Fire in Central Texas
“Prescribed burning will do more to improve habitat for deer and numerous other wildlife than any other practice. Prescribed burning is also considered the ‘cheapest, most effective habitat management technique.’ ” – TPWD website
Wildfires were once essential to Texas. Grasses and understory plants used to burn at intervals of two to five years. Those fires not only determined the mix of flora and fauna that made up the ecosystem, they also regenerated the land.
When humans with property, houses, and ranches arrived, humans began to suppress any fire that came upon the landscape. They protected their property. Now, a group of Central Texas specialists are bringing fire back. Depending on their mission, they seek to sustain habitat for endangered animals and/or enhance water’s infiltration of the aquifer.
While catastrophic fires cause untold damage to life and property, carefully controlled burns help keep wildfire fuel in check. Different types of prescribed burns are used in Central Texas, depending on what the fire managers want to accomplish. Some of these missions and lands present unique challenges to the fire starters.
I recently spoke with Carl Schwope, the Fire Management Officer at Balcones Canyonlands National Wildlife Refuge. Located west of Austin, the refuge’s primary purpose is to protect the nesting habitat of two endangered migratory birds — the golden-cheeked warbler and black-capped vireo. These birds have two different habitats. Keeping the birds happy with their area of the forest is Schwope’s job.
“For the vireo, we burn for shin oak,” Schwope said. “This habitat has about six feet of brush covering about 30-60% of the ground. We want a mosaic of brush and trees.” He said the vireo like shin oak thickets.
Shin oak, according to wildflower.org, “forms thickets on shallow soil, seldom a single tree, found mostly on flat-topped limestone hills.”
“Because shin oak is an early successional brush,if we let it keep growing, it would get too tall. So we need to burn it and set it back,” Schwope said. To keep the thickets, his crews burn at four to six year intervals.
“Burning for grasslands is pretty well understood and studied. Keeping grassland is a well-accepted use for fire from a habitat standpoint,” he said. Schwope has been instrumental in prescribed burns at over 40 different refuges around the country.
Though burning for vireo is pretty straightforward, Schwope said they don’t have much land dedicated to vireos. “Of the 20,000 acres of refuge, 15,000 are managed for the golden cheeked warbler. Very little is managed for the vireo.”
“Most of what we have is warbler land,” he said. “At the last count, we had only 150 vireo” on our refuge.
For the golden-cheeked warbler, the refuge manages a much larger area — 15,000 acres. And the warblers want a different habitat, which is harder to maintain.
Warblers feed on insects that live in the juniper and oak woodlands. They arrive in March and they only nest and raise young in Texas. The key is the mixed, old growth Ashe juniper and Spanish oak woodlands. The terrain has to include tall, closed-canopy mature trees.
“Most of the vegetation we have here is fire dependent. Using tree rings, studies have shown that the refuge would have a fire, on average, every five years.”
One of the issues that Schwope sees is a lack of new Spanish oak trees versus the new Ashe juniper.
“Oaks have many predators: squirrel, disease, age, deer. They are short-lived trees. But juniper only has one predator – fire. If left alone, the refuge would keep losing oaks and gaining junipers until the habitat was unfit for warblers,” he said.
Before fire was used for clearing areas of the forest, mechanical methods were used – chainsaws and heavy equipment. Schwope said the mechanically cleared gap in the canopy would fill with Ashe juniper — high density, small diameter juniper trees.
Using fire on the refuge helps promote the Spanish oaks. He said that when fire creates gaps in the forest canopy, oaks fill in the area. “The fire knocks out the juniper berries and the juniper seedlings,” he said. “Fire gives a boost to oaks, because they are sprouting and they have rootstock.”
“Habitat management for the warblers in the refuge involves burning only the understory to raise the crown base,” Schwope said.
For warblers, the habitat needs some fire, but not too much. When the refuge crew conducts a prescribed burn, conditions must be perfect to have the fire burn slowly along the ground without jumping to the mature forest canopy
“We know that high severity fire hurts the habitat,” Schwope said. He told of a 1996 high severity fire at Fort Hood that burned 10,000 acres of warbler habitat. The area burned again in 2011. Due to the slow recovery of Ashe juniper, it will be decades before this area will be suitable habitat for the warbler. So, if it is fire that will help these habitats, it won’t be high severity fire. Once high severity fires get started, they are hard to put out.
During burns in warbler lands, stopping a fire’s transition from ground to the canopy is based on two main things: how hot the fire is burning and how close to the ground the canopy is (canopy base height). If the canopy base height is 5 feet or more, then a fire is less likely to become a crown fire and destroy warbler habitat and people’s homes.
It is difficult to introduce a prescribed fire to an area for the first time. If there has not been fire in an area for many years, the fuel loads are tremendous. Once an area has fire carefully introduced, however, subsequent managed fires are more easily implemented. During some burns, there might be a flare up or a tree might fall across the fire line. Schwope and his crews are there, waiting to put these out. Before a prescribed fire is given a green light, the fire manager takes into account the fuel load, moisture, wind, temperature, and innumerable other factors.
Schwope’s influence is felt in other areas of Austin, as one of his former crew members, Luke Ball, is in charge of fire management at Austin Water Utility Wildland Conservation Division.
Ball manages the land owned by the City of Austin. This includes the Water Quality Protection Lands (WQPL) and the Balcones Canyonlands Preserve (BCP). The WQPL is managed to promote clean water going into the aquifer that flows to Barton Springs. The purpose of the BCP is to set aside land for the golden-cheeked warbler, black-capped vireo, and six karst invertebrates.
WQPL has areas like the Onion Creek Tract in South Travis County. This land owned by the city has Ashe junipers first cleared through mechanical means. Ball then manages the land with fire. Each parcel is burned in a 4, 5, or 6 year rotation.
The city’s website says, “prescribed fire is an effective land management tool on the WQPL, which are managed as grassland savanna environments to protect the quality and quantity of water reaching the Barton Springs segment of the Edwards Aquifer.”
Ball said the land recharges more water to Barton Springs when it is a savanna than with forest cover of oaks, junipers, and other trees.
“If we don’t burn and remove seedling trees and brush, within 9 years the brush will recover,” Ball said.
Walking around the Onion Creek tract of the WQPL, the grass savannas spread out giving long unobstructed views. Karst features like caves and sinkholes can be easily seen and managed. In this special area, the aquifer refills quickly. But, any pollution in the water also directly affects the quality of that recharge. Keeping the water pristine is the main goal of this site. For visitors, the area’s regular burns also nurture the long vistas and easy access.
Burning in a controlled setting is the goal of the fire managers. But when the land gets dry, hot, and windy, wildfires can rage out of control. In the past, there are many examples of wildfires delivering destruction upon the land.
Actually bringing fire to the managed land hasn’t always been seen as a sound strategy. In 1935, the USDA Forest Service instituted the “10 AM Policy,” wherein the objective was to prevent all human-caused fires and contain any fire that started, by 10 a.m. the following day. During the 1960’s and 70’s, scientists realized that fire was an essential part of the ecology for much of the habitat. Policies changed which promoted burns to reduce wildfire fuel and promote native landscapes. With the help of the fire management crews in Central Texas, our ecology can be more naturally managed, with fire.