Variations of growth rate of Eucalyptus delegatensis R. T. Baker seedlings at five elevations

Abstract

Eucalyptus delegatensis R.T. Baker, from a single seed source, was grown at five sites over a range of elevations from 260 m to 600 m on two soil types, in the Surrey Hills district of North West Tasmania. Seedlings were harvested twice, after 26 and 74 weeks of growth. Dry weight and leaf area were measured and at the second harvest the net assimilation rate was calculated for each elevation. The seedlings at the five elevations formed three significantly different populations, as discriminated on the basis of dry weight and leaf area. The differences in NAR can best be explained by variation in the length of the growing season, and the severity and duration of frosts over the altitudinal range. The population with the highest NAR (4.16gm sq dm -1 week-I) was grown below 300 m, in an area where Eucalyptus obliqua is the dominant wetsclerophyll forest species. The population with medium NAR (2.03 gm sq dm-1 week-1 ) was grown at three sites between 300 and 600 m, in an area where E. delegatensis wet sclerophyll forest is the -1 major vegetation type. The poor growth of the third population (NAR = 0.72 gm sq dm week - ), grown above 600 m, corresponds to an area in which E. delegatensis grassy woodlands, and Nothofagus cunninghamii rainforest are the predominant vegetation types.