Marcus Schaub

Pfynwald

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The study area (1.23 ha) is located in the dry, inner-alpine Rhone Valley, close to the distribution edge of Scots pine. The natural Scots pine stand was divided into eight plots of 25 x 40 m (1000 m 2) each with 5 m buffer areas between and around the plots. The plots were aligned side by side along a channel of the Rhone river to facilitate irrigation, from where water was taken to irrigate four randomly selected plots (irrigation). Four untreated plots served as controls. The Scots pine trees in the study area were numbered consecutively from 1 to 1123 before the treatment started. In spring 2003, before the treatment started, the stem diameters were recorded at breast height and their crown transparencies visually rated from 0% to 100% in 5% steps based on reference photographs (Müller and Stierlin 1990). A crown transparency of 0% refers to a fully foliated crown and a crown transparency of 100% refers to a crown without any needles. In the following years, the crown transparency of all the Scot pine trees was rated on every March before the vegetation period by the same observers without reference to the previous ratings. Irrigation was started for the first time in spring 2003. Water was pumped from the nearby river channel and distributed by 80 sprinklers set at a height of 110 cm in the four treatment plots. The sprinklers were placed along four parallel tubes per plot with five sprinklers per tube and a sprinkling radius of 7 m per sprinkler. The treatment plots were irrigated during the vegetation period on nights when there was no precipitation. The amount of irrigated water applied corresponded to about 700 mm per year. Since 2003, approx. 100 parameters are being monitored and measured, including intensive field campaigns addressing specific, scientific questions. (Source: Brunner et al. 2009. Tree Physiology. doi: 10.1093/treephys/tpn046)

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