Seasonality of ecosystem respiration and gross primary production as derived from FLUXNET measurements

Abstract

Differences in the seasonal pattern of assimilatory and respiratory processes are responsible for divergences in seasonal net carbon exchange among ecosystems. Using FLUXNET data (http://www.eosdis.ornl.gov/FLUXNET) we have analyzed seasonal patterns of gross primary productivity (F GPP ), and ecosystem respiration (F RE ) of boreal and temperate, deciduous and coniferous forests, Mediterranean evergreen systems, a rainforest, temperate grasslands, and C 3 and C 4 crops. Based on generalized seasonal patterns classifications of ecosystems into vegetation functional types can be evaluated for use in global productivity and climate change models. The results of this study contribute to our understanding of respiratory costs of assimilated carbon in various ecosystems.Seasonal variability of F GPP and F RE of the investigated sites increased in the order tropical < Mediterranean < temperate coniferous < temperate deciduous < boreal forests. Together with the boreal forest sites, the managed grasslands and crops show the largest seasonal variability. In the temperate coniferous forests, seasonal patterns of F GPP and F RE are in phase, in the temperate deciduous and boreal coniferous forests F RE was delayed compared to F GPP , resulting in the greatest imbalance between respiratory and assimilatory fluxes early in the growing season.F GPP adjusted for the length of the carbon uptake period decreased at the sampling sites across functional types in the order C 4 crops, temperate and boreal deciduous forests (7.5-8.3 g C m −2 per day) > temperate conifers, C 3 grassland and crops (5.7-6.9 g C m −2 per day) > boreal conifers (4.6 g C m −2 per day). Annual F GPP and net ecosystem productivity (F NEP ) decreased across climate zones in the order tropical > temperate > boreal. However, the decrease in F NEP with latitude was greater than the decrease in F GPP , indicating a larger contribution of respiratory (especially heterotrophic) processes in boreal systems.

Two years with extreme and little snowfall: effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

“…Gap filling of the eddy covariance data was performed based on a look-up table approach (Falge et al, 2002;Reichstein et al, 2005; Eddy covariance gap-filling & fluxpartitioning tool, 2015) using the REddyProcWeb online tool (Max Planck Institute for Biogeochemistry). Due to very limited data availability at both locations during the second snowmelt period in 2014, no gap filling of H and LE was applied and turbulent fluxes of H and LE were excluded from the analysis during that period.…”

Deriving a light use efficiency model from eddy covariance flux data for predicting daily gross primary production across biomes

“…Nighttime NEE represents nighttime respiration (autotrophic and heterotrophic) because plants do not photosynthesize at night. The following model (Marshall and Biscoe, 1980;Falge et al, 2002;Saito et al, 2005) was used to describe the effects of temperature on night-time NEE:…”

Systematic assessment of terrestrial biogeochemistry in coupled climate–carbon models

“…Eddy covariance measurements provide a powerful constraint on surface energy exchange (Stockli et al, 2008), the seasonal dynamics of NEE (Falge et al, 2002) and GPP (Falge et al, 2002;Heinsch et al, 2006). Prognostic leaf area from the biogeochemical model must be integrated with other aspects of the LSM to predict, for example, the flow of available energy into latent and sensible heat.…”