Doana mobile dunes: what is the vegetation pattern telling us?

摘要

In coastal dunes, changes in plant composition and vegetation pattern can reveal processes such as plant succession, dune stabilization or reactivation. With that goal, I sampled plant species composition, topography and sand mobility along 4 parallel transects perpendicular to the coastline in the mobile dune system of Doana. I used Split Moving Window to locate boundaries between plant communities along transects. To assess the main trends in variation, data of plant cover from all transects were subject to multivariate ordination analysis. Plant composition and geomorphological traits allowed to distinguish several stretches along all transects. Multivariate analyses reflected two different trends, plant succession and dune stabilization. High cover of Halimium halimifolium in the primary dune slack was consistent with the lack of new deposits of fresh sand. Growth of pine trees facilitated the colonization of the dune tail by H. halimifolium in a positive feedback. Although several studies have pointed out a decrease in the advance rates of dunes due to an increase in plant cover, the present results suggest that the increase in plant cover in the outer dunes is due to the stabilization of the secondary dune. Therefore, vegetation pattern evidenced a process of dune stabilization, which may produce loss of original plant communities and heterogeneity of dune landscapes.