FLORA (2004) 199 491 Photosynthetic and growth responses to fire of the subtropical- temperate grass, Spartina argentinensis Parodi Susana R. Feldman 1, *; Vilma Bisaro 2 & Juan Pablo Lewis 3 1 Biología & CIUNR , Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, CC 14 s2125zaa Zavalla, Argentina 2 Estadística , Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, CC 14 s2125zaa Zavalla, Argentina 3 Ecología & CONICET, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, CC 14 s2125zaa Zavalla, Argentina * Author to whom correspondence should be addressed. e-mail: sfeldman@agatha.unr.edu.ar Submitted : Oct 2, 2003 · Accepted : Mar 29, 2004 Summary Fire is a common phenomenon in grasslands but there is little experimental evidence of the mechanism involved in the rapid recovery of the plant growth. We tested under controlled conditions the hypothesis that after fire Spartina argentinensis leaves that restart growing have high photosynthetic rates. Photosynthetic rates and emergence of leaves and culms were registered. Initial photosynthetic rates were higher among plants which restarted growth after fire or clipping than in control ones, without effect of different water availability. High photosynthetic rate values remained during two months after fire or clipping treat- ments though then affected by water availability, and thereafter started declining towards the end of season. From January onwards no differences among treatments were detected except that control plants under water stress conditions had lower pho- tosynthetic rates than all others. Leaf and culm emergence were promoted by both fire and clipping treatments. Though affect- ed by water availability, burned and clipped plants had the highest percentages of living tissues at the end of the experiment. Considering photosynthetic and growth responses after fire it can be concluded that burning is a regular component of the sub- tropical-temperate S. argentinensis habitat, among the South American grasslands. Key words : clipping, culm and leaf emergence, disturbance, grasslands, photosynthetic rate, water stress Introduction Spartina argentinensis Parodi is the dominant species of tall grasslands that cover large areas of land up to several millions hectares in Argentina (Cabrera & Willink 1973). According to Mobberly (1956), S. argentinensis is the same species as S. spartinae (Trinius) Hitchcock which, therefore, has a vicarious distribution with an area around the Gulf of Mexico and another in Northern Argentina and Paraguay. But as Burkart (1969) claimed, S. spartinae is a tautologic denomination, therefore anyway invalid according to the International Botanical Nomenclature Code. Structure and floristic characteristics of S. argenti- nensis grasslands have been extensively analyzed (Collantes & Lewis 1980 ; Lewis et al. 1985, 1990 a, b; Stofella 1995). These communities tend to be mono-especific due to the strong dominance of S. argentinensis, favored by the harshness of the edaphic environment (Lewis et al. 1990 b). In these grasslands, fire is a recurrent disturbance, it is a process that leads to total or partial destruction of biomass (Grime 1979). But after fire these grasslands recover their canopy rapidly even during droughts (pers. obs.). There is no information about S. argentinensis response upon fire besides the empiric knowledge that the plant resprouts 0367-2530/04/199/06-491 $ 30.00/0 * Corresponding author : Susana R. Feldman, Biología & CIUNR, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, CC 14 s2125zaa Zavalla, Argentina, e-mail: sfeldman@agatha.unr.edu.ar Flora 199, 491– 499 (2004) http://www.elsevier.de/flora