Vol. 72 No: 4

Title:
A Validated Model to Predict the Effects of Environment on the Growth of Lettuce (Lactuca Sativa L.): Implications for Climate Change

Authors:
S. PEARSON, T.R. WHEELER, P. HADLEY and A.E. WHELDON

pp: 503-518

Abstract:
A mechanistic model is described that predicts the effects of changes to the environment on the growth, yield and maturity of lettuce. The model assumes that lettuce has structural and storage carbon pools. The storage pool is supplied by photosynthesis and depleted by respiratory losses and the conversion of assimilate to the structural pool. The model incorporated both instantaneous effects of temperature and CO₂, and long-term effects of thermal time on photosynthetic rate. The rate of structural dry-matter production was related to a simple temperature dependent partitioning coefficient. The model was calibrated on eight separate crops of lettuce and validated with independent data from seven sources. The validated model was then used to simulate changes in head weight and time to maturity with systematic changes in temperature (-2 to +5°C in 1K steps) and carbon dioxide (350 to 700 ppm in 50 ppm steps) superimposed on baseline meteorological data from Rothamsted (1984–1995). These predicted that changes to temperature of up to +3°C would reduce the production time from about 96 to 79 d for April plantings, and from 63 to 52 d for August plantings. Head weight would increase by approximately 32% with an increase in CO₂ of from 350 to 700 ppm, whilst the magnitude of this response varied little with planting date. For any sowing date, increasing temperature was predicted to have little effect on final head weight, however, head weight was predicted to decrease with later transplanting. The potential effects of changes to climate on lettuce production are discussed.

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