THE COMPETITION-DENSITY EFFECT IN POPULUS × EURAMERICANA CV.`SAN MARTION' PLANTATIONS

Xue Li(College of Forestry, South China Agricultural University Guangzhou510642) Akio Hagihara(Laboratory of Ecology and Systematics, Faculty of Science, University of the Ryukyus\ Okinawa 903-0213 Japan)

The C\|D effect, Reciprocal equation, Populus × euramericana cv.`San Martion'

The reciprocal equation of the C\|D effect, i.e. 1/ w = Aρ i+B ( w and ρ i respectively represent mean stem volume and density, A and B are coefficients) was used to describe the C\|D effect in Populus × euramericana (Dode) Guinier cv. `San Martion' plantations. The data observed from different growth stages were well fitted with the C\|D curve given by the reciprocal equation of the C\|D effect on logarithmic coordinates, and the C\|D curve shifted upward with the progress of time. The change trends of biological time τ, the coefficient A and B , the coefficient of growth λ(t) and the final yield Y(t) were given. The biological meanings of coefficient A and B were obtained. Biological time τ increased gradually with physical time t . With increasing τ , the coefficient A increased abruptly up to its maximum value, and then decreased gradually, whereas the coefficient B decreased exponentially and tended to close to zero. With stand growth the coefficient of growth λ(t) decreased gradually and final yield Y(t) increased gradually. Based on the C\|D effect, intermediate cutting for 7 year old P. euramericana plantation with high density was proposed.