NitroEurope - or NEU for short - is a project for integrated European research into the nitrogen cycle. NitroEurope is part of the EU's Sixth Framework Programme for Research and Technological Development, and will run for 5 years from February 2006 until 2011.
The impact of changes in atmospheric deposition and climate on forest growth in European monitoring plots: An empirical stand growth model.
Submitted by wim_de_vries on Tue, 07/04/2009 - 18:21.
Publication Type:
Journal Paper (submitted)Source:
Forest Ecology and Management (2009)Keywords:
European forests; growth; empirical model; carbon sequestration; monitoring; nitrogen deposition; acid deposition; climate change; drought.Abstract:
Forest growth in Europe has increased. Data from Intensive Monitoring Plots for a five years period were the basis to examine the influence of environmental factors on forest growth. Evaluations focussed on the influence of nitrogen, sulphur and acid deposition, temperatures, precipitation and on a drought index calculated as deviation from the long-term mean. The study included the main tree species Norway spruce, Scots pine, common beech as well as European and sessile oak and was based on data from 363 plots. As many other factors besides nitrogen and temperature influence tree growth, expected growth was modelled using site productivity, stand age and a stand density index. Relative tree growth was then calculated as actual growth in % of expected growth. The site productivity, assumed to be given by site conditions and past environmental conditions, was either taken from expert estimates or computed from site index curves from Northern, central and Southern Europe. The model explained between 18% and 39% of the variance with site productivity being positively related and age negatively related to actual growth. The various models and statistical approaches were fairly consistent, and indicated a fertilizing effect of nitrogen deposition, with one percent increase in site productivity per kg of nitrogen deposition per ha and year. This was most clear for spruce and pine, and most pronounced for plots having soil C/N ratios above 25. Also, we found a positive relationship between relative growth and summer temperature, i.e. May-August mean temperature deviation from the 1961-1990 means. The cause-effect relationship here is however, less certain. Other influences were uncertain. Possibly, sulphur and acid deposition have effects on growth, but these effects are obscured by, and outweighed by the positive effect of nitrogen deposition, because of co-linearity between these variables. Drought effects were uncertain also, and one reason for this might be large uncertainties in the precipitation data: Precipitation measured on some 50% of the plots correlated poorly with the precipitation data obtained from European wide databases. The major finding of this study was a positive relationship between higher than normal volume growth on one hand and nitrogen deposition on the other hand. The average estimated growth increase per kg of N deposition was estimated to correspond with an increase between 33 and 49 kg wood per year or 16-25 kg C per kg N.
