ABUNDANCE, GROWTH AND ALLOMETRY OF RED RASPBERRY (RUBUS-IDAEUS L) ALONG A NATURAL LIGHT GRADIENT IN A NORTHERN HARDWOOD FOREST

The effects of a natural light gradient on abundance, growth and allom etry of red raspberry (Rubus idaeus L.) was investigated in 1993 in a temperate deciduous forest (near Quebec city, Canada) in which 30% of total basal area had been removed in 1989. One hundred and three l-mz plots were sampled to evaluate red raspberry abundance along a light g radient ranging from 3 to 40% of above canopy photosynthetic photon fl ux density (% PPFD). No red raspberry was found under closed forest wh ere PPFD was less than 7%, whereas it was always present above 25% PPF D. Height growth (R(2) = 0.302, P < 0.001) and total biomass (R(2) = 0 .372; P < 0.001) in first-year stems were positively related to % PPFD . Strong allometric relationships were found between height, stem diam eter and biomass parameters. The proportion of the total biomass in st em, petiole and leaf did not change along the light gradient, This lac k of aboveground allocational plasticity may partially explain red ras pberry's inability to survive under low light levels.