Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Night time warming experimental methodology

Warming treatment. The warming treatment was applied to 3 study plots of 20 m2 (5*4 meter) at each site. The warming plots were covered by a light scaffolding carrying a curtain reflecting the infrared radiation. The scaffolding was a frame of galvanised steel tubes covered by a polyethylene plastic tube to avoid leaching of contaminants from the frame into the plots. The curtain material consisted of 5mm wide aluminium strips knitted into a high density polyethylene (HDPE) mesh (ILS ALU, AB Ludvig Svensson, Kinna, Sweden). The curtains reflected 97% of the direct and 96% of the diffuse radiation and allowed transfer of water vapour. The curtains were coiled on a beam and connected to a motor.

The motor was activated automatically by an electronic controller according to the following preset climatic conditions during the whole year:
- Light intensity at sunset (light intensity < 0.4W m-2) the curtains were automatically drawn over the vegetation to reduce the loss of IR radiation. At sunrise the curtains were retracted to leave the plots open during the day.

- Rain in order to keep the hydrological conditions in the plots unaffected a tipping bucket rain sensor activated the removal of the curtains in case of rain during the night (sensitivity <0.3 mm). When the rain stopped the curtains were automatically drawn over the vegetation again.

- Wind to avoid damage to the curtains, a wind sensor activated the removal of the curtains when wind speeds exceeded 10m s-1 during the night. When the wind speed dropped below 10 m s-1 the curtains were automatically drawn over the vegetation again.

The curtains were operated sequentially causing a delay time of c. 4 minutes from the first to the last curtain in the sequence. The height of the curtains matched the height of the vegetation at each site and was 0.6-1.0 meter above the soil surface. The study plots were open at all sides. All curtains were operated on 24V DC supplied by main power (Clocaenog, UK) or by solar panels (Mols, DK; Oldebroek, NL; Garraf, SP;). At Garraf and Oldebroek the warming treatments were stopped once or twice for 2-4 weeks during the dormant season for calibration of temperature sensors.

Drought treatment. The drought treatment was applied to 3 study plots of 20m2 at each site for extended periods in the growing season. The drought plots were constructed similar to the warming treatments except that the curtain material was a transparent polyethylene (PE) plastic. The curtains were controlled by a rain sensor activating the curtains to cover the plots whenever it rained and remove the curtains when the rain stopped. The water collected by the curtains was removed from the area by gutters. The curtains were removed automatically if the wind speed exceeded 10m s-1. Beyond the time of the drought treatment the drought plots were run parallel to the control plots.

Control. Parallel to the warming and drought treatments 3 untreated control plots were operated for comparison. The control plots were covered by a similar light scaffolding as for the warming and drought treatments, but with no curtain.

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Reported by

DISAFRI - University of Tuscia
Via S. Camillo de Lellis, snc
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