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Universidad de Buenos Aires (2015)

Effect of functional diversity of insect hervibores on carbon and nutrient cycling in Patagonian forests

Oleiro, Marina Inés

Titre : Effect of functional diversity of insect hervibores on carbon and nutrient cycling in Patagonian forests

Efecto de la diversidad funcional de insectos herbívoros en el ciclado de carbono y nitrógeno en bosques andino-patagónicos

Auteur : Oleiro, Marina Inés

Université de soutenance : Universidad de Buenos Aires

Grade : Doctor 2015

Résumé
Biodiversity loss affects trophic interactions and may thus change the fluxes of energy and nutrients within ecosystems. The aim of this thesis was to investigate the effect of functional diversity of folivorous insects on litter decomposition and nitrogen cycling in Nothofagus pumilio forests in northern Patagonia. Chemical (C:N) and physical (toughness) analyses showed that prior insect damage improves leaflitter "quality" as a substrate for decomposition, relative to undamaged leaf litter. This effect depended on the insect guild (leaf chewer, miner or tier). Field and laboratory experiments indicated that herbivory accelerated litter decomposition, but leaf damage diversity had no significant effect. In a microcosm experiment, both the physical damage of senescing leaves and deposition of insect frass increased rates of decomposition and net N mineralization. Folivore guild identity did not affect decomposition rate but enhanced N release from litter. Litter damaged by miners and tiers released more N than undamaged leaves or leaves damaged by chewing insects. Mass deposition of volcanic ashes after the 2011 eruption of the Puyehue- Cordón Caulle complex masked any differences in decomposition between intact and insect damaged tree leaves. Yet, insect-mediated effects on litter N dynamics remained significant even beneath a thick ash layer. Laboratory and field evidence suggests that volcanic ashes limited the activity of soil mesofauna. This thesis shows that the functional composition of folivorous canopy insects can regulate key processes for C and N cycling in forest soils, and that these effects are modified by large-scale natural disturbances.

Mots clés : BIODIVERSIDAD ; CICLO DE NUTRIENTES ; DESCOMPOSICION ; HERBIVORIA ; NOTHOFAGUS PUMILIO ; BIODIVERSITY ; DECOMPOSITION ; HERBIVORY ; NOTHOFAGUS PUMILIO ; NUTRIENT CYCLE

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Page publiée le 7 octobre 2017, mise à jour le 13 février 2020