Ecosystem transpiration and evaporation: Insights from three water flux partitioning methods across FLUXNET sites

Abstract

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The three major axes of terrestrial ecosystem function

“…For each site, we calculated a single set of functional properties (see ‘Calculation of ecosystem functions from FLUXNET’ in Methods for details on the calculation and definition of abbreviations): maximum gross CO 2 uptake at light saturation (GPP s at ), maximum net ecosystem productivity (NEP max ), maximum evapotranspiration (ET max ), evaporative fraction (EF) (that is, the ratio between latent heat flux and available energy, indicative of energy partitioning), EF amplitude (EF ampl ), maximum dry canopy surface conductance ( G smax ), maximum and mean basal ecosystem respiration (Rb max and Rb, respectively), and apparent carbon-use efficiency (aCUE) (that is, the remaining fraction of carbon entering the ecosystem). We also computed several metrics of growing season water-use efficiency (WUE) that account in different ways for physical evaporation and stomatal regulation effects: underlying WUE (uWUE), stomatal slope at ecosystem scale (G1), and WUE t , a second variant of WUE, but based on transpiration estimates 11 (see Methods ). We calculated average climate and soil water availability variables for each site, encompassing the following: cumulative soil water availability index (CSWI), mean annual precipitation ( P ), mean shortwave incoming radiation (SW in ), mean air temperature ( T air ), and mean vapour pressure deficit during the growing season (VPD).…”

Effects of conventional, extensive and semi-intensive green roofs on building conductive heat fluxes and surface temperatures in winter in Paris

“…The presence of substrate is therefore of a key importance for the assessment of building insulation during winter, and its thickness the main factor controlling its efficiency since vegetation is sparse and weakly evapotranspirates under such conditions, whatever the kind of green roof (i.e., EXT or SI) considered. Indeed, the grass transpiration under winter conditions only accounts for a small part of the total evapotranspiration, between 5-20% [51]. Hence, although the vegetation densities are quite different between EXT and SI green roofs (with a percentage of plant cover of approximatively 20-25% for EXT and 100% for SI, which is partly composed of yellow and inactive leaves), it could be expected that the total evapotranspiration is mainly driven by soil evaporation during winter conditions, which depends on atmospheric conditions (identical for the two roofs) and substrate water content (always close to the field capacity during the experiment).…”

New Representation of Plant Hydraulics Improves the Estimates of Transpiration in Land Surface Model

“…The total species basal area at each site in the datasets are more than 90% of the stand area. At the last, stand-level T could be calculated by summing species-level T [28]. All the data mentioned above can be found in the SAP-FLUXNET.…”