Ekena Pinagé - Academia.edu (original) (raw)

Papers by Ekena Pinagé

AGU Fall Meeting Abstracts, Dec 1, 2020

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), 2023

The Brazilian Amazon has been a focus of land development with large swaths of forests converted ... more The Brazilian Amazon has been a focus of land development with large swaths of forests converted to agriculture. Forest degradation by selective logging and fires has accompanied the advance of the frontier and has resulted in significant impacts on Amazonian ecosystems. Changes in forest structure resulting from forest disturbances have large impacts on the surface energy balance, including on land surface temperature (LST) and evapotranspiration (ET). The objective of this study is to assess the effects of forest disturbances on water fluxes and canopy structural properties in a transitional forest site located in Mato Grosso State, Southern Amazon. We used ET and LST products from MODIS and Landsat 8 as well as GEDI-derived forest structure data to address our research questions. We found that disturbances induced seasonal water stress, more pronounced and earlier in croplands and pastures than in forests, and more pronounced in second-growth and recently burned areas than in log...

Carbon Balance and Management

Background Tropical forests are critical for the global carbon budget, yet they have been threate... more Background Tropical forests are critical for the global carbon budget, yet they have been threatened by deforestation and forest degradation by fire, selective logging, and fragmentation. Existing uncertainties on land cover classification and in biomass estimates hinder accurate attribution of carbon emissions to specific forest classes. In this study, we used textural metrics derived from PlanetScope images to implement a probabilistic classification framework to identify intact, logged and burned forests in three Amazonian sites. We also estimated biomass for these forest classes using airborne lidar and compared biomass uncertainties using the lidar-derived estimates only to biomass uncertainties considering the forest degradation classification as well. Results Our classification approach reached overall accuracy of 0.86, with accuracy at individual sites varying from 0.69 to 0.93. Logged forests showed variable biomass changes, while burned forests showed an average carbon los...

This paper presents the detection of deforestation area with Linear Spectral Unmixing (LSU) and O... more This paper presents the detection of deforestation area with Linear Spectral Unmixing (LSU) and Object-Based Image Analysis (OBIA) applied in ALOS /AVNIR-2 multispectral image acquired at the Saracá-Taquera National Forest, Pará State, Brazil. The LSU method was utilized for endmember fraction estimation (soil, vegetation and shade). The OBIA method was used to segmentation and classification of the three fraction-images in two different scale parameters (10 and 50). Mean values of soil and cloud fraction images allowed discrimination of bare-soils. The results for both scale parameters are similar, with total soil area of 4.512 ha and 4.540 ha for 10 and 50, respectively. We concluded that the use of Linear Spectral Unmixing before Object Oriented Classification has favored discrimination of objects of interest in the scene. The two scale parameters applied in this analysis did not produce significantly different results, suggesting that scale and other parameters tests should be p...

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenha... more Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Florestal, 2013.Os recursos florestais da região amazônica têm sido largamente explorados de maneira predatória. Para reverter esse cenário, um novo modelo de gestão florestal está sendo implementado, com a concessão de terras públicas para a exploração florestal por empresas. Nesse modelo, o controle da atividade florestal é muito maior. Um dos aspectos do controle florestal, que se dá no nível da paisagem, é o monitoramento do corte seletivo com o uso de imagens de satélite e técnicas de geoprocessamento. Entretanto, por se tratar de um fenômeno mais complexo de detectar e classificar que o corte raso, esse monitoramento tem limitações. Este trabalho buscou avaliar os impactos da exploração florestal na primeira concessão florestal do Brasil, na Floresta Nacional do Jamari, no estado de Rondônia, com o uso de dados do inventário florestal da área, dados de campo e imagens de satéli...

Background: Tropical forests are critical for the global carbon budget, yet they have been threat... more Background: Tropical forests are critical for the global carbon budget, yet they have been threatened by deforestation and forest degradation by fire, selective logging, and fragmentation. Existing uncertainties on land cover classification and in biomass estimates hinder accurate attribution of carbon emissions to specific land covers. In this study, we used textural metrics derived from PlanetScope images to implement a probabilistic classification framework to identify intact, logged and burned forests in three Amazonian sites. We also estimated biomass for these forest classes using airborne lidar and compared biomass uncertainties using the lidar-derived estimates only to biomass uncertainties considering the land cover classification as well. Results: Our classification approach reached overall accuracy of 0.86, with accuracy at individual sites varying from 0.69 to 0.93. Logged forests showed variable biomass changes, while burned forests showed an average carbon loss of 35%....

Remote Sensing of Environment, 2022

ABSTRACTLogging lands (forest roads and log decks) are an underlying issue during selective loggi... more ABSTRACTLogging lands (forest roads and log decks) are an underlying issue during selective logging activities, but they are responsible for most impacts on the forest. This study aimed to apply and assess the performance of five geoprocessing techniques on remotely sensed data using three different spatial resolutions to detect logging lands under forest management at the Jamari National Forest, state of Rondônia, Brazil. The research results showed that Normalized Difference Vegetation Index (NDVI) and Principal Components Analysis (PCA) presented the best overall accuracy using spatial resolutions of 5 and 10 meters, and 30 meters, respectively. Generally, the overall accuracy and Kappa statistics for the selectively logged forest classifications were not good (39.2% or lower, and 0.38 or lower, respectively). The low performance of the geoprocessing techniques is related to the subtle changes on the forest canopy cover under selective logging activities.

Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and... more Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and regeneration, and is an important indicator of forest management quality. The objective of this study was to compare gap fraction estimates from undisturbed forests and different environments or strata of selectively logged areas. Moreover, gap fraction measurements were collected with two distinct instruments (optical canopy analyzer LAI-2000 and hemispherical photographs). Field data were collected from two sustainable forest management sites at Jamari National Forest, Rondônia State, Brazilian Amazon. Our results indicated significant differences between data ac-quired using these two instruments. For instance, the LAI-2000 data showed greater variation for each environment compared to hemispherical photographics data, and the data were also more sensitive to the increase in gap fraction. Small variations were found in the gap fraction means for the two study areas, and only data for...

IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium, 2020

Anthropogenic disturbances in tropical forests cause short-and long-term alterations in forest st... more Anthropogenic disturbances in tropical forests cause short-and long-term alterations in forest structure, species composition, and successional processes. However, improved understanding of the impacts of disturbance on forest functioning is needed to support forest management and conservation. In this study, we investigated the phenological responses of two sites in the Brazilian Amazon to forest degradation (selective logging and forest fires). We used MODIS-derived time-series to assess pre- and post-disturbance trajectories of two vegetation indices: Normalized Burn Ratio (NBR) and Enhanced Vegetation Index (EVI). We found that our study sites present different VI seasonality, and that selective logging did not cause phenological shifts. Fires, on the other hand, caused explicit EVI shifts in the transition from wet to dry season in the driest site and barely no shifts in the wettest site, and yearlong NBR shifts compared to intact forests at both sites. Changes in the magnitude and timing of phenological events highlight human-induced changes in tropical forests functioning. If widespread, these shifts may have large-scale implications for carbon sink stability in tropical regions.

Forest fragmentation divides forest areas into smaller discontinuous fragments, increasing the fo... more Forest fragmentation divides forest areas into smaller discontinuous fragments, increasing the forest edge area that experiences different environmental conditions from interior areas [1]. According to one study, logging and deforestation generate ~32,000 and 38,000 km of new forest edge each year in the Brazilian Amazon [2]. Nearly 20% of the world?s forests are within 100m of agriculture, urban, or other non-forest land uses [3]. Forest edges suffer changes in microclimate, with reduced moisture and increased variability of temperature compared to the forest interiors. In addition, winds cause greater structural damage near the forest ends and affect other ecological processes such as pollination, seed dispersal, nutrient cycling and carbon storage. The extent of forest edges in the Brazilian Amazon grows each year, caused by deforestation and forest degradation from human activity. However, the extent of edge forests, and the changes in carbon stock resulting from alterations in ...

&... more &am…

Methods in Ecology and Evolution, 2019

1. In forest ecosystems, many functional processes are governed by local canopy gap dynamics, cau... more 1. In forest ecosystems, many functional processes are governed by local canopy gap dynamics, caused by either natural or anthropogenic factors. Quantifying the size and spatial distribution of canopy gaps enables an improved understanding and predictive modelling of multiple environmental phenomena. For instance knowledge of canopy gap dynamics can help us elucidate time-integrated effects of tree mortality, regrowth and succession rates, carbon flux patterns, species heterogeneity and three-dimensional spacing within structurally complex forest ecosystems. 2. Airborne Laser Scanning (ALS) has emerged as a technology that is well-suited for mapping forest canopy gaps in a wide variety of forest ecosystems and across spatial scales. New technological and algorithmic advances, including ALS remotesensing, coupled with optimized frameworks for data processing and detection of forest canopy gaps, are allowing an enhanced understanding of forest structure and functional processes. 3. This paper introduces ForestGapr, a cutting-edge open source r package for forest gap analysis from canopy height models derived from ALS and other remote sensing sources. The ForestGapr package offers tools to (a) automate forest canopy gap detection, (b) compute a series of gap statistics, including gap-size frequency distributions and spatial distribution, (c) map gap dynamics (when multitemporal ALS data are available) and (d) convert forest canopy gaps detected into raster or vector layers as per user requirements.

Biogeosciences Discussions, 2019

Remote Sensing, 2019

Forest degradation is common in tropical landscapes, but estimates of the extent and duration of ... more Forest degradation is common in tropical landscapes, but estimates of the extent and duration of degradation impacts are highly uncertain. In particular, selective logging is a form of forest degradation that alters canopy structure and function, with persistent ecological impacts following forest harvest. In this study, we employed airborne laser scanning in 2012 and 2014 to estimate three-dimensional changes in the forest canopy and understory structure and aboveground biomass following reduced-impact selective logging in a site in Eastern Amazon. Also, we developed a binary classification model to distinguish intact versus logged forests. We found that canopy gap frequency was significantly higher in logged versus intact forests even after 8 years (the time span of our study). In contrast, the understory of logged areas could not be distinguished from the understory of intact forests after 6–7 years of logging activities. Measuring new gap formation between LiDAR acquisitions in ...

Global Biogeochemical Cycles, 2016

Deforestation rates have declined in the Brazilian Amazon since 2005, yet degradation from loggin... more Deforestation rates have declined in the Brazilian Amazon since 2005, yet degradation from logging, fire, and fragmentation has continued in frontier forests. In this study we quantified the aboveground carbon density (ACD) in intact and degraded forests using the largest data set of integrated forest inventory plots (n = 359) and airborne lidar data (18,000 ha) assembled to date for the Brazilian Amazon. We developed statistical models relating inventory ACD estimates to lidar metrics that explained 70% of the variance across forest types. Airborne lidar-ACD estimates for intact forests ranged between 5.0 ± 2.5 and 31.9 ± 10.8 kg C m −2. Degradation carbon losses were large and persistent. Sites that burned multiple times within a decade lost up to 15.0 ± 0.7 kg C m −2 (94%) of ACD. Forests that burned nearly 15 years ago had between 4.1 ± 0.5 and 6.8 ± 0.3 kg C m −2 (22-40%) less ACD than intact forests. Even for low-impact logging disturbances, ACD was between 0.7 ± 0.3 and 4.4 ± 0.4 kg C m −2 (4-21%) lower than unlogged forests. Comparing biomass estimates from airborne lidar to existing biomass maps, we found that regional and pantropical products consistently overestimated ACD in degraded forests, underestimated ACD in intact forests, and showed little sensitivity to fires and logging. Fine-scale heterogeneity in ACD across intact and degraded forests highlights the benefits of airborne lidar for carbon mapping. Differences between airborne lidar and regional biomass maps underscore the need to improve and update biomass estimates for dynamic land use frontiers, to better characterize deforestation and degradation carbon emissions for regional carbon budgets and Reduce Emissions from Deforestation and forest Degradation (REDD+).

AGU Fall Meeting Abstracts, Dec 1, 2020

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), 2023

The Brazilian Amazon has been a focus of land development with large swaths of forests converted ... more The Brazilian Amazon has been a focus of land development with large swaths of forests converted to agriculture. Forest degradation by selective logging and fires has accompanied the advance of the frontier and has resulted in significant impacts on Amazonian ecosystems. Changes in forest structure resulting from forest disturbances have large impacts on the surface energy balance, including on land surface temperature (LST) and evapotranspiration (ET). The objective of this study is to assess the effects of forest disturbances on water fluxes and canopy structural properties in a transitional forest site located in Mato Grosso State, Southern Amazon. We used ET and LST products from MODIS and Landsat 8 as well as GEDI-derived forest structure data to address our research questions. We found that disturbances induced seasonal water stress, more pronounced and earlier in croplands and pastures than in forests, and more pronounced in second-growth and recently burned areas than in log...

Carbon Balance and Management

Background Tropical forests are critical for the global carbon budget, yet they have been threate... more Background Tropical forests are critical for the global carbon budget, yet they have been threatened by deforestation and forest degradation by fire, selective logging, and fragmentation. Existing uncertainties on land cover classification and in biomass estimates hinder accurate attribution of carbon emissions to specific forest classes. In this study, we used textural metrics derived from PlanetScope images to implement a probabilistic classification framework to identify intact, logged and burned forests in three Amazonian sites. We also estimated biomass for these forest classes using airborne lidar and compared biomass uncertainties using the lidar-derived estimates only to biomass uncertainties considering the forest degradation classification as well. Results Our classification approach reached overall accuracy of 0.86, with accuracy at individual sites varying from 0.69 to 0.93. Logged forests showed variable biomass changes, while burned forests showed an average carbon los...

This paper presents the detection of deforestation area with Linear Spectral Unmixing (LSU) and O... more This paper presents the detection of deforestation area with Linear Spectral Unmixing (LSU) and Object-Based Image Analysis (OBIA) applied in ALOS /AVNIR-2 multispectral image acquired at the Saracá-Taquera National Forest, Pará State, Brazil. The LSU method was utilized for endmember fraction estimation (soil, vegetation and shade). The OBIA method was used to segmentation and classification of the three fraction-images in two different scale parameters (10 and 50). Mean values of soil and cloud fraction images allowed discrimination of bare-soils. The results for both scale parameters are similar, with total soil area of 4.512 ha and 4.540 ha for 10 and 50, respectively. We concluded that the use of Linear Spectral Unmixing before Object Oriented Classification has favored discrimination of objects of interest in the scene. The two scale parameters applied in this analysis did not produce significantly different results, suggesting that scale and other parameters tests should be p...

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenha... more Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Florestal, 2013.Os recursos florestais da região amazônica têm sido largamente explorados de maneira predatória. Para reverter esse cenário, um novo modelo de gestão florestal está sendo implementado, com a concessão de terras públicas para a exploração florestal por empresas. Nesse modelo, o controle da atividade florestal é muito maior. Um dos aspectos do controle florestal, que se dá no nível da paisagem, é o monitoramento do corte seletivo com o uso de imagens de satélite e técnicas de geoprocessamento. Entretanto, por se tratar de um fenômeno mais complexo de detectar e classificar que o corte raso, esse monitoramento tem limitações. Este trabalho buscou avaliar os impactos da exploração florestal na primeira concessão florestal do Brasil, na Floresta Nacional do Jamari, no estado de Rondônia, com o uso de dados do inventário florestal da área, dados de campo e imagens de satéli...

Background: Tropical forests are critical for the global carbon budget, yet they have been threat... more Background: Tropical forests are critical for the global carbon budget, yet they have been threatened by deforestation and forest degradation by fire, selective logging, and fragmentation. Existing uncertainties on land cover classification and in biomass estimates hinder accurate attribution of carbon emissions to specific land covers. In this study, we used textural metrics derived from PlanetScope images to implement a probabilistic classification framework to identify intact, logged and burned forests in three Amazonian sites. We also estimated biomass for these forest classes using airborne lidar and compared biomass uncertainties using the lidar-derived estimates only to biomass uncertainties considering the land cover classification as well. Results: Our classification approach reached overall accuracy of 0.86, with accuracy at individual sites varying from 0.69 to 0.93. Logged forests showed variable biomass changes, while burned forests showed an average carbon loss of 35%....

Remote Sensing of Environment, 2022

ABSTRACTLogging lands (forest roads and log decks) are an underlying issue during selective loggi... more ABSTRACTLogging lands (forest roads and log decks) are an underlying issue during selective logging activities, but they are responsible for most impacts on the forest. This study aimed to apply and assess the performance of five geoprocessing techniques on remotely sensed data using three different spatial resolutions to detect logging lands under forest management at the Jamari National Forest, state of Rondônia, Brazil. The research results showed that Normalized Difference Vegetation Index (NDVI) and Principal Components Analysis (PCA) presented the best overall accuracy using spatial resolutions of 5 and 10 meters, and 30 meters, respectively. Generally, the overall accuracy and Kappa statistics for the selectively logged forest classifications were not good (39.2% or lower, and 0.38 or lower, respectively). The low performance of the geoprocessing techniques is related to the subtle changes on the forest canopy cover under selective logging activities.

Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and... more Gap fraction is a biophysical variable related to energy balance, forest fauna, micro-climate and regeneration, and is an important indicator of forest management quality. The objective of this study was to compare gap fraction estimates from undisturbed forests and different environments or strata of selectively logged areas. Moreover, gap fraction measurements were collected with two distinct instruments (optical canopy analyzer LAI-2000 and hemispherical photographs). Field data were collected from two sustainable forest management sites at Jamari National Forest, Rondônia State, Brazilian Amazon. Our results indicated significant differences between data ac-quired using these two instruments. For instance, the LAI-2000 data showed greater variation for each environment compared to hemispherical photographics data, and the data were also more sensitive to the increase in gap fraction. Small variations were found in the gap fraction means for the two study areas, and only data for...

IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium, 2020

Anthropogenic disturbances in tropical forests cause short-and long-term alterations in forest st... more Anthropogenic disturbances in tropical forests cause short-and long-term alterations in forest structure, species composition, and successional processes. However, improved understanding of the impacts of disturbance on forest functioning is needed to support forest management and conservation. In this study, we investigated the phenological responses of two sites in the Brazilian Amazon to forest degradation (selective logging and forest fires). We used MODIS-derived time-series to assess pre- and post-disturbance trajectories of two vegetation indices: Normalized Burn Ratio (NBR) and Enhanced Vegetation Index (EVI). We found that our study sites present different VI seasonality, and that selective logging did not cause phenological shifts. Fires, on the other hand, caused explicit EVI shifts in the transition from wet to dry season in the driest site and barely no shifts in the wettest site, and yearlong NBR shifts compared to intact forests at both sites. Changes in the magnitude and timing of phenological events highlight human-induced changes in tropical forests functioning. If widespread, these shifts may have large-scale implications for carbon sink stability in tropical regions.

Forest fragmentation divides forest areas into smaller discontinuous fragments, increasing the fo... more Forest fragmentation divides forest areas into smaller discontinuous fragments, increasing the forest edge area that experiences different environmental conditions from interior areas [1]. According to one study, logging and deforestation generate ~32,000 and 38,000 km of new forest edge each year in the Brazilian Amazon [2]. Nearly 20% of the world?s forests are within 100m of agriculture, urban, or other non-forest land uses [3]. Forest edges suffer changes in microclimate, with reduced moisture and increased variability of temperature compared to the forest interiors. In addition, winds cause greater structural damage near the forest ends and affect other ecological processes such as pollination, seed dispersal, nutrient cycling and carbon storage. The extent of forest edges in the Brazilian Amazon grows each year, caused by deforestation and forest degradation from human activity. However, the extent of edge forests, and the changes in carbon stock resulting from alterations in ...

&... more &am…

Methods in Ecology and Evolution, 2019

1. In forest ecosystems, many functional processes are governed by local canopy gap dynamics, cau... more 1. In forest ecosystems, many functional processes are governed by local canopy gap dynamics, caused by either natural or anthropogenic factors. Quantifying the size and spatial distribution of canopy gaps enables an improved understanding and predictive modelling of multiple environmental phenomena. For instance knowledge of canopy gap dynamics can help us elucidate time-integrated effects of tree mortality, regrowth and succession rates, carbon flux patterns, species heterogeneity and three-dimensional spacing within structurally complex forest ecosystems. 2. Airborne Laser Scanning (ALS) has emerged as a technology that is well-suited for mapping forest canopy gaps in a wide variety of forest ecosystems and across spatial scales. New technological and algorithmic advances, including ALS remotesensing, coupled with optimized frameworks for data processing and detection of forest canopy gaps, are allowing an enhanced understanding of forest structure and functional processes. 3. This paper introduces ForestGapr, a cutting-edge open source r package for forest gap analysis from canopy height models derived from ALS and other remote sensing sources. The ForestGapr package offers tools to (a) automate forest canopy gap detection, (b) compute a series of gap statistics, including gap-size frequency distributions and spatial distribution, (c) map gap dynamics (when multitemporal ALS data are available) and (d) convert forest canopy gaps detected into raster or vector layers as per user requirements.

Biogeosciences Discussions, 2019

Remote Sensing, 2019

Forest degradation is common in tropical landscapes, but estimates of the extent and duration of ... more Forest degradation is common in tropical landscapes, but estimates of the extent and duration of degradation impacts are highly uncertain. In particular, selective logging is a form of forest degradation that alters canopy structure and function, with persistent ecological impacts following forest harvest. In this study, we employed airborne laser scanning in 2012 and 2014 to estimate three-dimensional changes in the forest canopy and understory structure and aboveground biomass following reduced-impact selective logging in a site in Eastern Amazon. Also, we developed a binary classification model to distinguish intact versus logged forests. We found that canopy gap frequency was significantly higher in logged versus intact forests even after 8 years (the time span of our study). In contrast, the understory of logged areas could not be distinguished from the understory of intact forests after 6–7 years of logging activities. Measuring new gap formation between LiDAR acquisitions in ...

Global Biogeochemical Cycles, 2016

Deforestation rates have declined in the Brazilian Amazon since 2005, yet degradation from loggin... more Deforestation rates have declined in the Brazilian Amazon since 2005, yet degradation from logging, fire, and fragmentation has continued in frontier forests. In this study we quantified the aboveground carbon density (ACD) in intact and degraded forests using the largest data set of integrated forest inventory plots (n = 359) and airborne lidar data (18,000 ha) assembled to date for the Brazilian Amazon. We developed statistical models relating inventory ACD estimates to lidar metrics that explained 70% of the variance across forest types. Airborne lidar-ACD estimates for intact forests ranged between 5.0 ± 2.5 and 31.9 ± 10.8 kg C m −2. Degradation carbon losses were large and persistent. Sites that burned multiple times within a decade lost up to 15.0 ± 0.7 kg C m −2 (94%) of ACD. Forests that burned nearly 15 years ago had between 4.1 ± 0.5 and 6.8 ± 0.3 kg C m −2 (22-40%) less ACD than intact forests. Even for low-impact logging disturbances, ACD was between 0.7 ± 0.3 and 4.4 ± 0.4 kg C m −2 (4-21%) lower than unlogged forests. Comparing biomass estimates from airborne lidar to existing biomass maps, we found that regional and pantropical products consistently overestimated ACD in degraded forests, underestimated ACD in intact forests, and showed little sensitivity to fires and logging. Fine-scale heterogeneity in ACD across intact and degraded forests highlights the benefits of airborne lidar for carbon mapping. Differences between airborne lidar and regional biomass maps underscore the need to improve and update biomass estimates for dynamic land use frontiers, to better characterize deforestation and degradation carbon emissions for regional carbon budgets and Reduce Emissions from Deforestation and forest Degradation (REDD+).