The relationship between vegetation dynamics and water table in tropical dune slacks

Inundation of tropical dune slacks is an irregular phenomenon produced by consecutive years with high precipitation and also by intense tropical storms. Our hypothesis was that the distribution, structure and composition of vegetation in tropical dune slacks have changed over time as a result of various factors, principally their topographical position with respect to the water table, frequency and duration of inundation, and historical fluctuations in climate. We tested this hypothesis in two different slacks that represent the slack community at the study site. Inundation caused changes in species composition and distribution, as well as in vegetation structure. In one slack, inundation was considered as disturbance because its intensity increased when areas remained inundated for longer periods of time, causing death of vegetation cover and favouring invasion of more aggressive, secondary species (Pluchea odorata, Ambrosia artemisiifolia, Panicum maximum). When inundation lasted less than three months, rhizomatous herbs remained (Cyperus articulatus, Lippia nodiflora, Hydrocotyle bonariensis) inhibiting the succession process. The results suggest that the different degrees of inundation and the irregular frequency and intensity of inundation in the slacks under study, have favoured different successional tendencies.