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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #418547
Research Project: Knowledge Systems and Tools to Increase the Resilience and Sustainablity of Western Rangeland Agriculture

Location: Range Management Research

Title: Exploratory analysis of multivariate relationships among the Normalized Difference Vegetation Index, grazing behavior, and carbon gas emissions of beef cows grazing arid rangeland vegetation

Author
item SPETTER, M - New Mexico State University
item Estell, Richard
item PEREA, A - New Mexico State University
item BAKIR, M - New Mexico State University
item FUNK, M - New Mexico State University
item Macon, Lara
item Bestelmeyer, Brandon
item Spiegal, Sheri
item UTSUMI, SANTIAGO - New Mexico State University

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2025
Publication Date: 2/13/2025
Citation: Spetter, M.J., Estell, R.E., Perea, A.R., Bakir, M., Funk, M.P., Macon, L.K., Bestelmeyer, B.T., Spiegal, S.A., Utsumi, S.A. 2025. Exploratory analysis of multivariate relationships among the Normalized Difference Vegetation Index, grazing behavior, and carbon gas emissions of beef cows grazing arid rangeland vegetation. Society for Range Management Meeting Abstracts. Abstract.

Interpretive Summary:

Technical Abstract: Ingestive mechanisms leading to ruminant and metabolic carbon gas emissions are well understood, but their response to environmental changes on arid rangelands remains unclear. This study investigated relationships among the Normalized Difference Vegetation Index (NDVI), grazing behavior variables, and carbon gas emissions using structural equation modeling (SEM). Sixty Raramuri Criollo (RC) and 29 Angus x Hereford (AH) cows were managed on two adjacent 2,500-ha pastures at USDA-ARS Jornada Experimental Range, NM, USA containing black grama (Bouteloa eriopoda), dropseed (Sporobolus cryptandrus), and mesquite (Prosopis glandulosa). From April 1 to August 15, 2024, vegetation cover was assessed using NDVI from Sentinel-2 L2A images. Grazing time (GrazTime, hours/day) and walking distance (WalkDist, km/day) were monitored using LoRaWAN GPS trackers with triaxial accelerometers. Graze rate (GrazRate, hours/km) was GrazTime/WalkDist. Methane (CH4, grams/day) and carbon dioxide (CO2, grams/day) fluxes were measured using the GreenFeed system (C-Lock Inc., Rapid City, SD). Multivariate relationships among the variables were explored using the 'lavaan' package in R software. NDVI had a direct negative effect on WalkDist (-0.39, p=0.02) with no effect on GrazTime (0.02, p=0.89). WalkDist had a direct negative effect on GrazRate (-0.76, p<0.001), while GrazTime had a direct positive effect on GrazRate (0.27, p=0.003). GrazRate showed a direct positive effect on CH4 (0.47, p=0.002) and CO2 (0.54, p<0.001) fluxes. Results suggest that higher NDVI is related to lower WalkDist, likely due to more available green forage, which decreases travel distance to forage. GrazRate, driven primarily by reduced WalkDist, may be associated with increased forage intake, leading to higher fermentation and metabolic activity, and consequently, increased CH4 and CO2 emission rate. Further studies are needed to explore differences between and within beef cattle biotypes, pasture, terrain and climatic conditions. NDVI appears to be an unbiased predictor of ruminant carbon fluxes on rangeland through its influence on GrazRate.