Date on Master's Thesis/Doctoral Dissertation

8-2018

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biology

Degree Program

Biology, PhD

Committee Chair

Yanoviak, Stephen

Committee Co-Chair (if applicable)

Carreiro, Margaret

Committee Member

Carreiro, Margaret

Committee Member

Emery, Sarah

Committee Member

Remold, Susanna

Committee Member

Bitzer, Phillip

Author's Keywords

dead wood; decomposition; tropical forest; lightning; fungi; prokaryotes

Abstract

This dissertation investigates the distribution, production, and decomposition of dead wood (or woody debris) in a lowland tropical forest within the Barro Colorado Nature Monument in Panama. Although the importance of woody debris is widely accepted, information describing components of WD pools and fluxes is generally separated in both time and space, particularly in understudied tropical forests. Here I provide a comprehensive inventory of woody debris in a lowland tropical forest (Chapter 1). Woody debris is highly aggregated and difficult to quantify, and this study demonstrates that historic estimates of woody debris pools and fluxes underestimate their uncertainty. In a separate collaboration, I quantified how soil nutrient availability regulates wood decomposition using a 15-year litter manipulation experiment (Chapter 2). Wood decomposition rates decreased with reduced nutrient availability in the litter removal treatments, but did not change relative to controls in the litter addition treatments. The first chapter also showed that ca. 50% of woody debris stocks were not in contact with the ground; however, information regarding the factors that regulate wood decomposition comes exclusively from the forest floor. Consequently, I quantified differences in decomposition rates, microclimate, and microbial community structure (prokaryotes and fungi) along a vertical gradient from the ground and the canopy of this tropical forest (Chapter 3). Decomposition rates varied predictably based on microclimate conditions and fungal composition along this vertical gradient. Decomposition rates also vary substantially with species-specific wood traits, and thus the relative contributions of each tree species to woody debris inputs is important to carbon cycling. Large trees contribute disproportionately to dead wood pools and lightning is one of the primary agents of large tree mortality in tropical forests. I used empirical measurements of tree electrical properties and lightning characteristics to model lightning damage parameters (heating and power) for trees of different species and size classes (Chapter 4). These damage parameters differ substantially among species, suggesting that increased lightning frequency will change inputs of woody debris. These studies improve our understanding of woody debris dynamics and tropical forest carbon cycling so that we can better predict future patterns in a changing world.

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