Effects of Season and Harvesting Treatments on Soluble-Sugar and Starch Levels in Eucalyptus obliqua and E. globulus subsp. bicostata Roots, and Implications for Armillaria Control

Abstract

Seasonal variations in starch and soluble sugar in root wood of standing trees and stumps of messmate stringybark (Eucalyptus obliqua) and Victorian blue gum (E. globulus subsp. bicostata) were measured for 2 years in four mature stands at Mount Cole, Victoria. Previously established seasonal variations were confirmed for E. obliqua standing trees, and similar patterns were established for E. globulus subsp. bicostata in the first year of the study. E. globulus subsp. bicostata had higher starch reserves but similar sugar reserves to E. obliqua. Selection, shelterwood and clearcutting at the beginning of the second season had no effect on the starch and sugar reserves of retained trees. However, starch levels for stumps declined and appeared to be converted to sugars as the latter were maintained at normal levels, and they continued to show a seasonal variation for at least 12 months after cutting. There is little or no scope for manipulating the food base for Armillaria by varying the harvesting treatment and/or the season of treatment.