Unusual effect of controlling aboveground competition by Ledum groenlandicum on black spruce (Picea mariana) in boreal forested peatland

Abstract

Poor growth of black spruce (Picea mariana (Mill.) BSP) has been associated with the presence of Ledum groenlandicum L. (Ledum) on some sites in the eastern boreal forest in Canada. To increase black spruce productivity on lowland sites, a study was carried out to test the effect of mechanical control of Ledum (by clipping) on black spruce growth on forested peatland in northwestern Quebec. We compared the growth and foliar nutrient concentrations of advance-regeneration black spruce seedlings with and without Ledum control. Contrary to our expectations, our results showed that 3-year control of aboveground competition by Ledum decreased rather than increased black spruce growth and had no effect on foliar nutrient concentrations. Ledum grows on a variety of site types; therefore, the mere presence of this species does not necessarily indicate that there will be a problem with conifer regeneration (growth and germination).