Growth and Biomass Partitioning Response of Northern Red Oak Genotypes to Shading and Grass Root Competition

Abstract

Abstract First-year biomass, biomass relative growth rate, and biomass partitioning among organs were compared among eight open-pollinated families of northern red oak (Quercus rubra L.) under crossed levels of light intensity (100% and 37% full sun) and grass root competition [presence and absence of grass roots (Poa pratensis L.)]. Ontogenetic patterns of biomass partitioning during the first year of seedling development were characterized by coefficients of the allometric equation Y = aXb. Grass root competition reduced seedling biomass at both levels of light intensity. Shading reduced seedling biomass in the absence of grass but had no effect in its presence. Total biomass and biomass relative growth rate differed among families, and family X environment interaction variance was negligible compared to family variance. Results suggest that families with superior juvenile growth rate under competition-free conditions will also have superior growth rate under at least some conditions of shading and root competition. Biomass partitioning to leaf area, and to shoot weight relative to root weight declined during seedling development. Both shoot-root ratio and leaf area ratio were greater in shaded compared to full sun environments, while the presence of grass root competition had an opposite effect on both ratios. Families differed in shoot-root ratio, and shoot-root ratios of families responded differently to grass root competition. However, family differences in biomass partitioning were not consistently related to family differences in growth rate in any environment. For. Sci. 36(2):293-303.