Photosynthetic Activity and Canopy Height Model Determined by UAV RGB and IR Close-Range Remote-Sensing in the High Andean Polylepis Relict Forest, Ecuador

Abstract

Unmanned aircraft systems are broadly used for ecological research and conservation efforts. The goal of this study was to document the status quo of the photosynthetic activity, spatial distribution, and some of the biometric characteristics of the High Andean Polylepis relict forest located in the “Reserva de Producción de Fauna Chimborazo”. Using RGB and IR sensors mounted on Unmanned Aerial Vehicles (UAVs), a multispectral image was obtained to calculate the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). From this image, a cloud of points was generated to determine the Digital Surface Model (DSM) and Digital Terrain Model (DTM). A layer of NDVI values was ranked between 0.708 and - 0.539 and a layer of EVI values was ranked between 0.00059 and - 0.00021 to consider all of the coverage types (forest cover, herbaceous vegetation, and rocky outcrop), with which it was demonstrated that the photosynthetic activity in the study area is low. The Canopy Height Model (CHM) was obtained as the difference between DSM and DTM. The methods described in this study could be used to document the conservation status of natural protected areas and to support biomass calculations for studies of carbon sequestration in the high Andean forests of Ecuador.