References of "Longdoz, B"
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See detailGround-based Network of NDVI measurements for tracking temporal dynamics of canopy structure and vegetation phenology in different biomes
Soudani, K.; Hmimina, K.; Delpierre, N. et al

in Remote Sensing of Environment (2012), 123

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See detailExceptional Carbon Uptake In European Forests During The Warm Spring Of 2007: A Data-Model Analysis
Delpierre, N.; Soudani, K.; Kostner, B. et al

in Global Change Biology (2009), 15(6), 1455-1474

Temperate and boreal forests undergo drastic functional changes in the springtime, shifting within a few weeks from net carbon (C) sources to net C sinks. Most of these changes are mediated by temperature ... [more ▼]

Temperate and boreal forests undergo drastic functional changes in the springtime, shifting within a few weeks from net carbon (C) sources to net C sinks. Most of these changes are mediated by temperature. The autumn 2006-winter 2007 record warm period was followed by an exceptionally warm spring in Europe, making spring 2007 a good candidate for advances in the onset of the photosynthetically active period. An analysis of a decade of eddy covariance data from six European forests stands, which encompass a wide range of functional types (broadleaf evergreen, broadleaf deciduous, needleleaf evergreen) and a wide latitudinal band (from 44 degrees to 62 degrees N), revealed exceptional fluxes during spring 2007. Gross primary productivity (GPP) of spring 2007 was the maximum recorded in the decade examined for all sites but a Mediterranean evergreen forest (with a +40 to +130 gC m(-2) anomaly compared with the decadal mean over the January-May period). Total ecosystem respiration (TER) was also promoted during spring 2007, though less anomalous than GPP (with a +17 to +93 gC m(-2) anomaly over 5 months), leading to higher net uptake than the long-term mean at all sites (+12 to +79 gC m(-2) anomaly over 5 months). A correlative analysis relating springtime C fluxes to simple phenological indices suggested spring C uptake and temperatures to be related. The CASTANEA process-based model was used to disentangle the seasonality of climatic drivers (incoming radiation, air and soil temperatures) and biological drivers (canopy dynamics, thermal acclimation of photosynthesis to low temperatures) on spring C fluxes along the latitudinal gradient. A sensitivity analysis of model simulations evidenced the roles of (i) an exceptional early budburst combined with elevated air temperature in deciduous sites, and (ii) an early relief of winter thermal acclimation in coniferous sites for the promotion of 2007 spring assimilation. [less ▲]

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See detailEvidence For Soil Water Control On Carbon And Water Dynamics In European Forests During The Extremely Dry Year: 2003
Granier, A.; Reichstein, M.; Breda, N. et al

in Agricultural and Forest Meteorology (2007), 143(1-2),

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See detailTowards A Standardized Processing Of Net Ecosystem Exchange Measured With Eddy Covariance Technique: Algorithms And Uncertainty Estimation
Papale, D.; Reichstein, M.; Aubinet, Marc ULg et al

in Biogeosciences (2006), 3(4),

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See detailComparing CO2 storage and advection conditions at night at different carboeuroflux sites
Aubinet, Marc ULg; Berbigier, P.; Bernhofer, C. H. et al

in Boundary-Layer Meteorology (2005), 116(1), 63-94

Anemometer and CO2 concentration data from temporary campaigns performed at six CARBOEUROFLUX forest sites were used to estimate the importance of non-turbulent fluxes in nighttime conditions. While ... [more ▼]

Anemometer and CO2 concentration data from temporary campaigns performed at six CARBOEUROFLUX forest sites were used to estimate the importance of non-turbulent fluxes in nighttime conditions. While storage was observed to be significant only during periods of both low turbulence and low advection, the advective fluxes strongly influence the nocturnal CO2 balance, with the exception of almost flat and highly homogeneous sites. On the basis of the main factors determining the onset of advective fluxes, the 'advection velocity', which takes net radiation and local topography into account, was introduced as a criterion to characterise the conditions of storage enrichment/depletion. Comparative analyses of the six sites showed several common features of the advective fluxes but also some substantial differences. In particular, all sites where advection occurs show the onset of a boundary layer characterised by a downslope flow, negative vertical velocities and negative vertical CO2 concentration gradients during nighttime. As a consequence, vertical advection was observed to be positive at all sites, which corresponds to a removal of CO2 from the ecosystem. The main differences between sites are the distance from the ridge, which influences the boundary-layer depth, and the sign of the mean horizontal CO2 concentration gradients, which is probably determined by the source/sink distribution. As a consequence, both positive and negative horizontal advective fluxes (corresponding respectively to CO2 removal from the ecosystem and to CO2 supply to the ecosystem) were observed. Conclusive results on the importance of non-turbulent components in the mass balance require, however, further experimental investigations at sites with different topographies, slopes, different land covers, which would allow a more comprehensive analysis of the processes underlying the occurrence of advective fluxes. The quantification of these processes would help to better quantify nocturnal CO2 exchange rates. [less ▲]

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See detailQuality Analysis Applied On Eddy Covariance Measurements At Complex Forest Sites Using Footprint Modelling
Rebmann, C.; Gockede, M.; Foken, T. et al

in Theoretical and Applied Climatology (2005), 80(2-4),

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See detailModel Of Forest Carbon Sequestration Incorporating Aerial Wood Radiative Budget
Longdoz, B.; Aubinet, Marc ULg; François, Louis ULg

in Agricultural and Forest Meteorology (2004), 125(1-2), 83-104

The CHANCE model, simulating CO2, energy and water fluxes in a forest ecosystem, is presented. The components of the simulated canopy are the leaves, the branches, the trunks and the soil. The first three ... [more ▼]

The CHANCE model, simulating CO2, energy and water fluxes in a forest ecosystem, is presented. The components of the simulated canopy are the leaves, the branches, the trunks and the soil. The first three are divided into sunny and shaded zones. The model has been calibrated and validated in comparison with measurements performed in the temperate beech forest of Vielsalm (Belgium). For the reproduction of half-hourly net CO2 fluxes, the quality of the CHANCE results is comparable to other models (systematic error of 14%—0.51 molm−2 s−1, R2 = 0.79). The differences between simulated and measured fluxes result essentially from noise in the data, underestimation of the stomatal conductance during very dry days and heterogeneity of the south, southeast sector (presence of conifer patches). Three sensitivity tests have been performed. The first one, neglecting the contribution of aerial wood in the radiation budget, doubles the annual carbon sequestration (Seco). This trend is strengthened in the second test where common radiative and photosynthetic properties are assigned to leaves and branches. The third test induces a 30% reduction of Seco when the calculation of canopy component temperatures using the complete energy balance is replaced by the use of air temperature. © 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailProductivity Overshadows Temperature In Determining Soil And Ecosystem Respiration Across European Forests
Janssens, Ia.; Lankreijer, H.; Matteucci, G. et al

in Global Change Biology (2001), 7(3),

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See detailLong Term Carbon Dioxide Exchange Above A Mixed Forest In The Belgian Ardennes
Aubinet, Marc ULg; Chermanne, B.; Vandenhaute, M. et al

in Agricultural and Forest Meteorology (2001), 108(4),

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