IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Can livestock grazing prevent species diversity loss from fertilizer addition in highly-productive grasslands?
Autor/es:
CHANETON, E.J.; YAHDJIAN, L.; TOGNETTI, P.; GRAFF, PAMELA
Lugar:
Baltimore, Maryland
Reunión:
Congreso; 100th Annual Meeting of the Ecological Society of America; 2015
Institución organizadora:
Ecological Society of America
Resumen:
Background/Question/MethodsNative grasslands are increasingly subjected to anthropogenic nutrient inputs, especially from fertilizer additionaimed at increasing biomass production for domestic animals. This practice may have, at least, two unwantedconsequences from a biodiversity standpoint. First, it has been shown that fertilization often decreases plantspecies richness in productive herbaceous systems through a reduction in light availability. Second, elevatednutrient loads may facilitate community dominance by invasive exotic species. Here we asked whetherseasonal grazing by domestic livestock ameliorates the negative impact of fertilization on grassland speciesdiversity. We also tested whether nutrient additions differentially altered diversity of dominant and subordinatespecies, and of native vs exotic species. The study was conducted in a highly-productive grassland in theFlooding Pampa of eastern Argentina. The design was a 2 x 2 factorial with grazing exclusion and fertilizationas main effects. Fertilizer (NPK) was applied three times a year to 5 x 5 m plots, paired with unfertilized controlplots, and established within 6 exclosures and in the adjacent grazed grassland (total = 24 plots). Diversity wasestimated by the number of species (richness) and the reciprocal of Simpson?s dominance index, bothcalculated from 1-m2 species cover data in spring and summer.Results/ConclusionsGrazing exclusion had a strongly negative effect on plant diversity (40%) and promoted dominance by exoticperennial grasses. Fertilizer addition (first year) similarly reduced plant richness in grazed and ungrazed plotsby nearly 5 species/m2, which represented a 20% loss in richness, relative to pre-treatment levels. Fertilizationfurther increased community dominance (decreased Simpson?s diversity) in the absence of domestic livestock,but had only a small effect on dominant species diversity in grazed grassland. Our results indicate thatseasonal grazing ameliorated the loss of diversity induced by fertilizer addition among dominant plant species,presumably by reducing biomass production and increasing light availability to least competitive species.However, grazing by domestic herbivores could not prevent the significant loss of total species richness thatoccurred after just one year of fertilization. Many such species were subordinate and rare native grasses andforbs that might contribute to ecosystem functions in the long term.