Patch-burn management changes grazing behavior of cattle in humid subtropical grasslands

Abstract

Humid, subtropical grazing lands utilized for cattle production are significant agroecosystems that are important for economic production, global food security, and biodiversity. Prescribed fire, an important management tool, is used for controlling woody plant encroachment, maintaining wildlife habitat, and stimulating forage regrowth. Fire also interacts with grazing to maintain grassland structure and heterogeneity. Understanding this fire-grazing interaction is important to producers because spatio-temporal cattle behavior has been linked to both livestock production and environmental impact through patterns of pasture utilization. The goal of the study was to understand how two fire regimes affected spatial and temporal grazing behavior, including grazing intensity, grazing evenness, and circadian and seasonal grazing patterns. A randomized block design experiment was established in 2017 with 16 pastures (16 ha each), at Archbold Biological Station’s Buck Island Ranch in FL, USA. We examined two prescribed fire management techniques, one represented the prevailing practice of the region with prescribed fire applied to entire pastures (full burn = FB), and the other ‘alternative’ regime applied patch-burn (PB), in which one-third of a pasture was burned each year. Here we present results from the first year of the study, after the first patch-burns and the full burns were implemented. Global Positioning System data loggers on cows recorded 5-min location fixes to track cows and cattle grazing behavior was inferred based on distances between GPS locations. Cattle behavior was significantly different in PB vs. FB pastures. Over a year with five grazing periods, cattle spent on average 38% more time grazing in burned vs unburned patches within PB pastures. PB burned patches were also grazed with a more even spatial distribution compared to unburned patches. In contrast, in FB pastures, cattle grazing intensity and evenness were similar across the entire pasture. Time of day, temperature, season, and fire treatment all had small effects on the circadian cattle grazing patterns. Our study suggests that PB can be a management tool to manipulate cattle behavior in humid subtropical grazinglands, with potential implications for pasture utilization and beef production, carbon and nutrient cycling, and wildlife habitat.