The Effect of Temperature and Day Length on the Height Growth of Birch (Betula pubescens) at 1900 Feet in the Northern Pennines

Abstract

The object of the work was to investigate the relationship between the growth of birch, and the air and soil temperatures and day length at different times of the growing season. According to Kienholz (1941), who worked on North American species of birch, increasing temperature largely determines the time at which growth starts in the spring. Mandy & Karpati (1958) found that cuttings of Betula verrucosa in the laboratory flushed under different combinations of time and temperature which corresponded with data on phenology found in the literature. Wang & Perry (1958) showed that photoperiod controlled the continuation of shoot elongation of B. papyrifera and B. lutea and the onset of dormancy as shown by the formation of terminal buds. They found no indication that the time when growth began was influenced by photoperiod after the plants had been subjected to winter chilling at 38-40? F. Wareing (1963, personal communication) found that a day length greater than 12 h was necessary to maintain the growth of Birch in a glass-house during the winter. The influence of soil temperature on height growth has been investigated mainly in relation to conifers but not to the same extent as the effect of air temperature, probably because of the difficulty of co-ordinating air and soil temperatures. Hiley & Cunliffe (1922, 1923) concluded that air temperature is the dominant factor in determining the daily fluctuations in growth, but some of their results also indicated that a high soil temperature is detrimental to stem development. Baldwin's studies (1931) suggested that air temperature was the chief determinant of the course of growth and that little growth took place until mean weekly air and soil temperature reached 50? F. Farnsworth (1955) did not present soil temperature data 'because they are not as closely related to elongation as air temperature' and Huikari (1958) concluded that height growth is not directly correlated with the temperature of the soil during growth. All of these authors worked on conifers although Huikari, working in Finland, included birch in his investigations.