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

Abstract

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