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Controls on carbon dynamics by ecosystem structure and climate for southeastern U.S. slash pine plantations
Author(s) -
Bracho Rosvel,
Starr Gregory,
Gholz Henry L.,
Martin Timothy A.,
Cropper Wendell P.,
Loescher Henry W.
Publication year - 2012
Publication title -
ecological monographs
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.254
H-Index - 156
eISSN - 1557-7015
pISSN - 0012-9615
DOI - 10.1890/11-0587.1
Subject(s) - slash pine , environmental science , carbon sink , eddy covariance , ecosystem , canopy , leaf area index , ecosystem respiration , carbon sequestration , forest ecology , carbon cycle , ecology , agronomy , carbon dioxide , biology , pinus <genus> , botany
Planted pine forests (plantations) in the southeastern United States are an important component of the continent's carbon balance. Forest carbon dynamics are affected by a range of factors including climatic variability. Multiyear droughts have affected the region in the past, and an increase in the frequency of drought events has been predicted. How this increased climatic variability will affect the capacity of the region's pine plantations to sequester carbon is not known. We used eddy covariance and biometric approaches to measure carbon dynamics over nine years in two slash pine plantations ( Pinus elliottii var elliottii Englm) in north Florida, consisting of a newly planted and a mid‐rotation stand. During this time, the region experienced two multiyear droughts (1999–2002 and 2006–2008), separated by a three‐year wet period. Net ecosystem carbon accumulation measured using both approaches showed the same trends and magnitudes during plantation development. The newly planted site released 15.6 Mg C/ha during the first three years after planting, before becoming a carbon sink in year 4. Increases in carbon uptake during the early stages of stand development were driven by the aggrading leaf area index (LAI). After canopy closure, both sites were continuous carbon sinks with net carbon uptake (NEE) fluctuating between 4 and ∼8 Mg C·ha −1 ·yr −1 , depending on environmental conditions. Drought reduced NEE by ∼25% through its negative effects on both LAI and radiation‐use efficiency, which resulted in a larger impact on gross ecosystem carbon exchange than on ecosystem respiration. While results indicate that responses to drought involved complex interactions among water availability, LAI, and radiation‐use efficiency, these ecosystems remain carbon sinks under current management strategies and climatic variability. Variation within locations is primarily due to major disturbances, such as logging in the current study and, to a much lesser extent, local environmental fluctuations. When data from this study are compared to flux data from a broad range of forests worldwide, these ecosystems fill a data gap in the warm‐temperate zone and support a broad maximum NEE (for closed‐canopy forests) between 8°C and 20°C mean annual temperature.