Mapping and characterizing selected canopy tree species at the Angkor World Heritage site in Cambodia using aerial data.

Minerva Singh,Boun Suy Tan,Chan Samean Nin,Damian Evans,Denis Loustau

doi:10.1371/journal.pone.0121558

Minerva Singh, Boun Suy Tan + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0121558

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Abstract

At present, there is very limited information on the ecology, distribution, and structure of Cambodia’s tree species to warrant suitable conservation measures. The aim of this study was to assess various methods of analysis of aerial imagery for characterization of the forest mensuration variables (i.e., tree height and crown width) of selected tree species found in the forested region around the temples of Angkor Thom, Cambodia. Object-based image analysis (OBIA) was used (using multiresolution segmentation) to delineate individual tree crowns from very-high-resolution (VHR) aerial imagery and light detection and ranging (LiDAR) data. Crown width and tree height values that were extracted using multiresolution segmentation showed a high level of congruence with field-measured values of the trees (Spearman’s rho 0.782 and 0.589, respectively). Individual tree crowns that were delineated from aerial imagery using multiresolution segmentation had a high level of segmentation accuracy (69.22%), whereas tree crowns delineated using watershed segmentation underestimated the field-measured tree crown widths. Both spectral angle mapper (SAM) and maximum likelihood (ML) classifications were applied to the aerial imagery for mapping of selected tree species. The latter was found to be more suitable for tree species classification. Individual tree species were identified with high accuracy. Inclusion of textural information further improved species identification, albeit marginally. Our findings suggest that VHR aerial imagery, in conjunction with OBIA-based segmentation methods (such as multiresolution segmentation) and supervised classification techniques are useful for tree species mapping and for studies of the forest mensuration variables.

Highlights

The concept of sacred or culturally important sites protecting small biodiversity-rich forest tracts exists in many countries
We briefly focused on examining the application of Object-based image analysis (OBIA)-based approaches to VHR aerial imagery for facilitation of individual tree studies
On the basis of both Kruskal-Wallis and Mood’s test of median difference, it can be concluded that multiresolution segmentation is a sound algorithm for individual tree crown delineation, whereas watershed segmentation underestimates field-measured crown tree widths

Summary

Introduction

The concept of sacred or culturally important sites protecting small biodiversity-rich forest tracts exists in many countries. The temple forests surrounding the great monuments of Angkor in Northwestern Cambodia are examples of forested areas that are deeply linked to identity, culture, and sacred beliefs. These areas have evolved along a distinctly different historical trajectory compared to other forests in the surrounding areas because of regulatory frameworks that have defined the former as areas of cultural significance [3,4,5,6]. In recent decades, Cambodia has seen a sharp increase in deforestation Important forests such as those in Angkor are facing increased pressure, mainly due to increased infrastructure development and an influx of tourists [5]. Utilization of advanced forest monitoring techniques is crucial for ensuring long-term survival of Cambodia’s forests, sacred or otherwise

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