Thursday, January 28, 2016

Fall Fire for Effective Management: Is There a Seasonal Affective Disorder in Prescribed Fire?

Over the years, I have noticed several intriguing responses in natural communities to seasonal variations in prescribed fire. I've discussed this issue with many folks, have initiated several interesting, though largely unsatisfying, email strings on the subject and wrote an essay on the subject in a recent Missouri Natural Areas Newsletter. Through this process, I have found that the increasing utilization of spring burning, as opposed to the more historically relevant application of autumnal anthropogenic burning, is primarily driven by convenience rather than ecological soundness. And, that the assumptions underlying the prescription of spring fire (that either spring fire is harmless or that it is at least better than no fire at all) are potentially more wishful than accurate. Having observed significant losses in plant diversity and subsequent increases in weedy shrubs like sumac and blackberries in areas where spring fire has reigned supreme, my concern has only grown. Steve Buback (Natural History Biologist for the Missouri Department of Conservation), sharing my concerns, suggested we investigate the matter via a summary of the pertinent literature on the subject and present the summary at the Missouri Natural Resource Conference. So, that is what we are doing. On Friday, February 5, 2016 Steve Buback and I will be presenting a talk on the effects of spring and summer prescribed fire compared to fall and winter prescribed fire.

On the surface this appears to be a dense or debatable topic. However, after an exhaustive review of the literature, I was surprised to find that it really isn't. It is quite simple really. Given this, Steve and I agreed to post the literature summaries in advance. We are hoping a few people will help catalyze any questions/discussion via this forum and thereby help us to be better prepared for Q&A after the presentation. We are also hopeful that this little bit of publicity will get more folks in attendance, since the talk is on Friday (last day of the conference) and the title isn't horribly provocative.

So, I'll start the talk with a rundown of why people used to burn and why we burn now. Basically modern burning (in North America, mind you) falls into two camps; 1) managing rangeland for cattle production with a heavy bias for grasses and 2) to promote and/or support biodiversity. There may also be a tad of fire use to promote forestry here and there. Because most prescribed fire in Missouri is done through public and private conservation agencies, most of it is directed toward promoting and/or supporting biodiversity; a rich assemblage of plants, animals and all creatures great and small.

Unfortunately, I could find zero published results on the effects of seasonality of fire in woodlands and forests. All of the literature involves prairie habitats and even then it is sparse. The phenomenon shouldn't be much different, and if it is different, one would expect to see more exaggerated results in woodlands and forests since there is a higher ratio of C3 graminoids and forbs to C4 grasses in woodland and forests: the effect we are concerned about. Here are the results of the studies directly testing hypotheses of seasonality on plant community structure and composition followed by a summary/synthesis:  

Towne and Kemp 2003 – 8 year study using annual fire (previous 3-4 year interval)
-Spring burning (late April) compared to winter (February) and fall (late November)
  Spring Burning resulted in…
  -decreased richness of C3 grasses and perennial forbs
  -decreased diversity of C3 grasses and perennial forbs
  -decreased productivity of C3 grasses and perennial forbs
  -complete loss of five annual species
  -no increase in C4 grass productivity
  Also found that… 
  -Big Bluestem increased regardless of season
  -Indian Grass proliferated with spring burning
  -Carex spp. increased 14% with autumn and winter; decreased to 3.5% in spring
  -Cool season grasses increased 22% in autumn and winter; decreased 5% spring
  -most legumes tolerated but did not benefit from spring burning
  -woody species showed no change (low density to begin with)

Towne and Craine 2014 – continuation of 8 year to a 20 year study
  -grass biomass remained unchanged from autumn, winter and spring burns
  -June Grass increased from 3 to 11 percent in autumn and winter
  -June Grass was eliminated from spring plots
  -Indian Grass stayed constant in autumn and winter
  -Indian Grass doubled in spring (increase indicative of lost diversity in glades)
  -spring burns reduced biomass by 50%
  -spring burns had increase in 5 species (average C-value = 4.7)
  -winter and fall saw increase in 6 species (average C-value=6.2)
  -Carex spp. increased 8 to 14 percent in autumn and winter
  -Carex spp. decreased from 6 to 1 percent in spring

  -woody plants stayed constant across treatments

Owensby and Anderson (1967) and Aldous (1934) – early studies from Konza
Compared early (Mar 20), mid (Apr 10), and late spring (May 1)
  to fall dormant season burns (not in Owensby and Anderson 1970).

          -C4 grass productivity increased from fall (lowest) to late spring (highest) 
          -weeds decrease by a ~ ¼ after early spring and ~ ½ after late spring

Weeds as defined by Aldous (1934): “There are several species of forbs, or broad-leafed plants. In pastures most of these are considered as weeds and will be designated as such. These forbs fluctuate in abundance from year to year. The most abundant ones include:

            -perennial ragweed (Ambrosia psilostachya) [C=3]
            -many-flowered aster (Aster ericoides) [C=5]
            -pasture sage (Artemisea ludoviciana) [C=3] [
            -whorled milkweed (Asclepias verticillata) [C=2]
            -prairie cat’s-foot (Antennaria neglecta) [C=4]
            -Missouri goldenrod (Solidago missouriensis) [C=6]
            -stiff goldenrod (Solidago rigida) [C=5]
            -blue-eyed grass (Sisyrinchium campestre) [C=5]
            -wild flax (Linum texanum) [C=5]

and about a half dozen other species of minor importance.”

Howe 1994 – early flowering vs. late flowering in experimental prairies in WI

  -compared spring (March 31) and mid-summer (July 15) burns
  -early flowering perennials (flowering before mid-July) planted prairie
          -cover was 17% in controls, 6% in spring burn and 46% in summer
  -late flowering perennials (flowering after mid-July) in remnants
          -cover was 80% in controls,  92% in spring burn and 47% in summer
     -spring fire hurts early perennials and encourages late perennials
     -summer fire hurts late perennials and encourages early perennials

Hajny, Hartnett and Wilson 2011 – 2 and 10 year study of fire effects on Smooth Sumac
 Fall (November), Winter (January), Spring (April), Summer (July); backfires and head fires

Part 1: Effects of seasonality

  -all treatments had dramatic stem mortality (80 to 99%)
       -summer burns had fewer resprouts post treatment
       -but lower mortality due to fuels (no net loss)
       -spring had the most resprouts 
       -fall had no significant change in resprouts
  -fire increased plant size and fruit set compared to unburned
       -thus no reproductive cost to sumac (resprouts or fruit)
       -summer and fall had the lowest seed set and lowest resprout
       -winter and spring had highest (>double fall or summer) 2 year study.
-suggests that summer burns could be the best management for sumac
       -10 year data demonstrates dramatic increase from summer burns
       -long term, summer burning is the worst scenario for stem density

-In terms of resprouts, new sprouts and seed production in long term study
       -spring burns showed most dramatic increases overall (worst option)
       -fall burns showed most decrease (best option)
       -winter was second best option
       -summer was third best option

Part 2. Fire Intensity (backfires vs. headfires)(no summer component)
  -spring backfires resulted in higher density of stems than
    fall or winter backfires or head fires
  -backfires and headfires in all seasons but winter and fall
    resulted in increased sumac
  -fall backfires resulted in zero population growth
  -winter backfires resulted in the only decrease
Given the long-term results, the lower number of stems and seeds produced, the stable population growth and suitability to herbaceous grass and forb diversity and productivity (from other studies), low intensity fall backfires provide for the greatest biodiversity and ecological function. 

In summary
  Minor disagreement – whether late spring increases productivity of C4 grasses
                 -Contemporary research demonstrates no difference between seasons   
                 -Older research demonstrated that late spring was best but for production of quality for 
                   forage, not biodiversity(weeds)

  Minor disagreement – seasonal effects of fire on woody plants 
                  -Most show nothing deters established woody plants in the long-term
                  -Others show that late spring and growing season fires increase woody plants like sumac,                       blackberries and dogwood.
   There is unanimous agreement  (Abrams and Hulbert 1987; Heisler et al. 2003;   Briggs et al.  2005;     Lett and Knapp 2005; Bidwell and Engle 1992; Engle and Bidwell   2001; Towne and Kemp 2008;         Dacy and Fulbright 2009; Owensby and Anderson   1967  and Anderson et al. 1970; plus above)           that…
                  -burning increases productivity compared to not burning (but maybe not    vs. haying)
                 -after forbs and C3 grasses break dormancy (late February to early March) their rates of                          mortality increase with the lateness of burning season
                 -any herbaceous plant that is actively growing will be negatively impacted by fire to some                      degree
                                -the degree depends on how advanced it is into growth cycle and fire intensity
                 -fire does not deter established shrubby plants (maybe winter backfires)

If an herbaceous plant is actively growing, it will be negatively impacted by fire.

Spring fire decreases C3 grasses and forbs, favors C4 grasses and increases shrubby
species recruitment and densities (carries high potential of net loss to biodiversity).

Fall fire increases richness, diversity and productivity of C3 grasses, C4 grasses, and
forbs and doesn’t encourage shrubby species (if shrubs aren’t an issue, winter is next best).

We don’t know enough about summer fire to apply it except under special circumstances
where the collateral damage is understood and acceptable. 
The End

Well, that's it. I'd be interested in anyone's thoughts or questions. Thanks!

Literature Cited

Abrams MD, Hulbert LC (1987) Effect of topographic position and fire on species composition in tallgrass prairie in north-east Kansas.  American Midland Naturalist, 117, 442-445.

Aldous AE (1934) Effect of burning on Kansas bluestem pastures. Kansas Agricultural Experiment Station Bulletin 38.

Anderson KL, Smith EF, Owensby CE (1970) Burning bluestem range.  Journal of Range Management 23, 81-92.

Bidwell TG, Engle DM (1992) Relationship of fire behavior to tallgrass prairie herbage production.  Journal of Range Management 45, 579-584.

Briggs JM, Knapp AK, Blair JM, Heisler JL, Hoch GA, Lett MS, McCarron JK (2005)  An ecosystem in transition:  causes and consequences of the conversion of mesic grassland to shrubland.  Bioscience 55, 243-254.

Dacy EC, Fulbright TE (2009) Survival of sprouting shrubs following summer fire:  effects of morphological and spatial characteristics.  Rangeland Ecology and Management 62, 179-185.

Engle DM, Bidwell TG (2001) Viewpoint:  the response of central North American Prairies to seasonal fire.  Journal of Range Management 54, 2-10.

Hajny KM, Hartnett DC, Wilson WT (2011) Rhus glabra response to season and intensity of fire in tallgrass prairie. International Journal of Wildland Fire 20  709-720

Heisler JL, Briggs JM, Knapp AK (2003) Long-term patterns of shrub expansion in a C4-dominated grassland: fire frequency and the dynamics of shrub cover and abundance.  American Journal of Botany 90, 423-428.

Howe HF (1994) Response of Early- and Late-Flowering Plants to Fire Season in Experimental Prairies Ecological Applications, Vol. 4, No. 1 (Feb., 1994), pp. 121-133

Lett MS, Knapp AK (2005) Woody plant encroachment and removal in mesic grassland:  production and composition responses of herbaceous vegetation.  American Midland Naturalist 153, 217-231.

Owensby CE, Anderson KL (1967) Yield responses to time of burning in the Kansas Flint Hills. Journal of Range Management 20, 12-16.

Town EG, Kemp KE (2003) Vegetation dynamics from annually burning tallgrass prairie in different seasons. Journal of Range Management 56, 185  192.

Towne EG, Kemp KE (2008) Long-term response patterns of tallgrass prairie to frequent summer burning.  Rangeland Ecology and Management 61, 509-520.

Towne EG, Craine JM (2014) Ecological Consequences of Shifting the Timing of Burning Tallgrass Prairie. PLoS ONE 9(7): e103423

Saturday, January 16, 2016


There are so many questions in field ecology. And there are those of us that obsess over the answers. We obsess because the questions gnaw at our psyches, needle the tender pink concavities of our brains, and boil up hot lava plumes of dissatisfaction as we dig deeper into the pleasure of nature study. They haunt us the way any puzzle haunts any person, only amplified. Instead of a word jumble over morning coffee, field ecologists face vast expanses of dead and living landscapes that have been scattered, smothered, covered, chunked, diced, peppered, capped and topped (not unlike Waffle House hash browns) across millions of years of ecological transition and evolutionary time. They have cooked into a steamy stew of wondrously bewildering patterns, pseudopatterns, and near trends. Good field ecologists savor their thick saucy sweetness.

Science, as a social function, thrives on questions. It is a progressive endeavor. In my estimation, the best field ecologists are those thirsty with questions. They are also almost always field botanists. I attribute this to several factors; 1) ecology is the study of energy flow; 2) photosynthesis is the sole source of all energy that enters terrestrial ecosystems (and the vast majority of aquatic ecosystems); 3) the structure and composition of botanical communities dictate the structure and function of all subordinate (in terms of energy flow) forms of life. Thus, the more intimately one knows a flora, the more insight one has into the past states, current condition and ultimate potential of a given area. I can’t state strongly enough that this type of knowledge is paramount to wise use and sound management. 

On a side note, this is also the reason I get squeamish this time of year as I see the flurry of summer job postings for “seasonal botanists”, in stark contrast to the complete absence of “professional botanist” jobs. No, it appears the conservation field is now defining "botanists" as an undergraduate student looking for an intern-like position who also has a penchant for thumbing their way through a Newcomb’s guide or equivalent. Once they’ve gotten their summer of wildflower romping out of their system they’re ready for more technocratic endeavors like manning ARC-GIS machines or computer modeling; no doubt drawing on the vast ecological wisdom a single season in the field has garnered them. And while the maps and models fly around with perpetually inbred logic, and they are ushered into other dubiously titled positions, there remain no professional avenues for the truly seasoned botanists; those driven by ecological or botanical phenomenology: the study of real systems and real organisms in real time. 

Which brings us to Juncus brachyphyllus. Between 1922 and 1974 Juncus brachyphyllus was documented by collections at least 28 times in Missouri (based on current Flora of Missouri Project database at Because no verified collections had been made since 1974, it was added to the state list of species of conservation concern as State Historic (SH), which isn’t too far a jump from State Extripated.

As a die-hard Juncus fan, I began looking for Juncus brachyphyllus in the early 2000’s as I botanized and/or sampled the prairies of southwest Missouri. I must have decapitated several hundred innocent Juncus dudleyi and J. interior in order to investigate the nature of their septa; the key-based character needed to distinguish J. brachyphyllus from these two similar species. As the keys read, the septa of J. brachyphyllus are complete and fully divide the ovary into three distinct locules, whereas the septa of J. dudleyi and J. interior are incomplete (not connected in the center); thus while the capsules are technically tricarpellate in all three, they are unilocular in the latter two.  

One day in 2013 my search for a rediscovery of Juncus brachyphyllus in Missouri ended. I was conducting a botanical survey for a private landowner in Hickory County. I had just gotten to the site and was talking to the landowner when about 20 feet away I saw a Juncus inflorescence sticking up in the grass. Instantly I knew it was different. It was taller than the ubiquitous J. dudleyi. It had a thicker stem. It had a more condensed inflorescence that was distinctly cinnamon brown. I attempted to politely and simultaneously uphold my end of the conversation and contain my excitement as I slid closer to the plant that I already knew was going to be J. brachyphyllus. It was. 

The very next morning I had business on Golden Prairie where I had been working earlier in the week. No sooner had I stepped out of the truck, when I spotted a stem of J. brachyphyllus. That’s two modern collections in two days! Since then I’ve been on twenty or more prairies in the Unglaciated Prairie Natural Division and at each of them I have found healthy populations of J. brachyphyllus without even trying. The “state historic” hypothesis, though functionally useful for raising awareness, was completely false. Sadly, the only thing historic was our ability to recognize this common member of our prairie flora.

Juncus brachyphyllus is a prairie species. Its complete range is prairie. So imagine my confusion when I also began finding it in the Ozarks. Everyone knows there is no prairie in the Ozarks, right? There are glades (edaphic prairies), there are historically open woodlands and savannas, but prairies? Okay, there are small prairie properties like Tingler Prairie near West Plains but that is it. All right, there are rumors of very large historic prairies like Lanes Prairie in Maries County. And sure, there are large prairie stretches with highly conservative prairie flora all along the I-44 corridor from Springfield to Pacific; all along highways 68, 32 and 19 radiating from Salem where Schoolcraft noted extensive prairies; all along highway 60 from Springfield to Mountain View or just about any highway or road in the broad upland zones of the entire Springfield and Salem Plateaus. And, okay, maybe Paul Nelson did mention in the Terrestrial Natural Communities of Missouri (1987, 2005 and 2010) that there were scattered prairies of just about every prairie type that occurs in Missouri in the Ozarks and that they consisted of 100 to 1000 acre patches. And if you really think about it, I guess Schroeder (1981), a mere 35 years ago, did well document via land survey notes large prairie stretches in the Ozarks. But there are NO prairies. Besides Tingler Prairie, they did not exist nor do they exist in the minds of most professionals in the field today. We never talk about them. There is no active project to document, survey or secure them. The public certainly is oblivious.  So while they may have existed, they may as well never have.

It's kind of sad. On one hand we have a plant that the professionals charged with protecting couldn’t identify (myself included) and on the other an entire community type (actually several types) that is completely off the radar on an ecoregional scale. What is even sadder is that these seemingly non-existent Ozark Prairies were/are phenomenal! They were unlike any other prairie expression in terms of structure and composition at all scales (community, population and genetic). I’ve actually walked on a few of these remnants and have marveled at combinations unseen elsewhere, as species characteristic of Ozark woodlands intermingle with classic prairie notoriety. Here are some photos of them in situ.

Delphinium carolinianum, unlike D. virescens which is more often associated with the Tallgrass Prairie ecoregion, is mostly found on limestone glades in the Ozarks. However, this photo was taken in an Ozark prairie remnant on soils derived from Roubidoux Sandstone. The population only consisted of a half dozen stems. 

Desmodium sessilifolium is a common species of prairie inside and outside the Ozarks. It is one of the more disturbance tolerant species and thereby serves as a decent indicator of prairie influence. 

Gymnopogon ambiguus is an odd duck. Primarily a grass of the Coastal Plain it likely sneaked into the Ozark prairies during the hypsithermal. 

Helianthus occidentalis was likely a common element of Ozark prairies especially given the often dry sandy soils of Ozark uplands. 

Helianthus x cinereus is a hybrid between the last and the next species. Because hybridization has a functional role in many communities, this is a wonderful thing to see in the Ozarks.

Helianthus mollis is a classic Tallgrass prairie species that does not occur on glades in the Ozarks. Its presence is highly indicative of remnant prairie.

Juncus brachycarpus is not a hardcore prairie species, but its prevalence in Ozark prairies as well as Tallgrass prairies to the west is interesting and fun. 

Liatris hirsuta is commonly considered an Ozark woodland species. But its geographical distribution actually indicates that it is a species of the east central Tallgrass Ecoregion with a range extension into the western Ozarks. Since most of the Ozark prairies are gone or overgrown, the perception of it as a woodland species is likely derived more from displacement than historic relevance.

Monarda bradburiana is primarily a woodland species, but it fits right into smaller Ozark prairie remnants. It makes one wonder just how much prairie blood is coursing through its veins. 

Andropogon ternarius is another species that seems to have been more common in Ozark prairies in Missouri than in our actual prairies.

Platanthera lacera is one of the weedier of the prairie orchid ilk, but, like in bigger prairies to the west and north, it is quite at home in the Ozark prairies. 

Polygala incarnata is one of several species that occur in shallow sandy soils of prairies in southwest Missouri. It does the same in Ozark prairies.

Orbexilum pedunculatum is equally at home in Ozark woodlands, Tallgrass prairies and prairies of the Ozarks. It is another one of these species that if you learned it in the Ozarks you think of as a woodland species, but if you learned it in prairies you think of it as a prairie species. Both are right. I feel this type of interface between the two ecotones is what makes Ozark prairies so specieal. 

Prunus munsoniana forms wonderful mounded thickets in prairie country and offers habitat heterogeneity and tasty plums for wildlife. Its range seems to overlay the Ozark prairie zone very well.

Andropogon scoparius (not Schizachyrium; a taxonomically useless moniker). You couldn't cry "prairie" without it. Like in Tallgrass prairie, it is/was a matrix species in Ozark prairie.

Escaped fire gave this remnant another breath of life. This is part of a patchy network of roughly 80 acres in Dent County that may represent one of the largest remnant Ozark prairies. Because no one is conserving or even investigating Ozark prairies, we have no idea of their current extent or condition; a fact that finds me staring at the ceiling on many a sleepless night.

The areas surrounding the few remnants I've seen consist of large fescue fields with odd jigsaw puzzled borders of tree line. I do not believe that these jigsaw puzzle borders are a coincidence. I suspect they represent historic prairie woodland interfaces. If only we had more time, more resources, more people with the requisite aptitude and fervor for natural community protection and restoration we might save some shining examples of this wholly unique clash between prairie and Ozark histories; this living example of explosive biological dynamism. Perhaps the first step is just getting people to see, in the hope that in seeing they will understand. And sometimes understanding is all we can ask for.