Report - ICP Forests

38 2. Large Scale Crown Condition Surveys
2.2.2.6 Quercus robur and Q. petraea
Defoliation of Quercus robur and Quercus
petraea had two peaks since 1991. The
share of damaged trees amounted to 41.1%
in 1997 and in 2005 it reached 42.9%. A
recuperation has been observed in 2006,
whereas in the last three years defoliation
remained rather unchanged (Figure 2.2.2.6-
1).
A deterioration in health of both oak species
was found on 25.7% of the plots in the map
whereas on only 7.7% of the plots health
status improved in the years 1998 to 2009.
Most Quercus robur and Quercus petraea
plots occur in France. Here, as well as in
Czech Republic and northern Spain plots
with deteriorating defoliation are more
frequent than plots with improvements. This
trend is reverse in Croatia (Figure 2.2.2.6-
2).
N trees 0-10% >10-25% >25%
1991 5732 45.0 32.2 22.8
1992 5296 42.4 35.0 22.5
1993 5379 36.9 32.9 30.1
1994 5598 34.1 31.8 34.1
1995 5451 33.1 36.4 30.6
1996 5424 24.7 39.0 36.3
1997 5437 16.3 42.6 41.1
1998 5591 20.5 42.5 37.0
1999 5711 20.4 47.8 31.7
2000 5740 21.0 48.3 30.7
2001 5758 19.1 49.4 31.4
2002 5771 18.4 50.9 30.7
2003 5770 14.7 47.2 38.1
2004 5872 15.0 44.6 40.4
2005 5882 13.5 43.6 42.9
2006 5388 17.1 46.1 36.8
2007 5494 15.9 47.0 37.1
2008 5647 15.7 48.0 36.2
2009 5580 17.9 46.6 35.5
N trees 0-10% >10-25% >25%
1998 6766 20.2 41.6 38.2
1999 6797 21.1 47.3 31.6
2000 6890 20.2 46.5 33.3
2001 6834 19.1 48.2 32.6
2002 6678 19.0 50.7 30.4
2003 6679 15.5 47.6 37.0
2004 6800 16.3 44.4 39.3
2005 6867 14.8 43.4 41.8
2006 6362 19.4 45.6 35.1
2007 6494 17.8 47.5 34.8
2008 6643 17.2 48.8 34.0
2009 6929 19.3 48.1 32.6
Percent of trees
100
80
60
40
0-10% (91-09)
>25% (91-09)
0-10% (98-09)
>25% (98-09)
20
0
1991
1993
1995
1997
1999
Year
Figure 2.2.2.6-1: Shares of trees of defoliation 0-10%
and >25% in two periods (1991-2009 and 1998-2009).
2001
2003
2005
2007
2009