Camphor laurels of various chemotype/s harbour a wide range of scientifically-proven ‘Toxic & Noxious’, ‘Noxious’(Declared categories), and ‘Environmental Weeds’, as well as numerous other weeds in Northeastern New South Wales. The most common weeds found across all-Shires , in order of occurrence are : Lantana, Broad-leaved Privet, and Small-leaved Privet.
Compared to native plants recorded alive-and-growing under Camphor laurel canopies across the same Shires, most weeds are not suppressed beyond their capacity to produce flowers and seed; most native trees and shrubs are in fact perennials, which rarely if ever produce viable seeds within the canopies of most Camphor laurels chemotypes.
In some cases Camphor laurels appear to helps promote the fertility and seeding of weeds-under-Camphor laurels. On the contrary, Camphor laurels do not harbor any native tree species, and in fact suppress the fertility, and seeding of most shrub and tree species growing underneath Camphor’ trees.
Arguably, on some soils, and in some ‘bush regeneration’ areas observed in the course of the Survey, Camphor laurel trees do favour the germination, and regeneration of Foambark trees, Jagera pseudorhus, but this is only one species. On the contrary, two locally (Lismore Shire) ‘Declared’ Noxious weed species, Crofton Weed, and Castor Oil Bush thrive and produce seeds under, and well-within the canopy/ies of mature Camphor laurel trees
In relatively dry, roadside habitats, and ‘disturbed’ roadside environmental conditions some 83 exotic species of known noxious , toxic, and environmental-weed (exotic) species, many of which are also ‘invasive’ or potentially invasive or already declared ‘Noxious’ can be commonly found growing under NSW Northern Rivers’ Camphor laurel trees ; by contrast only 26 native plant species, one Mistletoe and one Moss species are known to be frequently found under or in association with certain types of Camphor laurels commonly growing on roadsides, in parks, reserves, riverbanks, and wasteland(public & private).
Most exotic species found commonly under Camphor laurels are also invasive species, whereas the native plant species able to tolerate the chemistry of Camphor laurels are only ‘common’ in the case of two species; Jagera pseudorhus, and Guioa, in that order of most-common, to ‘sometimes common’.
No native plant species has been observed growing ‘normally’ to maturity under all-types of Camphor laurel.
Observations through the last two major Drought-periods of intense dry-weather encountered over much of the NSW Northern Rivers Region indicate that most, if not all Mistletoe** species are dying-out, or died-out after a period of at least 15-20 years when they did in fact flourish on Camphor laurels (ca.1985-2000) cf. drought-times(2000-02, and 2004 to-date). In some areas, native vine species that were once commonly found (pre-2002) twining on and up small-diameter, young Camphor laurels, have, as photographs confirm died-out, and are no longer living on any young Camphor laurel tree-seedlings in any forest or roadside situation recently inspected by detailed transect/s of the Northeastern Region of New South Wales.
Wattle (Acacia spp.).trees are surprisingly not-so-common under all or any Camphor laurel chemotypes, and in any case they normally die-out after 15-20 years, so providing additional nutrients- being especially rich in nitrogen - to the adjacent Camphor trees, thus ensuring that these trees grow faster, and/or produce bigger fruit-crops!
Acacias are only rarely found germinating underneath Camphor laurel canopies, and the expected lifetime of most if not all native trees competing with Camphor laurels is no doubt foreshortened, due to aggressive surface-root competition. In the case of one native-vine species photographed, Camphor laurel bark growth, to re-cover the twining vine-stem caused the death of the vine (see photoenlargement); no ‘new individuals’ of any one native vine species have not been found growing on any one type of C-laurel tree, during the period of the current Survey(1999-2004).
No native plant species, no mistletoe, and no moss species has been observed living-on the bark or branches of the ‘High Safrole’ type/chemotype of Camphor laurel (otherwise known as a ‘yellow type’ Camphor laurel tree; even grass species, and groundcover weed species are at extremely low frequency levels under these ‘most-toxic chemotypes (= ‘types’) of Camphor laurel, Cinnamomum camphora (L.). The most common species growing in sizeable numbers under the ‘Yellow type’ high-safrole Camphor laurels is Broad-leaved Privet, based on observations and notes taken at over 14 sites in 3 shires.
CONCLUSIONS
For relatively dry roadside area habitats of three Northeastern New South Wales shires, representing a somewhat more-than-average parched, and polluted environment, and a theoretical ‘window’ as to how much of the region might appear in a future, globally-warmed atmosphere there are clear indications that Camphor laurels of most, if not all, chemotypes commonly found growing across the entire region harbor a broad range of equally ‘noxious’, and invasive-environmental weeds, some 83 species in-all, of which a dozen (12) are also toxic plant species.
Camphor laurels therefore appear to increasingly harbor toxic species, which in-turn also appear to be more capable species, of, for instance withstanding pollutants commonly deposited on roadsides, and/or a locally warmed and windy/-ier than average environmental conditions.
AUTHOR
J. A. Friend
Camphor Laurel Research Centre – Lismore
12 July 2004