Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest
Windthrow (i.e., trees broken and uprooted by wind) is a major natural disturbance in Amazon forests. Images from medium-resolution optical satellites combined with extensive field data have allowed researchers to assess patterns of windthrow tree-mortality and to monitor forest recovery over decade...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-08-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/15/16/4027 |
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| author | Luciano Emmert Robinson Isaac Negrón-Juárez Jeffrey Quintin Chambers Joaquim dos Santos Adriano José Nogueira Lima Susan Trumbore Daniel Magnabosco Marra |
| author_facet | Luciano Emmert Robinson Isaac Negrón-Juárez Jeffrey Quintin Chambers Joaquim dos Santos Adriano José Nogueira Lima Susan Trumbore Daniel Magnabosco Marra |
| author_sort | Luciano Emmert |
| collection | DOAJ |
| description | Windthrow (i.e., trees broken and uprooted by wind) is a major natural disturbance in Amazon forests. Images from medium-resolution optical satellites combined with extensive field data have allowed researchers to assess patterns of windthrow tree-mortality and to monitor forest recovery over decades of succession in different regions. Although satellites with high spatial-resolution have become available in the last decade, they have not yet been employed for the quantification of windthrow tree-mortality. Here, we address how increasing the spatial resolution of satellites affects plot-to-landscape estimates of windthrow tree-mortality. We combined forest inventory data with Landsat 8 (30 m pixel), Sentinel 2 (10 m), and WorldView 2 (2 m) imagery over an old-growth forest in the Central Amazon that was disturbed by a single windthrow event in November 2015. Remote sensing estimates of windthrow tree-mortality were produced from Spectral Mixture Analysis and evaluated with forest inventory data (i.e., ground true) by using Generalized Linear Models. Field measured windthrow tree-mortality (3 transects and 30 subplots) crossing the entire disturbance gradient was 26.9 ± 11.1% (mean ± 95% CI). Although the three satellites produced reliable and statistically similar estimates (from 26.5% to 30.3%, <i>p</i> < 0.001), Landsat 8 had the most accurate results and efficiently captured field-observed variations in windthrow tree-mortality across the entire gradient of disturbance (Sentinel 2 and WorldView 2 produced the second and third best results, respectively). As expected, mean-associated uncertainties decreased systematically with increasing spatial resolution (i.e., from Landsat 8 to Sentinel 2 and WorldView 2). However, the overall quality of model fits showed the opposite pattern. We suggest that this reflects the influence of a relatively minor disturbance, such as defoliation and crown damage, and the fast growth of natural regeneration, which were not measured in the field nor can be captured by coarser resolution imagery. Our results validate the reliability of Landsat imagery for assessing plot-to-landscape patterns of windthrow tree-mortality in dense and heterogeneous tropical forests. Satellites with high spatial resolution can improve estimates of windthrow severity by allowing the quantification of crown damage and mortality of lower canopy and understory trees. However, this requires the validation of remote sensing metrics using field data at compatible scales. |
| first_indexed | 2024-03-10T23:36:13Z |
| format | Article |
| id | doaj.art-088bf8d30cdf40a69bf193bec07e8f3e |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T23:36:13Z |
| publishDate | 2023-08-01 |
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| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-088bf8d30cdf40a69bf193bec07e8f3e2023-11-19T02:53:31ZengMDPI AGRemote Sensing2072-42922023-08-011516402710.3390/rs15164027Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon ForestLuciano Emmert0Robinson Isaac Negrón-Juárez1Jeffrey Quintin Chambers2Joaquim dos Santos3Adriano José Nogueira Lima4Susan Trumbore5Daniel Magnabosco Marra6Forest Management Laboratory, National Institute of Amazon Research, Manaus 69060-062, AM, BrazilClimate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USAClimate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USAForest Management Laboratory, National Institute of Amazon Research, Manaus 69060-062, AM, BrazilForest Management Laboratory, National Institute of Amazon Research, Manaus 69060-062, AM, BrazilBiogeochemical Processes Department, Max Planck Institute for Biochemistry, 07745 Jena, GermanyBiogeochemical Processes Department, Max Planck Institute for Biochemistry, 07745 Jena, GermanyWindthrow (i.e., trees broken and uprooted by wind) is a major natural disturbance in Amazon forests. Images from medium-resolution optical satellites combined with extensive field data have allowed researchers to assess patterns of windthrow tree-mortality and to monitor forest recovery over decades of succession in different regions. Although satellites with high spatial-resolution have become available in the last decade, they have not yet been employed for the quantification of windthrow tree-mortality. Here, we address how increasing the spatial resolution of satellites affects plot-to-landscape estimates of windthrow tree-mortality. We combined forest inventory data with Landsat 8 (30 m pixel), Sentinel 2 (10 m), and WorldView 2 (2 m) imagery over an old-growth forest in the Central Amazon that was disturbed by a single windthrow event in November 2015. Remote sensing estimates of windthrow tree-mortality were produced from Spectral Mixture Analysis and evaluated with forest inventory data (i.e., ground true) by using Generalized Linear Models. Field measured windthrow tree-mortality (3 transects and 30 subplots) crossing the entire disturbance gradient was 26.9 ± 11.1% (mean ± 95% CI). Although the three satellites produced reliable and statistically similar estimates (from 26.5% to 30.3%, <i>p</i> < 0.001), Landsat 8 had the most accurate results and efficiently captured field-observed variations in windthrow tree-mortality across the entire gradient of disturbance (Sentinel 2 and WorldView 2 produced the second and third best results, respectively). As expected, mean-associated uncertainties decreased systematically with increasing spatial resolution (i.e., from Landsat 8 to Sentinel 2 and WorldView 2). However, the overall quality of model fits showed the opposite pattern. We suggest that this reflects the influence of a relatively minor disturbance, such as defoliation and crown damage, and the fast growth of natural regeneration, which were not measured in the field nor can be captured by coarser resolution imagery. Our results validate the reliability of Landsat imagery for assessing plot-to-landscape patterns of windthrow tree-mortality in dense and heterogeneous tropical forests. Satellites with high spatial resolution can improve estimates of windthrow severity by allowing the quantification of crown damage and mortality of lower canopy and understory trees. However, this requires the validation of remote sensing metrics using field data at compatible scales.https://www.mdpi.com/2072-4292/15/16/4027blowdownscrown damageforest inventoryextreme wind gustsnatural disturbancesspatial resolution |
| spellingShingle | Luciano Emmert Robinson Isaac Negrón-Juárez Jeffrey Quintin Chambers Joaquim dos Santos Adriano José Nogueira Lima Susan Trumbore Daniel Magnabosco Marra Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest Remote Sensing blowdowns crown damage forest inventory extreme wind gusts natural disturbances spatial resolution |
| title | Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest |
| title_full | Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest |
| title_fullStr | Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest |
| title_full_unstemmed | Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest |
| title_short | Sensitivity of Optical Satellites to Estimate Windthrow Tree-Mortality in a Central Amazon Forest |
| title_sort | sensitivity of optical satellites to estimate windthrow tree mortality in a central amazon forest |
| topic | blowdowns crown damage forest inventory extreme wind gusts natural disturbances spatial resolution |
| url | https://www.mdpi.com/2072-4292/15/16/4027 |
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