Wildfire Recovery at The Niobrara Valley Preserve – Asking The Big Questions

Most of you are familiar with the wildfire that affected our Niobrara Valley Preserve this summer.  Well, we’re still trying to regain our footing after that event.  A great deal of time and money has already been spent on rebuilding and redesigning infrastructure (especially fences), but there’s still much to do.  In addition, the staff of the Preserve, along with a few of us from around the state, has taken this opportunity to do some deep thinking about what the Preserve can be in the future.  It’s an incredible place, and we want to be sure it lives up to its potential.  I’ll share more about that process as the picture becomes more clear.

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The Niobrara River continues to flow through the Preserve, but much of the landscape looks pretty different since the fire.  Open grassy slopes such as this one will recover quickly, but more wooded areas will come back much more slowly.

In the meantime, we’re also trying to learn what we can from the 2012 wildfire so that we and others can be more prepared the next time something like this happens.  I’ve been asked to help organize this effort, which is an intriguing task for me since most of our questions are about woodlands – not exactly my area of expertise.  Fortunately, I’ve had some great advice from others, particularly Dr. Dave Wedin at the University of Nebraska, who is also generously helping us line up researchers and funding.  Other advice has come from a wide spectrum of foresters, ecologists, and others, and I appreciate it all.

I was up at the Preserve last week for another bison roundup (the west herd this time) and had some time to poke around in the hills and think about our current list of research ideas.  I think we’re honing in on a few important research directions, but we still have some thinking to do about how to ask and answer the right questions.  Since we’re at a good point to get feedback from others, I thought I’d lay out some of what we’re thinking and see if any of you have suggestions for us to consider.  If nothing else, those of you who are familiar with the Preserve, and concerned about the impacts of the fire, can get an update on the situation and a feel for where we’re going next.

Yucca are starting to regrow across the burned portions of the Preserve.  Many show signs of being eaten - there's not much else green out there!

Yucca are starting to regrow across the burned portions of the Preserve. Many show signs of being browsed by deer and other wildlife – there’s not much else green out there!

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Wild rose is another of the plants regrowing in the burned areas.  These woody plants, perennial grasses, and sedges make up the bulk of the surviving plants.

Wild rose is another of the plants regrowing in the burned areas. These and other perennials, including grasses, sedges, and wildflowers, are most abundant in open areas without dense stands of trees.

Our primary research objective is to learn lessons that will help us and others adapt our pre- and post-wildfire management in the future.  It would certainly be interesting to simply document the way in which plant and animal communities recover from the fire, but that has been done elsewhere.  With very limited resources, we’ll spend a little effort documenting how the Niobrara Valley Preserve recovers from the fire (including the use of time-lapse and other photography) but we want to focus most of our effort on learning things that we and others can actually use down the road.

Impacts of Tree Density

The first thing we want to know is how the density of eastern red cedar and ponderosa pine trees affected the way the fire burned  and (more importantly) the way the areas beneath the trees will recover.  In addition to the perennial plants that survived the fire, much of the future plant community in our former pine woodland will depend upon the seed bank (the collection of seeds sitting in the soil, ready to germinate when given the chance).  Unfortunately, areas under dense tree stands are also the most vulnerable to soil erosion.  Especially on steep slopes, wind and water erosion can quickly remove both seed and soil, leaving very little to support plant community recovery.  Since there were few herbaceous (non-woody) plants under dense tree stands, there is little to hold the soil (and the precious seeds in it) from washing and blowing away.  If seeds and soil go, it’s going to be a very long time before anything grows in those places.

Soil erosion will probably be an issue on steep slopes and under formerly dense stands of trees.

Soil erosion will probably be an issue on steep slopes and under formerly dense stands of trees.

We hope to correlate the amount of soil erosion with tree density and slope, and see how those factors affect plant community recovery.  Ideally, we can combine our data with what others have learned elsewhere and develop recommendations for future management.  We want to know how densely can we allow trees to grow before the site becomes vulnerable to severe erosion in the aftermath of a potential wildfire.  Hopefully, that information can help managers decide how to prioritize tree thinning operations.

Much of the erosion that's occurred so far appears to be wind erosion.  A 70 mph wind storm got sand moving in some areas.

Much of the erosion that’s occurred so far appears to be wind erosion. A 70 mph wind storm really got sand moving in some areas.

On a related topic, we want to see how cedar and pine density affected the survival of bur oak trees.  It’s clear that we’re going to have varying degrees of recovery among the oaks growing on the lower slopes of our pine woodlands.  Some of the oaks have already re-sprouted from the base, but others haven’t.  Those others are either completely dead or waiting to resume growth from the tips of their branches next year.  What could we have done as land managers to prevent oak mortality by thinning the cedars and pines near those oaks?

Many of the bur oaks in the burned area are re-sprouting from the base.

This oak is re-sprouting from the base – it’s still alive, but has to start it’s growth over from the ground.

Aiding Recovery

We also have questions about how best to manage the recovery of burned sites.  Some people are advocating seeding burned areas to speed up the establishment of herbaceous and/or woody plants.  There are numerous concerns about this, including what kind of seed would be used and whether or not it would actually make any difference.  We certainly want to avoid introducing plant species that could cause more problems than they solve, but the bigger question is whether or not seeding will make a difference when the most problematic areas are those where soil erosion rates are high.  Putting seed in those erodible areas probably won’t do much good. However, while we and most of our neighbors will probably not be doing large-scale seeding, we might consider a few small-scale trials to test the idea.  We could broadcast seeds in a few trial plots and see if the plant community establishes differently within those plots than elsewhere.

Aside from any seeding efforts, the recovery of ponderosa pines in large swaths of burned woodland is likely going to be dependent upon seed coming from unburned areas.  Because of the size of burned areas, that could take a very long time.  Is it worth trying to speed up that recovery by planting small patches of ponderosa pines in various locations, with the idea that as they mature, those trees would be seed sources for nearby establishment – thus speeding overall woodland recovery?

A few mature ponderosa pines may have survived along the very top of the ridge north of the river.  If so, new pines may be able to spread from these pockets of survivors.

A few mature ponderosa pines may have survived along the very top of the ridge north of the river. If so, new pines may be able to spread from these pockets of survivors.

The answer to that question is related to another big question.  How do we manage these burned woodlands over the next couple of decades – especially in terms of prescribed fire?  At first glance, it might seem that we’ve had enough fire to last quite a while.  On the other hand, prescribed fire might be pretty important to help prevent cedars from coming right back in, and to give us some control over the overall recovery trajectory.  If we do employ prescribed fire, that’s going to impact where pines will be able to survive – including any we plant and those that come back on their own.

Very few pine cones can be found away from the very top of the ridge.  A few isolated exceptions like this might produce a few trees, but future prescribed fires may not allow many of those to mature.

Not many pine cones can be found away from the very top of the ridge. A few isolated exceptions like this might produce a few trees, but future prescribed fires may not allow many of those to mature.

Grassland recovery from the wildfire comes with questions too.  We have choices to make about whether to graze some of those drought and fire-stricken prairies immediately or to rest them for several months or longer first.  In our bison pastures, bison are never removed, so grazing resumed immediately after the fire.  We could build some exclosures to look at how immediate grazing impacts grassland production and species diversity.  In addition, we can manage our cattle pastures in several different ways and measure the results.  What we learn could help us and others make informed decisions after future wildfires.

The last big question we’re struggling with has to do with invasive species, especially in burned woodlands.  I’m not sure yet how to formulate a research question on this topic because we don’t yet know what kinds of invasives we’ll be dealing with.  Some plant species will be much quicker to colonize burned woodlands than others, but whether they will include truly invasive species – and which ones they might be – will be unknown until it happens.  We may just have to be ready to react as quickly as possible when we see what happens, and try to learn from our experience as we attempt to contain any invasions that occur.

We don't yet know what will be growing here in the coming years, but something will - and it will continue to be a beautiful and ecologically important place.

We don’t yet know what will be growing here in the coming years, but something will – and it will continue to be a beautiful and ecologically important place.

There are plenty of questions we could ask about the impacts of this wildfire.  We’re hoping to focus on those that might be the most useful to us and others when dealing with future wildfires.  We have our draft list, but would be happy to hear from anyone with suggestions of other questions we should consider or how we should prioritize among the questions we have.  Thanks for your help and support!

I'm smiling here, but as a prairie ecologist, I'm pretty far out of my element trying to help restore pine woodland.

I’m smiling here, but as a prairie ecologist, I’m pretty far out of my element trying to help restore pine woodland.

If you’re interested in contributing toward the recovery of the Niobrara Valley Preserve, please click here.

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Invasive Species Control Strategies – Avoiding the Whac-A-Mole Approach

Successfully controlling invasive species may be the most difficult (and important) part of prairie management.  There are few things more frustrating than the realization that, despite your best efforts, there are more (insert your species here) than there were the year before.  Because of the immensity of the challenge, it’s crucial to make your control efforts as efficient and effective as possible.

I sometimes think of invasive species control like the game “Whac-a-mole”.  It often feels like I hit one weed just to see another one pop up somewhere else.  Of course, there are two differences between Whac-a-mole and real invasive species control.  First, Whac-a-mole is a just game, and losing doesn’t mean anything.  Second, if Whac-a-mole was really like invasive species control, the moles would be multiplying and spreading across the county!

Every invasive species is different, and each requires its own specific control technique.  However, there are some broad strategies that can apply to almost every situation, and can increase the effectiveness of your attack.  The most important may be the “work from the edges” approach.  When faced with a major infestation of a particular weed (or any other kind of invasive) it’s often tempting to wade into the biggest thickest part of the infestation and start killing everything you can.  It makes you feel good and you can stand back and see that you’ve done something.  Unfortunately, that’s often the least efficient approach.  To continue the analogy, you’re just hitting the biggest and slowest mole, while letting the others continue to spread. 

Two examples of working from the edge to control invasive species. In example A, the invasive species is radiating outward from older larger populations. In example B, the species is moving in one direction. In both cases, initial control efforts should be targeted at the new small populations first.

Working from the edges of an infestation toward the middle, or toward the source, has a couple of advantages.  First, by focusing on the edges of a spreading infestation, you’re protecting the portions of your prairie that aren’t yet invaded.  Keeping those areas clean has to be the highest priority.  Second, newly-established plants are often the easiest to eliminate.  Young plants are less likely than older plants to have developed an extensive root system or a large seed bank.  Often, if you can successfully kill a new plant it stays dead (the mole doesn’t pop back up). 

Once you have the outlying plants taken care of, you can start working toward the center (or the source) of the infestation.  However, it’s usually more important to spend adequate time making sure every plant you kill stays dead than it is to move quickly to kill everything.  It may be more valuable to spend your time re-checking and re-treating the plants that you worked on last week than attacking new ones.  Even when you move to the next set of plants, be sure to continue checking up on the ones you’ve controlled in the past to make sure they don’t pop back up.  When you feel comfortable that you’ve got the outlying plants eliminated, a quick periodic sweep of those areas can be sufficient, and you can start enjoying the third advantage of working from the edges – now that you’ve got the edges taken care of, you can focus all of your energy on the main part of the infestation without constantly looking over your shoulder.

Crown vetch is an example of an invasive species that can be very difficult to control. Repeated herbicide treatments are usually necessary, especially on well-established populations. Crown vetch tends to grow in large clumps, so working from the edge can mean both starting on the edge of each clump as well as working on the smallest clumps first.

Working from the edges applies to invasive species control at multiple scales.  At the prairie scale, it applies to the control of a species with multiple populations across the prairie – (focus on the newer populations first).  Within a prairie, it can also apply to the attack of a single weed patch (get the edges under control so the patch doesn’t continue to grow).  In both cases, the first objective is to keep the problem from getting worse.  If that’s successful, the next objective is to start shrinking the existing population(s) without letting new ones get started.

In some cases, it can be worthwhile to do a quick-and-dirty attack on the more established portions of an infestation even while you’re working to systematically eliminate the plants at the edges.  For example, you may want to quickly mow through patches of older plants as they’re flowering, preventing them from producing seeds.  While you’re not killing those plants, you’re improving the likelihood that you’ll be able to contain the overall infestation by slowing its rate of spread.  (Just be sure to clean off the mower, your shoes, or anything else that might otherwise spread the seeds anyway!)  A similar strategy can be used when only a subset of the older population is reproducing.  When controlling invasive trees, for example, younger trees (or male trees) may not be producing seeds.  If only a small percentage of the trees are reproducing, taking the time to find and kill those may be worth the effort, even if they’re in the middle of the infestation.  Then you can return to the edges, knowing that your chances of containment have improved.

While it is a native species, eastern red cedar can be an aggressive plant in prairies, especially in the absence of regular fire. Focusing early control efforts on mature female trees that are producing berries can be a good way to help slow the spread of trees while you work to contain the overall infestation.

Here’s a real example from one of our prairies:  We’re fighting Canada thistle in a large floodplain prairie (well over 1,000 acres).  The worst part of the infestation is in a wet and shrubby area where control (and access) is very difficult.  The remainder of the property has widely scattered patches of thistles.  We’re able to spot-spray all of those scattered populations each year, and have been slowly reducing the number and size of those patches.  However, we don’t yet have the resources to hit the scattered patches AND attack the really bad area – especially because the time window for effective control is relatively short each season.  We do what we can to hit the plants near the edges of that main population to help keep it from spreading, but we’re mainly trying to keep the rest of the property from being overrun.  Ideally, we’d be mowing the flowering heads off of the plants in the large population, but we can’t get equipment into that area.  As we continue to eliminate the small scattered populations, we’ll have more time to start working into the large population and begin shrinking it a little each year.  It’s not the best situation, but it’s the real situation, and we’re trying to make the best of it.

In some cases, an effective attack – with consistent follow-up – can eliminate an invasive species from a prairie, and you might just have to conduct an annual patrol to ensure that it’s still gone.  In other cases, containment of the worst area(s) may be the best case scenario, and you may have to plan to conduct perennial search-and-destroy missions to prevent new populations from starting.  In still other cases, an invasive species may be so entrenched across an entire prairie that you just have to try to suppress its vigor and allow as many other species to survive as possible.  And, of course, you’re likely to have all three of these situations happening simultaneously in the same prairie, so it’s important to have clear objectives and strategies for each invasive species you’re dealing with.

Regardless of the invasive species or its level of infestation, an efficient and effective attack strategy is critically important.  Not only will it improve your chances of success, it will also help maintain your sanity – it’s much less frustrating to know that you’re making gradual progress in your control than to attack sporadically, only to see plants or populations pop back up behind you. 

Makes you wonder why Whac-a-mole was such a popular game, doesn’t it?