July 31, 1996
A University of Colorado at Boulder research team will fly to Siberia this summer to continue a long-term study on the increasing reproductive activity by trees along portions of the Arctic tree line that may signal greenhouse warming.
Harvey Nichols, a professor in the environmental, population and organismic biology department, said evidence from northern Canada collected during the past 24 years indicates dwarf spruce trees at the forest edge have begun producing cones and pollen and may be readying to migrate into the tundra. A research trip by Nichols last summer to Russia indicated a similar “awakening” among dwarf spruce trees may be occurring at the Siberian Arctic tree line.
“Arctic tree line is sensitive to climatic change and is expected to be one of the first major vegetation boundaries to register greenhouse warming if it is indeed occurring,” he said. But it will take years of additional research to determine if the recent spruce activity is a signal of warming triggered by a buildup of greenhouse gases in Earth’s atmosphere or just a “natural flickering” of the climate, he said.
Nichols received a $30,000 grant from the National Geographic Society to travel to the Tiksi region of northwest Siberia in July to collect data on dwarf spruce and larch reproduction at tree line. He will be accompanied by CU-Boulder geography department senior Terry McManus, EPO biology graduate student Mary Wisz and linguistics department acting Chair Allan Taylor.
The CU research team, which also will include several Russian ecologists, will fly to the city of Tiksi and take a chartered helicopter to a number of sites along a 600-mile transect near the Lena River, said Nichols. The Lena River is a massive Siberian waterway slightly smaller in size than the Mississippi River.
The 1994 study by Nichols in the Canadian Arctic indicated dwarf spruce trees at eight sites along an L-shaped, 930-mile transect connecting Hudson Bay, Great Slave Lake, Great Bear Lake and the Arctic Ocean showed increasing reproductive activity in the past two decades. Although none of the trees were producing pollen or cones during Nichols’ 1973 research trip, trees at all eight study sites were producing both by 1993.
In addition, spruce seedlings up to six inches high were observed at several of the Canadian sites in 1993, said Nichols. The seedlings, which were only a few feet from the parent trees, appear to have sprouted in the mid-1980s.
“What I was seeing resembled predictions from warming scenarios,” said Nichols. “The trees are not yet advancing, but they appear to be on their tiptoes and in the starting blocks, readying to move into the tundra.”
Under colder conditions, spruce trees at the edge of the northern forests and in “tree islands” on the Arctic tundra reproduce asexually via underground shoots known as clones, he said. During slightly warmer periods, the trees reproduce sexually by forming pollen and cones that lead to new seedlings.
The reproductive activity levels of dwarf spruce at tree line near the Ob and Taz Rivers in north-central Siberia in 1995 was “nearly identical” to that seen in spruce trees in the Canadian Arctic in 1993, said Nichols. “If we find the same thing this summer in the Tiksi region, it will be an indication that quite a substantial area of northern tree line may be experiencing polar warming.”
Dwarf spruce trees at tree line appear to periodically “turn on and off” over the centuries in response to climate fluctuations, said Nichols. Five thousand years ago, for example, scientists believe the temperature at Arctic tree line was roughly 6 degrees to 7 degrees F warmer than it is today, he said.
As they did in the Canadian Arctic, Nichols and his students will place pollen traps in Siberian spruce groves at the edge of the forests to monitor pollen release during the summer months. The research team also will examine the trees visually for evidence of cone formation.
“This activity by the trees could turn off at any time,” said Nichols. “But if it keeps up and turns out to be a result of increasing carbon dioxide in the atmosphere, then the southern edge of the tundra will slowly fill in with trees.”
Nichols said he hopes to return or to send students to both the Siberian and Canadian Arctic regions in the coming years to monitor reproductive changes in the trees. Funding for the project is from the National Science Foundation, CU-Boulder and the National Geographic Society.
Courtesy of the University of Colorado