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Competition for nitrogen between adult European beech and its offspring is reduced by avoidance strategy |
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| Authors: | Judy Simon Michael Dannenmann Rainer Gasche Jutta Holst |
| Institution: | a Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, University of Freiburg, Georges-Koehler-Allee 53/54, 79110 Freiburg, Germany b Institute for Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Forschungszentrum Karlsruhe GmbH, Kreuzeckbahnstrasse 19, 82467 Garmisch-Partenkirchen, Germany c Meteorological Institute, University of Freiburg, Werthmannstrasse 10, 79085 Freiburg, Germany d University of Freiburg, Goerges-Koehler-Allee 53/54, 79110 Freiburg, Germany and King Saud University, Riyadh, Saudi Arabia |
| Abstract: | Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e., seedlings, mature trees, other woody and herbaceous understorey). This study investigated in a field experiment whether the competition for N between different vegetation components in beech forests was prevented via seasonal timing of N uptake and affected by microbial N use. For this purpose, a removal approach was used to study the seasonal effects on N uptake and N metabolites in adult beech trees and beech natural regeneration, as well as soil microbial processes of inorganic N production and utilisation. We found that the competition for N between beech natural regeneration and mature beech trees was reduced by seasonal avoidance strategies (“good parenting”) of N uptake regardless of the N sources used. In spring, organic and inorganic N uptake capacity was significantly higher in beech seedlings compared to adult beech trees, whereas in autumn mature beech trees showed the highest N uptake rates. Removal of vegetation components did not result in changes in soil microbial N processes in the course of the growing season. Thus, N resources released by the removal of vegetation components were marginal. This consistency in soil microbial N processes indicates that competition between plants and soil microorganisms for N was not avoided by timing of acquisition during the vegetation period, but existed during the entire growing season. In conclusion, N nutrition in the studied forest ecosystem seems to be optimally attuned to European beech. |
| Keywords: | Fagus sylvatica N uptake N metabolites Soil microorganisms Soil N processes Removal approach |
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