title: Competition for nitrogen between European beech and sycamore maple shifts in favour of beech with decreasing light availability.
abstract: Plant species use different strategies for maximizing growth and fitness under changing environmental conditions. At the ecosystem level, seedlings in particular compete with other vegetation components for light and nitrogen (N), which often constitute growth-limiting resources. In this study, we investigated the effect of light availability on the competition for N between seedlings of European beech and sycamore maple and analysed the consequences of this competition for the composition of N metabolites in fine roots. Our results show different strategies in N acquisition between beech and sycamore maple. Both species responded to reduced light availability by adapting their morphological and physiological traits with a decrease in biomass and net assimilation rate and an increase in specific leaf area and leaf area ratio. For beech seedlings, competition with sycamore maple led to a reduction in organic N uptake capacity. Reduced light availability led to a decrease in ammonium, but an increase in glutamine-N uptake capacity in sycamore maple. However, this response was stronger compared with that of beech and was accompanied by reduced growth. Thus, our results suggest better adaptation of N acquisition to reduced light availability in beech compared with sycamore maple seedlings.
authors.affiliation: Institute of Forest Sciences, Chair of Tree Physiology, University of Freiburg, Georges-Koehler-Allee 53/54, 79110 Freiburg, Germany.
authors.forename: Judy
authors.initials: J
authors.lastname: Simon
authors.forename: Xiuyuan
authors.initials: X
authors.lastname: Li
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
mesh_terms: D031002:Acer / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D000222:Adaptation, Physiological; D064751:Ammonium Compounds / Q000378:metabolism; D018533:Biomass; D002247:Carbon Isotopes / Q000032:analysis; D029964:Fagus / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D005973:Glutamine / Q000378:metabolism; D008027:Light; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D012987:Soil; D014197:Trees
chemical_list: D064751:Ammonium Compounds; D002247:Carbon Isotopes; D009566:Nitrates; D009587:Nitrogen Isotopes; D012987:Soil; D005973:Glutamine; D009584:Nitrogen
keywords: amino acids; ammonium; nitrate; nitrogen nutrition; nitrogen uptake capacity; soluble protein