Title
Interannual <tex>$CO_{2}$</tex> exchange of a sparse Mediterranean shrubland on a carbonaceous substrate
Author
Faculty/Department
Faculty of Sciences. Biology
Publication type
article
Publication
Subject
Physics
Chemistry
Biology
Source (journal)
Journal of geophysical research : biogeosciences
Volume/pages
114(2009) , p. G04015,1-G04015,11
ISSN
0148-0227
Article Reference
G04015
ISI
000272444500001
Carrier
E-only publicatie
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
This study presents the interannual CO(2) exchange of a semiarid shrubland overlying a carbonaceous substrate where abiotic processes may interact with biological processes in the ecosystem carbon cycle. Estimated by the eddy covariance technique and two different gap-filling models (RBF neural network and MDS ``Marginal Distribution Sampling''), the mean annual net ecosystem exchange (NEE) of CO(2) varied from -63 to 29 g C m(-2), averaging -2 +/- 23 g C m(-2) from May 2004 to December 2007. In addition, CO(2) exchange was divided into periods likely dominated by clear signals of biological activity (high daytime uptake, low Bowen ratio) and periods of apparent plant senescence (dry conditions) to better understand the relative contributions of ``biological versus abiotic processes'' to the annual NEE and the interannual variability of these processes. During biological periods, CO(2) exchange appears to be related to changes in the ecosystem leaf area index, whereas abiotic fluxes are most closely related to evapotranspiration. The timing of rainfall events seems to be a main determinant of both activation and duration of biological processes. During apparent abiotic periods, CO(2) exchange is characterized by daytime emissions averaging 1.5 mu mol m(-2) s(-1), whereas biological periods are characterized by daytime CO(2) uptake with mean values of around 1.4 mu mol m(-2) s(-1). As a preliminary result, the abiotic period characterized from 19% of 2004 to 45% of 2007 with a mean duration of approximately 2 months. However, future research is needed in order to achieve a more reliable division between determinant processes involved in CO(2) exchange over carbonaceous substrates.
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