Open AccessModeling nighttime ecosystem respiration from measured CO 2 concentration and air temperature profiles using inverse methods
Author(s) -
Juang JehnYih,
Katul Gabriel G.,
Siqueira Mario B. S.,
Stoy Paul C.,
Palmroth Sari,
McCarthy Heather R.,
Kim HyunSeok,
Oren Ram
Publication year - 2006
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jd005976
Subject(s) - eddy covariance , ecosystem respiration , environmental science , atmospheric sciences , canopy , ecosystem , stratification (seeds) , hydrology (agriculture) , soil science , ecology , physics , geology , botany , biology , seed dormancy , germination , geotechnical engineering , dormancy
A major challenge for quantifying ecosystem carbon budgets from micrometeorological methods remains nighttime ecosystem respiration. An earlier study utilized a constrained source optimization (CSO) method using inverse Lagrangian dispersion theory to infer the two components of ecosystem respiration (aboveground and forest floor) from measured mean CO 2 concentration profiles within the canopy. This method required measurements of within‐canopy mean velocity statistics and did not consider local thermal stratification. We propose a Eulerian version of the CSO method (CSO E ) to account for local thermal stratification within the canopy for momentum and scalars using higher‐order closure principles. This method uses simultaneous mean CO 2 concentration and air temperature profiles within the canopy and velocity statistics above the canopy as inputs. The CSO E was tested at a maturing loblolly pine plantation over a 3‐year period with a mild drought (2001), a severe drought (2002), and a wet year (2003). Annual forest floor efflux modeled with CSO E averaged 111 g C m −2 less than that estimated using chambers during these years (2001: 1224 versus 1328 gCm −2 ; 2002: 1127 versus 1230 gCm −2 ; 2003: 1473 versus 1599 gCm −2 ). The modeled ecosystem respiration exceeded estimates from eddy covariance measurements (uncorrected for storage fluxes) by at least 25%, even at high friction velocities. Finally, we showed that the CSO E annual nighttime respiration values agree well with independent estimates derived from the intercept of the ecosystem light‐response curve from daytime eddy covariance CO 2 flux measurements.