Effects of thinning and initial stocking on growth of Eucalyptus camaldulensis.  W. D. Incoll.  September 1981.  17 pp. (unpubl.)

SUMMARY

Thinning trials were established in Eucalyptus camaldulensis Dehnh. (river red gum) stands, each more than 20 years of age, in the Barmah Forest, northern Victoria, in 1957 (Black Swamp) and 1964 (War Plain), and in New South Wales, in the Murrumbidgee Irrigation Area, in 1961. Recent remeasurement of these trials suggested that net basal area growth was greatest (about 1.2 m² ha^-1 yr^-1) in moderately thinned (to a nominal 13.3 m² ha^-1) stands, whereas diameter growth of the 123 largest diameter trees per hectare was greatest (about 0.9 cm yr^-1) in the most heavily thinned (to a nominal 7.6 m² ha^-1) stands. Basal area and diameter growth seemed to increase with increased flood frequency, though there were insufficient data to test this conclusion statistically.

Measurements of mean tree diameter were made in a 20-year-old unthinned stand at Bucks Lake, Barmah Forest, which had previously been measured at 10 years of age. Measurements indicated that mean diameter (all stems) at 20 years of age ranged from 12 cm in stands of 5000 stems per hectare (basal area 56.5 m² ha^-1) to about 26 cm in stands of 200 stems per hectare (10.6 m² ha^-1). Variation in branch retention and incidence of stem bends with initial density were not measured, though observations suggest that both were more frequent at initial densities of less than 500 stems ha^-1. Thinning options for river red gum stands more than 20 years old are discussed and a spacing formula derived to assist in operational thinning of these stands.