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Characterisation of ecosystem water-use efficiency of european forests from eddy covariance measurements

Title data

Kuglitsch, F. G. ; Reichstein, Markus ; Beer, Christian ; Carrara, A. ; Ceulemans, Reinhart ; Granier, André ; Janssens, Ivan A. ; Köstner, Barbara ; Lindroth, Anders ; Loustau, Dennis ; Matteucci, G. ; Montagnani, Leonardo ; Moors, Eddy ; Papale, Dario ; Pilegaard, Kim ; Rambal, Serge ; Rebmann, Corinna ; Schulze, Ernst-Detlef ; Seufert, Günther ; Verbeeck, H. ; Vesala, Timo ; Aubinet, Marc ; Bernhofer, Christian ; Foken, Thomas ; Grünwald, Thomas ; Heinesch, Bernard ; Kutsch, Werner ; Laurila, T. ; Longdoz, B. ; Miglietta, Franco ; Sanz, M. J. ; Valentini, Riccardo:
Characterisation of ecosystem water-use efficiency of european forests from eddy covariance measurements.
In: Biogeosciences Discussions. Vol. 5 (2008) . - pp. 4481-4519.
ISSN 1810-6285

Abstract in another language

Water-use efficiency (WUE) has been recognized as an important characteristic of vegetationproductivity in various natural scientific disciplines for decades, but only recently at the ecosystem level, where different ways exist to characterize water-use efficiency. Hence, the objective of this research was (a) to systematically compare different ways of calculating ecosystem water-use efficiency (WUEe) from eddy-covariance measurements,(b) quantify the diurnal, seasonal and interannual variability of WUEe in relation to meteorological conditions, and (c) analyse between-site variability of WUEe asaffected by vegetation type and climatic conditions, across sites in European forest ecosystems.Day-to-day variability of gross primary productivity (GPP) and evapotranspiration (ET) were more strongly coupled than net ecosystem production (NEP) and ET, obviouslybecause NEP also depends on the respiration that is not heavily coupled to water fluxes. However, the slope of daytime NEP versus ET (mNEP) from half-hourly measurements of a single day may also be used as a WUEe-estimate giving very similar results to those of the GPP-ET slope (mGPP), since the diurnal variation is dominated by GPP. Since ET is the sum of transpiration (linked to GPP) and evaporation from wet vegetation and soil surfaces (not linked to GPP) we expected that WUEe is increasing when days after rain are excluded from the analysis. However only very minor changes were found, justifying an analysis of WUEe related to vegetation type.In most of the studied ecosystems the instantaneous WUEGPP was quite sensitive to diurnally varying meteorological conditions and tended to decline from the morning to the afternoon by more than 50% because of increasing vapour pressure deficits (VPD).Seasonally, WUEGPP increased with a rising monthly precipitation sum and rising average monthly temperatures up to a threshold of 11, 14 and 18C in boreal, temperateand Mediterranean ecosystems, respectively. Across all sites, the highest monthly WUEGPP-values were detected at times of positive anomalies of summer-precipitation.During drought periods with high temperatures, high VPD, little precipitation and low soil water content, the water-use efficiency of gross carbon uptake (WUEGPP) tended to decrease in all forest types because of a stronger decline of GPP compared to ET.However the largest variation of growing season WUEGPP was found betweensites and significantly related to vegetation type: WUEGPP was highest in ecosystems dominated by deciduous trees ranging from 5.0 gCO2 kgH2O−1 for temperate broadleaved deciduous forests (TD), to 4.5 for temperate mixed forests (TM), 3.5 for temperate evergreen conifers (TC), 3.4 for Mediterranean broad-leaved deciduous forests (MD), 3.3 for Mediterranean broad-leaved evergreen forests (Mbeg), 3.1 for Mediterranean evergreen conifers (MC), 2.9 for boreal evergreen conifers (BC) and only 1.2 g CO2 kgH2O−1 for a boreal wetland site (BT). Although vegetation type and meteorology co-vary, the WUEGPP variation was hardly related to meteorology, as we could show by comparing similar meteorological conditions only. Furthermore we compared across-site WUEGPP only under conditions when the 10% high GPP rates were exhibited.The between site differences remained, and at all sites ecosystem reached higher WUEGPP levels under this condition. This means when vegetation is most productive usually it also maximises the amount of carbon gained per water lost.Overall our results show that water-use efficiency exhibits a strong time-scale dependencyin the sense that at longer time-scale meteorological conditions play a smallerrole compared to shorter time scale. Moreover, we highlight the role of vegetation in determining carbon-water relation at ecosystem level. Consequently, all predictions of changing carbon-water cycle under changing climate should take into this role and the differences between vegetation types. These results show the strong time-scale dependency of water-use efficiency

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER66098
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Former Professors > Professor Micrometeorology - Univ.-Prof. Dr. Thomas Foken
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Former Professors
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 31 Aug 2015 05:50
Last Modified: 21 Apr 2022 13:24