Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

GAP - plant response, climatic stress (controlled experiments)

The present study is pioneering in terms of its complex approach to investigating intra- and inter-specific competition in beech and ash seedling growth in response to climate change in simulated regenerating natural forest gaps. Simulations were performed by temperature-regulated closed-top-chambers. Eight chambers were used in a factorial design with replicate treatments of [CO2] x temperature x light flux x competition design. [CO2] was ambient levels or + 360 ìgmol mol-1. Temperature was ambient levels or + 2.8 degrees Celsius. Light flux at the top of canopies was 25% or 8% of outdoor levels 1.75m above the ground (i.e. at the outdoor plot). Relative to more realistic open-field measurements (8 m above the ground) the two chamber light flux levels were 16% and 5%.

There were clearly visible effects by the light and carbon dioxide treatments, and an obvious interaction between temperature and carbon dioxide. The studied climate treatments and competition designs suggested that the predicted climate change during this century of 2-3 degrees Celsius warmer air and a doubling of atmospheric carbon dioxide concentration will improve the competitive capacity of ash seedlings relative to beech seedlings in the regeneration of natural mixed beech-ash forests in Europe.

It was demonstrated that an increase in temperature was the most important component in helping ash compete better with beech with a concomitant rise of [CO2] and temperature. Beech on the other hand responded more to light flux than ash. Some climate change scenarios induced ash seedlings to grow taller than beech seedlings, and at the same time attain a larger leaf area, and a larger total biomass. The advantages for ash were found particularly in the darker regions.

As judged from the present study, the most likely scenario for the future climate in Europe will improve ash regeneration below an old canopy relative to beech regeneration, where it will sometimes even surpass beech, so that when a gap is formed, and the time for definitive competition to dominate the mature mixed forest arrives, a shift from beech towards ash is likely.

With the existing scenarios for global climate change during this century it is of vast importance to know how these changes may affect forestry. The present study indicates that interaction between climate variables and competition can move the advantage from one major forest species to another. This should be valuable information to the forest manager. The next step, however, would be to include soil water, nutrition and more than one year of exposure and competition in future studies.

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Jens EMBORG, (Associate professor)
Tel.: +45-352-81744
Fax: +45-352-81508
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