River Oaks and Red Cedar Suppression.
Longlife landholder and Field Naturalist of the Kyogle district Harry Flowers noticed by weekly observations over a forty (40) year period how Camphor Laurel helped kill out whole stands of Casuarina cunninghamia along the banks of the Upper Richmond River, slowly replacing the 'River Oaks' with increasingly more dense Camphor infestations - additionally, all young Red Cedar (Toona ciliata) suffered attrition by the expanding spatial and nutrient competition caused by three factors working together:
1. Underground, extensive (not deep) root competition, Camphor having
an extremely wide/elongated network that also seasonally releases
defensive-allelopathic toxins, and
2. Shading by Camphors, better equipped than most - if not all - native riparian species at growing fast horizontally as well as vertically, to occupy any given space, and
3. Allelopathic leachates and/or toxins (not fully/totally identified) which are exuded or discharged-under-pressure by root bark exudation glands (Kew Botanic Gardens 2000) and that probably include above- ground bark and leaf/stem leachates which, in total, suppress most or much native plant growth, especially of small succulent shrubs, herbs and grasses, within the dripline-extent of most Camphor Laurel tree types.
Dense growth of camphors on riverbanks may cause increased erosion