Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology, Ecology

Date of Defense

6-23-2022

Graduate Advisor

Robert Marquis

Committee

Leighton Reid

Nathan Muchhala

Lon Chubiz

Abstract

Dead wood represents 8% of terrestrial carbon stocks and is an important source of habitat and food for decomposer and non-decomposer arthropods. However, anthropogenic disturbance reduces the amount of dead wood, putting at risk the presence of a habitat that is essential for many arthropods and other organisms that rely on it for food and shelter. Forest restoration aims to assist the recovery of ecosystems that have been damaged or destroyed and could be a means to recover both dead wood and its associated arthropod communities. This doctoral dissertation lies at the intersection of climate change, biodiversity loss and ecological restoration, and for the first time, addresses these issues in a tropical ecosystem. I focus on answering three largely unexplored questions: (1) What is the effectiveness of forest restoration at recovering dead wood volumes as they are found in reference forests? (2) How do different restoration strategies affect arthropod-mediated dead wood decomposition? and (3) How do different restoration strategies affect arthropod communities in the proximity of dead wood?

My study took place in a premontane tropical rainforest in southern Costa Rica, and in two broadly used restoration strategies, restoration plantations and natural regeneration. I compared the effects of these restoration strategies on arthropod-dead wood interactions to those in forests >100 years old. Restoration plantations recovered 40% of dead wood volumes in only 17 years whereas natural regeneration recovered virtually no dead wood in the same amount of time. Neither restoration treatment nor arthropod colonization affected dead wood decomposition during the first year. Finally, litter arthropod abundances are higher in reference forests, intermediate in plantations, and lowest in natural regeneration. Proximity to dead logs did not affect arthropod communities with the exception of ants, which were more species-rich closer to logs compared to far away from them. Overall, my study shows that forest restoration is effective at recovering dead wood carbon pools, arthropod communities, and decomposition functions. Further research is required on the effects of insect-mediated wood decomposition over a longer timeframe. To assess the efficiency of restoration at recovering arthropod communities, arthropods should be surveyed in recently abandoned cattle pastures.

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