Saving Nebraska’s Oak Woodlands… by Burning Them

Last week, I helped arrange a tour of recently-burned oak woodlands at Indian Cave State Park, an eastern Nebraska site owned and managed by Nebraska Game and Parks Commission.  Indian Cave State Park is one of very few deciduous woodlands in Nebraska that is managed with prescribed fire.  The Nature Conservancy’s Rulo Bluffs Preserve is another, but while we started using fire back in the mid 1990′s, we’ve not been able to use it as consistently as we’d like.  Seeing the results of four years of annual burning at Indian Cave State Park was a good incentive to keep trying to find ways to increase our burn frequency down at Rulo.  You can read here about a fire we conducted at Rulo last year.

Kent Pfeiffer (center) stands in a portion of woodland that has been burned four years in a row and points out some of the changes that have occurred over that time.

The tour was led by Gerry Steinauer (state botanist for Nebraska Game and Parks) and Kent Pfeiffer (Northern Prairies Land Trust), who have been leading the charge for woodland burning in eastern Nebraska.  In addition to Kent and Gerry, and several other Game and Parks biologists, the tour group included staff from the Nebraska Forest Service and the Bureau of Indian Affairs.

We started by talking about why Game and Parks is implementing prescribed fire at Indian Cave State Park.  Some of those reasons include:

- Fire topkills small understory trees and shrubs, and repeated fire can eventually kill them completely.  Mature trees – especially oaks – are largely immune to even frequent fire, so they survive, keeping the canopy of the woodland intact.  The end result of frequent fire is a more open woodland structure that promotes herbaceous plants such as grasses, sedges, and wildflowers of all kinds.  Kent and Gerry are aiming for something around 80% canopy coverage of mature trees, with very few understory trees, so that as the sun moves across the sky, woodland plants receive a mixture of sun and shade off and on during the day.  This keeps those woodland plants cool enough to survive, but gives them enough light to thrive.  Since the majority of woodland species (plant and animal) live in the herbaceous community, maintaining a diversity of plant species at the ground layer is particularly important.

A hiking trail used as a fire break for a recent prescribed fire. The woodland area to the left has not been burned (for many decades) and the area to the right was burned this spring.  There is a dramatic visual difference between the two – primarily because the abundance of small trees and brush makes it impossible to see more than a few feet into the unburned area.

- Fire removes leaf litter, as well as understory brush, and allows more light to hit the woodland floor.  This helps oak seedlings survive – a critical component of woodland ecosystems, because without that regeneration of oak trees, there will be no oaks to replace the mature trees as they die out.

Frequent fires will promote the survival of these oak seedlings, which would otherwise stand no chance of growing into mature trees.

- In addition to the habitat and plant community benefits, there are benefits to human visitors as well.  A woodland with an open understory is much more pleasant to walk through, making hunting, birding, or hiking easier and more fun.  Kent talked about how much nicer the temperature is in burned oak woodlands on summer days because the open understory allows a breeze to come through and prevents the kind of stifling heat found in unburned woodlands.  Plus, woodland burning suppresses poison ivy, which most hikers appreciate…

Gerry Steinauer stands in an area of woodland that has been treated with frequent fire, as well as some “hack and squirt” herbicide treatments to help kill smaller diameter trees. Note how far you can see into the woods because of the open understory – and the abundance of plants growing on the woodland floor.  Many of the smaller diameter trees in the photo are dead, but still standing (temporarily).

While those justifications are all good, Kent pointed out that there is a more comprehensive question that we need to answer in Nebraska.  If we want to have oak woodlands 50 years from now, we have to make that decision now, and start changing the way we treat our current sites.   Most oak woodlands in the state are essentially unmanaged.  Another couple of decades of that kind of hands-off approach, and many of the mature oak trees will die without replacing themselves, allowing the current understory of hackberry, ash, white mulberry, and other tree species to become the new canopy.  Those tree species don’t create leaf litter that can carry fire, so fire will no longer be a management option – meaning that it will be nearly impossible to create the kind of woodland habitat structure that birds and other woodland animals, as well as most plant species, depend upon.  The forest will still support life, but it will be a dramatically different community than we have now.  We have to decide as a society whether we value oak woodland enough to do what we know is necessary to maintain it into the future.

An abundance of perennial sunflowers is typical of woodland plant communities in transition from a dense shady forest to an open woodland. Over time, the herbaceous layer on the forest floor will become much more diverse as other species, including grasses, sedges, orchids, and many more, increase in abundance.

Nebraska is a little late to the party in terms of burning oak woodlands.  Other states like Missouri and Wisconsin (among others)have a strong record of utilizing fire to manage their woodlands.  You can also read here about the innovative work Bill and Sybilla Brown are doing in Iowa.  In those other places, the discussion revolves around how often to burn – not whether or not to burn in the first place.  Here in Nebraska, we’ve seen a dramatic increase in the use of prescribed fire to manage grasslands over the last decade or two.  Now we need to shift some of our attention to oak woodlands as well – and we need to do it before it’s too late.

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About Chris Helzer

Chris Helzer is an ecologist and Eastern Nebraska Program Director for The Nature Conservancy. He supervises the management and restoration of approximately 4,000 acres of land in central and eastern Nebraska - primarily along the central Platte River. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press.
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22 Responses to Saving Nebraska’s Oak Woodlands… by Burning Them

  1. chad graeve says:

    Chris, so well stated. We’ve been learning that more frequent fire in the woodlands is better for the oaks and the invertebrates. Burning in the oak woodlands with several years accumulation of fuel is a much hotter burn than burning one season’s fuel. The hotter fires are certainly good for top-killing more of the target woody species, but they also impact the detritus and soil dwelling invertebrates and they scar a much larger percentage of the oak trees. Annual fires are much more patchy – leaving refugia at a scale that is relevant to invertebrates rather than land managers peering at aerial photos. We’re moving to annual fire as a maintenance (and healing) practice and relying on the saw and herbicide as a restoration (and killing) practice.

    Keep up the great work!

    • Chris Helzer says:

      Thanks Chad. Good info. Do you know of any research papers that have quantified the detritus/soil invert impacts? I can see that accumulation of several years would have a greater impact, though my observation is that oak leaf litter doesn’t really survive well from one year to the next – or is so matted down that it might not add much to burn intensity. But this is definitely not my area of expertise! Thank you for chiming in.

      • chad graeve says:

        Chris,

        No papers that I can lay my hands on at the moment, though if time permits I can dig around. However, I vividly recall dragging a torch through the woods one fall several years ago when I crossed from a west aspect to a north east aspect where the oak leaf litter was mid-calf deep. I literally sunk into the leaf litter with each step. It was an accumlation of fuel from several years. The leaf matter will get compressed. But if drying conditions are favorable, that leaf litter will burn and hold heat closer to te soil surface for a greater duration. A single season’s fuel is elevated and allows the fire to burn quickly and permits skips at a meaningful scale.

  2. James C. Trager says:

    When I head up your way this summer, I’d like to plot a course that includes a stop at the Rulo Bluffs site, if it’s not too much out of the way.
    We started burning oak woodlands at our eastern Missouri site 20 years ago, and one unit has had ten burns in that time. In a sense, it “looks the best” – open structure, excellent herb layer, some oak and hickory recruitment and very little mesic forest tree recruitment. On the other hand, the less frequently burned sites are exhibiting these features, too, and contain some really beautiful spots, but are more evidently troubled with invasive honeysuckle (vine and bush) and privet. The fact that at least the last ten winters have been mild, and most recent summers have been relatively wet and mild has also helped these invaders. Various climate models predict more of the same for this region, so we’re coming to believe that more, not less, fire in the woods will be necessary to maintain the restoration gains already made.

  3. melmannphoto says:

    Growing up in the south we burned in the pine forests as well to give the seeds a chance of getting to the ground. Longleaf pine is fairly resistant to slow burning fire whereas the faster growing varieties are not. With this we could clear the underbrush and select for the more valuable longleaf at the same time. Some people complain that forests without underbrush look artificial but I like being able to see for a distance into the forest.

  4. My wife and I have been following the efforts of the local DNR crew to eliminate honeysuckle from a white and red oak/shagbark hickory woods. There, frequent burning has led to a great deal of soil erosion and virtual elimination of some herbaceous species. The understory in various parts of the burned areas is still barren, the mushroom populations have been set back or eliminated as their source of energy is burned off. The honeysuckle responds by vigorous resprouting at the base and because the root structure is not harmed a honeysuckle shrub can grow 3 or 4 feet in a single season. The diversity of herbs has been reduced to a dominance of white snakeroot (Eupatorium) and lots of Desmodium and hog peanuts (Amphicarpaea). Fern populations have responded in surprising (to me) ways. Maidenhair fern is doing well but fragile ferns have been eliminated in many areas. The monoculture of thin leaved sunflower is attractive but not normal. Frequent burning is not, in my opinion, the way to re-establish oak areas. It creates a nice clean understory but not a natural understory. Where is the seedbank for greater diversity on the woodland floor? Are there no understory trees in NE – like ironwood, cherry, buckeye?

    • Chris Helzer says:

      Michael – Thanks for the response. I think your observation is a good reminder that it’s necessary to evaluate strategies like this as they are implemented to be sure they’re doing what was planned.

      • James McGee says:

        Chris, You are an actual ecologist, so may be you can explain the concepts better than myself. At the 2011 Wild Things Conference, Greg Spyreas gave an excellent talk about historical fire frequencies in oak woodlands.

        http://www.habitatproject.org/wildthings2011/session.php?sid=G4

        In this talk he discussed the ecological threshold at which an oak woodland, in the absence of fire, can no longer be restored to the original state. After a certain period without fire, management efforts like species removal and prescribed fire will only be able to return the system to a much reduced ‘alternative state.’ The photo of a woodland with an understory composed of only woodland sunflower is probably a good example of this trajectory. The fact that restoring former conditions has often been unable to return the ecosystem is well known. This link discusses indepth the topic of a trajectory toward an alternative state from restoration efforts.

        http://www.jlakes.org/web/Alternative-states-positive-feedbacks-restoration-ecology-TEE2004.pdf

        The belief that an ecosystem can rise once again from the seed bank is a restoration legend that has not been observed by those conducting the work. What is observed is species which are barely able to hang on again become noticable with the return of favorable conditions. I have heard people describe this recovery as ‘ecological release.’

        What people should know is that not burning oak woodlands will cause the ecosystem to be completely lost after a certain number of years. After this point has been reached, restoring an oak woodlands is effectively like starting from scratch. It is a long process that may never return to the high diversity state that once existed. This is the reason taking immediate actions to prevent any further decline is imperative if these rich ecosystems are to continue to exist into the future.

        James

        • Chris Helzer says:

          James, I think you’re right that a woodland (or any other ecosystem) can reach a point at which it has changed stable states (see my earlier posts on ecological resilience). With oak woodlands, I’m not sure we know enough to predict where that point is. The Timber Hill site I mention in the article is a great example of a site where the Browns have seen amazing recovery from a condition that looked pretty grim early on. Kent says the Browns talked about those sunflowers as a transition stage, and that – at least for them – the sunflowers eventually gave way to a nice diverse herbaceous plant community. I’m certainly not ready to say that the same will happen in other woodlands – or that there’s a good way to predict one way or the other. I think your last sentence is right on – it’s best not to let things get to the point where we’re uncertain about our ability to turn everything around again.

  5. Jarren says:

    Chris, Great article. Do you have any thoughts on how woodland burning in NE might be justified from an economic standpoint for production-minded private landowners? I realize many farmers/ranchers see woodlands as waste areas, rather than places to invest in. Alternatively, any benefits for timber harvest might be seen as counter productive. Thoughts?

    • Chris Helzer says:

      Jarren, it’s a great question. And a simple answer. Nope, I don’t have any good thoughts on that topic! I don’t have enough experience to propose anything. I’d love to hear from others that DO have good thoughts about it though!

    • Kent says:

      Hi Jarren,

      It may not directly apply to the Missouri River Bluffs, but our old friends Dave and Jon (among several others) have made favorable comments about the impact of burning oak woodlands on their ranching operations in Jefferson County.

      Did you make it back to Cody, or are you still in Idaho?

  6. david burg says:

    Would welcome any references to studies that compare grazing to burning in oak woodlands, or a combo of the two. I am concerned about going overboard with any one management tool, whether fire, conservation grazing, or use of herbicides. Here in NYC WildMetro has been using hand removal of invasive species and small trees to save a small rare white oak/swamp white oak/hickory savanna and an adjacent grass/sedge/forb meadow. We do not plant, but two species of orchids have spontaneously appeared. Not always easy to get the required number of volunteers, but as we expand our efforts we feel grazing, rather than fire, might more closely model past local conditions. Suggestions welcome.

  7. Nancy Brennan says:

    How resistant to fire are the oak seedlings (as pictured above)? Or is it irrelevant in the grand scheme because more frequent fire creates a mosaic where some patches of seedlings will survive to maturity?

    • Kent Pfeiffer says:

      Oak seedlings will usually be top-killed by subsequent fires. However, most will survive and resprout in the following growing season. They can do this almost indefinitely. This is particularly true of bur and chinkapin oaks.

      Oak woodlands that are frequently burned typically have large numbers of “seedlings” that are not seedlings at all, but rather mult-year (even multi-decade) old trees that are maintained as a ground layer component of the plant community. All it takes at that point is a cessation of fire for a few years and you can get heavy recruitment of new trees into the woodland.

  8. Patrick Swanson says:

    Good and timely post, Chris. Two questions. First, are there any plans to burn parts of Platte River SP and areas down that way? I was hiking down there last year and noticed some fine bur oak stands and old cedars. Second, is there a list somewhere for contractors/CCBs willing to do prescribed burns on private lands in eastern NE? Thanks!

    • Chris Helzer says:

      Patrick, unfortunately, I can’t answer either of your questions. I’m hoping someone else (Kent?) can… I’ve not heard any plans to burn Platte River State Park, but that doesn’t mean anything.

      • Kent Pfeiffer says:

        I don’t have any information about Platte River State Park, unfortunately.

        For a variety of reasons, we don’t believe that contractors are an effective means of getting prescribed burns done on private lands. We’ve found that private landowners are fully capable of burning their own lands with just a little support. It’s primarily a matter of proper planning. That’s particularly true of woodland burns. They aren’t that hard to do, but require a fair amount of preparation and (usually) two or three days of baby sitting afterwards.

        • James McGee says:

          I agree with Kent that landowners should be able to conduct their own prescribed burns with the help of some neighbors. However, I think they should definitely consider taking a class on prescribed burning and helping with a few burns before leading their own burn. I also think they should get the consultation of a highly experienced burn boss on the morning before the burn. A quick phone call should be enough. They should also give their cell number to a burn boss so they can be notified if conditions change and they need to put the fire out.

          James

          • James McGee says:

            Instead of saying ‘consider taking a class on prescribed burning’ I should have said ‘definitely should take a class on prescribed burning.’ It is that important!

        • Patrick Swanson says:

          I do not necessarily disagree that the landowners can be capable, with some support, of burning their land, but as you point out, there are can be logistical challenges and considerable planning involved, especially if you don’t live/work on the property full time. There is also liability to be concerned about. Having a bonded and insured professional do it takes away some of the personal risk involved. Sure it costs more, but for some it might be worth the price. This may also be true if you’re older and don’t feel you have the stamina to manage a burn. This may apply to only a minority of situations, but I think some would be more comfortable using a contractor if they have the option.

  9. Sherry says:

    The folks at the Midwest Oak Woodland Fire Science Consortium will have more information on damage to timber by fire. See http://www.oakfirescience.com/workshops/.

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