Interactions between resources and abiotic conditions control plant performance on subarctic coastal dunes.

Both abiotic conditions and resource levels affect the performance of plants on coastal dune systems. On the foredune, environmental factors are particularly limiting for plant growth and these vary along a short topographical gradient, from the foot to the ridge. On subarctic coastal dunes in northeastern Canada, this topographical gradient is paralleled by a plant sequence that typically involves Honckenya peploides, Elymus mollis, and Lathyrus japonicus. In this study, field nutrient additions were carried out to evaluate the importance of N and/or P limitation on foredune plant performance. Also, glasshouse experiments were done to determine the significance of interactions between substrate resources (i.e., nutrients and water), and between substrate resources (i.e., nutrients) and an abiotic condition (i.e., salt spray) on the growth of a dune species. Field nutrient additions did not result in any significant increase in plant biomass, although nutrients were accumulated in the rhizomes of all three species present on the foredune and in the aboveground tissues of Elymus. Glasshouse experiments on Elymus showed that nutrient addition could increase plant biomass. However, water availability and salt spray interfered with nutrient use by the plants. I suggest that such interactions between resources and abiotic conditions may significantly affect plant performance and plant sequence on the foredune of coastal dune systems.