Forest fires in mountainous areas can cause severe defores-tation which can potentially trigger secondary natural hazards like debris falls and avalanches. We documented an extreme case study for the range of possible...Forest fires in mountainous areas can cause severe defores-tation which can potentially trigger secondary natural hazards like debris falls and avalanches. We documented an extreme case study for the range of possible post-fire land cover （LC） dynamics. We investigated a 15-ha, steep （10°-65°） burnt slope in Styria （Austria） at elevation of 760-1130 m, which burned in 1946 and has not fully recovered to date. Seven 8-class legend LC maps were produced （1954, 1966, 1973, 1982, 1998, 2004, 2009） and integrated in a vector-based GIS, mainly by on-screen interpretation of aerial photos. Our aim was to clarify how post-wildfire LC dynamics take place on a severely damaged, steep slope and to give a basic projection of the future vegetation recovery process. The pre-fire Pinus sylvestrisstands have been mainly replaced by Picea abies and Larix decidua. Regeneration proceeded mainly from the base of the slope upwards. All tree species together still cover no more than 40% of the slope after more than 60 years of recovery, while grassland communities and rock/debris areas have expanded. Multitemporal analysis showed a slow but steady increase in woodland cover. Degraded rock/debris areas, however, expanded as well because soil erosion and related debris flows remained active. Slope angle （with a threshold value of approx. 35-40°） seemed to control whether erosion or regeneration prevailed. According to a simple extrapolation, the slope will not reach its former condition before 2070. This extreme disturbance window of more than 120 years is owed to the steepness of the slope and to the shallow soils on dolomitic bedrock that were severely damaged by the fire. The neglect of any game fencing is a further factor slowing regeneration.展开更多
Research on macroinvertebrate community structure in Andean rivers has been oriented towards describing patterns of alpha and gamma diversity by taking into account environmental predictors at local spatial scales(e.g...Research on macroinvertebrate community structure in Andean rivers has been oriented towards describing patterns of alpha and gamma diversity by taking into account environmental predictors at local spatial scales(e.g.,micro-and mesohabitats).However,the patterns of beta diversity and the importance of landscape-scale variables have been evaluated to a lesser extent.The objective of this study was to describe the patterns of alpha and beta diversity of benthic macroinvertebrates in the Andean rivers of the Orinoco basin and their relationship with local and landscape environmental variation.A stratified random sampling of macroinvertebrates was carried out at 40 sites(comprising an altitudinal range of between 500 and 2900 m.a.s.l.),local and landscape variables were measured.Our results showed that the variation of alpha diversity was influenced by local and landscape variables,which are directly and indirectly related to the contribution of sediments,substrate composition and flow velocity,providing a heterogeneity of habitats.Global beta diversity was explained by the combined effect of local and landscape variables.Regarding the beta diversity phenomena,turnover was predominant while nestedness presented a minor contribution and both were explained in greater proportion by local descriptors and some landscape variables,specifically those of a geomorphological nature.Our results concur with the view of an environmental and spatial hierarchy within the river habitat and highlight the influence of multiple scales on macroinvertebrate diversity.The above suggests that both local and landscape scales must necessarily be considered for environmental management and the conservation of Andean lotic ecosystems.展开更多
<div style="text-align:justify;"> With global warming and increased human activity, more and more ground surface areas have been affected, which leads to the creation of many problems. To understand th...<div style="text-align:justify;"> With global warming and increased human activity, more and more ground surface areas have been affected, which leads to the creation of many problems. To understand the ecological environment changes in a typical alpine region, information on landcovers changes in the study area from 2000 to 2020 was obtained by combining remote sensing, geographic information system, and traditional statistical analysis for the Sanjiangyuan National Nature Reserve on the Qinghai-Tibet Plateau, China. The results show that the changes of surface cover in Sanjiangyuan National Nature Reserve are relatively concentrated, mainly distributed in the sections of south, northwest, central, and northeast, with the area of the changed regions and the unchanged regions being 31,127.45 km<sup>2</sup> and 271,941.37 km<sup>2</sup>, respectively. The transformation between the various types of ground landcover is mainly characterized by a shift from other types to grassland and from grassland to bare land. And the regions of change are mostly concentrated between 3500 - 4600 m in elevation. </div>展开更多
An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those obs...An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those observed in the late summer and early autumn of 1973, 1977, 1993 and 1995. As a parameter of land-cover, SAVI (Soil Adjusted Vegetation Index) derived from the data of Landsat MSS and JERS-1 OPS (Optical Sensor) is used. The result indicates the increase of vegetation in the oasis areas, confluent area of the Yarkant and Kashgar Rivers and around reservoirs while little change occurs in the desert area. The 1973 satellite image shows the abundant flow in the Yarkant River while the river is almost dried up in the satellite images of later years. The trend of the decrease in the Hotan River flow is recognized although not so dramatic as that of the Yarkant River.展开更多
Objectives:(1)To evaluate how ecosystem services may be utilized to either reinforce or fracture the planning and development practices that emerged from segregation and eco-nomic exclusion;(2)To survey the current st...Objectives:(1)To evaluate how ecosystem services may be utilized to either reinforce or fracture the planning and development practices that emerged from segregation and eco-nomic exclusion;(2)To survey the current state of ecosystem service assessments and synthesize a growing number of recommendations from the literature for renovating ecosys-tem service analyses.Methods:Utilizing current maps of ecosystem service distribution in Bushbuckridge Local Municipality,South Africa,we considered how a democratized process of assessing ecosys-tem services will produce a more nuanced representation of diverse values in society and capture heterogeneity in ecosystem structure and function.Results:We propose interventions for assessing ecosystem services that are inclusive of a broad range of stakeholders'values and result in actual quantification of social and ecological processes.We demonstrate how to operationalize a pluralistic framework for ecosystem service assessments.Conclusion:A democratized approach to ecosystem service assessments is a reimagined path to rescuing a poorly implemented concept and designing and managing future social-ecological systems that benefit people and support ecosystem integrity.It is the responsi-bility of scientists who do ecosystem services research to embrace more complex,pluralistic frameworks so that sound and inclusive scientific information is utilized in decision-making.展开更多
In 1965, the first forest map of Lebanon was produced. It is the oldest spatial distribution representation of junipers. Landcover maps of 2002 and 2010 are the most detailed spatial distribution that spatially shows ...In 1965, the first forest map of Lebanon was produced. It is the oldest spatial distribution representation of junipers. Landcover maps of 2002 and 2010 are the most detailed spatial distribution that spatially shows forests. Juniper forests are found in Lebanon as mainly as clear to low density coverage. High-density juniper forests are rarely found and only on Mount-Lebanon. Juniper forests are also mixed with oaks on the Eastern flank of Mount-Lebanon. Mapping juniper forests have demonstrated high degree of complexity, especially because of their low density and being mixed. The spatial representation of juniper forests was compared between the 1965 forest map and the landcover maps of 2002 and 2010. GIS environment was used to extract juniper forests from all maps. The degree of matching between juniper forests was investigated regarding the total area and spatial overlapping. Juniper forests were examined to their spatial locations, comparing the three maps. Spatial changes and anthropogenic effect were obtained, using Google Earth facilities. Google earth had satellite images acquired since 2014. Landcover maps of 2002 and 2010 have spatially matched forest map of 1965 by about 90% and 50% respectively. Spatial coverage of juniper forests were about 12,000, 26,000 and 28,000 ha on the 1965 forest map, landcover maps of 2003 and 2010 respectively. Anti-Lebanon juniper forests were not well represented on both landcover maps. Anthropogenic activities were mainly agriculture that affected juniper forests. Cultivations have replaced about 2% of the spatial coverage of 1965 Juniper forests. Quarries and urban existed inside juniper forests but in very limited areas. Juniper forests delineation did not completely match neither between the available maps, nor to the ground. Some juniper forests were not spatially represented on all maps or existing maps represented only portion of juniper forests. Juniper forest mapping requires more consideration and field investigation. High spatial resolution satellite images 展开更多
In this paper, one of the most classical statistical methods, Canonical Correlation Analysis (CCA) is applied to identify quantitatively the driving forces of landuse structure in Yulin Prefecture. The main analysis i...In this paper, one of the most classical statistical methods, Canonical Correlation Analysis (CCA) is applied to identify quantitatively the driving forces of landuse structure in Yulin Prefecture. The main analysis is carried out through the software SPSS with the data on the level of towns and townships in 1992. The results indicate that landuse structure is determined by comprehensive action of different factors. Landuse structure with rural characteristics is mainly determined by geographical factors such as the elevation, temperature and precipitation, while the landuse structure with urban characteristics is mainly determined by demographic and socioeconomic conditions. At the same time, tests were carried out through the canonical correlation coefficient and redundancy analysis.展开更多
Using the 1°×1° NOAA AVHRR NDVI data set in China, an index on the spatial different gradient of landcover is created. Then based on the index and supported by the geographical information system, it is...Using the 1°×1° NOAA AVHRR NDVI data set in China, an index on the spatial different gradient of landcover is created. Then based on the index and supported by the geographical information system, it is revealed through principal component and factor analyses methods that there exist four types of seasonal patterns of spatial differentiation of landcover change in China, i.e. November to next March type, June to September type, May or October type and April type.展开更多
Using the three-layer variable infiltration capacity （VIC-3L） hydrological model and the successive interpolation approach （SIA） of climate factors, the authors studied the effect of different land cover types on ...Using the three-layer variable infiltration capacity （VIC-3L） hydrological model and the successive interpolation approach （SIA） of climate factors, the authors studied the effect of different land cover types on the surface hydrological cycle. Daily climate data from 1992 to 2001 and remotely-sensed leaf area index （LAI） are used in the model. The model is applied to the Baohe River basin, a subbasin of the Yangtze River basin, China, with an area of 2500 km^2. The vegetation cover types in the Baohe River basin consist mostly of the mixed forest type （-85%）. Comparison of the modeled results with the observed discharge data suggests that： （1） Daily discharges over the period of 1992-2001 simulated with inputs of remotely-sensed land cover data and LAI data can generally produce observed discharge variations, and the modeled annual total discharge agrees with observations with a mean difference of 1.4%. The use of remote sensing images also makes the modeled spatial distributions of evapotranspiration physically meaningful. （2） The relative computing error （RCE） of the annual average discharge is -24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed. The error is 21.8% when a homogeneous cropland cover is assumed and -14.32% when an REDC （Resource and Environment Database of China） land cover map is used. The error is reduced to 1.4% when a remotely-sensed land cover at 1000-m resolution is used.展开更多
Using the multi-temporal Landsat data and survey data of national resources, the authors studied the dynamics of cultivated land and landcover changes of typical ecological regions in China. The results of investigati...Using the multi-temporal Landsat data and survey data of national resources, the authors studied the dynamics of cultivated land and landcover changes of typical ecological regions in China. The results of investigation showed that the whole distribution of the cultivated land shifted to Northeast and Northwest China, and as a result, the ecological quality of cultivated land dropped down. The seacoast and cultivated land in the area of Yellow River Mouth expanded by an increasing rate of 0.73 kma-1, with a depositing rate of 2.1 kma-1. The desertification area of the dynamic of Horqin Sandy Land increased from 60.02% of the total land area in1970s to 64.82% in1980s but decreased to 54.90% in early 1990s. As to the change of North Tibet lakes, the water area of the Namu Lake decreased by 38.58 km2 from year 1970 to 1988, with a decreasing rate of 2.14 km2a-1.展开更多
Landuse/Landcover(LULC)changes are recognised as some of the major causes of environmental problems like land degradation and climate change.To achieve sustainability,we need to properly understand such changes in ord...Landuse/Landcover(LULC)changes are recognised as some of the major causes of environmental problems like land degradation and climate change.To achieve sustainability,we need to properly understand such changes in order to have adequate information that will enable us to design and implementing measures to mitigate their negative impacts.Doing this particularly requires a proper understanding of how stakeholders perceive the changes in general and their drivers in particular.Unfortunately,not much is known for many areas about the perspective of landuse stakeholders on drivers of LULC changes.This paper reports the results of a study conducted to examine the perceptions of different landuse stakeholders on drivers of LULC changes in Abuja Federal Capital Territory,Nigeria.Questionnaire survey was utilised,involving 514 households across four settlements,2 rural(Karshi and Orozo)and 2 urban(Nyanya and Karu)towns in the territory,which were complimented with Focus Group Discussions were conducted.The results obtained showed that urban dwellers are largely aware of drivers of changes in socio-economic drivers(physical development on lands,more commercial complex development and more institutional development).Rural dwellers are largely aware of environmental drivers of LULC changes(bush burning,livestock overgrazing,collections of wood and medicinal plants,and agricultural expansion).It was concluded that there is the need to bring about a harmonisation of the perceptions of LULC change drivers by the rural and urban dwellers so as to bring about a common front understanding and responding to LULC changes in the study area.展开更多
In order to assess the information content and accuracy ofLandsat ETM+ digital images in land cover change detection,change-detection techniques of image differencing,normalized difference vegetation index,principal c...In order to assess the information content and accuracy ofLandsat ETM+ digital images in land cover change detection,change-detection techniques of image differencing,normalized difference vegetation index,principal components analysis and tasseled-cap transformation were applied to yield 13 images. These images were thresholded into change and no change areas. The thresholded images were then checked in terms of various accuracies. The experiment results show that kappa coefficients of the 13 images range from 48.05 ～78.09. Different images do detect different types of changes. Images associated with changes in the near-infrared-reflectance or greenness detects crop-type changes and changes between vegetative and non-vegetative features. A unique means of using only Landsat imagery without reference data for the assessment of change in arid land are presented. Images of 12th June, 2000 and 2nd June, 2002 are used to validate the means. Analyses of standard accuracy and spatial agreement are performed to compare the new images (hereafter called "change images" ) representing the change between the two dates. Spatial agreement evaluates the conformity in the classified "change pixels" and "no-change pixels" at the same location on different change images and comprehensively examines the different techniques. This method would enable authorities to monitor land degradation efficiently and accurately.展开更多
文摘Forest fires in mountainous areas can cause severe defores-tation which can potentially trigger secondary natural hazards like debris falls and avalanches. We documented an extreme case study for the range of possible post-fire land cover （LC） dynamics. We investigated a 15-ha, steep （10°-65°） burnt slope in Styria （Austria） at elevation of 760-1130 m, which burned in 1946 and has not fully recovered to date. Seven 8-class legend LC maps were produced （1954, 1966, 1973, 1982, 1998, 2004, 2009） and integrated in a vector-based GIS, mainly by on-screen interpretation of aerial photos. Our aim was to clarify how post-wildfire LC dynamics take place on a severely damaged, steep slope and to give a basic projection of the future vegetation recovery process. The pre-fire Pinus sylvestrisstands have been mainly replaced by Picea abies and Larix decidua. Regeneration proceeded mainly from the base of the slope upwards. All tree species together still cover no more than 40% of the slope after more than 60 years of recovery, while grassland communities and rock/debris areas have expanded. Multitemporal analysis showed a slow but steady increase in woodland cover. Degraded rock/debris areas, however, expanded as well because soil erosion and related debris flows remained active. Slope angle （with a threshold value of approx. 35-40°） seemed to control whether erosion or regeneration prevailed. According to a simple extrapolation, the slope will not reach its former condition before 2070. This extreme disturbance window of more than 120 years is owed to the steepness of the slope and to the shallow soils on dolomitic bedrock that were severely damaged by the fire. The neglect of any game fencing is a further factor slowing regeneration.
基金part the research project"Importancia de las variables locales y de paisaje sobre las comunidades de peces y macroinvertebrados bentónicos de sistemas lóticos andinos"(SGI 2955)financed by the Ministry of Science,Technology and Innovation of Colombia(MINCIENCIAS)with resources from the Fondo Nacional de Patrimonio Autónomo para el Financiamiento de la Cienciaendorsed by the Universidad Pedagógica y Tecnológica de Colombia ethics committee(Acta No 06 del 12 de agosto de 2019)。
文摘Research on macroinvertebrate community structure in Andean rivers has been oriented towards describing patterns of alpha and gamma diversity by taking into account environmental predictors at local spatial scales(e.g.,micro-and mesohabitats).However,the patterns of beta diversity and the importance of landscape-scale variables have been evaluated to a lesser extent.The objective of this study was to describe the patterns of alpha and beta diversity of benthic macroinvertebrates in the Andean rivers of the Orinoco basin and their relationship with local and landscape environmental variation.A stratified random sampling of macroinvertebrates was carried out at 40 sites(comprising an altitudinal range of between 500 and 2900 m.a.s.l.),local and landscape variables were measured.Our results showed that the variation of alpha diversity was influenced by local and landscape variables,which are directly and indirectly related to the contribution of sediments,substrate composition and flow velocity,providing a heterogeneity of habitats.Global beta diversity was explained by the combined effect of local and landscape variables.Regarding the beta diversity phenomena,turnover was predominant while nestedness presented a minor contribution and both were explained in greater proportion by local descriptors and some landscape variables,specifically those of a geomorphological nature.Our results concur with the view of an environmental and spatial hierarchy within the river habitat and highlight the influence of multiple scales on macroinvertebrate diversity.The above suggests that both local and landscape scales must necessarily be considered for environmental management and the conservation of Andean lotic ecosystems.
文摘<div style="text-align:justify;"> With global warming and increased human activity, more and more ground surface areas have been affected, which leads to the creation of many problems. To understand the ecological environment changes in a typical alpine region, information on landcovers changes in the study area from 2000 to 2020 was obtained by combining remote sensing, geographic information system, and traditional statistical analysis for the Sanjiangyuan National Nature Reserve on the Qinghai-Tibet Plateau, China. The results show that the changes of surface cover in Sanjiangyuan National Nature Reserve are relatively concentrated, mainly distributed in the sections of south, northwest, central, and northeast, with the area of the changed regions and the unchanged regions being 31,127.45 km<sup>2</sup> and 271,941.37 km<sup>2</sup>, respectively. The transformation between the various types of ground landcover is mainly characterized by a shift from other types to grassland and from grassland to bare land. And the regions of change are mostly concentrated between 3500 - 4600 m in elevation. </div>
文摘An experiment is made to detect the land-cover change in the area located to the south of Aksu in the northern Taklimakan desert through analyses of satellite data pixel by pixel basis. The analyzed data are those observed in the late summer and early autumn of 1973, 1977, 1993 and 1995. As a parameter of land-cover, SAVI (Soil Adjusted Vegetation Index) derived from the data of Landsat MSS and JERS-1 OPS (Optical Sensor) is used. The result indicates the increase of vegetation in the oasis areas, confluent area of the Yarkant and Kashgar Rivers and around reservoirs while little change occurs in the desert area. The 1973 satellite image shows the abundant flow in the Yarkant River while the river is almost dried up in the satellite images of later years. The trend of the decrease in the Hotan River flow is recognized although not so dramatic as that of the Yarkant River.
文摘需要计算空间某一点的热辐射环境,由于其主要影响因素是地球和大气的背景以及太阳,而MODTRAN 是一个比较有效可靠的大气辐射传输计算程序,于是主要考虑采用 MODTRAN 程序来计算空中某一点的热辐射环境.然后需要确定 MODTRAN 程序的输入数据,另一方面 MODTRAN 程序只能计算100 km 以下的大气辐射情况,于是先要解决观测点的转换问题,这里建立了一个模型可以使100 km 以上的情况转换成100 km 的情况;第二个需要解决的问题是下垫面的边界条件确定,这里根据地球表面的基础数据,得到了下垫面的边界条件.依照上述思路和理论计算了空中某一点的辐射环境,获得了初步的计算结果.
基金STAP and DLC are each grateful for a Fulbright Specialist Grant(6330:20905,20822)for hospitality shown by DNB and the faculty and staff of the University of the Witwatersrand's Rural Facility.This material is based upon work supported by the National Science Foundation under Grant No.RCN 1140070.
文摘Objectives:(1)To evaluate how ecosystem services may be utilized to either reinforce or fracture the planning and development practices that emerged from segregation and eco-nomic exclusion;(2)To survey the current state of ecosystem service assessments and synthesize a growing number of recommendations from the literature for renovating ecosys-tem service analyses.Methods:Utilizing current maps of ecosystem service distribution in Bushbuckridge Local Municipality,South Africa,we considered how a democratized process of assessing ecosys-tem services will produce a more nuanced representation of diverse values in society and capture heterogeneity in ecosystem structure and function.Results:We propose interventions for assessing ecosystem services that are inclusive of a broad range of stakeholders'values and result in actual quantification of social and ecological processes.We demonstrate how to operationalize a pluralistic framework for ecosystem service assessments.Conclusion:A democratized approach to ecosystem service assessments is a reimagined path to rescuing a poorly implemented concept and designing and managing future social-ecological systems that benefit people and support ecosystem integrity.It is the responsi-bility of scientists who do ecosystem services research to embrace more complex,pluralistic frameworks so that sound and inclusive scientific information is utilized in decision-making.
文摘In 1965, the first forest map of Lebanon was produced. It is the oldest spatial distribution representation of junipers. Landcover maps of 2002 and 2010 are the most detailed spatial distribution that spatially shows forests. Juniper forests are found in Lebanon as mainly as clear to low density coverage. High-density juniper forests are rarely found and only on Mount-Lebanon. Juniper forests are also mixed with oaks on the Eastern flank of Mount-Lebanon. Mapping juniper forests have demonstrated high degree of complexity, especially because of their low density and being mixed. The spatial representation of juniper forests was compared between the 1965 forest map and the landcover maps of 2002 and 2010. GIS environment was used to extract juniper forests from all maps. The degree of matching between juniper forests was investigated regarding the total area and spatial overlapping. Juniper forests were examined to their spatial locations, comparing the three maps. Spatial changes and anthropogenic effect were obtained, using Google Earth facilities. Google earth had satellite images acquired since 2014. Landcover maps of 2002 and 2010 have spatially matched forest map of 1965 by about 90% and 50% respectively. Spatial coverage of juniper forests were about 12,000, 26,000 and 28,000 ha on the 1965 forest map, landcover maps of 2003 and 2010 respectively. Anti-Lebanon juniper forests were not well represented on both landcover maps. Anthropogenic activities were mainly agriculture that affected juniper forests. Cultivations have replaced about 2% of the spatial coverage of 1965 Juniper forests. Quarries and urban existed inside juniper forests but in very limited areas. Juniper forests delineation did not completely match neither between the available maps, nor to the ground. Some juniper forests were not spatially represented on all maps or existing maps represented only portion of juniper forests. Juniper forest mapping requires more consideration and field investigation. High spatial resolution satellite images
文摘In this paper, one of the most classical statistical methods, Canonical Correlation Analysis (CCA) is applied to identify quantitatively the driving forces of landuse structure in Yulin Prefecture. The main analysis is carried out through the software SPSS with the data on the level of towns and townships in 1992. The results indicate that landuse structure is determined by comprehensive action of different factors. Landuse structure with rural characteristics is mainly determined by geographical factors such as the elevation, temperature and precipitation, while the landuse structure with urban characteristics is mainly determined by demographic and socioeconomic conditions. At the same time, tests were carried out through the canonical correlation coefficient and redundancy analysis.
文摘Using the 1°×1° NOAA AVHRR NDVI data set in China, an index on the spatial different gradient of landcover is created. Then based on the index and supported by the geographical information system, it is revealed through principal component and factor analyses methods that there exist four types of seasonal patterns of spatial differentiation of landcover change in China, i.e. November to next March type, June to September type, May or October type and April type.
文摘Using the three-layer variable infiltration capacity （VIC-3L） hydrological model and the successive interpolation approach （SIA） of climate factors, the authors studied the effect of different land cover types on the surface hydrological cycle. Daily climate data from 1992 to 2001 and remotely-sensed leaf area index （LAI） are used in the model. The model is applied to the Baohe River basin, a subbasin of the Yangtze River basin, China, with an area of 2500 km^2. The vegetation cover types in the Baohe River basin consist mostly of the mixed forest type （-85%）. Comparison of the modeled results with the observed discharge data suggests that： （1） Daily discharges over the period of 1992-2001 simulated with inputs of remotely-sensed land cover data and LAI data can generally produce observed discharge variations, and the modeled annual total discharge agrees with observations with a mean difference of 1.4%. The use of remote sensing images also makes the modeled spatial distributions of evapotranspiration physically meaningful. （2） The relative computing error （RCE） of the annual average discharge is -24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed. The error is 21.8% when a homogeneous cropland cover is assumed and -14.32% when an REDC （Resource and Environment Database of China） land cover map is used. The error is reduced to 1.4% when a remotely-sensed land cover at 1000-m resolution is used.
基金National Natural Sci-ence Foundation of China (Grant No. 39900084) and KZCX1-10-07.
文摘Using the multi-temporal Landsat data and survey data of national resources, the authors studied the dynamics of cultivated land and landcover changes of typical ecological regions in China. The results of investigation showed that the whole distribution of the cultivated land shifted to Northeast and Northwest China, and as a result, the ecological quality of cultivated land dropped down. The seacoast and cultivated land in the area of Yellow River Mouth expanded by an increasing rate of 0.73 kma-1, with a depositing rate of 2.1 kma-1. The desertification area of the dynamic of Horqin Sandy Land increased from 60.02% of the total land area in1970s to 64.82% in1980s but decreased to 54.90% in early 1990s. As to the change of North Tibet lakes, the water area of the Namu Lake decreased by 38.58 km2 from year 1970 to 1988, with a decreasing rate of 2.14 km2a-1.
文摘Landuse/Landcover(LULC)changes are recognised as some of the major causes of environmental problems like land degradation and climate change.To achieve sustainability,we need to properly understand such changes in order to have adequate information that will enable us to design and implementing measures to mitigate their negative impacts.Doing this particularly requires a proper understanding of how stakeholders perceive the changes in general and their drivers in particular.Unfortunately,not much is known for many areas about the perspective of landuse stakeholders on drivers of LULC changes.This paper reports the results of a study conducted to examine the perceptions of different landuse stakeholders on drivers of LULC changes in Abuja Federal Capital Territory,Nigeria.Questionnaire survey was utilised,involving 514 households across four settlements,2 rural(Karshi and Orozo)and 2 urban(Nyanya and Karu)towns in the territory,which were complimented with Focus Group Discussions were conducted.The results obtained showed that urban dwellers are largely aware of drivers of changes in socio-economic drivers(physical development on lands,more commercial complex development and more institutional development).Rural dwellers are largely aware of environmental drivers of LULC changes(bush burning,livestock overgrazing,collections of wood and medicinal plants,and agricultural expansion).It was concluded that there is the need to bring about a harmonisation of the perceptions of LULC change drivers by the rural and urban dwellers so as to bring about a common front understanding and responding to LULC changes in the study area.
文摘In order to assess the information content and accuracy ofLandsat ETM+ digital images in land cover change detection,change-detection techniques of image differencing,normalized difference vegetation index,principal components analysis and tasseled-cap transformation were applied to yield 13 images. These images were thresholded into change and no change areas. The thresholded images were then checked in terms of various accuracies. The experiment results show that kappa coefficients of the 13 images range from 48.05 ～78.09. Different images do detect different types of changes. Images associated with changes in the near-infrared-reflectance or greenness detects crop-type changes and changes between vegetative and non-vegetative features. A unique means of using only Landsat imagery without reference data for the assessment of change in arid land are presented. Images of 12th June, 2000 and 2nd June, 2002 are used to validate the means. Analyses of standard accuracy and spatial agreement are performed to compare the new images (hereafter called "change images" ) representing the change between the two dates. Spatial agreement evaluates the conformity in the classified "change pixels" and "no-change pixels" at the same location on different change images and comprehensively examines the different techniques. This method would enable authorities to monitor land degradation efficiently and accurately.
