Analysis Of Spatio-temporal Changes Research Articles

The Origin of Eight Trigrams: Explaining the Mechanism of Soil Response to Temperature Change

The Eight Trigrams has held a high position in the Eastern culture, but its origin of has been a mystery for thousands of years, thus it has not yet entered the scientific system. This research reveals the possible origin of the Eight Trigrams and the purpose of drawing the hexagrams. Research has shown that due to changes in the solar radiation there exist annual and diurnal soil temperature variable zones (STVZs). The heat conducts and interactions between the double-layer also form two different statuses of warming and cooling. In this paper the hydrometeorological factors such as temperature, relative humidity, absolute humidity and earth-air pressure were monitored or calculated in the STVZs. If the anural/diurnal STVZ is divided into three levels, and we associate soil cooling processes (Yin) with “--” and warming processes (Yang) with “—”. It is not hard to find that the distribution of soil status in soil profile at different times and locations clearly reflects the soil response to temperature change and reveals movement mechanism of earth-air and water. Furthermore, this model can be seen to be the source of the Eight Trigrams in the Yi-jing. The double-layer structure of the soil constitutes the foundation of the double trigrams. The Yin and Yang processes both form the primary driving force for phreatic water moves upward. Fu Xi invented the method of hou-qi, in which the monitoring of earth-air pressure in the closed system and applying Yin-Yang to draw Eight Trigrams and analysis of spatiotemporal status changes in the soil, which was then used to enact a calendar used as a guide to time for farming usage. The Yin-Yang and Eight Trigrams perfectly explain the response of earth-air to solar terms and mechanisms of water vertical cycle on daily/yearly timescales.

Analysis of spatiotemporal changes of agricultural land after the Second World War in Czechia

The term Sudetenland refers to large regions of the former Czechoslovakia that had been dominated by Germans. German population was expelled directly after the Second World War, between 1945 and 1947. Almost three million people left large areas in less than two years. This population change led to a break in the relationship between the people and the landscape. The aim of the study is to compare the trajectories of these changes in agricultural landscapes in lower and higher altitudes, both in depopulated areas and areas with preserved populations. This study included ten sites in the region of Northern Bohemia in Czechia (18,000 ha in total). Five of these sites represent depopulated areas, and the other five areas where populations remained preserved. Changes in the landscape were assessed through a bi-temporal analysis of land use change by using aerial photograph data from time hoirzons of 2018 and 1953. Land use changes from the 1950s to the present are corroborated in the studied depopulated and preserved areas mainly by the trajectory of agricultural land to forest. The results prove that both population displacement and landscape type are important factors that affect landscape changes, especially in agricultural landscapes.

Analysis of spatio-temporal changes of land cover and landscape pattern in Guangdong-Hong Kong-Macao Greater Bay Area

Analysis of spatio-temporal changes of land cover and landscape pattern in Guangdong-Hong Kong-Macao Greater Bay Area

Analysis of Spatiotemporal Changes and Driving Factors of Desertification in the Africa Sahel

Analysis of Spatiotemporal Changes and Driving Factors of Desertification in the Africa Sahel

A Model-Based Analysis of Spatio-Temporal Changes of the Urban Expansion in Arid Area of Western China: A Case Study in North Xinjiang Economic Zone

Investigation of urban expansion can provide a better understanding of the urbanization process and its driving forces, which is critical for environmental management and land use planning. Total of 514 sampling points from the aerial photos and field sampling were applied to assess the image accuracy. A Conversion of Land Use and its Effect at Small Region Extent (CLUE-S) model was established to simulate the urbanization process at the township level in the North Xinjiang Economic Zone (NXEZ) of western China. Historical land use and land cover changes with multi-temporal remote sensing data were retrieved, and the underlying driving forces were explored by training the CLUE-S model. Moreover, future changes in urban development were simulated under different scenarios. Results showed that the overall accuracy reaches larger than 80% for the years of 2002, 2005, and 2007, and the corresponding kappa coefficient is bigger than 0.8. The NXEZ is at a premature development stage compared with urban clusters in eastern China. Before 1999, the driving force in this region was primary industry development. In recent years, secondary industries started to show significance in urbanization. These findings indicate that the industrial base and economic development in the NXEZ are still relatively weak and have not taken a strong leading role. When industry and population become the main driving factors, the regional economy will enter a new stage of leap-forward development, which in turn will stimulate a new round of rapid urbanization.

Vegetation- and Environmental Changes on Non-Reclaimed Spoil Heaps in Southern Poland.

The study focused on the changes in vegetation and soils on an undeveloped area of coal mine spoil heaps. The process of vegetation changes was evaluated on the basis of historical cartographic materials and fieldwork. Changes of vegetation in nearly 200 years are presented herein. The main purpose of this study is to present an analysis of spatio-temporal changes in vegetation and their influence on soil features. The diversity of ecological species in terms of habitat requirements, tendency of hornbeam communities formation, and the relationship between forest communities and soil features was found. The basic soil properties were examined under selected plant communities (pH, Corg, Nt), available forms of elements (P, K, Mg), and as plant nutrients and heavy metal occurrence (Fe, Zn, Mn, Co, Cd, Pb, Sr, Cr, Cu). The soil organic carbon (Corg) content varied from 3.17 ± 0.007% to 17.7 ± 0.21% and significant differences were observed between sites. The highest total nitrogen (Nt) content was recorded in the soils of the sites that were represented by Populus-Betula stands (0.60 ± 0.01%). Soil acidity (pH) varied greatly, ranging from acidic (pH = 4.1) to weakly acidic (pH = 5.9). The highest value for Mgavail (205.43 ± 0.5 mg·kg−1) was noted in the soils under Calamagrostis epegijos (L.) Roth community and for Pavail (184.07 ± 3.77) and Kavail (346.19 ± 2.92 mg·kg−1) under the Quercus-Pinus stand. On all sites, Zn was a dominant element and its concentration ranged from 526.1 to 1060.4 mg·kg−1. Obtained results show how important it is to study the issue of vegetation changes and the formation of the landscape within an industrial city. The described results are important for the management of urban greening issues. Human influence on the disintegration and development of the natural environment is clearly visible. Due to the diversity of former mining areas and their time of creation, the studied area is one of the most important experimental areas for the determination link between vegetation and soil.

Analysis of Spatio-Temporal Changes in the Vegetation Cover of the Coastal Landscape of Doñana

Munoz-Reinoso, J.C.; Villafuerte Jordan, R; Tejada-Tejada, M., 2020. Analysis of spatio-temporal changes in the vegetation cover of the coastal landscape of Donana. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 113-117. Coconut Creek (Florida), ISSN 0749-0208.The analysis of changes is an important component in the understanding of the ecology of complex landscapes. The aim of this work was to study the long-term changes in the vegetation of the sands of Donana since 1970 until present, in order to know their causes and processes. Repeated detailed photointerpretation of historical aerial images (1970, 1984, 2002, 2016) was used to map the most extended vegetation types in the Donana sands. All the series were referenced, photointerpreted and normalized, and then processed to describe the changes produced in landcover/use. Observed vegetation changes in the protected area responded to changes in regional landscape management, as well as to local interactions in plant communities, and management. Thus, groundwater abstraction for cropping and urban supply benefited the most xerophytic plant communities, while the building of a tourist site and of a spit in the Tinto-Odiel estuary seems to be responsible for the stabilization of the mobile dunes. The expansion of Phoenicean junipers shows a successional process while the encroachment of stone pines responds to an invasion process triggered by forestry works.

Future Projected Groundwater Level Trend Analysis using GIS Techniques

High Population Growth and increase the urban sprawl in earth to less the groundwater resources causes degradation of groundwater Level in India. Water is very important for our life and natural resources. There are various uses of groundwater just as drinking, irrigation, and manufacturing. Today we are facing the shortage of groundwater level. The main goal of study is, because of increase in the population there is increase the number of bore well in earth surface this the reason to declination of groundwater level, so in these study to analysis of spatio-temporal changes in groundwater level fluctuation in Bhopal district in Madhya Pradesh, India. According to censes in Huzur Tehsil, M.P, Bhopal District, in 2001 population is 1429132 and 2011 population is 1834493. Collected the total of 350 observation wells Huzur Tehsil, Bhopal district for point observations. And using the GIS techniques spatial Analysis tools in ArcGIS10.5 to find out different Change of Groundwater Level Fluctuation since period (1996-2015) and using Matlab to generate the GWL (groundwater level) modeling .Generate the Future projected Groundwater level Fluctuation(2016-2050) and Trend Analysis of Groundwater Level (1996-2015) and Future Projected Groundwater level (2016-2050).

TSPO imaging-guided characterization of the immunosuppressive myeloid tumor microenvironment in patients with malignant glioma.

Tumor-associated microglia and macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) are potent immunosuppressors in the glioma tumor microenvironment (TME). Their infiltration is associated with tumor grade, progression, and therapy resistance. Specific tools for image-guided analysis of spatiotemporal changes in the immunosuppressive myeloid tumor compartments are missing. We aimed (i) to evaluate the role of fluorodeoxyglucose (18F)DPA-714* (translocator protein [TSPO]) PET-MRI in the assessment of the immunosuppressive TME in glioma patients, and (ii) to cross-correlate imaging findings with in-depth immunophenotyping. To characterize the glioma TME, a mixed collective of 9 glioma patients underwent [18F]DPA-714-PET-MRI in addition to [18F]fluoro-ethyl-tyrosine (FET)-PET-MRI. Image-guided biopsy samples were immunophenotyped by multiparametric flow cytometry and immunohistochemistry. In vitro autoradiography was performed for image validation and assessment of tracer binding specificity. We found a strong relationship (r = 0.84, P = 0.009) between the [18F]DPA-714 uptake and the number and activation level of glioma-associated myeloid cells (GAMs). TSPO expression was mainly restricted to human leukocyte antigen D related-positive (HLA-DR+) activated GAMs, particularly to tumor-infiltrating HLA-DR+ MDSCs and TAMs. [18F]DPA-714-positive tissue volumes exceeded [18F]FET-positive volumes and showed a differential spatial distribution. [18F]DPA-714-PET may be used to non-invasively image the glioma-associated immunosuppressive TME in vivo. This imaging paradigm may also help to characterize the heterogeneity of the glioma TME with respect to the degree of myeloid cell infiltration at various disease stages. [18F]DPA-714 may also facilitate the development of new image-guided therapies targeting the myeloid-derived TME.

Changes of Annual Precipitation and Probability Distributions for Different Climate Types of the World

Analysis of Spatio-temporal changes in precipitation (Pre) on the land surface of the earth was the focus of this study. Thiel-Sen median slopes and Modified Mann-Kendall (MMK) test were utilized to draw inferences. Majority of the regions were identified to show an increasing trend of annual precipitation except some of the low to mid-latitude regions in Northern hemisphere. The trends of wet-day frequency (Wet) were found in agreement with precipitation for most of the regions, but the inverse relationship was found for the subtropical regions of Northern hemisphere. These changes were examined for the world climate types based on Koppen-Gieger climate classes. Also, it was tried to find the probability distribution, which best describes the annual precipitation pattern in different climate types of the world among 21 commonly assumed probability distributions.

Riparian wetland rehabilitation and beaver re-colonization impacts on hydrological processes and water quality in a lowland agricultural catchment

Quantifying the catchment water balance and the characterization of its water quality changes are effective tools for establishing the response of catchments to shifting land management practices. Here we assess long-term hydrological partitioning and stream water chemistry over a 30-year period in a rural mixed land use catchment in northern Germany undergoing riparian wetlands and widespread re-colonization by beavers (Castor fiber) along the river network. We used long-term spatially distributed stream discharge, groundwater levels and surface water quality data with a simple monthly water balance model, changes in the variability in discharge measurements, and statistical analysis of spatio-temporal changes in stream water quality to assess long-term changes. Water balance estimates indicated high proportions of evapotranspiration loss (~90% of total precipitation) and relatively low groundwater recharge (<5% of total precipitation) prior to riparian rehabilitation in 2000. Increasing groundwater levels from 2000 to 2017 and the relatively linear nature of the catchment storage – discharge relationship, indicate a gradual increase in groundwater recharge (buts still <10% of total precipitation). Wetland rehabilitation, greatly enhanced by increasing beaver populations, resulted in longer water transit times in the stream network, less linear storage-discharge relationship and a loss of daily stream variability, increased DOC concentrations, isotopic evaporative enrichment downstream, and moderated stream temperatures. There was limited long-term water quality improvements from wetland rehabilitation on either nitrate or total phosphorus concentrations, with unchanged seasonal summer and winter peak concentrations for phosphorus and nitrate, respectively. This likely reflects the long-term legacy of fertilizer use on nutrient reservoirs in the catchment's soils, aquifers, and stream network. These long-term changes in hydrology and stream chemistry resulting from riparian rehabilitation and changes in agricultural management practices provide invaluable insights into catchment functioning and an evidence base for future planning in relation to long-term climatic changes.

Spatiotemporal Changes in the Macrophytobenthos of Laspi Bay (Crimea, Black Sea)

Using a landscape approach, the paper presents for the first time the results of a comparative analysis of spatiotemporal changes in the macrophytobenthos, performed in the Laspi Bay for the period from 1983 to 2008 with landscape maps of Laspi Bay compiled by the authors. In addition, it describes the distribution of the bottom natural complexes with key Black Sea phytocoenoses. It was found that over a span of 25 years, the plant components of bottom natural complexes in Laspi Bay underwent significant restructuring and degradation due to natural factors and anthropogenic activity in the coastal zone.

Intensification of the Daily Wet Day Rainfall Distribution Across Australia

AbstractIn Australia and globally, changes in the entire distribution of daily precipitation are poorly understood. An analysis of spatiotemporal changes in the intensity and frequency of wet and all day Australian rainfall between 1958–1985 and 1986–2013 is presented using three different gridded data sets of daily precipitation based on varying underlying station data and interpolation methods. Our analysis method provides a complete picture of changes in the entire distribution as well as a coherent picture of the spatial changes across Australia. We find that the spatial pattern of changes in total rainfall is similar to the pattern of change in wet day frequency but not to change in wet day intensity. Furthermore, more grids across Australia show statistically significant increases than decreases in rainfall intensity throughout the wet day distribution. This means that when it rains (i.e., limited to the wet day distribution), whether it is light, moderate, or extreme rainfall, it rains more.

Atlas of tissue- and developmental stage specific gene expression for the bovine insulin-like growth factor (IGF) system.

The insulin-like growth factor (IGF) axis is fundamental for mammalian growth and development. However, no comprehensive reference data on gene expression across tissues and pre- and postnatal developmental stages are available for any given species. Here we provide systematic promoter- and splice variant specific information on expression of IGF system components in embryonic (Day 48), fetal (Day 153), term (Day 277, placenta) and juvenile (Day 365–396) tissues of domestic cow, a major agricultural species and biomedical model. Analysis of spatiotemporal changes in expression of IGF1, IGF2, IGF1R, IGF2R, IGFBP1-8 and IR genes, as well as lncRNAs H19 and AIRN, by qPCR, indicated an overall increase in expression from embryo to fetal stage, and decrease in expression from fetal to juvenile stage. The stronger decrease in expression of lncRNAs (average ―16-fold) and ligands (average ―12.1-fold) compared to receptors (average ―5.7-fold) and binding proteins (average ―4.3-fold) is consistent with known functions of IGF peptides and supports important roles of lncRNAs in prenatal development. Pronounced overall reduction in postnatal expression of IGF system components in lung (―12.9-fold) and kidney (―13.2-fold) are signatures of major changes in organ function while more similar hepatic expression levels (―2.2-fold) are evidence of the endocrine rather than autocrine/paracrine role of IGFs in postnatal growth regulation. Despite its rapid growth, placenta displayed a more stable expression pattern than other organs during prenatal development. Quantitative analyses of contributions of promoters P0-P4 to global IGF2 transcript in fetal tissues revealed that P4 accounted for the bulk of transcript in all tissues but skeletal muscle. Demonstration of IGF2 expression in fetal muscle and postnatal liver from a promoter orthologous to mouse and human promoter P0 provides further evidence for an evolutionary and developmental shift from placenta-specific P0-expression in rodents and suggests that some aspects of bovine IGF expression may be closer to human than mouse.

Analysis of spatiotemporal land cover changes in Inner Mongolia using self-organizing map neural network and grid cells method

Land use has changed dramatically in the Inner Mongolia Autonomous Region because of rapid economic growth and human disturbances. However, little information is available about the medium- and long-term land use changes in this region. The effects of ecological recovery policies have also been evaluated rarely. In this study, we employed the self-organizing map neural network method to identify the land cover changes in Inner Mongolia between 2000 and 2014. MOD13Q1, Landsat, and DMSP/OLS night-time light data were used as the data resources. The dynamic change map was characterized using the grid cell method. The results showed that urban area of Inner Mongolia increased by more than five times during the 15-year study period, while the mining area also increased. In addition, 35.3% of the farmland was changed into grassland, which may have been caused by the “Grain to Green” policy. The most significant environmental issue in Inner Mongolia is the loss of wetland. >40% of the wetland was converted into other land use types between 2000 and 2014. Grassland increased by 6.05%, but areas of open water and woodland remained about the same. In terms of the geographical distribution, cropland increased in the eastern and middle parts of the region. The transformation from wetland to grassland mainly occurred in the north. Grassland degradation occurred in the west. Thus, environmental policy has resulted in some ecological improvements in Inner Mongolia. However, new environmental problems associated with rapid economic development should be addressed in a timely manner.

Spatiotemporal changes and drivers of global land vegetation oxygen production between 2001 and 2010

Oxygen is a sensitive indicator of atmospheric compositional changes, and also a primary requirement for human life. Values for the normalized difference vegetation index (NDVI), temperature, and radiation are input into the C-FIX model in this study in order to simulate global net ecosystem productivity (NEP). According to carbon–oxygen equilibrium theory, NEP is further converted into oxygen production by land vegetation around the world. Thus, an in-depth analysis of spatiotemporal changes in the oxygen production of land vegetation globally is presented in this study alongside a discussion of relevant mechanisms of change. The results of this research show that global annual average oxygen production between 2001 and 2010 had a significant increasing trend, amounting to 194 × 1010 t, at a rate of 0.78 × 109 t/a. Data show that the most obvious increases in oxygen production occurred in Asia, Europe, and North America, while changes in Africa, South America, and Oceania were insignificant. Global maximum oxygen production was seen in South America, encompassing roughly 30% of the global total, while between 2001 and 2010, the distribution of production by global land vegetation can be characterized by a gradual decrease from the equator to the poles. Production on approximately 12.0% of global landmass increased significantly (mainly in eastern Siberia, eastern Europe, and in the western part of North America), while a significant decrease was observed on approximately 5.43% of global landmass (mainly in western Siberia, central Africa, and the southern part of South America). At the same time, changes in carbon dioxide (CO2) concentration and vegetation resulted in an overall increase in global oxygen production, while climate change led to a decrease. Moreover, the increase of CO2 concentration is the main factor for the significant increase in the total oxygen production of land vegetation in the world, accounting for 70.0%, while the conversion of cultivated land and grassland into forested land led to significant global decreases. The main contributions of this study are thus to reveal the spatial distribution of, and variation in, global oxygen production by vegetation over the last decade, and to clarify the factors that have influenced these changes.

基于MODIS与Landsat 8的艾比湖湿地旱情时空变化及其影响因素分析

PDF HTML阅读 XML下载 导出引用 引用提醒 基于MODIS与Landsat 8的艾比湖湿地旱情时空变化及其影响因素分析 DOI: 10.5846/stxb201705060837 作者: 作者单位: 新疆大学资源与环境科学学院;新疆大学绿洲生态教育部重点实验室;新疆智慧城市与环境建模普通高校重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（41130531）；2016新疆研究生科研创新项目（XJGRI2016013）；国家自然科学基金地区项目（41561089） Analysis of spatiotemporal changes in the drying of the Ebinur Lake Basin and its influencing factors based on MODIS and Landsat 8 satellites Author: Affiliation: Xinjiang University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对干旱区艾比湖湿地旱情进行多源遥感监测，分析干旱对艾比湖湿地的生态安全与农业生产的影响，为水资源合理配置与干旱预警提供依据。选用2013年5月到2016年5月的MODIS温度和植被指数产品数据反演TVDI指数，并构建二维特征空间，分析土壤水分的时空分布特征，结果表明：TVDI可以有效地反演土壤水分，且精度较高；通过分析，艾比湖湿地土壤水分格局呈现由"极湿润-湿润-正常"面积减少，"干旱-极干旱"面积增加的趋势；在此基础上分析了影响艾比湖干旱变化的影响因素，近年来随着温度升高，风速与蒸发量增加，降水量减少，使艾比湖湿地旱情急剧恶化。利用多源遥感能很好的实现大面积、长时间、高精度的旱情监测，在四年间艾比湖湿地的旱情有所加剧，湖水面积与冰川萎缩变化较为严重，可见艾比湖湿地旱情情况较为不乐观，需加强水资源管理，开展艾比湖旱情监测对于干旱区湖泊生态有重要的理论与实际意义。 Abstract:By using multisource remote sensing data, the drought data of Ebinur Lake wetland in an arid region was extracted and the impacts of drought on the ecological environment and agriculture were analyzed, providing the basis for reasonable management of water resources and the drought warning system. MODIS vegetation and temperature products and Landsat 8 data were used to extract the NDVI and LST in order to inverse temperature and vegetation dryness index (TVDI), and at the same time construct 2-Dimension feature space and analyze the spatiotemporal change of soil moisture. The results showed that the TVDI model has higher precision to effectively inverse regional soil moisture; from 2013 to 2016 in a 4-year span, the Ebinur Lake soil moisture has shown that the wet, normal, and light drought area is decreasing, while the drought and heavy drought area is increasing. In addition, the team analyzed the driving forces in some respects. In recent years, the increase in temperature, population, wind speed, and precipitation showed downward trends, and drought has reduced sharply. It is better to use multisource remote sensing data to efficiently accomplish drought monitoring in a wide area for a long time. The drought in Ebinur Lake wetland intensified during the four years, and the lake water and glacier area are shrinking at a faster rate. The Ebinur Lake regional soil moisture distribution is not improving. In order to protect the regional ecological system, effective local water resources management should be enhanced. In conclusion, carrying out research on the spatial and temporal dynamic changes and the driving forces for drying of Ebinur Lake has important theoretical and practical significances for this arid zone. 参考文献 相似文献 引证文献

Analysis of Spatiotemporal Changes in Land Use and Land Cover in Sub-Watersheds of the Lower Itapecuru River in the State of Maranhão, Brazil

Este estudo foi destinado para realizar uma análise detalhada da dinâmica espaço-temporal dos padrões do uso e cobertura da terra em dez sub-bacias hidrográficas localizadas no Baixo Curso do Rio Itapecuru, no Estado do Maranhão. A avaliação foi processada por meio do mapeamento de imagens Landsat-5 Thematic Mapper, referentes aos anos de 2005, 2010 e 2015, que foram adquiridas gratuitamente junto ao Instituto Nacional de Pesquisas Espaciais – INPE. Para o mapeamento, foram utilizadas as seguintes classes de UCT: ocupação (alta, média e baixa), vegetação (alta, média, baixa), solo exposto, agricultura, campo inundável e água continental. Os resultados mostraram que as classes “vegetação alta” e “vegetação média” foram predominantes nos três anos analisados. As principais mudanças foram evidenciadas nas SBHs 1, 2 e 10. Nas SBHs 1 e 2, foram impulsionadas pela supressão da vegetação durante a etapa de terraplenagem de empreendimento petroquímico localizado no Município de Bacabeira, enquanto que, na SBH-10, o principal agente modificador foi a expansão das áreas ocupadas da cidade de Rosário. No entanto, num cenário futuro, existe a possibilidade da chegada de novos empreendimentos na região do BCRI, os quais, irão potencializar a pressão sobre os recursos naturais das demais SBHs, com a real possibilidade de ocorrerem mudanças significativa nos padrões de paisagem, gerando consequências negativas sobre a qualidade de vida das comunidades locais e funcionamento dos ecossistemas naturais. As informações obtidas sugerem o estabelecimento de estratégias de gerenciamento ambiental que antecipem a chegada de futuros empreendimentos, considerando a capacidade de suporte do ambiente e compatibilizando sua implantação com a manutenção das características socioambientais inerentes ao BCRI

Analysis of Dynamic Spatiotemporal Changes in Actual Evapotranspiration and Its Associated Factors in the Pearl River Basin Based on MOD16

Evapotranspiration is an important part of the hydrological cycle, surface energy balance and global climate system. Due to spatial heterogeneity, the trends in actual evapotranspiration (ET) and its associated factors vary in different regions. Because direct measurements of ET are limited over large areas, remote sensing provides an efficient method of ET spatial analysis, and standard data products are available at the global scale. This study uses the monthly MOD16 ET dataset and daily meteorological data to analyze the dynamic spatiotemporal changes in ET and its associated factors in the Pearl River Basin (PRB) from 2000 to 2014. The results of the study are as follows. (1) Over time and space, annual ET exhibited a slight increasing trend from 2000 to 2014, with an average value of approximately 946.56 mm/a. ET considerably varied at the monthly and seasonal scales, and in July displayed the highest monthly ET of approximately 119.57 mm, accounting for 36.37% of the annual ET. (2) ET displayed obvious spatial heterogeneity. Specifically, the west was a low-ET region, and moderate and high ET values were interspersed in the central and eastern PRB. Moreover, the rate of change of ET ranged from −13.99 mm/a to 12.81 mm/a in space, and 46.25% of the basin exhibited an increasing trend. (3) Dynamic changes in ET were mainly associated with temperature and relative humidity (RH). Additionally, energy-related elements and wind speed were positively correlated with ET, and temperature was the most influential factor of ET in some months (February–March and September–November). RH was the most important factor in other months but negatively correlated with ET in June and July. Affected by the actual environmental condition, qualitative changes were observed in the correlation between RH and ET in different months. The positive and negative spatial correlations between ET and its associated factors changed in different regions and in different months, and the changes mainly occurred from northwest to southwest.

Analysis of spatiotemporal changes of the human-water relationship using water resources constraint intensity index in Northwest China

Water resources constraint intensity (WRCI) refers to the conflict degree between water scarcity and human activities. We provide a comprehensive dynamic assessment index system for WRCI, which is composed of three primary indicators (natural endowment, exploitation and utilization degree, exploitation and utilization efficiency of water resources) and nine secondary indicators. After ascertaining the thresholds and grading standards for each specific indicator and their integrated indexes according to the experience of developed countries and regions, we employ an Analytic Hierarchy Process (AHP) model reformed by entropy technology to calculate their weights, and establish a multi objective fuzzy membership function to calculate the normalized values. Subsequently, we use the statistical data of 51 prefecture level regions in Northwest China during 2000–2014 to analyze the spatiotemporal changes of WRCI and its primary and secondary indicators. The results show that WRCI in the whole region of Northwest China belonged to the less strong or weak constraint type during the period. However, Northwest China was confronted with great disparity in human-water relationship according to the temporal and spatial changes of WRCI and its primary and secondary indicators. About 1/3 of prefecture level regions belonged to the strong and very strong constraint type. About 1/3 belonged to the less strong constraint type. Only about 1/3 belonged to the weak and very weak constraint type. The framework provides a relatively absolute evaluation of the conflict degree between the human-water systems. It might help to scientifically understand the spatiotemporal features of the relationship between water scarcity and human activities for Northwest China, and also has the potential for application in other areas and scales for monitoring and comparison purposes in space and over time.