Masters Degrees (Soil, Crop and Climate Sciences)
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Browsing Masters Degrees (Soil, Crop and Climate Sciences) by Subject "Adaptation strategies"
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Item Open Access Impacts of climate change on accumulated chill units at selected fruit production sites in South Africa(University of the Free State, 2014-12) Tharaga, Phumudzo Charles; Steyn, A. S.; Coetzer, G. M.English: Climate is an important aspect of crop production, determining the suitability of a given region to deciduous fruit production and largely controls the yield and quality thereof. Climate has always been variable, but there is strong evidence of global and regional-scale climate change since the advent of the industrial era. In South Africa mean surface temperatures have revealed an increasing trend over the last century. South Africa is renowned for its quality export fruit, but deciduous fruit production is already marginal under current conditions. Problems related to climate change will add strain to fruit growers and impact directly on livelihoods within the main production regions. It takes a considerable time to establish fruit orchards, thus it is even more important for these producers to take climate change in consideration. Since deciduous fruits require winter chilling to break dormancy, the main objective of this study was to determine the effect of climate change on accumulated chill units at three sites in South Africa, namely Bethlehem, Ceres and Upington. Observed winter temperature data were obtained for the base period 1981 – 2010, while projected temperatures up to 2100 were acquired from a Global Climate Model (GCM). Hourly temperatures were derived from these daily minimum and maximum temperatures by means of a Temporal Downscaling Model. The Utah Model and the Daily Positive Utah Chill Unit Model were used to quantify winter chill, accumulated over each winter season from 1981 – 2100. Cumulative distribution functions were used to identify shifts in industry related thresholds for accumulated positive chill units (PCUs). The results indicated that the impacts of climate change vary among regions. Historical accumulated PCUs showed no significant trend for Bethlehem, but a decreasing trend for both Ceres and Upington. The GCM projections indicated a continuation of these trends over the course of the 21st century, thus resulting in an increase in deficient winter chill problems in Ceres and Upington in future. Potential adaptations involve cultivar and/or rootstock selection, microclimate manipulation and the use of chemical rest-breaking agents.