CONICET | Buscador de Institutos y Recursos Humanos

Background and Aims. Flooding and grazing are major disturbances that simultaneously affect plant performance in many humid grassland ecosystems. We studied the effects of flooding on plant recovery from defoliation in two species: the grass Paspalum dilatatum, regrowing primarily from current assimilation, and the legume Lotus tenuis, which can use crown reserves during regrowth.Methods. Plants of both species were subjected to intense defoliation in combination with 15 days of flooding at 6 cm water depth. Plant recovery was evaluated during a subsequent 30 days growth-period under well-watered conditions. Plant responses in tissue porosity, height, tiller or shoot number and biomass of the different organs were assessed.Key Results. Flooding increased porosity both in P. dilatatum and L. tenuis, as expected in flood-tolerant species. In P. dilatatum, defoliation of flooded plants induced reductions in plant height, thus prevailing the prostrated-growth response typical of defoliated plants than the restoration of contact with atmospheric oxygen and most tillers remained submerged until the end of the flooding period. In contrast, in L. tenuis plant height was not reduced when defoliated and flooded, presenting a high proportion of shoots emerging above water (72%). In consequence, in the legume species, flooding plus defoliation did not depress plant recovery from defoliation, showing high sprouting and use of crown biomass during regrowth, whereas in the grass species it negatively affected plant recovery, achieving 32% lower biomass than plants subjected to flooding or defoliation as single treatments.Conclusions. The interactive effect of flooding and defoliation determines a reduction in the regrowth of P. dilatatum that is not detected in L. tenuis. In the legume, the use of crown reserves seems to be a key factor in plant recovery from defoliation under flooding conditions.