Intensive Harvesting of Forest Biomass As a Source of Bioenergy: Impacts On Soil Microclimate.

In Quebec, intensive harvesting of forest biomass represents one of the most promising sources of bioenergy.  However, removal of logging residues could affect soil productivity as well as stand establishment and growth depending on site edaphic conditions and physiological characteristics of the regenerating species.  Following harvesting, three species were planted in each of four sites across the province of Quebec.  Species range from the fast-growing hybrid poplar to the more conservative black spruce, and sites represent a gradient of soil fertility, and of precipitation and temperature.  Each species was exposed to eight treatments contrasting the influence of the removal of logging residues on microclimate, vegetative competition, and soil nutrients.  The corresponding physiological responses of planted trees regarding tree nutrition, water stress, and growth, will be compared between species and sites.  The goal of the project is to work towards the development of guidelines for the quantity of logging residues that can be harvested depending on species and site, without affecting soil fertility and growth potential.

Preliminary results of soil temperature and moisture depending on treatments at depths of five and fifteen centimetres are available.  During the first years following the plantation, microclimate has a predominant impact on the ecosystem response to the removal of logging residues, and on the physiological response of seedlings.  Soil temperature will influence water availability and root growth: crucial aspects of seedling establishment success, even more than availability of nutrients.