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REPRODUCING NIGHT-TIME WARMING
AND DROUGHT CONDITIONS
Italian ecologists have developed an innovative methodology for repro-
ducing night-time warming and drought conditions like those forecast to af-
fect Europe over the coming decades. The objective was to understand how
local ecosystems will respond.
As greenhouse concentrations continue to rise in the earth's atmosphere,
the temperature is expected to rise, not only during the day but also at night.
Furthermore, rain is projected to fall less frequently, but more intensely, re-
sulting in periods of drought followed by flash floods.
The question posed by the Vulcan project is how Europe's shrub ecosys-
tems will cope with these changes. In order to answer this question, it was
necessary to reproduce the expected warming and drought artificially in test
plots.
Ecologists developed the methodology applied at the six test sites in
Denmark, Spain, Italy, Hungary, the Netherlands and the United Kingdom.
The experimental set-up was designed for durability with a galvanised steel
frame covered with wave radiation. The HDPE was replaced with a transpar-
ent polyethylene curtain for the drought plots to allow solar radiation
through, but not rain, which was removed via special rain gutters.
Due to the length of the experimental campaign, the extension and re-
traction of the coverings was fully automated. Light sensors ensured that the
HDPE curtains moved into place following sunset and withdrew at sunrise,
acting as a blanket to raise the surface temperature during the night. Simi-
larly, a rain sensor activated the retraction of the covering so that equivalent
soil moisture content was maintained with the control plots. To prevent dam-
age in case of high winds, both the night-time temperature and drought plots
were outfitted with wind sensors that withdrew the curtains when wind
speeds exceed 10 m/sec.
At each of the six test sites, three nighttime and three drought plots, each
covering 20m
2
, were created as well as several control plots. Similar steel
frames were installed on the control plots to eliminate additional sources of
variation. The experimental set-up enabled the Vulcan scientists to investi-
gate the impact a warmer, drier climate may have upon important European
ecosystems.
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