The development zone is an important engine of regional economic development. Optimizing the spatial layout and industrial structure of the development zone is of great practical significance to the coordinated and sustainable development of the Yangtze River Economic belt. This study uses statistical analysis and geospatial analysis to explore the spatial pattern evolution characteristics of development zones above the provincial level and their industries in the Yangtze River Economic Belt. The main influencing factors of spatial distribution of technology intensive industries are analyzed by multiple linear regression method. The results show that the spatial layout of the Development zone of the Yangtze River Economic Belt changed from a scattered “multi-point” structure to a “T-shaped” structure from 1992 to 2012, and stabilized into a “grid” structure from 2012 to 2017.The spatial distribution of the development zone is stable in the direction of “southwest to northeast”, and the migration characteristic of the distribution center is “Northeast to due West to northeast”. The migration range from 2002 to 2012 is the largest, and from 2012 to 2017 is the smallest. The geographical space shows an overall trend of expansion. The spatial correlation of the development zone fluctuates on the whole, and the high-high agglomeration area first increases and then decreases. The technology-intensive industries in the development zone have absolute advantages, among which the equipment manufacturing industry is the main industry, and the electronic communication industry presents obvious spatial distribution characteristics of “one core and multiple poles”. The other four industries in the six industries are consistent with the spatial distribution characteristics of the development zone. Among the three types of industries, the aggregate shows the agglomeration characteristic of fluctuation, and only the labor-intensive industry in 1992 shows the dispersion characteristic. The urban economic environment has a positive relationship with the industrial development of the Development Zone, while there is a certain reverse relationship between the government’s introduction of foreign investment, and policy factors play an important role in the whole development process.

Regional diversification development plays an important role in enhancing productivity, promoting employment and stabilizing the economy. Regional industrial change is largely understood by evolutionary economic geographers as an endogenous phenomenon so far and the role of external resources in regional diversification development has been neglected. Actually trans-regional cooperation innovation is one of the important ways to obtain external knowledge in the region. Although many studies have confirmed the positive impact of extraregional knowledge inputs on innovation, the impact of these innovations on regional industrial continuity and change is rarely mentioned. Using the invention patent data of 41 cities from 2000 to 2017, this study measures the diversification level and cooperative innovation in the Yangtze River Delta which has a significant regional economic integration characteristics, and empirically tests the role of intra-regional and inter-regional cooperative innovation in the process of regional diversification. The results show that: (1) The level of related and unrelated variety of cities in Yangtze River Delta generally increases gradually and tends to be stable, With the development of economy, the diversity of cities is gradually narrowing; (2) Cooperation innovation is an important carrier of knowledge flow. Out-of-area cooperation patents are dominated in the Yangtze River Delta region, that is the proportion of participants in the city of cooperation patents is generally smaller than that of participants in other cities, while participants outside the city are mainly located in the Yangtze River Delta region. Cooperative innovation contributes to the development of related variety in Yangtze River Delta, but has no significant impact on unrelated variety; (3) The number of participating teams in cooperative innovation has no significant relationship with regional related and unrelated variety; (4) The higher the proportion of inter-regional cooperation in cooperative innovation, the more related and unrelated variety can be promoted. That is innovation in non-local knowledge source activities can promote regional related and unrelated variety. Therefore, in the process of promoting the diversification of regional industries, attention should be paid to strengthening the cooperation between regions and guide the development of regional industries with the help of external forces.

Urban agglomeration in the middle Yangtze river plays an increasingly prominent role in national development, the pattern of networked urban system has been gradually developed and improved. In light of the effects of various factors and time dimension, this study aims to investigate the temporal changes of network connectivity and degree centrality of urban agglomeration in the middle reach of Yangtze river between 2001 and 2016, employing Krugman index and AHP method (Analytic hierarchy process) to determine the city comprehensive “quality” based on economic, and social factors and to measure city link costs based on geometry, highway and railway elements. The findings highlighted that with the economic and social development and the construction of urban links, urban network system in the middle Yangtze river have been gradually formed and deepened, in which Wuhan-Changsha-Nanchang identified as the network center. With the increasing influence of Wuhan-Changsha city clusters, more and more cities were attracted to join the urban network, showing balanced development. The findings also indicated that: (1) regional network characteristics are becoming more and more prominent, and depth and intensity of connections is gradually emerging. It is very important to build a large channel to improve regional connections and promote infrastructure interconnection. (2) Central cities have been significantly strengthened, and secondary layer of cities need to be improved. The formation of a multi-center, hierarchical, and deep-level urban system also requires strengthening the cooperation of the top layer and the development of the bottom layer. (3) The network and hierarchy of city clusters in the middle Yangtze River are improving. An innovative, coordinated, green, open, and shared city system requires the guidance of central cities, but also requires more cities to actively deepen, participate, and promote.

The metropolitan area is a new form of promoting new urbanization, and it is also the basic unit to realize the regional economic development. This study clarifies the key role of the comprehensive competitiveness of cities and towns, the intensity of spatial connection and the inter-regional flow of elements in the core system of the metropolitan area in the process of regional spatial development. Through the comprehensive comparison of the metropolitan area, in order to optimize the new mechanism of regional coordinated development, To meet the new requirements of improving quality and increasing efficiency in metropolitan area to provide new reference. Combined with the comprehensive competitiveness model of cities and towns, the improved spatial relationship model and the factor flow intensity model, this paper analyzes the Changsha metropolitan area and Wuhan metropolitan area in the middle reaches of the Yangtze River in 2016. The comparative differences of Nanchang metropolitan area in three dimensions: urban comprehensive competitiveness, spatial structure and urban function division system. The conclusions are as follows: (1) the research on comprehensive competitiveness of each metropolitan area shows that the comprehensive competitiveness of each metropolitan area has significant spatial disequilibrium distribution characteristics, Changsha metropolitan area is developed in the east-west axis zone, the difference between the center and the peripheral towns of Wuhan metropolitan area is significant, and the Nanchang metropolitan area lacks a high value development center with strong leading ability; (2) Changsha metropolitan area forms the circular spatial structure form from the center to the periphery, Wuhan metropolitan area forms the multi-center group spatial structure form, Nanchang metropolitan area presents the Changjiu “double star” spatial structure form. The urban circle has a significant difference in the directivity and spatial structure of the central city, and is associated with the factors such as the urban expansion policy, the urban development gap and the network of the modern transportation line. With the perfect function division system of element flow, the matching degree between traffic flow and economic flow in Wuhan city circle is poor, and the urban circle of Nanchang lacks perfect economic flow and traffic flow function division system; (4) In the discussion and analysis, the city circle points out the perfect resource sharing and the element transfer channel, the construction of the urban economic cooperation mechanism, the promotion of the development of the modern transportation network system, etc. Development ideas.

The purpose of the study is to exploring impact mechanism of new-type urbanization on industrial land use efficiency, based on industrial enterprises in Jiangsu Province. Methods employed include spatial autocorrelation analysis and spatial econometric model. Results showed that:（1）The industrial land efficiency of the whole province was a gradually decreasing spatial structure from south to north. The land efficiency of manufacturing and electric power enterprises was similar to that of the whole sample enterprises, and the agglomeration evolution trend was in same step.（2）Population, economy, land and social urbanization showed positive effects on mining, manufacturing and the whole sample. While for the power industry, only social urbanization showed positive effects. In conclusion, the new-type urbanization has a significant positive impact on promoting industrial land use efficiency. It is necessary to further optimize the spatial layout and process of urbanization, promote the coordinated development of enterprise types among regions, and therefore the positive spillover effect of urbanization will be formed.

There exists two difficult issues in study of the trend and driving mechanism of urban expansion: (1) Maxed pixels of traditional landscape data reduce the accuracy of urban expansion trend research. (2) Collinearity of the driving factors affects the reliability of driving mechanism. To fix these problems, taking Nanjing City for example, the impervious surface was used to conduct weighted average barycenter analysis, linear direction mean analysis and standard deviation elliptic analysis to study the urban growth characteristics. Driving mechanism of urban growth was studied through combination analysis qualitatively and quantitatively (Partial least squares regression，PLS). Results showed that imperious surface in Nanjing showed multicentric and inconsonant expansion. Gravity center transfer distance of impervious surface increased over the three periods (2000 to 2005, 2005 to 2010, 2010 to 2017), which annual gravity center transfer distances were 303, 379 and 611m respectively. In general, the gravity center transferred 2 564 m to the direction that 259.12 degrees to the north clockwise. The exterior morphological characteristics of urban growth had obvious directivity, which the oblateness of the standard deviation elliptic of the impervious surface were all larger than 2.23 in 2000, 2005, 2010 and 2017. The external spatial characteristics of the administrative region, distribution of rivers and nature reserves, and the land use plan were the main factors that constrain and limit the direction of urban expansion. The number of employees in the secondary industry, population density, fixed assets investment in the tertiary industry, regional GDP, and per capita disposable income in urban and rural areas were the main factors that influenced the scale of urban expansion.

Under the background of industrial transfer and transformation and upgrading, this paper takes 21 major manufacturing industries’ industrial sales value and employees in 2006, 2011 and 2016 as research data, and uses dynamic agglomeration index, industrial gradient coefficient and improved Shift Share Model (SSM) to explore China’s manufacturing transfer and its structural evolution. The study found that: (1) During the research period, the main body of manufacturing industry transfer is labor-intensive and part of technology-intensive manufacturing industry, and the direction of transfer is from the east to the central and western regions. However, from 2011 to 2016, chemical raw materials, medicine and other manufacturing industries in Jiangsu, Zhejiang and other places have shown a strong spatial agglomeration trend；(2) The marginal industrial transfer and technology grants in the food and beverage manufacturing industry and metal smelting industry in the eastern region not only optimized their industrial organization, but also promoted the scale and concentration of manufacturing in the central and western regions, while Liaoning, Jilin, Heilongjiang and other places must guard against the loss of industry and guide the development of manufacturing industry; (3) During the study period, the structural effect index w of manufacturing industry in eastern regions such as Shanghai and Guangdong is greater than 1, and the average structural deviation component p is larger, indicating that its manufacturing industry contains a relatively large proportion of sunrise industries and its industrial structure is better. Hunan, Guizhou and other central and western regions of the manufacturing industry competition effect index U is greater than 1, and the average competitive effect is larger, indicating that its manufacturing industry is developing faster and more competitive. The research helps to clarify the new characteristics of China’s manufacturing transfer and its structural evolution in the context of industrial transfer and transformation and upgrading since the financial crisis, and provide reference for China’s high-quality economic and industrial development.

Water shortage has seriously affected human survival and China’s sustainable development. Analysis of water resources in various regions is the key for addressing China’s water resources problems. This study used multiregional input-output tables for 2007 and 2012 ,calculated the water footprint transfer amount of China’s 30 provinces, municipalities, and autonomous regions (not including Tibet, Hong Kong, Macao and Taiwan), and the source-sink system theory are used to analyze the flow pattern of the water resource network among regions within China. Finally, an ecological network analysis model is constructed to deeply analyze the inter-regional water footprint control, dependence, and the Finn cycle index and system robustness of water resource network. The results show that: (1) The regions with large water footprint output are Heilongjiang and Xinjiang, and the regions with large water footprint input are mostly economically large areas such as Jiangsu, Zhejiang, Guangdong and Shandong. （2)In the source system, eight areas such as Heilongjiang are important sources of water footprint. The water footprint extroversion coefficient of most source provinces has a decreasing trend, each region has a strong competitive relationship with water footprint consumption. In the sink system, the regions with large convergence coefficient are Jiangsu, Zhejiang, Shandong, and Guangdong; the dependence coefficient of Beijing and Tianjin are large, and the dependence coefficient of most regions shows a decreasing trend. (3) Heilongjiang and Xinjiang have a strong control relationship with other regions, while Beijing and Tianjin have a strong dependence relationship with other regions. 4)The circularity of water resources network is poor. Only Jiangsu and Guangdong had higher contributions in 2007 and 2012; In addition, the system robustness analysis showed that the water resources network is less efficient and more redundant. Water footprint transfer and spatial pattern analysis among regions within China can provide theoretical basis for addressing water resources problems, and provide theoretical support for rational utilization of regional and industrial water resources.

The reservoirs in the Upper Yangtze River are refilled in August-October. This period is in the late rainy season. If a reservoir cannot be refilled at a certain water level before the end of the rainy season when precipitation is concentrated, it will seriously affect the benefits of the reservoir. To optimize the existing reservoir impoundment operation policies, this paper selects the Rainy And Dry Season (RADS) data set of Texas A&M University, and analyzes the characteristics of the rainy season in the Upper Yangtze River. The results show that the characteristics of rainy season for China and the Upper Yangtze River revealed by RADS are similar with those from the existing researches. Thus the data set is applicable in the study area. The demise dates of rainy season in the Wu River Basin fluctuate obviously calling for the medium- and long-term hydrological and meteorological forecast of the Wu River Basin for the warning of the earlier end of the rainy season. For the regulated September 1st and October 1st of reservoirs initial impoundment time in Wu and Min-Dadu Rivers, there were situations that the rainy season ended earlier during 1961-2007. Namely, for reservoirs in the two basins, considering flood prevention tasks and forecasted streamflow conditions, it is necessary to consider further advances the initial impoundment time.

Under the influences of climate change and human activities, the ecological environment of Honghu wetland has undergone profound changes since the 1950s. Based on the monitoring results of many years, the current situation of plant diversity and vegetation in Honghu wetland was analyzed. It was considered that the overdevelopment of the littoral zone, the barrier of rivers and lakes, the frequent occurrence of drought and flood, the eutrophication of water bodies and the flood of invasive species may be the prominent problems affecting the plant diversity protection of Honghu wetland. Therefore, some countermeasures and suggestions were put forward, such as restoring the lakeshore wetland, implementing water system connectivity, optimizing water resources regulation, improving water quality and actively controlling invasive species. At the same time, it is believed that the natural hydrological relationship of the rivers and lakes in the middle and lower reaches of the Yangtze River is an important basis for maintaining the regional aquatic plant diversity. It is necessary to pay attention to the restoration of river and lake wetlands within the basin, improve the plant diversity of river and lake wetlands, restore the connection of water system in natural hydrological process, and form a river and lake network for the protection of diversity, so as to lay a foundation for the maintenance of plant diversity in the basin.

Yilong lake is one of the nine plateau lakes in Yunnan Province, China. It is a typical plateau lake on the node of evolution from plant-type lake to algae-type lake. For historical reasons, the water environment conditions in Yilong lake are completely different between the East and West areas, which is a good representative plant-type and algae-type Lake in Yunnan Plateau. There have been few research results on submerged plants in Yilong lake since 1980. To address this issue, in this study, the water quality and submerged plants of Yilong Lake are investigated for one year period, the distribution of submerged plants and their relationship with water environment factors are also studied, with aims to leave precious historical data for the study of submerged plants in Yilong lake and explore the distribution and impact factors of submerged plants, provide data and technical support for submerged plant restoration. Furthermore, results indicate the spatial distributions of submerged plants are significantly different between the East and West Lake areas with the dominant species of Najas minor, Utricularia vulgaris and Hydrilla verticillata in the West Lake area while potamogeton pectinatus and Myriophyllum verticillatum in the East Lake area, the coverage, biomass and species richness of submerged plants in the West Lake area are significantly higher than that in the East Lake area. Meanwhile, the results of correlation analysis show that water depth, transparency and dissolved oxygen are the main environmental factors affecting the distribution of submerged plants in Yilong lake, while total nitrogen, total phosphorus, ammonia nitrogen and pH are the secondary factors. Different restoration strategies should be adopted and different submerged plant species should be selected for restoration in different lake areas.

Studying the water conservation function of artificial forests in the basin plain lake area of Yangtze river is great significance to guide the afforestation and ecological restoration along the Yangtze riverbank. In this paper, the water conservation capacity of litter layer and topsoil of 7 different forest types were analyzed and compared by the soaking method based on field investigation. The results showed that, （1) The litter accumulation of semi-decomposed layer was larger than that of undecomposed layer, and the -Taxodium ascendens forest had the largest litter accumulation among the undecomposed layers, while the Salix jiangsuensis forest had the largest litter accumulation among the semi-decomposed layer. The total litter accumulation of Taxodium ascendens forest was largest, which was 3.90 t/hm². （2) The maximum water holding rate of the undecomposed layer (263.63%-530.86%) was greater than that of semi-decomposed layer(209.17%-277.91%). The maximum water capacity of the undecomposed layer and the semi-decomposed layer were 0.95-4.48 t/hm² and 4.15-6.02 t/hm²， respectively, and the Taxodium ascendens forest and Salix jiangsuensis forest exbihited highest maximum water capacity-correspondingly. (3) The effective storage capacity of undecomposed layer was 0.44-3.11 t/hm², of which the Taxodium ascendens forest was highest. And the effective storage capacity of semi-decomposed layer was 0.75-3.82 t/hm²， of which the Platanus acerifolia forest was highest. Among all the forest types, the total maximum water holding capacity and the total effective storage capacity of Taxodium ascendens forest were both largest and its values were 9.61 and 5.64 t/hm²， respectively. (4) With the-immersion time prolonged, the litter water holding capacity increased significantly at the beginning, and then slowed down, and finally reached saturation, the relationship between them  showed as logarithmic function. Otherwise, With the immersion time prolonged, the litter water absorption rate was higher in the early stage, then decreased sharply, and finally approached 0, the relationship between them was power function. （5) The maximum and effective water holding capacity of Salix jiangsuensis forest were largest in topsoil layer among all the forest types, which was 1 116.27 and 213.27 t/hm²， respectively. For the litter layer, the water conservation ability of Taxodium ascendens forest was better than others, while, the water conservation ability of Salix jiangsuensis forest was better than others in the topsoil. In general, Salix jiangsuensis forest is superior on water conservation comprehensively.

A large number of ecological land use has been transformed to non-ecological land use, and the key ecological conservation sources in the regional landscape pattern have been shrinking, and the function of ecological services has been weakening, which makes ecological security face new challenges.With the agglomeration of spatial elements and the rapid development of economy.This paper calculates the spatial and temporal differentiation characteristics of ecosystem service value and ecological risk index in the Three Gorges Reservoir area in the past 30 years and their correlation,based on the Landsat TM/Landsat 8OLI images of the Three Gorges Reservoir area in 1986, 1995, 2000, 2007, 2010 and 2018, and based on the 5 km*5 km evaluation cell.The results show that:(1)The total value of ecosystem services in the Three Gorges Reservoir area continued to increase from 1 639.56*108 yuan to 1 662.01*108 yuan, with an overall increase of 1.37%.The proportion of high-level ecological risk levels showed a slow decreasing trend, with an overall decline of 10.89%, and the ecological situation of the study area improved from 1986 to 2018;(2)There is a certain negative correlation between ecosystem service value and ecological risk index per unit area in the Three Gorges Reservoir Area, and there is also a certain negative correlation in space;(3)The value of ecosystem services and ecological risk index are not synchronized in the change rate.The value of ecosystem services corresponding to the high-risk index region has a greater possibility of reduction, which needs special attention.The purpose of the study is to provide reference for the safe operation of the Three Gorges Project and the sustainable development and utilization of the Three Gorges Reservoir Area.

Water and sediment change of the Three Major Outlets River (Ouchi, Hudu, Songzi rivers) to the Dongting Lake from the Jingjiang River in the middle Yangtze River is an important part of the Jingjiang River-Dongting Lake relation which is adjusted by the water-sediment change. The Three Gorges Reservoir has resulted in the significant reduction of diversion discharge in the Three Major Outlets River. Hydrological data (water level and discharge) were collected in five stations (Xinjiangkou and Shadaoguan stations at the Songzi inlet, Mituosi station at the Taipingkou inlet, Guanjiapu and Kangjiagang stations at the Ouchikou inlet) in 2003-2018, to fit five groups of empirical formulae for the diversion discharge calculation incorporating the effect of water level reduction at the inlet. Result shows that the diversion discharge of the Three Major Outlets is mainly a function of the water level in the inlet area. The simplified formulae of diversion discharge obtained are further modified using the channel gradient and water level drop at the inlet area, and channel width. In 2017-2018, the measured data in Guanjiapu and Kangjiagang stations of Ouchi River were used to verify the predicted values, 4.5% and 13.7% of relative error, respectively, 11.5% in the Mituoshi station of Hudu River, and 4.5% and 7.3% in Xinjiangkou and Shadaoguan stations of Songzi River, respectively. In summary, five modified empirical formulae are in good agreement with the measured data, which can be used to estimate the change of diversion discharge of the Three Major Outlets River affected by future water level dropping of the Jingjiang River.

The blue-green space, consisting of water and vegetation, can effectively mitigate the negative influence produced by urban heat island, which will help improve the urban thermal environment and promote the sustainable development. In this study，Landsat images collected from 2004, 2010 and 2014 were used to retrieve land surface temperature to characterize the thermal environment. The cooling island intensity and index were constructed to explore the spatial-temporal characteristics of the cooling island produced by blue-green space. The profile analysis and statistic method were employed to study the impact of the total area of blue green space, land use and land cover changes and social economy factors on the cooling island. The results showed that: from 2004 to 2014, the area of cooling island zone had decreased by 24.04%, which were mainly located at the north and east part in Suzhou. However, the cooling island intensity of the blue-green space were 6.3℃,7.1℃, and 9.6℃ in 2004, 2010 and 2014, respectively, which showed an increasing trend. However, when taking the area changes of blue green space into account, the cooling effect produced by blue and green space has decreased because of urbanization. The cooling effect of blue space (10.5℃) consisting of water was much higher than that of green space (4.8℃) which was consisted of vegetation, and the cooling effect of flowing river was stronger than still lakes. The changes of land use and land cover could make big differences on the spatial pattern of the cooling island. The loss of paddy land was the dominant factor for the expansion of urban area, resulting in the loss of cooling island zone at the same time. However, the total area of lakes in Suzhou has increased a little during 2004 to 2010, which reflected the choice of protection for different blue and green spaces by decision makers.

Dongting Lake basin is one of the large freshwater wetland system in China, having three important nature reserves. Water level is the basis to maintain the structure, function and integrity of the lake ecosystem. In this study, two special types of recurrent neural network method, Long Short-term Memory (LSTM) and The Gated Recurrent Unit (GRU), were propused to construct the Dongting Lake’s water level prediction model, in order to predict the water level change of Dongting Lake under the synthetical influence of the Yangtze river and the four sub-tributaries in the local catchment. The advantage of the LSTM and the GRU is their ability to learn the long-term dependencies between the provided input and output of the network, whichis important to simulate the cumulative change of water level affected by upstream inflow. The daily flows of five hydrological stations, which located at the stem stream of Yangtze River and the four sub-tributaries in the local catchment, were provided as the model’s input conditions to predict the process of water level change in different Dongting Lake areas. The water level and flow time series from 1980 to 2002 were used to test the model, and the data set from 2003 to 2014 were applied to validate our approach. In addition, the predicted results of the two models were compared. The results show that: (1) Models based on the recurrent neural network methods of LSTM and GRU can reasonably predict the process of water level change in three Dongting Lake areas, both NSE and R2 are 0.91 - 0.95. (2) The accurate of LSTM model is slightly higher than the GRU. It’s worth to say that the GRU model is a good alternative to the LSTM for that the former’s calculation is more efficient than the latter. (3) The model can simulate a flood event more accurately. The maximum relative error between the predicted value of flood level and the real value is less than 5%. Moreover, the model has a good prediction ability of multi-step time series, which underlines the potential of the LSTM for hydrological modelling applications.

Stem water potential and trunk sap flow for some typical tree species including Osmanthus fragrans, Cinnamomum camphora, Pinus massoniana and Liquidambar formosana in Changsha were monitored from 2013 to 2015. Meanwhile, the meteorological factors and soil moisture were measured in parallel. The main objects are to explore the response of transpiration to environmental factors, and to select an optimal transpiration model for this area by comparing the performance of the MJS, BTA and MBTA models. The results show that during the non-drought period, tree transpiration was less sensitive to precipitation and soil moisture. Solar radiation exerted the greatest effects on Osmanthus fragrans and Pinus massoniana transpiration with the sensitivity coefficient > 0.75, while the sensitivity of transpiration for Cinnamomum camphora and Liquidambar formosana tree to solar radiation and water vapor pressure deficit was strong. During the drought period in 2013, soil water content was the dominant factor for tree transpiration with the sensitivity coefficient > 0.71, and then tree transpiration was limited by the effects of temperature and water vapor pressure deficits. Among the three models, the MBTA model performed the best in fitting the observed tree transpiration, with a relative error was less than 5%; the BTA model failed to simulate the decline of the tree's daily transpiration during the drought period in 2013, and significantly overestimated transpiration of Pinus massoniana during the growth season in 2014 and 2015; the simulation accuracy of MJS model was not good. The performance of the three models in the growth season of 2013 was worse than that in 2014 and 2015, indicating that when the environmental stress exceeded the adaptive range of trees, the physiological structure of trees was likely to be changed, which leads to a reduction of the simulation accuracy of transpiration model constructed by environmental factors.

Based on monthly precipitation and average temperature data from 13 stations in the Hanjiang River Basin from 1960 to 2017, this paper calculated the standardized precipitation evapotranspiration index (SPEI) at different time scales, analyzed the temporal and spatial characteristics of meteorological drought in the Hanjiang River Basin, and discussed the causes of meteorological drought in the basin in combination with the atmospheric circulation index. The results show that: (1) The Han River Basin SPEI value has a main period of 3-4a, showing a state of alternating wet and dry. (2) On an annual scale, the frequency of light and middling droughts ranges from 5% to 24%, and is higher in the western regions. In spring, light and moderate droughts occur with a frequency of 6% -19%; in summer, the frequency of light drought is higher in the middle than the surroundings, and the highest frequency is 20%-28%; in autumn, the frequency of drought in the central region is high; in winter, the frequency of drought is generally higher than 10%, but it is mainly light and moderate. (3) On an annual scale, the SPEI value of the Han River Basin decreased at a rate of 0.0021/a, indicating that global warming has little effect on interannual drought conditions in the basin.SPEI values in spring and autumn are significantly correlated with MEI and SOI, and the absolute value of the correlation coefficient is between 0.271-0.422; the SPEI value in summer was significantly correlated with EASM, and the absolute value of the correlation coefficient was between 0.261-0.498; the SPEI value in winter was significantly correlated with AO, NAO, and the absolute value of the correlation coefficient was between 0.220-0.281.

Based on the monthly precipitation data of 103 meteorological stations in the Dongting Lake Basin from 1960 to 2017 and NCEP/NCAR reanalysis data, combining the Z-index and the droughts-floods region index, in order to enhance the understanding of seasonal droughts-floods abnormality and possible direct influence factors, the spatial-temporal distribution characteristics of seasonal droughts-floods abnormality, the synchronic atmospheric circulation and water vapor transport feature in typical droughts-floods years in the basin over 57 years were analysed. The results showed that in the statistical sense, it was unlikely that the droughts/floods abnormality appeared for two consecutive years, and the frequency of coexistence of droughts-floods abnormality in spring and summer was higher than that in autumn and winter in the basin. The dry and wet evolution showed interannual characteristic and obvious spatial distribution in spring and autumn, showing interdecadal transition and wetting tendency in winter and summer. In addition, each season showed that flood was heavier than drought in statistical sense. The synchronic atmospheric circulation feature would exert significant impacts on the droughts-floods abnormality in the basin. When the meridional (zonal) circulation was strong, the droughts were more likely to occur in winter (summer) and spring (autumn). When the subtropical high ridge was northward, the droughts tended to occur in summer and autumn; when the subtropical high was strong and westward, the floods were more likely to occur in winter. The Z-index was significantly positively correlated with the net meridional water vapor flux in each season, and the net water vapor budget in spring, summer and autumn, and may be more closely correlated with precipitation dynamic condition in winter.

Affected by climate, topography and other factors, meteorological drought index has different performance in different areas. Sichuan Province, located in the upper reaches of the Yangtze River, has complex geomorphic conditions and diverse climate types. Its applicability needs to be evaluated before using the meteorological drought index for drought monitoring. In this paper, we used the daily precipitation and daily mean temperature data of 34 meteorological stations in Sichuan Province from 1987 to 2016. Based on SPI index, SPEI index and MCI index (added in the new national standard document of 2017), by using some methods of time series analysis and spatial interpolation, the drought processes and drought years from 1987 to 2010 were analyzed. By means of the established RMSE (Root Mean Square Error) index and scoring method, the consistency of drought intensity and drought range reflected by multi-time scale indices was mainly studied. The results show that: (1) In general, applicability of MCI index is the best and SPI index is close to the SPEI index; On a specific monthly scale, MCI, SPI 3 (3 months), SPEI 3 (3 months), are the top three in the applicable ranking. (2) From the perspective of geographical division, the eastern Sichuan Basin is suitable for MCI index, the southwest mountainous area of Sichuan is suitable for SPI 3 index and the northwest Sichuan Plateau is suitable for two indices of SPI 6 (6 months) and SPI 1 (1 month). (3) The monitoring error of SPI, SPEI and MCI index in eastern Sichuan Basin is the smallest, followed by that in the southwest mountainous area of Sichuan, and the largest in the northwest Sichuan Plateau.

The “5·12” earthquake has caused great damage to the ecological environment of Wenchuan County. Quick and effective assessment of the ecological environment quality in the earthquake-stricken areas is an important basic work for post-disaster reconstruction. Based on TM and OLI data and principal component analysis technology of ENVI platform, the remote sensing ecological index (RSEI) of three periods in the study area is obtained, which can be used to analyze the changes and restoration of the ecological environment quality in the study area from 2003 to 2017. The results showed that: (1) From 2003 to 2017, the ecological environment quality of Wenchuan County was mainly moderate or above, and the proportion of moderate or above grade was 90.21%, 82.01% and 94.65% respectively in the three periods. (2) The average RSEI index of the three periods was 0.627, 0.617 and 0.716 respectively, so the ecological environment quality experienced the process of no recovery to recovery and improvement, and the ecological environment quality at the end of the study exceeded the beginning of the study. (3) From 2003 to 2017, the area transfer of the three grades of poor, moderate and good in the ecological environment quality of Wenchuan County was obvious, while the two grades of bad and high did not change much. In T1 period, moderate and good grade were transferred to lower grade; in T2 period, poor, moderate and good grade were transferred to higher grade; in T3 period, except high grade, the other grades were mainly transferred to higher grade. (4) In the area between 1 498-4 466 meters above sea level and 15-63 degrees of slope, the recovery of ecological environment quality is the most obvious.

The interaction of multi-hazards has attracted much attention in recent years, especially the concurrent of heat waves and droughts, that improved the impacts on the agriculture, ecosystem and human daily life. In this study, based on meteorological data from 197 meteorological stations for the period of 1960-2018, we constructed a conceptual framework including the concurrent heat waves and droughts hazard, exposure, and vulnerability. Meanwhile, the spatiotemporal variation of the concurrent heat waves and droughts was analyzed in north and south of Qinling-Huaihe region. More importantly, we used path analysis to investigate the relationship between hazard, exposure and vulnerability based on socioeconomic and demographic data. The results showed, (1) during 1960 to 2018, the concurrent heat waves and droughts presented the spatiotemporal cluster by using bipartite networks in study region. In detailed, one distinct phase was identified that the concurrency of heat waves and droughts is significant from 1970s to the early 1980s, and there are three spatial cluster regions, i.e. Huaihe Plain, the middle and lower reaches of the Yangtze River, Hill areas of eastern Sichuan and Wushan Mountains in central China. It should be noted that the concurrency for heat waves and droughts weakened gradually after 1990s; (2) The risk of concurrent of heat waves and droughts showed a significant pattern of spatial variation. About 70% of the top 30 cities with the greatest risk located in Huaihe Plain and the middle and lower reaches of the Yangtze River and 30% covered in Sichuan Basin, led by the dense population and economy, which meant greater exposure and the higher risk of the concurrent heat waves and droughts hazard; (3)In the term of influence factors, the path analysis confirmed that the negative relationship between susceptibility and coping capacity, and further verified that hazard, exposure correlated negatively with concurrent risk. These results implied that greater coping capacity was significant driving factor of lower concurrent risk in area with the more concurrent of heat waves and droughts and exposure.