Effects of pine plantations on coastal gradients and vegetation zonation in SW Spain

Abstract

One of the most important anthropic disturbances on Mediterranean coastal dunes is the plantation of pine trees. However, the impact of coastal pine plantations on environmental gradients and on the spatial zonation of vegetation has received little attention. I analysed the spatial pattern of vegetation along sea-inland gradients from the foredune inland in three dune systems at the Gulf of Cádiz (SW Spain) to assess the effects of pine plantations on both the environment and the plant communities. In this study, I focus on the effects of the “Wooded dunes with Pinus pinea and/or Pinus pinaster” European habitat (code 2270) on the “Coastal dunes with Juniperus spp.” European habitat (code 2250), both considered as priority habitat, and which in many cases compete for the same range of the spatial zonation of vegetation.CCA showed that the distance to the shoreline was the main factor controlling the composition of sand dune communities, even when several environmental gradients were modified by the presence of pine trees. Boundary Analysis detected several stretches with a characteristic vegetation that correspond to dune geomorphological zones. However, the plantation of pine trees on coastal dune ridges modified salt spray deposition and sand mobility landward, the main factors causing vegetation zonation in coastal dunes, making characteristic species of semifixed habitats such as Armeria pungens and Artemisia chritmifolia disappear. Pine plantations also shade and reduce wind flow producing negative effects on the growth and reproduction of the heliophilous and dioecious wind-pollinated Juniperus macrocarpa. Therefore, Pinus pinea may be considered as a physical ecosystem engineer in coastal sand dunes in spite of not being a species well adapted to salt spray and sand mobility, in contrast to J. macrocarpa. A better understanding of the ecological and geomorphological coastal processes is needed in order to promote better management and restoration actions of the coastal dune habitats to preserve the rich and specialized flora that inhabits these ecosystems, including Juniperus macrocarpa.