BURNS - Imagine a world without adolescents. Not bad, you might say, but what about a world that doesn't even have many middle-aged residents?
A vegetation "belt" from eastern Oregon south into Nevada has a perplexing population of young and old juniper trees with little in between. While junipers can live to be 1,600 years or older, 97 percent of the trees in the area are less than 100 years old.
And that has implications for other plants and animals that must compete with the juniper.
Researchers at Eastern Oregon Agricultural Research Center in Burns, operated by Oregon State University and the U.S. Department of Agriculture's Agricultural Research Service, are tracking this population trend, trying to predict the consequences.
Just as the human baby boom in the United States can be traced to changes in the economy and post-World War II marriages, the spread of these young junipers has historical underpinnings.
It's not that trees more than 100 years old are dying particularly fast, according to Rick Miller, an OSU range scientist. The population shift is due to a rapid spread of young junipers that began in the 1870s, he said.
"About 100 years ago, growing conditions were ideal and the area had been overgrazed by an influx of cattle, sheep and horses that came with homesteaders," Miller said. "Junipers were also cut for fence posts and other building materials. So, what you see today are the larger, older trees in the fire-safe rimrock areas and the trees that began to quickly propagate during the 10-15 year intensive grazing period that began in the 1870s."
Miller said grazing affects juniper growth indirectly. Animals eat most of the vegetation between trees so when there is a fire, there is less burnable material to carry it across the range from tree to tree.
This "natural fire suppression" allowed many more junipers to live than in the centuries before grazing, according to the scientist.
"Most of this we can deduce from grazing and fire records, but we are still looking at a relatively small time span in the 10,000-year history of the western juniper belt that runs from John Day down to northwestern Nevada," said Miller.
"Looking at the rings of core samples from 1,300-year-old junipers gives us more information," Miller said. "For instance, we can look at fire and precipitation cycles and see that big fires are usually preceded by two to three years of good growth climate."
Tony Svejcar, a USDA researcher at the station, says the difficult part of his and Miller's work is "coming up with a management plan for thousands of acres, based on our smaller plot experiments and observations."
Two of the management tools the researchers have identified are cutting junipers and prescribed burning of sections of rangeland.
"Management experiments do yield dramatic changes," Svejcar said. "An uncut range plot might yield only 100 pounds of forage, while the cut plot produces 1,000 pounds per acre.
"When junipers don't dominate the plot, there is less erosion and more plant and animal diversity," Svejcar added. "Still, we do know that we're not keeping up with the juniper expansion even with prescribed burning and cutting."
"We're just trying to present alternatives for managing the land," said Miller. "That may be burning or cutting or leaving it alone. Do you want a landscape that is dominated by junipers or do you want to shoot for the maximum biodiversity, including other plant life, birds and small mammals?"
Eighty percent of the juniper belt is on federal land, noted Svejcar. While fire and cutting are the most effective management tools, the questions are: when and where?