Response of self-thinning to artificially reduced levels of leaf areain monocultures of Trifolium pratense

Document Type

Article

Journal/Book Title/Conference

Annals of Botany

Volume

55

Publication Date

1-1-1985

First Page

361

Last Page

366

Abstract

Greenhouse grown monocultures of Trifolium pratense L, were partially defoliated to test the hypothesis that the constant of proportionality (K) in the self-thinning rule is a function of leaf area. This constant equates mean weight (w) and density (p) in self-thinning populations by the equation

w=K·ρ−1.5 (1)

Pruning leaflets did not affect the pattern or occurrence of density-related mortality but, as predicted, did affect K, which was reduced by 25 per cent as leaf area was decreased from an average of 7.3 to 3.9 m2m−2. For both self-thinning and non-self-thinning populations, leaf area was substituted for K in eqn (1) to give

wαLA.ρ−1.5 (2)

Multiple linear regression showed that this expression was significant for all three defoliation treatments. Regressions with tree data grouped by genera were also significant and indicate that eqn (2) may be a more general expression of the relation between mean weight and density in even-aged monocultures. The self-thinning rule may be a special case of eqn (2) which expresses itself when leaf area attains some upper limit.

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