White cypress pine in N.S.W.: growth patterns and optimal thinning regimes for 60 to 80 year old stands

Abstract

Summary The growth of 60-year-old white cypress pine stands at five locations in the Pilliga Management Area of N.S.W. is analysed over a 20 year period following thinning. The growth pattern and the optimum thinning range differed from that previously reported for this species. At four of the five locations stand basal area increment was independent of basal area for a range of values forming a ‘plateau’ of maximum increment. For these sites, no stand basal area increment rise or decline was detected with increasing residual basal area, over the range 6 to 18 m2 ha−1. The other location exhibited a growth pattern akin to the phenomenon of “lock-up” where increment did not “plateau” but peaked at a basal area of about 8 m2 ha−1 and then declined markedly at higher basal area without corresponding mortality. The optimum thinning range, where both tree size and site utilisation are maximised, was determined to be within the range 6 to 10 m2 ha−1. Maximum basal area increment ranged from 0.30 to 0.40 m2 ha−1...