A forestry GIS-based study on evaluating the potential of imaging spectroscopy in mapping forest land fertility |
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| Institution: | 1. Department of Forest Management and Applied Geoinformatics, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemědělská 3, 613 00 Brno, Czech Republic;2. Department of Biology, Faculty of Education, Palacky University, Olomouc, Purkrabská 2, 771 46 Olomouc, Czech Republic;3. Department of Geoinformatics, Faculty of Science, Palacky University, Olomouc, 17. listopadu 50, 771 46 Olomouc, Czech Republic;1. U.S. Geological Survey, Southwest Biological Science Center, Rm. 123, University of Arizona, 1110 E. So. Campus Drive, Tucson, AZ 85719, United States;2. U.S. Geological Survey, Core Science Analytics and Synthesis, Denver Federal Center Bldg. 810, Lakewood, CO 80225, United States;3. U.S. Geological Survey, USA National Phenology Network, 1955 E 6th St., Tucson, AZ 85721, United States;4. NOAA Fisheries Service, Office of Science and Technology, 1315 East West Highway, Silver Spring, MD 20910, United States;1. Center for Environmental Systems Research (CESR), University of Kassel, Germany;2. Geography Department, Humboldt-Universität zu Berlin, Germany;3. Integrative Research Institute on Transformations of Human-Environment Systems, Humboldt-Universität zu Berlin, Germany |
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| Abstract: | Fertility, or the availability of nutrients and water, controls forest productivity. It affects its carbon sequestration, and thus the forest's effect on climate, as well as its commercial value. Although the availability of nutrients cannot be measured directly using remote sensing methods, fertility alters several vegetation traits detectable from the reflectance spectra of the forest stand, including its pigment content and water stress. However, forest reflectance is also influenced by other factors, such as species composition and stand age. Here, we present a case study demonstrating how data obtained using imaging spectroscopy is correlated with site fertility. The study was carried out in Hyytiälä, Finland, in the southern boreal forest zone. We used a database of state-owned forest stands including basic forestry variables and a site fertility index. To test the suitability of imaging spectroscopy with different spatial and spectral resolutions for site fertility mapping, we performed two airborne acquisitions using different sensor configurations. First, the sensor was flown at a high altitude with high spectral resolution resulting in a pixel size in the order of a tree crown. Next, the same area was flown to provide reflectance data with sub-meter spatial resolution. However, to maintain usable signal-to-noise ratios, several spectral channels inside the sensor were combined, thus reducing spectral resolution. We correlated a number of narrowband vegetation indices (describing canopy biochemical composition, structure, and photosynthetic activity) on site fertility. Overall, site fertility had a significant influence on the vegetation indices but the strength of the correlation depended on dominant species. We found that high spatial resolution data calculated from the spectra of sunlit parts of tree crowns had the strongest correlation with site fertility. |
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| Keywords: | Airborne imaging spectroscopy Forest site fertility Narrowband vegetation index Sunlit crowns Boreal forest |
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