Air pollution is one of the top environmental concerns and causes of deaths and variousdiseases worldwide. In this paper, PM2.5 observation data at 1,497 automatic air quality-monitoringstations in 367 cities of China...Air pollution is one of the top environmental concerns and causes of deaths and variousdiseases worldwide. In this paper, PM2.5 observation data at 1,497 automatic air quality-monitoringstations in 367 cities of China in 2015 were utilized, and the study on spatiotemporal distribution of PM2.5concentration found that the average annual concentration of PM2.5 in urban China in 2015 was 49.74 μg/m3and exceeded the annual average limit in 287 cities. PM2.5 concentrations were highest in winter and lowestin summer in most cities, but it reached the highest in spring in the cities around Taklimakan Desert. Therewere 320 fi ne days in 2015 and the maximum PM2.5 was prone to appear at night, the minimum was usuallyin the afternoon, but in the early morning in Lhasa, and the minimum in winter was even in the earlymorning, midday and afternoon in some cities. Higher concentrations of PM2.5 were found in the EastChina Plain and the cities around Taklimakan Desert, preceded by the Yangtze River Delta economic zone,Chengdu-Chongqing economic zone and Harbin-Changchun megalopolis, while the lower values coveredthe northwestern region of Xinjiang, Heilongjiang Xing’an Mountains region, northeast high latitudes ofInner Mongolia, southwest high altitudes in the border area of Sichuan, Yunnan, Qinghai-Tibet Plateau andthe southeast coastal areas.展开更多
The China-Myanmar Economic Corridor(CMEC) is an important part of China's Belt and Road Initiative and an important area for global ecology and biodiversity. In this study, the annual and seasonal spatiotemporal p...The China-Myanmar Economic Corridor(CMEC) is an important part of China's Belt and Road Initiative and an important area for global ecology and biodiversity. In this study, the annual and seasonal spatiotemporal patterns of temperature and precipitation in the CMEC over the past century were investigated using linear tendency estimation, the Mann-Kendall mutation test, the T-test, and wavelet analysis based on the monthly mean climatic data from 1901 to 2018 released by the Climatic Research Unit(CRU) of the University of East Anglia, UK. The results show that the CMEC demonstrated a trend of warming and drying over the past 100 years, and the rate of change in Myanmar was stronger than that in Yunnan Province of China. The warming rate was 0.039 ℃/10a. Precipitation decreased at a rate of -6.1 mm/10a. From the perspective of spatial distribution, temperature was high in the central and southern, low in the north of the CMEC, and the high-temperature centers were mainly distributed in the southern plain and river valley. Precipitation decreased from west to east and from south to north of the CMEC. From the perspective of the rate of change, warming was stronger in central and northern CMEC than in southern and northeastern CMEC. The rate of precipitation decline was stronger in the central and western regions than in the eastern region. This study provides a scientific reference for the CMEC to address climate change and ensure sustainable social and economic development and ecological security.展开更多
Acquiring spatiotemporal patterns of phenological information and its drivers is essential for understanding the response of crops to climate change and implementing adaptation measures.However,current approaches to o...Acquiring spatiotemporal patterns of phenological information and its drivers is essential for understanding the response of crops to climate change and implementing adaptation measures.However,current approaches to obtain phenology and analyse its drivers have deficiencies such as sparse observations,excessive dependence of remote sensing inversion on sensors,and inevitable difficulties in upscaling site-based crop models into larger regions.Based on the Wang-Engel temperature response function,we improved the Crop Estimation through Resource and Environment Synthesis-Wheat(CERES-Wheat)model.First,we calibrated the model at the regional scale and evaluated its performance.Furthermore,the spatiotemporal changes in winter wheat phenology in China from 2000 to 2015 were analysed.The results showed that the improved model significantly enhanced the simulation accuracy of the anthesis and maturity dates by averages of 13%and 12%in most planting areas,especially in the Yunnan-Guizhou Plateau(YG)with improvements of 26%and 28%.The simulated phenology of winter wheat grown in a colder environment(e.g.,the average temperatures during the vegetative growth period range from 0 to 5℃ and from 15 to 20°C,and the reproductive growth period ranges from 10 to 15°C)also notably improved.These results confirmed that the original temperature response function indeed had limitations.Further analyses revealed that the key phenological dates and growth periods over the past 16 years were dominantly advanced and shortened.Specifically,the anthesis date,vegetative growth period(VGP),and reproductive growth period(RGP)indicated obviously spatial characteristics.For example,the anthesis date and VGP in the North China Plain(NCP)and the Middle-Lower Yangtze Plain(YZ)and the RGP in northwestern China(NW)showed opposite trends of delay and prolongation as comparing with the dominant patterns.Sensitivity analysis indicated that the key phenological dates and growth periods were advanced and shortened as the minimum(T_(min))and maximum temperatures(T_(max))rose,while they were postponed and prolonged with the increased precipitation.However,their responses to solar radiation did not show spatial consistency.Additionally,we found that the sensitivity of phenology to climatic factors differed across subregions.In particular,phenology in southwestern China and YG was more sensitive to T_(min),T_(max),and solar radiation than in the NCP and NW.Moreover,the sensitivity to precipitation in NW was higher than that in YZ.Totally,the improved crop model could provide more refined spatial characteristics of phenology at a large scale and benefit to explore its drivers more objectively.Furthermore,our results highlight that different planting areas should adopt suitable adaptation measures to cope with climate change impacts.Ultimately,the improved model is promising to enhance the accuracy of yield prediction and provide powerful tools for assessing regional climate change impact and adaptability.展开更多
A long-term,consistent Fraction of Absorbed Photosynthetically Active Radiation(FPAR)product is necessary to study the spatial and temporal patterns of vegetation dynamics associated with climatic changes and human a...A long-term,consistent Fraction of Absorbed Photosynthetically Active Radiation(FPAR)product is necessary to study the spatial and temporal patterns of vegetation dynamics associated with climatic changes and human activities.In this study,Eurasia was selected as the study area.The relationship between FPAR and simple infrared/red ratio relationship(SR FPAR),and that between Moderate Resolution Imaging Spectroradiometer(MODIS)FPAR and a Normalised Difference Vegetation Index(NDVI)look-up table(LUT FPAR)were employed to estimate FPAR from 1982 to 2006 by different land cover types,focusing on the comparisons of spatiotemporal FPAR patterns between the two FPAR datasets.The results showed high agreement between MODIS standard FPAR and estimated FPAR in seasonal dynamics with peak values in July.The LUT FPAR was close to MODIS standard FPAR and larger than SR FPAR.The SR and LUT FPAR showed the same spatial distribution and inter-annual variation patterns and were primarily determined by land cover types.An overall increasing trend in FPAR was observed from 1982 to 2006,with reductions from 1991 to 1994 and 2000 to 2002.The inter-annual dynamics in evergreen broadleaf forests showed a decreasing trend over 25 years,while non-forest vegetation FPAR values had slow,stable growth in inter-annual variation.展开更多
Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipita...Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipitation in north-west China is unclear.The dendrochronological method was used to study climate response sensitivity of radial growth of Picea schrenkiana from 158 trees at six sites during 1990-2020.The results show that climate warming and increased precipitation significantly promoted the growth of trees.The response to temperature first increased,then decreased.However,the response to increased precipitation and the self-calibrating Palmer Drought Severity Index(scPDSI)increased significantly.In most areas of the Tianshan Mountains,the proportion of trees under increased precipitation and scPDSI positive response was relatively high.Over time,small-diameter trees were strongly affected by drought stress.It is predicted that under continuous warming and increased precipitation,trees in most areas of the Tianshan Mountains,especially those with small diameters,will be more affected by precipitation.展开更多
Cultivated land pressure represents a direct reflection of grain security. Existing relevant studies rarely approached the spatiotemporal pattern of cultivated land pressure or the spatial heterogeneity of its influen...Cultivated land pressure represents a direct reflection of grain security. Existing relevant studies rarely approached the spatiotemporal pattern of cultivated land pressure or the spatial heterogeneity of its influencing factors from the level of economic zones.Taking the Huaihai Economic Zone(HEZ), China for case analysis, this study investigated the spatiotemporal pattern of cultivated land pressure in diverse periods from 2000 to 2018 based on a modified cultivated land pressure index and spatial correlation models. On this basis, it explored the influencing factors of the spatial differentiation of cultivated land pressure in the late stage of the study using geographical detector as well as multi-scale geographically weighted regression model. The results indicated that: 1) in the study period, the global cultivated land pressure index of the study area decreased gradually, but cultivated land pressure increased locally in a significant way, especially in the central and southern Shandong Province;2) the spatial pattern of cultivated land pressure manifested global clustering features. Hot and secondary-hot spots presented a narrowing and clustering trend, whereas cold and secondary-cold spots manifested a spreading and clustering trend;3) average slope, the proportion of non-grain crops, population urbanization rate, and multiple cropping index have significant effects on the spatial differentiation of cultivated land pressure. The former three factors were positively correlated with cultivated land pressure, and the last factor was negatively correlated with cultivated land pressure;and 4) the amount of cultivated land has increased in the central and southern Shandong Province through land consolidation which, nonetheless, failed to improve the grain production. In regards to major grain producing areas similar to the HEZ in China, the authors suggest that great importance should be given to the balance of the quality and quantity of cultivated land, the optimization of agricultural production factors and the rational control of non-grain crops, thus providing a powerful guarantee for grain security in China.展开更多
The composition of animal species and interactions among them are widely known to shape ecological communities and fine-scale(e.g.,<1 km)monitoring of animal communities is essential for understanding the relations...The composition of animal species and interactions among them are widely known to shape ecological communities and fine-scale(e.g.,<1 km)monitoring of animal communities is essential for understanding the relationships among animals and plants.Although the co-existence of large-and medium-sized species has been studied across different scales,research on fine-scale interactions of herbivores in deciduous broadleaf forests is limited.Camera trapping of large-and medium-sized mammals was carried out over a 1 year period within a 25 ha deciduous broadleaf forest dynamics plot in the Qinling Mountains,China.Fourteen species of large-and medium-sized mammals,including six carnivores,six ungulates,one primate and one rodent species were found.Kernel density estimations were used to analyse the diel or 24 h activity patterns of all species with more than 40 independent detections and general linear models were developed to explore the spatial relationships among the species.The combination of overlapping diel activity patterns and spatial associations showed obvious niche separation among six species:giant panda(Ailuropoda melanoleuca David),takin(Budorcas taxicolor Hodgson),Reeves’s muntjac(Muntiacus reevesi Ogilby),tufted deer(Elaphodus cephalophus Milne-Edwards),Chinese serow(Capricornis milneedwardsii David)and wild boar(Sus scrofa Linnaeus).Long-term fine-scale monitoring is useful for providing information about the co-existence of species and their interactions.The results demonstrate the importance for fine-scale monitoring of animals and plants for improving understanding of species interactions and community dynamics.展开更多
The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and...The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and complexity.Recently,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods.However,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics.To this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state.After matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion.The applicability and effectiveness of the proposed approach are examined in a road network of Beijing,China.Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.展开更多
Social assistance is the last safety net in the social security system and plays a vital role in poverty alleviation in countries around the world. Promoting the equal financial assistance is meaningful to achieve equ...Social assistance is the last safety net in the social security system and plays a vital role in poverty alleviation in countries around the world. Promoting the equal financial assistance is meaningful to achieve equalization of social assistance. Based on the provincial panel data from 2002 to 2017, this paper analyzes the dynamic characteristics and main influencing factors of the equity of social assistance in China, using the Theil index and geographically weighted regression(GWR) model. The results suggest that the level of per capita social assistance expenditure(PSAE) in China keeps increasing year by year, but the changes in different regions and provinces are quite different. These changes not only significantly changed the spatial pattern of PSAE in China, but also greatly improved its spatial coupling with the deeply impoverished areas. Further analysis shows that the regional inequality of PSAE between provinces is obvious during the study period, and the inter-regional inequality is significantly higher than the intra-regional inequality.This makes inter-regional inequality become the main source of the regional inequality of PSAE in China for a long time. According to GWR results, there is obvious spatiotemporal heterogeneity in the influence intensity and direction of the per capita financial revenue,urbanization rate, urban unemployment rate, natural disaster-affected area, and transfer payment intensity on the PSAE. The urbanization rate and per capita financial revenue are the main driving factors of PSAE, and the impact intensity of per capita financial revenue tends to strengthen. The remaining three factors have a positive effect on PSAE, but the effect intensity is not high.展开更多
Regional ecological health,the core of comprehensive ecosystem assessments,is an important foundation for regional exploration,environmental conservation,and sustainable development.The mountainous areas in southwest ...Regional ecological health,the core of comprehensive ecosystem assessments,is an important foundation for regional exploration,environmental conservation,and sustainable development.The mountainous areas in southwest China are backward in economy,but industrialization and urbanization have been rapid in recent years.This study assessed the ecosystem health of the Sichuan and Yunnan provinces in China using a pressure-state-response(PSR)model.Spatiotemporal patterns of regional ecosystem health were analyzed from 2000 to 2016,including overall characteristics as well as local characteristics.Ecosystem health in most regions was improved over time(Y=0.0058 X–11.0132,R2=0.95,P<0.001),and areas with poorer ecosystem health decreased from half to one-third of the total area.Analysis of the primacy ratio and the variation coefficient confirmed that the gap in health scores between regions has gradually expanded since 2007,but there are more high quality regions overall(Z of Moran’s index<1.96,P>0.05).Overall,the regional ecosystems to the east of the Hu line-an imaginary line dividing east and west China into roughly equivalent parts-were healthier than those to the west.The pressure and state scores of ecosystems were determined by physiographic condition,and the response scores by government policies and social concern.The spatiotemporal patterns of ecosystem health were dominated to a greater extent by natural than anthropogenic factors,which explains why the shift in the patterns aligned with the direction of the Hu line.Dividing regions into key management areas based on natural geographical conditions and socioeconomic development could contribute to the formulation of a reasonable ecological and environmental protection policy,guaranteeing ecosystem services in the long run.展开更多
China has experienced rapid urbanizations with dramatic land cover changes since 1978. Forest loss is one of land cover changes, and it induces various eco-environmental degradation issues. As one of China’s hotspot ...China has experienced rapid urbanizations with dramatic land cover changes since 1978. Forest loss is one of land cover changes, and it induces various eco-environmental degradation issues. As one of China’s hotspot regions, the Guangdong-Hong KongMacao Greater Bay Area(GBA) has undergone a dramatic urban expansion. To better understand forest dynamics and protect forest ecosystem, revealing the processes, patterns and underlying drivers of forest loss is essential. This study focused on the spatiotemporal evolution and potential driving factors of forest loss in the GBA at regional and city level. The Landsat time-series images from 1987 to2017 were used to derive forest, and landscape metrics and geographic information system(GIS) were applied to implement further spatial analysis. The results showed that: 1) 14.86% of the total urban growth area of the GBA was obtained from the forest loss in1987–2017;meanwhile, the forest loss area of the GBA reached 4040.6 km2, of which 25.60%(1034.42 km2) was converted to urban land;2) the percentages of forest loss to urban land in Dongguan(19.14%), Guangzhou(18.35%) and Shenzhen(15.81%) were higher than those in other cities;3) the forest became increasingly fragmented from 1987–2007, and then the fragmentation decreased from2007 to 2017);4) the landscape responses to forest changes varied with the scale;and 5) some forest loss to urban regions moved from low-elevation and gentle-slope terrains to higher-elevation and steep-slope terrains over time, especially in Shenzhen and Hong Kong.Urbanization and industrialization greatly drove forest loss and fragmentation, and, notably, hillside urban land expansion may have contributed to hillside forest loss. The findings will help policy makers in maintaining the stability of forest ecosystems, and provide some new insights into forest management and conservation.展开更多
Accurate estimations of evapotranspiration(ET)are essential for understanding land-atmosphere coupling and atmosphere-underlying surface energy and water vapor exchanges.Based on input data processing,this paper simul...Accurate estimations of evapotranspiration(ET)are essential for understanding land-atmosphere coupling and atmosphere-underlying surface energy and water vapor exchanges.Based on input data processing,this paper simulates the temporal and spatial variation of ET in the Dajiuhu Basin from 1990 to 2018 using the BEPS-Terrain Lab V2.0 model.Compared with the ET measured by an eddy covariance(EC)tower,the model explained 80.1%of the ET variation.From 1990 to 2018,the average annual ET in the Dajiuhu Basin was 1262.7 mm/yr indicating a downward trend(–27.12 mm/yr).In 2005,a sudden change point was observed based on the Mann-Kendall(MK)test and 3-year moving t-test.Around 2005,the downward trend in ET slowed and the proportional trend of ET to precipitation changed from upward trend to downward trend.Regarding spatial distribution,the ET in the basin’s central part was smaller than that in the basin’s surrounding area,the ET of the southern slope was higher than that of the northern slope,and the decrease in the ET rate on the sunny side was lower than that on the shady side.ET decreased as the elevation increased,with the fastest decrease observed between 2184 and 2384 m.For different landcover types,the average ET exhibited the following order:deciduous forest>mixed forest>wetland>grass>agriculture land.Decreased solar radiation is the main reason for the decreased ET in the Dajiuhu Basin,followed by increased wind speed and relative humidity,which together contribute 83.9%to the ET trend.This paper provides a theoretical basis for the study of ET changes and the mechanism of ET and provides a decision-making reference for water resource management in the Dajiuhu Basin and even the South-to-North Water Transfer Project.展开更多
Nutrient levels in the artificial channel constructed for the Middle Route Project are significant indicators of water quality safety and aquatic ecological integrity for this large,interbasin scheme.However,the distr...Nutrient levels in the artificial channel constructed for the Middle Route Project are significant indicators of water quality safety and aquatic ecological integrity for this large,interbasin scheme.However,the distribution and transport of nutrients along the channel were poorly understood.Based on a time-series dataset as well as mass balance and material flow analysis methods,the water and nutrient transport fluxes in the Middle Route of the South-to-North Water Diversion Project were identified in this study.The results indicate that the nutrient concentrations varied considerably with time,but there was no significant difference among the 30 stations of the main channel.Seasonal temperature difference was the major factor in the large fluctuations of water quality indicators over time.The nutrient loadings varied with the water volume outputs from the main channel to the waterreceiving cities.Atmospheric deposition was an important source of nutrients in the main channel,accounting for 9.13%,20.6%,and 0.635%of the nitrogen,phosphorus,and sulfur input from the Danjiangkou Reservoir,respectively.In 2021,a net accumulation of 988 tons of N,29 tons of P,and 2,540 tons of S,respectively,were present in the main channel.The increase of these external and internal nutrient loadings would cause water quality fluctuation and deterioration in some local sections of the main channel.Our study quantified the spatial and temporal patterns of nutrient transport in the Middle Route and revealed the ecological effects on the aquatic environment,assisting authorities on the project to develop effective water conservation strategies.展开更多
Climate change resulting from CO_2 emissions has become an important global environmental issue in recent years.Improving carbon emission performance is one way to reduce carbon emissions.Although carbon emission perf...Climate change resulting from CO_2 emissions has become an important global environmental issue in recent years.Improving carbon emission performance is one way to reduce carbon emissions.Although carbon emission performance has been discussed at the national and industrial levels,city-level studies are lacking due to the limited availability of statistics on energy consumption.In this study,based on city-level remote sensing data on carbon emissions in China from 1992–2013,we used the slacks-based measure of super-efficiency to evaluate urban carbon emission performance.The traditional Markov probability transfer matrix and spatial Markov probability transfer matrix were constructed to explore the spatiotemporal evolution of urban carbon emission performance in China for the first time and predict long-term trends in carbon emission performance.The results show that urban carbon emission performance in China steadily increased during the study period with some fluctuations.However,the overall level of carbon emission performance remains low,indicating great potential for improvements in energy conservation and emission reduction.The spatial pattern of urban carbon emission performance in China can be described as"high in the south and low in the north,"and significant differences in carbon emission performance were found between cities.The spatial Markov probabilistic transfer matrix results indicate that the transfer of carbon emission performance in Chinese cities is stable,resulting in a"club convergence"phenomenon.Furthermore,neighborhood backgrounds play an important role in the transfer between carbon emission performance types.Based on the prediction of long-term trends in carbon emission performance,carbon emission performance is expected to improve gradually over time.Therefore,China should continue to strengthen research and development aimed at improving urban carbon emission performance and achieving the national energy conservation and emission reduction goals.Meanwhile,neighboring cities with different neighborhood backgrounds should pursue cooperative economic strategies that balance economic growth,energy conservation,and emission reductions to realize low-carbon construction and sustainable development.展开更多
A mathematical model,consisting of a system of two coupled reaction-diffusion partial differential equations describing the interaction between solid tumor and immune system(termed as effector cells),is proposed here....A mathematical model,consisting of a system of two coupled reaction-diffusion partial differential equations describing the interaction between solid tumor and immune system(termed as effector cells),is proposed here.The main focus is on the analysis of the spa-tiotemporal dynamics of tumor cells and immune cells.The resulting systerm is analyzed and numerical simulations are presented.Diferent types of spatial patterns with respect to different initial conditions,and time are observed.Their analysis and mechanism of spatiotemporal pattern formation in immunogenic tumor are studied.Spatiotemporal perturbation around non-spatial steady state beyond the linear regime is obtained based on the analysis of higher-order perturbation terms.展开更多
Based on remote sensing and Geographic Information System techniques,multi-temporal Landsat data were used to monitor land use/cover changes(LUCC)in the Nanchang area during 1989–2010.Quantitative and spatiotemporal ...Based on remote sensing and Geographic Information System techniques,multi-temporal Landsat data were used to monitor land use/cover changes(LUCC)in the Nanchang area during 1989–2010.Quantitative and spatiotemporal indicators derived from the transition matrix for overall changes,intensity analysis for inter-category transitions,and spatiotemporal analysis of intra-category variations were constructed to analyze the spatiotemporal LUCC evolution.The study results show that urban and industrial land rapidly and continually expanded.The spatial extent of rural settlements shrunk while their distribution density increased.Cultivated land showed a tendency of spatially continuous loss and fragmented distribution,whereas the spatial pattern of forest tended to concentrate.The extents of ponds and reservoirs remained stable,but spatial changes were obvious.Rivers and bottomlands decreased significantly and tended toward fragmentation.The overall LUCC pattern showed that construction land rapidly sprawled while cultivated land decreased substantially,indicating an acceler-ating stage of urbanization and industrialization.Although rigid land requirements for urbanization had to be satisfied,land development and consolidation across forests and water body areas,as well as adjustment of agricultural structure,laid the foundation for a transition toward intensive land use in the Nanchang area.展开更多
Background:Dengue fever(DF)is a common mosquito-borne viral infectious disease in the world,and increasingly severe DF epidemics in China have seriously affeaed people's health in recent years.Thus,investigating s...Background:Dengue fever(DF)is a common mosquito-borne viral infectious disease in the world,and increasingly severe DF epidemics in China have seriously affeaed people's health in recent years.Thus,investigating spatiotemporal patterns and potential influencing factors of DF epidemics in typical regions is critical to consolidate effective prevention and control measures for these regional epidemics.Methods:A generalized additive model(GAM)was used to identify potential contributing faaors that influence spatiotemporal epidemic patterns in typical DF epidemic regions of China(e.g.,the Pearl River Delta[PRD]and the Border of Yunnan and Myanmar[BYM]).In terms of influencing faaors,environmental factors including the normalized difference vegetation index(NDVI),temperature,precipitation,and humidity,in conjunaion with socioeconomic factors,such as population density(Pop),road density,land-use,and gross domestic product,were employed.Results:DF epidemics in the PRD and BYM exhibit prominent spatial variations at 4 km and 3 km grid scales,characterized by significant spatial clustering over the Guangzhou-Foshan,Dehong,and Xishuangbanna areas.The GAM that integrated the Pop-urban land ratio(ULR)-NDVI-humidity-temperature factors for the PRD and the ULR-Road density-NDVI-temperaturewater land ratio-precipitation faaors for the BYM performed well in terms of overall accuracy,with Akaike Information Criterion values of 61859.89 and 826.65,explaining a total variance of 83.4 and 97.3〇/〇,respectively.As indicated,socioeconomic factors have a stronger influence on DF epidemics than environmental faaors in the study area.Among these faaors,Pop(PRD)and ULR(BYM)were the socioeconomic faaors explaining the largest variance in regional epidemics,whereas NDVI was the environmental faaor explaining the largest variance in both regions.In addition,the common factors(ULR,NDVI,and temperature)in these two regions exhibited different effeas on regional epidemics.Conclusions:The spatiotemporal patterns of DF in the PRD and BYM are influenced by environmental and socioeconomic factors,the socioeconomic faaors may play a significant role in DF epidemics in cases where environmental factors are suitable and differ only slightly throughout an area.Thus,prevention and control resources should be fully allocated by referring to the spatial patterns of primary influencing faaors to better consolidate the prevention and control measures for DF epidemics.展开更多
This paper proposes a novel data indexing scheme,the distributed access pattern R-tree(DAPR-tree),for spatial data retrieval in a distributed computing environment.As compared to traditional distributed indexing schem...This paper proposes a novel data indexing scheme,the distributed access pattern R-tree(DAPR-tree),for spatial data retrieval in a distributed computing environment.As compared to traditional distributed indexing schemes,the DAPR-tree introduces the data access patterns during the indexing utilization stage so that a more balanced indexing structure can be provided for spatial applications(e.g.Digital Earth data warehouse).In this new indexing scheme,(a)an indexing penalty matrix is proposed by considering the balance of data number,topology and access load between different indexing nodes;(b)an‘access possibility’element is integrated to a classic‘Master-Client’structure for a distributed indexing environment;and(c)indexing algorithm for the DAPR-tree is provided for index implementations.By using a duplication of official GEOSS Clearinghouse system as a case study,the DAPR-tree was evaluated in a number of scenarios.The results show that our indexing schemes generally outperform(around 9%)traditional distributed indices with the utilization of data access patterns.Finally,we discuss the applicability of the DARP-tree and document DARP-tree shortcomings to encourage researchers pursuing related topics in Big Data indexing for Digital Earth and other geospatial initiatives.展开更多
Introduction:The spatial association dynamics of free-ranging cattle herds are not fully understood;however,they can have a direct influence on the spatial patterns of resource utilization.The aim of our study was to ...Introduction:The spatial association dynamics of free-ranging cattle herds are not fully understood;however,they can have a direct influence on the spatial patterns of resource utilization.The aim of our study was to examine new analytical methods of identifying the spatio-temporal patterns of behavioral dynamics that determine cattle herd dispersal in the semi-arid rangelands of South Texas.We fitted 10 free-ranging cows with global positioning system collars and obtained positions every 5 min for each animal for 21-day trials,twice during the summer and winter period.We used an association pattern recognition software(ASSOC1)and the herd center of gravity to identify the spatial and temporal thresholds that defined dispersion-aggregation patterns and individual position to determine their relation to social dominance.Results:The association pattern defining herd membership was that animals spent 70%of their time within 200 m of each other.Dominance ranking did not appear to influence association membership or position within the herd.The cattle showed a more dispersed distribution during summer,but in winter,herd members behaved in a more aggregated pattern.This distribution is contrary to patterns described in more northerly and mountainous regions.Conclusions:The spatial thresholds of the cattle herd and the overall distance of all members to the center of the herd were smaller during winter and larger during summer,indicating that this study herd congregated during the winter and dispersed during the summer.Although this study uses a herd of 10 individuals in a 100 ha pasture to evaluate spatio-temporal dynamics,our results provide evidence of the ability of current tracking and spatial association tools to detect and quantify seasonal changes in cattle herd dispersion-aggregation patterns.The use of these data collection and analysis methods could prove useful in larger cattle herds,increase our understanding of herd spatiotemporal behavior,and subsequently help in the development of improved management practices.展开更多
China has experienced rapid and massive urban expansion in recent decades.To address the opportunities and challenges posed by urbanization,it is important to investigate this process.Although many studies have charac...China has experienced rapid and massive urban expansion in recent decades.To address the opportunities and challenges posed by urbanization,it is important to investigate this process.Although many studies have characterized China’s urbanization,mainly based on individual cities or urban agglomerations,few studies have compared the urban expansion patterns among cities of different regions and sizes at a national scale.Additionally,the source of the newly developed urban land has largely been ignored in previous research.To fill these gaps,we provide a comprehensive view of the growth patterns of 291 Chinese cities during 1990–2015,quantifying the rates,spatial forms,and corresponding landscape characteristics of the urban expansion.More importantly,we further investigate what their new urban land is converted from.Key findings include:(1)the annual expansion(AE)and annual growth rate(AGR)of all 291 cities were 1869.81 km2 and 4.81%during 1990–2015;(2)cropland and rural settlements were the predominant source,accounting for 65.22%and 17.49%of the new urban land during 1990–2015;(3)edge-expansion was the dominant growth form for most cities,followed by infilling and leapfrogging growth;and(4)the landscape characteristics of the occupied cropland differed across various cities.展开更多
基金Supported by Guizhou Province Science and Technology Fund(LKT[2012]07,25).
文摘Air pollution is one of the top environmental concerns and causes of deaths and variousdiseases worldwide. In this paper, PM2.5 observation data at 1,497 automatic air quality-monitoringstations in 367 cities of China in 2015 were utilized, and the study on spatiotemporal distribution of PM2.5concentration found that the average annual concentration of PM2.5 in urban China in 2015 was 49.74 μg/m3and exceeded the annual average limit in 287 cities. PM2.5 concentrations were highest in winter and lowestin summer in most cities, but it reached the highest in spring in the cities around Taklimakan Desert. Therewere 320 fi ne days in 2015 and the maximum PM2.5 was prone to appear at night, the minimum was usuallyin the afternoon, but in the early morning in Lhasa, and the minimum in winter was even in the earlymorning, midday and afternoon in some cities. Higher concentrations of PM2.5 were found in the EastChina Plain and the cities around Taklimakan Desert, preceded by the Yangtze River Delta economic zone,Chengdu-Chongqing economic zone and Harbin-Changchun megalopolis, while the lower values coveredthe northwestern region of Xinjiang, Heilongjiang Xing’an Mountains region, northeast high latitudes ofInner Mongolia, southwest high altitudes in the border area of Sichuan, Yunnan, Qinghai-Tibet Plateau andthe southeast coastal areas.
基金funded by the Natural Science Foundation of China (Grant No. 42271030)Fujian Provincial Funds for Distinguished Young Scientists (Grant No. 2022J06018)Applied Basic Research Programs of Yunnan province (Grant No. 202001BB050073)。
文摘The China-Myanmar Economic Corridor(CMEC) is an important part of China's Belt and Road Initiative and an important area for global ecology and biodiversity. In this study, the annual and seasonal spatiotemporal patterns of temperature and precipitation in the CMEC over the past century were investigated using linear tendency estimation, the Mann-Kendall mutation test, the T-test, and wavelet analysis based on the monthly mean climatic data from 1901 to 2018 released by the Climatic Research Unit(CRU) of the University of East Anglia, UK. The results show that the CMEC demonstrated a trend of warming and drying over the past 100 years, and the rate of change in Myanmar was stronger than that in Yunnan Province of China. The warming rate was 0.039 ℃/10a. Precipitation decreased at a rate of -6.1 mm/10a. From the perspective of spatial distribution, temperature was high in the central and southern, low in the north of the CMEC, and the high-temperature centers were mainly distributed in the southern plain and river valley. Precipitation decreased from west to east and from south to north of the CMEC. From the perspective of the rate of change, warming was stronger in central and northern CMEC than in southern and northeastern CMEC. The rate of precipitation decline was stronger in the central and western regions than in the eastern region. This study provides a scientific reference for the CMEC to address climate change and ensure sustainable social and economic development and ecological security.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41977405,42061144003).
文摘Acquiring spatiotemporal patterns of phenological information and its drivers is essential for understanding the response of crops to climate change and implementing adaptation measures.However,current approaches to obtain phenology and analyse its drivers have deficiencies such as sparse observations,excessive dependence of remote sensing inversion on sensors,and inevitable difficulties in upscaling site-based crop models into larger regions.Based on the Wang-Engel temperature response function,we improved the Crop Estimation through Resource and Environment Synthesis-Wheat(CERES-Wheat)model.First,we calibrated the model at the regional scale and evaluated its performance.Furthermore,the spatiotemporal changes in winter wheat phenology in China from 2000 to 2015 were analysed.The results showed that the improved model significantly enhanced the simulation accuracy of the anthesis and maturity dates by averages of 13%and 12%in most planting areas,especially in the Yunnan-Guizhou Plateau(YG)with improvements of 26%and 28%.The simulated phenology of winter wheat grown in a colder environment(e.g.,the average temperatures during the vegetative growth period range from 0 to 5℃ and from 15 to 20°C,and the reproductive growth period ranges from 10 to 15°C)also notably improved.These results confirmed that the original temperature response function indeed had limitations.Further analyses revealed that the key phenological dates and growth periods over the past 16 years were dominantly advanced and shortened.Specifically,the anthesis date,vegetative growth period(VGP),and reproductive growth period(RGP)indicated obviously spatial characteristics.For example,the anthesis date and VGP in the North China Plain(NCP)and the Middle-Lower Yangtze Plain(YZ)and the RGP in northwestern China(NW)showed opposite trends of delay and prolongation as comparing with the dominant patterns.Sensitivity analysis indicated that the key phenological dates and growth periods were advanced and shortened as the minimum(T_(min))and maximum temperatures(T_(max))rose,while they were postponed and prolonged with the increased precipitation.However,their responses to solar radiation did not show spatial consistency.Additionally,we found that the sensitivity of phenology to climatic factors differed across subregions.In particular,phenology in southwestern China and YG was more sensitive to T_(min),T_(max),and solar radiation than in the NCP and NW.Moreover,the sensitivity to precipitation in NW was higher than that in YZ.Totally,the improved crop model could provide more refined spatial characteristics of phenology at a large scale and benefit to explore its drivers more objectively.Furthermore,our results highlight that different planting areas should adopt suitable adaptation measures to cope with climate change impacts.Ultimately,the improved model is promising to enhance the accuracy of yield prediction and provide powerful tools for assessing regional climate change impact and adaptability.
基金the National Basic Research Program of China(contract:2009CB723902)Key Project of Digital Earth Science Platform CEODE(contract:Y01002101A)National Natural Science Foundation of China(contract:40801127).
文摘A long-term,consistent Fraction of Absorbed Photosynthetically Active Radiation(FPAR)product is necessary to study the spatial and temporal patterns of vegetation dynamics associated with climatic changes and human activities.In this study,Eurasia was selected as the study area.The relationship between FPAR and simple infrared/red ratio relationship(SR FPAR),and that between Moderate Resolution Imaging Spectroradiometer(MODIS)FPAR and a Normalised Difference Vegetation Index(NDVI)look-up table(LUT FPAR)were employed to estimate FPAR from 1982 to 2006 by different land cover types,focusing on the comparisons of spatiotemporal FPAR patterns between the two FPAR datasets.The results showed high agreement between MODIS standard FPAR and estimated FPAR in seasonal dynamics with peak values in July.The LUT FPAR was close to MODIS standard FPAR and larger than SR FPAR.The SR and LUT FPAR showed the same spatial distribution and inter-annual variation patterns and were primarily determined by land cover types.An overall increasing trend in FPAR was observed from 1982 to 2006,with reductions from 1991 to 1994 and 2000 to 2002.The inter-annual dynamics in evergreen broadleaf forests showed a decreasing trend over 25 years,while non-forest vegetation FPAR values had slow,stable growth in inter-annual variation.
基金funded by the National Natural Science Foundation of China(No.31971460 and 32271646)the National Key Research and Development Program of China(2021YFD2200401)。
文摘Climate change significantly impacts forest ecosystems in arid and semi-arid regions.However,spatiotemporal patterns of climate-sensitive changes in individual tree growth under increased climate warming and precipitation in north-west China is unclear.The dendrochronological method was used to study climate response sensitivity of radial growth of Picea schrenkiana from 158 trees at six sites during 1990-2020.The results show that climate warming and increased precipitation significantly promoted the growth of trees.The response to temperature first increased,then decreased.However,the response to increased precipitation and the self-calibrating Palmer Drought Severity Index(scPDSI)increased significantly.In most areas of the Tianshan Mountains,the proportion of trees under increased precipitation and scPDSI positive response was relatively high.Over time,small-diameter trees were strongly affected by drought stress.It is predicted that under continuous warming and increased precipitation,trees in most areas of the Tianshan Mountains,especially those with small diameters,will be more affected by precipitation.
基金Under the auspices of National Natural Science Foundation of China (No.42071229,41671174)Priority Academic Program Development of Jiangsu Higher Education Institutions (No.164320H116)。
文摘Cultivated land pressure represents a direct reflection of grain security. Existing relevant studies rarely approached the spatiotemporal pattern of cultivated land pressure or the spatial heterogeneity of its influencing factors from the level of economic zones.Taking the Huaihai Economic Zone(HEZ), China for case analysis, this study investigated the spatiotemporal pattern of cultivated land pressure in diverse periods from 2000 to 2018 based on a modified cultivated land pressure index and spatial correlation models. On this basis, it explored the influencing factors of the spatial differentiation of cultivated land pressure in the late stage of the study using geographical detector as well as multi-scale geographically weighted regression model. The results indicated that: 1) in the study period, the global cultivated land pressure index of the study area decreased gradually, but cultivated land pressure increased locally in a significant way, especially in the central and southern Shandong Province;2) the spatial pattern of cultivated land pressure manifested global clustering features. Hot and secondary-hot spots presented a narrowing and clustering trend, whereas cold and secondary-cold spots manifested a spreading and clustering trend;3) average slope, the proportion of non-grain crops, population urbanization rate, and multiple cropping index have significant effects on the spatial differentiation of cultivated land pressure. The former three factors were positively correlated with cultivated land pressure, and the last factor was negatively correlated with cultivated land pressure;and 4) the amount of cultivated land has increased in the central and southern Shandong Province through land consolidation which, nonetheless, failed to improve the grain production. In regards to major grain producing areas similar to the HEZ in China, the authors suggest that great importance should be given to the balance of the quality and quantity of cultivated land, the optimization of agricultural production factors and the rational control of non-grain crops, thus providing a powerful guarantee for grain security in China.
基金This work was supported by the National Natural Science Foundation of China project(No 41671183).
文摘The composition of animal species and interactions among them are widely known to shape ecological communities and fine-scale(e.g.,<1 km)monitoring of animal communities is essential for understanding the relationships among animals and plants.Although the co-existence of large-and medium-sized species has been studied across different scales,research on fine-scale interactions of herbivores in deciduous broadleaf forests is limited.Camera trapping of large-and medium-sized mammals was carried out over a 1 year period within a 25 ha deciduous broadleaf forest dynamics plot in the Qinling Mountains,China.Fourteen species of large-and medium-sized mammals,including six carnivores,six ungulates,one primate and one rodent species were found.Kernel density estimations were used to analyse the diel or 24 h activity patterns of all species with more than 40 independent detections and general linear models were developed to explore the spatial relationships among the species.The combination of overlapping diel activity patterns and spatial associations showed obvious niche separation among six species:giant panda(Ailuropoda melanoleuca David),takin(Budorcas taxicolor Hodgson),Reeves’s muntjac(Muntiacus reevesi Ogilby),tufted deer(Elaphodus cephalophus Milne-Edwards),Chinese serow(Capricornis milneedwardsii David)and wild boar(Sus scrofa Linnaeus).Long-term fine-scale monitoring is useful for providing information about the co-existence of species and their interactions.The results demonstrate the importance for fine-scale monitoring of animals and plants for improving understanding of species interactions and community dynamics.
基金the National Natural Science Foundation of China(U1564212,61773036,51508014)Beijing Natural Science Foundation(9172011)Young Elite Scientist Sponsorship Program of the China Association for Science and Technology(2016QNRC001)。
文摘The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and complexity.Recently,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods.However,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics.To this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state.After matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion.The applicability and effectiveness of the proposed approach are examined in a road network of Beijing,China.Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.
基金Under the auspices of National Social Science Fund of China(No.18BJL126)。
文摘Social assistance is the last safety net in the social security system and plays a vital role in poverty alleviation in countries around the world. Promoting the equal financial assistance is meaningful to achieve equalization of social assistance. Based on the provincial panel data from 2002 to 2017, this paper analyzes the dynamic characteristics and main influencing factors of the equity of social assistance in China, using the Theil index and geographically weighted regression(GWR) model. The results suggest that the level of per capita social assistance expenditure(PSAE) in China keeps increasing year by year, but the changes in different regions and provinces are quite different. These changes not only significantly changed the spatial pattern of PSAE in China, but also greatly improved its spatial coupling with the deeply impoverished areas. Further analysis shows that the regional inequality of PSAE between provinces is obvious during the study period, and the inter-regional inequality is significantly higher than the intra-regional inequality.This makes inter-regional inequality become the main source of the regional inequality of PSAE in China for a long time. According to GWR results, there is obvious spatiotemporal heterogeneity in the influence intensity and direction of the per capita financial revenue,urbanization rate, urban unemployment rate, natural disaster-affected area, and transfer payment intensity on the PSAE. The urbanization rate and per capita financial revenue are the main driving factors of PSAE, and the impact intensity of per capita financial revenue tends to strengthen. The remaining three factors have a positive effect on PSAE, but the effect intensity is not high.
基金Under the auspices of Science and Technology Service Network Initiative(No.KFJ-STS-QYZD-060)Key Project of National Natural Science Foundation of China(No.41930651)
文摘Regional ecological health,the core of comprehensive ecosystem assessments,is an important foundation for regional exploration,environmental conservation,and sustainable development.The mountainous areas in southwest China are backward in economy,but industrialization and urbanization have been rapid in recent years.This study assessed the ecosystem health of the Sichuan and Yunnan provinces in China using a pressure-state-response(PSR)model.Spatiotemporal patterns of regional ecosystem health were analyzed from 2000 to 2016,including overall characteristics as well as local characteristics.Ecosystem health in most regions was improved over time(Y=0.0058 X–11.0132,R2=0.95,P<0.001),and areas with poorer ecosystem health decreased from half to one-third of the total area.Analysis of the primacy ratio and the variation coefficient confirmed that the gap in health scores between regions has gradually expanded since 2007,but there are more high quality regions overall(Z of Moran’s index<1.96,P>0.05).Overall,the regional ecosystems to the east of the Hu line-an imaginary line dividing east and west China into roughly equivalent parts-were healthier than those to the west.The pressure and state scores of ecosystems were determined by physiographic condition,and the response scores by government policies and social concern.The spatiotemporal patterns of ecosystem health were dominated to a greater extent by natural than anthropogenic factors,which explains why the shift in the patterns aligned with the direction of the Hu line.Dividing regions into key management areas based on natural geographical conditions and socioeconomic development could contribute to the formulation of a reasonable ecological and environmental protection policy,guaranteeing ecosystem services in the long run.
基金Under the auspices of National Natural Science Foundation of China(No.41890854)Basic Research Program of Shenzhen Science and Technology Innovation Committee(No.JCYJ20180507182022554)+3 种基金National Key R&D Program of China(No.2017YFC0506200)National Natural Science Foundation of China(No.7181101150)National Natural Science Foundation of China(No.41901248)Shenzhen Future Industry Development Funding Program(No.201507211219247860)。
文摘China has experienced rapid urbanizations with dramatic land cover changes since 1978. Forest loss is one of land cover changes, and it induces various eco-environmental degradation issues. As one of China’s hotspot regions, the Guangdong-Hong KongMacao Greater Bay Area(GBA) has undergone a dramatic urban expansion. To better understand forest dynamics and protect forest ecosystem, revealing the processes, patterns and underlying drivers of forest loss is essential. This study focused on the spatiotemporal evolution and potential driving factors of forest loss in the GBA at regional and city level. The Landsat time-series images from 1987 to2017 were used to derive forest, and landscape metrics and geographic information system(GIS) were applied to implement further spatial analysis. The results showed that: 1) 14.86% of the total urban growth area of the GBA was obtained from the forest loss in1987–2017;meanwhile, the forest loss area of the GBA reached 4040.6 km2, of which 25.60%(1034.42 km2) was converted to urban land;2) the percentages of forest loss to urban land in Dongguan(19.14%), Guangzhou(18.35%) and Shenzhen(15.81%) were higher than those in other cities;3) the forest became increasingly fragmented from 1987–2007, and then the fragmentation decreased from2007 to 2017);4) the landscape responses to forest changes varied with the scale;and 5) some forest loss to urban regions moved from low-elevation and gentle-slope terrains to higher-elevation and steep-slope terrains over time, especially in Shenzhen and Hong Kong.Urbanization and industrialization greatly drove forest loss and fragmentation, and, notably, hillside urban land expansion may have contributed to hillside forest loss. The findings will help policy makers in maintaining the stability of forest ecosystems, and provide some new insights into forest management and conservation.
基金Under the auspices of National Natural Science Foundation of China(No.41201429)Independent Research Funds of the State Key Laboratory of Biogeology and Environmental Geology(No.GKZ17Y651)Fundamental Research Funds of Geological Processes,Resources and Environment in the Yangtze Basin(No.CUGCJ1808)。
文摘Accurate estimations of evapotranspiration(ET)are essential for understanding land-atmosphere coupling and atmosphere-underlying surface energy and water vapor exchanges.Based on input data processing,this paper simulates the temporal and spatial variation of ET in the Dajiuhu Basin from 1990 to 2018 using the BEPS-Terrain Lab V2.0 model.Compared with the ET measured by an eddy covariance(EC)tower,the model explained 80.1%of the ET variation.From 1990 to 2018,the average annual ET in the Dajiuhu Basin was 1262.7 mm/yr indicating a downward trend(–27.12 mm/yr).In 2005,a sudden change point was observed based on the Mann-Kendall(MK)test and 3-year moving t-test.Around 2005,the downward trend in ET slowed and the proportional trend of ET to precipitation changed from upward trend to downward trend.Regarding spatial distribution,the ET in the basin’s central part was smaller than that in the basin’s surrounding area,the ET of the southern slope was higher than that of the northern slope,and the decrease in the ET rate on the sunny side was lower than that on the shady side.ET decreased as the elevation increased,with the fastest decrease observed between 2184 and 2384 m.For different landcover types,the average ET exhibited the following order:deciduous forest>mixed forest>wetland>grass>agriculture land.Decreased solar radiation is the main reason for the decreased ET in the Dajiuhu Basin,followed by increased wind speed and relative humidity,which together contribute 83.9%to the ET trend.This paper provides a theoretical basis for the study of ET changes and the mechanism of ET and provides a decision-making reference for water resource management in the Dajiuhu Basin and even the South-to-North Water Transfer Project.
基金supported by the National Natural Science Foundation of China (Nos.52270202,and 41877471)the special fund was from the State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences,Chinese Academy of Sciences) (No.21Z02ESPCR)。
文摘Nutrient levels in the artificial channel constructed for the Middle Route Project are significant indicators of water quality safety and aquatic ecological integrity for this large,interbasin scheme.However,the distribution and transport of nutrients along the channel were poorly understood.Based on a time-series dataset as well as mass balance and material flow analysis methods,the water and nutrient transport fluxes in the Middle Route of the South-to-North Water Diversion Project were identified in this study.The results indicate that the nutrient concentrations varied considerably with time,but there was no significant difference among the 30 stations of the main channel.Seasonal temperature difference was the major factor in the large fluctuations of water quality indicators over time.The nutrient loadings varied with the water volume outputs from the main channel to the waterreceiving cities.Atmospheric deposition was an important source of nutrients in the main channel,accounting for 9.13%,20.6%,and 0.635%of the nitrogen,phosphorus,and sulfur input from the Danjiangkou Reservoir,respectively.In 2021,a net accumulation of 988 tons of N,29 tons of P,and 2,540 tons of S,respectively,were present in the main channel.The increase of these external and internal nutrient loadings would cause water quality fluctuation and deterioration in some local sections of the main channel.Our study quantified the spatial and temporal patterns of nutrient transport in the Middle Route and revealed the ecological effects on the aquatic environment,assisting authorities on the project to develop effective water conservation strategies.
基金Fundamental Research Funds for the Central UniversitiesNo.19lgzd09+2 种基金Guangdong Special Support ProgramPearl River S&T Nova Program of GuangzhouNo.201806010187
文摘Climate change resulting from CO_2 emissions has become an important global environmental issue in recent years.Improving carbon emission performance is one way to reduce carbon emissions.Although carbon emission performance has been discussed at the national and industrial levels,city-level studies are lacking due to the limited availability of statistics on energy consumption.In this study,based on city-level remote sensing data on carbon emissions in China from 1992–2013,we used the slacks-based measure of super-efficiency to evaluate urban carbon emission performance.The traditional Markov probability transfer matrix and spatial Markov probability transfer matrix were constructed to explore the spatiotemporal evolution of urban carbon emission performance in China for the first time and predict long-term trends in carbon emission performance.The results show that urban carbon emission performance in China steadily increased during the study period with some fluctuations.However,the overall level of carbon emission performance remains low,indicating great potential for improvements in energy conservation and emission reduction.The spatial pattern of urban carbon emission performance in China can be described as"high in the south and low in the north,"and significant differences in carbon emission performance were found between cities.The spatial Markov probabilistic transfer matrix results indicate that the transfer of carbon emission performance in Chinese cities is stable,resulting in a"club convergence"phenomenon.Furthermore,neighborhood backgrounds play an important role in the transfer between carbon emission performance types.Based on the prediction of long-term trends in carbon emission performance,carbon emission performance is expected to improve gradually over time.Therefore,China should continue to strengthen research and development aimed at improving urban carbon emission performance and achieving the national energy conservation and emission reduction goals.Meanwhile,neighboring cities with different neighborhood backgrounds should pursue cooperative economic strategies that balance economic growth,energy conservation,and emission reductions to realize low-carbon construction and sustainable development.
基金The first author gratefully acknowledges the financial support given by the Ministryof Human Resource and Development (MHRD), Government of India, India。
文摘A mathematical model,consisting of a system of two coupled reaction-diffusion partial differential equations describing the interaction between solid tumor and immune system(termed as effector cells),is proposed here.The main focus is on the analysis of the spa-tiotemporal dynamics of tumor cells and immune cells.The resulting systerm is analyzed and numerical simulations are presented.Diferent types of spatial patterns with respect to different initial conditions,and time are observed.Their analysis and mechanism of spatiotemporal pattern formation in immunogenic tumor are studied.Spatiotemporal perturbation around non-spatial steady state beyond the linear regime is obtained based on the analysis of higher-order perturbation terms.
基金This work was supported by the Ministry of Science and Technology,China,National Research Program[2010CB530300,2012AA12A407,2012CB955501,2013AA122003]the National Natural Science Foundation of China[41271099].
文摘Based on remote sensing and Geographic Information System techniques,multi-temporal Landsat data were used to monitor land use/cover changes(LUCC)in the Nanchang area during 1989–2010.Quantitative and spatiotemporal indicators derived from the transition matrix for overall changes,intensity analysis for inter-category transitions,and spatiotemporal analysis of intra-category variations were constructed to analyze the spatiotemporal LUCC evolution.The study results show that urban and industrial land rapidly and continually expanded.The spatial extent of rural settlements shrunk while their distribution density increased.Cultivated land showed a tendency of spatially continuous loss and fragmented distribution,whereas the spatial pattern of forest tended to concentrate.The extents of ponds and reservoirs remained stable,but spatial changes were obvious.Rivers and bottomlands decreased significantly and tended toward fragmentation.The overall LUCC pattern showed that construction land rapidly sprawled while cultivated land decreased substantially,indicating an acceler-ating stage of urbanization and industrialization.Although rigid land requirements for urbanization had to be satisfied,land development and consolidation across forests and water body areas,as well as adjustment of agricultural structure,laid the foundation for a transition toward intensive land use in the Nanchang area.
文摘Background:Dengue fever(DF)is a common mosquito-borne viral infectious disease in the world,and increasingly severe DF epidemics in China have seriously affeaed people's health in recent years.Thus,investigating spatiotemporal patterns and potential influencing factors of DF epidemics in typical regions is critical to consolidate effective prevention and control measures for these regional epidemics.Methods:A generalized additive model(GAM)was used to identify potential contributing faaors that influence spatiotemporal epidemic patterns in typical DF epidemic regions of China(e.g.,the Pearl River Delta[PRD]and the Border of Yunnan and Myanmar[BYM]).In terms of influencing faaors,environmental factors including the normalized difference vegetation index(NDVI),temperature,precipitation,and humidity,in conjunaion with socioeconomic factors,such as population density(Pop),road density,land-use,and gross domestic product,were employed.Results:DF epidemics in the PRD and BYM exhibit prominent spatial variations at 4 km and 3 km grid scales,characterized by significant spatial clustering over the Guangzhou-Foshan,Dehong,and Xishuangbanna areas.The GAM that integrated the Pop-urban land ratio(ULR)-NDVI-humidity-temperature factors for the PRD and the ULR-Road density-NDVI-temperaturewater land ratio-precipitation faaors for the BYM performed well in terms of overall accuracy,with Akaike Information Criterion values of 61859.89 and 826.65,explaining a total variance of 83.4 and 97.3〇/〇,respectively.As indicated,socioeconomic factors have a stronger influence on DF epidemics than environmental faaors in the study area.Among these faaors,Pop(PRD)and ULR(BYM)were the socioeconomic faaors explaining the largest variance in regional epidemics,whereas NDVI was the environmental faaor explaining the largest variance in both regions.In addition,the common factors(ULR,NDVI,and temperature)in these two regions exhibited different effeas on regional epidemics.Conclusions:The spatiotemporal patterns of DF in the PRD and BYM are influenced by environmental and socioeconomic factors,the socioeconomic faaors may play a significant role in DF epidemics in cases where environmental factors are suitable and differ only slightly throughout an area.Thus,prevention and control resources should be fully allocated by referring to the spatial patterns of primary influencing faaors to better consolidate the prevention and control measures for DF epidemics.
基金funded by the National Key R&D Program of China[grant number 2018YFB2100704]Science,Technology and Innovation Commission of Shenzhen Municipality[grant numbers JCYJ20170412142239369,JCYJ20170818101704025]the National Natural Science Foundation of China[grant numbers 41701444,71961137003,41971341].
文摘This paper proposes a novel data indexing scheme,the distributed access pattern R-tree(DAPR-tree),for spatial data retrieval in a distributed computing environment.As compared to traditional distributed indexing schemes,the DAPR-tree introduces the data access patterns during the indexing utilization stage so that a more balanced indexing structure can be provided for spatial applications(e.g.Digital Earth data warehouse).In this new indexing scheme,(a)an indexing penalty matrix is proposed by considering the balance of data number,topology and access load between different indexing nodes;(b)an‘access possibility’element is integrated to a classic‘Master-Client’structure for a distributed indexing environment;and(c)indexing algorithm for the DAPR-tree is provided for index implementations.By using a duplication of official GEOSS Clearinghouse system as a case study,the DAPR-tree was evaluated in a number of scenarios.The results show that our indexing schemes generally outperform(around 9%)traditional distributed indices with the utilization of data access patterns.Finally,we discuss the applicability of the DARP-tree and document DARP-tree shortcomings to encourage researchers pursuing related topics in Big Data indexing for Digital Earth and other geospatial initiatives.
基金Funding to C.Cheleuitte-Nieves was provided through Hispanic Leaders in Agriculture and the Environment(HLAE)fellowships,the Alfred P.Sloan Foundation Minority PhD fellowship,Texas A&M University Graduate Diversity fellowship,and Department of Ecosystem and Management(Texas A&M University)Tom Slick fellowship.
文摘Introduction:The spatial association dynamics of free-ranging cattle herds are not fully understood;however,they can have a direct influence on the spatial patterns of resource utilization.The aim of our study was to examine new analytical methods of identifying the spatio-temporal patterns of behavioral dynamics that determine cattle herd dispersal in the semi-arid rangelands of South Texas.We fitted 10 free-ranging cows with global positioning system collars and obtained positions every 5 min for each animal for 21-day trials,twice during the summer and winter period.We used an association pattern recognition software(ASSOC1)and the herd center of gravity to identify the spatial and temporal thresholds that defined dispersion-aggregation patterns and individual position to determine their relation to social dominance.Results:The association pattern defining herd membership was that animals spent 70%of their time within 200 m of each other.Dominance ranking did not appear to influence association membership or position within the herd.The cattle showed a more dispersed distribution during summer,but in winter,herd members behaved in a more aggregated pattern.This distribution is contrary to patterns described in more northerly and mountainous regions.Conclusions:The spatial thresholds of the cattle herd and the overall distance of all members to the center of the herd were smaller during winter and larger during summer,indicating that this study herd congregated during the winter and dispersed during the summer.Although this study uses a herd of 10 individuals in a 100 ha pasture to evaluate spatio-temporal dynamics,our results provide evidence of the ability of current tracking and spatial association tools to detect and quantify seasonal changes in cattle herd dispersion-aggregation patterns.The use of these data collection and analysis methods could prove useful in larger cattle herds,increase our understanding of herd spatiotemporal behavior,and subsequently help in the development of improved management practices.
基金supported by the National Natural Science Foundation of China:[grant number 41522110 and 41771360]the Hubei Provincial Natural Science Foundation of China:[grant number 2017CFA029]the National Key Research and Development Program of China:[grant number 2016YFB0501403].
文摘China has experienced rapid and massive urban expansion in recent decades.To address the opportunities and challenges posed by urbanization,it is important to investigate this process.Although many studies have characterized China’s urbanization,mainly based on individual cities or urban agglomerations,few studies have compared the urban expansion patterns among cities of different regions and sizes at a national scale.Additionally,the source of the newly developed urban land has largely been ignored in previous research.To fill these gaps,we provide a comprehensive view of the growth patterns of 291 Chinese cities during 1990–2015,quantifying the rates,spatial forms,and corresponding landscape characteristics of the urban expansion.More importantly,we further investigate what their new urban land is converted from.Key findings include:(1)the annual expansion(AE)and annual growth rate(AGR)of all 291 cities were 1869.81 km2 and 4.81%during 1990–2015;(2)cropland and rural settlements were the predominant source,accounting for 65.22%and 17.49%of the new urban land during 1990–2015;(3)edge-expansion was the dominant growth form for most cities,followed by infilling and leapfrogging growth;and(4)the landscape characteristics of the occupied cropland differed across various cities.
