Influence of physiological phenology on the seasonal pattern of ecosystem respiration in deciduous forests

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 dynamics ecosystem respiration (RECO) in deciduous forests. Previous studies showed that empirical RECO models can be substantially improved when considering the biotic dependency of RECO on some measure of 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 the fraction of absorbed photosynthetically active radiation fAPAR, for modeling RECO at 19 deciduous broadleaved forests in the FLUXNET La Thuile database. The new data-oriented semi–empirical model, developed with an emphasis towards up-scaling to larger areas, leads to an 8% decrease in root mean square error (RMSE) and a 6% increase in the modeling efficiency (EF) of modeled RECO. The reduction of the model–observation bias occurred mainly at monthly time-scale, and in spring and summer, while a smaller reduction was observed at the annual time–scale. In few sites the proposed approach failed to improve the model performance and we identified as potential cause the plant canopy heterogeneity and the use of air temperature as driver instead of soil temperature, the latter identified as the main driver of respiration in few sites. However, in the majority of cases the model-error remained unchanged regardless the driving temperature used. Overall, our results point toward the need of improving current approaches for modeling RECO in deciduous forests by including the phenological cycle of the canopy.

MIGLIAVACCA Mirco;  REICHSTEIN Markus;  RICHARDSON Andrew D.;  MAHECHA Miguel D.;  CREMONESE Edoardo;  DELPIERRE Nicolas;  GALVAGNO Marta;  LAW Beverly;  WOHLFAHRT G.;  BLACK A.;  CARVALHAIS Nuno;  CECCHERINI Guido;  GOBRON Nadine;  CHEN Jiquan;  KOFFI N'Dri;  MUNGER William J;  PEREZ-PRIEGO Oscar;  ROBUSTELLI Monica;  TOMELLERI Enrico;  CESCATTI Alessandro; 

2015-01-26

WILEY-BLACKWELL

JRC91108

1354-1013,   

http://onlinelibrary.wiley.com/doi/10.1111/gcb.12671/abstract,    https://publications.jrc.ec.europa.eu/repository/handle/JRC91108,   

10.1111/gcb.12671,