A Global Tree Conservation Role for an International Arboretum in Canberra

A. Burgess1 and M.M. Richardson 2
1 Curator, Canberra International Arboretum, Chief Ministers Department, ACT   
2 Botanical Consultant (www.planningforplants.com.au) 

Introduction

In 2003 the bushfire that ravaged Canberra was the catalyst for the creation of an arboretum originally envisaged by the designer of the city of Canberra, Walter Burley Griffin.   It has provided an opportunity to promote and in some cases conserve threatened species, and provides a valuable future resource in Canberra for ongoing education and research and a place for community recreation. The goal is to create a place of outstanding beauty, of international standard and interest.

In December 2003 the ACT Government agreed that the burnt-out pine forest area known as Green Hills is to be preserved as an international arboretum. It is being developed on a 250-hectare site near Lake Burley Griffin about six kilometres from the centre of Canberra. The site incorporates existing stands of Himalayan Cedar (Cedrus deodara) and Cork Oak (Quercus suber) much of which was planted about 80 years ago.

A national design competition for the Canberra lnternational Arboretum commenced in September 2004, and on 31 May 2005 the ACT Chief Minister, Jon Stanhope MLA, announced the landscape architects Taylor Cullity and Lethlean, with the architects Tonkin Zulaikha Greer, as the winners with the “100 Forests 100 Gardens” entry.  As the name suggests, the design includes a series of forests, such as the existing ones of cedars and oaks, instead of the usual wider arboretum collection of individual trees or small clumps.  Further information about the competition and the design can be seen at
http://www.cmd.act.gov.au/arboretum.

Tree Conservation

An important aspect of the “100 Forests 100 Gardens” design concept was the designers’ focus on threatened and rare trees.  This has provided an excellent theme in terms of the selection of the tree species and provided an opportunity to highlight the fact that many of the world’s trees, often common in cultivation, are in fact threatened in the wild.  For some of them, it will also help to protect them through ex situ conservation.  To help to fulfil this aim, the Canberra International Arboretum has also started negotiating an involvement with the Global Tree Campaign, a partnership between Fauna & Flora International and Botanic Gardens Conservation International.  The GTC aims to save threatened tree species through provision of information, conservation action and support for sustainable use and has already expressed an interest in the Canberra International Arboretum’s participation.

While the conservation of Australia’s flora must still be seen as the priority for the majority of conservation programs in Australia, the work that is being done at the Canberra International Arboretum takes into account its role to promote the importance of plants in a world wide sense.  Being the diplomatic capital of Australia, Canberra is well placed to fulfil such a role.  Already a number of representatives from different countries have planted a tree that is indigenous to their country.  While not all of them have been threatened species, it has always emphasised the importance of their flora.

As a part of this, it is intended to look at presenting interpretation in languages other than English that are particularly relevant to the where the trees occur naturally.  This could include an indigenous language where English is the national language.

At the individual species level, the Arboretum is also working with in-country and international conservationists.  One such species is Cedrus libani.  While the species is already in Australia and is reasonably easy to acquire, a closer link with the natural stands in Lebanon was sought.  A contact was made in Lebanon with the Lebanese Agricultural Research Institute who collected the seed at the Al Chouf Cedar Nature Reserve.  The seed was passed on to the Arboretum via the Millennium Seed Bank in Kew.  By doing so it not has only made other conservationists aware of the Arboretum but will also be an opportunity to promote the species and the Al Chouf Cedar Nature Reserve through the Lebanese Embassy in Canberra.

 

Looking west across the Canberra International Arboretum (Adam Burgess)

As some of the plants that are being planted are endangered or even critically endangered in the wild, the amount of seed available can be very limited and this has had to be addressed in terms of planting a forest lot.  An example is Sophora toromiro which was endemic to the Pacific island of Rapa Nui (Easter Island) but is now is extinct in the wild (Maunder et al, 1999).  As the Arboretum has not been able to initially produce a large enough number of plants for the total forest planting, it will share the forest lot with a ‘host species’.  In this case it will be Sophora tetraptera, a species from New Zealand, which will be planted with the Sophora toromiro and then slowly replaced as the S. toromiro is propagated.  Such propagation cannot be done using seed collected from S. toromiro in the Arboretum as the genetic difference between species within the South Pacific is very low (Hurr et al, 1999). Instead vegetative material will be collected from across the S. toromiro planting of over 100 seedlings. However, even then it is recognised that from testing done on collections in the world that the Arboretum’s S. toromiro planting is likely to still have only a low level of genetic diversity (Maunder et al, 1999).

One of the important issues that have been taken into account is the possible or recorded weediness of the trees and the CRC for Australian Weed Management’s weed status list (Randall, 2007) has played an important role in plant selection.  Several species meeting numerous of other requirements for the Arboretum have been rejected because of likely weed issues.  However, this has not been an easy task as the variation in the localities that plants have become weedy is substantial.  As a result trees known to have been weedy in areas thought different to Canberra have sometimes been accepted.  But the previous records must not be ignored and it is noted in Arboretum management plans that if a newly introduced species commences to show a weediness that could lead to it becoming naturalised, it will be removed. 

Although the majority of the forests are non indigenous trees, about 20% of the plantings are indigenous with, currently, six being threatened Eucalyptus species.  These are Eucalyptus argophloia, E.benthamii, E.lacrimans, E.michaeliana, E.morrisbyi and E.parvula. In addition, a display of local threatened and endangered species is being developed by the community-based group, Southern Tablelands Ecosystems Park (STEP) and stands of Corymbia maculata and E. tricarpa are to be grown as research lots for the Australian National University.

  Eucalyptus argophloia, less than one year after planting (Adam Burgess)

One of the lesser roles of the Arboretum will also be to trial species in Canberra’s conditions.  These will include species that have not been grown in Canberra before (such as S.toromiro) and species that have only been grown to very limited extent, such as Araucaria araucana. Among these latter species is Wollemia nobilis.  Prior to the planting of the Wollemi Pines at the Arboretum, the number growing in the ACT was still very small, having not long been discovered or being freely available for horticulture.  Since the first planting at the Arboretum, much has been learned about growing this species.  While the genetic diversity in the species is exceptionally small (Peakall et al, 2003), there is considerable landscape difference on the site where the trees are growing and the impact of those differences is already showing.  While it is a species that is not naturally exposed to climatic conditions like those in Canberra it may demonstrate the capacity to live in Canberra under the appropriate conditions.  Another of the Arboretum’s trees, Araucaria bidwilli, has already demonstrated such a capacity and being able to tolerate harsher conditions in terms of aridity and temperature may well be very relevant to possible future climate changes.



Wind protection for young Wollemia nobilis (Adam Burgess)

References:

Hurr, Kathryn A., Peter J. Lockhart, Peter B. Heenan and David Penny (1999)  Evidence for the Recent Dispersal of Sophora (Leguminosae) around the Southern Oceans: Molecular Data  Journal of Biogeography, Vol. 26, No. 3, pp. 565-577

Maunder M.M., A. Culham,  A. Bordeu, J. Allainguillaume and M. Wilkinson (1999) Genetic diversity and pedigree for Sophora toromiro: a tree extinct in the wild. Molecular Ecology Vol 8 (5) pp. 725-738

Peakall R., Ebert D., Scott L.J., Meagher P.F. and Offord C.A. (2003) Comparative genetic study confirms exceptionally low genetic variation in the ancient and endangered relictual conifer, Wollemia nobilis (Araucariaceae) Molecular Ecology, Volume 12, Number 9, pp. 2331-2343(13)

Randall R.P. (2007) The introduced flora of Australia and its weed status. CRC for Australian Weed Management

Reference to this Paper:

Burgess, A. and M. M. Richardson (2009) A Global Tree Conservation Role for an International Arboretum in Canberra  Australasian Plant Conservation 18(3)