The Response of Bavarian Mountain Forests to Climate Change

As the exposed forefront of the Calcareous Alps, the Bavarian Alps exhibit a
moderate lapse rate of 0,48°C/100 m elevation and annual preciptation of
1000-3000 mm. The region hosts the world’s oldest mountain forest
meteorologial station at Peissenberg, where a warming of 2,38°C has been
measured since 1850, while precipitaion remained unchanged.
Forest productivity, as measured by site index of the main tree species
Picea abies, declines with elevation, but is even more strongly constrained
by the prevalence of nutrient deficiences on shallow calcareous soils. Radial
growth of the same tree species shows a complex correlation with
temperature and precipitation: Warm and dry years limit growth up to an
elevation of ca. 1000 m, while they boost radial growth above that line.
Thus, high elevation forests are expected to respond to climate change with
increased growth, while lower elevation forests may suffer from heat and
drought periods.
Upper limits of many plant species had been recorded at the end of the
Little Ice Age by Otto Sendtner (1854). Resurveys by alpine biotope mapping
and a citizen science project demonstrate that forest understorey and tree
species have extended their upper limits, but are lagging behind the
warming trend and are constrained by lack of soil development and alpine
pasturing above the treeline.
Long-term monitoring of forest soils has revealed substantial losses of
organic floors during the last decades even under closed forest, which is
likely triggered by warming.
Under the scenario of continued high CO2-emissions (RCP 8.5), warming by
another 3-4°C must be expected until 2100, which would shift elevational
belts by another 600-800 m and render lower and middle elevations
unsuitable for Picea abies. Adaptation of forests is faced with goal conflicts
between salvage logging of bark beetle- (Yps typographus) infested spruces
and proactive management of dead wood and humus as as between
between the maintenance of open habitats and protection against natural
hazards and carbon storage.