Houston Regional Group - News

In recent years fires, mostly in the Western part of the United States, have burned large areas of forests. Because millions of acres burned numerous stories in newspapers, magazines, television, and radio emphasized the danger of forest fires. It is easy to get the impression that fire impacts in Western forests are representative of the entire United States. It would be a mistake to believe this.

Fire in Sam Houston National Forest (SHNF), is not the problem portrayed in the Western United States. Do we have an urban-wildland interface? Yes, indeed. Did fires naturally burn some or many of the forest ecosystems in SHNF? Definitely! Can fires cause considerable tree and vegetation mortality? Yes, without a doubt. But we are different from the Western United States!

SHNF, 50 miles north of Houston, Texas, exists on the Southeast Coastal Plain of Texas, just inland from the counties that fringe the Gulf of Mexico on the Texas Coast. The counties of Montgomery, Walker, and San Jacinto, where SHNF is located, consist of gentle, rolling, topography, with many ephemeral, intermittent, and perennial streams that dissect the low elevation ridges and uplands. Extensive flatwoods (poorly drained forests on nearly level topography) are found throughout SHNF. Elevation above sea level in SHNF is about 100-300 feet.

In SHNF different conditions exist than those found in the Western United States. These different conditions affect the impacts that fire has on forest ecosystems. What are these different conditions?

1) We have 50 or more inches of rain each year. 2) We commonly have torrential thunderstorms which flood wide expanses of forests and floodplains. 3) We have frequent hurricanes, tornados, and windstorms. 4) We have high relative humidity (80-90%).

There are many sources of natural disturbance (incidents that kill vegetation) in SHNF. For instance, over several decades large areas of forest with native pines (Loblolly and Shortleaf) are attacked or killed by southern pine beetles. Disturbances help regenerate, bring variation to, and diversify our forest ecosystems and landscapes. In SHNF fire is only one disturbance that shapes the landscape.

It is not that we do not have droughts or that lightning doesn't ignite burns. We have both. However, about 85% of the fires that burn in East Texas are caused by people. 1 Most fires in East Texas are caused by people but we rarely have large fires. According to one press release by the Texas Forest Service (TFS), the state forest agency, in East Texas, 27 wildfires burned 550 acres in 1999. 2 This is an average of 20 acres burned per fire. A fire of a few hundred acres is considered large in East Texas. In the year 2002 the TFS reported five fires in SHNF. These fires burned a total of three acres. 3 Over the last eight years (1998-2005) a total of 75 fires have been recorded in SHNF. These fires burned a total of 808.7 acres or 10.8 acres/fire. 4

According to the U.S. Forest Service (FS), for 1998-2005, of the 75 fires that burned in SHNF 11 (14.7%) were caused by lightning and 64 (85.3%) were caused by humans. The total acreage that burned due to these fires was 808.7 acres, of which 628.6 acres (77.7%) burned due to human caused fires and 180.1 acres (22.3%) burned due to lightning caused fires. The largest fire burned 168 acres and the smallest fire burned 0.1 acres. 5

The extensive network of roads, oil/gas pipelines, power-lines, ditches, and streams in SHNF provide firebreaks that reduce the spread of fires. Easy access and quick response by fire fighters make large fires relatively unusual occurrences in SHNF. Suppression of wildfire is complete. Prescribed fires do burn thousands of acres but are usually ignited during late winter and spring, when the risk of wildfire is usually not high. The most likely time that a severe fire would burn extensive acreage in SHNF is during summer (June- September) when droughts and high temperatures occur.

So how did the natural forest used to burn? Unfortunately, no one really knows the natural fire frequency, duration, intensity, rate, seasonality, evenness of burn, number of start locations, regime, and vegetation mosaic/patchiness of the many different forest ecosystems that used to, and to some extent still do, exist in SHNF.

There are clues that can be used to give us an idea about fire and the original forests of SHNF. In the 1996 Environmental Impact Statement (EIS) for the Forest Plan for the National Forests and Grasslands in Texas (NFGT), Appendix H, Vegetation and Natural Plant Communities, the FS makes the following statement about the Loblolly Pine Ecosystem, the predominant forest ecosystem in SHNF, "Pure pine stands in the loblolly region were rather limited in area, often restricted to deep sands. More typically, loblolly seemed to grow in association with hardwood." 6

Appendix H goes on to say, "Fire is certainly an important ecological factor in these Loblolly forests . However, loblolly is not a fire- resistant species and fire frequency associated with occurrence is lower than that associated with the occurrence of most other southern pines."

The FS states in Agricultural Handbook 713, "In the Coastal Plain, loblolly pine grew best mixed with hardwoods along stream margins and around swamps on sites that were not subject to long periods of flooding or to serious fires . However, because loblolly pine has limited tolerance to fire, it generally could not compete with longleaf pine on well-drained Coastal Plain lands subject to regular fires." 7 It is important to note that hardwood tree leaves and ground litter do not burn as readily as pine tree needles and debris. This is because pine needles and debris have flammable resin.

The Nature Conservancy and Stephan F. Austin State University prepared an Ecological Classification System (ECS) for the NFGT and the Kisatchie National Forest in Louisiana. According to the ECS the estimated historic fire frequency for Loblolly-Hardwood dominated forest ecosystems (the most common forest ecosystem found in SHNF) was 10-20 years. The Southeastern United States is a landscape known for very frequent fires with return intervals of 1-3 years. A 10-20 years fire return interval is considered infrequent by the ECS. 8

Historically, very little Longleaf Pine was found in SHNF. The other native pine, other than Loblolly Pine, found in SHNF was the Shortleaf Pine. The 1996 EIS for the Forest Plan has this to say about Shortleaf Pine Ecosystems, "Because the shortleaf forests were removed early and often completely, we have little knowledge of their character. It is believed that pure stands did occur, but that pine more often grew in association with hardwoods (and especially with upland oaks and hickories). Remnant shortleaf-oak-hickory forests have been described by a number of authors. It is possible that many areas once supported relatively pure short-leaf-bluestem communities . Shortleaf is adapted to survive relatively frequent fires. It can sprout prolifically after burns when young and is almost unaffected by growing-season head-fires when its diameter breast height is greater than 4 inches. In a typical shortleaf fire regime, fire may be of moderate intensity and reoccur approximately every 10 years."

The ECS estimated a 5-10 year fire return interval for most Shortleaf Pine Ecosystems although a few were estimated to have fire return intervals of 3-5 years.

In SHNF Loblolly Pine was probably the dominant pine tree. The 1938 Working Circle (management plan) states that of the acres approved and acquired within SHNF, about 57% was Loblolly Pine, 32% was Shortleaf Pine, and 11% was hardwood. These figures must be used with caution since Loblolly Pine is a prolific seeder and the figures above could reflect this biological fact. The figures also probably underestimate upland hardwood trees because pine trees were the commercially sought after upland species and good records of hardwood tree removal from the uplands were not usually kept. 9

Although the true composition of SHNF can only be inferred we can say that Loblolly Pine was dominant over Shortleaf Pine during the acquisition of SHNF. Most logging of the largest trees of the virgin forest in East Texas occurred in the period 1900-1930, or right before SHNF was acquired.

These clues suggest that the Loblolly Pine Ecosystem was the dominant forest ecosystem and probably both the Loblolly Pine and Shortleaf Pine Ecosystems included many hardwood trees. Some of the hardwood trees that possibly existed with one or both of these two pine species include White Oak, Southern Red Oak, Black Hickory, Sweetgum, Water Oak, Post Oak, Blackjack Oak, Bluejack Oak, Red Mulberry, Sassafras, Southern Magnolia, Black Gum, Common Persimmon, Flowering Dogwood, Eastern Redbud, American Basswood, Mockernut Hickory, Sweetbay Magnolia, American Beech, Bitternut Hickory, American Hornbeam, Eastern Hop Hornbeam, and Swamp Chestnut Oak.

Currently, in SHNF, the FS burns forest ecosystems too frequently. The 1996 Revised Land and Resource Management Plan for the NFGT requires burning of about 75% of the four National Forests in Texas (Sam Houston, Davy Crockett, Angelina, and Sabine National Forests) every 2-5 years. This frequency of burning is 2-6 times greater than the historic fire frequency for a number of Loblolly Pine and Shortleaf Pine Ecosystems. 10

Burning the forests of SHNF today more frequently than in historic time,s combined with an emphasis on commercial pine management (forest practices), results in forests with greater amounts of flammable fine fuels (needles, twigs, and small branches). Thin logging; hardwood tree under-story/mid-story logging (to create more habitat for the federally endangered Red-cockaded Woodpecker); and increased burning cause the growth of seedlings, saplings, shrubs, vines, and the re-sprouting of hardwood trees as more sunlight hits the ground. 11 The sunlight dries out vegetation during times of drought and hot weather in June-September

The conditions created by the above mentioned forest practices combined with drought and many in-holdings and adjacent private lands that lie in close proximity to SHNF, expose forests to additional human sources of fire starts and increase fire risk. Restoring natural fire frequencies for Loblolly Pine and Shortleaf Pine Ecosystems will create less flammable forests and reduce fire risk. The restoration of natural fire frequencies with the judicious application of fire-proofing around structures on private lands and in-holdings will result in safer residences and more natural forests which are less flammable.

1) Texas Firefighters on Standby for Hazardous Fourth of July Weekend, Texas Forest Service, http://txforestservice.tamu.edu/news_events/1998/june/29a.html 

2) Wildfires Erupt in East Texas, Texas Forest Service, December 28, 1999, http://txforestservice.tamu.edu/news_events/1999/december/28a.htm .

3) Texas Interagency Coordination Center, Situation Report for December 16-December 31, 2002, http://www.tamu.edu/ticc/state_summary/situation_report.htm 

4) Forest plan put to test in Texas, Dina Cappiello, The Houston Chronicle, January 11, 2003.

5) March 4, 2003, March 5, 2004, February 8, 2005, and February 3, 2006 letters from the U.S. Forest Service, Sam Houston National Forest, to the Houston Sierra Club.

6) Appendix H, Vegetation and Natural Plant Communities, Final Environmental Impact Statement for the Revised Land and Resource Management Plan, National Forests and Grassland in Texas, U.S. Department of Agriculture, U.S. Forest Service, 1996.

7) Loblolly Pine: The Ecology and Culture of Loblolly Pine (Pinus taeda L.), Robert P. Schultz, Agricultural Handbook 713, U.S. Department of Agriculture, Forest Service Southern Forest Experiment Station, December 1997.

8) Ecological Classification System for the National Forests and Adjacent Areas of the West Gulf Coastal Plain, The Nature Conservancy and Stephen F. Austin State University, July 1999.

9) Management Plan Sam Houston Working Circle Texas, U.S. Department of Agriculture, U.S. Forest Service, June 7, 1938.

10) Revised Land and Resource Management Plan, National Forests and Grassland in Texas, U.S. Department of Agriculture, U.S. Forest Service, 1996.

11) Effects of Fire on Vegetation of the Southeastern United State, Kenneth H. Garren, Paper No. 98, Journal Series, Georgia Agricultural Experiment Station, The Botanical Review.

Brandt Mannchen Chair, Forestry Subcommittee Houston Regional Group of the Sierra Club February 19, 2003 Revised May 8, 2004 Revised December 15, 2006

January 2007

Last updated:  12/16/2006.   Content © 1999-2006 by the Sierra Club.