Environmental resource interactions affect red raspberry growth and its competition with white spruce

Multifactor experiments were used to study the effects of (1) shade, moistu re, and nutrients on above- and below-ground biomass production of red rasp berry (Rubus idaeus L.) and (2) intra- versus inter-specific competition fo r light, nitrogen, and space in interplantings of raspberry and white spruc e (Picea glauca (Moench) Voss) seedlings. Interactive effects among the man ipulated resources on seedling growth were common. Raspberry biomass increa sed with increasing moisture and nutrients or with added nitrogen when nitr ogen was the only nutrient manipulated. Seventy-three percent shade reduced raspberry biomass production, while production under full sun and 30% shad e was similar. Raspberry shoot/root ratio increased with increasing nutrien ts and shade but decreased with age. In mixed plantings with spruce, when n itrogen was added, raspberry biomass and shoot/root ratio increased at the expense of spruce, while the shoot/root ratio decreased with shade in low-n itrogen plots. Spruce height growth was not affected by light level, nitrog en addition, or competition type; however, spruce diameter and biomass prod uction decreased with competition from both raspberry and spruce and increa sed with increasing growing space and in low-nitrogen shaded plots where ra spberry was less common.