Moisture reduction and nutrient retention associated with field-drying forest harvest residues on clearcut sites in Northwestern Ontario, Canada

Abstract

The increased utilization of forest harvest residues as supplemental, inexpensive and renewable energy raises two key concerns: 1) continued removal may negatively affect long-term site productivity; and 2) because 50-60% of this material's green weight is water, transportation and burning costs of the green biomass very inefficient. Leaving the harvest residues to passively field-dry in the clearcut is a common forestry practice in the Nordic countries and is also used as a nutrient management strategy. While field-drying, nutrients are retained on site through the processes of physical foliage shedding, leaching and decomposition. The present study investigated the effects of field-drying on moisture reduction and the release of nutrients from black spruce [Picea mariana (Mill.) B.S.P.], jack pine [Pinus banksiana Lamb.] and trembling aspen [Populus tremuloides Michx.] harvest residues. Field-drying plots were established in recent clearcut sites near Thunder Bay, Ontario, Canada. Trees of each species were felled and the limbs gathered into small biomass piles inside netted enclosures. The piles were left to dry for one year and sampled at regular intervals (0, 4, 8, 12, 16, 48 and 52 weeks) for moisture content, nutrient concentration and percent foliage mass.