Primary colonisation of mudflat estuaries by Spartina maritima (Curtis) Fernald in Northwest Spain: vegetation structure and sediment accretion

Spartina maritima in Northwest Spain follows a colonisation pattern similar to that described from other latitudes and other Spartina coloniser specie s. After the establishment of vegetative fragments on the mudflat, rhizomes grow centrifugally forming rounded patches that act like sediment traps, b ecoming dome-shaped due to the accumulation of sediment towards the centre of the patch. Patch size has been marked as one of the main determinants of the accretion due to the presence of Spartina. We propose a model to relat e patch size and sediment accretion at the first stages of colonisation, wh ich seems to be logarithmic rather than linear as had been previously sugge sted. Other factors such as distance to water exchange source and elevation prior to Spartina colonisation have proved to be important accretion deter minants. Shoot size within patches increased from the edge towards the cent re, while shoot density showed a complex distribution characterised by a se ries of concentric belts of different densities, with the lowest density at the centre of the patch. Despite, the higher elevation and the lower Spart ina density at the centre of the patches, no other species have been found colonising those spots. (C) 2001 Elsevier Science B.V. All rights reserved.