Allometric exponents as a tool to study the influence of climate on the trade-off between primary and secondary growth in major north-eastern American tree species

BACKGROUND AND AIMS: Trees invest in both primary (e.g. height) and secondary (e.g. diameter) growth. The trade-off between these investments varies between species and changes with the tree growing environment. To better establish this trade-off, readily available allometric exponents relating height to diameter at breast height (γ(h,dbh)) and stem volume to diameter at breast height (α(v,dbh)) were simultaneously studied. METHODS: Allometric exponents α(v,dbh) and γ(h,dbh) were obtained from 8893 individual tree stem analyses from two broadleaved species (Betula papyrifera, Populus tremuloides) and four conifers (Picea glauca, Picea mariana, Pinus banksiana, Abies balsamea) in the temperate and boreal forests of the province of Quebec, Canada. α(v,dbh) and γ(h,dbh) were related to tree age, stand density index (SDI), and mean temperature (TGS) and total precipitation (PGS) of the growing season. KEY RESULTS: α(v,dbh) and γ(h,dbh) were found to be invariant with PGS and positively related to SDI and TGS for all species except Pinus banksiana. The parameter values associated with SDI and TGS were of higher value for conifers than for broadleaved species. CONCLUSIONS: This suggests that conifers and broadleaved species have different growth patterns. This could be explained by their different mode of development, the conifer species having a stronger apical dominance than broadleaved species. Such results could be further considered in allocation studies to quantify future carbon stocks in managed forests.