Spatial and temporal variability during primary succession on tropical coastal sand dunes

We studied primary succession on mobile tropical coastal sand dunes over an 8-yr period. Every six months, we monitored changes in species composition and sand movement in permanent quadrats located on the windward slopes. th e arms and the crests. Our results indicate that sand movement decreased ov er time but was significantly higher on the slopes and crests than on the a rms. In all cases. there were seasonal fluctuations in sand movement which increased during the period with strong northerly winds and decreased durin g the rainy season. Sand movement was significantly correlated with species distribution. Plant cover and species richness increased at all three loca tions. Diversity increased on the slope, decreased on the arms and remained unchanged on the crest. However, the equitability values indicated the dom inance of a few species, especially at the end of the study period. Tempora l trends and species turnover rates differed among locations. Species turno ver occurred first on the arms (1994), then on the crests ( 1998) and lastl y on the slopes (at the end of the study period). In all cases the tall gra ss, Schizachyrium scoparium var. littoralis. became dominant over the endem ic legume, Chamaecrista chamaecristoides var. chamaecristoides. Similar to temperate dunes, primary succession on tropical sand dunes was spatially an d temporally heterogeneous.