Relationship between architecture and successional status of trees in the temperate deciduous forest

The architectural analysis of trees, as developed since the pioneering work of Halle & Oldeman in the 1960s and 1970s, allows the study of the develop mental pattern characteristic to each species in a global and dynamic persp ective of the tree. This leads to a fundamental question: is there a relati onship between architectural characteristics of a species and its successio nal status? The analysis of nine tree species from the deciduous temperate forest of southwestern Quebec reveals that such a relationship exists, main ly at the level of the alternation of organization plans (hierarchic and po lyarchic) during the growth of the trunk and the reiteration within the cro wn. Early successional species (Betula populifolia and Populus tremuloides) have a hierarchic architecture throughout their ontogenesis. The hierarchy of the branched system promotes a rapid growth of the trunk. The potential for total reiteration in the crown is very limited. Conversely, late succe ssional species (Acer saccharum, Fagus grandifolia and Tsuga canadensis) ha ve an architecture with several levels of organization. The alternation of hierarchic and polyarchic phases of development confers a greater shape pla sticity upon the tree, to the detriment of the speed of growth of the trunk . However, reiteration within the crown is common and abundant. This proces s increases the lateral spread of the crown, as well as it prolongs the lif e span of the tree itself. Mid-successional species (Ulmus americana, Fraxi nus americana, Tilia americana and Carya cordifornis) have architectural de velopment in between these two extremes. They combine a great hierarchy in the structure of the young tree with a potential for reiteration in the cro wn. Two growth strategies were identified among the late successional speci es, one facilitating growth in the shade and the other allowing the tree to benefit from increase in light in canopy gaps.