Based on digital land use data from 1995 to 2000 and road data, the land use and landscape changes of Golmud, Qumaleb and Zhidoi are studied on a macro-scale. Land use and landscape changes in highway buffer zones and city expansion are special subjects. A new formula is used to define the exact degree of dynamic land use. To adequately define land use and landscape pattern changes, the buffer zones, illustrating the changes at different distances from the road, are recognized with ArcGIS 8.1 software. Prominent changes took place in land use and landscape patterns from 1995 to 2000, and the area of built-up land increased by 323.8%. The comprehensive degree of dynamic land use is 2.25, and the degree of dynamic land use of built-up land is the highest, followed by cultivated land. Woodland has the lowest value. The used degree index of land resources declined by 38.8 from 1995 to 2000. Landscape changed dramatically which influenced ecological processes immensely. Different from the corridor effect of other traffic routes, the corridor effect of this section of road is not obvious and its "point" radiation effect can be easily seen. The expanding range of Golmud City is confined to a 3 km buffer, while for Wudaoliang, it is 1 km. No land use change happened in the Nanshankou buffer.

Using ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) infrared remote sensing data we inversed the parameters of urban surface heat fluxes applying the PCACA model and theoretical position algorithm, and then we analyzed the influence of different land use types on the surface heat fluxes and energy balance. In this study, Kumagaya, a city in Saitama Prefecture, Japan, was selected as the experimental area. The result shows that the PCACA model is feasible for the surface heat fluxes estimation in urban areas because this model requires less parameters in the procedure of heat fluxes estimation in urban areas with complicated surface structure and can decrease the uncertainty. And we found that different land-use types have indicated the height heterogeneity on the surface heat fluxes significantly. The magnitudes of Bowen ratio in descending order are industrial, residential, transportation, institutional, dry farmland, green space, and water body. Under the same meteorological condition, there are distinct characteristics and regional differences in Bowen ratios among different surface covers, indicating higher sensible heat flux and lower latent heat flux in the urban construction land, while lower sensible heat flux and higher latent heat flux in the vegetation-covered area, the outskirt of the urban area. The increase of urban impervious surface area caused by the urban sprawl can enlarge the sensible heat flux and the Bowen ratio, so that it causes the increasing of urban surface temperature and air temperature, which is the mechanism of the so-called heat island effect.

According to the textual research into the historical documents dominated by ar-chives yearly, as well as the verification with several other kinds of data, the later or earlier starting time of the rainy seasons in Yunnan during 1711–1982 has been reconstructed. The analysis indicates that there are obvious fluctuations in the starting date of the rainy seasons in Yunnan in a year or years, and long fluctuation on the decadal scale. The rainy season comes earlier in the early 18th century, later in the 19th century and earlier again in the 20th century. This reflects to a certain degree the gradual change of the summer monsoon in Yunnan. There exists an obvious quasi-3 years cycle, which is related to El-Nino’s quasi-3 years cycle, and a 11.3-year cycle which is notably related to the 11-year cycle of the solar activity of starting date of the rainy seasons in Yunnan. Meanwhile, the dissertation finds that the El-Nino is very important to the starting date of the rainy seasons in Yunnan. The starting date of the rainy seasons in Yunnan often comes later or normally in the year of El-Nino. However, there is an obvious imperfect period in such influence, which in turn may mean that there is a certain fluctuation in the effect of ENSO on Asian summer monsoon.

The immense and towering Tibetan Plateau acts as a heating source and, thus, deeply shapes the climate of the Eurasian continent and even the whole world. However, due to the scarcity of meteorological observation stations and very limited climatic data, little is quantitatively known about the heating effect and temperature pattern of the Tibetan Plateau. This paper collected time series of MODIS land surface temperature (LST) data, together with meteorological data of 137 stations and ASTER GDEM data for 2001-2007, to estimate and map the spatial distribution of monthly mean air temperatures in the Tibetan Plateau and its neighboring areas. Time series analysis and both ordinary linear regression (OLS) and geographical weighted regression (GWR) of monthly mean air temperature (Ta) with monthly mean land surface temperature (Ts) were conducted. Regression analysis shows that recorded Ta is rather closely related to Ts, and that the GWR estimation with MODIS Ts and altitude as independent variables, has a much better result with adjusted R² > 0.91 and RMSE = 1.13-1.53℃ than OLS estimation. For more than 80% of the stations, the Ta thus retrieved from Ts has residuals lower than 2℃. Analysis of the spatio-temporal pattern of retrieved Ta data showed that the mean temperature in July (the warmest month) at altitudes of 4500 m can reach 10℃. This may help explain why the highest timberline in the Northern Hemisphere is on the Tibetan Plateau.

In this paper, the spatial and temporal distribution of the settlement sites of six periods from the Neolithic Age to the Shang and Zhou dynasties in northern Shandong was investigated using the ArcGIS program, and the relationship between settlement distribution and environmental changes was discussed, based on the proxy records of climatic and environmental change contained in the sediments from three sections at the Shuangwangcheng site and the previous work. The results show that the climate was warm and humid and the sea level was relatively high during the period of 8000-5000 a BP in the study area, and the ancient people lived in the relatively flat (slope of <2°) areas at high elevation (20-300 m above sea level), such as diluvial tableland and alluvial plain. On the other hand, few archaeological sites in the low-lying plain in the west of the study area indicate that few people lived there during that period. This might be attributed to frequent flooding in the area. After 5000 years ago, the scope of human activity extended to the area close to the sea because the relatively colder and drier climate results in sea-level fall, meanwhile the low-lying plain in the west was occupied by the ancient people. The study area of this period was characterized by the rapid development of prehistoric culture, the intensified social stratification and the emergence of early city-states. However, around 4000 a BP, the abrupt change in climate and the increase in frequency and intensity of floods severely disrupted human activities, and eventually led to the decline of the Yueshi culture. During the Shang and Zhou dynasties, the climatic conditions gradually stabilized in a mild-dry state, which promoted the redevelopment and flourish of the Bronze Culture. The previous situation, which was characteristic of sparse human settlements due to freshwater shortage and unfitted conditions for sedentary agriculture, changed during the Shang and Zhou dynasties in northern coastal wetlands.Local residents effectively adapted themselves to the tough environmental conditions by producing sea-salt, which led to the rapid growth of human activities.

Using foggy days and mean temperature and relative humidity data of 602 stations from January to December in the period 1961–2003 in China, the relationship between variations of foggy days and temperature and its possible reason for the 43 years were analyzed by regression, correlation and contrastive analysis methods. The results show that the higher (lower) the mean temperature and the lower (higher) the relative humidity correspond to less (more) foggy days, the relationship is the best in the western, northern and eastern Sichuan, Yunnan-Guizhou Plateau, and southeast highland in China. This induces a decrease in relative humidity when the climate becomes warmer, and eventually brings about a decrease in foggy days in China.

Rural hollowing is a recent geographic phenomenon that has received significant attention in China, which is experiencing rapid urbanization. It has led to the wasteful use of rural land resources, and imposed obstacles on the optimization of land use and coordinated urban-rural development. Rural hollowing has various forms of manifestation, which refers to the neglect and vacancy of rural dwellings, both of which can lead to damage and ultimate abandonment of rural dwellings. Damaged dwellings have different degrees of destruction, ranging from slight, moderate to severe. The evolutive process of rural hollowing in general has five stages, i.e., emergence, growth, flourishing, stability, and decline. Based on the combination of both regional economic development level and its physiographic features, the types of rural hollowing can be categorised as urban fringe, plain agricultural region, hilly agricultural region, and agro-pastoral region. Especially, the plain agricultural region is the most typical one in rural hollowing, which shows the spatial evolution of rural hollowing as a “poached egg” pattern with a layered hollow core and solid shape. Furthermore, the driving forces behind rural hollowing are identified as the pull of cities and push of rural areas. In particular, this paper identifies contributors to rural hollowing that include rural depopulation in relation to rapid urbanisation and economic change, land ownership and land use policy, and institutional barriers.

The United States, Russia and China are militarily and economically among the most powerful countries in the post-Cold War period, and the interactions between the three powers heavily influence the international system. However, different conclusions about this question are generally made by researchers through qualitative analysis, and it is necessary to objectively and quantitatively investigate their interactions. Monthly-aggregated event data from the Global Data on Events, Location and Tone (GDELT) to measure cooperative and conflictual interactions between the three powers, and the complementary cumulative distribution function (CCDF) and the vector autoregression (VAR) method are utilized to investigate their interactions in two periods: January, 1991 to September, 2001, and October, 2001 to December, 2016. The results of frequencies and strengths analysis showed that: the frequencies and strengths of USA-China interactions slightly exceeded those of USA-Russia interactions and became the dominant interactions in the second period. Although that cooperation prevailed in the three dyads in two periods, the conflictual interactions between the USA and Russia tended to be more intense in the second period, mainly related to the strategic contradiction between the USA and Russia, especially in Georgia, Ukraine and Syria. The results of CCDF indicated that similar probabilities in the cooperative behaviors between the three dyads, but the differences in the probabilities of conflictual behaviors in the USA-Russia dyad showed complicated characteristic, and those between Russia and China indicated that Russia had been consistently giving China a hard time in both periods when dealing with conflict. The USA was always an essential factor in affecting the interactions between Russia and China in both periods, but China’s behavior only played a limited role in influencing the interactions between the USA-Russia dyad. Our study provides quantitative insight into the direct cooperative and conflictual interactions between the three dyads since the end of the Cold War and helps to understand their interactions better.

Lake water level is an essential indicator of environmental changes caused by natural and human factors. The water level of Poyang Lake, the largest freshwater lake in China, has exhibited a dramatic variation for the past few years, especially after the completion of the Three Gorges Dam (TGD*However, there is a lack of more accurate assessment of the effect of the TGD on the Poyang Lake water level (PLWL) at finer temporal scales (e.g., the daily scale*Here, we used three machine learning models, namely, an Artificial Neural Network (ANN), a Nonlinear Autoregressive model with eXogenous input (NARX), and a Gated Recurrent Unit (GRU), to simulate the daily lake level during 2003-2016. We found that machine learning models with historical memory (i.e., the GRU model) are more suitable for simulating the PLWL under the influence of the TGD. The GRU-based results show that the lake level is significantly affected by the TGD regulation in the different operation stages and in different periods. Although the TGD has had a slight but not very significant impact on the yearly decline of the PLWL, the blocking or releasing of water at the TGD at certain moments has caused large changes in the lake level. This machine-learning-based study sheds light on the interactions between Poyang Lake and the Yangtze River regulated by the TGD.

It is of necessity to investigate the adjustment of flood discharge capacity in the Lower Yellow River (LYR) because of its profound importance in sediment transport and flood control decision-making, and additionally its magnitude is influenced by the channel and upstream boundary conditions, which have significantly varied with the ongoing implementation of soil and water conservation measures in the Loess Plateau and the operation of the Xiaolangdi Reservoir. The braided reach between two hydrometric stations of Huayuankou and Gaocun in the LYR was selected as the study area. Different parameters in the study reach during the period 1986-2015 were calculated, covering bankfull discharge (the indicator of flood discharge capacity), the pre-flood geomorphic coefficient (the indicator of channel boundary condition), and the previous five-year average fluvial erosion intensity during flood seasons (the indicator of incoming flow and sediment regime*Functional linkages at scales of section and reach were then developed respectively to quantitatively demonstrate the integrated effects of channel and upstream boundary conditions on the flood discharge capacity. Results show that: (1) the reach-scale bankfull discharge in the pre-dam stage (1986-1999) decreased rapidly by 50%, accompanied with severe channel aggradation and main-channel shrinkage. It recovered gradually as the geometry of main channel became narrower and deeper in the post-dam stage, with the geomorphic coefficient continuously reducing to less than 15 m^-1/2*2) The response of bankfull discharge to the channel and upstream boundary conditions varied at scales of section and reach, and consequently the determination coefficients differed for the comprehensive equations, with a smallest value at the Jiahetan station and a highest value (0.91) at reach scale. Generally, the verified results calculated using the comprehensive equations agreed well with the corresponding measured values in 2014-2015*3) The effect of channel boundary condition was more prominent than that of upstream boundary condition on the adjustment of bankfull discharge at the Jiahetan station and the braided reach, which was proved by a larger improvement in determination coefficients for the comprehensive equations and a better performance of geomorphic coefficient on the increase of bankfull discharge.

Tidal creeks are the main channels of land-sea ecosystem interactions, and their high dynamics are an important factor affecting the hydrological connectivity of tidal flats. Taking the Yellow River Delta as the research area, we selected remote sensing images obtained during five periods from 1998 to 2018 as the data sources. Based on the spatial analysis function in GIS, the typical morphological characteristics of tidal creeks, such as the level, length, density, curvature, bifurcation ratio, and overmarsh path length (OPL), were extracted to characterize the degree of development of the tidal creeks in the Yellow River Delta wetlands. The spatio-temporal evolution of the tidal creeks was studied, and the development process and the characteristics of the tidal creeks during the different stages of development were investigated. The results revealed that (1) The number, density, and bifurcation ratio of tidal creeks exhibit an increasing trend, but the growth of the trend is slowing. The number of tidal creeks increased by 44.9% from the initial stage of the Yellow River diversion to the late stage of the wetland restoration, but it only increased by 26.2% from the late stage of the wetland restoration to the slow expansion of the Spartina alterniflora*2) The curvature of the tidal creeks on the landward side is greater than that on the seaward side*3) The development degree of tidal creek has spatial heterogenetiy, which is Area III > Area II > Area I*4) The drainage efficiency is significantly correlated with the tidal creak density and bifurcation ratio. Based on the analysis of the various morphological parameters and the drainage efficiency, it was found that after the rapid change in the tidal creek system in the early stage, the tidal creeks entered a state of slow change, and the development state of the tidal creeks tends to be in dynamic balance. The results of this study are expected to provide scientific support for the sustainable development and utilization of coastal tidal flats.

Heavy metal pollution is hazardous for the environment and human health. However, there are few studies of heavy metal pollution caused by historic metallurgical activity. The Laoniupo site in the Bahe River valley, Guanzhong Basin, China, was an important settlement of the Shang Culture (1600-1046 BCE*We studied two stratigraphic profiles at the Laoniupo site, which were used for measurements of magnetic susceptibility, heavy metal concentrations, and AMS ¹⁴C ages to provide evidence of copper smelting activity at the site during the Shang Dynasty. The Nemerow Pollution Index and Geoaccumulation Index were calculated to assess the heavy metals record (Cu, Zn, Ni, Pb, Cr, and As) in the topsoil on the loess tableland. According to the Single Pollution Index, the topsoil was slightly polluted by As and unpolluted by Cu, Zn, Ni, Pb and Cr; according to the Nemerow Composite Pollution Index the topsoil was mildly polluted; and according to the Geoaccumulation Index, the topsoil was moderately polluted by As, slightly polluted by Cu, and unpolluted by Zn, Ni, Pb and Cr. The main cause of the heavy metal pollution in the topsoil is the presence of copper slag in the cultural layers that was disturbed by modern farming activity.

Background vales (mg/kg)

The construction of channel regulation projects, reservoirs, and other human activities have led to significant changes in channel geometry and hydrodynamic conditions in mountainous macrotidal estuaries. However, their impact on the long-term evolution of the turbidity maximum zone (TMZ) in these estuaries is still unclear. Therefore, the Minjiang Estuary (ME) was selected as the study area and using the Gabor filter and surface suspended sediment concentration (SSSC) data retrieved from GF PMS/WFV and Landsat-TM/ETM+/ OLI images in the flood season from 1986 to 2020, the flow direction of Chuanshi Waterway, the spatiotemporal evolution characteristics of TMZ in the ME, and the influence of human activities on these were analyzed. The results indicate that during flood tides in the past 35 years, the TMZ was mainly distributed in sections from the Changmen to the Chuanshi and Meihua waterways. The construction of the Shuikou Reservoir caused the SSSC to decrease by 65 mg/L at the Chuanshi Tidal Gauge Station in the ME. The TMZ in the ME waterway channel notably migrated toward the sea due to the waterway regulation project, with the landward and seaward boundaries moving by 2.5 km and 3 km seaward, respectively. The main distribution area moved from Jinpaimen to the section from Chuanshi Waterway to the mouth of the ME. These variation characteristics were basically consistent with the annual average TMZ in the flood season. Through the interactions between nature and human interventions, the flow regime of the ME tended to converge in the flood season. Therefore, human activities have significantly impacted the long-term evolution of the TMZ in the ME.

Understanding the hydrological effects of the Three Gorges Dam operation in the entire reservoir area is significant to achieving optimal dam regulation. In this paper, a large-scale coupled hydrological-hydrodynamic-dam operation model is developed to comprehensively evaluate the hydrological effects of the river-type Three Gorges Reservoir. The results show that the coupled model is effective for hydrological, hydrodynamic regime and hydropower simulations in the reservoir area. Dam operation could have a notable positive effect on flood control and could reduce the maximum daily flood peak by up to 26.2%. It also contributes a large amount of hydropower, approximately 94.27 TWh/year, and a water supply increase for the downstream area of up to 22% during the dry season. In the flood season, the water level at Cuntan would increase under the condition that the water level of the dam is higher than approximately 158 m due to dam operation. In the dry season, attention should be paid to the low flow velocity near the dam in the reservoir area.

Geopolitics of energy transition has increasingly become the frontier and hot research area of world energy geography and global political science. Different historical periods are characterised by obvious differences in energy connotations, attributes, and geopolitical characteristics. In the new energy era, energy geopolitics becomes more diversified, complex, and comprehensive. In this paper, we compare the geopolitical characteristics of energy in the fossil fuel and renewable energy periods, and provide an overview of current study trends in new energy geopolitics. Recent research shows that the global energy transition will intensify the reconstruction of geopolitical patterns, change the relationship between geopolitical security and conflict dominated by traditional energy security, alter the role of different countries in global energy geopolitical games, reshape national energy relationships formed in the traditional oil and gas era. In addition, geopolitics will be affected by new energy technologies, availability of key rare materials, and energy cybersecurity measures. Despite considerable attention to this research topic, the likely geopolitical impact of energy transition remains uncertain, and there is still room for the development and improvement of the theoretical framework, technical methods, and research perspective. Looking forward to the future, the research into geopolitics of energy transition urgently needs to strengthen its theoretical basis and rely on the scientific and quantitative methods. The practical conclusions of the research into geopolitics of energy transition should strengthen major national energy security decisions, explore the geographical effect of energy transition, and determine the impact of energy transition on energy security. Research into geopolitics of energy transition should be carried out taking into account international academic frontiers such as climate change, “carbon peak” and “carbon neutral” goals, and global energy governance, to enrich the research perspective of world energy geography.

Cross-domain research and development has prevailed in regional transformation and disruptive innovation in the last 15 years. Recently, a new concept, termed combinatorial knowledge bases (CKBs), offers insights into combining knowledge dynamics and is considered a good approach to explore recombinant innovative activities. Here, we review the literature on CKBs in Western economic geography, and we introduce a research agenda for CKBs in China’s economic geography. Concerning the latter, four aspects are elaborated: the co-evolution of the innovation chain and industrial chain, the geography of innovative activities, innovative entrepreneurship and new path development, and innovation system reconfiguration. This paper contributes to theoretical studies of China’s geography by linking CKBs to Chinese-specific phenomena.

As a kind of large-scale connectivity infrastructure, submarine cables play a vital role in international telecommunication, socio-economic development and national defense security. However, the current understanding about the spatial pattern of global submarine cable network is relatively limited. In this article, we analyze the spatial distribution and connectivity pattern of global submarine cables, and identify their strategic pivots and strategic channels. The main conclusions are as follows: (1) The spatial distribution of global submarine cables is significantly unbalanced, which is characterized by the facts that the distribution of submarine cable lines is similar to that of sea lanes, and the agglomerations of landing stations are distributed unevenly along the coastline. (2) The connectivity pattern of global submarine cable network has a significant scale effect. At the micro, meso and macro scales, the connectivity structure presents chain model, cluster model and hub-and-spoke model, respectively. (3) The distribution of strategic pivots and strategic channels shows a pyramidal hierarchical feature. Singapore ranks highest among all the strategic pivots, while the Gulf of Aden and the Strait of Malacca rank highest among the strategic channels. Based on the identification of strategic pivots and channels, six strategic regions have been divided, which face various network security risks and need special attention and vigilance.

Exploring the utilization effect of water-land resources under the evolution of dietary patterns is of great significance in achieving sustainable global food consumption and the effective allocation of national resources. Our selected study area was China, a country with rapidly changing dietary consumption patterns, and the research period was between 1987 and 2020. Based on the material called Chinese Dietary Guidelines 2021, this study introduced the “virtual water” and the “virtual land” to quantify the utilization effect of water-land resources under the evolution of Chinese dietary patterns. Results showed that the dietary patterns gradually changed from “cereal-vegetable-based consumption” to “diversified consumption”. Food consumption’s total water footprint (WF) increased from 471.1 Gm³ in 1987 to 848.8 Gm³ in 2020, with a growth rate of 80.2%. Moreover, the total land requirement for food (LRF) increased from 88.8 Mha in 1987 to 129.9 Mha in 2020, with a growth rate of 46.3%. Furthermore, the meat consumption was the major contributor to the increase in total WF (104.0%) and LRF (102.1%). In contrast to the balanced diet pattern, there was no waste of water-land resources consumption for the food consumption of urban-rural residents in China between 1987 and 2020. However, the consumption of water resources would gradually approach the resource cost under the balanced diet patterns. It would eventually break through the critical value and reach the state of resource waste. In addition, the findings showed that urban residents’ waste rate of water-land resources for meat consumption increased by 142.3% compared with that in 1987. The research results can provide scientific guidance for resolving the food crisis under the supply of water-land resources in China and have an essential reference for national food security and sustainable development of resources and environment.

Relatively coordinated development among cities can typically promote the integration of the whole urban agglomeration, while urbanization of land has been found important to economic development in developing countries. Numerous studies have measured the urban land expansion in urban agglomerations. However, urban land spatial inequality under a specific spatial structure remains poorly understood. Here, we combined the β-convergence model and the core-periphery structure to explore the dynamic changes in urban land spatial inequality in urban agglomerations. The Yangtze River Delta Urban Agglomeration (YRDUA) in China was selected as the study area. Indicators of urban land have been applied in conjunction with a modified conditional β-convergence model, while the existence of the core-periphery structure was tested by analyzing coefficients of the control variable. The results show that although the spatial inequality of urban land area had decreased during 2000-2020, the whole YRDUA had still shown an obvious core-periphery structure. Compared with urban land area, the spatial inequality of urban land economic density and population density had decreased more rapidly, and the core-periphery structure was less obvious. Our findings can help to improve our current understanding of urban agglomeration and serve as a scientific reference for the coordinated development of urban agglomerations.

Suitable spatial morphology of cultivated land is a basic requirement for sustaining agricultural economic development in mountainous areas. Coordinated development efficiency of cultivated land spatial morphology and agricultural economy (CECA) is of great practical significance to measure the efficiency of cultivated land use, and thereby promote regional rural revitalization. However, few studies to date have focused on coordinated development efficiency between cultivated land use and agricultural economy in mountainous areas from the perspective of cultivated land spatial morphology. Thus, the present study explores CECA with this focus using the data envelopment analysis method, and analyzes the key influencing factors via a geographical detector model in 16 counties in western Hubei province. The results show the following: (1) CECA exhibits significant spatial heterogeneity that is high in the south of the study area and low in the north; (2) scale efficiency is the primary limiting factor for CECA; (3) the insufficient output of cultivated land use mainly restricts CECA in the south of the study area, while individual county in the north suffered from input redundancy and insufficient output; and (4) population density in the southern region has the most significant effect on CECA, and gross domestic product has the greatest impact in the northern region. The results contribute to the derivation of specific measures by which to promote cultivated land use efficiency and sustainable development of the social economy.

Spatial and temporal changes in ecosystem services (ESs) are driven by two types of factors: environmental factors and trade-offs/synergies between services. In the ecological conservation red line (ECRL) area, in which national ecological security and social sustainable development are guaranteed, it is particularly important to clarify the driving mechanism of ESs for the management of ecosystems. In this study, soil conservation, water yield, and carbon sequestration in Beijing’s ECRL area are quantified, and GeoDetector is used to identify the factors influencing the trade-offs/synergies between ESs. Moreover, partial correlation analysis is used to calculate the net trade-offs/synergies and compare them with the extent to which environmental variables contribute to ESs. The results are as follows: environmental variables and trade-offs/synergies have different effects on the changes in ESs, and their interactions can enhance the determinative power of the corresponding individual variable. The land use intensity is an extremely important factor affecting the trade-offs/synergies between the three services, indicating that rational land use planning in Beijing’s ECRL area is crucial for avoiding the negative impacts of trade-offs and enabling coordinated optimization of ESs. After the elimination of the cross-influence of environmental variables, the trade-offs/synergies change significantly, and the impact of environmental variables on ESs is compared with the net trade-offs/synergies. Environmental variables are the driving forces of the spatiotemporal changes in soil conservation. Precipitation and carbon sequestration have similar effects on water yield. Spatiotemporal changes in carbon sequestration are closely related to the other two services, with smaller influences from environmental variables.

The Yellow River Basin (YRB) occupies an important position in China’s socioeconomic development and ecological conservation efforts. Understanding the spatiotemporal characteristics of the relationships among multiple ecosystem services (ESs) and their drivers is crucial for regional sustainable development and human-earth system coordination. This study simulated food production (FP), water yield (WY), net primary production (NPP), soil conservation (SC), and habitat quality (HQ) in the YRB from 2000 to 2020, and evaluated the spatial evolution and the relationship of ESs at the raster scale. Redundancy analysis was used to identify the impact of natural, socioeconomic, and landscape patterns on the relationship between ESs. The results demonstrated that the average HQ per unit area decreased by 18.10%, while SC, NPP, WY, and FP increased by 42.68%, 47.63%, 30.82%, and 67.10%, respectively, from 2000 to 2020. The relationship between ESs in the YRB was dominated by weak trade-offs and weak synergies at a temporal scale, with the trade-offs strengthened in the Upper Yellow River Basin (UYRB) and the Middle Yellow River Basin (MYRB), and synergies strengthened in the Lower Yellow River Basin (LYRB). At the spatial scale, the relationships between HQ and WY, HQ and SC, HQ and NPP, FP and SC, and FP and HQ were all dominated by trade-offs, while other ES pairs were mostly based on synergistic relationships. In the YRB, the relationships among ESs were mainly influenced by human disturbance, precipitation, and land-use and exploitation intensity. Specifically, the trade-offs among ESs in the UYRB were primarily affected by precipitation, and those in the MYRB and LYRB by human disturbance. The heterogeneity of the landscape could also effectively promote synergies among ESs. This study could provide insights into trade-offs and synergies among ESs and their driving forces and lay a foundation for ecological restoration and sustainable development of ESs in the YRB.

Wetland vegetation is intimately related to floodplain inundations, which can be seriously affected by dam operation. Poyang Lake is the largest floodplain wetland in China and naturally connected with the Yangtze River and the Three Gorges Dam (TGD) upstream. To understand the potential impacts of TGD on Poyang Lake wetlands, we collected remote sensing imagery acquired during dry season from 1987 to 2020 and extracted vegetation coverage data in the Ganjiang Northern-branch Delta (GND) and the Ganjiang Southern-branch Delta (GSD), using the Object-oriented Artificial Neural Network Regression. Principal components analysis, correlation analysis, and the random forest model were used to explore the interactions between vegetation extent in the two deltas and 33 hydrological variables regarding magnitude, duration, timing, and variation. The implementation of the TGD advanced and extended the low-flow periods in Poyang Lake. Vegetation coverage in the GND and GSD increased at the rates of 0.39 and 0.22 km²/year, respectively. The reservoir storage at the end of September accelerated the runoff recession in the GND and the GSD, making low-flow events more influential for vegetation dynamics and shortening the response time of vegetation to the water regime. This study provides an important reference for evaluating the impacts of dam engineering on downstream wetlands.

As they are products of glacier movement, the water body composition and water quality attributes of glacial lakes have distinct characteristics compared with inland lakes. Although satellite remote sensing provides an effective approach to monitor water quality, lack of in-situ measurement data on the status and environment surrounding glacial lakes presents a major constraint in relating satellite data to water quality indicators. This study presents findings of a preliminary investigation into water quality attributes of 3 glacial lakes in the Mount Qomolangma region. Suspended particulate matter (SPM), light absorption attributes of phytoplankton, nonalgal particles (NAP), and colored dissolved organic matter (CDOM) were measured. The suspended substance concentration varies markedly from 0-320 mg/L. This is considered to reflect differing stages of lake development. The chlorophyll concentration is much lower than that found for inland lakes, as landscapes that surround these high altitude lakes have almost no vegetation growth. The phytoplankton and CDOM concentration depend on long-term stability of lake slopes. Given the lack of exogenous and endogenous inputs in the Qomolangma region, CDOM in glacial lakes is significantly lower than in inland lakes. These preliminary findings could support efforts to appraise estimates of water quality parameters using remotely sensed images.

Ecological shelter zones reconstruction is an ecosystem restoration and conserva-tion project aimed to the ecological safety of nations, regions and basins. Reconstruction of ecological shelter zones of the upper reaches of the Yangtze River became one of the most important tasks of Western Development strategy. This article, taking Zhaotong as an exam-ple, studies the functional regionalization of ecological shelter zones. The study supplies a case for functional regionalization of small and medium regions whose main tasks are envi-ronment reservation. With the guidance of theories of functional regionalization, and based on the analysis of Zhaotong’s natural, ecological and socioeconomic factors, the paper suggests five principles for factors selection. These principles include: (1) reversing order evaluation; (2) selecting main factors; (3) keeping the integrality of administrative regions of towns; and (4) making the products acceptable by local government. To analyze spatial status of selected factors, LUCC data in 2002, 1:50,000 relief maps and town-unit socioeconomic statistical data in 2004 are used. RS and GIS tools are also applied to melt traditional and modern geo-graphical methods. This would be useful to functional regionalization research in mountain-ous areas. As a conclusion, the leading functional regions of ecological conservation or economic development are suggested, respectively. Zhaotong city is divided into two-level functional regions. The first-level includes three leading functional regions and they will lead developing direction of sub-regions. The second-level includes eight sub-regions, which are policy implemented regions, and will supply guidance to Zhaotong’s ecological shelter zones reconstruction.

Climate change is likely to affect hydrological cycle through precipitation, evapotranspiration, soil moisture etc. In the present study, an attempt has been made to study the climate change and the sensitivity of estimated evapotranspiration to each climatic variable for a semi-arid region of Beijing in North China using data set from 1951 to 2010. Penman-Monteith method was used to calculate reference crop evapotranspiration (ETo). Changes of ETo to each climatic variable was estimated using a sensitivity analysis method proposed in this study. Results show that in the past 60 years, mean temperature and vapor pressure deficit (VPD) were significantly increasing, relative humidity and sunshine hours were significantly decreasing, and wind speed greatly oscillated without a significant trend. Total precipitation was significantly decreasing in corn season (from June to September), but it was increasing in wheat season (from October to next May). The change rates of temperature, relative humidity, VPD, wind speed, annual total precipitation, sunshine hours and solar radiation were 0.42℃, 1.47%, 0.04 kPa, 0.05 m·s^-1, 25.0 mm, 74.0 hours and 90.7 MJ·m^-2 per decade, respectively. In the past 60 years, yearly ETo was increasing with a rate of 19.5 mm per decade, and total ETos in wheat and corn seasons were increasing with rates of 13.1 and 5.3 mm per decade, respectively. Sensitivity analysis showed that mean air temperature was the first key factor for ETo change in the past 60 years, causing an annual total ETo increase of 7.4%, followed by relative humidity (5.5%) and sunshine hours (-3.1%); the less sensitivity factors were wind speed (0.7%), minimum temperature (-0.3%) and maximum temperature (-0.2%). A greater reduction of total ETo (12.3%) in the past 60 years was found in wheat season, mainly because of mean temperature (8.6%) and relative humidity (5.4%), as compared to a reduction of 6.0% in ETo during corn season due to sunshine hours (-6.9%), relative humidity (4.7%) and temperature (4.5%). Increasing precipitation in the wheat season will improve crop growth, while decreasing precipitation and increasing ETo in the corn season induces a great pressure for local government and farmers to use water more efficiently by widely adopting water-saving technologies in the future.

The estimation of surface evapotranspiration (ET) with satellite dataset is one of the main subjects in the understanding of climate change, disaster monitoring and the circulation of water vapor and energy in Tibet Autonomous Region (TAR). This research selects satellite images on January 11, April 6, July 31 and October 19 in 2010 as the representative of winter, spring, summer and autumn respectively, estimates the distribution of daily surface ET based on the surface energy balance system (SEBS) along with potential evapotranspiration (PET) and ET derived from Penman-Monteith (P-M) method. The results are obtained as follows. (1) The seasonal distribution of ET and PET basically decreases from the southeast part to the northwest part of TAR. Although ET and PET have similar spatial distributions, there are still some differences to estimate the extreme values especially the maximum value in the middle and southeastern parts of TAR. No matter what kind of methods we adopted, the maximum value of ET and PET always appears in summer, followed by autumn or spring while that in winter is the smallest. (2) In order to better understand the accuracy of SEBS model in the estimation of ET, we compared the ET from SEBS and the ET obtained from P-M method. Results show that the ET from SEBS could estimates the variation trend of actual ET, but it slightly underestimates or overestimates the value of ET as a whole, especially for those areas with thick forest. (3) The spatial distribution of Normalized Difference Vegetation Index (NDVI) exhibits a decreasing trend from the southeast part to the northwest part of TAR which displays remarkable consistency of distributions between ET and vegetation index. ET is well positively related to NDVI, minimum, mean, maximum air temperature and sunshine duration in different seasons while negatively related to precipitation, relative humidity and wind speed in summer.

Based on the analysis of suspended sediment elements at estuaries, influence of human activities and estuarine regulation projects on the turbidity maximum zone was studied according to the measurement data between 1959 and 2011. It was found that human activities had little effect on the seaward water while the sharp decrease of sediment volume and concentration in runoff led to the sharp decrease of turbidity maximum zone in the estuary. The concentration at outside sea and Hangzhou Bay did not change, and that along the Subei coast also decreased a little, which had no influence on the turbidity maximum zone. Compared with the concentration between 1959 and 1999, the peak of concentration moved upstream in the estuary, and the concentration in 2000-2009 decreased by about 24.73% with a narrower variation range along the river to the sea. The suspended sediment concentration in North Passage was low in upstream and downstream because of the decrease of seaward sediment and coarsening of bed material, while it was relatively high in the middle due to the influence of sediment cross the north jetty.

The water quality in the surface microlayer (SML) and subsurface water (SSW) in the Guangzhou segment of Pearl River, a eutrophic urban river section in China, were analyzed. The spatial and temporal dynamics of nutrient concentrations, heavy metals and bacteria were examined from two sampling sites in monthly samples throughout 2010. The mean concentrations of total nitrogen, ammonia, nitrate and nitrite were higher than 7.0 mg/L, 3.1 mg/L, 1.1 mg/L and 0.3 mg/L, while total phosphorus and orthophosphate were 0.5 mg/L and 0.1 mg/L, respectively. These results indicated that the water quality was rich in minerals and eutrophic. The mean concentrations of Mn and Fe were higher than 0.013 mg/L; and Ni, Cr and Pb were higher than 0.001 mg/L. The mean concentrations were in the order of Mn >Fe > Ni > Pb > Cr. The concentrations of heavy metals in the Guangzhou segment were lower than the limit of the surface water quality standards in China and the World Health Organization (WHO), but higher than the median values in the world’s freshwater. The density of bacteria ranged from 3.30×10⁵ to 5.23×10⁶ cells/mL, and the amount of cultivable heterotrophic bacteria ranged from 1.30×10³ to 1.89×10⁶ cfu/mL. Fecal coliform levels were beyond the V class of China water quality standard. The SML was enriched in nutrients, heavy metals and bacteria, with the maximum enrichment factor of 3.84 for nutrients, 8.00 for heavy metals, and 3.04 for bacteria, suggesting that the water quality of the SML of the Guangzhou segment of the Pearl River was more serious than in the SSW.

It is important to quantitatively analyze the effects of protection of important ecological spaces in China to ensure national ecological security. By considering changes in the ecological land, this study examines the effects of protecting three types of important natural ecological spaces in China from 1980 to 2018. Moreover, considering important ecological spaces and their surroundings yields differences in the effects of protection between internal and external spaces, where this can provide a scientific basis for the categorization and zoning of China’s land. The results show the following: (1) In 2018, the ratio of ecological land to important natural ecological spaces accounted for 92.64%. This land had a good ecological background that reflects the developmental orientation of important ecological spaces. (2) From 1980 to 2018, the area of ecological land in important ecological spaces shrank but the rate of reduction was lower than the national average, which shows the positive effect of regulating construction in natural ecological spaces. The restorative effects of ecological projects to convert farmland into forests and grasslands have been prominent. The expanded ecological land is mainly distributed in areas where such projects have been implemented, and the reduced area is concentrated in grain-producing areas of the Northeast China Plain and agricultural oases of Xinjiang. In the future, the government should focus on strengthening the management and control of these areas. (3) The area ratio of ecological land was the highest in national nature reserves. The rate of reduction in its area was the lowest and the trend of reduction was the smallest in national nature reserves, which reflects differences in the status of ecological protection among different spaces. (4) The ratio of ecological land to important ecological spaces was higher than that in the surrounding external space, and the rate of reduction in it was lower. Thus, the effects of internal and external protection had clear differences in terms of gradient.