Effects of livestock exclusion on density, survival and biomass of the perennial sagebrush grass Hymenachne pernambucense (Poaceae) from a temperate fluvial wetland

MAGNANO, ANDREA L.; NANNI, ANALÍA S.; KRUG, PAMELA; ASTRADA, ELIZABETH; VICARI, RICARDO; QUINTANA, RUBÉN D.

ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY

GAUTHIER-VILLARS/EDITIONS ELSEVIER

Lugar: Paris; Año: 2018 vol. 86 p. 72 - 78

1146-609X

In Argentina, the intensification of soybean production has displaced a substantial proportion of cattle ranchingto fluvial wetlands such as those in the Paraná River Delta. Cattle grazing affects structure and dynamicsof native forage plants but there is little information on this impact in populations from fluvial wetlands. Thisstudy addresses the effect of cattle ranching on density, survival, mean life-span and aerial biomass of Hymenachnepernambucense (Poaceae), an important forage species in the region. The study was carried out monthlyfor one year in permanents plots subject to continuous grazing and plots excluded from grazing in the MiddleDelta of the Paraná River. In plots excluded from grazing, tillers showed significantly higher population densityand survival, and a two-fold increase in mean life-span, while continuous grazing decreased survival of cohorts.The largest contribution to tiller density in ungrazed and grazed populations was made by spring and summercohorts, respectively. Total and green biomass were significantly higher in the ungrazed population, with highestdifferences in late spring-early summer. Cattle grazing affected the relationship between tiller density and greenbiomass suggesting that cattle prefer sprouts because they are more palatable and nutritious than older tissue.