The East Asian monsoon has a tremendous impact on agricultural production in China. An assessment of the risk of drought disaster in maize-producing regions is therefore important in ensuring a reduction in such disas...The East Asian monsoon has a tremendous impact on agricultural production in China. An assessment of the risk of drought disaster in maize-producing regions is therefore important in ensuring a reduction in such disasters and an increase in food security. A risk assessment model, EPIC(Environmental Policy Integrated Climate) model, for maize drought disasters based on the Erosion Productivity Impact Calculator crop model is proposed for areas with the topographic characteristics of the mountainous karst region in southwest China. This region has one of the highest levels of environmental degradation in China. The results showed that the hazard risk level for the maize zone of southwest China is generally high. Most hazard index values were between 0.4 and 0.5,accounting for 47.32% of total study area. However,the risk level for drought loss was low. Most of the loss rate was <0.1, accounting for 96.24% of the total study area. The three high-risk areas were mainlydistributed in the parallel ridge–valley areas in the east of Sichuan Province, the West Mountain area of Guizhou Province, and the south of Yunnan Province.These results provide a scientific basis and support for the reduction of agricultural drought disasters and an increase in food security in the southwest China maize zone.展开更多
Developed independently by China,HJ-1A/B satellites have operated well on-orbit for five years and acquired a large number of high-quality observation data.The realization of the observation data geometric precision c...Developed independently by China,HJ-1A/B satellites have operated well on-orbit for five years and acquired a large number of high-quality observation data.The realization of the observation data geometric precision correction is of great significance for macro and dynamic ecological environment monitoring.The paper analyzed the parameter characteristics of HJ-1 satellite and geometric features of HJ-1 satellite level 2 data(systematic geo- corrected data).Based on this,the overall HJ- 1 multi- sensor geometric correction flow and charge-coupled device(CCD) automatic geometric precision correction method were designed.Actual operating data showed that the method could achieve good result for automatic geometric precision correction of HJ-1 satellite data,automatic HJ-1 CCD image geometric precision correction accuracy could be achieved within two pixels and automatic matching accuracy between the images of same satellite could be obtained less than one pixel.展开更多
Environment and disaster monitoring and forecasting small satellite constellation A and B satellites(HJ-1-A,B) are called "environment and disaster reduction satellites A and B" for short.The constellation a...Environment and disaster monitoring and forecasting small satellite constellation A and B satellites(HJ-1-A,B) are called "environment and disaster reduction satellites A and B" for short.The constellation adopts a 10:30LT sun-synchronous circular orbit,with orbit altitude of 649km.HJ1-A and HJ-1-B are distributed with a phase difference of 180° in the same orbital plane,so as to enhance the time resolution of earth observation.The satellites have orbit maintenance capability,the lifetime is 3 years.Both satellites adopt CAST968 platforms.Two wide-coverage multispectral CCD cameras with resolution 30m and width 700km,a super-spectral imager with resolution 100m and width 50km as well as a data transmission subsystem of 120Mbit/s are deployed on HJ-1-A,which also carries Ka communication testing equipment of Thailand.HJ-1-B has two wide-coverage multispectral CCD cameras(the same as satellite A),one infrared camera with resolution 150m and width 720km and a data transmission subsystem of 60Mbit/s.The coverage period of the wide-coverage multispectral CCD camera is 48 hours.The revisit period of super-spectral imager is 96 hours and the coverage period ofinfrared camera is 96 hours.展开更多
In consideration of the resource wasted by unreasonable layout scheme of tidal current turbines, which would influence the ratio of cost and power output, particle swarm optimization algorithm is introduced and improv...In consideration of the resource wasted by unreasonable layout scheme of tidal current turbines, which would influence the ratio of cost and power output, particle swarm optimization algorithm is introduced and improved in the paper. In order to solve the problem of optimal array of tidal turbines, the discrete particle swarm optimization(DPSO) algorithm has been performed by re-defining the updating strategies of particles’ velocity and position. This paper analyzes the optimization problem of micrositing of tidal current turbines by adjusting each turbine’s position,where the maximum value of total electric power is obtained at the maximum speed in the flood tide and ebb tide.Firstly, the best installed turbine number is generated by maximizing the output energy in the given tidal farm by the Farm/Flux and empirical method. Secondly, considering the wake effect, the reasonable distance between turbines,and the tidal velocities influencing factors in the tidal farm, Jensen wake model and elliptic distribution model are selected for the turbines’ total generating capacity calculation at the maximum speed in the flood tide and ebb tide.Finally, the total generating capacity, regarded as objective function, is calculated in the final simulation, thus the DPSO could guide the individuals to the feasible area and optimal position. The results have been concluded that the optimization algorithm, which increased 6.19% more recourse output than experience method, can be thought as a good tool for engineering design of tidal energy demonstration.展开更多
The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought...The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a challenge.This paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is proposed.Dynamic range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to 1.00.Moreover,the saturation effect in NDVI is effectively removed by using the S-NDVI.Further analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,respectively.In the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are used.In this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture content.Thus,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.展开更多
Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the...Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the ablation zone of Shuiguan Glacier No.4, Qilian Mountains, China, combined with the balance ratio between accumulation and ablation, we established a linear relation between mass balance and altitude. The results show that the mean annual mass balance of this glacier was ~510 mm w.e. from 2010 to 2013. The uncertainty in the balance ratio value does not lead to a significant difference in the mass balance. The equilibrium-line altitude rose by 180 m from 1972 to 2013, while the accumulation–area ratio decreased from 0.68 to 0.25. These variations may be caused by changes in air temperature. Meanwhile, the glacier is at present not in a steady state, and it may continue to shrink by a further ~900 m, even without further climate warming. In the western Lenglongling Mountains, assuming that the glaciers are in a steady state and the Equilibrium-line altitudes(ELAs)remain similar, there will be only 46 glaciers left, covering a total area of 19.2 km^2, in other words, only 22.3% of the glaciers area in 1972.展开更多
This study presents an investigation of the scattering and backscattering properties of the particulates in three Chinese inland lakes(the Taihu Lake, the Chaohu Lake and the Dianchi Lake) based on in situ measurement...This study presents an investigation of the scattering and backscattering properties of the particulates in three Chinese inland lakes(the Taihu Lake, the Chaohu Lake and the Dianchi Lake) based on in situ measurements taken at 119 sites. We modeled the particulate scattering spectra using a wavelength-dependent power-law function, finding that the power-law exponents in the Taihu Lake and the Chaohu Lake differ from those in the Dianchi Lake but are similar to the values in the U.S. coastal waters. In contrast to the open ocean, the backscattering properties in the three lakes can not be determined only from chlorophyll-a concentration. The backscattering ratio spectra exhibit a wavelength dependence feature in all three lakes, generally decreasing with the increasing wavelength. Analysis results of the correlations between the backscattering ratio and the individual water quality parameters clearly show that there are distinctive relations among the three lakes, attributed primarily to different compositions of optically active materials in the three lakes. Analysis of the mass-specific scattering and backscattering coefficients shows that the coefficients at wavelength 532 nm in the Taihu Lake and Chaohu Lake are similar, but they are apparently different from those in the Dianchi Lake. Lastly, Model I multiple linear regressions were adopted to partition the mass-specific cross-sections for scattering and backscattering into organic and inorganic cross-sections to further interpret the scattering and backscattering properties. The relative contribution of organic and inorganic particulates to scattering and backscattering is clearly different among the three lakes. The scattering and backscattering properties of the particulates in the three inland lakes vary significantly based on our collected data. The results indicated that the existing semi-analytical water quality retrieval models of the Taihu Lake can not be applied perfectly to the Chaohu Lake and the Dianchi Lake.展开更多
Species diversity exhibit a close relationship with ecosystem services, and making clear the relationship can help us understand the service value and functional mechanism of ecosystems and take measures to promote hu...Species diversity exhibit a close relationship with ecosystem services, and making clear the relationship can help us understand the service value and functional mechanism of ecosystems and take measures to promote human well-being. Here, we used species survey data and multi-source habitat factors to simulate the spatial distribution of species richness and four types of ecosystem services(water production, net primary productivity, carbon storage, and habitat quality) in Sanjiangyuan National Park located in Qinghai Province, China. We also analyzed the spatial distribution pattern and explored the spatial relationship between species richness and ecosystem services through Geo Detector analyses. We found that high species richness in Sanjiangyuan National Park was shown to be mainly distributed in areas with high vegetation growth on both sides of rivers. The effect of climate on the spatial distribution of species richness in the park is the highest among all the selected environmental variables. For the relationship between species diversity and ecosystem services, the relative correlation strength of single ecosystem service varied among the three main ecosystems(grassland, meadow, and wetland) and all relations are positive.展开更多
[Objective] The research aimed to study clustering of the six climatic factors in Yunnan tobacco planting zone. [Method] 6 meteorological elements in 89 tobacco-growing counties and 12 sub-prefectures were conducted c...[Objective] The research aimed to study clustering of the six climatic factors in Yunnan tobacco planting zone. [Method] 6 meteorological elements in 89 tobacco-growing counties and 12 sub-prefectures were conducted clustering analysis. According to indicator and climate characteristics of the each type, climate in tobacco planting area of Yunnan Province was divided. [Result] Climate in tobacco planting area of Yunnan Province could be divided into eight types: Jiangchuan (24 counties, belonged to northern and central subtropical climate belts), Songming (27 counties, belonged to northern subtropical and central, south, north temperate climate belts), Tengchong (3 counties, belonged to northern subtropical climate belt), Mile (12 counties, belonged to central and southern subtropical climate belts), Qiubei (11 counties, belonged to southern subtropical climate belt), Yanjin (4 counties, belonged to central subtropical humid climate belt), Yuanjiang (4 counties, belonged to southern subtropical and northern tropical climate belts), Zhenxiong (3 counties, belonged to warm temperate and northern subtropical climate belts) were eight representatives. Among 1-8 eco-zones, domestic and foreign cities where climate reached level-one similarity were respectively 3, 1, 1, 0, 1, 1, 0 and 1, up to level-two similarity, respectively 12, 15, 3, 13, 13, 1, 5 and 3. Among 8 major ecological zones, similar distance of the city reaching level-one similarity was in the range of 0.28 to 0.45, and similar degree was the highest. Variety introduction among these places would be successful. Similar distance of the city reaching level-two similarity was between 0.51 and 1.00, and similar degree was higher. Mutual variety introduction had high successful rate in these places. [Conclusion] The research provided theoretical basis for selecting new suitable tobacco variety and optimizing tobacco variety layout in different zones.展开更多
Patterns in species geographic range size are relatively well-known for vertebrates,but still poorly known for plants.Contrasts of these patterns between groups have rarely been investigated.With a detailed flora and ...Patterns in species geographic range size are relatively well-known for vertebrates,but still poorly known for plants.Contrasts of these patterns between groups have rarely been investigated.With a detailed flora and fauna distribution database of Xinjiang,China,we used regression methods,redundancy analysis and random forests to explore the relationship of environment and body size with the geographic range size of plants,mammals and birds in Xinjiang and contrast these patterns between plants and animals.We found positive correlations between species range size and body size.The range size of plants was more influenced by water variables,while that of mammals and birds was largely influenced by temperature variables.The productivity variable,i.e.,Enhanced Vegetation Index(EVI)was far more correlated with range size than climatic variables for both plants and animals,suggesting that vegetation productivity inferred from remote sensing data may be a good predictor of species range size for both plants and animals.展开更多
We analyzed the Normalized Difference Vegetation Index (NDVI) from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand t...We analyzed the Normalized Difference Vegetation Index (NDVI) from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand the eco-hydrological effect of atmospheric precipitation and its relationship with vegetation. First,we analyzed its general spatio-temporal distribution using its mean,standard deviation and linear trend. Then,we used the Empirical Orthogonal Functions (EOF) method to decompose the NDVI and precipitation data into spatial and temporal modes. We selected four leading modes based on North and Scree test rules and analyzed the synchronous seasonal and inter-annual variability between the vegetation index and precipitation,distinguishing time-lagged correlations between EOF modes with the correlative degree analysis method. According to our detailed analyses,the vegetation index and precipitation exhibit a prominent correlation in spatial distribution and seasonal variation. At the 90% confidence level,the time lag is around 110 to 140 days,which matches well with the seasonal variation.展开更多
Snow depth (SD) is a key parameter for research into global climate changes and land surface processes. A method was developed to obtain daily SD images at a higher 4 km spatial resolution and higher precision with ...Snow depth (SD) is a key parameter for research into global climate changes and land surface processes. A method was developed to obtain daily SD images at a higher 4 km spatial resolution and higher precision with SD measurements from in situ observations and passive microwave remote sensing of Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and snow cover measurements of the Interactive Multisensor Snow and Ice Mapping System (IMS). AMSR-E SD at 25 km spatial resolution was retrieved from AMSR-E products of snow density and snow water equivalent and then corrected using the SD from in situ observations and IMS snow cover. Corrected AMSR-E SD images were then resampled to act as "virtual" in situ observations to combine with the real in situ observations to interpolate at 4 km spatial resolution SD using the Cressman method. Finally, daily SD data generation for several regions of China demonstrated that the method is well suited to the generation of higher spatial resolution SD data in regions with a lower Digital Elevation Model (DEM) but not so well suited to regions at high altitude and with an undulating terrain, such as the Tibetan Plateau. Analysis of the longer time period SD data generation for January between 2003 and 2010 in northern Xinjiang also demonstrated the feasibility of the method.展开更多
The Chinese Government attaches great importance to applications of satellite remote sensing in environmental monitoring.On 6 September 2008,the first two satellites of the Environment and Disaster Monitoring and Pred...The Chinese Government attaches great importance to applications of satellite remote sensing in environmental monitoring.On 6 September 2008,the first two satellites of the Environment and Disaster Monitoring and Prediction Satellite Constellation(HJ),HJ-1A and HJ-1B,were successfully launched,which started a new era of satellite applications for environmental monitoring in China.An introduction to the satellite,instrument,and ground systems of HJ-1A and HJ-1B is presented in this article,and an analysis of their technical performance and characteristics is also given.Focusing on the operational needs of environmental monitoring in China,the general design,functional construction,and operational mode of the application system of HJ-1A and HJ-1B are detailed,and the operations and applications of the two satellites are also discussed.展开更多
Forage supply has been stressed due to the rapid increase in China's livestock consumption.However,the long-term dynamics of the relationships between forage demand and multi-sourced supply are not understood.Here...Forage supply has been stressed due to the rapid increase in China's livestock consumption.However,the long-term dynamics of the relationships between forage demand and multi-sourced supply are not understood.Here,we examine the annual forage demand,or practical carrying capacity(PCC),and supply,or theoretical carrying capacity(TCC)from 2000 to 2019 in China.We construct a forage supply-demand index(FSDI)to represent the forage supply pressure using MODIS-derived net primary productivity products and provincial statistical datasets,and we consider two scenarios.First,natural grasslands are the sole source of forage.Second,natural grassland forage supply is supplemented with straw crops.We find an increase in PCC in northwestern China's major pastoral and agropastoral provincial regions,including Inner Mongolia,Gansu,Ningxia and Qinghai,at rate of 0.24-3.59 million sheep units(SU)a year.As the primary source of forage,the theoretical carrying capacity of natural grasslands(TCCgrass)expanded at a rate of 3 million SU/yr nationally.Crop straws fed 126.58 million SU nationally in 2019,which accounted for 11.3%of the total practical carrying capacity and alleviated the forage supply pressure by reducing FSDI by 26.56%.During 2000–2019,the theoretical carrying capacity of straw crops(TCCcrop)increased rapidly from 76.5 million SU to 126.6 million SU,which accounted for 10%-15%of the total forage supply at the national scale.We also discovered large carrying capacity gaps(TCCgap)in the northwestern pastoral provincial regions of Inner Mongolia,Xinjiang,Gansu,and some agricultural provinces such as Shandong and Henan,when we considered forage supply from both natural grasslands and straw crops.Our findings showed a large forage gap in the traditional pastoral regions,and we also discussed green fodder as a potential solution for balancing the supply of and demand for forage,which may shed light on crop and forage planning.展开更多
Based on the two most recent assessments of Chinese higher plants in 2013 and 2020,of 34,450 and 39,330 species,respectively,we analysed the threatened status of Chinese higher plants.In 2020,around 4,088(10.39%)of th...Based on the two most recent assessments of Chinese higher plants in 2013 and 2020,of 34,450 and 39,330 species,respectively,we analysed the threatened status of Chinese higher plants.In 2020,around 4,088(10.39%)of the assessed species in China are threatened,2,875(7.31%)Near Threatened,27,593(70.16%)not currently threatened and categorised as Least Concern and 4,752(12.08%)categorised as Data Deficient.While in 2013,3,767(10.93%)of the assessed higher plants in China are threatened,2,723(7.90%)Near Threatened,24,296(70.53%)Least Concern and 3,612(10.48%)Data Deficient.Estimates of the Red List Index in the two years show different patterns when using different weighting methods with the equal steps weighting method showing a slight decrease(0.91675-0.91495)and the extinction risk weighting method showing a slight increase(0.98792-0.98797).We inferred that China's threatened plant species were likely/relatively effectively protected.However,attention should also be given to the non-threatened species in the future as an additional strategy for their conservation,to maintain their non-threatened status.展开更多
Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuabl...Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuable in deriving aerosol distribution and properties over land;however,it cannot be applied to bright targets.As a supplement to the DDV algorithm,an algorithm to retrieve AOD over urban areas in North China in winter is developed using MODIS data,including(1) the generation and analysis of adjacent clear-days surface reflectance using MOD09 product from 2007 to 2008,and(2) seasonal aerosol models derived from AERONET data in Beijing and Xianghe sites.Ground-based measurements using sun photometers were used to validate the retrieved AOD,and the correlation coefficient(r) is up to 0.931.Especially for high AOD values(AOD>0.4),more retrievals meet the inversion accuracy.The temporal variations of retrieval errors over urban,rural and mountain regions were examined,and the results indicated that the variation of blue-band surface reflectance is less than 0.02 in a short period except for unusual weather conditions,the retrieval bias is under 0.08,and the relative error decreases as the AOD increases.展开更多
The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wet...The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wetland inventory data in Beijing, the water bodies were visually classified into different types of urban wetlands, and data on the urban wetlands of Beijing in 1986, 1991, 1996, 2000, 2002, 2004 and 2007 were obtained. Thirteen driving factors that affect wetland change were selected, and gray correlation analysis was employed to calculate the correlation between each driving factor and the total area of urban wetlands. Then, six major driving factors were selected based on the correlation coefficient, and the contribution rates of these six driving factors to the area change of various urban wetlands were calculated based on canonical correlation analysis. After that, this research analyzed the relationship and mechanism between the main driving factors and various types of wetlands. Five conclusions can be drawn. (1) The total area of surface water bodies in Beijing increased from 1986 to 1996, and gradually decreased from 1996 to 2007. (2) The areas of the river wetlands, water storage areas and pool and culture areas gradually decreased, and its variation tendency is consistent with that of the total area of wetlands. The area of the mining water areas and wastewater treatment plants slightly increased. (3) The six factors of driving forces are the annual rainfall, the evaporation, the quantity of inflow water, the volume of groundwater available, the urbanization rate and the daily average discharge of wastewater are the main factors affecting changes in the wetland areas, and they correlate well with the total area of wetlands. (4) The hydrologic indicators of water resources such as the quantity of inflow water and the volume of groundwater are the most important and direct driving forces that affect the change of the wetland area. These factors have a combined contribution rate of 43.94%. (5) Climate factors such as rainfall and evaporation are external factors that affect the changes in wetland area, and they have a contribution rate of 36.54%. (6) Human activities such as the urbanization rate and the daily average quantity of wastewater are major artificial driving factors. They have an influence rate of 19.52%.展开更多
Ecosystem services have become one of the core elements of ecosystem management and evaluation. As a key area of ecosystem services and for maintaining national ecological security, ecosystem changes and implementatio...Ecosystem services have become one of the core elements of ecosystem management and evaluation. As a key area of ecosystem services and for maintaining national ecological security, ecosystem changes and implementation effect evaluation are important in national key ecological function zones, for promoting the main function zone strategy and for improving the construction of an ecological civilization. This article studies the ecological zone of a tropical rainforest region in the central mountain area of Hainan Island, China. Multi-source satellite data and ground observation statistics are analyzed with geo-statistics method and ecological assessment model. The core analysis of this paper includes ecosystem patterns, quality and services. By means of spatial and temporal scale expansion and multidimensional space-time correlation analysis, the trends and stability characteristics of ecosystem changes are analyzed, and implementation effect evaluation is discussed. The analysis shows a variety of results. The proportion of forest area inside the ecological zone was significantly higher than the average level in Hainan Island. During 1990–2013, settlement gradually increased inside the ecological zone. After implementation of the zone in 2010, human activity intensity increased, with the main land use being urban construction and land reclamation. Water conservation in the ecological function zone was higher than that outside the zone. In general, it increased slightly, but had obvious fluctuations. Soil conservation inside the zone was also better than that outside. However, it demonstrated dramatic fluctuations and relatively poor stability during 1990–2013. The human disturbance index inside the zone was significantly lower than that outside, and had a lower biodiversity threat level. Especially in 2010–2013, the increased range of the human disturbance index inside the zone was significantly less than that outside.展开更多
It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolutio...It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 41301593 and 41471428)the Arid Meteorology Science Foundation, CMA (IAM201407)the State Key Development Program for BasicResearch of China (Grant No. 2012CB955402)
文摘The East Asian monsoon has a tremendous impact on agricultural production in China. An assessment of the risk of drought disaster in maize-producing regions is therefore important in ensuring a reduction in such disasters and an increase in food security. A risk assessment model, EPIC(Environmental Policy Integrated Climate) model, for maize drought disasters based on the Erosion Productivity Impact Calculator crop model is proposed for areas with the topographic characteristics of the mountainous karst region in southwest China. This region has one of the highest levels of environmental degradation in China. The results showed that the hazard risk level for the maize zone of southwest China is generally high. Most hazard index values were between 0.4 and 0.5,accounting for 47.32% of total study area. However,the risk level for drought loss was low. Most of the loss rate was <0.1, accounting for 96.24% of the total study area. The three high-risk areas were mainlydistributed in the parallel ridge–valley areas in the east of Sichuan Province, the West Mountain area of Guizhou Province, and the south of Yunnan Province.These results provide a scientific basis and support for the reduction of agricultural drought disasters and an increase in food security in the southwest China maize zone.
文摘Developed independently by China,HJ-1A/B satellites have operated well on-orbit for five years and acquired a large number of high-quality observation data.The realization of the observation data geometric precision correction is of great significance for macro and dynamic ecological environment monitoring.The paper analyzed the parameter characteristics of HJ-1 satellite and geometric features of HJ-1 satellite level 2 data(systematic geo- corrected data).Based on this,the overall HJ- 1 multi- sensor geometric correction flow and charge-coupled device(CCD) automatic geometric precision correction method were designed.Actual operating data showed that the method could achieve good result for automatic geometric precision correction of HJ-1 satellite data,automatic HJ-1 CCD image geometric precision correction accuracy could be achieved within two pixels and automatic matching accuracy between the images of same satellite could be obtained less than one pixel.
文摘Environment and disaster monitoring and forecasting small satellite constellation A and B satellites(HJ-1-A,B) are called "environment and disaster reduction satellites A and B" for short.The constellation adopts a 10:30LT sun-synchronous circular orbit,with orbit altitude of 649km.HJ1-A and HJ-1-B are distributed with a phase difference of 180° in the same orbital plane,so as to enhance the time resolution of earth observation.The satellites have orbit maintenance capability,the lifetime is 3 years.Both satellites adopt CAST968 platforms.Two wide-coverage multispectral CCD cameras with resolution 30m and width 700km,a super-spectral imager with resolution 100m and width 50km as well as a data transmission subsystem of 120Mbit/s are deployed on HJ-1-A,which also carries Ka communication testing equipment of Thailand.HJ-1-B has two wide-coverage multispectral CCD cameras(the same as satellite A),one infrared camera with resolution 150m and width 720km and a data transmission subsystem of 60Mbit/s.The coverage period of the wide-coverage multispectral CCD camera is 48 hours.The revisit period of super-spectral imager is 96 hours and the coverage period ofinfrared camera is 96 hours.
基金financially supported by the Marine Renewable Energy Funding Project(Grant Nos.GHME2017ZC01 and GHME2016ZC04)the National Natural Science Foundation of China(Grant Nos.5171101175 and 51679125)+1 种基金Tianjin Municipal Natural Science Foundation(Grant No.16JCYBJC20600)Technology Innovation Fund of National Ocean Technology Center(Grant No.F2180Z002)
文摘In consideration of the resource wasted by unreasonable layout scheme of tidal current turbines, which would influence the ratio of cost and power output, particle swarm optimization algorithm is introduced and improved in the paper. In order to solve the problem of optimal array of tidal turbines, the discrete particle swarm optimization(DPSO) algorithm has been performed by re-defining the updating strategies of particles’ velocity and position. This paper analyzes the optimization problem of micrositing of tidal current turbines by adjusting each turbine’s position,where the maximum value of total electric power is obtained at the maximum speed in the flood tide and ebb tide.Firstly, the best installed turbine number is generated by maximizing the output energy in the given tidal farm by the Farm/Flux and empirical method. Secondly, considering the wake effect, the reasonable distance between turbines,and the tidal velocities influencing factors in the tidal farm, Jensen wake model and elliptic distribution model are selected for the turbines’ total generating capacity calculation at the maximum speed in the flood tide and ebb tide.Finally, the total generating capacity, regarded as objective function, is calculated in the final simulation, thus the DPSO could guide the individuals to the feasible area and optimal position. The results have been concluded that the optimization algorithm, which increased 6.19% more recourse output than experience method, can be thought as a good tool for engineering design of tidal energy demonstration.
基金Under the auspices of National Natural Science Foundation of China(No.41071221)National Science Technology Support Program(No.2008BAC34B06)China Postdoctoral Science Foundation(No.20110490200)
文摘The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a challenge.This paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is proposed.Dynamic range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to 1.00.Moreover,the saturation effect in NDVI is effectively removed by using the S-NDVI.Further analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,respectively.In the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are used.In this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture content.Thus,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.
基金financially supported by the Ministry of Science and Technology of the People’s Republic of China (No. 2013FY111400)National Natural Science Foundation of China (No.41471008+1 种基金 No. 41571003)Fundamental Research Funds for the Central Universities (lzujbky-2015-126)
文摘Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the ablation zone of Shuiguan Glacier No.4, Qilian Mountains, China, combined with the balance ratio between accumulation and ablation, we established a linear relation between mass balance and altitude. The results show that the mean annual mass balance of this glacier was ~510 mm w.e. from 2010 to 2013. The uncertainty in the balance ratio value does not lead to a significant difference in the mass balance. The equilibrium-line altitude rose by 180 m from 1972 to 2013, while the accumulation–area ratio decreased from 0.68 to 0.25. These variations may be caused by changes in air temperature. Meanwhile, the glacier is at present not in a steady state, and it may continue to shrink by a further ~900 m, even without further climate warming. In the western Lenglongling Mountains, assuming that the glaciers are in a steady state and the Equilibrium-line altitudes(ELAs)remain similar, there will be only 46 glaciers left, covering a total area of 19.2 km^2, in other words, only 22.3% of the glaciers area in 1972.
基金Under the auspices of National Natural Science Foundation of China(No.41171269,41101378)
文摘This study presents an investigation of the scattering and backscattering properties of the particulates in three Chinese inland lakes(the Taihu Lake, the Chaohu Lake and the Dianchi Lake) based on in situ measurements taken at 119 sites. We modeled the particulate scattering spectra using a wavelength-dependent power-law function, finding that the power-law exponents in the Taihu Lake and the Chaohu Lake differ from those in the Dianchi Lake but are similar to the values in the U.S. coastal waters. In contrast to the open ocean, the backscattering properties in the three lakes can not be determined only from chlorophyll-a concentration. The backscattering ratio spectra exhibit a wavelength dependence feature in all three lakes, generally decreasing with the increasing wavelength. Analysis results of the correlations between the backscattering ratio and the individual water quality parameters clearly show that there are distinctive relations among the three lakes, attributed primarily to different compositions of optically active materials in the three lakes. Analysis of the mass-specific scattering and backscattering coefficients shows that the coefficients at wavelength 532 nm in the Taihu Lake and Chaohu Lake are similar, but they are apparently different from those in the Dianchi Lake. Lastly, Model I multiple linear regressions were adopted to partition the mass-specific cross-sections for scattering and backscattering into organic and inorganic cross-sections to further interpret the scattering and backscattering properties. The relative contribution of organic and inorganic particulates to scattering and backscattering is clearly different among the three lakes. The scattering and backscattering properties of the particulates in the three inland lakes vary significantly based on our collected data. The results indicated that the existing semi-analytical water quality retrieval models of the Taihu Lake can not be applied perfectly to the Chaohu Lake and the Dianchi Lake.
基金This work was supported by the National Key R&D Program of China(Grant number 2018YFC0507201)the National Natural Science Foundation of China(Grant number 41801366)。
文摘Species diversity exhibit a close relationship with ecosystem services, and making clear the relationship can help us understand the service value and functional mechanism of ecosystems and take measures to promote human well-being. Here, we used species survey data and multi-source habitat factors to simulate the spatial distribution of species richness and four types of ecosystem services(water production, net primary productivity, carbon storage, and habitat quality) in Sanjiangyuan National Park located in Qinghai Province, China. We also analyzed the spatial distribution pattern and explored the spatial relationship between species richness and ecosystem services through Geo Detector analyses. We found that high species richness in Sanjiangyuan National Park was shown to be mainly distributed in areas with high vegetation growth on both sides of rivers. The effect of climate on the spatial distribution of species richness in the park is the highest among all the selected environmental variables. For the relationship between species diversity and ecosystem services, the relative correlation strength of single ecosystem service varied among the three main ecosystems(grassland, meadow, and wetland) and all relations are positive.
基金Supported by Department of Science and Education,State Bureau,China(04A26)
文摘[Objective] The research aimed to study clustering of the six climatic factors in Yunnan tobacco planting zone. [Method] 6 meteorological elements in 89 tobacco-growing counties and 12 sub-prefectures were conducted clustering analysis. According to indicator and climate characteristics of the each type, climate in tobacco planting area of Yunnan Province was divided. [Result] Climate in tobacco planting area of Yunnan Province could be divided into eight types: Jiangchuan (24 counties, belonged to northern and central subtropical climate belts), Songming (27 counties, belonged to northern subtropical and central, south, north temperate climate belts), Tengchong (3 counties, belonged to northern subtropical climate belt), Mile (12 counties, belonged to central and southern subtropical climate belts), Qiubei (11 counties, belonged to southern subtropical climate belt), Yanjin (4 counties, belonged to central subtropical humid climate belt), Yuanjiang (4 counties, belonged to southern subtropical and northern tropical climate belts), Zhenxiong (3 counties, belonged to warm temperate and northern subtropical climate belts) were eight representatives. Among 1-8 eco-zones, domestic and foreign cities where climate reached level-one similarity were respectively 3, 1, 1, 0, 1, 1, 0 and 1, up to level-two similarity, respectively 12, 15, 3, 13, 13, 1, 5 and 3. Among 8 major ecological zones, similar distance of the city reaching level-one similarity was in the range of 0.28 to 0.45, and similar degree was the highest. Variety introduction among these places would be successful. Similar distance of the city reaching level-two similarity was between 0.51 and 1.00, and similar degree was higher. Mutual variety introduction had high successful rate in these places. [Conclusion] The research provided theoretical basis for selecting new suitable tobacco variety and optimizing tobacco variety layout in different zones.
基金This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDA26010101)the National Key Research and Development Program of China(2020YFC0832800)+1 种基金National Natural Science Foundation of China(41801366,52101405)NSFC-RS exchange project between China and UK(42011530175)。
文摘Patterns in species geographic range size are relatively well-known for vertebrates,but still poorly known for plants.Contrasts of these patterns between groups have rarely been investigated.With a detailed flora and fauna distribution database of Xinjiang,China,we used regression methods,redundancy analysis and random forests to explore the relationship of environment and body size with the geographic range size of plants,mammals and birds in Xinjiang and contrast these patterns between plants and animals.We found positive correlations between species range size and body size.The range size of plants was more influenced by water variables,while that of mammals and birds was largely influenced by temperature variables.The productivity variable,i.e.,Enhanced Vegetation Index(EVI)was far more correlated with range size than climatic variables for both plants and animals,suggesting that vegetation productivity inferred from remote sensing data may be a good predictor of species range size for both plants and animals.
基金Foundation: National Natural Science Foundation of China, No.40701172 No.40671122+2 种基金 The International Program for Cooperation in Science and Technology, No.2007DFA20040 National Science and Technology Supporting Item, No.2008BAC34B01 The Beijing Municipal Science and Technology Plan, No.D08040600580801
文摘We analyzed the Normalized Difference Vegetation Index (NDVI) from satellite images and precipitation data from meteorological stations from 1998 to 2007 in the Dongting Lake wetland watershed to better understand the eco-hydrological effect of atmospheric precipitation and its relationship with vegetation. First,we analyzed its general spatio-temporal distribution using its mean,standard deviation and linear trend. Then,we used the Empirical Orthogonal Functions (EOF) method to decompose the NDVI and precipitation data into spatial and temporal modes. We selected four leading modes based on North and Scree test rules and analyzed the synchronous seasonal and inter-annual variability between the vegetation index and precipitation,distinguishing time-lagged correlations between EOF modes with the correlative degree analysis method. According to our detailed analyses,the vegetation index and precipitation exhibit a prominent correlation in spatial distribution and seasonal variation. At the 90% confidence level,the time lag is around 110 to 140 days,which matches well with the seasonal variation.
基金Meteorological Research in the Public Interest,No.GYHY201106014Beijing Nova Program,No.2010B037China Special Fund for the National High Technology Research and Development Program of China(863 Program),No.412230
文摘Snow depth (SD) is a key parameter for research into global climate changes and land surface processes. A method was developed to obtain daily SD images at a higher 4 km spatial resolution and higher precision with SD measurements from in situ observations and passive microwave remote sensing of Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and snow cover measurements of the Interactive Multisensor Snow and Ice Mapping System (IMS). AMSR-E SD at 25 km spatial resolution was retrieved from AMSR-E products of snow density and snow water equivalent and then corrected using the SD from in situ observations and IMS snow cover. Corrected AMSR-E SD images were then resampled to act as "virtual" in situ observations to combine with the real in situ observations to interpolate at 4 km spatial resolution SD using the Cressman method. Finally, daily SD data generation for several regions of China demonstrated that the method is well suited to the generation of higher spatial resolution SD data in regions with a lower Digital Elevation Model (DEM) but not so well suited to regions at high altitude and with an undulating terrain, such as the Tibetan Plateau. Analysis of the longer time period SD data generation for January between 2003 and 2010 in northern Xinjiang also demonstrated the feasibility of the method.
文摘The Chinese Government attaches great importance to applications of satellite remote sensing in environmental monitoring.On 6 September 2008,the first two satellites of the Environment and Disaster Monitoring and Prediction Satellite Constellation(HJ),HJ-1A and HJ-1B,were successfully launched,which started a new era of satellite applications for environmental monitoring in China.An introduction to the satellite,instrument,and ground systems of HJ-1A and HJ-1B is presented in this article,and an analysis of their technical performance and characteristics is also given.Focusing on the operational needs of environmental monitoring in China,the general design,functional construction,and operational mode of the application system of HJ-1A and HJ-1B are detailed,and the operations and applications of the two satellites are also discussed.
基金supported by the Strategic Priority Research Program (XDA26010202,XDA28060100)of Chinese Academy of Sciences (CAS)the CAS Youth Interdisciplinary Team Project (JCTD-2021-04)the Second Tibetan Plateau of Scientific Expedition and Research Program (2019QZKK0608).
文摘Forage supply has been stressed due to the rapid increase in China's livestock consumption.However,the long-term dynamics of the relationships between forage demand and multi-sourced supply are not understood.Here,we examine the annual forage demand,or practical carrying capacity(PCC),and supply,or theoretical carrying capacity(TCC)from 2000 to 2019 in China.We construct a forage supply-demand index(FSDI)to represent the forage supply pressure using MODIS-derived net primary productivity products and provincial statistical datasets,and we consider two scenarios.First,natural grasslands are the sole source of forage.Second,natural grassland forage supply is supplemented with straw crops.We find an increase in PCC in northwestern China's major pastoral and agropastoral provincial regions,including Inner Mongolia,Gansu,Ningxia and Qinghai,at rate of 0.24-3.59 million sheep units(SU)a year.As the primary source of forage,the theoretical carrying capacity of natural grasslands(TCCgrass)expanded at a rate of 3 million SU/yr nationally.Crop straws fed 126.58 million SU nationally in 2019,which accounted for 11.3%of the total practical carrying capacity and alleviated the forage supply pressure by reducing FSDI by 26.56%.During 2000–2019,the theoretical carrying capacity of straw crops(TCCcrop)increased rapidly from 76.5 million SU to 126.6 million SU,which accounted for 10%-15%of the total forage supply at the national scale.We also discovered large carrying capacity gaps(TCCgap)in the northwestern pastoral provincial regions of Inner Mongolia,Xinjiang,Gansu,and some agricultural provinces such as Shandong and Henan,when we considered forage supply from both natural grasslands and straw crops.Our findings showed a large forage gap in the traditional pastoral regions,and we also discussed green fodder as a potential solution for balancing the supply of and demand for forage,which may shed light on crop and forage planning.
基金funded by the Natural Science Foundation of Hunan Province,China(2023JJ40443)the Outstanding Youth Project of Hunan Provincial Education Department(22B0088 and 22B0055)+1 种基金the Joint Fund for Regional Innovation and Development of the National Natural Science Foundation(U22A20570)the Science and Technology Innovation Program of Hunan Province(2022RC4027),China.
文摘Based on the two most recent assessments of Chinese higher plants in 2013 and 2020,of 34,450 and 39,330 species,respectively,we analysed the threatened status of Chinese higher plants.In 2020,around 4,088(10.39%)of the assessed species in China are threatened,2,875(7.31%)Near Threatened,27,593(70.16%)not currently threatened and categorised as Least Concern and 4,752(12.08%)categorised as Data Deficient.While in 2013,3,767(10.93%)of the assessed higher plants in China are threatened,2,723(7.90%)Near Threatened,24,296(70.53%)Least Concern and 3,612(10.48%)Data Deficient.Estimates of the Red List Index in the two years show different patterns when using different weighting methods with the equal steps weighting method showing a slight decrease(0.91675-0.91495)and the extinction risk weighting method showing a slight increase(0.98792-0.98797).We inferred that China's threatened plant species were likely/relatively effectively protected.However,attention should also be given to the non-threatened species in the future as an additional strategy for their conservation,to maintain their non-threatened status.
基金supported by National Natural Science Foundation of Chinafor Young Scholar (Grant No. 41101400)National Natural Science Foundation of China for Key Program (Grant No. 41130528)Opening Foundation of State Key Laboratory of Remote Sensing Science ofChina (Grant No. OFSLRSS201103)
文摘Two factors that affect satellite retrieval of Aerosol Optical Depth(AOD) are aerosol model assumptions and the separation of surface reflectance.NASA/MODIS Dense Dark Vegetation(DDV) algorithm has been proven valuable in deriving aerosol distribution and properties over land;however,it cannot be applied to bright targets.As a supplement to the DDV algorithm,an algorithm to retrieve AOD over urban areas in North China in winter is developed using MODIS data,including(1) the generation and analysis of adjacent clear-days surface reflectance using MOD09 product from 2007 to 2008,and(2) seasonal aerosol models derived from AERONET data in Beijing and Xianghe sites.Ground-based measurements using sun photometers were used to validate the retrieved AOD,and the correlation coefficient(r) is up to 0.931.Especially for high AOD values(AOD>0.4),more retrievals meet the inversion accuracy.The temporal variations of retrieval errors over urban,rural and mountain regions were examined,and the results indicated that the variation of blue-band surface reflectance is less than 0.02 in a short period except for unusual weather conditions,the retrieval bias is under 0.08,and the relative error decreases as the AOD increases.
基金National Natural Science Foundation of China, No.41171318 No.41001160+6 种基金 The Fundamental Research Funds for the Central Universities, the Beijing Plan Program of Science and Technology, No.D08040600580801 International Program for Cooperation in Science and Technology, No.2009DFA 91710 Beijing Forestry Survey and Design Institute provided the data and report of the wetland inventory. We would like to express our sincere appreciation for their suggestions, support and help. They are Prof. Ji Wei of University of Missouri-Kansas City Xue Li, Jianrui Zheng and Lingmei Huang of the Beijing Normal University Shiwu Gao, Gongying Yuan, Zhihua Yang and Zailan Yang of the Beijing Landscape Administration Liyuan Cui of the Chinese Academy of Forestry Jinzeng Wang of the Beijing Forestry Survey and Design Institute and Wenji Zhao, Lin Zhn and Zhaoning Gong of the Capital Normal University.
文摘The decision tree and the threshold methods have been adopted to delineate boundaries and features of water bodies from LANDSAT images. After a spatial overlay analysis and using a remote sensing technique and the wetland inventory data in Beijing, the water bodies were visually classified into different types of urban wetlands, and data on the urban wetlands of Beijing in 1986, 1991, 1996, 2000, 2002, 2004 and 2007 were obtained. Thirteen driving factors that affect wetland change were selected, and gray correlation analysis was employed to calculate the correlation between each driving factor and the total area of urban wetlands. Then, six major driving factors were selected based on the correlation coefficient, and the contribution rates of these six driving factors to the area change of various urban wetlands were calculated based on canonical correlation analysis. After that, this research analyzed the relationship and mechanism between the main driving factors and various types of wetlands. Five conclusions can be drawn. (1) The total area of surface water bodies in Beijing increased from 1986 to 1996, and gradually decreased from 1996 to 2007. (2) The areas of the river wetlands, water storage areas and pool and culture areas gradually decreased, and its variation tendency is consistent with that of the total area of wetlands. The area of the mining water areas and wastewater treatment plants slightly increased. (3) The six factors of driving forces are the annual rainfall, the evaporation, the quantity of inflow water, the volume of groundwater available, the urbanization rate and the daily average discharge of wastewater are the main factors affecting changes in the wetland areas, and they correlate well with the total area of wetlands. (4) The hydrologic indicators of water resources such as the quantity of inflow water and the volume of groundwater are the most important and direct driving forces that affect the change of the wetland area. These factors have a combined contribution rate of 43.94%. (5) Climate factors such as rainfall and evaporation are external factors that affect the changes in wetland area, and they have a contribution rate of 36.54%. (6) Human activities such as the urbanization rate and the daily average quantity of wastewater are major artificial driving factors. They have an influence rate of 19.52%.
基金National Key R&D Program of China,No.2017YFC0506506,No.2016YFC0500206National Natural Science Foundation of China,No.41501484
文摘Ecosystem services have become one of the core elements of ecosystem management and evaluation. As a key area of ecosystem services and for maintaining national ecological security, ecosystem changes and implementation effect evaluation are important in national key ecological function zones, for promoting the main function zone strategy and for improving the construction of an ecological civilization. This article studies the ecological zone of a tropical rainforest region in the central mountain area of Hainan Island, China. Multi-source satellite data and ground observation statistics are analyzed with geo-statistics method and ecological assessment model. The core analysis of this paper includes ecosystem patterns, quality and services. By means of spatial and temporal scale expansion and multidimensional space-time correlation analysis, the trends and stability characteristics of ecosystem changes are analyzed, and implementation effect evaluation is discussed. The analysis shows a variety of results. The proportion of forest area inside the ecological zone was significantly higher than the average level in Hainan Island. During 1990–2013, settlement gradually increased inside the ecological zone. After implementation of the zone in 2010, human activity intensity increased, with the main land use being urban construction and land reclamation. Water conservation in the ecological function zone was higher than that outside the zone. In general, it increased slightly, but had obvious fluctuations. Soil conservation inside the zone was also better than that outside. However, it demonstrated dramatic fluctuations and relatively poor stability during 1990–2013. The human disturbance index inside the zone was significantly lower than that outside, and had a lower biodiversity threat level. Especially in 2010–2013, the increased range of the human disturbance index inside the zone was significantly less than that outside.
基金supported by the Chinese Academy of Sciences Action Plan for West Development Project (Grant No. KZCX2-XB3-15)the National High-tech R&D Program of China (Grant No. 2012AA12A304)
文摘It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.