Challenging growth-survival trade-off: a key for Acer negundo invasion in European floodplains?

We compared the performances of juvenile Acer negundo with those of native species to assess how this species has invaded intermediate habitats along European riparian successional gradients. In the middle Rhone floodplain (France), we measured survival and growth of transplants of the invasive and of three native tree species from contrasted successional status within forests and in experimental gaps and at three positions along a riparian gradient: (i) a highly disturbed Salix-Populus stand, (ii) a moderately disturbed stand dominated by the invasive Acer, and (iii) a mature Fraxinus community. Acer's growth in the gaps was as high as that of the two native early-successional species, Salix and Populus, and higher than that of the native late-successional Fraxinus. In contrast, Acer survived as well in the shadiest understory conditions of the Fraxinus community as did Fraxinus and better than the two early-successional species. Inconsistent with the resource trade-off of succession theory, Acer showed both a high survival in the shade and a high growth in full light. This particular suite of traits shared with other invasive and native Acer species could be an example of adaptive plasticity that certainly represents an advantage to give it a competitive advantage over native species.