title: Seasonal variation in N uptake strategies in the understorey of a beech-dominated N-limited forest ecosystem depends on N source and species.
abstract: In forest ecosystems, species use different strategies to increase their competitive ability for nitrogen (N) acquisition. The acquisition of N by trees is regulated by tree internal and environmental factors including mycorrhizae. In this study, we investigated the N uptake strategies of three co-occurring tree species [European beech (Fagus sylvatica L.), sycamore maple (Acer pseudoplatanus L.) and Norway maple (Acer platanoides L.)] in the understorey of a beech-dominated, N-limited forest on calcareous soil over two consecutive seasons. For this purpose, we studied (15)N uptake capacity as well as the allocation to N pools in the fine roots. Our results show that European beech had a higher capacity for both inorganic and organic N acquisition throughout the whole growing season compared with sycamore maple and Norway maple. The higher capacity of N acquisition in beech indicates a better adaption of beech to the understorey conditions of beech forests compared with the seedlings of other tree competitors under N-limited conditions. Despite these differences, all three species preferred organic over inorganic N sources throughout the growing season and showed similar seasonal patterns of N acquisition with an increased N uptake capacity in summer. However, this pattern varied with N source and year indicating that other environmental factors not assessed in this study further influenced N acquisition by the seedlings of the three tree species.
authors.affiliation: Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, 79098 Freiburg, Germany.
authors.forename: Xiuyuan
authors.initials: X
authors.lastname: Li
authors.affiliation: Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, 79098 Freiburg, Germany.
authors.forename: Heinz
authors.initials: H
authors.lastname: Rennenberg
authors.affiliation: Chair of Tree Physiology, Institute of Forest Sciences, University of Freiburg, 79098 Freiburg, Germany Plant Physiology and Biochemistry, Department of Biology, University of Konstanz, 78457 Konstanz, Germany judy.simon@uni-konstanz.de.
authors.forename: Judy
authors.initials: J
authors.lastname: Simon
mesh_terms: D031002:Acer / Q000254:growth & development / Q000378:metabolism*; D029964:Fagus / Q000254:growth & development / Q000378:metabolism*; D065928:Forests; D005858:Germany; D009584:Nitrogen / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D013045:Species Specificity
chemical_list: D009584:Nitrogen
keywords: N allocation patterns; N pools; inorganic N; net N uptake; organic N