Variation in prescribed fire and bison grazing supports multiple bee nesting groups in tallgrass prairie

This article was published July 30, 2021 in Restoration Ecology.

Use this link to access the article's permanent address (DOI)

Abstract

Fire and grazing are historic ecosystem drivers of tallgrass prairie and both are used for restoration management today. The effects of these drivers on animal taxa are still incompletely resolved, especially for wild bees, a growing conservation and restoration priority. Fire and grazing could affect wild bee communities through structural changes to nest site availability via changes to soil conditions, vegetative cover, and availability of plant stems. Here, we sought to determine how different bee nesting groups are affected by the combination of fire and bison grazing management strategies. We grouped bee species by nesting substrate (ground, stem/hole, large cavity) because we expect the availability of these substrates to vary with the application of prescribed fire and grazing. We collected bees in restored and remnant high-quality tallgrass prairie and analyzed whether the proportion of each nesting group within the total bee community was predicted by fire and/or grazing. Ground-nesting bees reached their greatest proportion in bee communities immediately after prescribed fire, but declined proportionally over time since the last burn. Stem-/hole-nesting bees reached their highest proportion in the bee community with infrequent fire (6-year interval) and differed in their response to fire depending on the presence/absence of bison. Sampling year affected bee nesting groups and we found that nesting groups did not change in concert (i.e. different nesting groups had different good and bad years from each other). Our results show that spatiotemporal variation of prescribed fire and bison grazing is essential for conservation of multiple bee nesting groups.

Citation

Bruninga‐Socolar, Bethanne, Sean R. Griffin, Zachary M. Portman, and Jason Gibbs. "Variation in prescribed fire and bison grazing supports multiple bee nesting groups in tallgrass prairie." Restoration Ecology (2021): e13507.

Fires slow population declines of a long-lived prairie plant through multiple vital rates

This article was published June 2, 2021 in Oecologia.

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Abstract

In grasslands worldwide, modified fire cycles are accelerating herbaceous species extinctions. Fire may avert population declines by increasing survival, reproduction, or both. Survival and growth after fires may be promoted by removal of competitors or biomass and increasing resource availability. Fire-stimulated reproduction may also contribute to population growth through bolstered recruitment. We quantified these influences of fire on population dynamics in Echinacea angustifolia, a perennial forb in North American tallgrass prairie. We first used four datasets, 7–21 years long, to estimate fire’s influences on survival, flowering, and recruitment. We then used matrix projection models to estimate growth rates across several burn frequencies in five populations, each with one to four burns over 15 years. Finally, we estimated the contribution of fire-induced changes in each vital rate to changes in population growth. Population growth rates generally increased with burning. The demographic process underpinning these increases depended on juvenile survival. In populations with high juvenile survival, fire-induced increases in seedling recruitment and juvenile survival enhanced population growth. However, in populations with low juvenile survival, small changes in adult survival drove growth rate changes. Regardless of burn frequencies, our models suggest populations are declining and that recruitment and juvenile survival critically influence population response to fire. However, crucially, increased seedling recruitment only increases population growth rates when enough new recruits reach reproductive maturity. The importance of recruitment and juvenile survival is especially relevant for small populations in fragmented habitats subject to mate-limiting Allee effects and inbreeding depression, which reduce recruitment and survival, respectively.

Citation

Nordstrom, Scott W., Amy B. Dykstra, and Stuart Wagenius. "Fires slow population declines of a long-lived prairie plant through multiple vital rates." Oecologia (2021): 1-13.

Exploring the Potential Role of Ants as Pollinators in a Tallgrass Prairie Following Varied Prescribed Burns

This article was published Nov. 10, 2021, in Transactions of the Kansas Academy of Sciences 

https://doi.org/10.1660/062.124.0301

Abstract

Prescribed burns are used to restore the herbaceous plant communities of tallgrass prairies. Unfortunately, land-use change has driven declines in animal communities that use that habitat, including insect pollinators. Flowering forbs in tallgrass prairies likely depend on insect pollinators for their reproduction, suggesting that restoration efforts may be limited if insect pollinators continue to decline. Further, prescribed burns may lead to the direct mortality of insect pollinators. We thus explore whether Formica ants may be able to compensate for the loss of insect pollinators in tallgrass prairies by monitoring visitation rates of ants and insect pollinators to the milkweed Asclepias tuberosa. Using replicated experimental plots burned at different times (summer, fall, or spring), we found that ants were robust to the timing of prescribed burns and that they averaged 50% of all visits across plots. The distribution of ants and other insect pollinators may be regulated by competitive interactions, as there was a negative relationship between the two potential pollinator communities: the more ant visits, the fewer pollinator visits, and vice versa. The high visitation rates suggest ants may potentially compensate, especially as competitive interactions decrease, but whether that may occur likely depends on their efficiency as pollinators, current plant features, or subsequent plant adaptations to utilize ants.

Citation

Eckols, Tucker, Bethany Roberton, Brandon Clark, and Darren Rebar. "Exploring the Potential Role of Ants as Pollinators in a Tallgrass Prairie Following Varied Prescribed Burns." Transactions of the Kansas Academy of Science 124, no. 3-4: 155-164.

New Paper on Effects of Fire, Habitat and Climate on Regal Fritillary

TPOS notes:

In "Disentangling effects of fire, habitat, and climate on an endangered prairie-specialist butterfly," the authors present an analysis of long-term datasets on populations of an endangered species, habitat quality, and prescribed fire management.

Available online Dec. 20, 2017 via https://www.sciencedirect.com/science/article/pii/S0006320717312211.

Abstract:

Tallgrass prairie, arguably the most fire-dependent system in North America, is a Biome that has been essentially eliminated and is now exceedingly rare. Absent frequent disturbance, remnant tallgrass prairie rapidly converts to a dominant cover of woody plants. This creates unique challenges for conservation of prairie-specialist insects dependent on increasingly small and isolated habitats prone to direct and indirect threats from climate variability, habitat degradation, and management activities; or lack thereof. Regal fritillary butterflies (Speyeria idalia) exemplify this problem, with sharp population declines in recent decades and considerable disagreement on management practices, particularly in the use of prescribed burning to maintain habitat. Spanning 20-years (1997–2016), we evaluated regal fritillary populations within seven sites in relation to fire, habitat, and climate records to better understand these interacting effects on interannual and long-term population changes. Though fire had short-term negative effects on regal fritillary abundance, habitat quality was one of the most important factors explaining populations and was positively associated with prescribed fire. Burning every 3–5 years maximized regal fritillary abundance, but even annual burning was more beneficial to regal populations than no burning at all. Unburned refugia are important in maintaining populations, but creating and maintaining high quality habitat with abundant violets (Viola spp) and varied nectar sources, may be the most impactful management and conservation tool. Regal fritillary butterflies were consistently more than twice as abundant on high quality habitats and this relationship held across, and often dwarfed the effects of, various prescribed fire regimes or climate variability.

Keywords

Grasslands; Habitat quality; Pollinators; Prairie; Prescribed fire; Regal fritillary

Citation:

Richard A. Henderson, Jed Meunier, Nathan S. Holoubek, Disentangling effects of fire, habitat, and climate on an endangered prairie-specialist butterfly, Biological Conservation, Volume 218, February 2018, Pages 41-48, ISSN 0006-3207, https://doi.org/10.1016/j.biocon.2017.10.034.

Corresponding author: Richard A. Henderson, tpe.rhenderson "at" tds.net

"Landscape context drives breeding habitat selection by an enigmatic grassland songbird"

TPOS notes:

This study of habitat use by the rare Henslow's sparrow in eastern Kansas sampled grassland sites in the fragmented agricultural landscape ("Western Corn Belt Plains" ecoregion) as well as the extensive remnant grasslands of the Flint Hills. The species avoided woody vegetation and cropland, preferring landscapes with a higher proportion of grassland; for example, individuals were more likely to be detected in smalll patches of CRP embedded in rangeland than small patches of CRP surrounded by agricultural land. However, even in the Flint Hills the sparrows occupied less than 4% of the grassland area preferring CRP to intensively managed rangeland (typically grazed or burned then grazed). By using multiple sampling periods, researchers found that the sparrows were highly mobile within any given year, and in some cases occupied sites after mid-June that had been burned earlier in the year, though none were detected at completely burned sites during early season sampling.

First online 10/5/17 in Landscape Ecology.

Authors

Mark R. Herse, Michael E. Estey, Pamela J. Moore, Brett K. Sandercock, W. Alice Boyle

Abstract

Purpose

Wildlife conservation requires understanding how landscape context influences habitat selection at spatial scales broader than the territory or habitat patch.

Objectives

We assessed how landscape composition, fragmentation, and disturbance affected occurrence and within-season site-fidelity of a declining grassland songbird species (Henslow’s Sparrow, Ammodramus henslowii).

Methods

Our study area encompassed eastern Kansas (USA) and North America’s largest remaining tracts of tallgrass prairie. We conducted 10,292 breeding-season point-count surveys over 2 years, and related occurrence and within-season site-occupancy dynamics of sparrows to landscape attributes within 400-, 800-, and 1600-m radii.

Results

Sparrows inhabited < 1% of sites, appearing and disappearing locally within and between breeding seasons. Early in spring, sparrows responded to landscape attributes most strongly within 400-m radii, settling in areas containing > 50% unburned prairie. Later in summer, sparrows responded to landscape attributes most strongly within 800-m radii, settling in areas containing > 50% unfragmented prairie, including sites burned earlier the same year. Sparrows avoided landscapes containing woody vegetation, disappeared from hayfields after mowing, and were most likely to inhabit landscapes containing Conservation Reserve Program (CRP) fields embedded within rangeland.

Conclusions

Landscape context influenced habitat selection at spatial scales broader than both the territory and habitat patch. Protecting contiguous prairies from agricultural conversion and woody encroachment, promoting CRP enrollment, and maintaining portions of undisturbed prairie in working rangelands each year are critical to reversing the conservation crisis in North America’s remaining grasslands. As landscape change alters natural areas worldwide, effective conservation requires suitable conditions for threatened species at multiple spatial scales.

Link to article: http://rdcu.be/x2OX

Citation

Herse, M.R., Estey, M.E., Moore, P.J. et al. Landscape Ecol (2017). https://doi.org/10.1007/s10980-017-0574-z