Len Webb Ecological Images Collection

Image No. 9-49

Field Experiments The Silky Oak plantation does not exclude natural regeneration, shown here, of any rainforest species except itself Grimstone Plantation, Yarraman district, Queensland 1965 Larger image (167K)

Routine forestry tending of successful plantations removes regeneration because of root competition. Thus the "checked" Silky Oak plantations were not tended for some time, as in this slide. Underplantings of other commercial timber species such as Red Cedar, Hoop Pine were tried later. In healthy Hoop Pine plantations which are tended regularly, there are nevertheless natural regenerated Silky Oak seedlings, e.g. close to and behind trees, which escape "brushing" (by brush hooks used by the forestry gang). Their successful growth was later confirmed experimentally on a larger scale under Hoop Pine.
Silky Oak Plantation ca. 30 years old at Grimstone. Poor growth of trees is evident, although more vigorous and taller (e.g. in foreground) along boundaries, where roots can reach out into soils not affected by Silky Oak trees. This phenomenon of poor growth some time after planting is known in forestry as "checking" (of a plantation). Note common natural regeneration (seeded from nearby intact rainforest), termed "green fire-breaks" around each compartment) of many rainforest species, EXCEPT Silky Oak itself! This observation, confirmed by numerous surveys of similar situations afterwards, triggered this experimental research. It is of particular significance that Silky Oak natural regeneration occurs freely under adjacent Hoop Pine plantations, i.e. in precisely the same physical habitat, except for the presence of Silky Oak trees.

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