Posted Under: Habitat Management | January 14
Wildfires Natural, Prescribed Fire is Planned
“Out of sight, out of mind”, I think we all have heard that one. I wish remembering was as easy as forgetting! Digestion of food, the battery in your phone or light bulb in the house are all chemical processes or reactions that when working properly, do not draw attention. The battery dies, bulb burns out or the stomach aches, we are suddenly imposed with actions that may be sidled with a groan. These reactions and many others exist in our environment; and we have become dependent upon many of them to contribute to our success.
The same can be said for fire, a chemical reaction that exists when the appropriate components of fuel, heat and oxygen are present. I think we all can agree, not only does fire contribute to heat in a camp stove, grill or oven but the potential for fire is present in any landscape with the appropriate resources, and fire has played significant evolutionary roles in the development of flora and fauna.
As humans we quantify associations, relationships and change over time to communicate. Our first descriptions of the landscape here in central Texas vary somewhat. Tall grass prairies, live oak savannahs, burned prairie or dense cedar brush thickets are depicted in historical accounts. Although describing an ecosystem is difficult we have done so in many ways throughout our history. For example, grass belly high on a cow, abundant game, available firewood or sight distance are measurements that present the reader with a mental image of the historical landscape.
When describing an ecological system or ecosystem, one thing is certain — change. Change is constantly occurring, driven by soils, rainfall and disturbances. Of the disturbances imposed on the landscape, the most dramatic have been from humans. European settlement accounts in the mid 1800’s depict not only the landscape but a way of life. Cattle, sheep, goats, horses, donkeys, mules and fence were increased sharply with settlement practices.
Before Prescribed Burning
Fire on the landscape, once broad, extensive and frequent was considered disastrous thus controlled. The landscape at that period and time was a product of very powerful forces and a shift away from a fire dominated landscape began to produce a very different product in a short period of time. Heavy continuous grazing brought on significant changes in the historical disturbances governing the flora and fauna of the landscape, yielding a much different product than described in historical accounts. We were suddenly posed with a problem and fought the change in landscape with expensive mechanical methods to reduce an intense assault of plants selected by our actions, brush.
By the 1970’s the components of fire, relationships to weather and the application of fire came under question. By understanding the central components of fire (fuel, heat and oxygen) and its behavior, fire began to demonstrate a tameness with perceived benefit. Humidity in the air, moisture in fuels and wind speed were identified as factors directly related to the intensity of fire. Prescribing fire soon became a rule of thumb.
Although the goals of fire are different today, Native Americans demonstrated the first use of “fire prescriptions”. Whether to flush out game, attract game or restore a landscape, the common goal then and now is to use fire with a perceived benefit. Prescribed burning under a set of predetermined conditions to achieve a goal is a prescribed burn. In wildlife management, goals revolve around habitat and the primary contributor to habitat is plants.
Prescribed Burning Examined
Plants have a unique way of organizing themselves: forbs (annual plants), herbaceous perennials (mostly grasses) and browse or woody plants. Dormant grasses are our main fuel for fire on the landscape, gaining and losing moisture in relation to the humidity in the air. Dormant grass is usually 1 hour behind the relative humidity in the air and is subject to change as weather changes while larger fuels retain moisture for much longer periods. In other words, moisture is obtained and lost at slower rates as the fuel size increases, which affects the behavior of fire. Therefore, selection of the time of year, grazing practices and climatic conditions (drought, etc.) determine the behavior of fire, results and product from a prescription.
For example: Prescribed burning in January under a set of environmental conditions of 30 percent humidity, wind speeds less than 10 mph and dormant grass at greater than 1,200 lbs per acre will have an expectant yield of 80 percent kill on ashe juniper less than 4 feet tall . Furthermore, large trees (remember the moisture factor) will not be harmed. However, prescriptions can easily change to consume smaller woody plants.
For example: A prescription within 20-25 percent humidity and wind speeds of 5 mph can effectively burn through shin oak and live oak mottes. Fire prescriptions can range from simply reducing fuel loads to prevent devastating wildfires to fertilizing range sites to increase plant vigor from ash.
These are a few of many examples of fire prescriptions. Regardless of the prescription, the bottom line is that plants and plant communities have dealt with and adapted to fire and that this manipulation by fire causes change. What type of change fits into your habitat management goals?
More on Prescribed Fire
We have come full circle here, it really is easy to forget just how powerful and frequent fires were on the landscape prior to European settlement. Although we may have enjoyed the outcome or product of pre-settlement prescriptions, fires are surely something we should respect. Fire is a tool and just like any tool it can be used improperly. Effective training and experience is necessary for the successful prescription of fire. By understanding environmental conditions and setting goals, fire can be a very productive tool in your wildlife management toolbox.
To learn more about what others are doing with prescribed fire visit the TPWD burn page. Please use responsibly!
The previous article, Fire: A Change in Prescription, was written by Ryan Reitz, Texas Parks & Wildlife Department (TPWD) Biologist. Originally printed in TPWD “The Cedar Post”, Volume 2, Issue 2, 2012.