Effects of site productive capacity and stand density management on the maximum density line for Eucalyptus pilularis (blackbutt)

ABSTRACT

Data were available from two measurements of each stand of a set of stands in native regrowth and plantation forests of Eucalyptus pilularis (blackbutt) in subtropical New South Wales and Queensland. Measurements were made after competition-induced mortality had started in each stand. Most of the regrowth forest had been thinned some time before the measurements. Based on the Reineke model that relates stand stocking density to quadratic mean diameter, a maximum density line was determined for each stand based on methods developed by Vanclay and Sands. It was found that the intercept of the maximum density line increased both with increasing stand site productive capacity and in the thinned regrowth stands. The latter finding does not seem to have been reported for forests before; it is hypothesised to be a result of the delayed redevelopment of inter-tree competitive processes following the major reduction in stand density resulting from thinning. Both effects will have consequences for the structure of density management diagrams commonly used to assist in forest management practice.

KEYWORDS:

• self-thinning
• stand density
• maximum density
• Reineke index
• thinning

Acknowledgements

I am particularly grateful to my colleague, Mr Adrian Goodwin, who derived Equations 3(3) $N=N_1{\left\{1+\left[{\left(r/N_1\right)}^{(2n/s^{{ }^{\ast }})}\right]\left[D^{2n}-{D_1}^{2n}\right]\right\}}^{[s^{{ }^{\ast }}/(2n)]}$(3) and 4(4) $\begin{array}{rl}& \mathrm{l}\mathrm{n}\left(r\right)=\mathrm{l}\mathrm{n}\left(N_1\right)\\ & +\left\{s^{\ast }/\left(2n\right)\right\}\left\{\mathrm{l}\mathrm{n}\left[{\left(N_2/N_1\right)}^{(2n/s^{\ast })}-1\right]-\mathrm{l}\mathrm{n}\left[{D_2}^{2n}-{D_1}^{2n}\right]\right\}\end{array}$(4) as developments of Vanclay and Sands’ work. He also made useful suggestions as to how the analysis of results might be pursued.

Disclosure statement

No potential conflict of interest was reported by the author.