ALBARIÑO Ricardo Javier
Leaf litter breakdown in Patagonian streams: native vs. exotic trees and the effect of invertebrate size
ALBARIÑO, R.J.; BALSEIRO, E.G.
AQUATIC CONSERVATION-MARINE AND FRESHWATER ECOSYSTEMS
John Wiley & Sons, Ltd.
Lugar: Chichester; Año: 2002 vol. 12 p. 181 - 181
Nothofagus native forest in South Andes is being progressively substituted by forestation with rapid growth exotic trees, mainly Pinaceae species. The effect on stream processing dynamics is explored through in situ experiments. We analysed the effects of leaf litter quality and macroinvertebrate size on in situ litter breakdown. Experiments were run in litter bags which allowed access of macroinvertebrate fauna in streams running through a dense forest of the deciduous Nothofagus pumilio. In Experiment 1, we measured the decay rates of N. pumilio leaves and Pinus ponderosa needles during an autumn-winter period. N. pumilio decayed two times faster than P. ponderosa (P<0.01). Shredders fed only on N. pumilio leaves. Total macroinvertebrate abundance colonising both treatments was similar, however, the biomass was higher in the N. pumilio treatment. Large shredders were only found colonising N. pumilio leaves. Since no decay due to shredders was observed in P. ponderosa, the presence of macroinvertebrates in these litter bags was related to refuge and feeding on FPOM-biofilm resources. In Experiment 2, N. pumilio leaf litter was exposed in order to allow (open bags) or restrict (closed bags) access of invertebrates. The invertebrate assemblage in open bags showed the similar pattern observed for N. pumilio in the first experiment. Gathering-collectors were generally smaller and dominant in number while shredder biomass was higher in open bags as a result of its high individual biomass. Although N. pumilio decayed faster when the whole size spectrum of macroinvertebrates colonized the bags (P<0.01), feeding signs of small shredder were observed in closed bags, therefore its role on leaf litter breakdown in Andean streams should not be neglected. As a combined result of both experiments it can be predicted that the whole litter processing mechanism would be affected, as consequence of the substitution of the native forest by exotic pine forestation.