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Defoliation in
Finnish forests is
not due to pollution
but mostly to aging
of forests,
unfavourable climate
and weather
conditions and
damages caused by
insects and fungi,
says a fresh
research by UN
Economic Commission
for Europe.
Finnish Forest
Research Institute’s
conclusion of the
research says that
Finnish forests are
the healthiest in
the Europe. The
changes in the
degree of
defoliation over
time in Finland also
are minor. During
the last year the
defoliation of pine
has diminished while
defoliation of
spruce and
broadleaves has
increased on mineral
soils.
The results are from
joint monitoring
research under the
ICP Forests research
programme on air
pollution effects on
forests and the
European Union
scheme “Forest Focus”.
The research was
established in the
early 1980s due to
the alarming
scenarios of air
pollution effects
causing catastrophic
forest damage.
In general the
results show that
the condition of
European forests has
deteriorated far
less dramatically
than was feared.
Still, in many
regions various
stress factors,
including air
pollution, affect
forest condition
considerably.
Extreme drought and
heat during the
summer of 2003
contributed to the
pronounced worsening
of the condition of
many of the main
tree species in
2004, notably for
beech and especially
in central Europe.
Only the defoliation
of Scots pine is now
clearly lower than
in the mid 1990s.
Crown condition is
not the only
indicator
Crown condition has
proved to be a
valuable indicator
to estimate the
condition of trees
in a relatively
short time and with
low costs. The
inclusion of a new
litterfall survey
into the monitoring
system is an
additional
opportunity to
evaluate the link
between defoliation
and environmental
stress factors.
Research also
predicts recovery of
soil although full
recovery will take
decades and will
depend on further
emission reductions.
Since 2001 has also
been gathered
reliable ozone data
from remote forested
sites in the Europe.
The threat of higher
ozone concentrations
in lower atmosphere
in repeated warm
summer episodes has
been substantiated.
The assessment of
ozone effects on
plants has just
begun. The very
first results show
that there is no
clear link between
ozone concentrations
and visible ozone
injury. This is
because gas exchange,
and thus ozone
uptake are limited
in dry weather
conditions.
In the future the
ICP Forests research
programme will
provide more
information also on
species diversity in
European forests and
on causes of its
changes over time.
In addition,
harmonized data on
carbon sequestration
will be contributed
by ICP Forests.
By Hannes
Mäntyranta
http://www.forest.fi |
