Pre-print: "Post-fire Quercus alba fitness in a stressed plant community"

TPOS notes: This article is a pre-print and has not been peer reviewed.

Abstract

Prescribed burns are widely used for managing North American deciduous forests due to their ability to positively affect plant community structure and composition. This study examines the effects of neighboring herbaceous plants on the recruitment of Quercus alba (white oak) seedlings in fire-managed parts of Shawnee National Forest (Illinois, USA). Herbs were clipped to induce plant community stress and relative growth rates (RGRs) of planted white oak seedlings were assessed to determine if a competitive or facilitative dynamic is present. In addition to RGR, we observed the mycorrhizal network via fungal colonization in mesh bags to quantify belowground activity for our experimental plots. Our results supported fire's positive effects on tree recruitment and herbaceous growth. Clipping combined with fire management decreased RGR. This finding suggests that a facilitative dynamic is at play and herbaceous neighbors help white oak seedlings persist due to protection from environmental stressors (p = 0.017). Soil moisture played a large role in promoting tree fitness on each of our sites. Lower hyphal biomass was observed in areas where herbs were clipped. We further speculate that the stress caused by clipping may have suspended or eliminated the need for mycorrhizae to form, possibly due to herb mortality. Knowing how herbs and trees interact will lead to purposeful forest community planning especially in fire-managed forests where herbs are likely to dominate post-prescribed burn.

Citation:

"Post-fire Quercus alba fitness in a stressed plant community," Kevin Milla, bioRxiv 189829; doi: https://doi.org/10.1101/189829

Corresponding author: Kevin Milla, email: milla2 "at" illinois.edu

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

"Thermocouple Probe Orientation Affects Prescribed Fire Behavior Estimation"

Published December 14, 2017

Abstract:

Understanding the relationship between fire intensity and fuel mass is essential information for scientists and forest managers seeking to manage forests using prescribed fires. Peak burning temperature, duration of heating, and area under the temperature profile are fire behavior metrics obtained from thermocouple-datalogger assemblies used to characterize prescribed burns. Despite their recurrent usage in prescribed burn studies, there is no simple protocol established to guide the orientation of thermocouple installation. Our results from dormant and growing season burns in coastal longleaf pine (Pinus palustris Mill.) forests in South Carolina suggest that thermocouples located horizontally at the litter-soil interface record significantly higher estimates of peak burning temperature, duration of heating, and area under the temperature profile than thermocouples extending 28 cm vertically above the litter-soil interface (p < 0.01). Surprisingly, vertical and horizontal estimates of these measures did not show strong correlation with one another (r2 ≤ 0.14). The horizontal duration of heating values were greater in growing season burns than in dormant season burns (p < 0.01), but the vertical values did not indicate this difference (p = 0.52). Field measures of fuel mass and depth before and after fire showed promise as significant predictive variables (p ≤ 0.05) for the fire behavior metrics. However, all correlation coefficients were less than or equal to r2 = 0.41. Given these findings, we encourage scientists, researchers, and managers to carefully consider thermocouple orientation when investigating fire behavior metrics, as orientation may affect estimates of fire intensity and the distinction of fire treatment effects, particularly in forests with litter-dominated surface fuels.

Citation:

Coates, T. A., A. T. Chow, D. L. Hagan, T. A. Waldrop, G. G. Wang, W. C. Bridges, M. Rogers, and J. H. Dozier. 2017. Thermocouple Probe Orientation Affects Prescribed Fire Behavior Estimation. J. Environ. Qual. 0. doi:10.2134/jeq2017.02.0055

Corresponding author: Alex T. Chow (achow "at" clemson.edu)

Increased burn frequencies may be detrimental to soils & productivity in savanna grasslands

TPOS notes: A recent paper in the journal Nature made headlines for suggesting that an increase in the frequency of burning is detrimental to soils and plant productivity. The meta-analysis titled, "Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity" (available online Dec. 11), analyzed soils data from 48 long-term research sites from around the globe, representing savanna grasslands, broadleaf forests, needleleaf forests, and boreal forests.

The study primarily reports the comparison of sites with elevated fire frequencies (average fire frequency 4 times greater than the historic fire frequency) compared to sites protected from fire. Analysis of intermediate sites (at which fire frequencies were closer to mimicking the historic fire frequency) suggests that the changes associated with elevated burn frequencies were "... attributable both to C and N accumulation during fire protection, and to C and N loss during increased burning."

Media coverage included, "More frequent fires reduce soil carbon and fertility, slowing the regrowth of plants" at phys.org.

Abstract:

Fire frequency is changing globally and is projected to affect the global carbon cycle and climate. However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity. Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the frequency of fires was altered at each site. We find that frequently burned plots experienced a decline in surface soil carbon and nitrogen that was non-saturating through time, having 36 per cent (±13 per cent) less carbon and 38 per cent (±16 per cent) less nitrogen after 64 years than plots that were protected from fire. Fire-driven carbon and nitrogen losses were substantial in savanna grasslands and broadleaf forests, but not in temperate and boreal needleleaf forests. We also observe comparable soil carbon and nitrogen losses in an independent field dataset and in dynamic model simulations of global vegetation. The model study predicts that the long-term losses of soil nitrogen that result from more frequent burning may in turn decrease the carbon that is sequestered by net primary productivity by about 20 per cent of the total carbon that is emitted from burning biomass over the same period. Furthermore, we estimate that the effects of changes in fire frequency on ecosystem carbon storage may be 30 per cent too low if they do not include multidecadal changes in soil carbon, especially in drier savanna grasslands. Future changes in fire frequency may shift ecosystem carbon storage by changing soil carbon pools and nitrogen limitations on plant growth, altering the carbon sink capacity of frequently burning savanna grasslands and broadleaf forests.

Citation:

Pellegrini, A. F., Ahlström, A., Hobbie, S. E., Reich, P. B., Nieradzik, L. P., Staver, A. C., ... & Jackson, R. B. (2017). Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity. Nature.

doi:10.1038/nature24668

Corresponding author: Adam F. A. Pellegrini (afapelle "at" stanford.edu)

"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

“What is an anomaly?”*

TPOS note:

New research on the 2016 drought in the southern Appalachians demonstrates this event was an anomaly given recent regional climate trends. Since the 1950s, average fall weather has seen higher than average precipitation and lower than average daily high temperatures. The drought of 2016 (sometimes called a "flash drought") was notable for the "...intensity and rapid onset... and its destructive impact on wildfire and human water resources..."

However, the authors also reviewed longer-term climate data and concluded, "...droughts as strong as the 2016 event are more likely than indicated from a shorter 60 year perspective."

The infamous Chimney Tops 2 Fire occured during this flash drought. Following ignition by an arsonist, this fire burned from Great Smokey Mountains National Park to Gatlinburg, Tennessee. With severe drought, strong winds, steep terrain, and high fuel loads (including recent leaf fall and dry heavy fuels) the fire covered 14,000 acres, destroyed structures, and resulted in 14 fatalities.

Here are two questions we hope will lead to further discussion on this blog or elsewhere:

• do these events suggest wildfire risk assessments for the Midwest should be reviewed to determine if models include parameters adequate to modeling wildfire spread in worst case (so-called "unthinkable") scenarios?
• what questions do you have for the authors about this research?

Read the abstract below or check out the article "The 2016 southeastern U.S.drought: An extreme departure from centennial wetting and cooling" at http://onlinelibrary.wiley.com/doi/10.1002/2017JD027523/full

* thanks to Megan Sebasky, Northeast Region LANDFIRE coordinator, for helpful comments on this post and suggesting this title (read LANDFIRE's interview with Megan). Thanks also to Jed Meunier, Wisconsin DNR fire ecologist, for reviewing and sharing comments on this post.

Abstract

The fall 2016 drought in the southeastern United States (SE U.S.) appeared exceptional based on its widespread impacts, but the current monitoring framework that only extends from 1979 to present does not readily facilitate evaluation of soil-moisture anomalies in a centennial context. A new method to extend monthly gridded soil-moisture estimates back to 1895 is developed, indicating that since 1895, October–November 2016 soil moisture (0–200 cm) in the SE U.S. was likely the second lowest on record, behind 1954. This severe drought developed rapidly and was brought on by low September–November precipitation and record-high September–November daily maximum temperatures (Tmax). Record-high Tmax drove record-high atmospheric moisture demand, accounting for 28% of the October–November 2016 soil-moisture anomaly. Drought and heat in fall 2016 contrasted with 20th century wetting and cooling in the region but resembled conditions more common from 1895–1956. Dynamically, the exceptional drying in fall 2016 was driven by anomalous ridging over the central United States that reduced south-southwesterly moisture transports into the SE U.S. by approximately 75%. These circulation anomalies were partly promoted by a moderate La Niña and warmth in the tropical Atlantic, but these processes accounted for very little of the SE U.S. drying in fall 2016, implying a large role for internal atmospheric variability. The extended analysis back to 1895 indicates that SE U.S. droughts as strong as the 2016 event are more likely than indicated from a shorter 60 year perspective and continued multidecadal swings in precipitation may combine with future warming to further enhance the likelihood of such events.

Citation

Park Williams, A., Cook, B. I., Smerdon, J. E., Bishop, D. A., Seager, R., & Mankin, J. S. (2017). The 2016 southeastern U.S.drought: An extreme departure from centennial wetting and cooling. Journal of Geophysical Research: Atmospheres, 122. https://doi.org/10.1002/2017JD027523

Corresponding author: A. Park Williams, williams "at" ldeo.columbia.edu

Rapidly sharing new fire science for the TPOS region

Introducing a new tool to stay up-to-date on fire science for the tallgrass prairie and oak savanna region as it comes out. The New Science Blog is an experimental effort to increase the rate at which relevant science is shared with practitioners and researchers in the Upper Midwest.

There are multiple options to follow the blog:

• subscribe via RSS - http://www.tposfirescience.org/new-science/rss.xml,
• follow the new Twitter feed set up to share new posts (@strictlyfiresci), or
• watch for research round ups in the TPOS newsletter (join here).

How we find new publications:

Google Scholar and Web of Science alerts notify us when new fire science publications have been published for the tallgrass prairie and oak savanna ecosystems; for example, Google Scholar alerts notify us of papers that include both the phrase "tallgrass prairie" and "fire." However, this is a relatively poor filter -- many of the publications are not necessarily relevant to the region (for instance, a paper may be picked up because of a reference to tallgrass prairie in a literature review or the title of a paper in the works cited section). Papers shared via the blog are selected for their potential relevance to fire practitioners, land managers, ecologists, researchers, and policy makers in the region.

Your feedback about whether we were too narrow or too broad with our first selections will help us modify how we determine which papers to share.

The audiences:

Applied science is favored by practitioners, so expect to see an emphasis on papers that compare restoration and management techniques that incorporate prescribed fire (for example, research published in Restoration Ecology, Ecological Restoration, Fire Ecology, Conservation Biology, Ecosphere). Studies of fire effects on taxa and other natural history papers also provide valuable information to land stewards and wildlife biologists (journals such as American Midland Naturalist, Natural Areas Journal, Biodiversity Conservation).

We will also share papers that provide examples of fire ecology research methods that can be applied to management challenges in the TPOS region-even if the study was not conducted here. Those posts will be tagged "research methods."

While we are sometimes encouraged to avoid "preaching to the choir," some of our members have interest in papers that share interesting perspectives on fire ecology, wildfire, and prescribed fire, whether or not the information can be directly applied. We'll aim for 5-10 percent of posts sharing new peer-reviewed papers that address national policy, controversial issues that affect public opinion about prescribed fire, and fire science that is otherwise nationally or internationally notable.

"Developing a Conceptual Framework of Landscape and Hydrology on Tallgrass Prairie: A Critical Zone Approach"

TPOS note:

New interdisciplinary research published in the Vadose Zone Journal integrates ecology, climate, hydrology, and soils at Konza Prairie, a reference site for the tallgrass prairie ecosystem. While this paper may lack immediate applications, it provides a long view on grassland management.

Check out the abstract below or follow this link to the article (this article is not open access): https://dl.sciencesocieties.org/publications/vzj/abstracts/0/0/vzj2017.03.0069

Core Ideas: 

• Konza Prairie is a reference ecosystem for evaluation of current and former grasslands.
• Hydrologic change includes climatic and geologic factors such as karstification.
• Future research is needed to expand vadose zone knowledge.

Abstract

Agricultural intensification and urbanization have greatly reduced the extent of tallgrass prairie across North America. To evaluate the impact of these changes, a reference ecosystem of unperturbed prairie is required. The Konza Prairie Biological Station in northeastern Kansas is a long-term research site at which a critical zone approach has been implemented. Integration of climatic, ecologic, and hydropedologic research to facilitate a comprehensive understanding of the complex environment provides the basis for predicting future aquifer and landscape evolution. We present a conceptual framework of the hydrology underpinning the area that integrates the extensive current and past research and provides a synthesis of the literature to date. The key factors in the hydrologic behavior of Konza Prairie are climate, ecology, vadose zone characteristics and management, and groundwater and bedrock. Significant interactions among these factors include bedrock dissolution driven by cool-season precipitation and hence a climatic control on the rate of karstification. Soil moisture dynamics are influenced at various timescales due to the short- and long-term effects of prescribed burning on vegetation and on soil physical characteristics. The frequency of burning regimes strongly influences the expansion of woody species in competition with native tallgrasses, with consequent effects on C and N dynamics within the vadose zone. Knowledge gaps exist pertaining to the future of Konza Prairie (a model for US tallgrass prairie)—whether continued karstification will lead to increasingly flashy and dynamic hydrology and whether compositional changes in the vegetation will affect long-term changes in water balances.

Citation:

Vero, S.E., G.L. Macpherson, P.L. Sullivan, A.E. Brookfield, J.B. Nippert, M.F. Kirk, S. Datta, and P. Kempton. 2017. Developing a Conceptual Framework of Landscape and Hydrology on Tallgrass Prairie: A Critical Zone Approach. Vadose Zone J. 0. doi:10.2136/vzj2017.03.0069