Description

From the Summary ... 'Natural disturbances are integral processes in the succession, functioning, and carbon-cycling that occurs in most of the world's boreal forests. Insects represent dominating disturbance factors in Canada's boreal forests and during outbreaks trees are often killed over vast areas. This extensive tree mortality shifts the forest toward younger age-classes which contain less biomass and much of the residual carbon is later released to the atmosphere. A fundamental question is whether climate change will increase the frequency, duration, and intensity of natural disturbances and thus accelerate the rate of warming.Climate change will likely transform the damage patterns caused by many insects and the resulting uncertainties directly affect depletion forecasts, pest hazard rating procedures, and long-term planning for harvest queues and pest control requirements. Because the potential for wildfire often increases in stands after insect attack, uncertainties in future insect damage patterns magnify uncertainties in fire regimes. In addition, insects are important contributors to carbon and nutrient cycling, to biomass decomposition, and to energy flow, and changes in damage patterns can indirectly alter competitive relationships between plants and hence successional pathways, species composition, and forest distribution.The disturbance regimes associated with three of the most important insects of Canada's boreal forest are described. The assumption of integrated ecosystem response is used to develop scenarios of how the disturbance regimes of a number of boreal forest insects might respond to climate change. Methods for improving the incorporation of insect disturbance regimes in carbon budget estimates for Canada's boreal forests are outlined and concepts underpinning a number of proposed approaches to managing insect disturbance regimes to improve carbon storage and sustain other values and benefits of the boreal resource are briefly discussed. An unresolved issue is the trade-off implicit in any approach, be it large-scale planting or protection from insects and fire, which uses fossil fuels. Any short-term increase in the sequestration of atmospheric carbon by the forest comes at a cost of additional carbon imported into the modern biospheric system for the long term. Some research approaches for filling key information gaps are briefly suggested.' © 2000 World Resource Review.