Within the next 50 years drastic climate changes are expected to take place, according to international climate experts.

The Green house effect is the main clue due to an increase in the combustion of fossil fuels and a subsequent rise in green house gases in the atmosphere, especially carbon-dioxide which is expected to double!

"But don't trees and other plants flourish on more carbon-dioxide which is the basis of photosynthesis together with water?"

Generally speaking yes - If carbon-dioxide was the limiting factor. But mostly other nutrients or water availability will limit growth.

What will happen to the tree species of today in another climate?
To what extent will an increase in forest area and forest production sequester carbon dioxide into the trunks and the crown and consequently reduce the green house effect?

Can changes in forestry prevent the mineralizing of carbon- and nitrogen sources in the soil, and prevent further emission of green house gases? 
Can forests prevent the negative effects of draught, and what ground water level will there be in the forests over the next fifty years?

Ecological effect

An increase in carbon-dioxide will lead to an increased growth of trees, i.e. in nutrient rich soils. An increase in temperature will lead to an increase in the decomposing of organic substances and thus to an increase in the release of nutrients which will in turn lead to further growth. When organic matter is then decomposed not only nutrients but also carbon-dioxide will be released which will be used for further photosynthesis - a feed back balanced system.

With increased average temperatures the growth season will be longer; not necessarily leading to an increased production since the respiratory rate of the trees will increase in parallel with the temperature increase. The complex balance of carbon-dioxide exchange rates between atmosphere and trees is being investigated in Denmark by Risoe National Laboratory. These investigations are part of similar studies in other European forests.

To-day we only have restricted knowledge about the influence of climate change on ecological processes, but a drier climate will definitely reduce both decomposition and growth rates. Increased evaporation due to increased temperatures will eventually lead to a drier climate, but it is uncertain whether or not precipitation will in- or decrease.

Meteorological station measuring green house gases, C02 and N20, to and from the forest

Ultraviolet rays

The trees have to stand an increase in ultraviolet light caused by a
reduction in stratospheric ozone. Some plants are more sensitive to ultraviolet
light than others, and some species react by producing pigments and other
metabolites. Southern species are therefore expected to oust species normally
found in Denmark today, southern species will spread further north, and
regionally to higher altitudes. The timber line will go up, and some alpine
trees and scrubs will eventually disappear.

Conifers in northern Europe will move further north, and deciduous trees like
oak, Quercus sp., and beech, Fagus silvatica, will flourish.

But the spruce, Picea abies, will get into difficulties, and it is still the
economically most important species in DK.

How quickly can the forest sector and the wood industry adjust to deciduous
trees or other species of conifers when one considerrotation time?

Adjustment in the agricultural sector will not suffer the same problems when
the rotation time is short.

'Climex'

= Climate Change Experiments are carried out in giant green houses in Grimstad, Norway.

The experimental enclosure at Risdalsheis, southern Norway, covers a whole forested catchment ecosystem

1200 square meters of mountain forest have been covered, the tempearture have
been increased five degrees C and the carbon-dioxide level is doubled. In
another green house heating cables have been placed at the forest floor.

Soil chemistry, plant physiology, botany and zoology are being investigated
as well as contents of nutrients in tree trunks, leaves and needles.

Results from the first two years show that assimilation and turnover rate of
organic substance has increased. But at the same time nutrients are getting
less available . So, the turnover rate decrease or will it stabilize at the
increased level?

The next step is to follow if nitrogen will be mineralised, accumulated or
washed out of the ecosystem.

The results will be used for model calculations and predictions enabling
forestry to adapt to future effects og climate changes, and for predicting the
benefit of reducing the emissions of carbon-dioxide.

The experimental enclosure at Risdalsheis, southern Norway, covers a whole
forested catchment ecosystem.