CLB Journal

Summer 2009

After the Rain a Good Fire

For many people the word "fire" has an alarming ring to it. We've all been reminded by Smokey the Bear of the danger of dropping a lighted match in the forest. But for reasons I will explain below, a carefully managed fire is a necessary step in ranch landscape restoration. Here is the protocol we follow on the C.L. Browning Ranch. It may be useful for other ranchers whose properties, like ours, are overgrown with Ashe juniper Juniperus ashei a.k.a. cedar.

In order to return to the ranch the savanna grasslands that once characterized the central Texas landscape, we are mechanically removing the Ashe juniper using a Bobcat skid-steer with hydraulic shear that cuts the tree off at the ground level. We opted for this method over a bulldozer because we wanted to leave the roots in place to help anchor the soil. We also prefer to leave the fallen tree in situ for a period of two to three years. I have seen from experience that this stabilizes the soil, which reduces erosion and provides favorable conditions for the collection and germination of grass seed. We call this treatment a juniper blanket, referring to to the widespread coverage of the landscape with cut juniper.

Our Bobcat skid-steer being used to cut down an Ashe juniper at the ground level with a tree shear.

But the blanket of brush, which I must admit is something of an eyesore, cannot be left to lie on the ground indefinitely. After all, what we are aiming for is a rolling Hill Country landscape of native grasses that has optimum value, both as scenery and as a resource for wildlife and cattle. So when we feel the time is ripe, we will mound the juniper into piles of approximately 1,000 square feet by no more than 10 feet high and wait for the right conditions of wind an humidity to light a fire that will eliminate the brushy debris with due caution and respect for the environment.

An example of the unsightly yet very beneficial juniper blanket treatment

For those who remain skeptical about lighting this kind of fire, I'd like to go on record as saying that I consider fire to be the most important tool available today for land managers. Whether it be in the form of a rangeland prescribed burn intended to address a specific problem (woody species encroachment), or a brush-pile burn for practical purposed (disposing of juniper), I like fire as a management treatment because it, along with grazing and drought, is one of the driving forces that creates and maintains grasslands worldwide.

Fire is a tool that can be used to dispose of cut brush or control woody and invasive species in grasslands (shown above)

For example, the Great Plains grasslands are located on the dry side of the Rocky Mountains and have a climate of perpetual drought punctuated by periodic floods. These arid conditions provide an advantage to grasses over woody species because the grasses require less water. However, competition for moisture alone will not stop the encroachment of woody species into the grasslands. Among the several benefits that the landscape receives from fire, such as a change in the nutrient cycle of the soil, enhanced seed germination, and the creation of patchy microhabitats across the area of the burn, the control of woody species is most important. Fire provides the maintenance function that drought alone cannot. For us in central Texas, grasslands maintained by fire can increase the absorption of rainfall (ground water recharge) and decrease the rates of erosion. This helps to refill the aquifers that we all depend upon for drinking water.

It is believed that most of the grasslands in eastern North America exist today because of the Native Americans' frequent use of fire. Native Americans used fire for numerous reasons, such as crop management, pest control, and to drive game while hunting. Burning off the dead grass enabled the growth of new grass, which would ensure that the bison would return to these areas again and again. The bison and other large herbivores, such as elephants, mammoths, and camels (all of them no longer naturally present in North America), also helped to maintain the open grasslands by consuming woody species.

Historically, the Great Plains grasslands of North America experienced widespread fire on an average of once every three to five years. By the time the Anglo settlers arrived on the Great Plains grasslands, several of the large herbivores had gone extinct, and the colonists' efforts to rid the region of Native Americans was accomplished by eliminating the last remaining large herbivore, the bison. Livestock were confined into fenced-off pastures, initiating the process of overgrazing. Additionally, laws intended to eliminate the use of fire on the range were enacted. These actions altered the cycles and control of vegetation succession, resulting in the encroachment into grasslands of woody species that quickly outcompeted the grasses for water and nutrients. It has been estimated that the elimination of periodic fire leads to a loss of original prairie species at a rate of about 1% per year. So if we are going to attempt to restore the grasslands on the Browning Ranch, we must do so with fire as our main strategy.

Woody species control in action

This brings us back to burning piles of cut Ashe juniper. A day with over an inch of rainfall offered ideal conditions for our most recent burn. This was the moment we had been waiting for. We could see that there was enough ground moisture for us to go ahead and burn a large brush pile. Getting rid of this pile was a top priority because it was located beside a trail we are creating to highlight the special ecological, cultural, and aesthetic attributes of the ranch. We experienced intermittent rain showers during the burn that helped to reduce the wildfire threat and clear the airborne particulates from the atmosphere.

The start of the burn at 9:30 a.m.

Ivan the Vizsla, a.k.a. Ranch Biologist at 11:00 a.m.

The Smoldering pile at 1:00 p.m.

Scott ensuring he gets a good night's rest by scraping the embers along the perimeter back into the site to prevent the fire from crawling out overnight.

There is an inherent problem with burning piles of brush besides air quality and wildfire concerns. In most cases, a vegetation-free scar will exist after the burn and will be slow to recover, if at all. We initially thought this was due to the cooking of the soil organisms, rendering the site micro-biologically sterile. But when we conducted an experiment with the Lady Bird Johnson Wildflower Center, we found that the burn process did not sterilize the soil. Instead, it only killed off the seed bank. This was fantastic news because it means that the burn scar can be eliminated by reseeding the site. So after the site has cooled down, we will reshuffle the soil with the tractor and disk harrow to a depth of about three to four inches. We will then use the tractor and cultipacker, a rolling implement that textures the soil, to pack down smooth the surface. After this step we will add grass see, and then we'll make one more round with the cultipacker in order to embed the seed into the soil. This process erases the burn scar so well that I doubt I could find more than half of the hundred-plus burn sites that we have treated in this manner. Most importantly, the whole process produces a patchwork of seed islands that will drift out into the surrounding landscape, all the while providing excellent forage and nesting resources for wildlife and reducing soil erosion during heavy rain events.

Here is a picture of our cultipacker in action. Notice the grooves it makes on the soil surface, which are the perfect depth for sowing grass seed.

At Site #1, we added seed after the burn. New growth appear quickly, as seen here in this picture taken three months after the fire.

Site #10, where we did not add seed after the burn, was still barren three months after the fire.

Site #1 again, taken in 2007, three years after burning and reseeding.

And here's Site #10 again, taken in 2007, three years after burning.

Next entry, I will talk about droughts and their impact on the ecology and society. I look forward to bringing more pictures and discussions about our burn site revegetation program and other Browning Ranch activities in the near future.