References of "Ibrom, A"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailInterpreting canopy development and physiology using a European phenology camera network at flux sites
Wingate, L.; Ogée, J.; Cremonese, E. et al

in Biogeosciences (2015), 12(10), 5995-6015

Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant development stages and ... [more ▼]

Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant development stages and their response to climate and management practices are crudely represented in land surface models. As visual observations of phenology are laborious, there is a need to supplement long-term observations with automated techniques such as those provided by digital repeat photography at high temporal and spatial resolution. We present the first synthesis from a growing observational network of digital cameras installed on towers across Europe above deciduous and evergreen forests, grasslands and croplands, where vegetation and atmosphere CO2 fluxes are measured continuously. Using colour indices from digital images and using piecewise regression analysis of time series, we explored whether key changes in canopy phenology could be detected automatically across different land use types in the network. The piecewise regression approach could capture the start and end of the growing season, in addition to identifying striking changes in colour signals caused by flowering and management practices such as mowing. Exploring the dates of green-up and senescence of deciduous forests extracted by the piecewise regression approach against dates estimated from visual observations, we found that these phenological events could be detected adequately (RMSE < 8 and 11 days for leaf out and leaf fall, respectively). We also investigated whether the seasonal patterns of red, green and blue colour fractions derived from digital images could be modelled mechanistically using the PROSAIL model parameterised with information of seasonal changes in canopy leaf area and leaf chlorophyll and carotenoid concentrations. From a model sensitivity analysis we found that variations in colour fractions, and in particular the late spring `green hump' observed repeatedly in deciduous broadleaf canopies across the network, are essentially dominated by changes in the respective pigment concentrations. Using the model we were able to explain why this spring maximum in green signal is often observed out of phase with the maximum period of canopy photosynthesis in ecosystems across Europe. Coupling such quasi-continuous digital records of canopy colours with co-located CO2 flux measurements will improve our understanding of how changes in growing season length are likely to shape the capacity of European ecosystems to sequester CO2 in the future. [less ▲]

Detailed reference viewed: 41 (7 ULg)
See detailMethodology for data acquisition, storage and treatment
Aubinet, Marc ULg; Clément, R.; Elbers, J. A. et al

in Valentini, R. (Ed.) Fluxes of Carbon, Water and Energy of European Forests (2003)

Detailed reference viewed: 23 (0 ULg)
See detailSpruce forests (Norway and Sitka spruce, including Douglas fir): Carbon and water fluxes, Balances, Ecological and ecophysiological determinants
Bernhofer, C.; Aubinet, Marc ULg; Clément, R. et al

in Valentini, Riccardo (Ed.) Fluxes of Carbon, Water and Energy of European Forests (2003)

Detailed reference viewed: 57 (0 ULg)
Full Text
Peer Reviewed
See detailEnergy Balance Closure At Fluxnet Sites
Wilson, K.; Goldstein, A.; Falge, E. et al

in Agricultural and Forest Meteorology (2002), 113(1-4),

Detailed reference viewed: 20 (3 ULg)
Full Text
Peer Reviewed
See detailCarbon balance gradient in European forests: should we doubt 'surprising' results? A reply to Piovesan & Adams
Jarvis, P. G.; Dolman, A. J.; Schulze, E. D. 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: 36 (1 ULg)
Full Text
Peer Reviewed
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),

Detailed reference viewed: 37 (1 ULg)
Peer Reviewed
See detailRespiration As The Main Determinant Of Carbon Balance In European Forests
Valentini, R.; Matteucci, G.; Dolman, Aj. et al

in Nature (2000), 404(6780),

Detailed reference viewed: 50 (4 ULg)
Full Text
Peer Reviewed
See detailEstimates of the annual net carbon and water exchange of forests: the EUROFLUX methodology.
Aubinet, Marc ULg; Grelle, A.; Ibrom, A. et al

in Advances in Ecological Research (1999), 30

Detailed reference viewed: 778 (21 ULg)