Title page for ETD etd-07082010-102921


Type of Document Dissertation
Author Tobias, Vanessa Danielle
URN etd-07082010-102921
Title Developing Tools to Identify Factors that Limit Production in Coastal Marshes
Degree Doctor of Philosophy (Ph.D.)
Department Renewable Natural Resources
Advisory Committee
Advisor Name Title
Nyman, J. Andew Committee Chair
DeLaune, Ronald Committee Member
Foret, John Committee Member
Gambrell, Robert Committee Member
Kelso, William Committee Member
Bush, Edward Dean's Representative
Keywords
  • vegetation
  • sea level rise
  • management
  • natural resources
  • flooding
  • salinity
  • nitrogen
  • stress
  • productivity
  • restoration
  • marsh
  • coastal
  • Spartina patens
Date of Defense 2010-05-20
Availability unrestricted
Abstract
Marsh loss is a problem in many areas around the world. In Louisiana’s coastal marshes, where Spartina patens is the most common plant, restoration and management seek to slow wetland loss rates that average approximately 77.4 km2/year. To combat the problem, scientists and managers require tools to determine local causes and evaluate the effectiveness of management techniques. Current methods for identifying factors that limit productivity in marshes are too time-consuming or expensive for wide-spread, regular use. Critical values of elemental concentrations in plant tissue are widely used to diagnose mineral deficiencies and toxicities in agricultural crops, however. I used the chemical composition of leaf tissue from S. patens grown under controlled conditions to develop critical values of C:N ratio and concentrations of Na, Mn, and Ca to identify N limitation, salinity stress, and flooding stress, respectively. I tested these critical values and identified seasonal changes in leaf tissue chemistry in a field experiment where all three limiting factors fluctuated naturally. I also compared the leaf tissue chemistry of S. patens and Spartina alterniflora, the second most common plant in Louisiana’s coastal marshes, to facilitate comparisons between the species. Finally, I investigated the effects of flooding stress on above- and belowground biomass of S. patens. Aboveground biomass was reduced by low N-uptake, high salinity, and high flooding. Belowground biomass was reduced by increased flooding. In leaf tissue, C:N decreased with increasing N-availability and [Na] increased with increasing salinity. [Mn] and [Ca] in leaf tissue decreased with increased flooding. In the field study, C:N increased seasonally. Biomass was most highly correlated with [Na] in spring and with both [Na] and C:N in summer. In fall, leaf tissue composition appeared unrelated to biomass. Managers should take seasonal differences in leaf tissue composition and nutritional requirements into account when diagnosing the causes of limited production and when creating management plans. Leaf tissue should be collected in summer to diagnose limiting factors. To have the most impact, flooding should be used in late spring or early summer to reduce salinity and increase N-availability.
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