The effect of temperature and day length on the height growth of Birch (Betula pubescens) at 1900 feet in the northern Pennines.
There are clear indications that Birch grows in height only when the mean air and soil temperatures exceed 42-44°F. There is a rather loose correlation between the rate of height growth and mean daily accumulated air temperature (m.d.a.a.t.) above 42°F. Mean daily maximum air temperature (m.d.m.a.t.) appears to be more critical for growth than mean daily minimum. There are three consecutive phases of growth during the season. During the initial phase, m.d.m.a.t. appears to be the most important factor. The apparent effect of mean daily accumulated soil temperature is probably a consequence of the correlation between this variate and m.d.a.a.t. The difference between mean daily air and soil temperatures appears to be the most important factor influencing growth during the middle phase. During the final phase, the values of all the factors under consideration are decreasing, so that the relations may be complex, but day-length seems to be the principal factor that stops growth. Throughout the season, day-length affects the difference between mean daily air and soil temperatures, and it may thus influence growth indirectly during the middle phase. From author's summary. KEYWORDS: Atmospheric relations and acclimatization \ Betula pubescens see also \ B. alba \ increment \ Betula pubescens see also \ B. alba \ light relations \ Betula pubescens see also \ B. alba \ microclimate \ plant ecology \ Growth climatic factors \ Photoperiod \ effects \ height growth \ Photoperiod int