© 2001 Heron Publishing—Victoria, Canada
Influence of tree internal N status on uptake and translocation of C and N in beech: a dual 13C and 15N labeling approach
Jens Dyckmans (1) and Heiner Flessa (1)
1. Institute of Soil Science and Forest Nutrition, University of Göttingen, Büsgenweg 2, 37077 Göttingen, Germany / Received June 14, 2000
Summary
Influence of plant internal nitrogen (N) stocks on carbon (C) and N uptake and allocation in 3-year-old beech (Fagus sylvatica L.) was studied in two 15N- and 13C-labeling experiments. In the first experiment, trees were grown in sand and received either no N nutrition (–N treatment)
or 4 mM unlabeled N (+N treatment) for 1 year. The –N- and +N-pretreated trees were then supplied with 4 mM 15N and grown in a 13CO2 atmosphere for 24 weeks. In the second experiment, trees were pretreated with 4 mM 15N for 1 year and then supplied with unlabeled N for 24 weeks and the remobilization of stored 15N was monitored.
On the whole-plant level, uptake of new C was significantly reduced in –N-pretreated trees; however, partitioning of new C
was not altered, although there was a trend toward increased belowground respiration. The amount of N taken up was not influenced
by N nutrition in the previous year. In +N-pretreated trees, partitioning of new N was dominated by the fine roots (59.7%
at Week 12), whereas in –N-pretreated trees, partitioning of new N favored stem, coarse roots and fine roots (24, 21 and 31.9%,
respectively, at Week 12), indicating the formation of N stores. The contribution of previous-year N to leaf N was about 15%.
The N remobilized for leaf formation had been stored in stem and coarse roots. We conclude that, within a growing season,
the growth of beech is strongly determined by the availability of tree internal N stores, whereas the current N supply is
of less importance.
Keywords:
carbon uptake, Fagus sylvatica, nitrogen remobilization, nitrogen storage, nutrient cycling, stable isotope.
