A profoundly simple key has been. developed to aid in the identification, and pre-elimination or bush regeneration 'marking' of both the 'more toxic' and 'most/extremely toxic' chemotypes of Camphor Laurel trees, both in planted park situations, and in 'wild' , weed-infested roadside and. Crown land areas.
This Key has a priority Aim of ensuring that World Heritage rainforest reserves do not become invaded by seed-spread of the more, and most-toxic types of Camphor Laurel trees; the Key can be a useful management tool, as well as aid scientists and the community in gaining a better understanding of this genetically diverse northern hemisphere species (Family: Lauraceae).
Excellent quality Camphor trees have been cut for wood, laminated or slabbed, and, sold domestically or for export from NSW's Northern. Rivers Region for at least the past 60 years. The species was spread throughout the region by farmers, schools, and various NSW Government agencies for 60 or more years before that. intra-species hybridisation occurred as a result of the specific importation of a Japanese type-tree (ex-Hiroshima 1880) via Sydney's Royal Botanic Gardens - it was sent to Burringbar on NSW's North Coast in 1881.
Today, Camphor Laurel has become the dominant forest and farm species over most districts of NSW's North Coast Region, whether the calculation is based on individual tree numbers per species, or the area of land. covered by each dominant species. In fact, one chemotype of Camphor has adapted to estuarine, and marine areas in NSW and Southeast Queensland (Friend 2001), so that land. and water areas must he added in any satellite imagery determination of this species' spread.
Not only do Camphor Laurel trees extract large volumes of water all-year-round, they have on some rivers, eg Orara River Northwest: of Coffs Harbour, been let go to become the single, dominant species, completely overtaking most other life in and near the stream/s. A wide range of wildlife is known to be impacted upon (Bishop 1993; Fuller and McClintock 1982, Camphor Research Centre 2000, and Friend 2002), especially by the most toxic types/ chemotypes of the Camphor trees.
There can be little doubt now that Camphor Laurel infestations, and their spread, especially by the more aggressive/dominant bird species that are capable of vomiting-up Camphor seeds, is currently the greatest environmental problem of the North Coast of New South Wales; anything to help identify which trees are causing the most damage to wildlife should be helpful.
At flowering of the Camphor trees, from 1st September 2002, through to the average-time of fruit-set, (circa 5th November 2002), some 50 randomly chosen Camphors were sub-sampled by breaking off multiple branchlets measuring approx. 1 cm diameter at their thickest ; a sub-sample of three branchlets was broken-off for dry-pressing with record-of-origin, and cross-referencing to the numbered, marked primary sample. All inflorescences were then counted, and summated for each spike-rachis, as well as for each flower-cluster of each branchlet. All branchlet inflorescence samples were assessed 'fresh' on the same day of sampling.
Records on all specimens and Record Sheets include date of sampling, actual location of tree, branchlet and petiole bark colour , colour variation and/or distinctive markings, leaf venation, and domatia number and colour, leaf shape and size/variability, leaf blistering, origin of spikes in relation to top-leaves and lowest remaining leaves of branchlet, floret compactness/density on spike, sepal size or absence, rachis-spike length, distinctive flower colour, and, most especially, total number of florets per spike, - using a hand-lens to ensure that fallen/windblown florets could still be accurately estimated by the size and number of abcission zones on each spike).
Tree sampling was conducted, around four geographically dispersed centres, representing at least four soil types, hilly locations, slopes, and. floodplain trees in a rough circle around the Mt.Whian Whian and 'World Heritage' rainforest reserve forests between Lismore, Mullumbimby, Uki, Nimbin and The Channon, and in two neighbouring river catchments (Richmond and Tweed Rivers).
A total of 62 Camphor trees were assessed in the year 2002. Branchlet and leaf sub-sampling was conducted in Lismore, of the highly distinctive 'bird killer type' Camphors growing there at flowering time, airmailed to Kew Botanic Gardens, Londond/K.) for technical appraisal and advice.
Significant differences exist between the aggregated data for 'floret number in-total per spike, after averaging the data for each discrete groups of figures; no overlap occurred across all groups of totals, such that clear divisions exist between all the characteristic seven (7) types of Camphor Laurel so far assessed.
Diagram 1. details the average number of florets in-total per spike, in a range from 9.0 florets
per spike through to the highest average, 36.5 florets per spike.
Total Number (Average) Florets Per Spike:
|Descriptor/Type of Tree||Yellow Leaf||Yellow-Green Leaf||Most Common (hybrid) type||(unnamed)||Least Common type||(unnamed)||'Bird Killer' type ex 3 sites|
|Range in Averages;||NA||11,2-14.8||17.2-19.5||22,2-23.9||NA||27.7-30,3||35.3-37.6|
|Number (N) of Trees:|
(Total = 62)
The Camphor trees having the most definite, and. characteristically unique morphological features are mature street-trees, planted, by Lismore Council in 1946.
High densities (of flower blossom, often extended beyond the leaf-canopy, combined with a significant frequency of 'leaf blistering' when viewed closeup are the hallmarks of a most distinctive chemotype: it was under one of these particular 'bird killer type' Camphors that berry-eating native birds were found dead in heatwave conditions at the base of a "bird killer type' tree-trunk, at the end of February 2002, by the Author.
A second, highly distinctive Camphor chemotype appears to he the 'Yellow' Leaf' trees that are particularly most common on dry hilltop and slope country in the Nimbin district; these trees consistently have the lowest number of florets per spike. On the basis of previous laboratory analyses of 'Yellow Leaf' and 'Yellow Green Leaf' types of Camphor laurel from Lismore and The Channon locations, the characteristic 'Yellowness' of Camphor chemotypes with the lowest number of florets per spike is correlated with high, and higher safrole (a carcinogen) levels in the leaves and. stems. These can he considered more toxic than most other Camphor trees, especially as safrole % contents of particular trees has been measured at up to 74% of oil distilled from hark of particular 'yellow leaf Camphors growing near Lismore (Camphor Laurel Research Centre/CRC,1999 , unpublished).
Across the range of figures shown in. Diagram One, it is significant that the known more-toxic, and most toxic/'extremely toxic' Camphor Laurels lie at both ends of the continuum of type range, and that the mass of most-common 'hybrid' (Chinese x Japanese) Camphor Laurels lies near the center of that continuum.
There are three chemotypes of Camphor Laurel that are less than highly distinctive in terms of either leaf or inflorescence morphology; two of these types have only one representative tree sampled to date. Also, they appear to have not been previously sampled for their chemical differences.
Kew-Royal Botanic Gardens (U.K.) have provided a chemical analysis of a subsampled leaf off the 'Bird Killer Camphor' tree which is also a park specimen tree in Magellan Street, Lismore, proving there to be over 93% camphor molecule in the leaf oil constituents; this is an unprecedented high level of camphor (Figure One)
Whereas the 'Bird Killer type' Camphor trees are over fifty(50) years of age, and appear to have reached full-size as park specimens, the 'Yellow Leaf type' Camphors sampled to date are generally of smaller stature, implying that they are a hybrid. (ex-Chinese x Japanese) of more recent origin.
Leaf-blistering does not appear to be associated in any way with either 'Yellow leaf type or 'Yellow -green leaf' type Camphors. The existence, and. frecpency of characteristic Leaf blistering appears to be directly correlated to dense-flowering type/ dense-fruiting type Camphor trees. The existence of leaf blisters in the canopy of 'Bird Killer type' and other Camphors of unnamed type, but having higher than average numbers of florets per spike in their inflorescences appears to be variable in location within the canopy.
It has been observed that birds of both exotic, and native species rarely if ever go into the canopy of the 'Bird Killer type' Camphor laurel tree, following a year of close observations, and record-keeping, based in a verandah hide 35 ms from, and slightly elevated equivalent to the top-canopy of the observed Camphor tree/s.
Also observed, hut nowhere recorded in scientific literature reviewed to date is the fact that no bee species, including Native Bee, or European Honeybee species attend, visit (pollen, nectar) any Camphor Laurel blossoms, in over 10 000 observations and many hours of viewing at the time of tree flowering in all the districts sampled.
That the known 'Bird killer type' Camphor trees in Lismore, Uki and elsewhere have inflorescences with exactly double the number of florets per spike (36.5), compared to that (18,25 average) on the* most commonly sampled type of Camphor Laurel growing or grown in most districts of New South Wales Northern Rivers suggests there would be a genetic basis for the chemotype differences.
Substantive evidence for the above proposition exists at the other end of the continuum of discrete types assessed to-date: the 'Yellow Leaf type' flowering rate, measured as florets per spike (9.0) is almost exactly half that (18.25) of the most common (hybrid.) type Camphor Laurels.
Also, the analyses of Kew Botanic Gardens tend to confirm that extremely high concentrations of camphor molecules in the leaves of 'Bird Killer type' trees may he the principal chemical difference between these and more common Camphor Laurels planted or gone-wild as weeds elsewhere in the region.
Extreme concentrations of camphor in-leaf may also serve to biochemically explain how some leaves of 'more toxic' Camphor trees produce blisters and appear as aberrant to the rest of the canopy. 'Bubbled 'or blistered leaves may well have so much camphor contained or stored in them that the passage of adequate supplies of water within them may be difficult - hence, the resultant blistering.
Additional substantive evidence of profound, botanical differences between the 'Bird Killer type' Camphor Laurels, and the more average and common Camphors at Lismore was provided by Kew Botanic Gardens, to the effect that microscopic examination of the cell structures of the bark and cambium in both types sampled revealed that oil or toxin excretion glands or modified entices are significantly more developed and more frequent in the branchlets of 'Bird Killer type' trees. Previous research into the different chemotypes of Camphor Laurels in New South Wales' Northern Rivers region (Firth. 1979, Stubbs 1.999 and DSARD, a review 2000) Have suggested that there is only 2 or 3 discrete types of Camphor Laurel trees. However, in Taiwan (Hiraizumi 1.950). working with older Camphor trees believed to have also been the result of a similar/near-identical 'cross' hybridisation of 'Chinese' and 'Japanese' imported Camphor tree types(circa. 1600 to 1900) described, eight chemotypes of Camphor Laurel in and around the commercial plantations of that country; all had names, and could he named or recognised from a distance. One type in Taiwan was highly priced because of its high safrole concentrations, mostly harvested from the roots/root bark, in a time (before 1980) when European countries imported large quantities of safrole to be used as a food preservative and colourant (yellow oil) in the food industry.
Although Hiraizumi(1950) did not provide any in-depth results of biochemical differences between the discrete tree types/he did recognize them all as chemically different (chemotypes). with most being able to be discerned by scent.
No previous research is published on the capacity of Camphor Laurels to kill native birds, in Australia or any other country, although one Lecture (and notes) was once provided in Lismore (1990 Floyd ) by a notable regional Botanist, who referred to a 'mass native bird death' of native pigeon species becoming over-reliant/overconsuming Camphor laurel berries, subsequent to the demise (in a cyclone) of their native Bangalow Palm food source.
Given the current findings, plus the geographic extent, and density of Camphor Laurel infestations across all districts of N.S.W.'s Northern Rivers region, and the revealed fact (Friend 2000) in "The Camphor Fact Files' that various bird species have been turned sterile due to seasonally significant consumption of fallen Camphor berries (inc. seed), there now exist sound reasons to suspect , or link the long-term demise of many native bird species to the maturity and spread of Camphor; disappearing species of native Australian birds, including one 'Presumed Extinct' species in northeastern N.S.W.. the Coxen's Fig-Parrot ( Psittaculiastris dioptbalma subsp. coxeni) and a number of species of threatened Native Pigeons can now be reasonably linked to the rise and spread of more toxic Camphor chemotypes over the past 50 years or so.
Since Camphor Laurel tree cutting for wood-slabs, veneer, and export, logs etc is an ongoing industry in this region, with the known straighter, more well-formed trees having been largely removed, over the past 60 to 80 years, there is now a high likelihood that the Camphor trees remaining represent a range of more-toxic chemotypes. Evidence for this comes from interviewing key managerial staff of leading Camphor slabmaking factories, and eminent/ notable all-of-life landowners in the Lismore district - who state that timbercutters fully recognize at least the principal 2 types of Camphor Laurel, and that the least-desirable trees are more likely to have a more toxic timber.... .."capable of causing dermatitis or serious irritation of the respiratory organs during wood processing" (Metcaife 1987, p 170).
This sort of evidence, combined with the botanical knowledge that most or many Camphor Laurel toxins are likely to be produced in the leaves or stems of trees, prior to their transport and deposition in the wood leads one to the conclusion that a more complete biochemical appraisal of all eight (8) or more existing chemotypes of this tree species is warranted. Since there are now ten known toxins in Camphor Laurel (Friend 2002 in-press), It can be surmised that some toxins will be fast-acting, whilst others will be slow in action : some toxins are believed to cause sterility (e.g. the 2 cytotoxins in the seeds, LingJung et al 1995), and this effect may take years to cause the demise of a large bird population - especially if the species has a long lifespan. These sorts of effects may not be generally researched, let alone noticed within short-term, research periods (3 to 5 years). In the case of Camphor Laurel, containing so many (10) toxins, and having a seasonal peak in Autumn (DPIQ, Veterinary Research Centre, Brisbane 2000, official Queensland Records & personal communications , fauna deaths may be visible at only one or two months of the year, but the cumulative or multiple impact/s of all the other toxins may be even more important in the long-term.
A Draft Floristic Key, albeit a highly simplified one, could well help reveal which Camphor Laurel trees, being an East Asian exotic species, are to be ecologically-tolerated in the Australian environment. A Floristic Key, combined with organic toxin analysis, and/or volatile organic compound analyses may well show that none of the present-day Camphor Laurel trees being currently sold by nurseries in some states of Australia should in future be sold anywhere.
It has been shown that amongst all the visibly different types of Camphor trees, in parks, planted by Councils, and as weeds invading World Heritage rainforests, to both high altitude, and down lo sea level in coastal districts, some are more toxic than others. A Floristic Key can help accurately identify the more toxic Camphors, prior to their recommended elimination/replacement with native tree species.
It has been noticed during the course of developing the Floristic Key, that the more-toxic Camphor laurel trees are capable of killing native birds under adverse seasonal conditions; some other chemotypes of the tree may have toxins that are killing or sterilizing other bird species more slowly.
Over the last 100 years, since Camphor Laurel first became identified as a serious 'invasive weed' pest (The Northern Star, Lismore, 1900), foresters, and timbercutters have had no reliable way of determining which type of Camphor to cut first, and how to tell the various types of timber ./chemotype of tree prior to logging. Similarly, there has been no thoroughly accurate method of telling any of the known chemotypes (Hiraizumi. 1950) apart .
It has been found by deductive reasoning, and the formation of a simple floristic key that there are discrete inflorescence, and leaf structural differences between most: or all of the most common, and most- toxic Camphor laurel chemotypes.
This Draft-Key should allow for the future taxonomic separation of the different subspecies or 'principal types' of Camphor trees (Chinese, Japanese origins) lit were originally imported to Australia (1828, 1880 respectively), and as to whether any of those type are of such low-toxicity as could be left in-place e.g. as Heritage trees, for shade or on recreational Park borders.
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Deegan J 1993 Camphor Laurel within the Richmond-Tweed Region of Northern New South Wales DSARD .1.999 'Pest to Profit'. New South Wales Department of State and Regional Development, Tweed I-Ieads.
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LingJung et al. 1995 Simultaneous Existence of Two Types of Ribosome-inactivating Proteins in the Seeds of Cinnamomum camphora -Characterisation, of the Enzymatic Activities of these Cytotoxic Proteins. Biochemica-et-Biophysica Acta. Protein Structure and Molecular Enzymology , 1252 (1.) : 15-22.
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