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Research explores effects of a warming climate on the region’s Christmas tree industry

BOONE—Local Christmas tree farms are providing a backyard laboratory for Dr. Howard Neufeld, an Appalachian State University biology professor who is interested in how a warming climate might affect the tree industry’s future. The information he hopes to glean is important because it can help tree farmers make decisions regarding future plantings and farm locations.

View larger imageThe Christmas tree industry contributes more than $100 million to the state’s economy. Appalachian State University professor Dr. Howard Neufeld is studying what effect climate warming might have on trees by studying those grown at 2,200 feet in elevation in eastern Tennessee and at higher elevations in Northwest North Carolina. (Photo courtesy of Scott Cory)View larger imageLauren Wood, a graduate student in the Department of Biology, measures tree shoot length to gauge differences in growth patterns of Fraser firs at tree farms ranging from 2,200 to 4,200 feet in elevation. (Photo courtesy of Scott Cory)View larger imageDendrometer bands are used to measure tree trunk growth. (Photo courtesy of Scott Cory)View larger imageScott Cory, a graduate student in the Department of Biology, adjusts a weather station used to monitor weather conditions at a Fraser fir tree farm. (Photo courtesy of Lauren Wood)View larger imageA conifer chamber is used to a measure a Fraser fir’s photosynthesis, the process by which a tree makes sugars, and transpiration, which is the tree’s water loss. (Photo courtesy of Scott Cory)

About 50 million Fraser firs grow in North Carolina, primarily in the northwestern counties and in western counties with elevations above 3,000 feet, which is outside the tree’s native range of 5,000 feet and above. The region’s cooler temperatures and precipitation contribute to the Christmas tree industry’s success.

“One of the goals of this project is to get an idea of what will happen to the Christmas tree industry if the Southern Appalachians get warmer,” Neufeld said.

Since the cost of heating trees in the field to simulate their growth in a warming climate can cost hundreds of thousands of dollars, Neufeld is using the region’s varied elevation to track growth patterns in warm versus cooler terrains.

“We have millions of Fraser firs planted in this area that are nearly identical genetically. The tree farmers have similar growing practices, tree density and ages, and trees that are grown in farms over a range of elevations,” Neufeld said. “Because of that, we can use elevation as a surrogate for warming.”

Neufeld and student research assistants are monitoring tree growth, water use, photosynthesis and carbon output at six tree farms ranging from lower elevations in eastern Tennessee to mid-elevation farms off Hwy. 105 in Watauga County and higher-elevation farms off Hwy. 194 in the Watauga County’s Meat Camp community.

“Even though we are saying elevation is a surrogate for warming, warming is more than just an increase in temperature,” Neufeld said. “It’s a change in the whole climate, water balance, temperatures, length of growing season and soil differences. We realize there are a number of factors changing simultaneously.”

Neufeld hypothesizes that Fraser firs planted at lower, warmer elevations grow more slowly than their higher-elevation counterparts because of stress associated with heat-related water loss and differing rates of photosynthesis, among other factors.

The study, which began last spring, includes taking growth measurements and recording phenology data, such as when the trees bud, when needles grow and when branches extend and stop growing, and the rate at which trees lose water through transpiration or evaporation.

Neufeld will work with the university’s tree ring experts to analyze discs taken from tree trunks to determine tree growth during the last decade at the different elevations.

“Trees growing in hotter and dryer locations have greater loss of water because of the higher temperatures and lower humidity. They also release more carbon dioxide that otherwise might be available for growth,” he said.

“Although, we have heard from the growers that their trees grow to marketable size sooner at the lower elevations, our preliminary measurements at least of diameter growth suggests that trees at lower elevation this year seem to be growing substantially less than those at the higher elevations, but maybe they grow less in diameter but faster in height,” Neufeld said. “We will measure that later in the study.”

Trees grown at higher elevations experience less stress related to water loss, Neufeld explained. “A lot of times the trees at the highest elevation farms (4,200 feet) are in clouds or fog 35-40 percent of the time and get 35-45 percent of their water from the fog. They also have lower evaporation rates,” he said. “If trees are hotter and dryer, they have to deal with greater loss of water because of the higher temperatures and lower humidity.”

Future climate warming could mean that growers at the lower elevations find themselves in an area that is no longer favorable for growing Fraser firs. Will they have to move their farms to a higher elevation as a result? Will the trees at the higher elevations, which also will experience warming, grow more or less?

“We don’t know the answers but those are some of the things to consider,” Neufeld said.

“Growers may ask themselves if they want to invest $100,000 by planting trees at 2,200 feet knowing that in 10 years they might not recoup their investment. We won’t be able to attribute differences to any one specific factor, but by looking at what the trees are doing at the lower elevation, we can say that if it gets warmer and the temperature becomes similar to what it is at the lower elevation farms, growers will know what to expect and perhaps adjust their management practices.”

To view a video about Neufeld’s research, visit http://science.unctv.org/content/oh-christmas-tree.

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