Patch-burn grazing impacts forage resources in subtropical humid grazing lands

Authors: BOUGHTON, ELIZABETH - Archbold Biological Station; GOMEZ-CASANOVAS, NURIA - University Of Illinois; SWAIN, HILARY - Archbold Biological Station; Bernacchi, Carl; BOUGHTON, RAOUL - Archbold Biological Station; BRINSKO, KEITH - Archbold Biological Station; LI, HAOYU - Archbold Biological Station; RIVERO, ALAN - Archbold Biological Station; DELUCIA, EVAN - University Of Illinois; SPARKS, JED - Cornell University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2022
Publication Date: 6/10/2022
Citation: Boughton, E., Gomez-Casanovas, N., Swain, H., Bernacchi, C.J., Boughton, R.K., Brinsko, K., Li, H., Rivero, A., DeLucia, E.H., Sparks, J. 2022. Patch-burn grazing impacts forage resources in subtropical humid grazing lands. Rangeland Ecology and Management. 84:10-21. https://doi.org/10.1016/j.rama.2022.05.004.
DOI: https://doi.org/10.1016/j.rama.2022.05.004

Interpretive Summary: Globally grasslands represent a major land use and have many services that they provide to the environment and to agriculture. The extent that the grassland services can be optimized depends heavily on how they are managed. Research in this area, particularly for subtropical grasslands, is limited regarding the potential for fire management on optimizing the services that grasslands provide. Two burning regimes are compared in this study, one in which large grasslands are burned once at the start of the three-year experiment. The second treatment are one-third of each grassland is burned each year, with each third only being burned one. Many aspects of grassland growth, productivity, and nutritive quality were assessed throughout the experiment. Two types of grasslands were tested in these treatments, with half being agronomically improved pastures and the other half being pastures that are close to unimproved native grasslands. We found that the grasslands burned incrementally over three years showed contrast in the nutritional quality in each 'patch'. Results also showed that the patch burned grasslands had overall higher nutritive value. These results were consistent with both the improved and semi-native grasslands. The patch burning improved digestible forage production only in the semi-native pastures. These results suggest that fire management in grazed subtropic grasslands may be a strategy that impacts cattle production, species diversity, and ecosystem function.

Technical Abstract: Subtropical humid grazinglands represent a large global land use and are important for livestock production as well as provision of multiple ecosystem services. However, more work is needed to assess how innovative management regimes alter sustainability of these systems. Patch-burn grazing (PBG) management is commonly applied in temperate grazinglands to enhance environmental and economic sustainability, however this management system has not been widely tested in subtropical humid grazinglands. The objective of this study was to determine how PBG affected forage resources, including aboveground net primary productivity (ANPP), digestible forage production, residual biomass, growth rate, and forage nutritive value (Total P, crude protein, and in vitro organic matter digestibility (IVOMD)) in comparison to the business-as-usual full burn management in both intensively managed pastures and semi-native pastures in the subtropical humid region of south-central Florida. We hypothesized that PBG management would create patch contrasts in forage quantity and forage nutritive value in both improved and semi-native pastures, with a greater effect in semi-native pastures. A randomized block design experiment was established in 2017 with 16 pastures (16 ha each) in two different pasture-types (intensively-managed (IMP) vs. semi-natural (SN)) at Archbold Biological Station’s Buck Island Ranch in FL, USA. In 2017, eight pastures were completely burned (“full-burned”: FB). The remaining eight pastures were partially burned (“patch burn grazing”: PBG) under a fire regime of one-third burned yearly with the first third burned in 2017. We found: 1) Patch-burn grazing management employed on intensively managed and semi-native subtropical humid pastures resulted in the creation of patch contrast in forage nutritive value (total P, crude protein, and IVOMD), ANPP, digestible forage production, and residual biomass, 2) PBG benefited forage nutritive value in both IMP and SN, and 3) PBG increased digestible forage production in semi-native pastures. The creation of heterogeneity with PBG may impact cattle production, species diversity, and ecosystem function and our work is underway to examine these responses in subtropical humid grasslands.