COLLEGE STATION — Clearcut forestland may appear devastated just after harvest, but looks are deceiving, according to an ecological study of an East Texas hardwood forest.
Virtually all of the soil, water, amphibians, reptiles, small mammals and revegetation process on clearcut land were unharmed or enhanced within two years of the harvest.
“It is like a natural disaster,” Dr. Jim Dixon, Texas Agricultural Experiment Station herpetologist, said of the clearcut. “Some animals may go through a cycle of decline, but they don’t disappear completely. And, they return when new plant growth returns.”
The study, which compared uncut areas to partially cut and clearcut areas in bottomland hardwood forests of Tyler County, was a first for looking at the broad impacts of clearcutting on such an ecosystem. Dixon teamed with Experiment Station forest scientist Dr. Mike Messina, U.S. Forest Service wildlife biologist Dr. Jim Dickson and Dr. Stephen Schoenholtz of Mississippi State University in the two- year study.
Plants, soil and water were examined to determine whether alterations would impact the future plant or animal life there.
Prior to harvest, there were 37 species of woody plants with the most prevalent being water oak, willow oak, ironwood, American holly and cherrybark oak. One year after the harvest, the most abundant were water oak, willow oak, ironwood, American holly and sweetgum.
“There were about the same number of species, types and individuals before and one year after the cut,” said Messina.
He said as expected, the biggest difference appeared in the clearcut areas since “the more disturbance of an ecosystem, the more diversity you have afterwards.”
“Before the cutting, this forest had a closed canopy, so it was very shady,” Messina said. “When the canopy is opened or removed during a cutting, that provides sunlight which all plants need to grow. A lot of species move in and compete with each other.”
Water quality was checked for physical and chemical properties by taking samples from the streams and groundwater in the area, Messina said. Turbidity, temperature, pH, nitrates, ammonium, phosphates and oxygen were among the properties tested.
“The bottom line is that none of these things were significantly affected in the stream water,” he said. “In a couple of occasions, nitrate levels went up in the groundwater but never for a long period and never above the U.S. Environmental Protection Agency’s safe limit for drinking water.”
Messina said nitrate is a by-product of decomposing plant matter, caused in this case from the slash, or unused pieces of trees that remained on the land after the cutting.
Soil disturbance, which could affect the ability of new plants to grow, was monitored through bulk density, or compaction, and porosity, which relates to the ability of water to move through soil particles.
Neither the partially cut nor the clear-cut areas showed major disturbance of the soil to the point that future growth would be affected.
“There was some significant compaction in the top 6 inches of soil on the clearcut land, because the trees were mechanically harvested with heavy machinery,” Messina explained.
He said that the amount of compaction did not appear to be a problem for regrowth given the number of species that returned to the areas in the two years following the cut.
Messina stressed that the harvest of trees in the research plots followed Best Management Practice techniques, such as not cutting trees on the sides of streams to protect water courses.
Similar results were found for animal populations on the test plots.
Rather than looking at a single species, as many studies have done, the researchers examined the impact on amphibians, reptiles and small mammal communities.
“Bottomland hardwood systems are critical wildlife habitat,” Dickson said. “In East Texas, nearly 75 percent of the bottomlands have been converted to other uses.
“Small mammals are an important component of these systems, but there has been little information on the effects of timber harvest on their populations,” he added.
Of the 38 amphibian and reptile species seen on the plots, 15 species were selected for the study because their populations were large enough to analyze effects of the land treatments on them, according to Dan Foley III, a graduate student who this month earned a master’s for work on this project under Dixon.
Only the marbled salamander showed a significant decline, Foley said.
“The marbled salamander needs a closed canopy with moist ground,” he said. “It is very intolerant of sunlight.”
Other amphibians, such as the Texas salamander, showed marked increases in population. Some of the animals may have moved to adjoining, uncut forests or stacks of slash until the area’s natural plant regrowth was sufficient to provide habitat, the researchers said.
Foley also kept tabs on four lizard and four snake species. These populations remained stable, he said, with none showing declines.
“It’s important to note that the slash was left behind for animal habitat after the harvest and that the cuts were relatively small at about 20 acres each,” Foley said.
The clearcut was beneficial for the reptiles, Dixon said, perhaps because the open area increased rodent populations which the reptiles prey on.
Rodents prospered in the clearcut areas, according to Dickson.
“They responded positively,” Dickson said. “They came after cuts were made, in sizeable numbers.”
Dickson said slash piles provided habitat for the rodents, and grass and other vegetative growth provided food.
“We caught 2-1/2 times as many rodents in the clearcut areas as in the uncut control area,” Dickson said. “It made us wonder where they all had migrated from, and how did they know to come?”
As the hardwood forest continues to recover, however, Dickson said, rodent numbers likely will fall due to the decreased food supply.
Overall, the researchers said, harvests haven’t proven harmful for the ecosystem along the Neches River.
“If Best Management Practices and common sense are used, loggers can get timber out and not detrimentally affect the ecosystem,” Messina added.