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The Seasonal Effects on Nitrogen Uptake from 15N-labelled Leaf Litter in European Beech (Fagus sylvatica L.)

  • Author(s): Guo, Chanjuan
  • Simon, Judy
  • Rennenberg, Heinz
  • et al.
Abstract

In a field study with beech seedlings, the decomposition and fate of nitrogen from 15N-labelled leaf litter and its seasonal effects on nitrogen uptake and metabolism were analysed during one growing season in a beech-dominated deciduous forest in a low mountain range in southern Germany. At this site, European beech is the main species making up more than 90% of the total basal area of adult trees. For this purpose, young beech trees from replicate plots exposed to 15N-labelled litter or non-labelled litter (as controls) were sampled in early June and September 2008. The amounts of 15N and total N were determined for leaves, stems, fine and coarse roots. Furthermore, the concentrations of total amino acids, soluble protein, nitrate and ammonium were quantified in fine roots. After 6 months of litter decomposition, δ15N signatures increased in leaves compared to those in stems and coarse roots, but the concentration of 15N was still lower than in fine roots. Simultaneously, also total N in fine roots, coarse roots and stems increased, but not total N in leaves. In addition, amounts of both, total amino acids and soluble protein of fine roots increased during the growing season. It appears that newly accumulated nitrogen in the leaves originates from the leaf litter and was allocated during the growing season via fine roots, coarse roots and the stem into the leaves. The increase in total nitrogen in roots can be explained as intrinsic nitrogen originating from storage or as external nitrogen originating from sources others than leaf litter, for example deeper soil layers.

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