Located at the Marine Corps Air Station (MCAS) in Yuma, Arizona, this research initiative investigates the effectiveness of adaptive grazing management as a conservation tool for arid rangeland landscapes. The study compares the ecological impacts of grazing cattle against total grazing exclusion to determine which method best fosters ecosystem resilience through improved soil infiltration, overall soil health, and vegetation improvement.

Key Project Highlights

Research is conducted on arid rangelands at MCAS Yuma, utilizing stratified sampling based on ecological sites and soil types. The study compares two distinct scenarios: High Stock Density (>80,000 lbs live weight/ac and No Grazing (control).

The primary goals are to quantify impacts on dynamic soil properties (moisture and health), vegetation characteristics (structure, function, and quantity) and wildlife monitoring using advanced tools, including autonomous recorders for bird detection, advanced wildlife cameras, solar-powered cellular data loggers for soil moisture, Vegetation GIS Software System (VGS) for managing line point data.

Results will benefit the USMC, policymakers, and ranchers operating in similar arid regions worldwide by validating working lands conservation strategies. This study addresses a critical gap in understanding how grazing intensity and timing affect soil health indices in arid environments. By treating the ecosystem as an interconnected web by linking grazers, vegetation, soil, and wildlife this project moves beyond simple observation to understanding the mechanisms of restoration ecology.

The project operates on the hypothesis that managed disturbance by herbivory, in this case cattle, can positively impact ecosystem services. Rather than simply releasing cattle, the study employs “adaptive planned grazing” with specific density targets. Researchers will monitor these treatments over two years, recording grazing management application and measuring vegetative recovery to see if active management outperforms the control strategy of grazing exclusion.

Soil degradability is a major threat to arid rangeland resilience. To measure the impact of the grazing treatments, the team is deploying a rigorous sampling regime:

• Intact soil cores (0-30 cm) are collected and split into depths of 0-10 cm and 10-30 cm for analysis.
• Samples are analyzed for bulk density, aggregate stability, water-holding capacity, active carbon, and microbial respiration.
• The potential for nutrient cycling is measured using specific enzymes, including β-glucosidase (carbon cycling) and N-acetyl-β-glycosaminidase (carbon and nitrogen cycling).
• Solar-powered sensors installed at depths ranging from 4 , 8 , 12 inches provide continuous data on soil moisture dynamics.

Rangeland resilience relies heavily on native vegetation. The research team uses the Line-Point Intercept methodology to quantify soil cover and species composition from the canopy down to the soil surface. Data is analyzed using the Shannon Diversity Index to estimate species diversity within the community.

Metrics are captured before grazing, after recovery, and during the growing season to provide a complete picture of how the landscape responds to the different grazing intensities