Burning and climate interactions determine impacts of grazing on tallgrass prairie systems

Authors: FLYNN, COLTON - Redlands Community College; ZHOU, YUTING - Oklahoma State University; Gowda, Prasanna; Moffet, Corey; Wagle, Pradeep; KAKANI, VIJAYA - Oklahoma State University

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2019
Publication Date: 11/6/2019
Citation: Flynn, C.K., Zhou, Y., Gowda, P.H., Moffet, C., Wagle, P., Kakani, V.G. 2019. Burning and climate interactions determine impacts of grazing on tallgrass prairie systems. Rangeland Ecology and Management. 73(1):104-118. https://doi.org/10.1016/j.rama.2019.10.002.
DOI: https://doi.org/10.1016/j.rama.2019.10.002

Interpretive Summary: This six-year study (2011-2016) compared tallgrass prairie pastures that were subjected to burned and unburned conditions while exposed to grazing under differing climate conditions in the Southern Great Plains of the United States. The study sites consisted of six pastures, three burned and three unburned. Each burned pasture was further divided into three patches and subjected to a three-year rotational burning cycle. The Enhanced Vegetation Index (EVI) derived from satellite images was used to indicate vegetation production. The distribution of precipitation controlled vegetation phenology during and after grazing. Most burned patches had lesser production than unburned patches within the same pasture, probably because of selective grazing of newly grown grass in recently burned patches. The differences in production were larger (13%) in a drought year (2011) compared to normal (3% in 2013) and wet (<1% in 2015) years. In contrast, the differences in production between during and after grazing periods were mostly (78%) smaller in burned than unburned patches. More variations in production existed among pasture comparisons due to landscape heterogeneity. Overall, results demonstrated that pyric herbivory management and climate determine the impacts of grazing on tallgrass prairie systems. The contrasting seasonal forage availabilities in burned and unburned patches suggests that patch burning might better balance the quantity and quality of the grass available for cattle grazing.

Technical Abstract: Tallgrass prairie may respond differently to prescribed burning and subsequent preferential grazing, termed pyric herbivory, under variable climate conditions. This six-year study (2011-2016) compared tallgrass prairie pastures that were subjected to burned and unburned conditions while exposed to grazing under differing climate conditions in the Southern Great Plains of the United States. The study area consisted of six pastures, three burned and three unburned. Each burned pasture was further divided into three patches and subjected to a three-year rotational burning cycle. The Enhanced Vegetation Index (EVI) derived from Landsat 7/8 (EVILS) and Moderate Resolution Imaging Sprectroradiometer (MODIS, EVIMOD) was used to indicate vegetation production depending on size of pastures. Based on EVILS, most burned patches (11 of 18) had lesser production (overall difference of 3%) than unburned patches within the same pasture. The differences were larger (13%) in a drought year (2011) compared to normal (3% in 2013) and wet (<1% in 2015) years. The distribution of precipitation controlled EVILS for periods during and after grazing. The burned patches tended to have lower EVILS during grazing periods than the unburned patches within the same pasture, probably because of selective grazing of newly grown grass in recently burned patches. In contrast, the differences in EVILS between during and after grazing periods were mostly (78%) smaller in burned than unburned patches. However, more variations in EVILS existed among pasture comparisons due to landscape heterogeneity. Similar results were observed with EVIMOD. Overall, results demonstrated that pyric herbivory management and climate determine the impacts of grazing on tallgrass prairie systems. The contrasting seasonal forage availabilities in burned and unburned patches, indicated by different seasonality of EVI, also suggests that patch burning might better balance the quantity and quality of the grass available for cattle grazing.