Report - ICP Forests

84 3. Intensive Monitoring
should be noted that an increase in the number of species is often found in re-evaluations of
permanent plots. In this case, N-deposition is rather improbable as a cause because no
significant relation with deposition was found. Also climate change is rather improbable as a
cause because Ellenberg's temperature indicator did not change at all. The simplest explanation
is that in a second visit to the plot the observer has a better knowledge of the species which
increases the probability to find extra species. This is particularly true if a list of species that
were found previously is taken into the field. However, this explanation fails to explain the
significant positive correlation with fertile soil and negative correlation with the Mediterranean.
3.4.6 References
De Vries, W., Reinds, G.J., Van Dobben, H., De Zwart, D., Aamlid, D., Neville, P., Posch, M.,
Auee, J., Voogd, J.C.H., Vel, E.M. (2002): Intensive Monitoring of Forest Ecosystems in
Europe. 2002 Technical Rapport. EC, UN/ECE, Brussels, Geneva. Available through:
http://www.icp-forests.org/pdf /TRLII2002.pdf.
Ellenberg, H. (1991): Zeigerwerte der Gefäßpflanzen (ohne Rubus). Scripta Geobotanica 18:9-
166.
Tarrasón, L., Fagerli, H., Jonson, J.E., Simpson, D., Benedictow, A., Klein, H., Vestreng, V.,
Aas, W., Hjellbrekke, A.-G. (2007): Transboundary acidification, eutrophication and
ground level ozone in Europe in 2005. EMEP Report 1/2007. Norwegian Meteorological
Institute, Oslo, Norway.
Van Duuren, L., Eggink, G.J., Kalkhoven., J., Notenboom., J., Van Strien., A.J., Wortelboer, R.
(eds) (2003): Natuurcompendium. PBL, Bilthoven.