Assessment of forage production in pastoral rangelands using multispectral drone imagery data in the sahelian and sudanian zones of the West African sahel

The forage mass of herbaceous and woody plants is the main source of food for livestock in pastoral rangelands in the Sahelian and Sub-Danian zones. This study aims to assess the biomass of woody and herbaceous species using the normalized difference vegetation index NDVI derived from multispectral Red-Green-Blue and near-infrared drone images and photogrammetric parameters. A Dji Phantom multispectral UAV was used to collect images from four pilot sites in Niger and Benin. Ground measurements of herbaceous biomass using the integrated yield square method and estimation of woody leaf phytomass using dendrometric parameters calculated with allometric equations were used to assess the performance of the drone-based model. The results showed that the herbaceous biomass estimated with the drone had an R² coefficient of determination of 0.59-0.86 and relative root mean square estimation errors (RMSEr) of 19.86% to 26.84% with ground measurements, at a significance level of p < 0.0001. As for woody biomass, an R² of 0.58-0.69 and an RMSEr of 14.16% to 39.55% at a p-value < 0.0001 were obtained.