Defense Date

2020

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Christopher M. Gough

Abstract

In the United States, forests sequester 17% of national carbon (C) emissions annually (UGCRP, 2018), however shifting forest disturbances threaten the stability of this essential C sink. Unlike the high severity, stand-replacing disturbances that were widespread a century ago, today’s eastern temperate forests experience frequent low-to-moderate severity disturbances from invasive pests and pathogens with mixed effects on net primary production (NPP). Carbon cycling stability after disturbance has been reported, however, the mechanisms underlying immediate NPP stability or decline are not well understood. Through weekly measurements of production in a landscape scale experiment, we show that the sustained growth of senescent trees in the first year after disturbance stabilized aboveground wood net primary production (ANPPw) in an eastern temperate forest. We found no evidence for an immediate compensatory growth response from healthy trees that we hypothesized, but instead, aboveground accumulation of C and continued growth by senescent trees. Among disturbance severities (0, 45, 65, 85% gross leaf area loss) and two disturbance types concentrated in the lower and upper canopy, no difference in annual ANPPw relative to a control was observed. Further, we found early, but limited evidence that early successional plant functional types (PFT) contribute more to annual ANPPw than late successional PFTs at high severity disturbances (>65%). Our high-frequency ANPPw observations provide novel insights into the immediate response of a large C pool to disturbance, revealing initial mechanisms of stability useful as benchmarks for ecosystem models. We conclude that C cycling stability immediately following disturbance is largely dependent on the continued aboveground growth of senescent trees.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-4-2020

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