Report - ICP Forests

50 3. Intensive Monitoring
3.2.2.2 Temporal variation
Earlier reports described a decrease in sulphur deposition based on periods of the last 6 available
years with data submission. As nowadays also longer time series can be calculated without a
significant reduction in number of observations compared to a six years period, the deposition in
the 10 years from 1998 to 2007 was the basis for the present study. Figure 3.2.2.2-1 shows the
decrase of mean annual sulphur deposition from 1998 to 2007. The strong decrease in sulphur
deposition in the exceptionally dry year 2003 reflects its dependance from precipitation (not
depicted). Nevertheless, the strong decrease in sulphur deposition from 1998 to 2007 (e.g. for
sulphur throughfall deposition from 10.0 to 6.6 kg per ha and year) indicates a clear reduction of
sulphur depsosition in this period. Thus, the influence of precipitation on deposition is
considerable, but the observed decrease in deposition (see also Figures 3.2.2.2-3 and 3.2.2.2-4)
over 10 years is not mainly a result of decreasing precipitation (LORENZ et al. 2008).
12
[kg / ha-a]
11
10
9
8
7
6
5
S_SO4 througfall (157)
S_SO4 bulk (151)
S_SO4 througfall (no seasalt) (157)
S_SO4 bulk (no seasalt) (151)
4
3
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Figure 3.2.2.2-1:
year
Changes in mean annual bulk and throughfall deposition (with standard error of the mean) of
sulphate, with and without correction for sea salt, from 1998 to 2007.
The temporal development of ammonium and nitrate deposition is shown in Figure 3.2.2.2-2.
Whereas for bulk deposition a more or less clear decrease in nitrogen deposition is observed,
this is not the case for throughfall. This is as well reflected by the maps of the plot specific
regression slopes in Figures 3.2.2.2-5 to 3.2.2.2-8. A significant increase in nitrogen throughfall
deposition was even observed on some plots scattered across Europe.