SEMINAR: REMINDER:GEOTOPICS Today: Dr. Engel (2/21 3:15 pm)

[Qiong Zhang <qzhang@rsmas.miami.edu>]

##### G  E  O  T  O  P  I  C  S  #####

    P  r  e  s  e  n  t  s

3:15 PM, Monday,  February 21st, 2011

   SLAB Seminar Room, S/A 103

Refreshments 3:00 PM

Vic Engel

 South Florida Natural Resource Center , Everglades National Park

"Mangrove Carbon Cycling in Western Everglades National Park"

    Net ecosystem carbon balance in an Everglades tidal mangrove forest Mangrove forests exhibit high global productivity rates estimated at 218±72 Tg C yr-1. Dissolved and particulate carbon (C) fluxes generated by tidal activity may represent up to 50% of net primary productivity in these forests. Remarkably, mangrove forests have been estimated to contribute 10% of all terrestrially derived dissolved organic C to the oceans. However, direct measurements of tidal C exchange in mangrove forests are challenging, particularly in large deltaic systems where interconnected channels and spatially-variable inundation patterns impute high levels of uncertainty on traditional mass balance or flow-based approaches. Improving estimates of tidal C fluxes in relation to plant and soil C balance is necessary to gain a better understanding of how mangrove ecosystems respond to environmental forcings and to compare C balance in these systems with values from terrestrial forests. Here we present a new methodology for estimating ecosystem carbon balance and for determining net C advection in a riverine mangrove forest. The study site is located along the Shark River in Everglades National Park, Florida, USA and is part of the AmeriFlux (site SRK) and the Florida Coastal Everglades Long Term Ecological Research (FCE-LTER) networks. Using an ecosystem-scale C balance approach, C advection can be defined as the difference between net ecosystem carbon dioxide exchange with the atmosphere (NEE) and the net change in C measured in the plants and soil. Prior to hurricane Wilma in 2005, NEE in this forest was estimated to be greater than 1000 g C m-2 yr-1. Preliminary results suggest that the C advected from the site annually may have been as high as 300 g C m-2 yr-1 prior to the storm, increasing to as much as 800 g C m-2 yr-1 after the disturbance. Continuous measurements of discharge rates and dissolved C in the main river channel provide an independent estimate of tidal C advection over seasonal time scales. Short-term, tracer-based analyses of dissolved C conducted as part of this study add insight into potential factors controlling the spatial and temporal variability of tidal C fluxes. The C balance in this estuary is governed by many of the same factors which regulate C in terrestrial forests, including light and temperature, but also by factors unique to tropical estuaries, including hydroperiod, salinity, and disturbance caused by tropical storms and cold temperatures. Improved understanding of the factors regulating ecosystem carbon balance and organic soil accretion is of use to Everglades managers responsible for the preservation of the mangrove ecosystem in this era of sea level rise. Furthermore, detailed coupling of land surface-atmosphere-water C fluxes will enable more precise determinations of the role of mangrove forests in global carbon budgets.

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Cheers
Qiong Zhang

Marine Geology and Geophysics
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami Fl 33149