Density effect and self-thinning in Eucalyptus urophylla stands

Abstract

Density effects on the growth and self-thinning of Eucalyptus urophylla stands were examined for 7 years. The reciprocal equation of the competition-density (C–D) effect was used to describe the C–D effect in even-aged pure stands of E. urophylla during course of self-thinning and showed a good fit to the data. The time trajectories of mean stem volume-density nearly paralleled the y-axis during early growth stages of stands, and then began to curve left. Finally, the mean stem volume-density trajectories of the low-, middle- and high-density stands tended to follow the self-thinning lines with slopes of − 2.01, − 1.90 and − 1.99, respectively. With increasing physical time t, the biological time τ increased rapidly during early growth stages and became slow gradually during later growth stages. Realized density-initial density curves tended to become more or less flat with increasing initial density, indicating the existence of an asymptotic value for density at a given time. The coefficient ε, the reciprocal of which represents the asymptotic density at a given time, increased with increasing biological time τ, indicating that the asymptotic density decreased with increasing stand age. Final yield Y(t) increased gradually with increasing stand age.