Title page for ETD etd-07112003-091151


Type of Document Dissertation
Author Gough, Christopher Michael
URN etd-07112003-091151
Title Quantification and Physiology of Carbon Dynamics in Intensively Managed Loblolly Pine (Pinus taeda L.)
Degree PhD
Department Forestry
Advisory Committee
Advisor Name Title
Seiler, John R. Committee Chair
Aust, Wallace Michael Committee Member
Fox, Thomas R. Committee Member
Maier, Christopher A. Committee Member
Parrish, David J. Committee Member
Keywords
  • carbon
  • soil respiration
  • photosynthesis
  • fertilization
  • soil CO2 efflux
  • nitrogen
Date of Defense 2003-07-07
Availability unrestricted
Abstract
Loblolly pine (Pinus taeda L.) occupies 13 million hectares in the United States and represents a critical component of the global carbon (C) cycle. Forest management alters C dynamics, affecting the C sequestration capacity of a site. Identifying drivers that influence C cycling, quantifying C fluxes, and determining how management alters processes involved in C cycling will allow for an understanding of C sequestration capacity in managed forests. Objectives of the first study included (1) investigating environmental, soil C, root, and stand influences on soil CO2 efflux on the South Carolina coastal plain and (2) quantifying soil CO2 efflux over a rotation in loblolly pine stands located on the South Carolina coastal plain and the Virginia piedmont. In relation to the first objective, temporal variation in soil CO2 efflux was most highly related to soil temperature. Spatial and temporal variability in soil CO2 efflux was weakly related to soil C and root biomass, and not related to coarse woody debris, stand age, stand volume, or site index [Chapter 2]. Soil CO2 efflux was not related to stand age on the South Carolina sites while efflux was positively related to age on the Virginia sites. Cumulative soil C efflux on the South Carolina sites over 20 years is an estimated 278.6 Mg C/ha compared with an estimated 210.9 Mg C/ha on the Virginia sites [Chapter 3]. Objectives of the second study were (1) to investigate short-term effects of fertilization on processes permitting enhanced growth in loblolly pine and (2) to determine the short-term effects of fertilization on autotrophic, heterotrophic, and soil respiration. Major results from the study include the finding that fertilization caused a transient rise in photosynthetic capacity, which paralleled changes in foliar nitrogen. Leaf area accumulation and enhanced growth following fertilization was partly due to enhanced C fixation capacity [Chapter 4]. Fertilization altered the contribution of autotrophic and heterotrophic respiration to total soil CO2 efflux. Enhanced specific root respiration was short-lived while suppressed microbial respiration following fertilization was maintained over the course of the nearly 200-day study. Respiring root biomass growth increased total soil respiration over time [Chapter 5].
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