Project Code: WELD-01-073
Sponsor:Weldwood of Canada Ltd.

This study investigated how site and stand properties of different ecosites of the Weldwood Forest Management Agreement (FMA) area influence stand response to fertilizer treatments.

Study sites within unmanaged, fire-origin, immature lodgepole pine dominated stands, were established in the Upper Foothills natural subregion of the FMA. Ranging from subxeric to hygric and very poor to very rich, these sites encompassed typical site conditions under which stands of lodgepole pine grow. Two treatments of fertilizer (heavy – 400 kg N/ha; moderate – 325 kg N/ha) were applied to the study sites.

The heavy treatment elicited substantially greater response than the moderate treatment across the majority of stands where it was applied. Total nitrogen content of foliar samples was determined to be the most reliable and consistent measure of foliar response to fertilization. It was also found to be far more closely correlated with relevant stand characteristics, including productivity and volume, than needle weight. The driest and poorest sites exhibited the greatest frequency and magnitude of response. Given individual site characteristics, soil nutrient regime held the greatest influence over response, with stand productivity able to explain the greatest amount of variation in foliar response. In combination with ecosite, it is recommended that a primary filter is applied when selecting stands for potential fertilizer treatment. Several recommendations are made regarding potential for future research trials and considerations for operational fertilization.