Assessing intraspecific wood density variations of Syzgium sp. in tropical forest of Southwest Sabah
IOP Conference Series: Earth and Environmental Science
Wood density (WD) is a critical determinant of estimating forest above-ground biomass (AGB) and c... more Wood density (WD) is a critical determinant of estimating forest above-ground biomass (AGB) and carbon stock. Thus, heterogeneity in WD on individuals within species trees needs to be scrutinized, and acquisition of fixed WD value is essential to estimate carbon stock with confidence. This study investigated intraspecific variation in WD of Syzgium sp., also known as “Jambu” or “Kelat”. It is the most occurring species in study areas, and is regarded as an economically important species. Firstly, one half-diameter drilling from bark-to-pith measurement was taken per tree using Rinntech Resistograph R650-ED at breast height. Meanwhile, 5.15 mm-diameter core was sampled at 1.30 m above-ground, with DeWalt DCF899HP2 20V impact wrench 950 Nm and Haglöf increment borer. WD was estimated for each core sample using a dimensional method. Drilling resistance (DR) profiles were processed using DECOM 2.38m1 Scientific (c), and several independent variables were extracted from the resistogram. ...
Pembangunan sukan di Sabah : penyelidikan padang bola sepak berumput turf di sekitar zon pantai barat Sabah menggunakan GIS / Alexius Korom and Haijon Gunggut
Bola sepak adalah sejenis sukan di luar rumah (outdoor) yang dimainkan di padang bola sepak atau ... more Bola sepak adalah sejenis sukan di luar rumah (outdoor) yang dimainkan di padang bola sepak atau kawasan lapang yang berumput turf biasanya jenis 'Cowgrass'. Objektif kajian adalah memperoleh data berkenaan padang bola sepak di sekitar Bandaraya Kota Kinabalu seperti jenis rumput, saiz, pemilik/pentdbir padang, jenis aktiviti yang dijalankan, kadar sewa, kecerunan dan kualiti penjagaan padang. Ini bertujuan untuk mengujudkan databes GIS padang-padang bola sepak di sekitar kawasan Zon Pantai Barat Sabah. Kaedah yang yang digunakan ialah pemeriksaan lapangan selepas pengenalpastian padang bola sepak melalui GIS. Sebanyak 45 padang telah diperiksa pada Ogos dan September 2009. Hasil kajian menunjukkan bahawa dari segi jenis rumput, semua padang yang ditinjau adalah berumput campuran (mixed grass). Dari segi saiz pula, majoriti padang memenuhi piawai saiz padang biasa. Kebanyakan padang yang ada dimiliki Lembaga Sukan Sabah atau organisasi berkaitan pendidikan (sekolah/kolej/uni...
Aboveground biomass assessment of degraded rainforest using IKONOS-2: specific forest cluster analysis
Accurate estimation of aboveground biomass (AGB) has increasingly important especially dealing wi... more Accurate estimation of aboveground biomass (AGB) has increasingly important especially dealing with various levels of forest degradation. Exploration of forest texture and forest structure helps to define forest type which shaping a distribution of AGB. In this study, high resolution satellite imagery of IKONOS-2 was used to assess the AGB of tropical Borneo rainforest at specific degradation level. Study site consists of degraded lowland Dipterocarp forest located at Tangkulap forest reserves in Sabah. The satellite image was segmented using eCognition and classified into three specific levels of forest cluster that are early, mid and late-successional forest. Field plots were assigned to the cluster by AGB to reflect the degradation levels. Multiple stepwise regression analyses were performed between AGB and independent variables of spectral and textural properties. The resulted estimation models of AGB within each forest cluster level had R2 ranging from 0.65 to 0.70 (Pearson coe...
The information on biophysical parameters—such as height, crown area, and vegetation indices such... more The information on biophysical parameters—such as height, crown area, and vegetation indices such as the normalized difference vegetation index (NDVI) and normalized difference red edge index (NDRE)—are useful to monitor health conditions and the growth of oil palm trees in precision agriculture practices. The use of multispectral sensors mounted on unmanned aerial vehicles (UAV) provides high spatio-temporal resolution data to study plant health. However, the influence of UAV altitude when extracting biophysical parameters of oil palm from a multispectral sensor has not yet been well explored. Therefore, this study utilized the MicaSense RedEdge sensor mounted on a DJI Phantom–4 UAV platform for aerial photogrammetry. Three different close-range multispectral aerial images were acquired at a flight altitude of 20 m, 60 m, and 80 m above ground level (AGL) over the young oil palm plantation area in Malaysia. The images were processed using the structure from motion (SfM) technique i...
Oil palms (OP) in Sabah, Malaysia were studied to explore the relationship between canopy size an... more Oil palms (OP) in Sabah, Malaysia were studied to explore the relationship between canopy size and aboveground biomass (AGB). Four available allometric equations were used to calculate the dry AGB. Pearson's correlation analysis was performed between crown diameter (CD) and crown area (CA) towards the variables of AGB, height and dbh. In this analysis, the transformation to natural log of variable resulted in better coefficient compared to the original one. The mean of various variables such as height (stem, total and height difference), biomass (crown, trunk and total), dbh (inner and outer) and number of petiole leaf were calculated based on 32 independent sample plots (N = 222 palms) across various age stages from 2 to 24 years. These variables were regressed against CD and age. AGB versus CD was a nonlinear with R2 ranging from 0.950 to 0.975. Random modelling and cross validation between AGB and CD was applied at the ratio of 70:30. Upon checking, the best estimation was ac...
Estimating tree height and above ground biomass of tropical rainforest across different degradation levels in malaysian borneo using airborne lidar data
Climage Change Office, Forestry and Forest Products Research Institute, Tsukuba, Japan, e-mail: h... more Climage Change Office, Forestry and Forest Products Research Institute, Tsukuba, Japan, e-mail: hirat09@affrc.go.jp School of International Tropical Forestry, Universiti Malaysia Sabah, Kota Kinabalu, Sabah, Nalaysia, e-mail: pmh@ums.edu.my, w.wilson@ums.edu.my Kyusyu Research Center, Forestry and Forest Products Research Institute, Kumamoto, Japan, e-mail: rslsaito@ffpri.affrc.go.jp Department of Forest Management, Forestry and Forest Products Research Institute, Tsukuba, Japan, e-mail: matsuu50@affrc.go.jp Universiti Teknologi MARA Sabah Branch, Kota Kinabalu, Sabah, Malaysia Graduate School of Agriculture, University of Kyoto, Kyoto, Japan
Exploring forest degradation: Tree density and aboveground biomass
Assessing forest degradation is increasingly important to support a transparent and reliable repo... more Assessing forest degradation is increasingly important to support a transparent and reliable reporting system for Reduced Emission from Deforestation and Forest Degradation-plus (REDD+) in combating the climate change. Exploration of forest degradation is still insufficient in the tropical region. In this paper, the logged-over Tangkulap and Deramakot Forest Reserves in Sabah, Malaysia-Borneo were thoroughly studied. Using the IKONOS-2 image, forest was segmented based on multi-resolution algorithm in eCognition and classified into forest degradation types. AGB was used to guide the classification into three levels of forest degradation i.e. very-degraded (VDF), degraded (DF) and intact forests (IF). The accuracy was assessed at 0.65 of Kappa coefficient (79% of overall accuracy). Under each forest degradation class, the distribution patterns of tree densities and AGBs at the respective strata of understory, canopy and emergent were examined. Statistical mean and standard deviation were used to describe the variation patterns. Tree density of understory strata is saturating at DF and IFs. Tree density of emergent strata at IF is about twice higher than at DF. AGB at IF is 3.6 and 1.8 times higher than at VDF and DF, respectively. Standard deviation of AGB tends to increase nonlinearly from VDF to IF. This study has examined the patterns of tree density and AGB in order to understand the recovery processes of the degraded forest.
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2019
Malaysia currently is one of the biggest global producers and exporters of palm oil. The world's ... more Malaysia currently is one of the biggest global producers and exporters of palm oil. The world's expanding oil palm plantation areas contribute to climate change and in-return, climate is change also affecting the health of oil palms through a range of abiotic and biotic stresses. Current advancements in Precision Agriculture research using UAV gives an advantage to detect the health conditions of oil palm at early stages. Thus, remedial actions can be taken to prolong the life and increase oil palms productivity. This paper explores the use of UAV derived NDVI and CPA of young oil palm to detect the health conditions. NDVI of individual oil palm were extracted using ground masking layer from the dense point clouds and visual on-screen manual editing was done for removing trees other than oil palm in ENVI software. The classified individual crown NDVI were then processed to extract the mean NDVI also conversion to vector to obtain the individual crown outline. Extracted mean NDVI was classified into un-healthy and healthy trees while the CPA was classified into small, medium and big size classes. These classes of NDVI and CPA were analysed using GIS overlay method thus revealing the spatial patterns of individual oil palm trees and its health conditions. Overall, the majority of oil palm trees of the study area are healthy but average performing. However, few oil palm trees detected having health problems which has low NDVI and small CPA. This study demonstrates that biophysical parameters such as the CPA can be used to detect individual young oil palm trees health conditions and problems when combined with vegetation indices such as NDVI.
Monitoring of land use and land cover change using remote sensing is important to evaluate the im... more Monitoring of land use and land cover change using remote sensing is important to evaluate the impacts of anthropogenic activities on the environment. Digital change detection using post-classification can help to elucidate dynamics of landscape change. This study illustrates the effectiveness of object-oriented classification compared to pixel-oriented classification in generating land cover information and its temporal changes. Spatio-temporal dynamics of land cover types in Vientiane area, Lao PDR were analyzed using Landsat images in two-time series (1990 and 2015). We used the topdown approach to classify the Landsat images in iterative steps with three hierarchical scale levels. Scale levels of 25, 10 and 5 with different weighting parameters were used to map the land cover type of Vientiane in 1990 and 2015. With object-oriented classification, overall accuracy and Kappa statistic were improved by 13.44% and 0.16 for land cover classification (LCC) 1990. For LCC 2015, the improvements in overall accuracy and Kappa statistic were 28.71% and 0.25. Based on the LCC 1990 and 2015, we observed an significant growth of plantation areas over the 25 years in the study area. Instead of traditional agricultural activity, the plantation seemed to be the new driver in the rural areas of Lao PDR. The object-oriented classification approach can be applied in other areas of Lao PDR to generate accurate information on land cover changes for better land resource management.
Biogeosciences and Forestry Biogeosciences and Forestry Seeing trees from space: above-ground bio... more Biogeosciences and Forestry Biogeosciences and Forestry Seeing trees from space: above-ground biomass estimates of intact and degraded montane rainforests from high-resolution optical imagery Mui-How Phua (1) , Zia-Yiing Ling (1) , David Anthony Coomes (2) , Wilson Wong (1) , Alexius Korom (1) , Satoshi Tsuyuki (3) , Keiko Ioki (1) , Yasumasa Hirata (4) , Hideki Saito (4) , Gen Takao (4) Accurately quantifying the above-ground carbon stock of tropical rainforest trees is the core component of "Reduction of Emissions from Deforestation and Forest Degradation-plus" (REDD+) projects and is important for evaluating the effects of anthropogenic global change. We used high-resolution optical imagery (IKONOS-2) to identify individual tree crowns in intact and degraded rainforests in the mountains of Northern Borneo, comparing our results with 50 ground-based plots dispersed in intact and degraded forests, within which all stems > 10 cm in diameter were measured and identified to species or genus. We used the dimensions of tree crowns detected in the imagery to estimate above-ground biomasses (AGBs) of individual trees and plots. To this purpose, preprocessed IKONOS imagery was segmented using a watershed algorithm; stem diameter values were then estimated from the cross-sectional crown areas of these trees using regression relationships obtained from ground-based measurements. Finally, we calculated the biomass of each tree (AGBT, in kg), and the AGB of plots by summation (AGBP, in Mg ha-1). Remotely sensed estimates of mean AGBT were similar to ground-based estimates in intact and degraded forests, even though small trees could not be detected from space-borne sensors. The intact and degraded forests not only had different AGB but were also dissimilar in biodiversity. A tree-centric approach to carbon mapping based on high-resolution optical imagery, could be a cheap alternative to airborne laser-scanning.
IOP Conference Series: Earth and Environmental Science, 2014
Oil palm (OP) is the most commercial crop in Malaysia. Estimating the crowns is important for bio... more Oil palm (OP) is the most commercial crop in Malaysia. Estimating the crowns is important for biomass estimation from high resolution satellite (HRS) image. This study examined extraction of individual OP crown from a WorldView-2 image using twofold algorithms, i.e., masking of Non-OP pixels and detection of individual OP crown based
Estimating Aboveground Biomass of a Tropical Forest in Northern Borneo Based on Individual Tree Crowns from Ikonos 2 Data
Estimation of AGB and carbon of tropical forests has been a crucial factor to 'Reduction of c... more Estimation of AGB and carbon of tropical forests has been a crucial factor to 'Reduction of carbon emissions from deforestation and forest degradation-plus', a monetary mechanism for combating global warming. We examined the use of IKONOS 2 data for estimating aboveground biomass of a tropical forest in Long Mio, Sabah, Malaysia. The IKONOS 2 data was corrected for path radiance and topographic effect before segmentation using the watershed method in ArcGIS. Correlation analyses between the segment variables and forest variables revealed that crown area extracted from the IKONOS 2 data (CA s) had the strongest correlation with the field-measured diameter at breast height (DBH f). Linear regression analysis produced a model to estimate DBH f using CA s with R 2 of 0.71. Cross-validation using the remaining half of the data set also showed very consistent result. The CA s only represented upper canopy trees but estimated about 80% of the aboveground biomass.
Estimating above-ground biomass is important in establishing an applicable methodology of Measure... more Estimating above-ground biomass is important in establishing an applicable methodology of Measurement, Reporting and Verification (MRV) System for Reducing Emissions from Deforestation and Forest Degradation-Plus (REDD+). We developed an estimation model of diameter at breast height (DBH) from IKONOS-2 image that led to above-ground biomass estimation (AGB). The IKONOS image was preprocessed with dark object subtraction and topographic effect correction prior to watershed segmentation for tree crown delineation. Compared to the field observation, the overall segmentation accuracy was 64%. Crown detection percent had a strong negative correlation to tree density. In addition, satellite-based crown area had the highest correlation with the field measured DBH. We then developed the DBH allometric model that explained 74% of the data variance. In average, the estimated DBH was very similar to the measured DBH as well as for AGB. Overall, this method can potentially be applied to estimate AGB over a relatively large and remote tropical forest in Northern Borneo.
Assessing forest degradation is increasingly important to support a transparent and reliable repo... more Assessing forest degradation is increasingly important to support a transparent and reliable reporting system for Reduced Emission from Deforestation and Forest Degradation-plus (REDD+) in combating the climate change. Exploration of forest degradation is still insufficient in the tropical region. In this paper, the logged-over Tangkulap and Deramakot Forest Reserves in Sabah, Malaysia-Borneo were thoroughly studied. Using the IKONOS-2 image, forest was segmented based on multi-resolution algorithm in eCognition and classified into forest degradation types. AGB was used to guide the classification into three levels of forest degradation i.e. very-degraded (VDF), degraded (DF) and intact forests (IF). The accuracy was assessed at 0.65 of Kappa coefficient (79% of overall accuracy). Under each forest degradation class, the distribution patterns of tree densities and AGBs at the respective strata of understory, canopy and emergent were examined. Statistical mean and standard deviation were used to describe the variation patterns. Tree density of understory strata is saturating at DF and IFs. Tree density of emergent strata at IF is about twice higher than at DF. AGB at IF is 3.6 and 1.8 times higher than at VDF and DF, respectively. Standard deviation of AGB tends to increase nonlinearly from VDF to IF. This study has examined the patterns of tree density and AGB in order to understand the recovery processes of the degraded forest.
Assessing intraspecific wood density variations of Syzgium sp. in tropical forest of Southwest Sabah
IOP Conference Series: Earth and Environmental Science
Wood density (WD) is a critical determinant of estimating forest above-ground biomass (AGB) and c... more Wood density (WD) is a critical determinant of estimating forest above-ground biomass (AGB) and carbon stock. Thus, heterogeneity in WD on individuals within species trees needs to be scrutinized, and acquisition of fixed WD value is essential to estimate carbon stock with confidence. This study investigated intraspecific variation in WD of Syzgium sp., also known as “Jambu” or “Kelat”. It is the most occurring species in study areas, and is regarded as an economically important species. Firstly, one half-diameter drilling from bark-to-pith measurement was taken per tree using Rinntech Resistograph R650-ED at breast height. Meanwhile, 5.15 mm-diameter core was sampled at 1.30 m above-ground, with DeWalt DCF899HP2 20V impact wrench 950 Nm and Haglöf increment borer. WD was estimated for each core sample using a dimensional method. Drilling resistance (DR) profiles were processed using DECOM 2.38m1 Scientific (c), and several independent variables were extracted from the resistogram. ...
Pembangunan sukan di Sabah : penyelidikan padang bola sepak berumput turf di sekitar zon pantai barat Sabah menggunakan GIS / Alexius Korom and Haijon Gunggut
Bola sepak adalah sejenis sukan di luar rumah (outdoor) yang dimainkan di padang bola sepak atau ... more Bola sepak adalah sejenis sukan di luar rumah (outdoor) yang dimainkan di padang bola sepak atau kawasan lapang yang berumput turf biasanya jenis 'Cowgrass'. Objektif kajian adalah memperoleh data berkenaan padang bola sepak di sekitar Bandaraya Kota Kinabalu seperti jenis rumput, saiz, pemilik/pentdbir padang, jenis aktiviti yang dijalankan, kadar sewa, kecerunan dan kualiti penjagaan padang. Ini bertujuan untuk mengujudkan databes GIS padang-padang bola sepak di sekitar kawasan Zon Pantai Barat Sabah. Kaedah yang yang digunakan ialah pemeriksaan lapangan selepas pengenalpastian padang bola sepak melalui GIS. Sebanyak 45 padang telah diperiksa pada Ogos dan September 2009. Hasil kajian menunjukkan bahawa dari segi jenis rumput, semua padang yang ditinjau adalah berumput campuran (mixed grass). Dari segi saiz pula, majoriti padang memenuhi piawai saiz padang biasa. Kebanyakan padang yang ada dimiliki Lembaga Sukan Sabah atau organisasi berkaitan pendidikan (sekolah/kolej/uni...
Aboveground biomass assessment of degraded rainforest using IKONOS-2: specific forest cluster analysis
Accurate estimation of aboveground biomass (AGB) has increasingly important especially dealing wi... more Accurate estimation of aboveground biomass (AGB) has increasingly important especially dealing with various levels of forest degradation. Exploration of forest texture and forest structure helps to define forest type which shaping a distribution of AGB. In this study, high resolution satellite imagery of IKONOS-2 was used to assess the AGB of tropical Borneo rainforest at specific degradation level. Study site consists of degraded lowland Dipterocarp forest located at Tangkulap forest reserves in Sabah. The satellite image was segmented using eCognition and classified into three specific levels of forest cluster that are early, mid and late-successional forest. Field plots were assigned to the cluster by AGB to reflect the degradation levels. Multiple stepwise regression analyses were performed between AGB and independent variables of spectral and textural properties. The resulted estimation models of AGB within each forest cluster level had R2 ranging from 0.65 to 0.70 (Pearson coe...
The information on biophysical parameters—such as height, crown area, and vegetation indices such... more The information on biophysical parameters—such as height, crown area, and vegetation indices such as the normalized difference vegetation index (NDVI) and normalized difference red edge index (NDRE)—are useful to monitor health conditions and the growth of oil palm trees in precision agriculture practices. The use of multispectral sensors mounted on unmanned aerial vehicles (UAV) provides high spatio-temporal resolution data to study plant health. However, the influence of UAV altitude when extracting biophysical parameters of oil palm from a multispectral sensor has not yet been well explored. Therefore, this study utilized the MicaSense RedEdge sensor mounted on a DJI Phantom–4 UAV platform for aerial photogrammetry. Three different close-range multispectral aerial images were acquired at a flight altitude of 20 m, 60 m, and 80 m above ground level (AGL) over the young oil palm plantation area in Malaysia. The images were processed using the structure from motion (SfM) technique i...
Oil palms (OP) in Sabah, Malaysia were studied to explore the relationship between canopy size an... more Oil palms (OP) in Sabah, Malaysia were studied to explore the relationship between canopy size and aboveground biomass (AGB). Four available allometric equations were used to calculate the dry AGB. Pearson's correlation analysis was performed between crown diameter (CD) and crown area (CA) towards the variables of AGB, height and dbh. In this analysis, the transformation to natural log of variable resulted in better coefficient compared to the original one. The mean of various variables such as height (stem, total and height difference), biomass (crown, trunk and total), dbh (inner and outer) and number of petiole leaf were calculated based on 32 independent sample plots (N = 222 palms) across various age stages from 2 to 24 years. These variables were regressed against CD and age. AGB versus CD was a nonlinear with R2 ranging from 0.950 to 0.975. Random modelling and cross validation between AGB and CD was applied at the ratio of 70:30. Upon checking, the best estimation was ac...
Estimating tree height and above ground biomass of tropical rainforest across different degradation levels in malaysian borneo using airborne lidar data
Climage Change Office, Forestry and Forest Products Research Institute, Tsukuba, Japan, e-mail: h... more Climage Change Office, Forestry and Forest Products Research Institute, Tsukuba, Japan, e-mail: hirat09@affrc.go.jp School of International Tropical Forestry, Universiti Malaysia Sabah, Kota Kinabalu, Sabah, Nalaysia, e-mail: pmh@ums.edu.my, w.wilson@ums.edu.my Kyusyu Research Center, Forestry and Forest Products Research Institute, Kumamoto, Japan, e-mail: rslsaito@ffpri.affrc.go.jp Department of Forest Management, Forestry and Forest Products Research Institute, Tsukuba, Japan, e-mail: matsuu50@affrc.go.jp Universiti Teknologi MARA Sabah Branch, Kota Kinabalu, Sabah, Malaysia Graduate School of Agriculture, University of Kyoto, Kyoto, Japan
Exploring forest degradation: Tree density and aboveground biomass
Assessing forest degradation is increasingly important to support a transparent and reliable repo... more Assessing forest degradation is increasingly important to support a transparent and reliable reporting system for Reduced Emission from Deforestation and Forest Degradation-plus (REDD+) in combating the climate change. Exploration of forest degradation is still insufficient in the tropical region. In this paper, the logged-over Tangkulap and Deramakot Forest Reserves in Sabah, Malaysia-Borneo were thoroughly studied. Using the IKONOS-2 image, forest was segmented based on multi-resolution algorithm in eCognition and classified into forest degradation types. AGB was used to guide the classification into three levels of forest degradation i.e. very-degraded (VDF), degraded (DF) and intact forests (IF). The accuracy was assessed at 0.65 of Kappa coefficient (79% of overall accuracy). Under each forest degradation class, the distribution patterns of tree densities and AGBs at the respective strata of understory, canopy and emergent were examined. Statistical mean and standard deviation were used to describe the variation patterns. Tree density of understory strata is saturating at DF and IFs. Tree density of emergent strata at IF is about twice higher than at DF. AGB at IF is 3.6 and 1.8 times higher than at VDF and DF, respectively. Standard deviation of AGB tends to increase nonlinearly from VDF to IF. This study has examined the patterns of tree density and AGB in order to understand the recovery processes of the degraded forest.
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2019
Malaysia currently is one of the biggest global producers and exporters of palm oil. The world's ... more Malaysia currently is one of the biggest global producers and exporters of palm oil. The world's expanding oil palm plantation areas contribute to climate change and in-return, climate is change also affecting the health of oil palms through a range of abiotic and biotic stresses. Current advancements in Precision Agriculture research using UAV gives an advantage to detect the health conditions of oil palm at early stages. Thus, remedial actions can be taken to prolong the life and increase oil palms productivity. This paper explores the use of UAV derived NDVI and CPA of young oil palm to detect the health conditions. NDVI of individual oil palm were extracted using ground masking layer from the dense point clouds and visual on-screen manual editing was done for removing trees other than oil palm in ENVI software. The classified individual crown NDVI were then processed to extract the mean NDVI also conversion to vector to obtain the individual crown outline. Extracted mean NDVI was classified into un-healthy and healthy trees while the CPA was classified into small, medium and big size classes. These classes of NDVI and CPA were analysed using GIS overlay method thus revealing the spatial patterns of individual oil palm trees and its health conditions. Overall, the majority of oil palm trees of the study area are healthy but average performing. However, few oil palm trees detected having health problems which has low NDVI and small CPA. This study demonstrates that biophysical parameters such as the CPA can be used to detect individual young oil palm trees health conditions and problems when combined with vegetation indices such as NDVI.
Monitoring of land use and land cover change using remote sensing is important to evaluate the im... more Monitoring of land use and land cover change using remote sensing is important to evaluate the impacts of anthropogenic activities on the environment. Digital change detection using post-classification can help to elucidate dynamics of landscape change. This study illustrates the effectiveness of object-oriented classification compared to pixel-oriented classification in generating land cover information and its temporal changes. Spatio-temporal dynamics of land cover types in Vientiane area, Lao PDR were analyzed using Landsat images in two-time series (1990 and 2015). We used the topdown approach to classify the Landsat images in iterative steps with three hierarchical scale levels. Scale levels of 25, 10 and 5 with different weighting parameters were used to map the land cover type of Vientiane in 1990 and 2015. With object-oriented classification, overall accuracy and Kappa statistic were improved by 13.44% and 0.16 for land cover classification (LCC) 1990. For LCC 2015, the improvements in overall accuracy and Kappa statistic were 28.71% and 0.25. Based on the LCC 1990 and 2015, we observed an significant growth of plantation areas over the 25 years in the study area. Instead of traditional agricultural activity, the plantation seemed to be the new driver in the rural areas of Lao PDR. The object-oriented classification approach can be applied in other areas of Lao PDR to generate accurate information on land cover changes for better land resource management.
Biogeosciences and Forestry Biogeosciences and Forestry Seeing trees from space: above-ground bio... more Biogeosciences and Forestry Biogeosciences and Forestry Seeing trees from space: above-ground biomass estimates of intact and degraded montane rainforests from high-resolution optical imagery Mui-How Phua (1) , Zia-Yiing Ling (1) , David Anthony Coomes (2) , Wilson Wong (1) , Alexius Korom (1) , Satoshi Tsuyuki (3) , Keiko Ioki (1) , Yasumasa Hirata (4) , Hideki Saito (4) , Gen Takao (4) Accurately quantifying the above-ground carbon stock of tropical rainforest trees is the core component of "Reduction of Emissions from Deforestation and Forest Degradation-plus" (REDD+) projects and is important for evaluating the effects of anthropogenic global change. We used high-resolution optical imagery (IKONOS-2) to identify individual tree crowns in intact and degraded rainforests in the mountains of Northern Borneo, comparing our results with 50 ground-based plots dispersed in intact and degraded forests, within which all stems > 10 cm in diameter were measured and identified to species or genus. We used the dimensions of tree crowns detected in the imagery to estimate above-ground biomasses (AGBs) of individual trees and plots. To this purpose, preprocessed IKONOS imagery was segmented using a watershed algorithm; stem diameter values were then estimated from the cross-sectional crown areas of these trees using regression relationships obtained from ground-based measurements. Finally, we calculated the biomass of each tree (AGBT, in kg), and the AGB of plots by summation (AGBP, in Mg ha-1). Remotely sensed estimates of mean AGBT were similar to ground-based estimates in intact and degraded forests, even though small trees could not be detected from space-borne sensors. The intact and degraded forests not only had different AGB but were also dissimilar in biodiversity. A tree-centric approach to carbon mapping based on high-resolution optical imagery, could be a cheap alternative to airborne laser-scanning.
IOP Conference Series: Earth and Environmental Science, 2014
Oil palm (OP) is the most commercial crop in Malaysia. Estimating the crowns is important for bio... more Oil palm (OP) is the most commercial crop in Malaysia. Estimating the crowns is important for biomass estimation from high resolution satellite (HRS) image. This study examined extraction of individual OP crown from a WorldView-2 image using twofold algorithms, i.e., masking of Non-OP pixels and detection of individual OP crown based
Estimating Aboveground Biomass of a Tropical Forest in Northern Borneo Based on Individual Tree Crowns from Ikonos 2 Data
Estimation of AGB and carbon of tropical forests has been a crucial factor to 'Reduction of c... more Estimation of AGB and carbon of tropical forests has been a crucial factor to 'Reduction of carbon emissions from deforestation and forest degradation-plus', a monetary mechanism for combating global warming. We examined the use of IKONOS 2 data for estimating aboveground biomass of a tropical forest in Long Mio, Sabah, Malaysia. The IKONOS 2 data was corrected for path radiance and topographic effect before segmentation using the watershed method in ArcGIS. Correlation analyses between the segment variables and forest variables revealed that crown area extracted from the IKONOS 2 data (CA s) had the strongest correlation with the field-measured diameter at breast height (DBH f). Linear regression analysis produced a model to estimate DBH f using CA s with R 2 of 0.71. Cross-validation using the remaining half of the data set also showed very consistent result. The CA s only represented upper canopy trees but estimated about 80% of the aboveground biomass.
Estimating above-ground biomass is important in establishing an applicable methodology of Measure... more Estimating above-ground biomass is important in establishing an applicable methodology of Measurement, Reporting and Verification (MRV) System for Reducing Emissions from Deforestation and Forest Degradation-Plus (REDD+). We developed an estimation model of diameter at breast height (DBH) from IKONOS-2 image that led to above-ground biomass estimation (AGB). The IKONOS image was preprocessed with dark object subtraction and topographic effect correction prior to watershed segmentation for tree crown delineation. Compared to the field observation, the overall segmentation accuracy was 64%. Crown detection percent had a strong negative correlation to tree density. In addition, satellite-based crown area had the highest correlation with the field measured DBH. We then developed the DBH allometric model that explained 74% of the data variance. In average, the estimated DBH was very similar to the measured DBH as well as for AGB. Overall, this method can potentially be applied to estimate AGB over a relatively large and remote tropical forest in Northern Borneo.
Assessing forest degradation is increasingly important to support a transparent and reliable repo... more Assessing forest degradation is increasingly important to support a transparent and reliable reporting system for Reduced Emission from Deforestation and Forest Degradation-plus (REDD+) in combating the climate change. Exploration of forest degradation is still insufficient in the tropical region. In this paper, the logged-over Tangkulap and Deramakot Forest Reserves in Sabah, Malaysia-Borneo were thoroughly studied. Using the IKONOS-2 image, forest was segmented based on multi-resolution algorithm in eCognition and classified into forest degradation types. AGB was used to guide the classification into three levels of forest degradation i.e. very-degraded (VDF), degraded (DF) and intact forests (IF). The accuracy was assessed at 0.65 of Kappa coefficient (79% of overall accuracy). Under each forest degradation class, the distribution patterns of tree densities and AGBs at the respective strata of understory, canopy and emergent were examined. Statistical mean and standard deviation were used to describe the variation patterns. Tree density of understory strata is saturating at DF and IFs. Tree density of emergent strata at IF is about twice higher than at DF. AGB at IF is 3.6 and 1.8 times higher than at VDF and DF, respectively. Standard deviation of AGB tends to increase nonlinearly from VDF to IF. This study has examined the patterns of tree density and AGB in order to understand the recovery processes of the degraded forest.
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Papers by Alexius Korom