Continuous measurements of radial variation in Eucalyptus pauciflora Sieb. ex Spreng

Abstract

Improvised dendrographs of the Fritts type were used to make continuous chart records of radial variation in trees of Eucalyptus pauciflora at two altitudinal sites where, in addition, concurrent observations were made of some environmental variables. The total period of observation was 186 days, which was presumed to cover the main growing season.

Continuous data were digitized by means of a stripchart converter and the converted data used to replot curves and to extract daily values of variables.

Broadly sigmoid seasonal growth curves were found to be modified by a period of reduced growth in the hottest part of summer, by irregular fluctuations apparently related to precipitation, and by regular diurnal fluctuations.

Unreversed increases in radius immediately following some falls of rain suggested that rapid cell growth occurred at times of high tissue hydration.

An attempt to find a general explanation of daily radial variation in terms of certain environmental variables by means of multiple regression techniques was not successful. The results reflected to some extent the effects of precipitation referred to above, but the order of importance of significant variables was inconsistent between trees and between altitudes.