DOI

https://doi.org/10.25772/A424-JK89

Defense Date

2025

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Christopher Gough

Second Advisor

Karen Kester

Third Advisor

Lesley Bulluck

Abstract

Soil respiration (Rs) is the largest terrestrial flux of carbon (C) to the atmosphere, with heterotrophic contributions to Rs varying spatially and temporally. While microbes are the primary and most thoroughly studied source of soil heterotrophic respiration (Rh), contributions from higher trophic organisms, including arthropods, are rarely quantified and poorly understood. Arthropod abundance and diversity correspond with variation in soil microclimate, which is influenced by site factors including canopy structure, site productivity, and disturbance. However, the extent to which these site factors influence arthropod abundance and diversity, and consequently, spatial variation in Rs is not known. The objective of our study was to evaluate whether arthropod abundance and diversity affect Rs through the cascading effects of disturbance and site productivity on canopy structure and soil microclimate. Our study leveraged the Forest Resilience Threshold Experiment, a large-scale manipulation of disturbance severity with tree mortalities of 0%, 45%, 65%, or 85% replicated across four different landscape ecosystems. Using structural equation modeling, we evaluated linkages between spatially paired measurements of in situ Rs, arthropod abundance and diversity via pitfall traps, soil moisture and temperature, and canopy structure and pre-disturbance biomass. Our findings suggest disturbance severity and pre-disturbance biomass have direct positive effects on canopy structural complexity, leading to downstream effects on soil moisture. Soil moisture was negatively linked to Shannon arthropod diversity, which was positively correlated with Rs. Mean Rs during our sampling campaign was 7 µmol CO2 m-2 sec-1, and a single unit increase in Shannon arthropod diversity corresponded with an increase in Rs of 2 µmol CO2 m-2 sec-1. We conclude that site productivity and disturbance has interacting and cascading effects on Rs through arthropod diversity, establishing arthropod diversity as an informative and critical constraint to consider when scaling spatially-variable Rs to the ecosystem level.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

6-18-2025

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