WELD-01-061

Soil Nutrients and Understory Species Associated with Lodgepole Pine (Pinus contorta) Forests in the Lower Boreal-Cordilleran Ecoregion of Alberta
Sponsor: 
Weldwood of Canada Ltd.
Lead Researcher: 
Kevin Szwaluk, Masters student, University of Calgary
Body: 
This study tested two hypotheses. The study considers whether there a relationship between nutrient levels (i.e. N, P, K, S, Mg, Ca, Fe, and Al) in the forest floor litter and uppermost mineral soil zone, and the height growth rate of lodgepole pine, and whether vegetation composition and abundance related to the availability of nutrients in the forest floor litter and uppermost mineral zone.

Forest floor litter, uppermost mineral soil zone nutrients and plant species were assessed for 42 lodgepole pine stands in the Lower Boreal-Cordilleran Ecoregion of Alberta. These stands were separated into three site index classes which represented a gradient from poor to better quality sites. Extractable nutrient levels in the forest floor and uppermost mineral zone were associated with site index classes. Other properties collected included understory species, thickness of forest floor and uppermost mineral soil horizon, humus form, soil texture, course fragment content, pH, and bulk density.

Properties of forest floor litter and uppermost mineral soil were found to be associated with lodgepole pine height growth. Regression equations based on plant species percent cover explained greater variance in site index properties than soil properties. The strongest models included both plant species cover and soil properties.