The March of the Seward Peninsula Spruce
For almost half a century, Johnny Johnson of Nome has driven the dirt road between his home and Council, Alaska. While motoring the 75 miles to his cabin near Council, Johnson has noticed subtle changes in the landscape. When researchers told him they were checking a certain area for the encroachment of spruce trees, he was way ahead of them.
“Thirty years ago there were no trees there,” said Johnson, who is 65 and a retired meteorologist for the National Weather Service. “Now the trees are beginning to spring up.”
Andrea Lloyd has taken a good look at those trees. She’s a biologist from Middlebury College in Vermont who is interested in the reaction of Alaska spruce trees to the warmer weather of the 20th century. She wonders how treeline, the point in elevation or latitude above which trees do not grow, has changed in the past 100 years.
One of Lloyd’s study sites is on the Seward Peninsula, the “nose” of Alaska that points to Russia, just 30 miles away across the Bering Strait. Tundra plants dominate most of the peninsula, but spruce trees crowd some river valleys and cling to slopes in the southeast corner of the peninsula. This boundary between trees and tundra shrubs intrigues Lloyd, who also studies treeline at several other areas in Alaska.
Each summer, Lloyd, her husband Chris Fastie, their son Galen, and three or four students from Middlebury College travel north to Alaska. For the past two summers, they congregated in patches of white spruce trees surrounding Council, Alaska, about 75 miles northeast of Nome. Using a tree corer, a tool screwed into trees to extract pieces of wood the size of pencils, Lloyd’s crew counted rings that revealed the ages of more than 500 trees. They wanted to find out if spruce crept uphill as the climate warmed in the 20th century. Cold soils and air, often characteristic of higher areas in summer, will stop spruce trees from colonizing an area.
Lloyd and her crew found that trees in the warmer river valleys were the oldest trees around Council. She found trees dating back to the 1600s on the flood plains of two rivers near Council, about 140 feet above sea level. Just fifty feet higher on the hill, the eldest spruce trees germinated in the 1890s. At the top of the slope, at an elevation of about 500 feet, the oldest trees were white spruce that sprouted in the 1920s.
This evidence of younger trees working their way up the hillside fits with Lloyd’s hypothesis that the slightly warmer temperatures of the 1900s may be warming up soils enough for spruce trees to occupy areas in which no one alive has seen them before.
“As best I can tell, the movement up the hill started when climate began warming, around the 1880s,” Lloyd said.
By checking the ages of trees at different elevations, she found that in the last 150 years white spruce migrated about 15 kilometers into new territory that was perhaps too cold in the past. She also found sites where dense patches of spruce trees had not advanced out of the river plain except for areas where permafrost may have melted. She will return to that valley in the summer of 2001 with UAF Professor and Hydrologist Larry Hinzman to check for permafrost and its effects on spruce tree advancement.
Lloyd said that treeline seems to be on the move in much of Alaska. She has studied the advance of spruce trees throughout northern Alaska, and found similar results—the march of the spruce trees is on, possibly triggered by a warmer climate.
As Johnson said from his home in Nome, the face of the north is changing.
“When we saw all that tundra and no trees years ago, we thought how it was then, it would be forever,” he said. “But in the last 30 years, there’s been an abrupt change.”
