Daily Radial Growth of Oak in Relation to Maximum and Minimum Temperature

1. The relations between daily radial growth and maximum and minimum temperature of the day of growth measurement, 1 day before growth measurement, and 2 days before growth measurement were studied during the 1960 growing season for northern pin oak (Quercus ellipsoidalis Hill) growing on Plain-field sand in central Wisconsin. Correlation coefficients were obtained between growth and maximum and minimum temperature for (a) a 98-day period from June 8 to September 13; (b) a 70-day period from June 8 to August 16; (c) seven 2-week periods from June 8 to September 13; and, (d) four 3-week periods from June 8 to August 30. 2. Daily radial increment was significantly correlated with maximum and minimum temperature. The closeness of correlation varied during the growing season, with a general tendency to decline in the latter part. Earlier in the season, based on 3-week analyses, a closer relationship was indicated between growth and minimum temperature than between growth and maximum temperature. In late summer correlations between growth and temperature were not significant. 3. Correlations generally were better between growth and temperature of the day of growth measurement than between growth and temperature of the day before growth measurement. The possibility of a 1-day lag effect of temperature on growth was indicated, however, as was the absence of a 2-day effect. Possible physiological implications of the lag effect of temperature on growth are discussed. 4. Marked response of trees to even small amounts of intermittent precipitation during the growing season complicates evaluation of temperature-growth relations. Radial increase following a rain consists of a cambial growth component and increase resulting from stem rehydration. The hydration component often is greater than cambial growth.