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

KRUG, CECILIA P.; QUINTANA, RUBÉN D.; NANNI, ANALÍA; KRUG, CECILIA P.; VICARI, RICARDO; QUINTANA, RUBÉN D.; NANNI, ANALÍA; VICARI, RICARDO; MAGNANO, ANDREA; ASTRADA, ELIZABETH; MAGNANO, ANDREA; ASTRADA, ELIZABETH

ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY

GAUTHIER-VILLARS/EDITIONS ELSEVIER

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

1146-609X

In Argentina, the expansion of the agricultural frontier due to the intensification of soybean production has displaced a substantial proportion of cattle ranching activity to fluvial wetlands such as those in the Parana River Delta region. Cattle pressure may probably affect native forage species and it appears of particular interest to investigate the impact of herbivory on their demographic parameters and population dynamics, mainly because there is little information on this issue in fluvial wetlands at the population level. We studied the effect of cattle ranching on the aerial biomass, survival, density and mean life-span of tillers of Hymenachne pernambucense, an important forage species in the region. The study was carried out monthly during one year on plots subject to continuous grazing and plots excluded from grazing at a cattle ranch in the Middle Delta of the Parana River, Argentina. In plots excluded from grazing, tillers showed higher values of population density and survival, and a two-fold increase in mean life-span, while continuous grazing led to a decrease in the survival of winter, spring and summer cohorts. The largest contribution to tiller density in the ungrazed and the continuously grazed populations was made by spring and summer cohorts, respectively. Total and green biomass estimates were significantly higher in the ungrazed population, with highest differences in late spring-early summer. Information on the population dynamics of important forage species in the Delta region is valuable for both producers and policymakers, as it helps to develop strategies for resource use, in the frame of sustainable management of livestock production. Our results suggest that livestock rotation to other pastures during spring may favour tiller regrowth in this season leading to an increase in biomass and forage quality during summer.