Semi-empirical modeling of abiotic and biotic factors controlling ecosystem respiration across eddy covariance sites
Résumé
In this study we examined ecosystem respiration (RECO) data from 104 sites belonging to FLUXNET, the global network of eddy covariance flux measurements. The main goal was to identify the main factors involved in the variability of RECO: temporally and between sites as affected by climate, vegetation structure and plant functional type (PFT) (evergreen needleleaf, grasslands, etc.). We demonstrated that a model using only climate drivers as predictors of RECO failed to describe part of the temporal variability in the data and that the dependency on gross primary production (GPP) needed to be included as an additional driver of RECO. The maximum seasonal leaf area index (LAIMAX) had an additional effect that explained the spatial variability of reference respiration (the respiration at reference temperature Tref=15°C, without stimulation introduced by photosynthetic activity and without water limitations), with a statistically significant linear relationship (r2=0.52 p<0.001, n=104) even within each PFT. Besides LAIMAX, we found that the reference respiration may be explained partially by total soil carbon content. For undisturbed temperate and boreal forest a negative control of the total nitrogen deposition on the reference respiration was also identified. We developed a new semi-empirical model incorporating abiotic factors (climate), recent productivity (daily GPP), general site productivity and canopy structure (LAIMAX) which performed well in predicting the spatio-temporal variability of RECO, explaining >70% of the variance for most vegetation types. Exceptions include tropical and Mediterranean broadleaf forests and deciduous broadleaf forests. Part of the variability in respiration that could not be described by our model could be attributed to a range of factors, including phenology in deciduous broadleaf forests and management practices in grasslands and croplands.
Domaines
Sciences du Vivant [q-bio]| Origine | Fichiers produits par l'(les) auteur(s) |
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