The partitioning of net energy resources in two populations of Solidago canadensis during a single developmental cycle in southern Ontario

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Abstract
The partitioning of net energy resources among component organs was measured in two populations of vegetatively produced Solidago canadensis L. individuals on two abandoned pasture sites in southern Ontario. One population was invading a grass-dominated site of comparatively recent abandonment while the other population was well established on a site which was dominated by perennial forbs and which typified a late stage of secondary herbaceous succession. Early in the season there were differences in the proportional contribution of leaf and stem tissue to total new growth, but allometric analysis showed these differences to be a function of developmental stage. New roots emerged earlier in the invading population, which subsequently maintained a higher new root – shoot ratio. The relative growth of new roots was the same in both populations between July and mid-August. Reproductive effort (RE), consisting of both sexual and asexual components, was similar in both populations. Asexual RE was very small (1.5%), but rhizome length was longer in the invading population. It is suggested that rhizome length is determined principally by the size of the photosynthetic apparatus in late season when rhizome extension and leaf senescence are occurring simultaneously. An explanation for differential senescence rates is offered based on the size and density of Solidago clumps and the influence of these characteristics on light attenuation in the canopy.