fire

9th Annual Fall Tiger Beetle Trip: Day 1

/ Ted C. MacRae / 6 Comments

Once again, I have embarked upon my Annual Fall Tiger Beetle Trip, this being the ninth consecutive year that I have done such a trip. Unlike previous editions, however, the quarry on Day 1 (Sept. 15) was not a tiger beetle but a longhorned beetle. Ataxia hubbardi is not uncommon in the eastern and central U.S. and breeds in the living tissues of a variety of herbaceous plants, but especially certain species of Helianthus, Ambrosia, and Silphium in the family Asteraceae. I was hoping to see a distinctive population of this beetle that is associated with prairie dock (Silphium terebinthinaceum) in the dolomite glades just south of St. Louis. This population is interesting because individuals are smaller, darker, and narrower in form than is typical for the species, and I would like very much to get some photographs of the adults, which seem most abundant in the fall, on the tall flower stalks of their host plant.

Victoria Glades Natural Area | Jefferson Co., Missouri

I first discovered the population many years ago—back in the 1980s when I visited one particular glade, Victoria Glades Natural Area, almost weekly over a period of several years. I left Missouri for a few years in the early 1990s but returned in 1995, and during my absence fire was implemented in Victoria Glades and other glades in the area as a management practice for controlling invasion by woody plants (primarily eastern red-cedar, Juniperus virginiana). While the use of fire has certainly done much to restore the glades and improve its floral diversity, it seems more than coincidental that insect abundance and diversity on the glades is only a fraction of what I observed during my pre-burn collecting in the 1980s. There are a number of beetle species that I found at the glade historically that I have not seen now for more than 20 years; one of which is this distinctive population of A. hubbardi.

Prairie dock (Silphium terebinthinaceum) – host for Ataxia hubbardi

The prairie dock plants were at the height of bloom, but the flower stems seemed shorter and the normally large, spatulate basal leaves of the plants generally smaller than typical—perhaps a result of this summer’s severe drought. How such conditions affect the beetles is unknown. The day was also rather cool due to unbroken cloud cover and light drizzle, with temperatures in the low 70s during my visit. I spent the better part of two hours inspecting the stems of every prairie dock plant that I encountered and did not see a single beetle, so it has now been 23 years—almost a quarter century—since I’ve seen this once fairly common species at the glade. Can I prove that fire management has extirpated the beetle? No—populations might have been knocked down by the drought, or maybe the adults hide on cool, cloudy, drizzly days. Still, the pattern is too consistent to ignore, and I become increasingly worried that a special feature of these glades has now been lost.

Ninebark (Physocarpus opulifolius intermedius) – host for Dicerca pugionata

On the other hand, another quite rare beetle that I encountered abundantly at Victoria Glades in the past seems to have rebounded from its long absence—the jewel beetle Dicerca pugionata. This beautiful beetle is associated with the scraggly clumps of ninebark (Physocarpus opulifolius intermedius) that hang on in the moist toe slopes of the glades. I wrote about this species earlier this year after re-discovering it in the glades; however, I couldn’t resist taking a few more photographs of this stunningly gorgeous species. This species also makes its appearance in the fall as well as spring, and in the two hours I spent searching I counted 13 beetles—more than I’ve ever seen on any one day. Interestingly, most of these were associated with a stand of plants in an area at the south end of the glade that I had never searched before and that appears not to have been subjected to fire management (cedar removal has been effected instead with a chain saw). Only a few of the beetles were found in the much more abundant plants growing in the area of the glade I am more familiar with and that has obviously been subjected to repeated burning. It’s not proof, but I’m just saying…

Dicerca pugionata on ninebark branch.

Adult beetles are colored almost precisely the same as the bark of their host plant.

More even lighting in this face shot compared to my previous attempts.

The cool temperatures and light drizzle were not conducive to much other insect activity, but while crossing the small, shallow creek that separates the south end of the glade from the main glade, the biggest male tarantula (Aphonopelma hentzi) that I have ever seen caught my attention as it crossed the creek. Situated only 30 miles south of St. Louis, Victoria Glades must represent the northeastern limit of distribution for the species, and although I once saw a tarantula crossing the road very near to this location, this is the first tarantula that I have actually seen in the glades that lie so close to St. Louis. Males are famous for their fall wanderings, presumably in search of the females that tend to stay within their burrows. This male was missing part of one of its hind legs but otherwise appeared quite healthy and robust. I hope he succeeds in finding a mate and sires many offspring and is not discovered by any of the poachers who regularly scour the glades and steal its more unusual inhabitants—the glades have already lost enough of their unique residents…

Can you find the tarantula crossing the creek? (Hint: 0.60X, 0.37Y)

Male Aphonopelma hentzi | Jefferson Co., Missouri

Copyright © Ted C. MacRae 2012

Are we loving our prairies/glades/woodlands to death?

/ Ted C. MacRae / 25 Comments

I had such high hopes for last weekend’s collecting trip – late May is boom time for insects across Missouri, we have had good moisture this spring, and I would be visiting some high-quality natural communities that I had not visited for a long time.  My stated goals (the jewel beetles, Agrilus impexus and A. frosti) were long shots – I knew that and would have been fine coming home without those species (which I did) had the the collecting been otherwise productive (which it was not).  Still, I’ve been doing this for a long time now, and I’ve learned to draw on my accumulated experience when things don’t go as planned to give myself the best shot at turning a bad collecting trip into a decent one when things don’t go as planned.  The itinerary with which I start is rarely the one that I actually follow, and this past weekend was a good example of such.

My first stop was Ha Ha Tonka State Park, one of Missouri’s premier parks, boasting high-quality chert, dolomite, and sandstone savanna interspersed with dolomite glades.  It is on these glades and savannas that I hoped to find Agrilus impexus, or failing that at least collect a nice diversity of other jewel beetles on the oaks and hickories of the savannas and surrounding woodlands.  However, it was with some reservation that I even came here after being told by my colleague at the Department of Natural Resources just 2 days before my trip that 75% of the park’s grasslands and woodlands had been burned within the past two years.  For an insect collector, this is never good news – in all my years of collecting insects, my experience in relatively recently-burned habitats has been consistent: collecting sucks!  I decided, however, to visit Ha Ha Tonka anyway because of the quality of the natural communities it contains, thinking perhaps I might be able to find pockets of unburned habitat supporting good insect populations.  This was not to be. I beat oak after oak in the savannas and woodlands – nothing!  I swept little bluestem and Indian grass in the glades – nothing!  The foliage was lush and green and the savanna and glade landscapes highly diverse – given the time of season the place should have been teeming with insect life, yet it almost seemed sterile. Were it not for a few Chrysobothris quadriimpressa jewel beetle adults that I found attracted to a recently wind-thrown black oak tree, I would not have seen any insects here at all.  It appeared my fears about park-wide depression of insect populations had been realized.  However, not one to waste a visit I decided to explore some of Ha Ha Tonka’s fascinating geological features.  Ha Ha Tonka contains one of Missouri’s best examples of karst geology, with complex structures formed from the collapse of a major cave system.  The Devil’s Promenade is one of the more spectacular examples of such, its horseshoe-shaped cliff representing the former interior walls of a now-collapsed cave.  As dusk approached, the day’s poor insect collecting caused me to abandon my plans to stay here and blacklight for nocturnal beetles.  Instead, I decided to break from the itinerary, drive further west and explore Lichen Glade Natural Area in the morning before heading to the Penn-Sylvania Prairie BioBlitz later that afternoon.

Devils Promenade, Ha Ha Tonka State Park

Lichen Glade Natural Area is a small area owned by The Nature Conservancy that boasts a high-quality sandstone glade surrounded by post oak/black jack oak forest.  My first visit to the area more than 20 years ago was during May, and it was one of the most productive collecting trips I’ve had with a number of Agrilus spp. (including A. frosti) beaten from post oak (Quercus stellata) along the woodland edge.  I didn’t visit again until fall of 2002, when Chris Brown, Rich Thoma and I found claybank tiger beetles (Cicindela limbalis) sunning on the exposed sandstone outcrops, and I made one more visit the following May to beat more insects off of post oak.  The Lichen Glade that I returned to this past weekend was a very different place from when I last visited – the surrounding woodlands had been extensively opened (I would guess within the past few years based on the size of the post oak resprouts), and fire had been used throughout the area.  Anticipation turned to frustration when no amount of beating of the woodland vegetation and sweeping of the glade vegetation turned up beetles in any appreciable numbers (or any insects for that matter) and two hours worth of effort yielded not a single buprestid beetle!

Sandstone glade community, Lichen Glade Natural Area

With resignation, I headed on over to Penn-Sylvania Prairie, where during the introduction to the BioBlitz I learned that nearly half of the 160-acre prairie was burned last December and all of it had been burned within the past few years.  I knew what I was going to find – nothing!  Okay, I shouldn’t say nothing, as there actually were some beetles present.  However, the numbers and diversity were low, with all of the species encountered representing common, widespread species.  Moreover, it was not just beetles – all of the invertebrate group leaders (which included experts on snails, ants, butterflies, and bees) reported low overall abundance and diversity in their groups of interest.  Only the vascular plants – the metric by which the value of prescribed burning is always assessed – showed high diversity, with 300 species of mostly native prairie plants recorded for the site.  It was a fun event, with probably ~75 attendees and a delicious pot luck dinner that evening; however, it would have been more enjoyable had there actually been a nice diversity of insects present to document for the preserve.

My comments may make it seem that I am against the use of prescribed burning.  This is not true – I understand the critical role that fire as a management technique plays in restoring and maintaining examples of Missouri’s historically fire-mediated landscape. Without fire and other processes to mimic natural disturbance factors, most of Missouri’s historical grasslands and woodlands suffer relentless encroachment by woody vegetation. However, the modern landscape is very different from the historical landscape, where fires of unpredictable scale, intensity, and frequency operated within a vastly larger scale to create a shifting mosaic of natural communities in various stages of ecological succession. Such processes cannot be recreated on today’s severely fragmented landscape, where the precious few remaining tracts of native habitat are relatively to extremely small and more often than not separated from each other by vast expanses of homogeneous and “inhospitable” habitat (e.g., agricultural, urbanized, or severely degraded lands).  It is in that context that I have great concerns about how aggressively fire has been used in recent years on our state’s natural areas and the impact this is having on insect populations – specialist and generalist alike.  Fire proponents will point to published studies that show little to no effect by the use of fire for managing small, isolated remnants on specialist insects (see review in Henderson 2010).  However, there are an equal number of studies that suggest such concerns are well-founded (see review in Panzer 2002). A consistent limitation in all of the studies that have been conducted is the lack of very large and long un-burned remnants.  Prescribed burning has been adopted so rapidly and pervasively that there just aren’t any significant un-burned remnants left to properly include as controls in such studies.  As a result, the insect fauna present at a given site at the start of such a study is already skewed towards those species that successfully recolonized the area post-burn.  At a minimum, the data to this point are inconclusive, and certainly the potential for impacts has not been given the consideration it warrants in designing fire-management plans for our own state’s prairies and glades. Furthermore, as rapidly and aggressively as fire has been adopted on our few, small, widely disjuct remnants, the opportunity for proper investigation of those potential effects may be gone.  A particularly egregious example of the lack of consideration being given to prairie invertebrates in designing fire management plans is shown in these photos of Iowa’s Sylvan Runkel State Preserve before and after a late May burn and the impact of that burn on a resident population of Nevada buck moths (Hemileuca nevadensis).

Here in Missouri, as in Iowa, it’s a problem of scale – the landscape is too fragmented and remnants too disjunct to manage based strictly on floristic response.   Populations of generalist insect species will recover, and even specialist species may be able to overcome such management practices if they are widely distributed and sufficiently mobile. But what about conservative species with low vagility, such as the swift tiger beetle (Cylindera celeripes) and our disjunct population of the frosted dromo tiger beetle (Dromochorus pruinina), flightless species restricted in Missouri to the few tiny remnants of loess hilltop prairie in northwestern Missouri and a single 2.5-mile stretch of roadside habitat in west-central Missouri?  Until directly relevant data, gathered here in Missouri, are forthcoming to suggest otherwise, I believe the most judicious use of fire possible should be practiced in restoring and maintaining our grasslands and woodlands.  In-season burns may have been a part of the historical landscape, but their use today has great potential to result in local extirpations and should be used only after the most careful consideration.  Leaving un-burned refugia within remnant habitats to accelerate recovery would also be prudent – yet many land managers disregard this practice because of its logistical difficulties. This is especially true in small parcels, yet it is precisely these remnants that have the most to gain from their use (or lose from not doing so!).  In the historical landscape, every burn was a patch burn – no matter what its size, there were always adjacent or proximal unburned habitat from which recolonization could occur.  Elk and bison, too, were integral components of the presettlement prairie landscape – their roamings caused intermittent, localized disturbances that were likely not only crucial to the tiger beetles that I study but may also have contributed to vegetational diversity through patch succession.  Techniques that mimic these natural disturbance factors include mowing, haying, and managed grazing.  They can be utilized to mimic those disturbances as well as delay woody encroachment, and their use in land management should be considered for their ecological value rather than deprioritized because of their relatively greater complexity and cost to implement. Mechanical removal and selective use of herbicides offer additional tools for addressing woody encroachment while minimizing potential impacts to insect populations. An effective management program that considers all of the flora and fauna of a remnant may not be possible unless all of these management tools are utilized, or at least properly considered. As my good friend James Trager said in a recent email (quoting Andrew Williams), habitat restoration “cannot rest on any single management practice, nor practicing it too extensively.”

REFERENCES:

Henderson, R. A.  2010. Influence of Patch Size, Isolation, and Fire History on Hopper (Homoptera: Auchenorrhyncha) Communities of Eight Wisconsin Prairie Remnants.  Wisconsin Department of Natural Resources, Research Report 189, 22 pp.

Panzer, R. 2002. Compatibility of prescribed burning with the conservation of insects in small, isolated prairie reserves. Conservation Biology, 16(5):1296-1307.

Copyright © Ted C. MacRae 2010

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Blackjack oak “flower”

/ Ted C. MacRae / 8 Comments

Quercus_marilandica_P1020923_2

This blackjack oak (Quercus marilandica) was found on one of southeastern Missouri’s finest sand prairie relicts a couple of weeks ago on my ‘Annual Birthday Season Opener Bug Collecting Trip.’ Growing near the edge of the prairie at the transition to dry sand forest (Nelson 1985), the arrays of soft, red, newly-expanding leaves at each branch tip had a distinctly floral quality to them. Of course, as with all oaks, the actual flowers of blackjack oak are much less conspicuous, with the staminate (male) flowers borne on drooping catkins, the pistillate (female) flowers on separate spikes on the branch, and pollination accomplished by wind.

Missouri is oak country – nearly a quarter of North America’s 90 oak species (Nixon 2009) occur naturally within the state. This high diversity is explained partly by Missouri’s ecotonal continental position – straddling the east-west transition from the great eastern deciduous forest to the western grasslands. The boundary between these two great biomes is a dynamic, ever-changing interdigitation of woodland, savanna, and prairie that ebbs and flows with the prevailing climatic conditions. Unlike the more mesic forests further east, these dry woodland habitats were often subjected to fire during presettlement times – to which oaks in general (and blackjack oak in particular) are supremely adapted with their thick bark and ability to resprout repeatedly after being burned or grazed back. Sadly, the suppression of these fires post-settlement has caused many of these unique, fire-mediated natural communities to shrink drastically amidst a choking growth of junipers (“cedars” ’round these parts), maples, and other fire-intolerant species. Only on publicly owned preserves and a few private parcels under progressive ownership (such as the sand prairie relict where this photograph was taken) is fire once again shaping the landscape.

Oaks are among my favorite trees, and among the oaks I have several favorites. White oak (Quercus alba) – tolerating many forest types but forming nearly pure stands in high-quality, mesic sites, its tall symmetrical crown, pale bark, and brilliant fall colors are unparalleled among Missouri’s other oaks. Post oak (Q. stellata) as well – lacking the elegance of white oak but achieving its greatest character in fire-adapted savannas and open woodlands as squat, gnarled, massively-trunked trees with broad, spreading crowns¹. Blackjack oak has none of these qualities, yet somehow, it is still one of my favorite Missouri oaks. Stunted and gnarled (‘scrub oak’ to some), it occurs mostly in sandstone and limestone glades, savannas and woodlands on dry, nutrient-poor soils that support few other tree species. The dark green of its tough, waxy (to limit the loss of water), pear-shaped leaves contrasts beautifully with its rough, blocky, almost black bark. Blackjack oak has virtually no timber value, although it is sometimes used for charcoal and firewood. Nevertheless, for me, it is almost an icon for the unique natural communities in Missouri in which it occurs – communities that face ever-increasing pressure from human and forest encroachment.

¹ Please refer to this lovely essay about post oaks in Missouri, by the talented Allison Vaughn.

REFERENCE:

Nelson, P. W. 1985. The Terrestrial Natural Communities of Missouri. Missouri Natural Areas Committee, Jefferson City, 197 pp.

Nixon, J. C.  2009. Quercus in Flora of North America, Vol. 3.

Copyright © Ted C. MacRae 2009

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