Subtropical, humid grasslands (SHG) are an important global land-use, and support ~30% of the US beef herd. Research is lacking on how SHG management can be improved to sustain ecosystem services and economic viability. Patch-burn-grazing (PBG) is an innovative tool in temperate grasslands to benefit biodiversity, enhance soil nitrogen, and reduce invasive plants while maintaining cattle production at similar levels to traditional full burn management. Our objective was to determine how PBG affects provisioning and regulating ecosystem services in SHG, including forage production (Aboveground Net Primary Productivity, ANPP), plant diversity, and greenhouse gas regulation. Here we present results on provisioning services and economic impact.
A randomized block experiment was established in 2017 with 16 pastures (16 ha each) in two different pasture-types (intensively-managed (IM) vs. semi-natural (SN)) at Archbold’s Buck Island Ranch, FL, USA. Eight pastures were completely burned (“full-burn grazing”: FBG) and eight pastures were partially burned (“patch burn grazing”: PBG) under a fire regime of one-third burned annually (2017, 2018, 2019). Statistical comparisons are between PBG and FBG pastures, or within PBG comparing burned and unburned sectors. Economic analysis was based on average calf production in FL, forage productivity, stocking density, calf production, and recent calf $ values.
Results/Conclusions
In 2017, ANPP was greater in burned areas (in FBG and PBG) than unburned areas (F=4.64, p=0.006). In 2018, ANPP was greater in the PBG patches (both one year since fire and the recently burned patch) compared to the FBG that was one year since fire and the unburned patch in PBG (F = 4.78, p=0.005). Forage quality was greater in recently burned areas and declined with time since fire in both years. Cattle grazing intensity was greater in recently burned patches compared to unburned patches in PBG. In contrast, cattle grazing intensity was spread evenly across FBG pastures. Prescribed fire (in FBG and PBG) increased ANPP, was projected to increase cattle production by $485/ha in IM pastures and $33.79/ha in SN pastures. These benefits occur during the growing season, so ranchers still need to manage for winter forage. Preliminary analysis indicates that using PBG compared to FBG in SN pastures benefits cattle production by $19.40/ha. In contrast the same PBG to FBG comparison in IM pasture suggests a loss of -$46.94/ha: this was due to higher productivity overall in FBG compared to PBG in year 1 and outcomes will likely change with increased time since fire in FBG pastures.