Variation in aboveground and belowground biomass in progeny of selected stands of Pinus sylvestris

Abstract

Forest biomass studies not only range from estimation of timber standing mass to assessing biogeochemical cycles, but may also reveal genetic variation in growth and biomass allocation. In this study, we investigated differences in biomass accumulation and allometric relationships between tree diameter and biomass of above and belowground components in two populations of Scots pine (Pinus sylvestris L.) (progeny of clonal seed orchards) differing in stem growth. At a common tree diameter, populations differed in accumulated belowground biomass, but not in total tree or aboveground components' biomass. Populations also differed in the root:shoot ratio and proportional allocation of biomass into stems. However, proportional allocation to stem mass decreased from smaller to larger trees, contrary to branch and foliage, which likely reflected a response to competition in the stand. The allometric equations predicted well the total tree, aboveground, and stem biomass independently of population, but separate equations were required for estimation of belowground biomass for the two populations. These results suggest that total stand and aboveground biomass in young Scots pine stands could be estimated without accounting for genetic component. Comparison of literature data with estimates obtained using our allometric equations indicate that equations were site-specific and should not be generalized to other sites, unless for rough approximation of aboveground biomass. More research is required for a more reliable assessment of genetic effect on allometric relationships for belowground biomass.