River. The results show that the average con- tent of the heavy metal elements Zn is 91.43 mg/kg, Pb is 41.85 mg/kg, and As is 21.84 mg/kg in the bed sands of the Upper Mekong River, which are higher than those （Zn 68.17 mg/kg, Pb 28.22 mg/kg, As 14.97 mg/kg） in the Lower Mekong. The average content of Cr in the Lower Mekong is 418.86 mg/kg, higher than that in the Upper Mekong （42.19 mg/kg）. luang Prabang has a very high Cr concentration with 762.93 mg/kg and Pakse with 422.90 mg/kg. The concentration of Cu in all of the 8 sampling sites is similar, except for in Jiajiu with 11.70 mg/kg and Jiebei with 7.00 mg/kg. The results of the geoaccumulation index reveal that contaminations caused by Zn and Pb while Pb and As are more than those by Zn in Upper Mekong. Cr is the primary pollutant in the Lower Mekong, especially at luang Prabang and Pakse. Slight pollution with As also occurs in Pakse. The potential ecological risk index indi- cates that the potential ecological risk of heavy metals in the mainstream of the Mekong River is low. We argue that the pollution of water quality and contamination of heavy metals in bed sediment caused by mining of mineral resources or geochemical background values in the Mekong is not transmitted from the Upper to the Lower Mekong because of the reservoir sedimentation and

关键词： Mekong River basin heavy metal pollution geoaccumulation index potential ecological risk index

Carbon isotopic evidence for transformation of DIC to POC in the lower Xijiang River, SE China

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Carbon isotopic evidence for transformation of DIC to POC in...

Soil Erosion Changes over the Past Five Decades in the Red Soil Region of Southern China

中国科学院地质与地球物理研究所2015年度（第15届）学术年会

作者： Huiguo Sun Jingtai Han Shurong Zhang xixi lu Key Laboratory of Cenozoic Geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences College of Water Sciences Beijing Normal University Department of Geography National University of Singapore

The sources and dynamics of riverine carbon have been discussed extensively,but the transformation from inorganic carbon into organic carbon is still poorly *** this study,we conducted a comprehensive investigation on the riverine carbon,stable carbon isotopic composition and POC/PN(particulate nitrogen) ratio for different seasons,including an extreme flood event,in the lower Xijiang and its three *** carbon isotopic analyses are also performed for soil samples across the study *** decreases in δC and POC/PN have been observed for all the ***,the data obtained manifest a prominent positive shift of δC and negative shifts of bothδC and POC/PN from summer to *** observations suggest that the isotopic compositions of both DIC and POC are significantly affected by in-river primary production that converts DIC into organic matter through *** is estimated that the contribution of the riverine aquatic primary production to the riverine POC in the Xijiang and three tributaries of Guijiang,Hejiang and luoding is respectively 7.1%,43.2%,36.4%and 9.9%in rainy season,and 35.6%,47.3%,50.3%and 40.1%in dry *** on the stoichiometry involved in chemical weathering of the bedrocks,the transformation of the carbonate-sourced DIC to POC is 3.4-20.5%in rainy season,and 12.3-22.1%in dry *** transformation of DIC into POC implies an important sink of atmospheric CO in river systems and suggests a new mechanism for the old carbon effect in C age of aquatic-environmental sediments.

关键词： DIC(dissolved inorganic carbon) POC(particulate organic carbon) Soil organic carbon Stable carbon isotope Xijiang River

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Journal of Mountain Science 2010年第1期7卷 92-99页

作者： LIANG Yin LI Decheng lu xixi YANG Xuan PAN Xianzhang MU Huan SHI Deming ZHANG Bin Institute oj: Soil Science Chinese Academy of Sciences Nanjing 210008 China Department of Geography National University of Singapore Singapore 119260 Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil Science Chinese Academy of Sciences. Nanjing 210008 China

This paper reports the dynamic changes of soil and water loss in the red soil region of Southern China since the 1950s. The red soil region covers eight provinces: Jiangxi, Zhejiang, Fujian, Anhui, Hubei, Hunan, Guangdong and Hainan. From the 1950s to 1986, the annual rate of soil erosion increased by 3.4%. From 1986 to 1996 and from 1996 to 2000, the annual rates of soil erosion decreased by 2.0% and 0.32%, respectively. Field surveys showed that from 2000 to 2005, the area of soil and water loss decreased annually by 1.2%. This decrease was a result of large-scale erosion control activities across China. Although the eroded soil has been restored, the restoration process is very slow and full restoration will take a long time. Our report suggests that controlling soil and water loss is a challenging task, and additional measures must be taken to effectively control the soil erosion in the red soil region.

关键词： red soil region soil and water loss dynamic change remote sensing field samplingsurvey