KAZALCI OKOLJA

Key message
Neutral

The health status of forests in Slovenia has been relatively stable in recent years, but with a slight negative trend. In 2014 and 2015 we observed an increased defoliation, due to ice storm and wind throws, followed by a stable defoliation status in both - conifers and deciduous trees. In 2020, for the first time, the average defoliation of conifers was lower than the average defoliation of deciduous trees.

In general, the average defoliation in Slovenian forests is 28% (2020) - still higher than the average of the European Union, where in 2019 it was 23%. The trend of increasing defoliation is also observed at the European level.

The most damaged tree species are black pine, sweet chestnut, black locust, oaks (especially Q.robur), common beech, hornbeam and Norway spruce. According to recent findings, annual differences in estimates are mainly a combination of the unforeseen weather conditions between years and other biotic and abiotic causes.


Charts

Figure GZ01-1: Trend of average tree defoliation
Sources:

Slovenian Forestry Institute 2021 (12. 05. 2021)

Show data
coniferous[%] deciduous[%] total[%]
1991 22.14 12.95 16.56
1993 22.46 15.68 19.59
1994 18.53 16.30 18.29
1995 26.86 18.07 21.42
1996 22.80 15.95 18.69
1997 24.69 20.49 22.21
1998 27.37 20.49 23.49
1999 28.65 21.87 25.62
2000 24.32 18.15 20.56
2001 25.90 21.46 24.62
2002 26.11 20.78 24.16
2003 25.13 20.75 23.56
2004 24.98 20.93 23.27
2005 24.99 22.21 23.47
2006 24.60 22.60 23.30
2007 24.56 25.87 25.37
2008 26.02 25.42 25.65
2009 26.36 25.86 26.05
2010 25.13 24.48 24.71
2011 25.95 23.81 25.45
2012 25.78 23.36 24.91
2013 26.14 24.46 25.87
2014 27.72 27.14 28.21
2015 29.69 26.30 28.08
2016 28.52 25.71 26.70
2017 28.60 26.86 27.46
2018 27.73 27.20 27.38
2019 28.68 27.61 27.97
2020 26.73 28.35 27.82
Figure GZ01-2: Trend in shares of damaged trees with defoliation above 25% (index of tree defoliation)
Sources:

Slovenian Forestry Institute 2021 (12. 05. 2021)

Show data
coniferous[%] deciduous[%] total[%]
1991 26.40 9.35 15.57
1993 25.28 12.45 18.87
1994 16.35 13.00 15.69
1995 37.75 17.63 24.71
1996 27.52 12.62 18.94
1997 31.06 20.34 27.03
1998 38.87 21.72 28.81
1999 41.97 22.77 30.62
2000 30.32 16.86 22.28
2001 36.11 24.53 30.41
2002 41.49 24.36 30.85
2003 36.73 23.76 29.27
2004 40.51 23.67 29.27
2005 35.08 28.49 30.59
2006 32.20 27.80 29.40
2007 36.60 35.70 35.70
2008 40.74 34.56 36.90
2009 39.07 32.78 35.42
2010 42.79 23.23 31.72
2011 37.87 27.62 31.40
2012 37.03 23.01 29.04
2013 34.31 28.47 30.87
2014 39.95 34.90 38.29
2015 44.33 32.75 37.81
2016 41.89 31.31 33.81
2017 40.60 35.12 37.03
2018 40.33 33.86 36.08
2019 42.70 35.14 37.69
2020 41.11 36.61 38.07
Figure GZ01-3: Share of trees by individual defoliation class in 2020
Sources:

Slovenian Forestry Institute 2021 (12. 05. 2021)

Show data
defoliation less than 10 %[% of trees] defoliation from 11 to 25 %[% of trees] defoliation more than 25 %[% of trees]
total 18.30 43.70 38
deciduous 15.40 48 36.60
coniferous 24.20 34.70 41.10

Methodology

Date of data source summarization