Environmental relationships of vegetation patterns in saltmarshes of central Argentina

We describe vegetation-environment relationships in the saltmarshes of central Argentina. Gradient analysis (Detrended canonical correspondence analysis, DCCA) was performed involving 14 parameters of the groundwater that account for most of the variation in plant communities. We used a stepwise multivariate procedure to classify the vegetation data into 8 clusters, named according to the most abundant characteristic species:Chloris canterai, Cynodon dactylon, Distichlis, spicata, Spartina densiflora andPaspalum vaginatum clusters, containing relevés of tall grassland communities, andAtriplex undulata, Cyclolepis genistoides andHeterostachys ritteriana clusters, containing relevés from scrub. Our interpretation of DCCA ordinations suggests that vegetation pattern is primarily related to a salinity-moisture gradient. There is a strong relationship between vegetation type and the amount of salt in the groundwater and the pattern of its variation during the year. The depth of the groundwater and the conditions of submersion are also related to the compositional variation of the vegetation. Although flooding causes some differences between sites, the most important discriminant variable, and therefore the best predictor of floristic variation, is salinization.