B33C-0672
Long term carbon fluxes in south eastern U.S. pine ecosystems.
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Rosvel G Bracho, University of Florida, School of Forest Resources and Conservation, Ft Walton Beach, FL, United States, Timothy Martin, University of Florida, Gainesville, FL, United States, Carlos A Gonzalez-Benecke, Oregon State University, Forest Engineering, Resources and Management, Corvallis, OR, United States and Julia Sharp, Clemson University, Mathematical Sciences, Clemson, SC, United States
Abstract:
Forests in the southeastern U.S. are a critical component of the national carbon balance storing a third of the total forest carbon (C) in conterminous USA. South eastern forests occupy 60% of the land area, with a large fraction dominated by the genus Pinus distributed in almost equal proportions of naturally-regenerated and planted stands. These stands often differ in structure (e.g., stem density, leaf area index (LAI)) and in the intensity with which they are managed (e.g. naturally-regenerated, older pine stands are often managed less intensively, with prescribed fire). We measured C fluxes using the eddy covariance approach (net ecosystem production, -NEP) in planted (Pinus elliottii var. elliottii) and naturally-regenerated mixed stand of long leaf (Pinus palustris Mill) and slash pine (Pinus elliottii var. elliottii) accompanied by biometric estimations of C balance. Measurements spanned more than a decade and included interannual climatic variability ranging from severe droughts (e.g. Palmer Drought severity index (PDSI) averaged -2.7 from January 2000 to May 2002, and -3.3 from June 2006 to April 2008), to years with tropical storms. Annual NEP for the older, naturally-regenerated stand fluctuated from -1.60 to -5.38 Mg C ha-1 yr-1 with an average of -2.73 ± 1.17 Mg C ha-1 yr-1 while in plantations after canopy closure NEP fluctuated from -4.0 to -8.2 Mg C ha-1 yr-1 with an average of -6.17 ± 1.34 Mg C ha-1 yr-1. Annual NEP in naturally-regenerated pine was mainly driven by a combination of water availability and understory burning while in plantations it was driven by water availability after canopy closure. Woody and above ground net primary productivity (NPP) followed gross ecosystem carbon exchange (GEE) in both ecosystems. Naturally-regenerated and planted pine are a strong carbon sink under the current management and environmental fluctuations accumulating 28 and 130 Mg C ha-1 in a decade, respectively, and are among the most productive forests in the world.
