Climate impacts on health and productivity of aspen

Tracking the effects of drought

Tree-ring analysis shows that the region’s aspen forests have undergone dramatic growth collapses in the past, following periods of drought accompanied by defoliation by forest tent caterpillar and other insects.

In 2001–2002, an exceptionally severe and widespread drought led to massive dieback of aspen forests in the parklands of Saskatchewan and Alberta. The continued tracking of forest changes in the CIPHA plot network has shown that the yearly rate of aspen stem death has remained high since the drought of 2001–2002, partly because of consequent damage by wood-boring insects. Similar impacts of this drought are being reported in the western United States, where “sudden aspen decline” has emerged as a major concern.

A pattern of rotating, severe droughts has been documented across large areas of North America since 2002. These droughts may have contributed to the widespread browning and decline of forests reported recently in northern Alberta, northwestern Ontario and elsewhere.

Drought- and heat-induced forest dieback has emerged as a global issue in recent years, highlighting the value of integrated systems for tracking and understanding large-scale, climate-related changes in our forests.

Dead aspen biomass concerns

CIPHA study results are being used in a related initiative to include drought effects in the carbon budget model of the Canadian forest sector.

Analyses from the CIPHA research have revealed that there is an estimated 45 million tonnes of dead aspen biomass within the most severely drought-affected area – the equivalent of Canada’s total harvest of hardwood tree biomass over two years. The carbon content of the dead aspen is also equivalent to about 7% of Canada’s annual fossil fuel emissions, illustrating the importance of drought in the carbon cycle.