IS GLOBAL warming pulling Canada's treelines further north? No one knows for sure, but Katherine McLeod (PhD'99), a lecturer in York University's Geography Department, hopes that by studying white spruce populations in the Tuktoyaktut Peninsula she'll find out.

The spruce exist in a highly stressful tundra environment. They likely established themselves in a warmer age and persist despite climate deterioration, says McLeod, who notes that many of these trees have stood their ground, largely unchanged for more than 1,000 years.

"What we want to know is whether these trees are responding to the increasing warmth," she says. "There's some indication that at timber lines in the mountains there's movement of treelines to higher altitudes."

On the other hand, isolated clumps that exist north of Inuvik, where the conifers stand, on average, less than three metres tall, are not responding to global warming, she says. McLeod says that may be due to moisture stress. "They may not be responding to temperature increases because moisture levels are decreasing."

Part of her study includes trying to determine just how old the trees are by looking at their annual rings, and cross-dating live individuals with dead stumps. "It's really an initial study to get an idea of where they're located, what they're doing and how they're persisting there."

Illustration:Julie Seregny-Mahoney