title: Seasonal and within-canopy variation in shoot-scale resource-use efficiency trade-offs in a Norway spruce stand.
abstract: Previous leaf-scale studies of carbon assimilation describe short-term resource-use efficiency (RUE) trade-offs where high use efficiency of one resource requires low RUE of another. However, varying resource availabilities may cause long-term RUE trade-offs to differ from the short-term patterns. This may have important implications for understanding canopy-scale resource use and allocation. We used continuous gas exchange measurements collected at five levels within a Norway spruce, Picea abies (L.) karst., canopy over 3 years to assess seasonal differences in the interactions between shoot-scale resource availability (light, water and nitrogen), net photosynthesis (An ) and the use efficiencies of light (LUE), water (WUE) and nitrogen (NUE) for carbon assimilation. The continuous data set was used to develop and evaluate multiple regression models for predicting monthly shoot-scale An . These models showed that shoot-scale An was strongly dependent on light availability and was generally well described with simple one- or two-parameter models. WUE peaked in spring, NUE in summer and LUE in autumn. However, the relative importance of LUE for carbon assimilation increased with canopy depth at all times. Our results suggest that accounting for seasonal and within-canopy trade-offs may be important for RUE-based modelling of canopy carbon uptake.
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Umeå, SE-901 83, Sweden.|Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, SE-405 30, Sweden.
authors.forename: Lasse
authors.initials: L
authors.lastname: Tarvainen
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, SE-405 30, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Räntfors
authors.affiliation: Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, SE-405 30, Sweden.
authors.forename: Göran
authors.initials: G
authors.lastname: Wallin
mesh_terms: D002244:Carbon / Q000378:metabolism*; D019069:Cell Respiration; D008027:Light; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism; D010788:Photosynthesis; D028222:Picea / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration; D012044:Regression Analysis; D012621:Seasons
chemical_list: D002244:Carbon; D009584:Nitrogen
keywords: Picea abies; light-use efficiency; nitrogen-use efficiency; photosynthesis; stomatal conductance; transpiration; water-use efficiency