INVESTIGADORES
GARIBALDI Lucas Alejandro
congresos y reuniones científicas
Título:
Impact of introduced herbivores on plant biodiversity and ecosystem function in cool-temperate Patagonian forests.
Autor/es:
PIAZZA, M. V.; GARIBALDI, L. A.; KITZBERGER, T.; CHANETON, E. J.
Lugar:
Londrés
Reunión:
Congreso; INTECOL; 2013
Institución organizadora:
http://eventmobi.com/intecol2013/agenda/34843/183134
Resumen:
The introduction of large exotic herbivores constitutes a major threat
to the conservation of the few remaining forested regions that have been
spared from intensive logging. Large-herbivore effects on plant
biodiversity and key ecosystem processes have been extensively
documented in grasslands and savannas. Less is known about the impact of
introduced grazers on understorey plant communities and the functioning
of native forest ecosystems. Herbivory effects on plant diversity and
species composition have been found to vary along gradients of primary
productivity and resource availability. But how concomitant effects on
carbon and nutrient cycling might change along environmental gradients
remains largely untested. Here we examine the long-term effects of
introduced domestic herbivores on understorey plant composition, species
diversity and litter decomposition in cool-temperate forests of
southern South America. Our study compared historically (>50 years)
grazed and ungrazed sites (n = 5) paired along a region-wide moisture
gradient (PP = 1400?1800 mm/year; PP/PET = 2.5?4.5) in Nahuel Huapi
National Park, northwestern Patagonia, Argentina. Nothofagus dombeyi
was the main canopy species across all sites. Vegetation sampling and
litterbag decomposition experiments were replicated for three plots
nested within sites. Data were analysed using hierarchical mixed-effect
models. Compositional dissimilarity (Bray-Curtis index) between grazed
and ungrazed sites was generally greater than 60%, and increased with
increasing environmental moisture. Large herbivores reduced woody plant
cover (50%) and species evenness (30%) throughout the moisture gradient,
but there was no overall consistent effect on plant species richness
per site. In addition, grazing reduced species diversity (40%) within
the leaf-litter pool, which contained a greater proportion of N. dombeyi leaves in grazed than in ungrazed sites. Decomposition rate of N. dombeyi
leaf litter over 18 months was higher in ungrazed than in grazed sites,
irrespective of site moisture. Further, the leaf-litter pool of
understorey species from ungrazed sites decomposed faster than the
corresponding litter pool of grazed sites, but only when incubated in
ungrazed forests towards the drier end of the gradient. Our results show
that the presence of domestic herbivores altered understorey community
structure and diversity, which resulted in a significant functional
shift in the litter pool composition. Long-term increase in large
herbivore densities also decelerated organic matter decomposition, by
primarily modifying the forest soil environment rather than the quality
of aboveground litter inputs. Importantly, grazing-induced changes in
forest biodiversity and ecosystem function were not restricted to
certain environmental conditions, but were manifested across a
broad-scale moisture gradient.