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Temporal and Spatial Variation Characteristics of Precipitation during Crop Growing Season in Northeast China 被引量:2
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作者 李秀芬 李帅 +2 位作者 纪瑞鹏 郭春明 姜丽霞 《Agricultural Science & Technology》 CAS 2010年第6期137-140,168,共5页
[Objective] The aims were to understand variation characteristics of water resources and provide theoretical guidance for the formulation of agricultural irrigation methods.[Method] Taking the precipitation records du... [Objective] The aims were to understand variation characteristics of water resources and provide theoretical guidance for the formulation of agricultural irrigation methods.[Method] Taking the precipitation records during crop growing season(from April to September)observed by 177 weather stations from 1971 to 2008 in the three provinces of Northeast China(Heilongjiang,Jilin and Liaoning)as research data,annual change and spatial distribution characteristics of precipitation during crop growing season were analyzed by means of small grid interpolation and climatic trend rate.[Result] The precipitation during crop growing season general exhibited the decreasing trend and the precipitation trend rate was-8.6 mm/10a in Northeast China.In addition,there was lack of rain from 1971 to 1980 and relatively abundant of rain during 1981 and 1990 respectively.Moreover,the precipitation obviously exhibited decreasing trend from 1991 to 2008.But the decreasing trend was inconsistent in spatial distributions,that was,the precipitation slightly increased in relatively rainless areas and obviously decreased in relatively rainy areas.[Conclusion] The areas with obvious decreasing trend of precipitation during crop growing season are the main grain producing zones in Northeast China,so the problem of food production security caused by the precipitation changes should be paid enough attention. 展开更多
关键词 Regions in the Northeast China Precipitation during crop growing season temporal and spatial variations
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Analysis on Temporal and Spatial Characteristic and Variation of Precipitation in Ningxia Hui Autonomous Region 被引量:1
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作者 陈海波 严华生 +2 位作者 苏发奋 杨继祖 鲁统亮 《Meteorological and Environmental Research》 CAS 2010年第10期47-52,57,共7页
Based on seasonal and annual observed precipitation data at 19 meteorological stations in Ningxia Hui Autonomous Region,the temporal and spatial distribution characteristic is analyzed by EOF method.And spatial charac... Based on seasonal and annual observed precipitation data at 19 meteorological stations in Ningxia Hui Autonomous Region,the temporal and spatial distribution characteristic is analyzed by EOF method.And spatial characteristics and temporal changes trends of EOF of seasonal and annual precipitation have been showed.The main period and sudden changes point of EOF of annual precipitation have been studied by Mann-Kendall and spectrum analysis method. 展开更多
关键词 PRECIPITATION temporal-spatial Distribution variation Ningxia China
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Layer chicken microbiota:a comprehensive analysis of spatial and temporal dynamics across all major gut sections
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作者 Yadav Sharma Bajagai Thi Thu Hao Van +3 位作者 Nitish Joat Kapil Chousalkar Robert J.Moore Dragana Stanley 《Journal of Animal Science and Biotechnology》 SCIE CAS CSCD 2024年第3期1056-1070,共15页
Background The gut microbiota influences chicken health,welfare,and productivity.A diverse and balanced microbiota has been associated with improved growth,efficient feed utilisation,a well-developed immune system,dis... Background The gut microbiota influences chicken health,welfare,and productivity.A diverse and balanced microbiota has been associated with improved growth,efficient feed utilisation,a well-developed immune system,disease resistance,and stress tolerance in chickens.Previous studies on chicken gut microbiota have predominantly focused on broiler chickens and have usually been limited to one or two sections of the digestive system,under con-trolled research environments,and often sampled at a single time point.To extend these studies,this investigation examined the microbiota of commercially raised layer chickens across all major gut sections of the digestive system and with regular sampling from rearing to the end of production at 80 weeks.The aim was to build a detailed picture of microbiota development across the entire digestive system of layer chickens and study spatial and temporal dynamics.Results The taxonomic composition of gut microbiota differed significantly between birds in the rearing and pro-duction stages,indicating a shift after laying onset.Similar microbiota compositions were observed between proven-triculus and gizzard,as well as between jejunum and ileum,likely due to their anatomical proximity.Lactobacil-lus dominated the upper gut in pullets and the lower gut in older birds.The oesophagus had a high proportion of Proteobacteria,including opportunistic pathogens such as Gallibacterium.Relative abundance of Gallibacterium increased after peak production in multiple gut sections.Aeriscardovia was enriched in the late-lay phase compared to younger birds in multiple gut sections.Age influenced microbial richness and diversity in different organs.The upper gut showed decreased diversity over time,possibly influenced by dietary changes,while the lower gut,specifi-cally cecum and colon,displayed increased richness as birds matured.However,age-related changes were inconsist-ent across all organs,suggesting the influence of organ-specific factors in microbiota maturation.Conclusion Addressing a gap in previous research,this study explored the microbiota across all major gut sections and tracked their dynamics from rearing to the end of the production cycle in commercially raised layer chickens.This study provides a comprehensive understanding of microbiota structure and development which help to develop targeted strategies to optimise gut health and overall productivity in poultry production. 展开更多
关键词 Chicken microbiota Gut microbiota Layers spatial variation temporal variation
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Temporal and Spatial Variation and Distribution Characteristics of Maximum and Minimum Temperature from 1971 to 2008 in Tibet
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作者 格桑 拉巴次仁 陈定梅 《Meteorological and Environmental Research》 CAS 2010年第4期52-55,共4页
Based on temperature data of meteorological stations from 1971 to 2008 in Tibet,the temporal and spatial variation of maximum andminimum temperature in Tibet was analyzed.The results showed that both maximum temperatu... Based on temperature data of meteorological stations from 1971 to 2008 in Tibet,the temporal and spatial variation of maximum andminimum temperature in Tibet was analyzed.The results showed that both maximum temperature andminimum temperature increased distinctly,the warming amplitude of winter was the highest among the four seasons,and next came spring.The increment ofminimum temperature was visibly over that of maximum temperature,particularlyminimum temperature in winter with significant increment.For spatial variation,maximum temperature in most stations increased except particular stations,while theminimum temperature in all stations rose.In addition,the space variation law ofminimum temperature,being more obvious thanminimum temperature,increased from southeast to northwest with different spatial changes in various seasons.From decadal variation,both maximum andminimum temperature appeared increase from 1970s to the first eight years in the 21st century,and the rise ofminimum temperature was significant greater than maximum temperature.The increase of maximum andminimum temperature was the highest from 2001 to 2008,whereas the lowest in 1970s. 展开更多
关键词 Tibet region Maximum andminimum temperature temporal and spatial feature Decadal variation China
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Spatial and temporal variations of water quality in Cao-E River of eastern China 被引量:15
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作者 CHEN Ding-jiang LU Jun +2 位作者 YUAN Shao-feng JIN Shu-quan SHEN Ye-na 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2006年第4期680-688,共9页
Evaluation and analysis of water quality variations were performed with integrated consideration of water quality parameters, hydrological-meteorologic and anthropogenic factors in Cao-E River, Zhejiang Province of Ch... Evaluation and analysis of water quality variations were performed with integrated consideration of water quality parameters, hydrological-meteorologic and anthropogenic factors in Cao-E River, Zhejiang Province of China. Cao-E River system has been polluted and the water quality of some reaches are inferior to Grade V according to National Surface Water Quality Standard of China (GB2002). However, mainly polluted indices of each tributary and mainstream are different. Total nitrogen (TN) and total phosphorus (TP) in the water are the main polluted indices for mainstream that varies from 1.52 to 45.85 mg/L and 0.02 to 4.02 mg/L, respectively. TN is the main polluted indices for Sub-watershed Ⅰ, Ⅱ, Ⅳ and Ⅴ(0.76 to 18.27 mg/L). BOD5 (0.36 to 289.5 mg/L), CODMn (0.47 to 78.86 mg/L), TN (0.74 to 31.09 mg/L) and TP (0 to 3.75 mg/L) are the main polluted indices for Sub-watershed Ⅲ. There are tow pollution types along the river including nonpoint source pollution and point source pollution types. Remarkably temporal variations with a few spatial variations occur in nonpoint pollution type reaches (including mainstream, Sub-watershed Ⅰ and Ⅱ) that mainly drained by arable field and/or dispersive rural dwelling district, and the maximum pollutant concentration appears in flooding seasons. It implied that the runoff increases the pollutant concentration of the water in the nonpoint pollution type reaches. On the other hand, remarkably spatial variations occur in the point pollution type reaches (include Sub-watershed Ⅲ, Ⅳ and Ⅴ) and the maximum pollutant concentration appears in urban reaches. The runoff always decreases the pollutant concentration of the river water in the seriously polluted reaches that drained by industrial point sewage. But for the point pollution reaches resulted from centralized town domestic sewage pipeline and from frequent shipping and digging sands, rainfall always increased the concentration of pollutant (TN) in the river water too. Pollution controls were respectively suggested for these tow types according to different pollution causes. 展开更多
关键词 spatial and temporal variations water quality point pollution nonpoint pollution Cao-E River
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Spatial and temporal variation of nitrogen exported by runoff from sandy agricultural soils 被引量:10
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作者 ZHANG Ming-kui WANG Li-ping HE Zhen-li 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2007年第9期1086-1092,共7页
The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were... The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N (TKN), organic matter-associated N (OM-N), NO3- -N, and NHn+-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3--N, and NHn+-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use. 展开更多
关键词 citrus grove NITROGEN rainfall RUNofF sandy agricultural soils spatial and temporal variation vegetable farms
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Temporal and Spatial Variations in the Climate Controls of Vegetation Dynamics on the Tibetan Plateau during 1982–2011 被引量:5
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作者 Ting HUA Xunming WANG 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2018年第11期1337-1346,共10页
The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region u... The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region under the changing climate.By employing Normalized Difference Vegetation Index data, the Climatic Research Unit temperature and precipitation data,and the in-situ meteorological observations, we report the temporal and spatial variations in the relationships between the vegetation dynamics and climatic factors on the Plateau over the past three decades. The results show that from the early 1980s to the mid-1990s, vegetation dynamics in the central and southeastern part of the Plateau appears to show a closer relationship with precipitation prior to the growing season than that of temperature. From the mid-1990s, the temperature rise seems to be the key climatic factor correlating vegetation growth in this region. The effects of increasing temperature on vegetation are spatially variable across the Plateau: it has negative impacts on vegetation activity in the southwestern and northeastern part of the Plateau, and positive impacts in the central and southeastern Plateau. In the context of global warming, the changing climate condition(increasing precipitation and significant rising temperature) might be the potential contributor to the shift in the climatic controls on vegetation dynamics in the central and southeastern Plateau. 展开更多
关键词 VEGETATION dynamics CLIMATE control temporal and spatial variationS TIBETAN PLATEAU
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Temporal and spatial variations of δ^18O in precipitation of the Yarlung Zangbo River Basin 被引量:7
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作者 LIU Zhongfang TIAN Lide +3 位作者 YAO Tandong GONG Tongliang YIN Changliang YU Wusheng 《Journal of Geographical Sciences》 SCIE CSCD 2007年第3期317-326,共10页
This paper reveals the temporal and spatial variations of stable isotope in precipitation of the Yarlung Zangbo River Basin based on the variations of δ^18O in precipitation at four stations (Lhaze, Nugesha, Yangcu... This paper reveals the temporal and spatial variations of stable isotope in precipitation of the Yarlung Zangbo River Basin based on the variations of δ^18O in precipitation at four stations (Lhaze, Nugesha, Yangcun and Nuxia) in 2005. The results show that δ^18O of precipitation has distinct seasonal changes in the Yarlung Zangbo River Basin. The higher value of δ^18O occurs in spring prior to monsoon precipitation, and the lower value occurs during monsoon precipitation. From the spatial variations, with the altitude-effect and rainout process during moisture transport along the Yarlung Zangbo River Valley, δ^18O of precipitation is gradually depleted. Thus, δ^18O of precipitation decreases gradually from the downstream to the upstream, and the lapse rate of δ^18O in precipitation is approximately 0.34‰/100m and 0.7%J‰/100km for the two reasons. During monsoon precipitation, spatial variation of δ^18O in precipitation is dominated by the amount effect in the large scale synoptic condition. 展开更多
关键词 Yarlung Zangbo River Basin Δ^18O PRECIPITATION temporal and spatial variations
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Spatial and Temporal Variations of Pneumoconiosis in the Pearl River Delta Region in 2006–2015 被引量:5
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作者 LI Xu Dong TU Hong Wei +4 位作者 LIU Yi Ming WEN Xian Zhong YU Hong Wei QU Hong Ying CHEN Qing 《Biomedical and Environmental Sciences》 SCIE CAS CSCD 2020年第3期191-195,共5页
Pneumoconiosis is a restrictive lung disease mostly caused by occupational exposure to dust,including silica dust,asbestos,and other fibers.Inhalable particles smaller than 10μm can enter the bronchioles,injure lung ... Pneumoconiosis is a restrictive lung disease mostly caused by occupational exposure to dust,including silica dust,asbestos,and other fibers.Inhalable particles smaller than 10μm can enter the bronchioles,injure lung cells,and induce lung fibrosis.This hard-to-cure disease places a substantial burden on patients and society[1]. 展开更多
关键词 spatial and temporal variationS of PNEUMOCONIOSIS in the PEARL River DELTA REGION in 2006 DELTA
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Spatial and temporal variations in pH and total alkalinity at the beginning of the rainy season in the Changjiang Estuary, China 被引量:3
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作者 GAO Xuelu SONG Jinming +2 位作者 LI Xuegang YUAN Huamao LI Ning 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2005年第5期68-77,共10页
The results of field observation carried out in May 2003 were used to examine pH and total alkalinity behaviors in the Changjiang Estuary. It was showed that pH and total alkalinity took on clear spatial variations in... The results of field observation carried out in May 2003 were used to examine pH and total alkalinity behaviors in the Changjiang Estuary. It was showed that pH and total alkalinity took on clear spatial variations in values with the minima in the low salinity region. Like salinity, transect distributions of pH and total alkalinity (TA) in a downriver direction had a sharp gradient each. These gradients appeared in such a sequence that the TA gradient was earlier than salinity and pH gradients, and the salinity gradient was earlier than the pH gradient. These distribution characteristics seemed to be strongly influenced by the mixing process of freshwater and seawater, for both pH and total alkalinity had significant linear relationships with salinity and temperature. For pH, phytoplankton activities also had a significant impact upon its spatial distribution. During a period of 48 h, pH and total alkalinity changed within wide ranges for every layer of the two anchor stations, namely, Stas 13 and 20, which were located at the mixed water mass and seawater mass, respectively. For both Stas 13 and 20, pH and TA fluctuation of every layer could be very wide during a 4 h period. As a whole, the data of the two anchor stations showed that neither variations in salinity and temperature nor phytoplankton activities were the main factors strongly influencing the total alkalinity temporal variability on a small time scale. The data of Sta. 20 implied that both salinity variation and phytoplankton activities had a significant influence on pH temporal variability, but the same conclusion could not be drawn from the data of Sta. 13. 展开更多
关键词 Changjiang Estuary PH total alkalinity spatial and temporal variations
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The temporal and spatial variation of positive degree-day factors on the Koxkar Glacier over the south slope of the Tianshan Mountains, China, from 2005 to 2010 被引量:3
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作者 Min Xu HaiDong Han ShiChang Kang 《Research in Cold and Arid Regions》 CSCD 2017年第5期425-431,共7页
The degree-day model is one important method to estimate glacier melt, which is based on the specific relationship between glacial melting and the sum of daily mean temperatures above the melting point. According to t... The degree-day model is one important method to estimate glacier melt, which is based on the specific relationship between glacial melting and the sum of daily mean temperatures above the melting point. According to the observation data on the Koxkar Glacier(KG) from 2005 to 2010, we analyzed the temporal and spatial variation of degree-day factors(DDF) and its influential factors. The results indicate that the average value of DDF was 7.2~10.4 mm/(°C·d) on the KG from 2005 to 2010. It showed a decreasing trend between 3,700 m and 4,200 m, and the deceasing trend was more obvious in the upper part of the KG. On a spatial scale, the DDF increased evidently with increasing altitude. The DDF ranged from3.6 to 9.3 mm/(°C·d) at 3,700 m a.s.l., with the average value of 9.3 mm/(°C·d). It varied from 6.9 to 13.0 mm/(°C·d) at4,000 m a.s.l., with the average value of 10.2 mm/(°C·d). During the period of ablation, the fluctuation of DDF was not significant at the lower altitude(3,700 m a.s.l.), but it decreased at the higher altitudes(4,000 m a.s.l. and 4,200 m a.s.l.).The debris changes the transmission of heat, which accelerates the melting of a glacier; and the DDF showed high value.This paper will provide the reference for temporal–spatial parameterization schemes of DDF on Tuomuer glaciers of the Tianshan Mountains. 展开更多
关键词 DEGREE-DAY factor temporal and spatial variation GLACIER ablation Koxkar GLACIER
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Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait,China 被引量:2
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作者 黄邦钦 林学举 洪华生 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2009年第1期22-30,共9页
The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, ... The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70–209.2)×106 and (0.75–15.4)×106 cells/cm2 in the abundance, and 1.93–52.3 and 1.57–32.4 μgC/cm2 in the carbon biomass, for SYN and PEUK, respectively. The horizontal distributions of both groups were diurnal but heterogeneous in abundance, depending on the groups and layer of depths. Temperature is the key controlling factor for picophytoplankton distribution (especially in winter) in the Strait. 展开更多
关键词 SYNECHOCOCCUS PICOEUKARYOTES PICOPHYTOPLANKTON spatial and temporal variations theTaiwan Strait
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Temporal and Spatial Variation of Phytoplankton Community and Main Pollution Indicators in the Cyanophyte Enrichment Area of North Dianchi Lake 被引量:2
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作者 Yanying Guo Feng He +1 位作者 Aijun Li Yaping Han 《Meteorological and Environmental Research》 CAS 2013年第2期30-33,共4页
[ Objective] The study aimed to discuss the temporal and spatial variation of phytoplankton community and main pollution indicators in cyanophyte enrichment area of northern Dianchi Lake. [ Method ] In the cyanophyte ... [ Objective] The study aimed to discuss the temporal and spatial variation of phytoplankton community and main pollution indicators in cyanophyte enrichment area of northern Dianchi Lake. [ Method ] In the cyanophyte enrichment area of northern Dianchi Lake, phytoplankton community, chlorophyll a, total nitrogen (TN) and total phosphorus (TP) concentration had been monitored monthly from January 2007 to December 2011, and the temporal and spatial variation of phytoplankton community and main pollution indicators were analyzed. [ Result] From January 2007 to December 2011, algal diversity in the area increased slightly, and algal diversity in the alongshore region was less than that in the offshore re- gion ; chlorophyll a, TN and TP concentration decreased in the alongshore region, but it was otherwise in the offshore region; chlorophyll a, TN and TP concentration in the alongshore region were higher than those in the offshore region. [ Conclusion] The research could provide theoretical references for the control of cyanophyte bloom and achievement evaluation of each control measure in Dianchi Lake. 展开更多
关键词 Northern Dianchi PHYTOPLANKTON temporal and spatial variation China
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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 被引量:13
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作者 YANG Xuemei LIU Shizeng +6 位作者 YANG Taibao XU Xianying KANG Caizhou TANG Jinnian WEI Huaidong Mihretab G GHEBREZGABHER LI Zhiqi 《Journal of Arid Land》 SCIE CSCD 2016年第4期556-568,共13页
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 Inv... 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. 展开更多
关键词 desert vegetation NDVI global warming spatial-temporal variations Hexi region
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Temporal and spatial variations of the Huanghe River mouth bars 被引量:1
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作者 YANGZuosheng ZHANGYong +2 位作者 LIUZhan WEIHelong HEShufeng 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2005年第2期43-56,共14页
On the basis of the bathymetric records of 371 survey sections in the present Huanghe mouth area from 1996 to 2001, the temporal and spatial variations of the Huanghe mouth bars were studied by using GIS technology. T... On the basis of the bathymetric records of 371 survey sections in the present Huanghe mouth area from 1996 to 2001, the temporal and spatial variations of the Huanghe mouth bars were studied by using GIS technology. The variation of the mouth bars is closely related to the water and sediment discharges from the Huanghe River to the sea that has been decreasing drastically in recent years, and to coastal hydrodynamic regimes. The characteristics of the mouth bars are unique in contrast with those of other estuaries in the world. (1) The mouth bars of the Huanghe River consist of many small sandbars. Usually the sandbars are of ellipse-shape with the long axis of about 1~6 km, and short axis of about 1~4 km. The long axis is parallel to the principal direction of tidal current, and the short axis is variable, depending on the local dynamics. The crest of the sandbars is only about 0.4 m below the water surface at low tide. They are distributed within an area of 20 km2, not far from the river mouth area. The present mouth bars are in small-medium size, quite different from the large one formed during the 1970s and 1980s, when the river sediment discharge was several times larger than that after 1996. (2) The scale of a river mouth bar is related to the river discharge of that year. In 1997 sediment discharge from the Huanghe River was 42 Mt, and the mouth bar consisted of several small scattered sandbars. In 1998 the size of mouth bars was much larger than that in 1997, as the sediment discharge from the Huanghe River increased to 363 Mt. Variation of the mouth bars largely depends on the sediment discharge with a correlation coefficient of 0.78. The calculation of the volume of the mouth bar area shows that about 30%~40% of the river's into-sea sediment is deposited in the mouth bar area. (3) Compared with other large estuaries in the world, the Huanghe mouth bars have three unique features in responding to its high sediment concentration: small size, steep slope gradient and shallow crest depth. 展开更多
关键词 Huanghe mouth bars temporal and spatial variations mechanism of formation
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Spatial and temporal variation of energy carbon emissions in Yantai from 2001 to 2011 被引量:1
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作者 Qiuhong Su Qiuxian Wang +1 位作者 Dengjie Wang Xiaomei Yan 《Chinese Journal of Population,Resources and Environment》 2016年第3期182-188,共7页
In order to understand the characteristics of spatial and temporal variation,as well as provide effective ideas on carbon emissions and regulatory policy in Yantai,this article analyzed spatial and temporal variation ... In order to understand the characteristics of spatial and temporal variation,as well as provide effective ideas on carbon emissions and regulatory policy in Yantai,this article analyzed spatial and temporal variation of carbon emissions in Yantai based on energy consumption statistics for a variety of energy sorts together with industrial sectors from 2001 to 2011.The results were as following:First of all,Yantai's carbon emissions grew by an average of 5.5%per year during the last 10 years,and there was a peak of 10.48 million carbon in the year of 2011.Second,compared with the gross domestic product(GDP) growth rate,the figures for energy carbon emissions growth rate were smaller;however the problem of carbon emissions were still more obvious.Furthermore,carbon emissions in Yantai increased rapidly before 2008;while after 2008,it increased more slowly and gradually become stable.Third,the energy consumption was different among regions in Yantai.For instance,the energy consumption in Longkou city was the largest,which occupied 50%of the total carbon emissions in Yantai;and the energy consumption in Chang Island was generally less than 1%of the Longkou consumption.Finally,there were relative close relationships among the spatial difference of carbon emissions,regional resources endowment,economic development,industrial structure,and energy efficiency. 展开更多
关键词 Energy carbon emission spatial and temporal variation energy consumption carbon emission intensity
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The Spatial and Temporal Variation Characteristics of CH<sub>4</sub>and CO<sub>2</sub>Emission Flux under Different Land Use Types in the Yellow River Delta Wetland 被引量:1
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作者 Qingfeng Chen Junjian Ma +1 位作者 Changsheng Zhao Rongbin Li 《Journal of Geoscience and Environment Protection》 2015年第6期26-32,共7页
The Yellow River Delta Wetland is one of the youngest wetlands, and also the most complete, extensive wetlands in China. The wetland in this delta is ecologically important due to their hydrologic attributes and their... The Yellow River Delta Wetland is one of the youngest wetlands, and also the most complete, extensive wetlands in China. The wetland in this delta is ecologically important due to their hydrologic attributes and their roles as ecotones between terrestrial and aquatic ecosystems. In the study, the spatial and temporal variation characteristics of CH4 and CO2 emission flux under five kinds of land use types in the wetland were investigated. The results indicated that the greenhouse gas emission flux, especially the CO2 and CH4, showed distinctly spatial and temporal variation under different land use types in the wetland. In the spring, the emission flux of CO2 was higher than that of CO2 in the autumn, and appeared negative in HW3 and HW4 in the autumn. CH4 emission flux of HW4 and HW5 was negative in the spring and autumn, which indicated that the CH4 emission process was net absorption. Among the five kinds of land use types, the CO2 emission flux of HW4 discharged the largest emission flux reaching 29.3 mg.m-2.h-1, but the CH4 emission flux of HW2 discharged the largest emission flux reaching 0.15 mg.m-2.h-1. From the estuary to the inland, the emission flux of CO2 was decreased at first and then appeared increasing trend, but the emission flux of CH4 was contrary to CO2. 展开更多
关键词 WETLand CH4 and CO2 Emission FLUX Land Use spatial and temporal variation
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Temporal and spatial variation characteristics of extreme precipitation on the Loess Plateau of China facing the precipitation process 被引量:1
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作者 ZHANG Yixin LI Peng +5 位作者 XU Guoce MIN Zhiqiang LI Qingshun LI Zhanbin WANG Bin CHEN Yiting 《Journal of Arid Land》 SCIE CSCD 2023年第4期439-459,共21页
The preceding and succeeding precipitation(PSP)often act together with extreme precipitation(EP),in turn,causing floods,which is an objective component that is often overlooked with regard to summer flood hazards in t... The preceding and succeeding precipitation(PSP)often act together with extreme precipitation(EP),in turn,causing floods,which is an objective component that is often overlooked with regard to summer flood hazards in the arid region of Northwest China.In this study,event-based extreme precipitation(EEP)was defined as continuous precipitation that includes at least one day of EP.We analyzed the spatiotemporal variation characteristics of four EEP types(front EEP,late EEP,balanced EEP,and single day EEP)across the Loess Plateau(LP)based on data acquired from 87 meteorological stations from 1960 to 2019.Precipitation on the LP basically maintained a spatial pattern of"low in the northwest region and high in the southeast region",and EP over the last 10 a increased significantly.The cumulative precipitation percentage of single day EEP was 34%and was dominant for 60 a,while the cumulative precipitation percentage of front,late,and balanced EEP types associated with PSP accounted for 66%,which confirms to the connotation of EEP.The cumulative frequencies of front and late EEP types were 23%and 21%,respectively,while the cumulative frequency of balanced EEP had the lowest value at only 13%.Moreover,global warming could lead to more single day EEP across the LP,and continuous EEP could increase in the northwestern region and decrease in the eastern region in the future.The concept of process-oriented EP could facilitate further exploration of disaster-causing processes associated with different types of EP,and provide a theoretical basis for deriving precipitation disaster chains and construction of disaster cluster characteristics. 展开更多
关键词 temporal and spatial variation climate change extreme precipitation(EP) event-based extreme precipitation(EEP) Loess Plateau
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Analysis on temporal and spatial variations of groundwater hydrochemical characteristics in the past decade in southern plain of Beijing, China 被引量:1
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作者 JIANG Ti-sheng QU Ci-xiao +3 位作者 WANG Ming-yu SUN Yan-wei HU Bo CHU Jun-yao 《Journal of Groundwater Science and Engineering》 2017年第3期235-248,共14页
Groundwater utilization and protection are crucial for sustainable urban development. This is especially true for Beijing, where groundwater is an important source for urban water supply. In this study, statistical me... Groundwater utilization and protection are crucial for sustainable urban development. This is especially true for Beijing, where groundwater is an important source for urban water supply. In this study, statistical methods, including descriptive statistics, correlation analysis, principal component analysis, and Piper-Tri-linear diagram, were used in analyzing the temporal and spatial variations of the hydrochemical characteristics of groundwater based on monitored data from the southern plain of Beijing, China. Results indicated consistent changes of groundwater's hydrochemical characteristics in different aquifers in the study area. The percentage of HCO_3^-in total anion increased significantly in the groundwater, and hydrochemical water type evolved gradually from Ca-Mg-Cl-SO_4 based to Ca-Mg-HCO_3 based from period 2005-2007 to period 2013-2015. In shallow groundwater, the concentration of Na^+, Ca^(2+), SO_4^(2-), HCO_3^-, and total dissolved solids(TDS) increased from period 2005-2007 to period 2013-2015, and the greatest change came from HCO_3^-, rising from 428.93 to 528.96 mgL^(-1). The changes of main ionic concentrations in the deep groundwater were consistent with those in the shallow groundwater for both periods. However, the variations in deep groundwater were less than those in shallow groundwater. The temporal and spatial variations of hydrochemical characteristics reflect the groundwater quality in the study area. This study could facilitate decision-making process on the protection of groundwater resources to ensure its sustainable utilization. 展开更多
关键词 BEIJING GROUNDWATER Hydrochemical characteristics temporal and spatial variation Water quality
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Analysis on Temporal and Spatial Variation Characteristics of the Precipitation in Hexi Corridor in Recent 58 Years 被引量:1
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作者 LI Xiang-yu ZHOU Xiang 《Meteorological and Environmental Research》 2012年第1期36-40,共5页
[ Objective] The research aimed to analyze temporal and spatial variation characteristics of the precipitation in Hexi Corridor in the past 58 years. [Method] Based on monthly rainfall data in Hexi Corridor from 1951 ... [ Objective] The research aimed to analyze temporal and spatial variation characteristics of the precipitation in Hexi Corridor in the past 58 years. [Method] Based on monthly rainfall data in Hexi Corridor from 1951 to 2008, by using moving average, wavelet analysis and climate trend coefficient, variation rule of the precipitation in Hexi Corridor in the past 58 years was analyzed. [ Result] Average rainfall in Hexi Corridor in the past 58 years was 130.4 mm. Precipitation mainly concentrated in summer, occupying 59.08% of the annual rainfall. From June to September, it occupied 72.57% of the annual precipitation. Interdecadal change of the precipitation in Hexi Corridor wasn't severe. Average rainfall in each dec- ade was from 120.8 to 139.0 mm. The precipitation series had periods of the 5, 10, 21 and 32 years in Hexi Corridor from 1951 to 2008. in the fu- ture, annual, spring, summer and winter precipitation would have small increase tendency. Increase amplitude of the annual precipitation in Shule River basin was the biggest (5.231 -0.062 mm/10 a). The increase amplitude in the south and southeast of the Heihe River basin was bigger than that in the northwest. The smallest increase amplitude of the annual precipitation was 3.280 -0.098 mm/10 a in Shiyang River basin. [ Conclusion] This research could provide beneficial reference for coordinated development between local social economy and ecological environment. 展开更多
关键词 PRECIPITATION temporal and spatial variation Trend analysis Hexi Corridor China
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