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No description available.

The objective of this study was to investigate K, Ca, and Mg immobilization in the stem of species typical of the hardwood forest of southern Quebec. The species examined included American basswood, sugar maple, and white ash from a rich site, and American beech, red oak, and red maple from a poor site. Firstly, rates of immobilization were evaluated over a time span of 40 years. Higher rates of immobilization in the wood only were generally observed on the rich site. Sugar maple immobilized Ca at an elevated rate during 1978--1997, in comparison to the other species on site. In the case of Ca for white ash, and Ca and Mg for red oak, a low wood element concentration and a high rate of growth was associated with a low rate of immobilization. Mean annual immobilization rates on a whole stem basis were also determined for the life of the tree. These results suggest that American basswood and red oak immobilize significant amounts of Mg and Ca in their bark, respectively. / In a second study, concentrations of K, Ca, and Mg across the radial section of the stem (heartwood, transitional, sapwood, and bark) were determined. In a majority of cases, the bark was highest in concentration of base cations. Whereas, for the woody portion of the stem, concentrations were generally highest in the heartwood.

Upland soils are a significant sink of atmospheric methane, but the organisms responsible for methane consumption have yet to be identified. The ecology of methanotrophs was investigated in a beech forest soil which exhibited atmospheric-methane-uptake. Maximal methane-oxidation was observed in the upper mineral layer between the organic and inorganic horizons at a rate of 3.1 +/- 0.3 nmoles CH 4 g [fresh wt soil]-1 d-1. A clone bank of the methanotroph pmoA gene was constructed by PCR amplification from soil DNA extracts. The PCR primers used coamplify the related amoA gene of ammonia-oxidizers. The clones recovered grouped into three clusters: Nitrosospira-like sequences, a group somewhat related to alpha-Proteobacteria methanotrophs and previously referred to as the RA14 group, and a cluster which could not be characterized as either amoA or pmoA sequences. No pmoA genes closely related to genera of cultured methanotrophs were obtained. The 16S rDNA was also targeted using eubacterial and methanotroph-specific primers. 16S rDNA sequence analysis revealed the presence of organisms distantly related to known methanotrophs. Methanotroph enrichment cultures were established by inoculating mineral salts medium with soil and incubating under an atmosphere of 10% methane in air. Gene sequencing from the enrichments indicated the presence of organisms belonging to the genera Methylosinus and Methylocystis. The results suggest that the dominant methanotrophs in the forest soil are not related to known organisms and do not grow under conditions typically used to isolate methanotrophs.

Black spruce (Picea mariana (Mill.) B.S.P.)-feathermoss forests are a common subtype of the northern boreal forests. These forests are associated with large accumulations of mor humus, which is regarded as an important source of nutrients, contributor to soil structure, moisture retention and vital to the long-term sustainability of these forests. Harvesting with protection of advance regeneration (CPRS) is currently used in northwestern Quebec as the method for sustainable management, which reduces soil compaction and protects advance regeneration, and genetic diversity. We examined the effects of CPRS on organic matter and advance regeneration 6 years after harvesting. During the summer of 2002, a humus classification based on observable field characteristics was developed and applied to six CPRS sites in the northern Abitibi claybelt region of Quebec. At each site 75 humus profiles were surveyed and classified by order and thickness of horizons present. Humus horizons were easily observed using morphological features, and master horizon classes were distinguished by their nutritional and biochemical attributes with differences occurring as a result of the natural process of decomposition. Individual humus horizon and total profile thickness was the variable that most affected profile nutrient mass. High forest floor disturbance was associated with shallow profile depth, resulting in low humus profile nutrient mass and low density advance regeneration. Lower forest floor disturbance resulted in deeper profiles associated with higher available nutrients in humus profiles and higher density of advance regeneration. These results suggest that disturbance caused by harvesting may reduce overall stand productivity in the short term due to the effect of low tree density and possibly in the long-term due to loss of nutrients.

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No description available.

No description available.

The effect of species, parent material, and stand age on nitrogen mineralization were examined during aerobic lab and field incubations. The experimental design consisted of 3 tree species (birch (Betula papyrifera Marsh.); poplar (Populus tremuloides Michx.); and conifers (Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss.)); two parent materials (lacustrine clay and glacial till); and three stand ages (50, 75, and 124 years of age). The strongest determinant of nitrogen mineralization potential was species. The effects of parent material and stand age were variable. Total nitrogen, pH, and soil moisture also affected N mineralization. Nitrogen mineralization dynamics may be largely affected by annual changes in quality of organic matter or climate. Available nitrogen inherent in forest stands must be taken into consideration when replacing hardwood stands with softwoods, because eliminating stages of boreal mixedwood succession could have detrimental effects on available nitrogen and forest productivity in the long-term.

No description available.