Effects of fire on the structure and diversity of a Spartina argentinensis tall grassland

Question: What are the effects of fire on the structure and the diversity of a Spartina ar gentinensis tall grassland in the short and medium run. S. argentinensis is the dominant species of tall grasslands on inland marshes of the Chaco‐Pampean region (Argentina), where spontaneous or man‐made fires are very frequent. Location: Federico Wildermuth Reserve (31°57′S; 61°23′W), Province of Santa Fe, Argentina, an area never ploughed that supported cattle until its exclusion in 1988. Methods: Vegetation was surveyed in randomly placed permanent plots using the Braun‐Blanquet cover‐abundance scale. The data were analysed by multivariate methods (PCA and MRPP) for synthesizing information and testing hypotheses. Results: Fire did not have a long‐lasting effect on the tall grassland. There was only a temporarily reduction of cover‐abundance of S. argentinensis which allowed an increase in the number of accompanying species such as Heliotropium curassavicum, Pluchea sagittalis, and Verbena litoralis and of some naturalised or weed species, such as Melilotus alba and Cirsium vulgare, respectively. Fire increased diversity, which remained relatively high for two to three years. Three years after the fire there were no significant differences on the amount of litter accumulated on burned and unburned plots. Conclusion: Fire should be considered an intrinsic part of the dynamics of S. argentinensis tall grassland.