Relationship between vegetation dynamics and dune mobility in an arid transgressive coastal system, Maspalomas, Canary Islands

Abstract

This paper explores the relationship between vegetation dynamics and dune mobility in an arid transgressive coastal dune system, specifically the dune field ofMaspalomas (Gran Canaria, Canary Islands). The aim is to understand the strategies of colonization and survival that plant communities have developed in slacks that face dune advance. The relationship between plant colonization and dune migration was performed by following Tamarix canariensis and Traganum moquinii plants for several years. Morphological data about each individual as well as the distance of each plant to the dune weremeasured. A study of the colonization patterns developed by T.moquinii, T. canariensis, Cyperus laevigatus and Launaea arborescens communities was performed by analyzing the evolution of consolidated plant patches and adult plants in relation to the dune advance. This was achieved using digital orthophotos and spatial analysis from geographic information systems. Initiation of plant colonization over transgressive dunes occurs on bothwet and dry slacks. The results showthat both plant colonization and development of adult plants are largely related to dune mobility. Thus, survival of T. moquinii and T. canariensis plants under dune migration conditions is related to both distance to the dune front and plant height at the moment of burial. Distance from the dune front and plant height increases chance of survival. The dynamics of adult plants is also related to dune displacement rates. Thus, each community has different thresholds of resistance tomobility rates. The T. canariensis communitywithstands average rates higher than 3 m/year. Its arboreal structure allows this species to grow high enough to resist the advance of the dunes and burial. For the T.moquinii community, the population decreases gradually to eventually disappearwhen dune mobility rates exceed 4 m/year. The C. laevigatus community develops at dunemobility rates lower than 3 m/year, decreasing its surface area at higher rates. The L. arborescens community endures dune migration rates of at least 1.8m/year. However, different distances between the dune front and the vegetated area also significant factor, because these can compensate for the effects of displacement rates. Thus, the closer a vegetated area is to a dune front, the lower the rates of displacement must be to produce a greater reduction in the surface vegetation. Plant communities present two patterns of plant colonization to resist burial by sand, one vertical and the other horizontal. The horizontal pattern is employed by C. laevigatus and L. arborescens communities and consists of locating new generations of plants in progressive alignment with the dune front migration. The vertical pattern is employed by the T. canariensis community, and consists of increasing the heights of the plants. The T. moquinii community can utilize both patterns because it reacts positively to some degree of burial since it is located in areas where the dunes reach different heights.