Interactive effects of trampling and flooding on the growth of Lotus tenuis in grassland mesocoms of the Flooding Pampa

STRIKER GG, MOLLARD FPO, GRIMOLDI AA, INSAUSTI P, LEÓN RJC

Chascomús

Taller; IV Taller Interdisciplinario sobre Aspectos Genéticos, Moleculares y Fisioecológicos de Lotus spp. y sus Simbiontes; 2008

INTECH-CONICET

Flooding and trampling are two major disturbances affecting the vegetation of the Flooding Pampa. The continuous grazing regime and the periodic occurrence of floods determine the trample of the flooded grassland as a common situation. In these grasslands, which lack of native legumes of importance, the introduction and persistence of Lotus tenuis Waldst. & Kit. (syn. Lotus glaber Mill.) is desirable because increases the forage quality of the grassland. The objective of this work was to investigate the impact of flooding and trampling on plant cover and aerial biomass of the functional groups of graminoids and dicots, and of L. tenuis, growing in mesocosms of natural grassland. To this end, 20 soil monoliths supporting natural vegetation (=mesocosms of 0.8×0.5×0.35 m depth) were extracted and transferred to the experimental garden of the Faculty of Agronomy (UBA). Mesocosms were initially similar in floristic composition, soil cover, vertical distribution of the canopy and abundance of L. tenuis. After 45 days of acclimatization, mesocosms were subjected to a combination of trampling and flooding in a completely randomized design (n=5). The flooding lasted 40 days while trampling was made at the day 20 by covering 52% of the surface of the mesocosms. Flooding increased by two-folds the cover of graminoids (P