Temperature as a determinant of plant productivity.

Quite small variations in temperature such as those that exist between the north and south of Britain, or on a local scale between north and south aspects of a hill, may cause large variations in plant productivity. An attempt is made to assess the effect of a 1 degree C increase in the mean temperature of the growing season by using published data from various sources. The conclusion reached is that a 1 degree C increase in a north temperate climate may be expected to increase plant productivity by about 10%, providing that other factors like water or nutrients do not become limiting. But, for annual crops, a negative effect of temperature has sometimes been observed. This may be because temperature speeds up the development of the crop and thus reduces the duration of photosynthesis. In the natural environment variations in solar radiation and wind speed may often exert an effect on growth because they influence the energy balance, altering the temperature of meristems and other plant tissues in subtle ways which have a significant impact on the pattern of carbon utilization. A more precise understanding of the relationship between growth and weather variables is unlikely to be achieved unless models are developed which enable integration of component processes of growth with what is known about the spatial and temporal variation in the weather variables.