From the Ashes

Last Friday, I wandered through the small prairie we burned back on March 10.  Even though it is still very early spring, there were already a number of prairie plants popping out of the ground.  I posted photos of this site right after the fire was completed.  Today, I’m posting some photos taken 10 days later at the same site, along with some discussion of the impacts and effectiveness of prescribed prairie fires.

Purple poppy mallow (Calliroe involucrata)

Purple poppy mallow (Callirhoe involucrata) begins its new year of growth.

Most prairie plants grow from belowground buds, making them much less vulnerable to fire than trees and shrubs, which start their new growth above ground – from buds at the tips of branches.  When fire burns woody plants, those aerial buds and living tissue are destroyed, stressing the plants and forcing them to start over from ground level.  However, fire (at least during the dormant season) simply burns up the old stems and leaves of non-woody prairie plants, causing no injury.  Instead removing those dead stems helps stimulate growth in the coming season, especially via increased sunlight, which warms the ground and is available to new shoots as they first emerge.

Scribner's panicum (Panicum oligosanthes), a native cool-season grass.

Scribner’s panicum (Panicum oligosanthes), a native cool-season grass.  In this photo, you can see that the tips of the grass leaves had just started to grow when the fire came through ten days earlier.  Since the leaves grow from the base, those burned tips don’t impede plant growth.

Increased sunlight hitting the ground has helped the small area we burned on March 10 green up much faster than unburned prairie nearby.  Our main objective for the fire was to remove thatch in order to improve the effectiveness of planned herbicide treatment/re-seeding of some smooth brome patches within the small prairie.  The brome is responding very strongly to the fire, and its rapid growth (and the absence of thatch to intercept spray droplets) will make the grass more susceptible to our herbicide treatment.  However, since many other plants are also popping up, we’ll carefully spray only the thickest patches of brome where no other species are growing.

Green sage (Artemisia campestre)

Green sage (Artemisia campestre) growing next to its old stem from last year.

Prescribed fire can be a useful tool when trying to temporarily flip the balance of power from cool-season invasive grasses (smooth brome, Kentucky bluegrass, etc.) to native warm-season grasses (big bluestem, indiangrass, etc.).  However, timing is critically important.  A dormant season or early spring fire is actually counterproductive unless it is followed by herbicide treatment, mowing or grazing.  Those early fires stimulate the growth of cool-season plants – including smooth brome and Kentucky bluegrass – giving them a big advantage over later-season plants which won’t start growth until late April or early May.  By the time those warm-season plants start growing, the early plants will have had a month or more to extract soil moisture and nutrients, and will be big enough to dominate competition for light and root space.

If we’d wanted to suppress smooth brome solely with fire (and not follow up with herbicide), we would have waited until late April or early May to burn.  That late season burn would have stressed the actively-growing brome and bluegrass and provided direct sunlight to freshly emerging shoots of big bluestem and other warm-season grasses.  More often, we combine periodic fire and grazing to suppress brome and bluegrass and facilitate greater plant diversity.

Here's one of the grasses we would like not to see coming back after a fire - Kentucky bluegrass (Poa pratensis).

Along with smooth brome (Bromus inermis), Kentucky bluegrass (Poa pratensis) also responded well to the fire.  This particular plant will likely have a very good year, but the brome and bluegrass in the thicker patches of this prairie will be sprayed with glyphosate herbicide and re-seeded.

The regrowth of prairie plants after fire can seem almost magical.  Fire is absolutely an important natural process and a very useful tool for prairie managers.  However, prescribed fire is not magic, and doesn’t automatically lead to better prairies.  As with any tool, fire has to be applied thoughtfully (and carefully!) in order to meet objectives.

The timing of fire dramatically impacts the way prairie plant communities respond.  Early spring, late spring, summer, and fall fires each have different effects on plants, and those effects are also influenced by soil moisture, the presence/absence of grazers, and many other factors.  Prescribed fire can also have serious impacts on some animals, even during the dormant season.  Many invertebrates, for example, overwinter in the aboveground plant stems or thatch, making them very vulnerable to fire. It’s important not to burn an entire prairie at once – especially if that prairie is isolated from other grasslands.

I'm not sure what species of wildflower this is.

I’m not sure what species of wildflower this is but I’m looking forward to finding out as it gets bigger!

Fire plays many critical roles in prairie ecology – suppressing woody plants, removing thatch, stimulating microbial activity, aiding in nutrient cycling, and more.  However, while fire is important and its effects are both useful and aesthetically pleasing, it is not automatically positive.  Safe use of prescribed fire requires training, experience, and caution.  The effective use of fire requires clear objectives and careful planning that ensures those objectives will be met.

As I’ve discussed before, the actual process of conducting a fire can be very stressful.  However, once the smoke clears and I can relax, its easy to appreciate both the beauty and ecological benefits of prairie fires.  The emergence of bright green prairie plants through black ash is one of my favorite sights, and I love watching plant and animal communities respond and adapt to changing habitat conditions.

In prairies, rising from the ashes is more than a metaphor – it’s a way of life.

 

Continuing Wildfire Recovery at the Niobrara Valley Preserve

When I was at the Niobrara Valley Preserve a couple weeks ago, I spent some time exploring the area north of the river where the 2012 wildfire ripped through oak savanna and ponderosa pine woodland.  As discussed in earlier posts, the density of trees, especially eastern redcedar, fueled a fire that killed nearly every pine and cedar in the 3000 acres of Preserve land on the north side of the river.  Most oaks and other decidous trees were topkilled, but many resprouted within a few weeks of the fire.  I have been following the regrowth and recovery of this part of the Preserve with great interest, and trying to help the Preserve staff as they think about how to manage the area in the future.

Here is a series of photos from an uphill hike I took on September 18.  The photos are roughly in order of elevation, starting at the river road (just above the floodplain) and proceeding upslope to the ridgetop at the north edge of the valley.

Hemp and marestail

On the first slopes above the river road, hemp (Cannabis) and marestail (Conyza) dominate the understory of a woodland that now consists mainly of skeletons of eastern redcedar and oak trees.  Most of the oaks have resprouts from their bases, however, and a few still have live branches up high.

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Marestail and cedar skeletons

The abundance of marestail (a native pioneering species) is especially interesting to me because it’s the same species that usually dominates two-year-old prairie plantings.  This is the role it plays in ecosystems, and it plays it well.  It’s difficult to see very much below the marestail, but when I looked closely, I found scattered grasses, sedges, and wildflowers – a good sign of future recovery.

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ragweed

As I walked higher and got into the prairie-covered slopes, ragweed (Ambrosia) replaced marestail as the visually dominant plant in the formerly shaded areas beneath cedar trees.  The ragweed is playing the same role as the marestail – quickly filling in the open space until a more permanent plant community establishes.  That community should move in pretty quickly in cases like that shown in this photo, in which a cedar tree is surrounded by prairie.

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prairie

Higher up the slope, large areas of prairie had not been encroached upon by cedars, and recovery after the fire was just as predicted – quick and easy.  The vegetation was still a little thin, but that was more of an aftereffect of the 2012 drought than of the fire.  In this image you can see the scattered cedars further downslope (such as the one featured in the previous photo).

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Oaks

Almost every bur oak tree I saw was vigorously resprouting from the base.  Those numerous stems should thin themselves down to three or four major trunks over the next decade or so.  Some of the branches were already 6-8 feet high, so recovery is proceeding quickly.  These oaks were growing along the edge of one of many steep draws scattered along the north side of the river.  As I was wading through 3-4 foot tall marestail, I couldn’t help but wonder if that dense growth and the presence of mountain lions in the area explained the near absence of deer browsing on the oak sprouts (Ecology of Fear).   I don’t know if the deer felt it, but I sure had moments of discomfort, knowing that if a lion was hiding in the weeds nearby, the steep slopes and thick vegetation would make escape nearly impossible.  It made my hike a little more exciting, but I didn’t stay down in those draws very long…

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Sedges

I was surprised and pleased to see numerous examples of large sedge patches growing under the marestail forest, especially on the steeper portions of draws.  I don’t remember seeing many sedges last year, so either I missed them or they are expanding rapidly.  Either way, they will sure help stabilize those slopes as other plants move in to join them, and they’ll also help carry fire when we restart fire management of the area.

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Pine woodland

High on the slopes, where ponderosa pine and eastern redcedar had dominated just a few years ago, the scenery was every bit as spectacular as it had been before the fire – just different.  Marestail was abundant here too, but there was quite a bit of grass and wildflower cover as well, and several shrub species were flourishing, including smooth and skunkbush sumac, chokecherry, snowberry and others.  Despite the density of scorched tree trunks, the overall feel of the slopes was not one of death and destruction, but rather of abundant life.

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Ridge top

Even the very steep erodible slopes at the very edge of the ridge top were full of previously established perennial wildflowers and shrubs, as well as colonizing annuals.

I came down the slope after my walk with a great feeling of optimism.  My greatest worries about this area of the preserve had been that

1) Invasive plants would fill the slopes before the native vegetation could recover, and we’d be faced with the difficult challenge of attacking those invasives in difficult terrain.

2) Numerous eastern redcedar trees would colonize the slopes before there was enough vegetation to carry prescribed fires to knock those cedars back.

3) Soil erosion would be so severe that the seed bank needed to reestablish the native plant community would wash down the slope, along with the topsoil those plants needed to grow.

None of those three have occurred – or at least to the extent I feared they might.  There has been some erosion, but much less than I anticipated, and it doesn’t seem to be affecting vegetation recovery much.  I haven’t seen any truly invasive plants yet – which doesn’t mean they aren’t there, but they sure aren’t roaring in.  Finally, the recovery of the vegetation has been fast enough that we should be able to start running prescribed fires up the slopes within the next few years.  I didn’t see any little cedar trees on my walk, and while I’m sure there are a few around, the abundance is much less than I feared, and our ability to use prescribed fire should make it fairly easy to control them, except on the steepest slopes.

Most of all, the beauty of the Niobrara Valley has survived the wildfire.  The pines are gone from some parts of the valley, but are still doing well in other areas nearby, including other parts of the Niobrara Valley Preserve.  Whether or not (or when) they’ll return to the site of the 2012 fire is still an open question.  Regardless, there is abundant life on the slopes north of the river.  Just because those slopes will be dominated by different species than before doesn’t change the scenic or ecological value of the site.  It’s still one of my favorite places on earth.