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Title: The effects of climate warming on winter wheat development
Author: Butterfield, Ruth
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 1996
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A model of winter wheat (Triticum aestivum L.) development (Weir et al., 1984) has been used along with field experiments to test the hypothesis that small amounts of warming, that may occur as a result of greenhouse gas-induced climate change, will cause marked reductions and affect the year-to-year variability in winter wheat developmental phase durations. The model has been run using long series historic climatic data from two sites in the UK, with systematic year round additions to the historic baseline and with seasonally varying changes to historic temperature. Changes from the present temperature predicted by GCMs for the future years of 2010, 2030 and 2050 have also been added to the historic data and the sensitivity of modelled development has been assessed. The sensitivity of the model output to different sowing dates and to different vernalization models have also been assessed. Field experiments were conducted on winter wheat over two growing seasons to assess the sensitivity of developmental phases to elevated temperatures produced by growing the wheat under synthetic covers. Differences in the early development of three varieties on two sowing dates was studied in the first season. A further study on the phenological development of cultivar Avalon, again using two sowing dates, was conducted in the second year. Model mean and year-to-year variability in duration from sowing to maturity were significantly reduced by arbitrary warming and increases in temperature expected from climate change scenarios. Model results indicated that a northern UK site (Edinburgh) is more sensitive to increases in temperature than a southern UK site (Oxford), due, in part, to the temperatures experienced over winter being closer to the base temperature for development. Model tests also revealed that the shape of the vernalization effectiveness curve has dramatic effects on the duration from sowing to double ridges which implies the need for correct vernalization model parameterization for different cultivars. The field experiments highlighted the differences between the vernalization responses of three UK varieties of winter wheat and also showed that warming produced in field conditions can have dramatic effects on shortening of the growing season, causing inevitable shortening of . the grain filling period. Testing the model, using temperature data and observations of developmental phases from the field experiment, indicated that the model predicted the duration to early phases of development (up to double ridges) more successfully than later phases. Anthesis was predicted too late causing maturity also to be predicted late in all situations. Durations to stages were predicted less well at later sowings rather than earlier sowings and_ in warming conditions rather than in controls. Manipulation of model thresholds, of thermal, photo-thermal and photo-vernal-thermal time for each developmental phase, to fit the observations in the uncovered treatments and then application of the altered model to the covered treatments resulted in a considerable improvement in the model's ability to predict phase durations under warmer conditions. The implications of the shortened winter wheat growing season length, due to climatic warming, on crop yields is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available