2014 Woodland Burning at the Rulo Bluffs Preserve

I made a trip down to our Rulo Bluffs Preserve last week.  I wanted to get down and see the results of the prescribed fire we conducted earlier this spring.  We’re in a restoration mode at the site, trying to re-open the woodland and increase the amount of light hitting the ground.  The day we burned the site this spring, the relative humidity was very low, so the fire was a little hotter and burned a higher percentage of the unit than we’d seen  in previous burns.  Killing small trees and brush with a nice hot fire was good for our objective.  On the other hand, I worried a little that we might have cooked some of the bigger trees we wanted to keep.

Another panorama showing burned and unburned.  This time, the burned area is to the left and the unburned to the right.

A panorama (four photos merged together) along the edge of the burn unit. The area burned this spring is to the left and the unburned is to the right.

Overall, I was very pleased with what I saw last week.  The fire, combined with some recent “hack-and-squirt” herbicide treatments on smaller trees has done a great job of increasing the amount of light hitting the ground.  At the same time, the majority of larger trees were still alive and leafing out, maintaining a fairly complete canopy – but one that allows for mottled light to hit the ground throughout the day.  We hope to continue annual, or at least very frequent, fires for the next several years to set the woodland back on the trajectory we want.  Then we may back off on the fire frequency a little.  Eventual success will be measured by whether we see an increased abundance of wildflowers, sedges, and grasses on the woodland floor, and – more importantly – regeneration of oak trees, which is crucial for the survival of the woodland itself.

Here are some photos of this year’s spring fire, as well as what I found during my walk through the site last week.

Firebreaks for the fire were mostly created by using a power leaf blower to clear out a narrow trail.  Nelson Winkel is shown here making a final pass around the breaks of the 100 acre burn unit.

Firebreaks for the fire were mostly created by using a power leaf blower to clear out a narrow trail. Nelson Winkel is shown here making a final pass around the breaks of the 100 acre burn unit.  Other members of the crew followed behind, raking out any other debris that needed to be cleared from the breaks.

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Anne Stine lights down a slope during the fire.

Anne Stine lights down a slope during the fire.

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The fire burned a little more intensively than most woodland burns we've done at the site, but nothing like a prairie fire - though it burned pretty hot up some of the steeper draws, where leaf litter had accumulated and slopes helped drive the fire.

The fire burned a little more intensively than most woodland burns we’ve done at the site, but nothing like a prairie fire – though it got pretty hot  as it went up some of the steeper draws where leaf litter had accumulated and slopes helped drive the fire.  Crew members patrolled the narrow breaks constantly during the burn, checking the fire, raking leaves and sticks in, and looking for dead trees burning along the edge of the unit that might need to be taken down.

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This multi-photo panorama shows the largest of the prairies at Rulo Bluffs, along with some of the woodland.  The photo(s) were taken from our neighbor's pasture.

This stitched multi-photo panorama shows the largest of the prairies at Rulo Bluffs, along with some of the woodland. The photo(s) were taken from our neighbor’s pasture during the fire.

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This area

This area burned fairly completely but there were still small unburned patches here and there.

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We were able to use ATVs to access some portions of the firebreaks, but others were too steep and/or narrow, and were accessible only on foot.

We were able to use ATVs to access some portions of the firebreaks, but others were too steep and/or narrow, and were accessible only on foot.

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This panorama shows approximately the same area as Anne is shown lighting above.  The right half of the photo was burned, the left was not.  Note how much more open the burned area is.

This panorama shows approximately the same area as Anne was lighting in the earlier photo. The right half of this image was burned, the left was not. Note how much more open the burned area is.

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Burned on the left, unburned on the right.

Burned on the left, unburned on the right.  Wood nettles seem to be having a banner year in both burned and unburned areas.  I’m not sure why that is.

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More wood nettles (and other plants) - this time on a southeast-facing slope that burned pretty hot.  Note the dead (or at least top-killed) small diameter trees.

More wood nettles (and other plants) – this time on a southeast-facing slope that burned pretty hot. Note the dead (or at least top-killed) small diameter trees.

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Wood nettles were most abundant on lower slopes.  Higher up, mayapples, sanicle, and other plants were more common.  Here, mayapples grow with little company.  That will change as the plant community adjusts to an environment with more light availability.

Wood nettles were most abundant on lower slopes. Higher up, mayapples, sanicle, and other plants were more common. Here, mayapples grow with little company. That will change as the plant community adjusts to an environment with more light availability.  The fire wiped out this year’s crop of garlic mustard.  Hopefully, maintaining a high fire frequency in coming years will help suppress that invader.

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Here is a south-facing wooded slope that has a lot of bare ground.  Again, this will change over time.  Here, many of the small trees were dead prior to the fire (from the hack-and-squirt treatment.

Here is a south-facing wooded slope with a lot of bare ground. Again, this will change over time as light-loving plants colonize and spread. Here, many of the small trees were dead prior to the fire (from the hack-and-squirt treatment.

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Columbine was blooming on north-facing slopes - mainly in places the fire skipped.

Columbine was blooming on north-facing slopes – mainly in places the fire skipped.

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A close-up of columbine.

A close-up of columbine.

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Yellow ladies slipper orchids seemed to weather the fire just fine.  Of four populations we marked with GPS last year, I found all four and three of them were blooming.  All had been in areas that burned.

Yellow ladies slipper orchids seemed to weather the fire just fine. I found all four of the plants we marked with GPS last year, and three of them were blooming. All  four were in areas that burned.

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The prairie (left) and neighbor's pasture (right) shown in the earlier photo during the fire.  the prairie greened up very nicely, and the numerous dogwoods were knocked back (temporarily).

Here is the same prairie (left) and neighbor’s pasture (right) shown in an earlier photo (during the fire). The prairie looks vibrant, and numerous dogwoods were knocked back (at least temporarily).

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Small prairie ridges were greening up very nicely.  Most of the bur and black oaks in those  areas appeared to escape the fire with little or no injury.

The  small prairie ridges scattered across the preserve are greening up very nicely.  Most of the bur and black oaks in those areas appeared to escape the fire with little or no injury.

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This beautiful spreading bur oak was clearly thriving - as was the prairie around it.

This beautiful spreading bur oak was clearly thriving – as were the prairie plants around it.  The top-killed shrubs will regrow, but frequent fires (and maybe some basal herbicide treatments) should keep them at bay.

 

 

 

Blowing Against the Wind?

As I mentioned last week, I recently spent a couple days helping our land manager, Nelson Winkel, pull garlic mustard at our Rulo Bluffs Preserve in southeast Nebraska.  The invasive species has just started to invade our property within the last several years.  We’ve heard stories from colleagues in other places about beautiful woodland plant communities turning into monocultures of garlic mustard within a relatively short time period.  We’d sure like to keep that from happening at our Preserve.

So, we pulled garlic mustard plants.  A lot of them.  On the first day, I figured we pulled at least 25,000 plants.  That’s a very conservative estimate.  The second day was longer, but we did more searching and less pulling.  This wasn’t the first trip to pull either, so we were just trying to get what was leftover from the previous efforts.

Nelson Winkel, showing off one patch's worth of pulled garlic mustard plants.  The Nature Conservancy's Rulo Bluffs Preserve - Nebraska.

Nelson Winkel, showing off one patch’s worth of pulled garlic mustard plants. The Nature Conservancy’s Rulo Bluffs Preserve – Nebraska.

The Rulo Bluffs Preserve is 444 acres.  Hand-pulling weeds doesn’t seem like a very sustainable strategy for invasive species control at that scale.  In fact, it’s downright depressing because we pull more plants from more locations every year.  We’re clearly not winning.  So why bother?

It’s a good question, with several answers.  The first answer is that we’ve got some ideas for increasing our effectiveness.  Nelson and I talked as we worked about how we might put together a small army of volunteers to come help us pull each spring.  The big challenges are that the site is far from population centers (more than two hours from Lincoln and Omaha), has difficult terrain to hike in, and garlic mustard doesn’t bloom at exactly the same time each year, so we’d have to schedule work days on fairly short notice.  On the other hand, I think there are people who’d be glad to help, and it is a beautiful place to work in the spring time – lots of warblers and other birds above, and plenty of woodland wildflowers below.

In addition to finding more people to help hand pull, we hope to decrease the number of plants we need to pull in the bigger, more established, patches by doing some herbicide work in the late winter.  Garlic mustard is a winter annual or biennial which germinates in one season, overwinters as a rosette (a few leaves, low to the ground), and then flowers in the late spring of the next year.  Our colleagues in more eastern states have been dealing with garlic mustard longer than we have, and have had luck spraying the rosettes with Glyphosate herbicide on warm February days.  Spraying in the winter works well because there are very few other woodland plants that are green (and thus susceptible to Glyphosate) in February.  They don’t usually spray in the early winter because many rosettes die on their own over the winter, and by waiting until February, they can focus only on those most likely to bloom in the coming year.  Nelson was marking the bigger patches we found with a GPS unit so he can find them next winter and try the spraying technique.

Small patches of garlic mustard such as this one might eventually be eliminated by hand-pulling.

Small patches of garlic mustard such as this one might eventually be eliminated by hand-pulling – especially if we find and treat them every year.  Larger patches are much more problematic.

The second reason we’re still trying to suppress garlic mustard is that I hope we can buy some time until better control options become available.  There has been some work to develop a biocontrol technique (using insects from the native range of garlic mustard), for example, and if something like that turns out to be effective, I want to be sure we still have some woodland left to save.  Unfortunately, I’m hearing that biocontrol development has stalled at the moment.  Apparently, in at least some places, people are seeing garlic mustard populations decline steeply on their own – as if the plants are outcompeting themselves and self-thinning.  That could be great news, but only if the native plant community rebounds as the garlic mustard declines, and I haven’t been able to find anyone who can tell me whether or not that’s the case.  I sure hope it is, but I’d feel better if the biocontrol folks kept forging ahead on the development of that control option anyway.  Regardless, I’m holding out hope that either garlic mustard will turn out to be a temporary nuisance (seems unlikely?) or that biocontrol or better control options will be developed in the next several years.  I could be naive, but at least it gives us something positive to think about while we’re pulling up thousands of garlic mustard plants…

While we look for better control options, we’re also trying to change the playing field for plant competition at Rulo Bluffs and give garlic mustard less of an advantage.  With considerable help from Kent Pfeiffer of Northern Prairies Land Trust, and funding from the Nebraska Game and Parks Commission and others, we’ve been trying to ramp up our stewardship work during the last several years.  We’ve not done as much burning as we’d like to, but are earnestly trying to change that.  Last fall, a contractor did some “hack-and-squirt” herbicide treatment to kill many of the smaller understory trees that are shading out the herbaceous plants on the ground.  We’ve also been doing mechanical shredding of brush on ridgetops to help the grassland, savanna, and open woodland plants there.  All of this work is aimed at getting more light to the ground, which should stimulate increased oak regneration and a stronger, more diverse, herbaceous community on the woodland floor.  In addition, we hope that increased light will put shade-loving garlic mustard at a disadvantage, at least in some parts of the woodland.  From talking with others around the country, they’ve seen mixed results from similar work.  I guess since we want that light on the ground anyway, we’re going to forge ahead – and hope we don’t make things worse.

Jack-in-the-pulpit is one of many woodland flower species that help make the Rulo Bluffs Preserve unique and valuable.

Jack-in-the-pulpit is one of many woodland flower species that help make the Rulo Bluffs Preserve unique and valuable.

Finally, we’re pulling garlic mustard because the Rulo Bluffs Preserve is worth the effort.  It’s one of the few remaining high-quality oak woodlands in Nebraska, and hosts a wide diversity of plant and animal species – many living at the edge of their geographic range.  In addition to lots of mayapples, jack-in-the-pulpit plants, and woodland phlox, we also found two orchid species blooming last week – the showy orchid and the yellow lady’s slipper orchid.  We walked around beneath eastern deciduous tree species such as chinkapin oak, black oak, and Ohio buckeye.  Several animal species at the preserve, including zebra swallowtails, timber rattlesnakes, and southern flying squirrels, are only found on the very eastern edge of Nebraska.  While some of those species are common to the east of us, it is probably important to protect their genetic diversity by maintaining populations across their entire range.  That should allow the species to better adapt and survive in changing conditions over time.

Genetic and biological diversity aside, the Rulo Bluffs Preserve is also important because it’s a beautiful place.  We need to keep some aesthetically-pleasing natural areas around for people to enjoy.  Despite our aching backs, Nelson and I had a great time exploring the preserve last week, marveling at warblers, flowers, velvet mites, and other wonders.  It’s possible that we’ll invest a tremendous amount of time and money into stewardship and restoration at the Rulo Bluffs Preserve over the next several years and still lose out to garlic mustard.  There are plenty of examples of that happening elsewhere.  I guess we’re not ready to concede the battle, however – there’s too much at stake.