Title: Seasonal variation of photosynthetic model parameters and leaf area index from global Fluxnet eddy covariance data
Authors: GROENENDIJK M.DOLMAN A. J.AMMANN C.ARNETH AlmutCESCATTI AlessandroDRAGONI D.GASH J.h.c.GIANELLE DamianoGIOLI B.KIELY GeraldKNOHL A.LAW BeverlyLUND M.MARCOLLA B.VAN DER MOLEN M.k.MONTAGNANI LeonardoMOORS E.RICHARDSON Andrew D.ROUPSARD O.VERBEECK H.WOHLFAHRT Georg
Citation: JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES vol. 116 no. G4 p. G04027
Publisher: AMER GEOPHYSICAL UNION
Publication Year: 2011
JRC N°: JRC68599
ISSN: 0148-0227
URI: http://onlinelibrary.wiley.com/doi/10.1029/2011JG001742/abstract
http://publications.jrc.ec.europa.eu/repository/handle/JRC68599
DOI: 10.1029/2011JG001742
Type: Articles in periodicals and books
Abstract: Global vegetation models require the photosynthetic parameters, maximum carboxylation capacity (Vcm), and quantum yield (a) to parameterize their plant functional types (PFTs). The purpose of this work is to determine how much the scaling of the parameters from leaf to ecosystem level through a seasonally varying leaf area index (LAI) explains the parameter variation within and between PFTs. Using Fluxnet data, we simulate a seasonally variable LAIF for a large range of sites, comparable to the LAIM derived from MODIS. There are discrepancies when LAIF reach zero levels and LAIM still provides a small positive value. We find that temperature is the most common constraint for LAIF in 55% of the simulations, while global radiation and vapor pressure deficit are the key constraints for 18% and 27% of the simulations, respectively, while large differences in this forcing still exist when looking at specific PFTs. Despite these differences, the annual photosynthesis simulations are comparable when using LAIF or LAIM (r2 = 0.89). We investigated further the seasonal variation of ecosystem‐scale parameters derived with LAIF. Vcm has the largest seasonal variation. This holds for all vegetation types and climates. The parameter a is less variable. By including ecosystem‐scale parameter seasonality we can explain a considerable part of the ecosystem‐scale parameter variation between PFTs. The remaining unexplained leaf‐scale PFT variation still needs further work, including elucidating the precise role of leaf and soil level nitrogen.
JRC Directorate:Sustainable Resources

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