Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,m...Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,mountain and urban materials.The shadow correction process consists of two steps:detection and de-shadowing.This paper reviews a range of techniques for both steps,focusing on urban regions(urban shadows),mountainous areas(topographic shadow),cloud shadows and composite shadows.Several issues including the problems and the advantages of those algorithms are discussed.In recent years,thresholding and recovery techniques have become important for shadow detection and de-shadowing,respectively.Research on shadow correction is still an important topic,particularly for urban regions(in high spatial resolution data) and mountainous forest(in high and medium spatial resolution data).Moreover,new algorithms are needed for shadow correction,especially given the advent of new satellite images.展开更多
Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carb...Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carbon estimates are scarce globally, particularly in Mexico. The objective of this study was to simulate future land-cover scenarios for the Sierra Madre Oriental in Mexico, by analyzing past forest cover changes. Another objective was to estimate stored carbon in the two study areas. These objectives involve the generation of information that could be useful inputs to anti-deforestation public policy such as the REDD+ strategy. Remote sensing was used to measure land cover change and estimate carbon stocks. Satellite images from 2015, 2000 and 1986 were used, and Dinamica EGO freeware generatedmodels of future projections. Between 1986 and 2015, 5171 ha of forest were converted to pasture. The annual deforestation rates were –1.5% for Tlanchinol and –1.3% for the San Bartolo Tutotepec sites. Distance to roads and marginalization were highly correlated with deforestation. By 2030, an estimated 3608 ha of forest in these sites will have been converted to pasture. Stored carbon was estimated at 16.35 Mg C ha-1 for the Tlanchinol site and 12.7 Mg C ha-1 for the San Bartolo site. In the Sierra Madre Oriental deforestation due to land cover change(–1.4%) is higher than levels reported worldwide. Besides having high values of stored carbon(14.5 Mg C ha-1), these forests have high biodiversity. The models' outputs show that the deforestation process will continue if action is not taken to avoid the expansion of livestock pasturing. This can be done by paying incentives for forest conservation to the owners of the land. The results suggest that REDD+ is currently the most viable strategy for reducing deforestation rates in tropical montane cloud forests in Sierra Madre Oriental.展开更多
In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous enviro...In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH （diameter at breast height） larger than 50 cm （LLT, large living trees） were measured （DBH and height） and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 12o to ~5o years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of largeliving trees （age 〉 120 years）. The size-class distribution of stems had a reverse-J shape, and basal area was 52 m2 ha-1. Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m3 ha-1. Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.展开更多
Hilly or mountainous terrain occupies around 12% of the area of Bangladesh.Natural resources associated with Bangladesh's hill are forest resources,biodiversity,minerals,and agricultural crops.Natural resources ha...Hilly or mountainous terrain occupies around 12% of the area of Bangladesh.Natural resources associated with Bangladesh's hill are forest resources,biodiversity,minerals,and agricultural crops.Natural resources have been exploited in the recent four decades due to excessive clearing of hill forest cover,resulting in loss of species richness, impacts related to increased water flow variability, increased hill slope erosion and flooding intensity, and a gradual decrease in the extent of hill area in Bangladesh.This review explores the major causes and effects of depletion of natural resources by linking drivers,pressures and the related impacts.A review has been conducted to structure the effects on the hilly areas and describe the responses to minimize them in the associated DPSIR framework.Population growth has been identified as a major driver contributing to high deforestation rates.This may negatively effect agricultural productivity and increase the frequency of serious flooding.Slash and burn cultivation also impacts the regeneration of evergreen forests,which may accelerate soil erosion. Due to this and other factors,local people are facing a deficits of natural resources(food,fodder,fuel wood and water),which exacerbates the effects of poverty. Future research should try to facilitate decision making for sustainable utilization of natural resources management in the hilly areas of Bangladesh. Additional conservation measures should be developed to increase the resilience of ecosystems at national and regional levels.展开更多
In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roif...In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roifill and imfill,in order to improve the accuracy of forest mapping over mountainous regions.These two methods were applied to Landsat Enhanced Thematic Mapper (ETM +) multispectral image from Dong Yang County,Zhejiang Province,China.The performance of these methods was compared with two conventional techniques,including cosine correction and multisource classification.The results showed that by applying filling approaches,average overall accuracy of classification was improved by 14 percent.However,through conventional methods this value increased only by 9 percent.The results also revealed that estimated forest area on the basis of shadow-corrected images by 'roifill' technique was much closer to the survey data compared to traditional algorithms.Apart from this finding,our finding indicated that topographic shadow was an accentuated problem in medium resolution images such as Landsat ETM+ over mountainous regions.展开更多
Alborz Mountains host Caspian Hyrcanian forest ecoregion along the northern slopes and forest steppe ecoregion in highlands. Hyrcanian forest covers the southeastern part of Caucasus biodiversity hotspot and is of gre...Alborz Mountains host Caspian Hyrcanian forest ecoregion along the northern slopes and forest steppe ecoregion in highlands. Hyrcanian forest covers the southeastern part of Caucasus biodiversity hotspot and is of great biogeographic importance. Altitudinal pattern and correlation between woody species biodiversity （DIV）, forest structure （（stem density （DEN）, mean basal area （MBA） and mean height class （MHC）） and disturbance （DIS） were explored along 2,4oo m altitudinal gradient in Hyrcanian relict forest, Central Alborz Mountains. Vegetation changes from lowland forest （LoF） to mid- altitude forest （MiF） and montane forest （MoF） in this area. The altitudinal gradient was divided into twelve 200 m elevational belts. Point centered quarter method （PCQM） with 96 sampling points and 83 vegetation samples by plot method （PM） were used to record field data. Shannon-Wiener index and Pearson coefficient were used for diversity and correlation analysis. The results showed that DEN decreased linearly, MBA and MHC showed relatively hump shaped and DIS showed a reverse hump shaped pattern of change along altitudinal gradient. Woody species diversity decreased non-steadily from LoF to MoF. Transitional vegetations of Carpinus-Fagus and Fagus-Quercus represented higher diversity of woody taxa compared to adjacent homogenous communities. Significant correlation was observed between altitude and all parameters： DEN with MBA, DIS and DIV; MBA with DIS; MHC with DIS along with DIV; and DIS with DIV at the study area scale. Surprisingly,correlation between studied parameters differed within each vegetation type. Altitude probably acts as a proxy for human and environmental driving forces in this area. Stability of warm and wet condition, season length, soil depth along with forest accessibility probably influences the altitudinal pattern of the studied parameters. Disturbance affects forest structure and consequently diversity; especially in lowlands. The obtained results recommend using both forest biodiversity and mensuration data in management process of forest ecosystems.展开更多
基金Under the auspices of National Technology Research and Development Program of China(No.2006BAJ05A02)National Natural Science Foundation of China(No.31172023)
文摘Shadow is one of the major problems in remotely sensed imagery which hampers the accuracy of information extraction and change detection.In these images,shadow is generally produced by different objects,namely,cloud,mountain and urban materials.The shadow correction process consists of two steps:detection and de-shadowing.This paper reviews a range of techniques for both steps,focusing on urban regions(urban shadows),mountainous areas(topographic shadow),cloud shadows and composite shadows.Several issues including the problems and the advantages of those algorithms are discussed.In recent years,thresholding and recovery techniques have become important for shadow detection and de-shadowing,respectively.Research on shadow correction is still an important topic,particularly for urban regions(in high spatial resolution data) and mountainous forest(in high and medium spatial resolution data).Moreover,new algorithms are needed for shadow correction,especially given the advent of new satellite images.
基金support with doctorate fellowship CONACy T(No.266708)Postgraduate Sciences in Biodiversity and Conservation of the Center for Biological Research,UAEH
文摘Tropical montane cloud forest is one of the ecosystems with the highest biomass worldwide, representing an important carbon store. Globally its deforestation index is –1.1%, but in Mexico it is higher than –3%. Carbon estimates are scarce globally, particularly in Mexico. The objective of this study was to simulate future land-cover scenarios for the Sierra Madre Oriental in Mexico, by analyzing past forest cover changes. Another objective was to estimate stored carbon in the two study areas. These objectives involve the generation of information that could be useful inputs to anti-deforestation public policy such as the REDD+ strategy. Remote sensing was used to measure land cover change and estimate carbon stocks. Satellite images from 2015, 2000 and 1986 were used, and Dinamica EGO freeware generatedmodels of future projections. Between 1986 and 2015, 5171 ha of forest were converted to pasture. The annual deforestation rates were –1.5% for Tlanchinol and –1.3% for the San Bartolo Tutotepec sites. Distance to roads and marginalization were highly correlated with deforestation. By 2030, an estimated 3608 ha of forest in these sites will have been converted to pasture. Stored carbon was estimated at 16.35 Mg C ha-1 for the Tlanchinol site and 12.7 Mg C ha-1 for the San Bartolo site. In the Sierra Madre Oriental deforestation due to land cover change(–1.4%) is higher than levels reported worldwide. Besides having high values of stored carbon(14.5 Mg C ha-1), these forests have high biodiversity. The models' outputs show that the deforestation process will continue if action is not taken to avoid the expansion of livestock pasturing. This can be done by paying incentives for forest conservation to the owners of the land. The results suggest that REDD+ is currently the most viable strategy for reducing deforestation rates in tropical montane cloud forests in Sierra Madre Oriental.
基金partially developed within the scope of research project LIFE+2013 "PAN LIFE Project-Natura 2000 Action Programme.Life+Nature-2013-LIFE13 NAT/IT/001075
文摘In Europe, very small forest areas can be considered to be old-growth, and they are mainly located in Eastern Europe. The typical structures of old growth forests infrequently occur in Mediterranean mountainous environments, since they have been affected by human activities for centuries. This study focused on a remote and almost pure Italian maple stand located in southern Italy, which has not been managed for long time due to its inaccessibility. The effects of natural evolution on the forest stand were evaluated through the analysis of the spatial and chronological structure and the regeneration patterns, then estimating the amounts and quality of deadwood occurrence. Across the whole stand, all the trees with DBH （diameter at breast height） larger than 50 cm （LLT, large living trees） were measured （DBH and height） and age was also determined through a dendrochronological approach. The diameters observed ranged between 50 and 145 cm with ages of 12o to ~5o years. The Latham index calculated for trees within the sample plot highlighted a multilayered canopy with a dominant layer of largeliving trees （age 〉 120 years）. The size-class distribution of stems had a reverse-J shape, and basal area was 52 m2 ha-1. Deadwood was exclusively constituted by standing dead trees and CWD and its volume was on average 31 m3 ha-1. Pure Italian maple forests are generally rare in Europe, and it was unexpected to find a forest stand characterized by a so complex structure with old growth attributes. The study of complex forest stand, even if small, could give precious information on the forest evolution, clarifying also diverse auto-ecological traits of tree species that usually are not common in our forests.
文摘Hilly or mountainous terrain occupies around 12% of the area of Bangladesh.Natural resources associated with Bangladesh's hill are forest resources,biodiversity,minerals,and agricultural crops.Natural resources have been exploited in the recent four decades due to excessive clearing of hill forest cover,resulting in loss of species richness, impacts related to increased water flow variability, increased hill slope erosion and flooding intensity, and a gradual decrease in the extent of hill area in Bangladesh.This review explores the major causes and effects of depletion of natural resources by linking drivers,pressures and the related impacts.A review has been conducted to structure the effects on the hilly areas and describe the responses to minimize them in the associated DPSIR framework.Population growth has been identified as a major driver contributing to high deforestation rates.This may negatively effect agricultural productivity and increase the frequency of serious flooding.Slash and burn cultivation also impacts the regeneration of evergreen forests,which may accelerate soil erosion. Due to this and other factors,local people are facing a deficits of natural resources(food,fodder,fuel wood and water),which exacerbates the effects of poverty. Future research should try to facilitate decision making for sustainable utilization of natural resources management in the hilly areas of Bangladesh. Additional conservation measures should be developed to increase the resilience of ecosystems at national and regional levels.
基金supported by the funding from National Natural Science Foundation of China(Grant No 30671212)partially by NASA projects NNX08AH50G and G05GD49G at Michigan State University
文摘In general,topographic shadow may reduce performance of forest mapping over mountainous regions in remotely sensed images.In this paper,information in shadow was synthesized by using two filling techniques,namely,roifill and imfill,in order to improve the accuracy of forest mapping over mountainous regions.These two methods were applied to Landsat Enhanced Thematic Mapper (ETM +) multispectral image from Dong Yang County,Zhejiang Province,China.The performance of these methods was compared with two conventional techniques,including cosine correction and multisource classification.The results showed that by applying filling approaches,average overall accuracy of classification was improved by 14 percent.However,through conventional methods this value increased only by 9 percent.The results also revealed that estimated forest area on the basis of shadow-corrected images by 'roifill' technique was much closer to the survey data compared to traditional algorithms.Apart from this finding,our finding indicated that topographic shadow was an accentuated problem in medium resolution images such as Landsat ETM+ over mountainous regions.
文摘Alborz Mountains host Caspian Hyrcanian forest ecoregion along the northern slopes and forest steppe ecoregion in highlands. Hyrcanian forest covers the southeastern part of Caucasus biodiversity hotspot and is of great biogeographic importance. Altitudinal pattern and correlation between woody species biodiversity （DIV）, forest structure （（stem density （DEN）, mean basal area （MBA） and mean height class （MHC）） and disturbance （DIS） were explored along 2,4oo m altitudinal gradient in Hyrcanian relict forest, Central Alborz Mountains. Vegetation changes from lowland forest （LoF） to mid- altitude forest （MiF） and montane forest （MoF） in this area. The altitudinal gradient was divided into twelve 200 m elevational belts. Point centered quarter method （PCQM） with 96 sampling points and 83 vegetation samples by plot method （PM） were used to record field data. Shannon-Wiener index and Pearson coefficient were used for diversity and correlation analysis. The results showed that DEN decreased linearly, MBA and MHC showed relatively hump shaped and DIS showed a reverse hump shaped pattern of change along altitudinal gradient. Woody species diversity decreased non-steadily from LoF to MoF. Transitional vegetations of Carpinus-Fagus and Fagus-Quercus represented higher diversity of woody taxa compared to adjacent homogenous communities. Significant correlation was observed between altitude and all parameters： DEN with MBA, DIS and DIV; MBA with DIS; MHC with DIS along with DIV; and DIS with DIV at the study area scale. Surprisingly,correlation between studied parameters differed within each vegetation type. Altitude probably acts as a proxy for human and environmental driving forces in this area. Stability of warm and wet condition, season length, soil depth along with forest accessibility probably influences the altitudinal pattern of the studied parameters. Disturbance affects forest structure and consequently diversity; especially in lowlands. The obtained results recommend using both forest biodiversity and mensuration data in management process of forest ecosystems.
