Climate change scenarios predict simultaneously
increase in temperature, altered precipitation patterns
and elevated atmospheric CO2 concentration,
which will affect key ecosystem processes and plant
growth and species interactions. In a large-scale
experiment, we investigated the effects of in situ
exposure to elevated atmospheric CO2 concentration,
increased temperature and prolonged drought
periods on the plant biomass in a dry heathland
(Brandbjerg, Denmark). Results after 3 years
showed that drought reduced the growth of the
two dominant species Deschampsia flexuosa and Calluna
vulgaris. However, both species recovered
quickly after rewetting and the drought had no
significant effect on annual aboveground biomass
production. We did not observe any effects of increased
temperature. Elevated CO2 stimulated the
biomass production for D. flexuosa in one out of
three years but did not influence the standing
biomass for either D. flexuosa or the ecosystem as
more litter was produced. Treatment combinations
showed little interactions on the measured
parameters and in particular elevated CO2 did not
counterbalance the drought effect on plant growth,
as we had anticipated. The plant community did
not show any significant responses to the imposed
climate changes and we conclude that the two
heathland species, on a short time scale, will be
relatively resistant to the changes in climatic conditions.