Premium
A method for deriving net primary productivity and component respiratory fluxes from tower‐based eddy covariance data: a case study using a 17‐year data record from a Douglas‐fir chronosequence
Author(s) -
SCHWALM CHRISTOPHER R.,
BLACK T. ANDREW,
MORGENSTERN KAI,
HUMPHREYS ELYN R.
Publication year - 2007
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2006.01298.x
Subject(s) - chronosequence , eddy covariance , ecosystem respiration , primary production , productivity , environmental science , atmospheric sciences , ecosystem , forestry , mathematics , ecology , geography , biology , physics , economics , macroeconomics
Conventional gap‐filling procedures for eddy covariance (EC) data are limited to calculating ecosystem respiration ( R E ) and gross ecosystem productivity ( P G ) as well as missing values of net ecosystem productivity ( F NEP ). We develop additional postprocessing steps that estimate net primary productivity ( P N ), autotrophic ( R a ), and heterotrophic respiration ( R h ). This is based on conservation of mass of carbon (C), Monte Carlo (MC) simulation, and three ratios: C use efficiency (CUE, P N to P G ), R a to R E , and F NEP to R E . This procedure, along with the estimation of F NEP , R E , and P G , was applied to a Douglas‐fir dominated chronosequence on Vancouver Island, British Columbia, Canada. The EC data set consists of 17 site years from three sites: initiation (HDF00), pole/sapling (HDF88), and near mature (DF49), with stand ages from 1 to 56 years. Analysis focuses on annual C flux totals and C balance ratios as a function of stand age, assuming a rotation age of 56 years. All six C balance terms generally increased with stand age. Average annual P N by stand was 213, 750, and 1261 g C m −2 yr −1 for HDF00, HDF88, and DF49, respectively. The canopy compensation point, the year when the chronosequence switched from a source to a sink of C, occurred at stand age ca. 20 years. HDF00 and HDF88 were strong and moderate sources ( F NEP =−581 and −138 g C m −2 yr −1 ), respectively, while DF49 was a moderate sink ( F NEP =294 g C m −2 yr −1 ) for C. Differences between sites were greater than interannual variation (IAV) within sites and highlighted the importance of age‐related effects in C cycling. The validity of the approach is discussed using a sensitivity analysis, a comparison with growth and yield estimates from the same chronosequence, and an intercomparison with other chronosequences.