Very high-resolution true color leaf-off imagery for mapping Taxus baccata L. and Ilex aquifolium L. understory population.
Author(s)
Date Issued
2020
Type
article
Volume
29
Issue
8
Start Page
2605
End Page
2622
Journal
Abstract
According to the ‘‘Habitat’’ Directive 92/43/EEC, the conservation status of natural
habitats depends on the occurrence of populations of their typical species. For some forest
habitats, typical species do not occur as canopy dominant trees but are found in the
understory. This is the case with the priority habitat ’‘Apennine beech forests with Taxus
and Ilex’’ 9210*. Taxus baccata L. and Ilex aquifolium L. are evergreen tree species and
occur as isolated trees or groups in the understory of beech dominated forests. Accordingly,
the knowledge of the spatial pattern of populations of typical species is fundamental for
habitat monitoring goals. In this perspective, this study aims to evaluate the potential of
very high-resolution, true color, leaf-off imagery (pixel size = 0.11 m), supplied by Google
Earth, for mapping these populations. Understory layer detection has been accomplished
through an object-oriented approach, based on multiresolution segmentation. The classification
was developed with thresholds based on spectral and geometric properties, as well
as on textural and contextual information. The main critical issues are represented by site
conditions, where shadowing can prevent crown detection. The thematic accuracy of the
target species map resulted in a Producer Accuracy of 0.77 and a User Accuracy of 0.80.
The proposed procedure offers a good methodological foundation with which to map the
actual spatial extent of forest broadleaved deciduous habitat types, characterized by low
abundance and patchily distributed populations of yew and holly.