  Direct advection measurements do not help to solve the night-time CO2 closure problem: Evidence from three different forestsAubinet, Marc  ; ; Heinesch, Bernard et alin Agricultural and Forest Meteorology (2010), 150(5), 655-664 The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time ... [more ▼] The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time conditions, in an attempt to improve NEE estimates. Four towers were arranged in a square around a main tower, with the sides of the square about 100 m long. Equipped with 16 sonic anemometers and [CO2] sampling points, the towers were installed to measure vertical and horizontal advection of [CO2]. Vertical turbulent fluxes were measured by an eddy covariance system at the top of the main tower. The results showed that horizontal advection varied greatly from site to site and from one wind sector to another, the highest values being reached when there were large friction velocities and fairly unstable conditions. There was less variation in vertical advection, the highest values being reached when there were low friction velocities and stable conditions. The night-time NEE estimates deduced from the mass balance were found to be incompatible with biologically driven fluxes because (i) they varied strongly from one wind sector to another and this variation could not be explained in terms of a response of the biologic flux to climate, (ii) their order of magnitude was not realistic and (iii) they still showed a trend vs. friction velocity. From a critical analysis of the measurement and data treatment we concluded that the causes of the problem are related to the representativeness of the measurement (control volume size, sampling resolution) or the hypotheses underlying the derivation of the [CO2] mass balance (ignoring the horizontal turbulent flux divergence). This suggests that the improvement of eddy flux measurements by developing an advection completed [CO2] mass balance at night would be practically difficult. (C) 2010 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 25 (3 ULg) Management effects on European cropland respiration; ; et al in Agriculture, Ecosystems & Environment (2010), 139 Detailed reference viewed: 21 (2 ULg)Quality Control Of Carboeurope Flux Data - Part 1: Coupling Footprint Analyses With Flux Data Quality Assessment To Evaluate Sites In Forest Ecosystems; ; Aubinet, Marc et alin Biogeosciences (2008), 5(2), Detailed reference viewed: 14 (2 ULg)CO2 balance of boreal, temperate, and tropical forests derived from a global database; ; et al in Global Change Biology (2007), 13(12), 2509-2537 Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this ... [more ▼] Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but syntheses of these data are still sparse. To facilitate future synthesis activities, we have assembled a comprehensive global database for forest ecosystems, which includes carbon budget variables (fluxes and stocks), ecosystem traits (e.g. leaf area index, age), as well as ancillary site information such as management regime, climate, and soil characteristics. This publicly available database can be used to quantify global, regional or biome-specific carbon budgets; to re-examine established relationships; to test emerging hypotheses about ecosystem functioning [e.g. a constant net ecosystem production (NEP) to gross primary production (GPP) ratio]; and as benchmarks for model evaluations. In this paper, we present the first analysis of this database. We discuss the climatic influences on GPP, net primary production (NPP) and NEP and present the CO2 balances for boreal, temperate, and tropical forest biomes based on micrometeorological, ecophysiological, and biometric flux and inventory estimates. Globally, GPP of forests benefited from higher temperatures and precipitation whereas NPP saturated above either a threshold of 1500 mm precipitation or a mean annual temperature of 10 degrees C. The global pattern in NEP was insensitive to climate and is hypothesized to be mainly determined by nonclimatic conditions such as successional stage, management, site history, and site disturbance. In all biomes, closing the CO2 balance required the introduction of substantial biome-specific closure terms. Nonclosure was taken as an indication that respiratory processes, advection, and non-CO2 carbon fluxes are not presently being adequately accounted for. [less ▲] Detailed reference viewed: 47 (4 ULg)Evidence For Soil Water Control On Carbon And Water Dynamics In European Forests During The Extremely Dry Year: 2003; ; et al in Agricultural and Forest Meteorology (2007), 143(1-2), Detailed reference viewed: 20 (1 ULg)Quality Analysis Applied On Eddy Covariance Measurements At Complex Forest Sites Using Footprint Modelling; ; et al in Theoretical and Applied Climatology (2005), 80(2-4), Detailed reference viewed: 12 (2 ULg)Methodology for data acquisition, storage and treatmentAubinet, Marc ; ; et alin Valentini, R. (Ed.) Fluxes of Carbon, Water and Energy of European Forests (2003) Detailed reference viewed: 14 (0 ULg)Spruce forests (Norway and Sitka spruce, including Douglas fir): Carbon and water fluxes, Balances, Ecological and ecophysiological determinants; Aubinet, Marc ; et alin Valentini, Riccardo (Ed.) Fluxes of Carbon, Water and Energy of European Forests (2003) Detailed reference viewed: 41 (0 ULg)A Model Based Study of Carbon Fluxes at Ten European Forest Sites; ; Aubinet, Marc et alin Valentini, Riccardo (Ed.) Fluxes of Carbon, Water and Energy of European Forests (2003) Detailed reference viewed: 15 (0 ULg)Seasonality Of Ecosystem Respiration And Gross Primary Production As Derived From Fluxnet Measurements; ; et al in Agricultural and Forest Meteorology (2002), 113(1-4), Detailed reference viewed: 12 (2 ULg)Carbon balance gradient in European forests: should we doubt 'surprising' results? A reply to Piovesan & Adams; ; et al in Journal of Vegetation Science (2001), 12(1), 145-150 This paper responds to the Forum contribution by Piovesan & Adams (2000) who criticized the results obtained by the EUROFLUX network on carbon fluxes of several European forests. The major point of ... [more ▼] This paper responds to the Forum contribution by Piovesan & Adams (2000) who criticized the results obtained by the EUROFLUX network on carbon fluxes of several European forests. The major point of criticism was that the data provided by EUROFLUX are inconsistent with current scientific understanding. It is argued that understanding the terrestrial global carbon cycle requires more than simply restating what was known previously, and that Piovesan & Adams have not been able to show any major conflicts between our findings and ecosystem or atmospheric-transport theories. [less ▲] Detailed reference viewed: 27 (1 ULg)Gap Filling Strategies For Long Term Energy Flux Data Sets; ; et al in Agricultural and Forest Meteorology (2001), 107(1), Detailed reference viewed: 10 (2 ULg)Gap Filling Strategies For Defensible Annual Sums Of Net Ecosystem Exchange; ; et al in Agricultural and Forest Meteorology (2001), 107(1), Detailed reference viewed: 8 (2 ULg)Productivity Overshadows Temperature In Determining Soil And Ecosystem Respiration Across European Forests; ; et al in Global Change Biology (2001), 7(3), Detailed reference viewed: 20 (1 ULg)Respiration As The Main Determinant Of Carbon Balance In European Forests; ; et al in Nature (2000), 404(6780), Detailed reference viewed: 30 (4 ULg)Estimates of the annual net carbon and water exchange of forests: the EUROFLUX methodology.Aubinet, Marc ; ; et alin Advances in Ecological Research (1999), 30 Detailed reference viewed: 493 (14 ULg) |
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