Tree productivity and successional status in Quebec northern hardwoods

Few studies have sought to understand the growth characteristics of tree species in order to explain the observed patterns of succession. This study seeks to determine the successional status of hardwood species in a secondary succession, to analyze their productivity and to examine the existing relationships between these two aspects. The age, production and biomass of 3273 stems were estimated in 34 stands distributed along a stand age gradient in south-western Quebec. The successional status of a species was determined bg comparing its abundance with stand age in a contingency table. Linear regressions of the logarithm of the age of trees with the logarithm of the aerial biomass (log [B]), the logarithm of the net primary production (log[NPP]) and the relative biomass increment (NNP/B) were established for each species. An analysis of covariance allowed the separation of statistically different species regression curves. Sugar maple (Acer saccharum? Marsh.), American beech (Fagus grandifolia Ehrh.) and eastern hemlock (Tsuga canadensis [L.] Carr.) are indicator species of old stands; bitternut hickory (Carya cordiformis [Wang] K. Koch), white ash (Fraxinus americana L.), butternut (Juglans cinerea L.), black cherry (Prunus serotina Ehrh.), white elm (Ulmus americana L.) and red elm (Ulmus rubra Muhl.) are mostly found in young stands. Ironwood (Ostrya virginiana [Mill.] K. Koch) is a ubiquitous species, found in stands of ail ages. Analysis of the relationships between tree age and B,NPP and NPP/B revealed that the more a species is capable of rapidly increasing its biomass at a young age, the less it is able to sustain this growth with increasing age. This growth trade-off relationships ordered species along a gradient of productivity patterns closely Linked to the observed stand age gradient.