title: Influence of physiological phenology on the seasonal pattern of ecosystem respiration in deciduous forests.
abstract: Understanding the environmental and biotic drivers of respiration at the ecosystem level is a prerequisite to further improve scenarios of the global carbon cycle. In this study we investigated the relevance of physiological phenology, defined as seasonal changes in plant physiological properties, for explaining the temporal dynamics of ecosystem respiration (RECO) in deciduous forests. Previous studies showed that empirical RECO models can be substantially improved by considering the biotic dependency of RECO on the short-term productivity (e.g., daily gross primary production, GPP) in addition to the well-known environmental controls of temperature and water availability. Here, we use a model-data integration approach to investigate the added value of physiological phenology, represented by the first temporal derivative of GPP, or alternatively of the fraction of absorbed photosynthetically active radiation, for modeling RECO at 19 deciduous broadleaved forests in the FLUXNET La Thuile database. The new data-oriented semiempirical model leads to an 8% decrease in root mean square error (RMSE) and a 6% increase in the modeling efficiency (EF) of modeled RECO when compared to a version of the model that does not consider the physiological phenology. The reduction of the model-observation bias occurred mainly at the monthly time scale, and in spring and summer, while a smaller reduction was observed at the annual time scale. The proposed approach did not improve the model performance at several sites, and we identified as potential causes the plant canopy heterogeneity and the use of air temperature as a driver of ecosystem respiration instead of soil temperature. However, in the majority of sites the model-error remained unchanged regardless of the driving temperature. Overall, our results point toward the potential for improving current approaches for modeling RECO in deciduous forests by including the phenological cycle of the canopy.
authors.affiliation: Max Planck Institute for Biogeochemistry, PO Box 100164, Jena, 07701, Germany; Remote Sensing of Environmental Dynamics Lab, DISAT, University of Milano-Bicocca, P.zza della Scienza 1, Milan, Italy.
authors.forename: Mirco
authors.initials: M
authors.lastname: Migliavacca
authors.forename: Markus
authors.initials: M
authors.lastname: Reichstein
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Richardson
authors.forename: Miguel D
authors.initials: MD
authors.lastname: Mahecha
authors.forename: Edoardo
authors.initials: E
authors.lastname: Cremonese
authors.forename: Nicolas
authors.initials: N
authors.lastname: Delpierre
authors.forename: Marta
authors.initials: M
authors.lastname: Galvagno
authors.forename: Beverly E
authors.initials: BE
authors.lastname: Law
authors.forename: Georg
authors.initials: G
authors.lastname: Wohlfahrt
authors.forename: T Andrew
authors.initials: TA
authors.lastname: Black
authors.forename: Nuno
authors.initials: N
authors.lastname: Carvalhais
authors.forename: Guido
authors.initials: G
authors.lastname: Ceccherini
authors.forename: Jiquan
authors.initials: J
authors.lastname: Chen
authors.forename: Nadine
authors.initials: N
authors.lastname: Gobron
authors.forename: Ernest
authors.initials: E
authors.lastname: Koffi
authors.forename: J William
authors.initials: JW
authors.lastname: Munger
authors.forename: Oscar
authors.initials: O
authors.lastname: Perez-Priego
authors.forename: Monica
authors.initials: M
authors.lastname: Robustelli
authors.forename: Enrico
authors.initials: E
authors.lastname: Tomelleri
authors.forename: Alessandro
authors.initials: A
authors.lastname: Cescatti
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D017753:Ecosystem; D005060:Europe; D065928:Forests; D008954:Models, Biological; D009656:North America; D010788:Photosynthesis / Q000502:physiology; D018521:Plant Physiological Phenomena; D012621:Seasons
keywords: FLUXNET La Thuile database; deciduous forests; ecosystem respiration; eddy covariance; land-atmosphere fluxes; phenology