Ley production potential as affected by climate change at high latitudes

摘要

Examples of climate change throughout the century were quantified using HadGEM2-ES-RCP45 scenarios (2070 - 2099) as compared with baseline data (1981 - 2010) for three sites, Rygge (59.4°N), Vajrnes (63.5°N) and Tromso (69.7°N). The daily mean temperature for May through August was estimated to increase by 2.2 - 2.7 °C, while the length of the mean growing season (5 to 5 °C) increased some 28, 33 and 40 days, respectively, for the sites. Changes in total precipitation and its distribution through the year were relatively small. Potential evapotranspiration increased slightly. Forage DM yield was estimated from climatic, soil and management factors by the updated COUP-ENGNORley crop model; accounting for the benefit of long photoperiods, and calibrated against field trials with continuous growth curves obtained from weekly sampling of timothy ley yield during ten weeks at As (59.7°N) and Tromso. The extended growth period allows an increase from three to occasionally four seasonal cuts in southern Norway and from two or one cut to three or two cuts when moving northwards. Drought periods, frequently occurring during midsummer in south eastern Norway will counteract the yield increase.