Spatially discrete disturbance processes enhance grassland floral resources

Abstract

resources and may delay flower availability. Similarly, grazing removes competitors of flowering plants, but destroys flower heads.2. To address this knowledge gap, we investigated the impacts of rotational fire and cattle grazing (patch-burn grazing with one and two seasons of fire per year) versus traditional season-long grazing with no fire on floral resources in mixed-grass prairie. In patch-burn treatments, part of each pasture is burned each year, which focuses grazing activity due to the high-quality regrowth. We aimed to use fire to remove litter around flowering plants while also sheltering established flower heads from grazing pressure by directing cattle away from regenerating forbs in unburned portions of the landscape. Over two summers, we performed weekly flower surveys in season-long grazing and patch-burn grazing pastures. We analysed total seasonal floral resources, maximum floral abundance and seasonal species richness between treatments.3. Over 2 years, we surveyed 1,238,241 ramets of 160 species, focusing on 36 common species for individual analysis. We found broad positive associations between patch-burn grazing and total seasonal flower abundance, maximum flower abundance and species richness compared to traditional management.In most cases, patch-burn grazing with dormant and growing season fires produced higher floral abundance, total seasonal floral resources and species richness than patch-burning with dormant season fires alone, suggesting benefits of increased levels of pyrodiversity.

Native and introduced pollinators vary in their seasonal floral resource visitation and selection between native and exotic plant species

“…Aside from restorative plantings to increase native species forage, grassland managers can promote native floral expression through grassland management practices. For example, localized prescribed fire and grazing disturbances in grasslands can reduce competitive litter and increase floral expression (Duquette et al, 2022). Artificially implementing disturbances in the NGP region is especially important due to the prevalence of idle management that favours low‐diversity plant communities and differs greatly from grassland disturbance processes historically maintained by native herbivores and wildfires (Fuhlendorf & Engle, 2001; Murphy & Grant, 2005).…”

Pyrogeography of the Western Great Plains: A 40-Year History of Fire in Semi-Arid Rangelands

“…Surveys of remotely-sensed vegetation data from across the Great Plains and western rangelands suggest that prairie communities are resilient to wildfire [78,79], and field data from the Northern Plains, specifically, call into question the necessity of grazing exclusion [80][81][82]. In fact, research on prescribed fire suggests recently-burned vegetation provides higher-quality forage, supports better livestock weight gains, and enhances pollinator resources without negative impacts on soil carbon and microbes, generally increasing ecosystem service delivery and buffering against drought [83][84][85][86][87][88]. However, it remains to be determined whether these same positive outcomes for livestock production can be realized from wildfires.…”

Heterogeneity-Based Management Restores Diversity and Alters Vegetation Structure without Decreasing Invasive Grasses in Working Mixed-Grass Prairie

“…), and Pascopyrum smithii (Rydb. ), but now Poa pratensis and Bromus inermis comprise the majority of vegetation cover [32,33]. Common forbs include Solidago spp., Asclepias spp., and Cirsium spp., while Symphoricarpos occidentalis (Hook.)…”

“…Common forbs include Solidago spp., Asclepias spp., and Cirsium spp., while Symphoricarpos occidentalis (Hook.) is the dominant woody species [33]. Common non-native forb species include Artemisia absinthium (L.), Melilotus officinalis (L.), and Medicago sativa (L.).…”