Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests
This study aims to reveal the relationships between understory coverage (principally, weed growth) beneath the canopies of Sumatran eucalyptus plantations and L-band backscatter data gathered by the PALSAR-2 Synthetic Aperture Radar (SAR) onboard the ALOS-2 satellite. Statistical analysis in conjunc...
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Taylor & Francis Group
2024-12-01
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| Series: | GIScience & Remote Sensing |
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| Online Access: | https://www.tandfonline.com/doi/10.1080/15481603.2024.2360771 |
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| author | Shoko Kobayashi Motoko S. Fujita Yoshiharu Omura John Philip Matthews |
| author_facet | Shoko Kobayashi Motoko S. Fujita Yoshiharu Omura John Philip Matthews |
| author_sort | Shoko Kobayashi |
| collection | DOAJ |
| description | This study aims to reveal the relationships between understory coverage (principally, weed growth) beneath the canopies of Sumatran eucalyptus plantations and L-band backscatter data gathered by the PALSAR-2 Synthetic Aperture Radar (SAR) onboard the ALOS-2 satellite. Statistical analysis in conjunction with in situ measurements of forest structural parameters reveals that the SAR polarization ratio is significantly negatively correlated with understory coverage in forests taller than or equal to 10 m or above 2 years of age. Our field investigations confirm that a decrease in canopy coverage takes place some 2 years after transplanting, which in turn permits increased penetration (decreased attenuation) of microwave signals thereby enabling the SAR to detect changes in understory coverage. In addition, both growth and unmanaged remnants of the understory vegetation in older forests reduce evaporation from the ground, which in turn stabilizes soil-moisture levels throughout the year and allows co-polarized backscatter data (which might otherwise be dominated by soil-moisture changes) to contain significant information on the underlying vegetation. No correlation between the understory and SAR backscatter was recorded in younger forests undergoing programs of intensive weed management. This is presumably because strong canopy and trunk backscatter obscured the response from understory vegetation and because artificial changes were induced in vegetation water content as a result of the application of herbicides which in turn reduced the accuracy of some of our field measurements of understory coverage. This research nevertheless demonstrates an important potential application of active satellite microwave remote sensing. We show that satellite-based L-band SAR can be used as a tool to investigate coverage percentages of understory layers. This synoptic technique reduces the need for repeated field surveys across large areas of forest. It can enhance ecosystem assessment and improve understory coverage estimates in sparse forests and in various types of plantations. |
| format | Article |
| id | doaj-art-8c20366858a445b8981f3171714f4a72 |
| institution | Kabale University |
| issn | 1548-1603 1943-7226 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | Taylor & Francis Group |
| record_format | Article |
| series | GIScience & Remote Sensing |
| spelling | doaj-art-8c20366858a445b8981f3171714f4a722024-12-06T13:51:50ZengTaylor & Francis GroupGIScience & Remote Sensing1548-16031943-72262024-12-0161110.1080/15481603.2024.2360771Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forestsShoko Kobayashi0Motoko S. Fujita1Yoshiharu Omura2John Philip Matthews3College of Agriculture, Tamagawa University, Tokyo, JapanCenter for Southeast Asian Studies, Kyoto University, Kyoto, JapanResearch Institute for Sustainable Humanosphere, Kyoto University, Kyoto, JapanEnvironmental Satellite Applications (ENSA), Anglesey, UKThis study aims to reveal the relationships between understory coverage (principally, weed growth) beneath the canopies of Sumatran eucalyptus plantations and L-band backscatter data gathered by the PALSAR-2 Synthetic Aperture Radar (SAR) onboard the ALOS-2 satellite. Statistical analysis in conjunction with in situ measurements of forest structural parameters reveals that the SAR polarization ratio is significantly negatively correlated with understory coverage in forests taller than or equal to 10 m or above 2 years of age. Our field investigations confirm that a decrease in canopy coverage takes place some 2 years after transplanting, which in turn permits increased penetration (decreased attenuation) of microwave signals thereby enabling the SAR to detect changes in understory coverage. In addition, both growth and unmanaged remnants of the understory vegetation in older forests reduce evaporation from the ground, which in turn stabilizes soil-moisture levels throughout the year and allows co-polarized backscatter data (which might otherwise be dominated by soil-moisture changes) to contain significant information on the underlying vegetation. No correlation between the understory and SAR backscatter was recorded in younger forests undergoing programs of intensive weed management. This is presumably because strong canopy and trunk backscatter obscured the response from understory vegetation and because artificial changes were induced in vegetation water content as a result of the application of herbicides which in turn reduced the accuracy of some of our field measurements of understory coverage. This research nevertheless demonstrates an important potential application of active satellite microwave remote sensing. We show that satellite-based L-band SAR can be used as a tool to investigate coverage percentages of understory layers. This synoptic technique reduces the need for repeated field surveys across large areas of forest. It can enhance ecosystem assessment and improve understory coverage estimates in sparse forests and in various types of plantations.https://www.tandfonline.com/doi/10.1080/15481603.2024.2360771ALOS-2PALSAR-2satellite microwave remote sensingforest structureunderstoryforest management |
| spellingShingle | Shoko Kobayashi Motoko S. Fujita Yoshiharu Omura John Philip Matthews Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests GIScience & Remote Sensing ALOS-2 PALSAR-2 satellite microwave remote sensing forest structure understory forest management |
| title | Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests |
| title_full | Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests |
| title_fullStr | Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests |
| title_full_unstemmed | Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests |
| title_short | Analysis of the relationship between L-band SAR backscatter and understory weed density in eucalyptus plantation forests |
| title_sort | analysis of the relationship between l band sar backscatter and understory weed density in eucalyptus plantation forests |
| topic | ALOS-2 PALSAR-2 satellite microwave remote sensing forest structure understory forest management |
| url | https://www.tandfonline.com/doi/10.1080/15481603.2024.2360771 |
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