A Pilot Study to Estimate Forage Mass from Unmanned Aerial Vehicles in a Semi-Arid Rangeland

Alexandria M Dimaggio,Michael T Page,Humberto L Perotto-Baldivieso,Karelys N Labrador-Rodriguez,Chase Walther,David B Wester,Jose De La Luz Martinez,Brent C Hedquist,Sandra Rideout-Hanzak,J Alfonso Ortega-S

doi:10.3390/rs12152431

Alexandria M Dimaggio, Michael T Page + Show 8 more

Open Access

https://doi.org/10.3390/rs12152431

Copy DOI

Abstract

The application of unmanned aerial vehicles (UAVs) in the monitoring and management of rangelands has exponentially increased in recent years due to the miniaturization of sensors, ability to capture imagery with high spatial resolution, lower altitude platforms, and the ease of flying UAVs in remote environments. The aim of this research was to develop a method to estimate forage mass in rangelands using high-resolution imagery derived from the UAV using a South Texas pasture as a pilot site. The specific objectives of this research were to (1) evaluate the feasibility of quantifying forage mass in semi-arid rangelands using a double sampling technique with high-resolution imagery and (2) to compare the effect of altitude on forage mass estimation. Orthoimagery and digital surface models (DSM) with a resolution <1.5 cm were acquired with an UAV at altitudes of 30, 40, and 50 m above ground level (AGL) in Duval County, Texas. Field forage mass data were regressed on volumes obtained from a DSM. Our results show that volumes estimated with UAV data and forage mass as measured in the field have a significant relationship at all flight altitudes with best results at 30-m AGL (r2 = 0.65) and 50-m AGL (r2 = 0.63). Furthermore, the use of UAVs would allow one to collect a large number of samples using a non-destructive method to estimate available forage for grazing animals.

Highlights

Estimating forage standing crop [1] is crucial for resource inventory, assessment, and monitoring in livestock and rangeland management decision making
Digital surface models derived from unmanned aerial vehicles (UAVs) imagery can be used to estimate forage mass on rangelands
This is one of the first studies conducted in a semi-arid rangeland to compare flight altitudes for forage mass estimation using high resolution imagery derived from an UAV and sampling imagery in a similar way to field-based methodologies

Summary

Introduction

Estimating forage standing crop (hereafter ‘forage mass’) [1] is crucial for resource inventory, assessment, and monitoring in livestock and rangeland management decision making. The number of samples and the area covered may be insufficient to adequately estimate total available forage mass in large pastures [6] This can be even more difficult in semi-arid rangelands because these areas are highly dependent on the scarce rainfall events that occur within a growing season. These weather events are usually unpredictable and quickly change the structure, size, and canopy coverage of the plants [7,8]. This temporal variability in vegetation growth requires resource estimates to be made upon short notice, and accurately, to keep up with these dynamic processes and provide valuable vegetation information

Objectives

Methods

Results

Discussion

Conclusion