Doug G. Maynard

Armillaria root disease, stand characteristics, and soil properties in young lodgepole pine.

Thirty six lodgepole pine stands in west-central Alberta, ranging in age from 9 to 28 yr of age, were surveyed for Armillaria root disease mortality. Selected stand characteristics and edaphic factors were recorded in each stand to determine if there was a relationship between these factors and Armillaria root disease. Data was analysed using a multivariate linear regression. A statistically significant relationship was found between sand content, ammonium (NH4+) concentration and Armillaria root disease. The incidence of Armillaria root disease increased significantly with increasing sand content of the surface mineral horizon and decreasing NH4+ concentration of the surface organic horizon (LFH). Stand age, density, elevation, soil pH, depth of the surface organic horizon (LFH), calcium (Ca), phosphorus (P), potassium (K), magnesium (Mg), and sulfur (S) did not have a significant effect on the amount of mortality.

Soil nutrient and vegetation response to patch clear-cutting of an aspen forest near Meadow Lake, Saskatchewan

Alternate silviculture systems, such as small patch clearcuts, may become important in the development of sustainable forest management strategies in aspen forests. A study was initiated in a 64-yr-old trembling aspen (Populus tremuloides Michx.) stand in Meadow Lake Provincial Park, Saskatchewan to determine changes in nutrient dynamics and secondary succession following patch clear-cutting. One hectare replicated patch cuts were logged in the winter of 1993–1994. There was no site preparation following harvest. Annual vegetation, regeneration and soil and plant nutrient data were collected annually, 1 yr prior to, and 3 yr following harvest. Aspen regeneration was 48 375 stems ha−1 2 yr after treatment. Stand (alpha) diversity of the understory was not affected by harvesting, although annual species turnover (beta diversity) increased slightly after harvest. There was an increase in aspen foliar nitrogen (N) for 2 yr following harvest. Soil nutrient concentrations did not differ between patch cut and un...

SOIL NUTRIENT DYNAMICS IN A BOREAL MIXEDWOOD CUTOVER FOLLOWING THE APPLICATION OF HEXAZINONE

Large-scale human disturbances, primarily harvesting and site preparation, are recent and increasingly frequent activities in the Boreal Mixedwood, and potential impacts on long-term site productivity are unknown. A 7-yr experiment was carried out in a clear-cut Boreal Mixedwood forest to assess the effect of the herbicide hexazinone on soil nutrient dynamics. A completely randomized design with three herbicide treatments (0, 2, and 4 kg of active ingredient (a.i.) per hectare applied as Pronone 10G) and five replicates per treatment was established. The surface organic horizon (L-H) and three mineral horizons (Ah, Ae, and Btnj horizons) were sampled for five years: one year prior to the herbicide application and during the first, second, third, and sixth year after the herbicide was applied. Littertraps and lysimeters were installed and samples collected for the first three years of the study. Total biomass decreased and N concentrations increased in litterfall for at least 2 yr following the application of hexazinone. Other elemental concentrations were affected only in the year of application. Concentrations of ammonium (NH4+-N) and nitrate (NO3−-N) in the L-H of the hexazinone treatments were higher relative to the control. Extractable phosphorus (P), sulfur (S), and potassium (K) in the L-H of the herbicide treatments were lower by as much as 25%. These differences persisted for the duration of the study. No changes in extractable calcium (Ca) and magnesium (Mg) were found. Elevated concentrations of NH4+-N and K were measured in the Ah and Ae mineral horizons of the highest herbicide treatment, but total soil nutrient pools remained unaffected by the herbicide treatments. Reduced plant uptake of nutrients and the indirect impact of changes to the vegetation on soil mineralization–immobilization processes resulted in the differences in the available nutrient concentrations of the L-H horizon. The short-term results (6 yr) following the hexazinone application indicate that there was little change to the total nutrient pools and that the potential loss of nutrients at this site was minimal.