How does fire affect ant-mediated seed dispersal?

Eva Colberg describes her ongoing research at Shaw Nature Reserve. She is a Ph.D. student in the Biology Department at the University of Missouri St. Louis.

In the late 1940s, Ohio-born entomologist Mary Talbot spent her days crouched in the woods of St. Charles, MO, tracking ant activity in painstaking detail through the seasons. Similarly, last summer I tried my hand at watching ants in the woodlands of Shaw Nature Reserve, with the addition of crumbled pecan shortbread cookies and the help of my field assistant, Dayane Reis. Foraging ants flocked to the buttery feast, the contrast of the crumbs’ sandy color against dark soil and leaf litter allowing us to easily follow the cookie thieves back to their nests.

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A plot of flagged ant nests (found by following cookie-bearing ants) in the Dana Brown Woods, one of the management units at Shaw Nature Reserve.

We watched at least seven different species of ants run off with the cookie crumbs, but I was most interested in the winnow ant (Aphaenogaster rudis). Reddish-brown, long-legged, and narrow-waisted due to a double-segmented petiole (the connection between the abdomen and thorax), the winnow ant worker is an elegant lady. She is also remarkably swift-footed and strong, adept at carrying chunks of pecan cookie or naturally occurring analogs.

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A winnow ant (Aphaenogaster rudis) worker, with the petiole and post-petiole that give the species its svelte waist. From her head to the end of her abdomen, this ant is about 4.5 mm long.

To an ant, a cookie more or less resembles an insect carcass, a staple of many ant diets. Chemically and nutritionally, the seeds of many of Missouri’s spring-flowering herbs also resemble a delicious dead insect (or cookie). From an ant’s point of view, this means food for larvae. From a seed’s point of view, this means dispersal. Hitchhiking to an ant’s nest gives the seed a new location to germinate and grow away from the parent plant, and potentially a multitude of other benefits such as escape from predation or better soil conditions. In any case, this is ant-mediated seed dispersal, or myrmecochory.

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A field ant (Formica subsericea) grabs a bloodroot (Sanguinaria canadensis) seed by its elaiosome, the oily, nutritious appendage that most resembles a dead insect and attracts ants.

In other parts of the world, benefits of myrmecochory include enhanced survival and germination after fire. In arid, fire-prone areas of both Australia and South Africa, ants bury seeds deep enough to buffer the intense heat of fire, but shallow enough that the heat weakens the seed coat and increases the odds of germination. Thus, the ants protect the seed from the flames while still providing exposure to a Goldilocks level of heat.

Just as in Australia and South Africa, fire is (or was, and with the help of land managers is once again becoming) also a frequent occurrence in Missouri. At Shaw Nature Reserve, managers use prescribed burns to restore an open structure to the reserve’s oak-hickory woodlands. But, is ant-mediated seed dispersal interacting with fire the same way here as in those other fire-adapted ecosystems?

This is a key question of my dissertation research at University of Missouri St. Louis. Using cookies to find winnow ant nests last summer helped me test methods and plan out my experiments for this coming year. Specifically, I will be tracking where the ants take their seeds, whether ants disperse seeds more or less in the year after a fire, and whether the presence and timing of surface fire affects the germination of the seeds after dispersal. Stay tuned!

You can keep up with Eva Colberg on Twitter (@ColbergEva) or by checking out her science communication initiative Science Distilled STL.

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It’s Complicated: Trees and Ecological Restoration

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The best time to plant a tree was twenty years ago. The second best time is now.
-Anonymous

Addendum: That is, unless the tree will grow just fine without your help or the tree doesn’t really belong there. In that case, the best time might be never.

Planting a tree is rejuvenating. It gets you outside, it’s good exercise, and it’s often good for the planet. Really, trees give us an awful lot and don’t ask for much in return. Among their many gifts are food, shade, animal habitat, building materials, erosion control, and fuel. Trees also filter our water and suck carbon out of the air. In cities, trees collect grit and grime that would otherwise coat our lungs.

But tree planting is not the same as restoration. Ecological restoration is the process of assisting the recovery of a damaged ecosystem. Trees are integral to many ecosystems, like forests…

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Notes on dolomite glade natural history and restoration

In early October, CCSD scientists Leighton Reid, Matthew Albrecht, and James Aronson and Shaw Nature Reserve naturalist James Trager toured several dolomite glades with Greg Mueller (Chicago Botanic Garden) and Betty Strack (Field Museum). We used the opportunity to discuss glade natural history and restoration.

In his book The Terrestrial Natural Communities of Missouri, Paul Nelson describes glades as:

“…open, rocky, barren areas dominated by drought-adapted forbs, warm-season grasses and a specialized fauna. They appear as small or large essentially treeless openings within landscapes primarily dominated by woodlands.”

Missouri glades are characterized by their geology. Many occur on southwestern-facing slopes with outcrops of sedimentary rocks, like dolomite and sandstone. But some also occur with igneous rocks in the St. Francis Mountains and Tom Sauk Mountain.

For some, glades seem like miniature deserts, complete with cacti, collared lizards, tarantulas, and even roadrunners in southwestern Missouri.

But glades are also like islands. To many of the organisms adapted to these sunny, rocky environments, the dark, duffy woodlands that surround them may seem like an oceanic barrier to movement. Dispersal events between glades can be rare. For collared lizards, dispersal is contingent on landscape fire to temporarily make the surrounding woodlands more easily traversable.

Glades are rarely cultivated, but many have been grazed. Cattle degrade glades by eroding and compacting their thin, precious soil. Some glades are also maintained by fire, which keeps woody trees and shrubs from crowding out the forbs and grasses. When people suppress fires, some glades become overrun with trees – especially eastern redcedar (Juniperus virginiana).

Shaw Nature Reserve contains a kind of chronosequence of glade restorations. Near the Maritz Trail House, Crescent and Long Glades were restored in the 1990s by clearing out the encroaching redcedar, establishing a fire regime, and reintroducing forbs and grasses – some of which were sourced from the remnant prairie at Calvary Cemetery in St. Louis. Other glades at Shaw Nature Reserve were restored in the 2000s and 2010s using similar techniques. So it might be possible to study changes in restored glades over time by comparing older restored glades to younger ones.

Could better-conserved dolomite glades serve as a reference to guide restoration at Shaw Nature Reserve? Beautiful dolomite glades are conserved at Valley View Glades Natural Area, Victoria Glades Conservation Area, and Meramec State Park. Some of these have plant species that are missing from Shaw Nature Reserve, possibly because they once existed at Shaw Nature Reserve and were extirpated, or possibly because glades at Shaw Nature Reserve lack appropriate ecological conditions for these plants. For example, prior grazing may have stripped the soil of some vital mycorrhizal fungi. Either way, the lack of some rare plants at Shaw Nature Reserve is probably exacerbated by fragmentation – a remnant plant population at Valley View Glades Natural Area would probably have trouble dispersing seeds 28 kilometers (17 miles) to Shaw Nature Reserve.

Further reading

Nelson P. (2010) Terrestrial Natural Communities of Missouri. 550 pages.

CrescentGladeSoilLine

Lines of woody vegetation on dolomite glades correspond to the local stratigraphy; plants like gum bumelia (Sideroxylon lanuginosum) and eastern redbud (Cercis canadensis) accrue on slightly deeper-than-average soils. (Crescent Glade, Shaw Nature Reserve)

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In this regularly burned glade at Shaw Nature Reserve, there is a fairly seamless transition between the open glade with abundant Rudbeckia and Silphium and the adjacent oak/hickory woodland. In other places, such glade/woodland transitions are marked by a dense thicket of vegetation, often with a strong component of eastern redbud or eastern redcedar. (Crescent Glade, Shaw Nature Reserve)

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Gattinger’s goldenrod (Solidago gattingeri) is an open-panicled goldenrod found on dolomite glades in the northern Ozarks and, disjunctly, in the cedar barrens of central Tennessee. This one was growing just above a transition from dolomite to sandstone substrate on Crescent Glade at Shaw Nature Reserve.

KatydidCrescentGlade

A short-winged meadow katydid (Conocephalus brevipennis) rests on a seed head of Missouri coneflower (Rudbeckia missouriensis). These black seed heads were abundant across Crescent Glade in early October.

BarnGlade

Barn glade has been restored much more recently. A line of green, resprouting brush (including invasive Lonicera maackii and Ailanthus altissima) is visible where woody vegetation was recently removed. Blue flags in the foreground mark an experimental population of endangered Pyne’s ground plum (Astragalus bibullatus).

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A denizen of barn glade – the lichen grasshopper. (Shaw Nature Reserve)

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The quality of Valley View Glades Natural Area is evident in the abundant and diverse fall wildflowers that were present in early October. Could regional dolomite glades like this one serve as references to guide glade restoration at Shaw Nature Reserve?

 

 

Microstegium population distribution (and control) along Brush Creek

Restoration specialist, Mike Saxton, describes his observations on the distribution of invasive Japanese stiltgrass along a creek running through Shaw Nature Reserve.

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Brush Creek (blue) runs eastward through Shaw Nature Reserve in Gray Summit, Missouri. Gray Summit Road is in the upper right.

July 28, 2017

Yesterday, Adam and I put in to Brush Creek at the Old Gray Summit Rd. bridge and headed upstream spraying Microstegium vimenium (Japanese stiltgrass). This was the second time through this area this year and I made this sweep solo 3 times last season. My first outing last season, I used 3 gallons of herbicide before I finished the first wetland cell…this year it’s been much, much lighter. Last year, with only 1 person spraying, I was hard pressed to leave the creek bed because there was so much to spray directly along the accessible banks. And in our first outing this season, Catherine and I stayed completely within in the creek, rarely going up on the banks.

However, yesterday Adam and I abandoned the creek bed and went crashing through the brushy banks, finding more Microstegium than I had anticipated. What was interesting was that pockets of stiltgrass followed a predictable pattern of distribution. In many areas, one creek bank will be severely down cut, perhaps 15 ft sheer banks, while the opposite bank is tapered with a more gradual slope. This is where you find the Microstegium. I posit that floodwaters do not over-top the high bank but rush over the lower bank depositing sediment and seed. Almost without fail, the lower bank, if totally brushy, would have scatted Microstegium. However, if the lower bank was open or had open pockets of sunlight, those pockets would be dense thickets of stiltgrass. We observed a nearly 1-to-1 correlation between bank height and stiltgrass presence/absence and open sunlit patches having dense patches of stiltgrass on the lower banks.

I was covering a roughly 20 ft swath out from the bank edge before it dropped into the creek bed.  I did go further from the creek a number of times but wasn’t finding much (if any) the further I got from the creek.

Management considerations

Based on these observations, I believe that our current strategy of managing downstream from the “head waters” is prudent. Based on the diminished population this year and because the species has a 5-year seed viability, we should continue to see diminishing populations if we continue to be methodical and thorough with our management.

We repeatedly found dense patches of Microstegium in high light availability openings/tree fall gaps. This suggests to me that if we open up the brush creek corridor with forestry mowing/brush cutting, the increased light levels and soil disturbance might cause a spike in Microstegium populations.  While the brush creek corridor isn’t priority #1, I know we’ll get there some day. Before we aggressively start clearing brush in this area, I’d like to have 3-5 years of aggressive Microstegium management under our belts. We have observed diminished populations in the wildflower garden, along Paw Paw Creek, and along Brush creek with just one year of management. Coupled this with a short seed viability…and we might have a winning strategy.

 

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Large patch of Japanese stiltgrass (Microstegium vimenium) along Brush Creek at Shaw Nature Reserve.

 

 

Soil and vegetation recovery on burn pile scars at Shaw Nature Reserve

Claire Waldman is a senior at Centre College. This summer, she worked with CCSD scientist Matthew Albrecht to study the legacy of burn pile scars – the ashy leftovers from burning thinned tree trunks – in a restored woodland at Shaw Nature Reserve as part of MBG’s NSF-funded Research Experience for Undergraduates (REU) program.

In December 2016, the staff at Shaw Nature Reserve began a major restoration project focusing on 60 acres of woodland that were heavily invaded by bush honeysuckle (Lonicera maackii), Japanese privet (Ligustrum japonicum), and other invasive shrubs. This work, funded by the Institute of Museum and Library Services, commenced with removal of the invasive shrubs and thinning the canopy through selective tree cutting to promote a more open woodland structure. An open canopy structure allows for future use of prescribed burns in the area to help maintain the open canopy and facilitate diverse understory vegetation.

Canopy thinning left land managers with excess woody debris – that is, there were many large, fallen trees covering the forest floor. Rather than use heavy machinery to remove the logs (which often creates a large amount of soil disruption), the wood was stacked into piles and burned. These slash pile burns create an extremely localized but intensive disturbance. The soil at the burn site becomes sterilized and covered in a layer of ash. These sites are referred to as burn scars. The layer of ash that remains, as well as the absence of vegetation, make burn scars easily identifiable.

BurnPileMontage

Slash pile burn at Shaw Nature Reserve, December 2016 (left). Barren sampling plot in a burn scar six months later (right).

Slash pile scars were distributed across the restored site at Shaw Nature Reserve. Previous research has suggested the combustion of biomass and extreme temperatures of the burns can be lethal to the soil seedbank, alter soil structure, moisture, and nutrient availability. The rate of native vegetation recovery on slash pile scars depends on burn intensity, pile area, and properties of the surrounding plant community. The native plant community in burn pile scars, without active seed addition by people, are expected to recover slowly. If the native plant community recovers slowly over time, it raises the concern that slash pile scars could serve as foci for the reestablishment and spread of invasive or undesirable species.

This summer, as part of the NSF-funded Research Experience for Undergraduates program at the Missouri Botanical Garden, I worked under the guidance of Matthew Albrecht to further our understanding of these slash pile burn scars.

First we developed a field experiment focused on native vegetation recovery in slash pile burns. In order to characterize the changes in soil nutrients, compaction, and moisture that occur in these burn piles, we took soil samples from the burn piles as well as adjacent control areas and sent them to the University of Missouri Soil and Plant Testing Laboratory. The results we obtained from this soil analysis were dramatic. Soil pH, P, Ca, Mg, and K were all significantly higher in the burn pile. Soil compaction and soil organic matter were both significantly lower in the burn pile.

SoilProperties

Soil chemical properties from samples of the top 4 cm of burn pile and control soil (Albrecht et al. Unpublished data).

While there was an apparent flush of nutrients available in these burn piles, in the first growing season after a burn occurred, we found that burn scars remained essentially bare. We created experimental burn scar plots in which we seeded six native species. The six species sown into the plots were Bromus pubescens (grass), Chasmanthium latifolium (grass), Lespedeza violacea (legume), Senna marilandica (legume), Solidago ulmifolia (composite), and Symphyotrichum drummondii (composite).  We also seeded these species in adjacent unburned control plots. We then monitored plant occupancy in these plots over the course of eight weeks.

SpeciesII

Six native plant species seeded into the burn pile scars and adjacent control areas.

We found four of the six species established significantly better in the control plots relative to the burn scar plots. These results support that while there is a significant influx of nutrients in the burn scars, there are other factors that are limiting native species establishment in the burn scars.

BareGroundReVeg

Vegetation cover in a burn plot six months after a slash pile burn (left) and an adjacent, unburned control plot (right).

PercentPlantCov

Average percent native vegetation cover (± 1 standard error) in burned plots and unburned control plots (Albrecht et al. Unpublished data).

There are restoration implications of our results. We found, of the six species sowed into the burn plots, native grasses established best. While the microenvironment created by slash pile burns presents a barrier to the restoration of native vegetation in burn pile scars, seed additions of native grasses provide a practical management strategy for promoting native vegetation recovery in burn pile scars.

PlotOccupancy

Average plot occupancy for six native herbaceous plant species in burned plots and unburned control plots. Error bars denote 1 standard error. P-values were derived from a generalized linear mixed effects model. Brpu = Bromus pubescens, Chla = Chasmanthium latifolium, Levi = Lespedeza violacea, Sema = Senna marilandica, Soul = Solidago ulmifolia, Sydr = Symphyotrichum drummondii. (Albrecht et al. Unpublished data).

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Claire Waldman recording  plant occupancy in an experimental plot at Shaw Nature Reserve.

Special Feature: Ecological Restoration in a Changing Biosphere

The following is an introduction by Leighton Reid and James Aronson to a special feature in Annals of Missouri Botanical Garden about ecological restoration in a changing biosphere. The eight papers described are derived from presentations last October at the 65th Annual Plant Symposium. The full issue can be found here.

Restoration efforts will affect large areas of the planet and hundreds of millions of people over the coming decades, but what will these actions look like, and what will they achieve? Debate continues about what constitutes appropriate restoration targets in our human-dominated and ever more rapidly changing world, and the outcome of this debate will impact the actions taken to conserve biodiversity, sequester carbon, and improve human livelihoods at large spatial scales. This special issue brings together eight scientific, historical, and journalistic perspectives to address these two critical questions about ecological restoration in a rapidly changing biosphere.

In the post-COP22 world, when all three of the UN’s “Rio Conventions” call for scaling up and mainstreaming of ecological restoration (UNCBD 2012; UNCCD 2015; UNFCCC 2015), and dozens of governments have made ambitious restoration commitments (IUCN 2016), it is clear that restoration programs will affect hundreds of millions of hectares – and as many people – over the coming decades. At the same time, we find ourselves in an era of unprecedented change where climate, ecological baselines, and future land-use changes are highly uncertain (Steffen et al., 2015). This raises the crucial question: What will large-scale restoration activities look like in the coming years?

Unsurprisingly, there are differences of opinion about the future of restoration and how to scale it up and integrate it with larger programs in an era of major, anthropogenic changes. Hobbs et al. (2011; pg 442) observe that “…the basic principles and tenets of restoration ecology and conservation biology are being debated and reshaped. Escalating global change is resulting in widespread no-analogue environments and novel ecosystems that render traditional goals unachievable. Policymakers and the general public, however, have embraced restoration without an understanding of its limitations, which has led to perverse policy outcomes.” [Emphasis added]

This perspective has received considerable attention (ESA 2016) and also pointed criticism (Murcia et al., 2014). Aronson et al. (2014; pg 647) retort that “…Restoration includes a wide range of practical possibilities for dealing with transformed ecosystems, including rehabilitation, reclamation, and remediation. Some will bring the ecosystem back to its historical trajectory, some will bring back only some attributes, but the intention is that the end product is better than the degraded ecosystem. Importantly, a label such as novel ecosystem implies no need for further intellectual exertion – and ignores the growing science of the young discipline of ecological restoration.” [Emphasis added]

The debate goes on about what we are trying to restore (Hobbs, 2016; Kattan et al., 2016; Miller & Bestelmeyer, 2016), with implications far beyond academia. Billions of dollars are now being spent to rehabilitate and restore degraded ecosystems, sometimes at large scales, and the science of restoration ecology must adapt to be integrated in larger planning and management schemes, wherein conservation, management, and restoration will all take place.

On 8 Oct 2016, we convened a panel of six scientists, one historian, and a journalist, all with long-standing involvement in the field of restoration ecology. The goal was to discuss ecological restoration in a changing biosphere at the 63rd Annual Fall Symposium at Missouri Botanical Garden. Each speaker has contributed a paper to this special issue.

The first set of papers focus on the question: Has global change outpaced and rendered obsolete the so-called “classical” ecological restoration approach? Aronson et al. (2017) say no, far from it; for example, the historically-based reference system ‒ a pillar of ecological restoration to date ‒ is more valid than ever and can indeed be adapted to landscape and higher levels of complexity. They emphasize that while restoration ecology has produced many useful ecological models, a participatory approach and consensus-building among stakeholders are crucial at these higher levels of integration. Falk (2017), in contrast, says yes: global change calls for radical rethinking of ecological restoration. He focuses on ponderosa pine forests in the southwestern US, which are undergoing a major, climate change-induced biome shift from forest to shrub land, and he concludes that a shift towards resilience-based management is necessary to supplement traditional ecological restoration. Meine (2017) takes the middle ground through an historical analysis; he notes that Aldo Leopold (1887-1948) would likely have concluded that a simple “yes” or “no” was inappropriate and that ecological novelty is neither novel nor absolute.

Whereas the first group of papers asks what we should restore, the second group focuses more on how we will restore at larger spatial and temporal scales. Brancalion & van Melis (2017) suggest that to bridge the gap between science and practice, we need to innovate; rather than refining current approaches, restoration ecologists must look outside of their disciplinary silos for fresh solutions to contemporary dilemmas. One source of new insights will be through joint research between scientists and practitioners. To this end, Holl (2017) presents several new directions for tropical forest restoration research (graduate students – take note!). She emphasizes that for research to best inform practice, it should be conducted at large spatial and temporal scales, research projects should be undertaken jointly with stakeholders, and resulting knowledge should be shared across regions. Chazdon (2017) argues that natural regeneration, more than any other method, is the key for scaling up to efficient forest and landscape restoration, and she emphasizes the need to identify priority areas where natural regeneration is maximally feasible and minimally competitive with alternative land uses. Finally, Reid et al. (2017) argue that however we restore ecosystems, we should plan to make them last; the longevity of restored ecosystems, they suggest, is variable, often finite, and determined to some degree by stakeholder preferences, environmental attributes, and the umbrella of governance. These papers emphasize tropical forest restoration, particularly in Latin America, which is appropriate given this biome’s global importance, yet the topics addressed will be of interest to readers with experience in many ecosystems.

The last word (for this special issue, at least) is left to Paddy Woodworth (2017), an international journalist with broad and optimistic perspectives on ecological restoration (Woodworth, 2013). Looking across the contributions, he observes that the words we choose have meaning and cautions against the use of the word “restoration” for anything less than the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed (SER 2004).

We hope that readers from many backgrounds, including researchers, practitioners, and policymakers, will find this special issue worth pondering as they move forward with our collective task to progress towards a more sustainable, just, and desirable future.

 

References

Aronson, J., J. Blignaut & T. B. Aronson. 2017. Conceptual frameworks and references for landscape-scale restoration: Reflecting back and looking forward. Annals of the Missouri Botanical Garden 102(2): 188–200.

Aronson, J., C. Murcia, G. H. Kattan, D. Moreno-Mateos, K. Dixon & D. Simberloff. 2014. The road to confusion is paved with novel ecosystem labels: a reply to Hobbs et al. Trends in Ecology & Evolution 29: 646-647.

Brancalion, P. H. S. & J. van Melis. 2017. On the need for innovation in ecological restoration. Annals of the Missouri Botanical Garden. 102(2): 227–236.

Chazdon, R. L. 2017. Landscape restoration, natural regeneration, and the forests of the future. Annals of the Missouri Botanical Garden. 102(2): 251–257.

ESA (Ecological Society of America). 2016. Ecological Society of America announces 2016 award recipients. The Bulletin of the Ecological Society of America 97: 337-351.

Falk, D. A. 2017. Restoration ecology and the axes of change. Annals of the Missouri Botanical Garden. 102(2): 201–216.

Hobbs, R. J. 2016. Degraded or just different? Perceptions and value judgements in restoration decisions. Restoration Ecology. doi: 10.1111/rec.12336.

Hobbs, R. J., L. M. Hallett, P. R. Ehrlich & H. A. Mooney. 2011. Intervention ecology: Applying ecological science in the Twenty-first Century. Bioscience 61: 442-450.

Holl, K. D. 2017. Research directions in tropical forest restoration. Annals of the Missouri Botanical Garden. 102(2): 237–250.

IUCN (International Union for Nature Conservation). 2016. Bonn Challenge commitments. http://www.bonnchallenge.org/commitments. Date accessed: September 22, 2016

Kattan, G. H., J. Aronson & C. Murcia. 2016. Does the novel ecosystem concept provide a framework for practical applications and a path forward? A reply to Miller and Bestelmeyer. Restoration Ecology 24:714-716.

Meine, C. 2017. Restoration and “novel ecosystems”: Priority or paradox? Annals of the Missouri Botanical Garden. 102(2): 217–226.

Miller, J. R. & B. T. Bestelmeyer. 2016. What’s wrong with novel ecosystems, really? Restoration Ecology 24: 577-582.

Murcia, C., J. Aronson, G. H. Kattan, D. Moreno-Mateos, K. Dixon & D. Simberloff. 2014. A critique of the ‘novel ecosystem’ concept. Trends in Ecology & Evolution 29: 548-553.

Reid, J. L., S. J. Wilson, G. S. Bloomfield, M. E. Cattau, M. E. Fagan, K. D. Holl & R. A. Zahawi. 2017. How long do restored ecosystems persist? Annals of the Missouri Botanical Garden. 102(2): 258–265.

SER (Society for Ecological Restoration). 2004. The SER primer on ecological restoration. http://www.ser.org/content/ecological_restoration_primer.asp. Date accessed: September 28, 2009

Steffen, W., W. Broadgate, L. Deutsch, O. Gaffney & C. Ludwig. 2015. The trajectory of the Anthropocene: the great acceleration. The Anthropocene Review 2: 81-98.

UNCBD (United Nations Convention on Biological Diversity). 2012. UNEP/CBD/COP/DEC/XI/16. https://www.cbd.int/doc/decisions/cop-11/cop-11-dec-16-en.pdf. Date accessed: 12 December 2016

UNCCD (United Nations Convention to Combat Desertification). 2015. Land matters for climate: reducing the gap and approaching the target. http://www.unccd.int/Lists/SiteDocumentLibrary/Publications/2015Nov_Land_matters_For_Climate_ENG.pdf. Date accessed: 12 December 2016

UNFCCC (United Nations Framework Convention on Climate Change). 2015. Paris agreement. http://unfccc.int/files/essential_background/convention/application/pdf/english_paris_agreement.pdf.  Date accessed: 12 December 2016

Woodworth, P. 2013. Our Once and Future Planet. University of Chicago Press, Chicago.

Woodworth, P. 2017. Meeting  the twin challenges of global change and scaling up, Restoration needs insights from the humanities as well as analysis from science. Annals of the Missouri Botanical Garden. 102(2): 266–281.

Does fire affect Eastern Bluebird nest success at Shaw Nature Reserve?

Joseph Smith is a rising senior at Lake Superior State University. This summer, he studied the effect of prescribed fire on Eastern Bluebird nesting success at Shaw Nature Reserve as part of  MBG’s NSF-funded Research Experience for Undergraduates (REU) program.

Among the rich plant diversity at Shaw Nature Reserve are a wide range of animal species, including the Eastern Bluebird (Sialia sialis). The Nature Reserve is home to an extensive bluebird trail consisting of 86 nest boxes in the north-central region of the reserve. This summer, I have been working with Dr. Leighton Reid and a citizen scientist, Lynn Buchanan, in an effort to understand the effects that land management practices have on bluebird nest success.

Prescribed fire is one of the most important management practices used at Shaw Nature Reserve. In the 2016-2017 burn season, for instance, nature reserve staff set fire to 306 ha (756 acres) of woodlands, prairies, and glades to restore and maintain open vegetation structure and a high diversity of native plants. However, it was unclear what effect these fires might have bluebirds.

FireHypotheses

Hypothetical effects of prescribed fire on Eastern Bluebird nest success. +/- symbols denote the short-term effect of fire on snakes and arthropods, and the effect of snakes and arthropods on bluebird nest success. Photo credits: (1) Black rat snake (Pantherophis obsoletus) by John Mizel CC BY-NC-SA 2.0, (2) Bluebird eggs by Bailey & Clark (2014); (3) Red-legged grasshopper (Melanoplus femurrubrum) by Gilles Gonthier; (4) Prescribed fire courtesy of Shaw Nature Reserve.

We hypothesized that fire might affect bluebird nesting success in two ways. First, fire could reduce the food supply for nesting birds. When understory vegetation burns, many arthropods are also killed, and it takes some time for their populations to rebound. During the lag, bluebirds might have less to eat, which could result in poorer nest success.

Second, fires could increase nest success by reducing the risk of snake predation. Bluebird boxes at Shaw Nature Reserve are equipped with baffles to prevent snakes from getting in, but snake predation still occurs sometimes. After a fire, there is less vegetation to hide snakes from their own predators, like raptors, and we surmised that fewer snakes could mean more successful bluebird nests.

BluebirdTrailMapLowRes

The Bluebird Trail at Shaw Nature Reserve. Bluebird nest boxes are shown in yellow.

We tested our hypotheses using a long-term dataset collected by volunteers. Over the past eight years, Lynn Buchanan and her team have monitored the nest boxes on the bluebird trail and kept records of their observations. Each week during the breeding season, they peek into all of the boxes and record the number of eggs and nestlings, how many nestlings fledged, and whether or not the nest was predated.

With statistical help from Washington University researcher Joe LaManna, we found that prescribed fire had little or no effect on bluebird nesting. We compared areas that were burned with areas that were mowed, and we also compared burned areas at different time intervals since the most recent fire (0-3 years). Likewise, we found no effect of prescribed fire on the rate of snake predation.

Species Probability of nest success (%)* Probability of snake predation (%)* Did nest success change from 2009-2016? Did prescribed fire have an effect on nest success?
Eastern Bluebird 90.8 ± 0.5 4.6 ± 0.3 No No
House Wren 92.1 ± 0.1 4.0 ± 0.3 No No
Tree Swallow 92.1 ± 0.1 4.8 ± 0.4 No No

*Standard errors are shown

While the lack of significant results can be slightly disheartening after an entire summer of work, it is reassuring that the bluebird population is thriving at Shaw Nature Reserve. Overall, we calculated that 90.8 ± 0.5% of bluebird nests produced at least one fledgling. In addition, two other species (House Wrens and Tree Swallows) that commonly use bluebird boxes also had high nest success.

There are more aspects of bluebird nesting to look at. For instance, the time from when an egg hatches until the chick leaves the nest could be longer in recently burned areas if there is less food (i.e., arthropods) available. In the meantime it appears the bluebirds are living well at Shaw Nature Reserve.

BluebirdAndBox

Eastern Bluebird (left) and bluebird nest box (right) at Shaw Nature Reserve. Photo credits: (L) Bluebird by Andy Reago & Chrissy Mclarren; (R) bluebird nest box by Rachel Weller.