Abstract
Mapping the distribution of forested areas and monitoring their spatio-temporal changes are necessary for the conservation and management of forests. This paper presents two new image composites for the visualization and extraction of forest cover. By exploiting the Landsat-8 satellite-based multi-temporal and multi-spectral reflectance datasets, the Forest Cover Composite (FCC) was designed in this research. The FCC is an RGB (red, green, blue) color composite made up of short-wave infrared reflectance and green reflectance, specially selected from the day when the Normalized Difference Vegetation Index (NDVI) is at a maximum, as the red and blue bands, respectively. The annual mean NDVI values are used as the green band. The FCC is designed in such a way that the forested areas appear greener than other vegetation types, such as grasses and shrubs. On the other hand, the croplands and barren lands are usually seen as red and water/snow is seen as blue. However, forests may not necessarily be greener than other perennial vegetation. To cope with this problem, an Enhanced Forest Cover Composite (EFCC) was designed by combining the annual median backscattering intensity of the VH (vertical transmit, horizontal receive) polarization data from the Sentinel-1 satellite with the green term of the FCC to suppress the green component (mean NDVI values) of the FCC over the non-forested vegetative areas. The performances of the FCC and EFCC were evaluated for the discrimination and classification of forested areas all over Japan with the support of reference data. The FCC and EFCC provided promising results, and the high-resolution forest map newly produced in the research provided better accuracy than the extant MODIS (Moderate Resolution Imaging Spectroradiometer) Land Cover Type product (MCD12Q1) in Japan. The composite images proposed in the research are expected to improve forest monitoring activities in other regions as well.
Highlights
Forests are the prominent terrestrial plant communities dominated by trees, and they are essential for sustaining the life on Earth
Combinations of Forest Cover Composite (FCC) and Enhanced Forest Cover Composite (EFCC), or Biophysical Image Composite (BIC), FCC, and EFCC did not provide improvements over the EFCC alone. This analysis confirmed that the FCC and EFCC are efficient composite images for the extraction and visualization of forested areas
This paper presented image compositing techniques for the visualization and extraction of forested areas on a national scale
Summary
Forests are the prominent terrestrial plant communities dominated by trees, and they are essential for sustaining the life on Earth. Forests have been in a constant state of change with a variety of natural, climatic, and anthropogenic factors worldwide [1,2,3]. The global forest area fell by 3% from. J. Imaging 2018, 4, 105; doi:10.3390/jimaging4090105 www.mdpi.com/journal/jimaging. Rates of forest loss are highest in low income countries [4]. The unprecedented changes in forested areas due to human activities over the past couple of centuries have attracted great attention worldwide [5,6,7,8,9]. Up-to-date and precise information on forest cover dynamics is necessary to the conservation and management of forests as well as essential to a better understanding of future climates [10,11,12,13]
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