Proximity signal and shade avoidance differences between early and late successional trees
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Date
14/06/2001Author
Gilbert, Ian R
Jarvis, Paul G
Smith, Harry
Metadata
Abstract
Competitive interactions between plants determine the success of
individuals and species. In developing forests, competition for
light is the predominant factor. Shade tolerators acclimate photosynthetically
to low light1±3 and are capable of long-term survival
under the shade cast by others, whereas shade avoiders rapidly
dominate gaps but are overtaken in due course by shade-tolerant,
later successional species. Shade avoidance4±6 results from the
phytochrome-mediated perception of far-red radiation (700±
800 nm) scattered from the leaves of neighbours, provides early
warning of shading7, and induces developmental responses that,
when successful, result in the overgrowth of those neighbours8.
Shade tolerators cast a deep shade, whereas less-tolerant species
cast light shade9, and saplings tend to have high survivorship in
shade cast by conspecific adults, but high rates of mortality when
shaded by more-tolerant species9. Here we report a parallel
relationship in which the shade-avoidance responses of three
tree species are inversely proportional to proximity signals generated
by those species. On this basis, early successional species
generate small proximity signals but react strongly to them,
whereas late successional species react weakly but generate
strong signals.