Consequences of elevated CO2, augmented nitrogen‐deposition and soil type on the soluble nitrogen and sulphur in the phloem of beech (Fagus sylvatica) and spruce (Picea abies) in a competitive situation
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Media type:
E-Article
Title:
Consequences of elevated CO2, augmented nitrogen‐deposition and soil type on the soluble nitrogen and sulphur in the phloem of beech (Fagus sylvatica) and spruce (Picea abies) in a competitive situation
Description:
<jats:p>Mixed spruce‐beech plantations grown in large open‐top chambers (OTC) were used to study consequences of elevated CO<jats:sub>2</jats:sub>, nitrogen‐deposition and soil type on plant internal nitrogen and sulphur cycling of juvenile beech (<jats:italic>Fagus sylvatica</jats:italic> L.) and spruce (<jats:italic>Picea abies</jats:italic> Karst.) in a competitive situation. Processes of re‐cycling as a consequence of protein turnover during leaf senescence in autumn were of further interest. For this purpose, phloem sap was collected in September 1998 and analysed for the composition and concentrations of organic and inorganic nitrogen and sulphur compounds. The phloem exudate of spruce showed higher total soluble non‐protein nitrogen (TSNN) concentration on calcareous soil than on acidic soil, independent of the treatment. N‐fertilization increased the N‐concentration of phloem exudate significantly on both soil types, mainly by an increase of Arg and Gln concentrations. Elevated CO<jats:sub>2</jats:sub> slightly increased TSNN on calcareous, but not on acidic soil. The combination of elevated CO<jats:sub>2</jats:sub> and augmented N‐deposition induced a further increase of TSNN on calcareous soil, but caused a lower N‐effect on TSNN on acidic soil. Arg, the main TSNN component in phloem exudate, mediated this effect. Since Arg is considered to be a major nitrogen storage compound, it is concluded that in autumn elevated CO<jats:sub>2</jats:sub> and augmented N‐deposition, influence storage of N rather than N‐supply of spruce. An effect of elevated CO<jats:sub>2</jats:sub> and augmented N‐deposition on GSH and sulphate concentrations in phloem exudate of spruce was not observed on acidic soil. On calcareous soil augmented N‐deposition enhanced, elevated CO<jats:sub>2</jats:sub> decreased phloem exudate GSH contents. In combination, elevated CO<jats:sub>2</jats:sub> compensated the positive effect of N‐deposition. The effects of elevated CO<jats:sub>2</jats:sub> and augmented N‐deposition on phloem sap N‐ and S‐contents described above were not observed for beech trees. Apparently, elevated CO<jats:sub>2</jats:sub> and augmented N‐deposition did not affect plants internal S and N cycling of beech grown in spruce‐beech plantations.</jats:p>