Impact of Patch‐Burn Grazing on Vegetation Composition and Structure in Subtropical Humid Grasslands

Abstract

Pyric herbivory, a process by which grazing is driven by fire, has been shown to create heterogeneity in fire-prone grasslands. Patch-burn grazing (PBG) is a management tool used to harness pyric herbivory and contrasts with full burn (FB) which fosters homogeneity. Here we provide a comprehensive assessment of plant communities (vegetation composition, diversity, and heterogeneity), soil characteristics, and fire fuel consumption responses to PBG as compared to FB management in two different pasture-types (intensively managed pastures [IMP] vs. less intensely managed seminatural pastures [SNP]) in subtropical, humid grasslands in Florida, USA. In 2017, we established 16 experimental pastures at Archbold Biological Station's Buck Island Ranch that were 16-ha each, eight in IMP and eight in SNP. Of the eight pastures in each pasture-type, four were fully burned in 2017 (FB) while in the other four, one-third of the pasture was burned each year for three years (2017, 2018, and 2019) (PBG). PBG-treated pastures were expected to have greater plant richness, diversity, and structural heterogeneity due to the creation of patch contrast while in FB pastures, we expected homogeneous vegetation structure because patches would all have the same fire history. Fuel consumption by fire was greater in SNP vs. IMP and in burned patches within PBG vs. similar-size areas in FB. Recently burned patches had greater total native richness and Shannon diversity, driven by greater numbers and cover of forbs and sedges, but the magnitude of this response varied among years. PBG pastures had greater structural heterogeneity shortly after fire but this disappeared by the end of the growing season. PBG benefits both conservation and production goals in SNP, but incentive programs may be required to implement PBG in IMP to offset losses in forage production while gaining increased height heterogeneity and potential increases in vegetation diversity.