Shift of weather patterns necessitates rethinking of reforestation methods
OVERTON – Forest landowners can greatly increase the survival rate of pine tree seedlings by changing when and how they plant, according to research conducted here.
"There's been too many (reforestation) failures over the last decade or so," said Dr. Eric Taylor, Texas Cooperative Extension forestry specialist.
"Some landowners have had to replant two, three or even four years in a row because of poor seedling survival."
Second-year data from an ongoing comparison of planting methods show that survival rates could be significantly increased by using containerized seedlings and planting in the fall instead of the winter or early spring.
In 2000, a Texas Forest Service survey showed Texas had 12 million acres in forest land, all of it in the East Texas Piney Woods area. Approximately 61 percent of the forest land was owned by non-industrial private forest landowners. Another 32 percent was owned by industry and investment groups, and the remainder was publicly owned. In 2000, approximately 160,000 acres were being replanted each year. Non-industrial private landowners accounted for about half of the replantings
Taylor's test show that fall-planted containerized seedlings had a 93 percent survival rate compared to 67 percent survivability for bare root seedlings. After two years, the containerized seedlings averaged about 4 feet tall and 6-3/4 inches in diameter. The bare root fall-plantings averaged less than 3 feet tall and about 0.4 inches in diameter.
"Now that the third growing season is under way, the fall-planted containerized trees are really taking off," Taylor said. "Some are 7 feet tall and taller. Compare that to traditional bare root/spring seedlings that have been left behind."
As for spring plantings, both bare root and containerized seedlings had a 83 percent survival rate. The containerized seedlings were only slightly larger than the bare root plantings after two years.
"And we did everything right planting the bare root seedlings," Taylor said.
"Doing everything right" meant meticulous attention to care of the bare root seedlings, soil moisture at planting time, attention to weather conditions and planting techniques, Taylor said.
If everything is done correctly, containerized plantings have little or no economic advantage over bare root seedlings – if planting in the spring, he noted.
But it's rare that everything is done correctly, particularly considering the landowner doesn't have full control over all factors with bare root seedlings, he said. The trees may arrive at the site already stressed.
"And this is a big factor in their survival," Taylor said.
Another big factor is the subjection of new to hot dry conditions before they've had a chance to acclimate and recover from the stress of planting.
Rethinking planting time could remedy the loss due to droughty conditions, Taylor said. Traditional methods prescribe planting in the winter, but conditions – primarily soil moisture and availability of planting crews – may mean planting isn't done until late March. A decade or more ago, East Texas weather patterns favored success with this planting strategy. Relatively cool, wet weather throughout mid-summer gave the new seedlings time to recover from root damage.
But weather patterns have changed, Taylor said.
"Using a Texas Forest Service analysis of 100 years of weather data, we see a cyclical pattern of 25 years of summers that are either hot and drier or cooler and wetter than average," he said. "We're now in about year eight of a 25-year hot-and-dry cycle. That doesn't mean every year will be hot and dry. The last two years weren't. It just means that the trend will be for more hot-and-dry summers."
Most years, Taylor expects this hot-and-drier trend to give an even a bigger advantage to containerized fall plantings over other methods.
Economically, fall planting of containerized seedlings has other advantages.
For example, there's less waste. Landowners are often to advised to over-plant in the spring because of the likelihood of low survivability. With containerized seedlings, the survival rate is higher and landowners can plant fewer trees to get the same stand density.
On wet years, when a high percentage of bare root seedlings do survive, landowners find themselves paying for costly thinnings, Taylor said.
Taylor's research is being conducted near the Texas A&M University Research and Extension Center at Overton. The Bruce McMillan Jr. Foundation, a perpetual trust dedicated to agricultural science and education, made available two tracts of land – each about 100 acres in size – on long-term, no cost leases, for forestry research.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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