Crews from the Yukon Youth Conservation Corps (Y2C2) and from the Northern Affairs Program spent part the summer contributing to an international effort to monitor forest ecosystems.

The young people mapped and measured trees in two one-hectare plots of Yukon forest in the Wolf Creek watershed. The plots are the first Smithsonian Institution/Man and the Biosphere (SI/MAB) biodiversity plots north of the sixtieth parallel.

SI/MAB plots were started in tropical rainforests in South America, and many countries in other climate zones are now setting up their own networks of plots. The information derived from these plots will eventually help us understand what is happening in the global environment and why.

The Wolf Creek watershed, near Whitehorse, was chosen for the first Yukon sites because water and climate studies have been going on there for several years already, says Environment Canada's co-ordinator for the project, Joan Eamer.

"The beauty of this site is we're starting to develop a good basic understanding of the soils and the water and meteorology. Now we can build on that foundation."

The first step in setting up the plots was to survey them, laying out a 100x100 metre square and then subdividing it into 25 smaller plots called quadrats that measured exactly 20 metres by 20 metres. Volunteers and the Y2C2 crew and some volunteers surveyed the quadrats and marked them by running string between stakes.

The work wasn't easy, says Eamer. The spruce forest in the first plot is very old, untouched by fire or any other major disturbance for a long time. It has a thick moss ground cover and a litter of dead trees and branches that make moving about on the forest floor extremely difficult. It's also excellent mosquito habitat, she adds.

The youth crews worked their way through the entire hectare, marking and measuring every tree, alive or dead, that was at least 2.5 centimetres in diameter at breast-height (1.3 metres above the ground), a standard forestry measurement of trees. Then the trees were mapped by measuring their distance from two corners of the string-marked quadrats.

The dense brush in the old forest made it easy to lose track of directions, Eamer says, so the string lines had to marked with coloured flagging tape to help the mappers determine which lines ran north-south and which ran east-west.

Tree mapping is complete for the first plot and the results show an average of 100 trees per quadrat or 2500 trees in the entire hectare. The vast majority are spruce, Eamer says, but there are also a few balsam poplars and willows, and a single pine tree.

The second plot is in mixed pine and spruce forest that has experienced fire within the past century and so is not quite so dense. It has been surveyed, but the measuring and mapping of trees has not yet begun. Eamer hopes to have that stage complete before new growth begins next spring.

The tree surveys will be redone every five years to keep track of changes in the condition and composition of the forest.

Once the initial surveys are complete, the plots can also be used for further studies. Eamer would like to continue with an inventory of the plant growth in the plots, working down to shrubs, grasses and ground cover. She would also like to see studies of animal and insect life, of the processes that occur as dead trees decay, and of the new growth that takes hold when a fallen tree creates a gap in the forest.

Much of the work will have to be done by volunteers, she says, because little government money is available. However, since the plots are within Whitehorse city limits, she hopes that schools, college classes, and other interested groups might take the opportunity to help expand our knowledge of northern forests.

For more information about the Wolf Creek biodiversity plots and Environment Canada's Ecological Monitoring and Assessment Network, contact Joan Eamer at the Canadian Wildlife Service, Environment Canada, Whitehorse.