Nitrogen fluxes in two Norway spruce stands in Austria: An analysis by means of process-based modelling

Leopoldsdorf

2004

S. 167-182

2 Abb., 5 Ta., 25 Lit. Ang.

Artikel aus einer ZeitschriftUnselbständiges Werk

200119167

Recent studies have shown that the growth rate of many European forests has increased during the 2nd half of the 20th century, mainly because of higher rates of atmospheric nitrogen deposition. In contrast, studies using process-based models suggested that increased N-deposition had not enhanced growth in conifer forests in northern Austria. These results were the more unexpected because N-deposition had increased strongly at the sites. Here, we analyse the modelling results in depth to identify possible causes for the lack of response on the Austrian sites, Helfenberg and Karlstift. The analysis suggests that sensitivity of forests to N-deposition may be more closely linked to indirect effects of deposition, i.e. stimulation of soil nitrogen mineralisation because of enhanced litter quality, than to the direct contribution of deposition to the pool of available nitrogen. The indirect effect of stimulating mineralisation may have been smaller at the Austrian sites than elsewhere because of nitrogen saturation in soil and trees, such that litter quality was insensitive to extra N-inputs.