Like bears and berries or moose and willows, caribou and lichens go together. In winter, almost nothing is as important for caribou as these slow-growing, mat-forming plants.

Caribou would not make it through the long northern winters without plentiful supplies of lichens, and they spend much of their time digging through the snow to find where these plants lie buried. Fortunately it is not a blind search as they can actually smell where the plants are located beneath the snow.

For biologists working with caribou, the best way to figure out which areas provide good winter habitat is to start looking for lichen. But mapping where these plants grow can be a challenge.

Lichens typically grow in well-drained areas of the forest. Fly over an area with lots of lichen, and you would not be able to see them for the trees. On the ground, it can take researchers huge amounts of time to walk through an area and map where lichens are growing.

That's why Jody Schick is trying to find an easier way to figure out which areas are good for lichen. A biology student at the University of British Columbia, Schick grew up in the Yukon and has worked for the Yukon Department of Renewable Resources for several summers.

The department had tried to use existing vegetation maps to determine where lichen would be abundant. But several attempts at finding a relationship between lichen and types of vegetation that were already on the map did not work out.

Schick is now taking a different approach, trying to figure out which soils and topography lichen prefer. He is also looking at the age of the forest to see how long it takes lichen to develop in different types of forest.

"I'm trying to find a cheaper way to look at big areas and get a rough idea of what is there," he says. And as he began to do research on the issue, he found that not much is known about exactly where lichen grow.

It is well-established that lichens are most plentiful in mature forests where they have had time to develop. Lichens only grow about one centimetre per decade, so after a disturbance such as fire or logging, it can take 30 to 70 years for lichens to re-establish themselves.

This is Schick's second summer of fieldwork, and he has been sampling areas south of Whitehorse that are within the range of the Southern Lakes Caribou Herd. This woodland herd, which once numbered in the thousands, consisted of only about 450 animals by the time a recovery program began in 1992.

After extensive efforts, including a voluntary ban on hunting by First Nations, the herd is increasing in size. But development in the herd's range will always make winter habitat an issue in the Southern Lakes area. The caribou depend on areas where light powdery snow covers abundant supplies of lichen, a combination usually found in valley bottoms where most homes, farms and roads are also located.

Schick is trying to come up with a method that links lichen abundance with soil properties such as drainage, texture and nutrient status, and topographic features such as the slope of an area and the direction that it faces. If he can establish these links, existing topographic and soil maps can be used to determine which areas probably have abundant lichens.

Better estimates could also be made of how long it takes lichens to establish themselves in different types of forest. "We have a rough idea that it takes a long time, but when people are thinking about things like rotations of forestry, it would be nice to know whether it takes 50 years or 70 years or whatever."

If his method works out, he thinks that it could be used in conjunction with satellite imagery to estimate where lichen are most abundant. It might also prove useful for looking into the future.

"In some pine forests it seems that lichens continue to increase if the forest does not burn, while spruce forests typically get denser until the lichen is taken over by mosses. It would be nice to quantify the time that it takes for these processes to happen, so that we could look at how the Southern Lakes area might change over time."

Schick's work is being supported by the Northern Research Institute and the Yukon Department of Renewable Resources. For more information he can be contacted at joschick@interchange.ubc.ca.