Abstract
Pine processionary moth (PPM) feeds on conifer foliage and periodically result in outbreaks leading to large scale defoliation, causing decreased tree growth, vitality and tree reproduction capacity. Multispectral high-resolution imagery acquired from a UAS platform was successfully used to assess pest tree damage at the tree level in a pine-oak mixed forest. We generated point clouds and multispectral orthomosaics from UAS through photogrammetric processes. These were used to automatically delineate individual tree crowns and calculate vegetation indices such as the normalized difference vegetation index (NDVI) and excess green index (ExG) to objectively quantify defoliation of trees previously identified. Overall, our research suggests that UAS imagery and its derived products enable robust estimation of tree crowns with acceptable accuracy and the assessment of tree defoliation by classifying trees along a gradient from completely defoliated to non-defoliated automatically with 81.8% overall accuracy. The promising results presented in this work should inspire further research and applications involving a combination of methods allowing the scaling up of the results on multispectral imagery by integrating satellite remote sensing information in the assessments over large spatial scales.
Highlights
The area covered by forest ecosystems in the Mediterranean has increased during the last century due to land abandonment and climate change impacts, which have led to significant changes in forest dynamics [1,2,3]
The accuracy of the automatic identification and delineation (ITDe) was analyzed in comparison to the manual tree crown delineation (MCDe) on the orthomosaic
We investigated the use of multispectral high-resolution imagery acquired from a unmanned aerial systems (UAS) platform and image processing techniques to quantitatively assess Pine processionary moth (PPM) impact on a pine-oak mixed forest at tree level
Summary
The area covered by forest ecosystems in the Mediterranean has increased during the last century due to land abandonment and climate change impacts, which have led to significant changes in forest dynamics [1,2,3] These forest changes an increase in the effects of pests on trees, partially due to more frequent large-scale outbreaks becoming an increasingly important disturbance in forest dynamics [4,5]. Amongst these pests we can highlight the increasing impact of the pine processionary moth Tecnosylva, S.L. provided support in the form of salaries for author AC, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript
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