The Effects of Fertilization and Herbivory on the Phenology of the Understory Vegetation of the Boreal Forest in Northwestern Canada

Abstract

Environmental conditions associated with climate change, such as earlier snowmelt, warmer spring temperatures, and increased soil mineralization, have resulted in shifts in the timing of plant phenological events. We assessed the effects of fertilizer and herbivory on the phenology of 7 plant species from a boreal forest understory using long-term experimental plots in the southwest Yukon. Fertilizer and fencing treatments were initiated in 1990, and discontinued in half of each plot in 2000. There were few effects on phenology of either fertilizer or fencing. In some species, fertilizer affected the final phenological stage reached, but the presence and direction of the effect was species-dependent. Epilobium angustifolium was the only species where the timing of phenological stages responded to fertilization; early phenological stages were advanced with fertilizer. First leaf expansion for Arctostaphylos uva-ursi occurred earlier in fenced plots, although this effect disappeared in plots where the fencing treatment had been discontinued. We conclude that previously observed changes in species abundance with fertilizer treatments are likely not caused by changes in the phenology of these species, and are more likely due to fertilization imposed changes in vegetative growth.