title: Importance of short-term dynamics in carbon isotope ratios of ecosystem respiration (delta13C(R)) in a Mediterranean oak woodland and linkage to environmental factors.
abstract: Temporal dynamics in carbon isotope ratios of ecosystem respiration (delta13C(R)) were evaluated on hourly, daily and annual timescales in a Mediterranean woodland. Emphasis was given to the periods of transition from wet to dry season and vice versa, when the system turns from a net carbon sink to a source. The constancy of nocturnal delta13C(R) was tested. The relationship between delta13C(R) (determined through Keeling plots) and environmental factors was evaluated through time-lag analysis. Delta13C(R) exhibited high annual variation (> 7). During the transition periods, delta13C(R) correlated significantly with factors influencing photosynthetic discrimination, soil respiration, and whole-canopy conductance. Time-lags differed between below- and above-ground variables, and between seasons. A shift in regression parameters with environmental factors indicated seasonal differences in ecosystem responsiveness (e.g. temperature acclimation). Delta13C(R) exhibited substantial nocturnal enrichment (> 4) from dusk to dawn. These data indicate pronounced short-term dynamics in delta13C(R) at hourly to daily timescales and a modulated response to environmental drivers. Substantial short-term changes in nocturnal delta13C(R) may have important implications for the sampling protocols of nocturnal Keeling plots.
authors.affiliation: Exp. and Systems Ecology, University of Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany. c.werner@uni-bielefeld.de
authors.forename: Christiane
authors.initials: C
authors.lastname: Werner
authors.forename: Stephan
authors.initials: S
authors.lastname: Unger
authors.forename: João S
authors.initials: JS
authors.lastname: Pereira
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Maia
authors.forename: Teresa S
authors.initials: TS
authors.lastname: David
authors.forename: Cathy
authors.initials: C
authors.lastname: Kurz-Besson
authors.forename: Jorge S
authors.initials: JS
authors.lastname: David
authors.forename: Cristina
authors.initials: C
authors.lastname: Máguas
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes; D002940:Circadian Rhythm; D017753:Ecosystem; D019083:Mediterranean Region; D029963:Quercus / Q000378:metabolism*; D012621:Seasons; D013997:Time Factors; D014197:Trees / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide