© 2005 Heron Publishing—Victoria, Canada
Carbon budget for Scots pine trees: effects of size, competition and site fertility on growth allocation and production
Petteri Vanninen (1, 2, 3) and Annikki Mäkelä (1)
1. Department of Forest Ecology, P.O. Box, FIN-00014 Helsinki University, Finland / 2. Saima c/o Department of Teacher Education, Box 55, 57101 Savonlinna, Finland / 3. Corresponding author (petteri.vanninen@helsinki.fi) / Received June 17, 2003; accepted July 11, 2004; published online November 1, 2004
Summary
Time series of carbon fluxes in individual Scots pine (Pinus sylvestris L.) trees were constructed based on biomass measurements and information about component-specific turnover and respiration
rates. Foliage, branch, stem sapwood, heartwood and bark components of aboveground biomass were measured in 117 trees sampled
from 17 stands varying in age, density and site fertility. A subsample of 32 trees was measured for belowground biomass excluding
fine roots. Biomass of fine roots was estimated from the results of an earlier study. Statistical models were constructed
to predict dry mass (DW) of components from tree height and basal area, and time derivatives of these models were used to
estimate biomass increments from height growth and basal area growth. Biomass growth (G) was estimated by adding estimated biomass turnover rates to increments, and gross photosynthetic production (P) was estimated by adding estimated component respiration rates to growth. The method, which predicts the time course of G, P and biomass increment in individual trees as functions of height growth and basal area growth, was applied to eight example
trees representing different dominance positions and site fertilities. Estimated G and P of the example trees varied with competition, site fertility and tree height, reaching maximum values of 22 and 43 kgDW year–1, respectively. The site types did not show marked differences in productivity of trees of the same height, although height
growth was greater on the fertile site. The G:P ratio decreased with tree height from 65 to 45%. Growth allocation to needles and branches increased with increasing dominance,
whereas growth allocation to the stem decreased. Growth allocation to branches decreased and growth allocation to coarse roots
increased with increasing tree size. Trees at the poor site allocated 49% more to fine roots than trees at the fertile site.
The belowground parts accounted for 25 to 55% of annual G, increasing with tree size and decreasing with site fertility. Annual G and P per unit needle mass varied over the ranges 1.9–2.4 and 3.5–4.0 kgDW kg–1, respectively. The relationship between P and needle mass in the example trees was linear and relatively independent of competition, site fertility and age.
Keywords:
biomass, carbon balance, needle efficiency, Pinus sylvestris, structure.
