Since the launch of reform and opening up in the late 1970s, Chinese urban geography has gained rapid development and become the fastest growing and the most active branch of human geography. The development of Chinese urban geography has the following remarkable characteristics: (1) It combines urban planning practice closely, and always regards urban planning needs as the goal; (2) It establishes a mechanism for the introduction, absorption and conversion; (3) It promotes international cooperation in urbanization research actively; (4) In terms of theoretical research, urban geography absorbs a large number of experiences, theories and concepts in Western countries, and promotes the integration of Chinese urban geography theory with the West from the global perspective; (5) In the new situation of China's social development, it pays more attention to the concept of ecological environment and people-centered development, and promotes the development of its sub-disciplines. Young urban geographers have made discussions on the new trend of development of the Western urban geography, the evolution of urban industry, the evolution of urban spatial structure, the reshaping of the urbanization pattern, the new interpretation of China's development model, the application of large data and the innovation of qualitative method. In the future, the Chinese urban geography study should place more emphasis on the service in urban planning practice. Firstly, the new generation of urban geographers should absorb the advantages of other disciplines, and summarize the law of urban development in China based on China's national conditions. What's more, urban geographers should hold the power of speech in the policy and major strategies of national cities, such as the Belt and Road Initiative and the new urbanization strategy, and play an important role in the formulation of these policies. At last, we should continue to strengthen the international cooperation so as to raise the level of Chinese urban geography in the status of international academia
：Qiangtang Plateau (QP) refers as a typical interior region in the Tibetan Plateau, where the variability of precipitation is critical for cryospheric and ecosystems changes. However, the spatial distribution and variation of precipitation in the QP remains poorly understood due to lacking of precipitation gauges data. Based on precipitation data from nine automatic stations and five remote sensing and simulated precipitation products in 2015 and daily precipitation data from twenty-six meteorological stations during 1978-2015 in the QP and its vicinity, the spatial distribution and variation of precipitation were analyzed. Results showed that: (1) Annual precipitation and precipitation days were approximately 154.9 mm and 50 days in the core of the QP in 2015, respectively. Annual precipitation in the core of QP was approximately one third and one quarter of the average annual precipitation in the southeast of the QP and Tibet Autonomous Region, respectively. The lowest precipitation is observed on the north slope of the Kunlun Mountains, which confirms that this area is one of the main regions of 'cold dry core' in the perspective of precipitation. (2) The rainy season is clearly different from the dry season. The rainy season exists from June to August in the northern region, whose length is about 1-2 months shorter than that in the southern region. The distribution of precipitation in the northern region shows a single peak while that in the southern region shows a bimodal pattern. (3) TRMM (3B43) and GPM (IMERG) overestimated the annual precipitation in most sites of the QP, mainly due to the overestimation of precipitation in dry season. (4) A slight wetting process and an increasing trend of heavy rainfall events were detected in local area of the QP from 1978 to 2015.
The land cover datasets in the Qiangtang Plateau (QP) have generally been considered as the fundamental data in the studies of local environmental and ecological issues. We evaluated the accuracy of seven land cover datasets in the QP, i.e. International Geosphere-Biosphere Program's Data and Information System Cover (IGBPDIS), Global Land cover mapping at 30 m resolution (GlobeLand 30), The MODIS Land Cover Type product (MCD12Q1), Climate Change Initiative Land Cover (CCI-LC), Global Land Cover 2000 (GLC2000), GlobCover 2009 (GlobCover) and University of Maryland (UMD). For that, the study used 6851 field samples with first and second level (8 and 10, respectively) land cover types. Three widely used parameters were derived to describe the error matrix of the map and also for the overall user's and producer's accuracy. The quantitative assessments of the map quality and classification accuracy for the available land cover maps will help to improve the overall accuracy of land cover mapping in future. The overall results of the assessment pointed out that the GlobeLand 30 and CCI-LC land cover map have higher accuracy than other data sets. However, they are also just 55.09% and 53.92% in first level assessment and 46.55% and 46.23% in the second level accuracy assessment. The best producer's accuracies of the three main land cover classes, e.g. alpine grassland, barren land and desert land in the QP were 46.19% in GLC 2000, 39.20% in MCD12Q1, and 84.44% in the IGBPDIS. The user's accuracy of the three first level land cover classes were less than 50%. In addition, the accuracy of the CCI-LC data was 92.8%, with omission error at 19.90% in the snow and ice cover. After analysis, we found that the discrepancy of classification system and the typical plateau environment in the QP are the main factors that result in a high level of inaccuracy of the land cover datasets.
A total of 19 soil temperature stations and three automatic weather stations in Gaize and Ritu counties, Tibet within the core region of Northern Tibetan Plateau, have been established to measure soil temperature at three soil depths (1 cm, 10 cm and 20 cm) with their elevations varying from 4515 to 5172 m. The station-averaged soil temperature data at hourly to monthly scale are used to analyse the characteristics of soil temperature and thaw-freezing processes during the period from September, 2013 to October, 2014. Major findings are as follows: The ranges of daily soil temperature at 1 cm, 10 cm and 20 cm depths are -16.27 to 17.18 ℃, -14.35 to 15.75 ℃, and -13.49 to 14.70 ℃, respectively during the study period. Soil temperature varied in a slower amplitude with the increase of depths. The difference of 22 stations may have relationship with elevation and latitude, and the spatial variability is less than 12.82 ℃. The temperature continuous rising process is faster than continuous cooling process at daily scale. For all the three depths of soil temperature, the coldest month is January with an average temperature of -12.69 ℃, and the warmest month is July with an average temperature of 13.15 ℃. The annual range of daily mean temperature is about 30 ℃. The soil temperature has a strong coefficient of variation (CV) values during thaw phase and freezing phase, especially at 1 cm soil depth. And the CV values during the thaw phase are higher than those during the freezing phase. In view of the correlation analysis between air temperature and soil temperature at three soil depths, the soil temperature at 1 cm depth is strongly correlated with air temperature at monthly scale with the correlation coefficient being r = 0.99. The results will provide reliable data for the basic research of the Tibetan Plateau. And it will also provide a scientific basis for regional thaw phase and freezing phase, soil heat transfer and hydrological and thermal process.
The Changtang Plateau is a typical alpine area in Asia, as well as one of the regions with fewer available data. Exploring soil properties and their data is very helpful to grasp the soil forming characteristics in cold environments. Twenty two soil samples, covering the three layers: 0-5 cm, 5-10 cm, 10-20 cm, from 8 sample points, were collected from Charinazu piedmont to the lakeside near Chabu village in Gerze County, Tibet Autonomous Region in the central area of Changtang plateau. The soil particle composition, pH, organic matter, total nitrogen, total phosphorus, total potassium, alkali solution nitrogen, available phosphorus, available potassium, and soil calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), and zinc (Zn) were measured. Soil properties and their spatial characteristics were discussed. The results indicated: (1) the soil pH is 8.9; Compared to the national background values of frigid calcic soils, the soil organic matter, total phosphorus, total potassium and alkali solution nitrogen content are lower; Ca and Mg content are higher; and Na, K, Fe, Mn, Pb, Cd, Cr, Cu, and Zn contents are lower than the corresponding background values. (2) Spatial characteristics: the soil pH value was lower near the lakeside and piedmont, and it was higher in the middle section; From the lakeside to the foothills, the gravel (with more than 2 mm diameter) content showed a reducing trend, but the average particle size of fine soil (less than 2 mm) increased gradually; Soil organic matter, total nitrogen and alkali solution nitrogen content increased; Available potassium and available phosphorus decreased, but the total phosphorus content fluctuated greatly with no obvious trend. Soil Ca and Mg content showed a declining trend; Na increased slightly; Fe fluctuated; and Pb, Cd, Cr, Cu, Zn, and Mn content also increased slightly with large fluctuations. (3) Soil pH, total phosphorus, available phosphorus, available potassium, alkali solution nitrogen, and Cd had poor relationships to the values of other soil indicators. The correlation coefficient between soil organic matter and total nitrogen content was very high with a ratio of 5: 1, and they both had close correlations to most major and trace soil elements. There was a significantly positive correlation between soil Ca and Mg, and a significantly negative correlation to the values of other soil indicators. In addition, there was a significantly positive correlation between soil K, Na, and other metal element content except for Ca and Mg.
Soil moisture is a key parameter of the ecosystem. Real-time and effective monitoring of soil moisture helps to enhance our understanding of regional climate and environmental change. MOD11A2 and MOD13A2 of MODIS synthetic products in DOY (Day of Year) 177-225 between 2000 and 2014 was used to obtain the Land Surface Temperature and Normalized Difference Vegetation Index, and the status of soil moisture on the Qiangtang Plateau covering the summer from 2000 to 2014 was evaluated based on the method of Temperature Vegetation Dryness Index (TVDI). The spatial distribution of soil moisture in the summer of 2014 was analyzed as an example, and the dynamic changes of soil moisture during 2000-2014 were further discussed. The results show that: (1) The soil moisture of the Qiangtang Plateau in 2014 was generally humid in the southeastern part, while it was arid in the northwestern part. Soil moisture gradually reduced from east to west, dry and wet conditions were found alternately between south and north. The percentages of areas of dry soil, partially dry soil, normal humidity soil, partially wet soil, and wet soil were 3.84%, 27.17%, 37.64%, 29.63%, and 1.72%, respectively in 2014. (2) In July and August from 2000 to 2014, soil moisture in the northern and central parts of the plateau showed a significant trend of getting dry, while that in the southern part showed a trend of getting wet with little significance. The proportion of area of dry soil and wet soil in the study area was the smallest and had little fluctuation from 2000 to 2014, while that of partially dry soil, normal humidity soil, partially wet soil had different fluctuations. (3) Precipitation was an important factor affecting TVDI, and had the certain hysteresis, while the impact of temperature was relatively small.
ECH2O EC-5 soil moisture sensor can effectively monitor the soil moisture content, and it can reveal the soil moisture dynamic change under different rainfall events. However the main soil type has high gravel content on Tibetan plateau, and there is a large temperature disparity between day and night, especially the freezing and thawing phenomenon which frequently occurs during spring and autumn. This paper discusses the property of the EC-5 soil moisture sensor's measuring data of soil water content, and the soil sample are taken from the field observation sites in the Qiangtang plateau western Tibetan Plateau of China.
The results show that all samples have good imitative effects: (1) According to the fitted line, the measured data which had already been corrected could efficiently reflect the practical soil moisture content most R2 of the fitting were over 0.97, the fitting curve of measured data after calibration and the real value is very close to the standard curve; (2) Comprehensive calibration results of different soil depth, there are some differences of regression straight line and the ideal straight line (Y = X), when the water content is quite low the water content value after calibration is higher than the real value, when the water content is quite high the water content value after calibration is lower than the real value. When the water content between 0. 06~0.12 cm3/cm3, the calibration result is more reliable. (3)The existing calibration model can reflect the overall situation of the water content changes, but may cause overestimate or underestimate the true value of the deviation.
The Qinghai-Tibet Railway is constructed in an ecologically fragile area, and thus, the railway construction will impact the ecosystem around inevitably. To evaluate the effects of railway objectively, we carried out a study on the basis of 212 Landsat TM/ETM+ images captured in 1995-2014 during the peak period of vegetation growth along the railway and within a 10-km range of it. The Fmask method and the spatial and temporal adaptive reflectance fusion model (STARFM) were used to remove the cloud, shadow, and gap in those images to acquire clear 30-m NDVI images. Then, the linear regression and sequential T test of regime shifts (STARS) were used to analyze the spatial-temporal change, regime shift, and eco-resilience characteristics of the NDVI in the study area. Results show that: (1) the NDVI of the study area grew slightly in 20 years, similar to the NDVI growth in the whole Tibetan Plateau. The NDVI along the railway is higher in the north than that in the south. The NDVI in the northern part changes slightly, and the area of decline is concentrated in Naqu-Damxung; (2) The railway construction exerts no apparent effects on the ecological system. Both sides of the railway within the range of 1 km are influenced by the railway construction. Most significant damages to vegetation cover resulted by the railway and ancillary facilities construction are within the range of 100 m along the railway. (3) Regime shift and eco-resilience focused in the city and the surrounding valley and pastoral areas caused most dramatic changes in the region. The detection results of different ecosystem types of eco-resilience show that the eco-resilience order is as follows: bare > desert > alpine > grassland > meadow > shrub > wetland > farmland. The wetland ecosystem is the most vulnerable environment and the main type of ecosystem protection. In addition, restoring vegetation is most difficult in the desert ecosystem and bare ground.
Based on the panel data of 45 Aviation Economic Development Zones (AEDZs) in China from 2001 to 2014, this paper empirically examines the relationship between AEDZ and the hinterland development at the national scope and by three typologies, i.e. central, pillar, and start-up types of AEDZs, through applying the Granger causality test and dynamic spatial measurement. The results show that: (1) regional economic development of the hinterland plays a decisive role in the increase of passenger and cargo throughput in the airport, while AEDZ imposes limited impact on the economic growth of hinterland, with the influence mainly concentrated on the passenger throughput. (2) Different levels of AEDZs exert different impacts on the development of hinterland regional economy: i) the central type of AEDZs, represented by Beijing and other first-tier cities, has the greatest impact with a steady growth trend; ii) the pillar type of AEDZs, represented by the second-tier provincial capital cities such as Zhengzhou, has relatively weak impact, indicating an accelerating growth trend; iii) the start-up type of AEDZs represented by the third-tier cities such as Lanzhou has little impact, with a relatively slow growth rate. Based on the analysis, the following suggestions and recommendations can be made: (1) aligned with the well positioning of the hinterland and the AEDZ development stage, identify the local competitive industries with rational planning; (2) improve the soft environment of AEDZs to develop the modern industrial system; (3) promote the integration of AEDZs and hinterland areas to push the continuous development of aerotropolis; (4) innovate institutional system to boost vitality of the customized development of AEDZs.
With the rapid reconstruction of global industrial spatial organization, Logistics Supply Chain (LSC) is becoming a new topic of transportation geography. Understanding the spatio-temporal evolution of the LSC and its influencing factors can help policy makers more efficiently guide the regional spatial reorganization of the logistics in an integrative context. Based on the data of the relational international freight forwarding enterprises in 2005, 2010 and 2015, this paper explores the evolutionary process, the formed pattern and the influencing factors of LSC in the Yangtze River Delta (YRD) on both the regional and provincial scales, by mainly using the complex network research method. The result implies that the LSC of YRD presents radial pattern characteristics, taking Shanghai as the core. Suzhou, Nantong, Jiaxing and other nodes surrounding Shanghai have developed rapidly. The degree of LSC integration in YRD is strengthening, while the connection between Zhejiang and Jiangsu provinces grows slowly, with obvious disparities within the provinces. The organization-control capability of the nodes are remarkably different in the regional and provincial scales. Nanjing has always been the core node of LSC in Jiangsu. The core node of Zhejiang is composed of “dual-core structure” of Ningbo and Hangzhou, controlling regional and provincial elements respectively. The stability of LSC is getting better in the two scales, with the efficiency of LSC in the regional scale increasing, but the efficiency of LSC in provincial scales is obviously different. Based on the analysis, this paper presents the five-stage development model of LSC evolution, and currently the LSC of YRD is in the fourth development stage. The main influencing factors include the regional economic development and city location, macro policies and marketization, logistics integration and logistics resources coordination, global production network and logistics enterprise organization. Finally, the paper puts forward countermeasures and suggestions for the development of LSC in YRD as follows: (1) Shanghai should strengthen connections with neighboring Suzhou, Nantong, Jiaxing and other nodes, jointly building an international supply chain center; (2) give full play to the advantageous functions of Ningbo and Hangzhou in LSC respectively as the dual cores by better consolidation and coordination; (3) fully enhance the cooperation between Yangzhou and Taizhou, so as to strengthen the radiation of Sunan (Southern Jiangsu) towards Subei (Northern Jiangsu).
Improving grain production efficiency is an important way to relieve the pressure from cultivated land loss and to ensure grain security. In this paper, we assessed the county-level grain production efficiency with SFA in the North China Plain during 2000-2015. Furthermore, the spatial distribution characteristics of county-level grain production efficiencies were analyzed based on global and local spatial autocorrelation analysis. Finally, we discussed the impact of land use change on grain production efficiency. The main results are as follows: (1) The proportion of counties with grain production efficiency above 0.8 is relatively high, and the average efficiency in 2000, 2005, 2010 and 2015 were 0.7544, 0.7730, 0.7525 and 0.7518 respectively, which indicates that there is still some scope for improvement in grain production efficiency; (2) Although the global spatial autocorrelation in county-level efficiency is weak, the local spatial autocorrelation in county-level efficiency shows obvious regional differentiation; (3) The input factors, such as rural population, total power of agricultural machinery, the amount of applied chemical fertilizer, the amount of used pesticides, the rural per capita net income and the sown area of grain, have positive effects on the grain production efficiency, however, rural electricity consumption has negative effects; (4) The land use diversity index, cultivated land proportion, cultivated land patch density, land use degree and multiple cropping index were selected to construct the panel data, based on which, the Tobit regression model estimations reveal the effect of land use change on grain production efficiency. The patch density, land use degree and land use diversity index have significant negative effects on grain production efficiency, while multiple cropping index has a significant positive effect on grain production efficiency. Several feasible suggestions were concluded from this study. First, in order to perfect the farmland circulation and scale operation, it is mecessary to strictly enforce land planning, strengthen the protection of basic farmland, avoid the fragment caused by the extensive expansion of rural settlements and urban built-up land. Second, it is important to maintain a certain quantity of cultivated land to guarantee large scale grain production. Third, the agricultural policy must be adjusted to maintain its vitality for grain production, reinforce farmland infrastructure, and reduce the risk of grain production. Fourth, it is necessary to continue financial, political and scientific supports in regions with a high multiple crop index.
The optimization of regional industrial structure is a classic topic for human-economic geography, also a heated issue faced in the context of Chinese new-type urbanization, which plays a key role for the Chinese regional balanced development. In this paper, with Beijing-Tianjin-Hebei as the study area, using multi regional input-output method, we constructed a linear programming model to systematically analyze the overall optimal industrial structure and development path in the Beijing-Tianjin-Hebei region under three constraints of energy-environment-employment, which included the multi regional flow factors. The results showed that (1) the results of the energy and environment constraint scenarios for Tianjin and Hebei share similar trends, and that energy consumptions in Tianjin city and Hebei province will cost too much. (2) In the scenario of employment constraint, Beijing should reduce the proportion of heavy industry; develop light industry, information industry, as well as financial service industry. Tianjin should focus mainly on modern industries, while Hebei province should mainly combine the development of modern industry and traditional service industry. (3) The industrial structure adjustment of the three case studies in the environmental restraint scenario is mainly turning to reduce the proportion of industries characterized by high pollution and high emissions. (4) Considering the above constraints of all scenarios, Beijing, Tianjin and Hebei should cooperate on the systematical planning of industrial development, taking advantages of their resouces, human capitals, and developmental bases respectively. Beijing should put the tertiary industry as the leading economic pillar, focusing mainly on the development of high-end service industry, high-tech industry, as well as transferring the primary and secondary industries to Tianjin and Hebei. Tianjin should balance the manufacturing and service industries, and seek its own advantage industry. Hebei should upgrade the high pollution and high energy consumption industry, develop service industries and undertake the transferring of industries from Beijing and Tianjin.
Based on the theories of 'central place' and 'flow space', this paper used the urban flow intensity model and the improved gravity model to analyze urban economic ties in Shandong province from the perspective of urban network development from the city center. We built an abstract city association based on elements flow by combining geographic space of enterprise groups in Shandong province. We compared the evolution of a polycentric network from the two types of urban association patterns in Shandong province from 2000 to 2009 to determine the trends in network characteristics in two types of cities in four regions. We confirmed that the study of city relationships based on flow space theory avoided an over reliance on space-distance concepts. We also found that the relative stability of urban attributes during the study period based on central place theory effectively could not reflect the dynamic processes of city connection structures and direction. Some conclusions can be drawn as follows. (1) The urban structure correlations in Shandong province showed the evolution of a multi-center pattern from the dimensions of 'point-line-network', and a trend of urban network association equilibrium was emerging. (2) City network connections became more closely related. The structure of the association was mature, which provided additional possibilities for the development of the regional polycentric network. A close and efficient multi-core ring network was formed in the urban area, which provided a more extensive and convenient channel for the circulation of regional elements. (3) In the eastern and central parts of Shandong, cities' concentric internal economic ties tended to decline. However, in the southern and northwestern parts of the province, cities' close internal economic interactions were maintained with the central city and there was strong development of their economy. (4) The inward-focus characteristics of enterprise associations in eastern Shandong were obvious, but the eastern part had weaker cooperation with the central and western parts.
The Paris Agreement established an institutional framework of the global response to climate change after 2020, which has greatly promoted the global cooperation in tackling climate change. Global climate governance has been more and more recognized by state and government. Chinese government has pledged to reach CO2 emissions peak by 2030, and strives to reach the peak as soon as possible, and actively participates in the global climate governance. As the same time, the central and local governments have implemented air pollution control policies in order to solve the increasingly serious air pollution in China. Due to the homology of carbon dioxide emissions and air pollutants, for instance, fossil fuel combustion, the government can adopt collaborative governance policy to reduce carbon dioxide emissions and control air pollution simultaneously. Collaborative governance can avoid inconsistencies in policy making and improve the effectiveness of policy implementation. In the background of world economy integration, a country's climate governance policy will have an impact on the rest of the world economy, thereby affecting countries' investment for climate change mitigation, and ultimately affect the global cumulative welfare. In this paper, based on EMRICES model, we simulated the effects of carbon tax and sulfur tax of China on the world economy, and analyzed the change of carbon peak value after China's participation in global governance of climate. It was found that, under the baseline scenario, China's carbon emissions peak is 3695.30 Mt C, which will appear in 2033. Under China's carbon tax scenario, when other economies do not levy carbon tax, China's carbon emissions peak is 3480.30 Mt C, which will appear in 2032. Under China's sulfur tax scenario, when other economies do not levy sulfur tax, China's carbon emissions peak is 3307. 90 Mt C, which will appear in 2031. When China levies tax carbon and sulfur tax simultaneously, and other economies do not levy tax, China's carbon emissions peak is 3125.10 Mt C, will appear in 2030, three years earlier than the baseline scenario, which reflects that China can complete the target of reaching carbon peak around 2030, but China may suffer from greater economic losses.
For the growing challenge of international carbon emission reduction, to control the investments of the energy-intensive industries to accelerate the industrial structure upgrading is an important way to achieve carbon reduction targets of China. In this study, a climatic-economic integrated assessment model named CIECIA was applied. CIECIA mainly comprises a multi-country-sector general equilibrium model as its economic core and a global carbon cycle system. A stochastic technological shock mode driven by R&D is also adopted in this model to depict the endogenous mechanism of technological progress. Based on this model, the carbon reductions of countries by the natural industrial evolution were predicted, and the carbon reduction effects of the industrial restructuring by investment control measures of China and their economic impacts on different countries were studied, as well as the carbon governance of investment balance distributions among sectors. The results show that despite significant decline of the GDP shares of energy-intensive sectors in the industrial structure, the carbon reductions of China by the natural industrial evolution in future are still very limited. In the baseline scenario, the cumulative carbon reduction contributed by industrial structure change of China between 2007 and 2050 is only 17%. Investment controls for energy-intensive sectors in China have significant effects on carbon reductions, and also accelerate the industrial transformation and upgrading. In the three scenarios, the GDP shares of energy-intensive sectors decline sharply, leading to significant carbon emission reductions. Under Scenario 1, the carbon emission peak of China occurs in 2029, and the carbon emissions of China directly decrease from 2016 in scenarios 2 and 3. However, the investment control is negative to China's economic development, and the outflow of investments benefit other countries in turn, especially Russia, which takes energy-intensive sectors as its leading industries. In Scenario 3, the cumulative utility loss of China is up to more than 3%, whereas the increase of Russia is around 1.5%. Using the investment balance to invest tertiary industry and R&D to speed up the technological progress is an effective strategy for China to keep steady economic growth, reduce economic losses of carbon reductions, and achieve its carbon reduction targets under investment control. In Scenario 6, China avoids its economic loss under the investment control measure, and advances its carbon peak to 2024.
：Light use efficiency (LUE) is a critical parameter for remote sensing estimation of ecosystem productivity. Therefore, accurate estimates of spatio-temporal variation of LUE is essentially required. Photochemical reflectance index (PRI) has been widely accepted to hold the potential to track the LUE variations. Here we combined spectral and eddy covariance observations in a subtropical mixed forest to investigate the ability of PRI to estimate LUE at a half-hourly time-scale in different seasons. The forest is located at Dinghu mountain forest ecological experiment station in Zhaoqing of Guangdong province and the observations ranged from April 2014 to March 2015. The results showed that: (1) LUE was significantly correlated with PRI but the correlation strength was different in different seasons; The correlation was the strongest in winter (R2=0.40, P<0.01) and the weakest in summer (R2=0.04, P<0.01). (2) The standardized PRI (?PRI), which removes noises from canopy and soil background, did not well capture the dynamics of LUE. (3) Photosynthetic active radiation (PAR) had the largest influence on the relationship between LUE and PRI among various climatic variables. Our analysis featured the temporal limitation of PRI in estimating LUE in subtropical forests and similar efforts are needed to quantify PRI ability to estimate LUE in other ecosystem types.
Land surface temperature (LST) is an important parameter driving dynamics of biogeophysical processes on Earth surface. It has significant impacts on the distribution of permafrost and the change of the active layer depth. Conventional acquisition of LST data usually comes from weather station monitoring in a small and discrete scope. NASA's MOD11 A1 surface temperature product can provide a wide range of surface temperature data. In winter, however, the confusion of clouds and snow often leads to a large amount of data missing in the MOD11 A1 products in the permafrost region. In this paper, an improved split-window algorithm was selected to re-build the LST products in Northeast China, one of the major permafrost regions in China. Within the common land covers extracted from remote sensing classification results, such as vegetation, bare soil, water and snow. We extracted LST in each cover type from four cloud-free MODIS 1B satellite images in 2006. Both our results and the original MOD11 A1 products were statistically compared with ground measurements at weather stations. The average difference between our results and measurements at meteorological stations was small, reaching a room-mean-square error (RMSE) of 1.24 ℃. In comparison with the original MOD11 A1 products, our results took advantage of land covers and revealed better distributions of land surface temperature in snow area, and had a high consistency with the surface temperature products. This study provides a good approach to filling in the gaps of current land surface temperature products due to confusion caused by the cloud and snow.
The Lunden Bay, an ancient lagoon, is located near the western coast of the Jutland Peninsula along the Southern North Sea. A non-disturbance core LN in the length of 719 cm was obtained with the gravity core sampler. The upper part buried less than 53 cm was observed and 7 sediment samples were taken in the field. Based on the core analyses on sedimentary structure, grain size, loss on ignition (LOI) and EMMA, it is clear that the core is mainly composed of fluvial deposits (EM1), tidal deposits (EM2) and wave deposits/storm deposits (EM3). The main dynamic processes changed from wave/storm dominated in the early period to tide dominated afterwards. When the river influence became stronger gradually, the effect of marine processes got weaker, and disappeared finally. Combined with sedimentary structure and LOI data, EM3 revealed several storm deposit layers effectively. With the time scale determined by AMS14C dates and the background of the regional eustatic sea level change, it could be reconstructed for the evolution processes of the coast along the Lunden Bay since 6050 cal. a BP. Controlled by the river-sea interactions, the embayment coast, submarine sand bar-lagoon, semi-enclosed barrier-lagoon and enclosed barrier-lagoon have been formed in the Lunden Bay successively, which showed the typical processes for the changes of the regressive barrier-lagoon coast. Finally, the ancient lagoon was filled and developed into coastal wetland in 5150 cal. a BP.
