最新刊期
卷 18 ， 期 4 ， 2014
- 摘要：<正>尺度问题随着研究对象而变化。海量、多时空尺度的对地观测数据,为地理科学提供了地理大发现以来极为重要的机遇,若不解决尺度问题,必将影响地球科学研究的进一步推进。2013年9月,李小文院士发表论文《定量遥感尺度效应刍议》,试图推动解决遥感在定量研究和应用过程中遇到的尺度效应问题。论文
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发布时间：2021-06-10 - 摘要：The inversion of the forest vertical structural parameters is the basis of forest resource management,forest volume estimation,and global carbon cycle studies. However,very limited research has been conducted regarding forestry applications. With the increasing development of Interferometric Synthetic Aperture Radar（ InSAR） /Polarimetric Interferometric Synthetic Aperture Radar（ Pol-InSAR） techniques,Tomographic Synthetic Aperture Radar（ TomoSAR） has been widely considered suitable for the inversion of the forest vertical structural parameters. TomoSAR is a new technique introduced to remote sensing applications,particularly for the remote sensing of land covers with complex three-dimensional structures,such as forests and urban areas. This study mainly aimed to summarize the new developments and applications of TomoSAR in extracting information regarding vertical forest structures. Three approaches can be used to extract information regarding vertical forest structures: Polarization Coherence Tomography（ PCT）,Multi-baseline Interferometric TomoSAR（ MB-InTomoSAR）,and multi-baseline polarimetric TomoSAR（ MB-PolTomoSAR）. In PCT,forest vertical profile is obtained using Fourier-Legendre expansion series with a priori knowledge,such as forest height and topographic phase estimated with polarimetric interferometric information or Lidar. With this approach,the profile of vertical forests with two tracks in a repeat-path mode can also be extracted. In MB-InTomoSAR technique,information regarding forest vertical structures can be obtained by multi-baseline interferometric SAR images in a repeat-path mode with low temporal and spatial decoherence. MB-InTomoSAR can be used to estimate the vertical parameters of forests in a physical model. Along with spectral analysis method,MB-InTomoSAR can also be used to extract vertical forest information. In MB-PolTomoSAR technique,the vertical structural parameters of forests are determined using multi-baseline polarimetric interferometric SAR images in a repeat-path mode. MB-PolTomoSAR can be used to obtain not only forest height,forest aboveground biomass,and other forest vertical structural parameters but also variation in scattering mechanisms in vertical forests. In this study,the principles and methodologies of these three TomoSAR techniques were described. The application status and developments of TomoSAR technique were summarized. TomoSAR was used to extract the vertical structural parameters of forests. Afterward,this technique was evaluated.This study also described further advances in TomoSAR applications for the vertical structural parameters of forests. TomoSAR was applied to extract information regarding forest vertical structures. Our results indicated that TomoSAR could be a suitable technique in studying forests with large slopes or complex topographic characteristics.关键词：tomographic synthetic apeture radar;polarimetric interferometric synthetic aperture radar;forest vertical structure parameters;forest height;forest above ground biomass
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发布时间：2021-06-10 - 摘要：Tree crowns are usually simulated as basic geometrical shapes in geometric-optical models. However,the selection of specific shape often based on visual judgment and may induce uncertainties,and the uncertainties would propagate to the practical application of the model,retrieving Leaf Area Index（ LAI）,for example. This study aimed to address the potential effect of crown shape by conducting a simulation experiment. In this study the Nilson’s gap probability model was enhanced to ensure compatibility with commonly encountered crown shapes,such as ellipsoid,cone and cone + cylinder. The enhanced Nilson’s gap probability model can be used to calculate volumes and projected area profiles of the three shapes. This enhanced model was then compared with a gap probability model derived from Beer’s Law. Clumping index was then formulated. This can be described as a function of canopy structure parameters,such as crown volume,projected area,and stem density. On the basis of the enhanced Nilson’s gap probability model and formulated clumping index,we analyzed the sensitivity of gap probability,clumping index,and LAI retrieval to crown shape. In this study,the gap probability was found sensitive to crown shape. This result could be attributed to the volumes and projected areas of different crown shapes. A high difference in gap probabilities was observed between various crown shapes in the middle of the canopy. Below the canopy,crowns with ellipsoid and cone + cylinder shapes exhibited very similar（ relative error< 9. 7%） gap probabilities. By contrast,these gap probabilities were very different from those of cone-shaped crown（ largest relative error > 36. 7%）. Our results further showed that clumping index is a function of crown shape. Similar to gap probability,the clumping indexes of crowns with ellipsoid and cone + cylinder shapes were very similar below the canopy. By contrast,these indexes differed from those of cone-shaped crown. Hence,crown shape should be considered when LAI is retrieved using ground measurements. Relative error likely reached > 25% if crowns were set in wrong shapes. Gap probability and clumping index underneath the canopy were very similar when crowns were modeled in ellipsoid or cone + cylinder shapes; however,a considerable difference was observed if crowns were modeled in a cone shape. The volumes and projected areas of different crown shapes could be a ccounted for similarities or differences in results. Based on the retrieved LAI,crown shapes could account for 25% of the relative retrieval error. Therefore,crown shapes should be carefully specified to obtain a satisfactory result. Our analysis results were d erived from simulation experiments; in our future work,ground experiments would be performed to verify our conclusions.关键词：crown shape;gap probability;clumping index;leaf area index
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发布时间：2021-06-10 - 摘要：High-resolution satellite images provide extensive spectral,shape,and textural information of ground objects; as such,these images have been widely used in many fields. As by products of images,shadows affect the visual interpretation and automatic identification of landscape objects. Nevertheless,shadows reveal additional useful information,such as shape,height,surface characteristics,and relative position of targets. Therefore,studies should be conducted to develop methods for detecting shadows.To extract shadows accurately,researchers should consider the necessary pre-conditions; such methods should also be readily available for further utilization. This study proposed a shadow detection method based on object-oriented method and established characteristic components for high-resolution satellite images. To analyze the spectral characteristics of shadows,we determined several components,such as color invariant C3,brightness I,first principal component（ PC1）,and RATIObnir. We then used these components to highlight shadow areas in images. RATIObnirindex,which can be used to distinguish shadow and water efficiently,was d eveloped by considering the Rayleigh scattering of different wavelengths in shadow and non-shadow areas. However,such c omponents are difficult to analyze comprehensively because different construction methods have revealed various value ranges. To overcome this problem,we used a linear normalization method and transformed the pixel values of images in the same range of 0 to1. Object-oriented method,which comprised segmentation and information extraction,was used to extract shadow areas in the enhanced images. Brightness I and PC1,which contained relatively clear boundary information,were chosen as the main data source for multi-resolution segmentation based on the characteristics of high-resolution images. C3and RATIObnirindices were also used the main data source in the subsequent classification. Several characteristics,such as mean value,maximum difference,standard deviation,area,and gray-level co-occurrence matrix,indicated the difference between shadow and non-shadow objects; as such,these characteristics were selected to extract shadow areas from images. Shadows in 20 QuickBird images were extracted using the proposed method and two contrast experiments. Data revealed that the average total accuracy of the proposed method was 97%,the average producer accuracy was 96%,and the average Kappa index was 0. 94. The combined characteristic component-based and object-oriented methods could be used to obtain shadows with perfect shapes but without fragmentation compared with pixel-based method. The combined method also exhibited higher accuracy than the object-oriented method based on original optical i mages alone. Considerable experiments and statistically high-precision results of the proposed method showed that the combined characteristic component-based method and object-oriented method could be used efficiently to enhance the contrast of shadows a gainst other features. Furthermore,this combined method could be used to ensure the complete extraction of shadow areas. The proposed method could be applied not only to QuickBird imagery used as test data in this study but also to other high-resolution satellite images.关键词：shadow extraction;characteristic component;object oriented;spectral characteristic;color invariant index
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发布时间：2021-06-10 - 摘要：The Aerosol Optical Depth（ AOD） retrieval algorithm for sand-dust weather over ocean is investigated u sing FY-3A /Medium Resolution Spectral imager（ MERSI） based on aerosol modes in the MODIS C005 over-ocean algorithm. The AOD（ 550 nm） retrieved from MERSI is evaluated with MODIS AOD product（ MOD04）. Results show a systematic bias in this algorithm. Further analyses reveal that this bias results from the MODIS-available aerosol modes. Therefore,a sand-dust aerosol mode is adopted to modify the MODIS aerosol modes by mixing them at an appropriate ratio. AOD is retrieved a second time based on the modified aerosol modes,and the corresponding results exhibit good consistency with MOD04,indicating that modified aerosol modes are more appropriate for the AOD r etrieval from MERSI for sand-dust weather over ocean.关键词：FY-3A/MERSI;aerosol mode;sand-dust;Aerosol Optical Depth（AOD）
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发布时间：2021-06-10 - 摘要：The importance of the extraction and cognition of geo-information has been increasingly highlighted in the face of the massive accumulation of remote sensing data and the lack of application information. According to the geo-informatics Tupu methodology regarding the visual cognitive process,Tupu-cognition can automatically interpret remotely sensed imagery. In this study,using a unified framework of geographic information systems,we extract the features of images step by step. Spatial-spectrum a nalysis is then executed in the geo-cognitive process described as "Perceive-Identify-Confirm ". Algorithms like multiscale s egmentation,feature analysis,and supervised learning are invoked to meet the application’s requirements for automation and intelligence. In the cognitive application of land-cover information,we first establish the mechanism of prior knowledge management for automation. Second,a number of machine learning algorithms are employed to improve the intelligence. Finally,adaptive iteration is introduced to optimize the results. The data selected for this classification experiment are Advanced Land Observing Satellite（ ALOS） multispectral images in the Pearl River Delta. The land cover results are consistent with expectations and illustrate the f easibility of our method.关键词：Tupu-cognition;automatic interpretation;land cover;automatic classification
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发布时间：2021-06-10 - 摘要：An algorithm for modeling bidirectional reflectance anisotropies of land surfaces has been developed as a surrogate for the operational MODIS Bidirectional Reflectance Distribution Function（ BRDF） and albedo product for user community. This algorithm is a set of kernel-driven BRDF models extensively used in several space-borne remotely sensed BRDF /albedo products. A mong these models,RossThick（ RT）-LiSparseR（ RTLSR） has been selected as the current operational MODIS BRDF /albedo a lgorithm. However,the hotspot effect has not been considered in RT kernel. As such,the use of an RTLSR model underestimates hotspot reflectance,thereby influencing the accuracy of the retrieval of vegetation structures,such as clumping index. On the basis of Bréon’s hotspot factor,Maignan corrected RT kernel to generate a RTMaignan（ RTM） kernel. For producers,a 13-year MODIS BRDF /albedo product is reprocessed using this corrected model,but this task is time consuming. For users,the direct use of this corrected model for MODIS observations is complicated because the equivalent inputs of the operational RTLSR algorithm are not easily available. In this study,a method was developed to correct the hotspot effect for the operational MODIS BRDF product,which is available for users. Based on the effective validation using POLDER-3 /BRDF data and the selected MODIS data,this study shows that（ 1） an improvement of approximately 10. 12% of relative error between our method and the RTLSR model can be obtained by estimating the hotspot reflectance;（ 2） a relative error of approximately 2. 10% occurs between this method and the RTM-LiSparseR（ RTMLSR） model,but this difference is not significant;（ 3） relative error reaches approximately 4. 99% between this method and the RTLSR model to simulate NDHD but decreases to approximately 1. 32% between this method and the R TMLSR model.关键词：kernel-driven BRDF models;AMBRALS;BRDF;hotspot;MODIS BRDF/albedo product
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发布时间：2021-06-10 - 摘要：Soil-adjusted Vegetation Indexes（ SAVIs） have been developed to eliminate the effect of soil background on Vegetation Indices（ VIs）. The soil-adjusted power of VIs varies with environment conditions. After summarizing the development of SAVI family,we compared and evaluated NDVI,SAVI,TSAVI,MSAVI,OSAVI,and GESAVI in terms of their resistance to soil variations over a series of Leaf Area Indices（ LAI）. Two datasets in use were simulated through PROSAIL model. The optimal application conditions of these VIs were noted. Based on the signal-to-noise ratio,these six VIs are classified into three categories. OSAVI and TSAVI can adjust soil noise betterly when applied to uniformly distributed canopy with intermediate-low LAI. MSAVI is more stable in the expression of vegetation information when LAI or vegetation species is heterogeneous. Analysis results based on M ODIS-VI and MODIS-LAI products over corresponding canopy preliminarily validates our conclusion.关键词：prosail model;vegetation index;soil background;ability comparison;optimal environment
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发布时间：2021-06-10 - 摘要：For a vegetation-covered area,a Normalized Difference Vegetation Index（ NDVI） is widely applied in drought monitoring by remote sensing. Compared with vegetation index based on optical remote sensing,the proposed Microwave Vegetation I ndex（ MVI） provided additional information on vegetative growth. Temperature microwave vegetation index（ TMVDI） was also developed using MVI based on Temperature Vegetation Dryness Index（ TVDI） instead of NDVI. In the present study,drought that affected Sichuan province in the summer of 2006 was observed. Drought monitoring results based on TMVDI and TVDI were compared and then analyzed. We particularly compared the monitoring results obtained by remote sensing with those based on the standardized precipitation index established from the precipitation observation data of meteorological observatory to evaluate monitoring accuracy. These results also show that TMVDI,which is calculated on the basis of low-frequency microwave radiometer d ata（ descending pass）,is considered as the most suitable index that can be used to monitor drought in vegetation-covered areas.关键词：drought monitoring via remote sensing;microwave vegetation index;temperature vegetation dryness index;AMSR-E;Sichuan province
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发布时间：2021-06-10 - 摘要：Remote sensing has become an important exploratory method for the national census of traditional Chinese medicinal resources. We selected safflower（ Latin name: Carthamus tinctorius L.） as a sample species of cultivated Chinese medicinal plant species. We extracted textures from ZY-3 satellite images based on fractal theory and Gray Level Co-occurrence Matrix（ GLCM）methods to assist the supervised classification. Results showed that the overall accuracy increased by 0. 49% to 5. 31%. Kappa coefficient increased by 0. 01 to 0. 07 after textures were combined for classification processing. Accuracy with fractal-based textures improved at least twice as much as GLCM-based textures,particularly when fractal-based texture was extracted with a 5 × 5 sliding block in Matlab and then added. The classification accuracy of safflower increased to 100% when this parameter was combined with fractal-based textures; by contrast,this accuracy reduced by 0. 55% to 1. 28% with GLCM-based textures. Moreover,the s amples collected from the final recognition results based on fractal theory were relatively complete with a smaller degree of fragmentation and a higher distinction from other categories. Therefore,fractal-based textures can be used to assist in the recognition of cultivated Chinese medicinal plants. Textures based on fractal theory could effectively increase the classification accuracy of ZY-3 images at a higher extent than those based on GLCM.关键词：cultivated Chinese medicinal plant;safflower（Carthamus tinctorius L.）;texture;fractal theory;Gray Level Co-occurrence Matrix（GLCM）;ZY-3 satellite
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发布时间：2021-06-10 - 摘要：It is difficult to evaluate and predict soil erosion and its related effects in mountainous areas without sufficient observation data. This study aimed to estimate and predict changes in soil erosion using137Cs,RS,and GIS techniques and propose an a pproach for soil erosion evaluation in mountainous areas. Using the erosion modulus calculating models based on137Cs concentration,the annual average soil erosion modulus of forest lands,shrub lands,grasslands,farmlands,and uncovered land were obtained. The values were 356—1531 t /（ km2·a）,330—1709 t/（ km2·a）,886—3885 t/（ km2·a）,5197—12454 t/（ km2·a）,and more than 1 5000 t /（ km2·a）,respectively. Then,erosion zoning was done by combining erosion rates and land use data by interpreting remote sense images from 1987（ Landsat TM）,1995（ Landsat TM）,and 2005（ Landsat ETM）,and these were overlaid with 1∶ 50000 DEM data. The results showed that the eroded land changed very little from 1987 to 2005,accounting for about66% —67. 3% of the total; however,the erosion intensity significantly rose from 1987 to 1995,up to 30% for some land use types. The eroded land, with the erosion modulus of 2500—5000 t /（ km2·a）,5000—8000 t/（ km2·a）, and 8000—15000 t /（ km2·a） rise 30%,23%,and 26%,respectively. The soil erosion amount in the Xiaojiang River basin was 7.51 ×106t / a,8. 19 × 106t /a,and 8. 18 × 106t /a in 1987,1995,and 2005,r espectively. Moreover,the zoning and amount of soil erosion for 2015 was predicted using a Markov-Cellar A utomata Model,which was established using the data from 1995 and 2005. The predicted result,8. 17 × 106t /a,was very similar to that from 2005. This study provides a valuable solution to evaluate and predict soil erosion for mountainous areas in southwest China.关键词：Soil erosion;estimation;prediction;137Cs;RS;GIS;Xiaojiang River basin
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发布时间：2021-06-10 - 摘要：Salinity is a basic property of natural water. Therefore,assessing this property is relevant. Measuring salinity by using optical remote sensing data provides the advantages of spatial coverage and high spatiotemporal precision of currently available highresolution satellite data. Full-resolution images from a medium-resolution imaging spectrometer were used to explore the f easibility of measuring the low salinity of a lake based on ocean color data. Bosten Lake was selected as the study area for this r esearch. The study was carried out by establishing the empirical relationship between salinity and Colored Dissolved Organic M aterial（ CDOM）absorption coefficients. We focused on different areas of the lake on April 27,2011 and in the whole lake for an entire year from June 2010 to June 2011,in which the day of April 27,2011 is the flood day of the Kaidu River. Salinity data were acquired by using YSI-6600 and in situ sampling and combining the data gathered by the researcher. CDOM absorption coefficients were obtained by using BEAM 4. 10. 3 software. The salinity of southwestern Bosten Lake,which is dominated by the Kaidu River,exhibits an inverse relationship with CDOM absorption coefficients; however,no significant correlation is observed. The relationships between CDOM absorption coefficients and salinity vary in space and time in Bosten Lake,which is similar to other study a reas. The salinity of Bosten Lake is lower than 3 g·L- 1,and the root mean square error of measuring salinity from a satellite in space is approximately 1. 1 practical salinity units. The errors are nearly close to the salinity value of the lake,thus denoting that they are too large for estimating the salinity of Bosten Lake by using optical remote sensing data. Thus,measuring the salinity of Bosten Lake by using optical remote sensing data is difficult. Because the considerable heterogeneities observed from the relationships between CDOM absorption coefficients and salinity at different times and areas have no significant correlation,and the error of the salinity calculated by optical remote sensing data is too large. Measuring water salinity by using optical data requires that water must possess sufficient salinity and has both salinity and CDOM gradients. Moreover,CDOM conservative mixing must also be satisfied. These conditions make monitoring the low salinity of a lake difficult.关键词：salinity;CDOM;MERIS;Bosten Lake
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发布时间：2021-06-10 - 摘要：Studies on the patterns of temperature changes with elevation have important implications for constructing the microscale temperature of mountain areas and for practical applications in agriculture,forestry,prevention and control of natural disasters,and ecosystem management. Long-term observation data and instrument data logging based on the ground meteorological network are the most conventional methods for obtaining temperature change patterns along the elevation gradient. However,limited by the number of meteorological stations and insufficient coverage over large geographical regions,the observed and recorded results are easily distorted by accidental factors. This implies that the results may be inadequate for constructing spatial distribution models of land surface temperatures in synchronized time phases for contiguous microscale mountain environments over large r egions. Choosing Yunnan Province as the study area,this paper endeavored to detail mountainous temperatures with elevation changes across different spatial scales using the Instantaneous Land Surface Temperature（ ILST） and Digital Elevation Model（ DEM）. First,a raster of ILST was retrieved from thermal infrared bands of Moderate Resolution Imaging Spectroradiometer（ MODIS） using the split-window algorithm. Second,the mean temperature data for November from three decades recorded at c onventional meteorological stations were used to calibrate the remotely sensed ILST to attain a raster of the temperature. Third,the effects of latitude changes,changes in slope drop,slope aspect,water body and latitudinal variations were eliminated or r educed. Then,the Temperature Lapse Rates（ TLRs） with elevation for the entire Yunnan province and for different types of mountain landforms and slope aspects were calculated using random sampling,spatial division and statistical regression. The results i nclude:（ 1） after reducing or eliminating the effects of aspect,slope,longitude,latitude and other microterrain factors,TLR of e levation was 0. 53℃ at the entire regional scale.（ 2） TLR increased gradually from the high to low mountain area at the local r egional scale of typical landforms. TLR was0. 47℃ in the alpine region of northwest Yunnan,0. 51℃ in the middle mountainous region of central and eastern Yunnan,0. 54℃in the low mountainous region alone the southern border of Yunnan,and 0. 54℃ in the alpine canyon region of northwest Yunnan and river valley region of southern Yunnan.（ 3） TLR increased from sunny to shady slope: 0. 52℃ on sunny slope,0. 54℃ on semi-shady slope,and 0. 55℃ on shady slope. The zonal patterns in mountain temperature changes,acquired by retrieving the instantaneous land surface temperature based on the thermal infrared bands in MODIS images,complement the constraints of unavailable synchronized data in conventional methods. Through statistical computation of TLRs,the zonal patterns of temperature changes at different spatial scales can be acquired in detail. Elevation is the main factor affecting mountain temperature,and it demonstrates outstanding geographical patterns in relation to temperature. In addition to elevation,other microterrain factors,such as aspect and slope are also affecting mountainous temperatures in micropatterns,and this needs to be further researched. It is a relatively new method to research into the laws of temperature change in the mountain regions with DEM and ILST using remotely sensed data.关键词：raster of remotely sensed instantaneous land temperature;mountain temperature;lapse rate;mountain landforms
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发布时间：2021-06-10 - 摘要：Canopy Nitrogen Concentration（ CNC） is a key indicator of crop yields. It is feasible to establish a realtime regional model to estimate CNC by upscaling the field-scale spectral model. This study focuses on monitoring the CNC in rice on a large scale in real-time. The Random Forest（ RF） algorithm is used to establish the CNC spectral i nversion model,and some vegetation indexes that are sensitive to nitrogen were selected as input parameters for the RF. CNC was selected as an output parameter. The hyperspectral and biochemical data were collected in a paddy in Changchun City,Jilin Province,China,and the data in Suzhou was used to test the model’s universality and effectiveness. Two regional-scale models were developed by applying scale transformation based on the input and output variables respectively. The results show that the RFCNC model（ CNC spectral inversion model based on the RF algorithm）performed accurately and significantly improved upon existing methods. R2,used to validate method accuracy in Changchun and Suzhou,was 0. 82 and 0. 73 respectively. The regional application accuracy increased（ R2= 0. 81）through the two upscaling methods using hyperspectral remote sensing satellite images. This study suggests that this method is promising for estimating regional CNC in rice by upscaling a field-scale spectral model if the strategy is a ppropriately selected.关键词：random forest algorithm;nitrogen inversion model;upscaling;regional application
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发布时间：2021-06-10 - 摘要：This study aims to evaluate the ecological restoration of Wenchuan County after the Wenchuan Earthquake in 2008,and to provide support for further ecological restoration and reconstruction. Simultaneously,this study also focuses on applying remote sensing and Geographic Information System（ GIS） technologies to evaluate the ecological environment. Wenchuan County,which was the epicenter of the May 12,2008 earthquake,was selected for this research,which involved multi-source r emote sensing data and other supporting statistical data. An eco-environmental quality evaluation index system was established based on the pressurestate-response framework. The analytic hierarchy process method was used to calculate index weight. The eco-environmental qualities of Wenchuan County in 2007,2008,and 2013 were evaluated by using the comprehensive index method. The results for the eco-environmental quality evaluation of Wenchuan County in 2007,2008,and 2013 were obtained. Data gathered on the eco-environmental quality of Wenchuan in 2008 were compared with those obtained in 2007,i. e.,before the earthquake. Data on the e co-environmental quality recovery gathered in 2013 were also compared with the data in 2007（ i. e.,before the earthquake） and2008（ i. e.,after the earthquake）. The result of the analysis showed that 79. 4% of Wenchuan County exhibited good eco-environmental quality in 2007. However,the eco-environmental quality of the county was severely damaged by the 2008 earthquake. In particular,the areas near the epicenter suffered from serious destruction. Five years after the earthquake（ 2013）,the e co-environmental quality of Wenchuan County has been successfully restored. In particular,55. 84% of the regional eco-environmental quality of the county has significantly improved compared with that in 2008. The eco-environmental quality of poor regions in the county has also exhibited an obvious improvement. However,the eco-environmental quality in some regions in the county has not fully recovered. Evaluating and analyzing the eco-environmental quality of Wenchuan County in 2007,2008,and 2013 are feasible by using remote sensing and GIS technologies. Such approaches help determine the space distribution of the eco-environmental quality of Wenchuan Earthquake and evaluate its recovery. This study offers several useful recommendations on protecting and restoring the ecological environment that can be applied in the future.关键词：Wenchuan earthquake;ecological recovery;evaluation;pressure-state-response framework;analytic hierarchy process
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发布时间：2021-06-10 - 摘要：The 8. 0 MsWenchuan Earthquake in 2008 significantly damaged the local ecosystem of Sichuan Province. In this study,high spatial resolution airborne remote sensing images,spaceborne remote sensing data,and field investigations were used to monitor and analyze agriculture and forestry recovery in Sichuan Province in the five years after the earthquake. The remote sensing i mages were acquired from the"Wenchuan 5th Anniversary"flight campaign organized by the Institute of Remote Sensing and Digital Earth,Chinese Academy of Sciences. For the agricultural aspect,visual interpretation by using high-resolution airborne i mages acquired from 2008 to 2013 and expert experience were used to determine the status of damaged cultivated areas and to e valuate their recovery.Crop type proportions were collected through ground surveys by using a GVG（ GPS,Video,and GIS） i nstrument over a sampled area,and then,interpolated for regions that were not surveyed. Results revealed that only 17. 5% of the 1592 ha damaged arable land could be cultivated five years after the Wenchuan Earthquake. Nearly all usable arable land was cultivated and the cropping structure did not evidently fluctuate after the earthquake. The enthusiasm of local farmers toward their craft was not affected by the u nprecedented disaster. This study recommends that the cropping structure must be kept essentially constant to ensure the supply of food in the disaster area. For the forestry aspect,the recovery of three key areas（ which are distributed in the dry valley of the M injiang River area and the montane around the Sichuan Basin area） was monitored via visual interpretation of airborne images. The damage and the recovery status of the entire disaster area were assessed by conducting a time-series change analysis of the normalized difference vegetation index with data from the Moderate-Resolution Imaging Spectroradiometer（ MODIS）. The results showed that the recovery status of forests in the key areas is relatively good,given that shrubs and young d eciduous trees are g erminating in most parts of the forests that were destroyed by landslides and mud-rock flows. However,some severely destroyed areas with large slopes and areas that were frequently struck by secondary disasters are still encountering difficulties. In summary,the 46400 ha seriously damaged and the 177000 ha moderately damaged forest areas have fully recovered by 13. 52% and 25. 84%,respectively,and both have partly recovered by approximately 50%. Some severely destroyed areas,which mainly include the f orest areas around Chaping Mountain,require physical intervention to accelerate recovery. A change analysis can directly indicate the damage and recovery status of croplands and forests by using high-resolution airborne images. The airborne remote sensing sensor will continue to play an important role in monitoring ecosystems and in assessing important natural disasters. Meanwhile,a time series analysis can monitor damage and recovery of forests at a large scale by using MODIS data.关键词：Wenchuan earthquake;agriculture and forestry recovery;airborne high-resolution remote sensing images;visual i nterpretation;change detection
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发布时间：2021-06-10 - 摘要：<正>HJ-1A助力中国拟新建南极科学考查站选址HJ-1A satellite help China to set new Antarctic research station中国拟在南极维多利亚地区建立一座新的科学考察站,但是国内科学家对该地区情况了解很少。针对这一难题,北京师范大学全球变化与地球系统科学研究院采用国产卫星HJ-1A于2010年11月拍摄的遥感影像,对该地区进行遥感综合调查,并建议难言岛作为预选站址（封面图片右下角为该岛的WorldView-2高分辨率影像）。调查发现,该地区地貌十分独特,分布着6大陆上冰川,巨大的德里加尔斯基冰舌长约120km,阻挡了南面漂浮过来
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发布时间：2021-06-10
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