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Suggested Tree-Ring Research Protocols

Currently, there is no official policy for the collection of tree-ring material in Tasmania. Therefore we provide the following as suggested methodology to promote best practice among researchers working in Tasmania and elsewhere. These protocols are discussed in greater detail in Harris et al. (in press).


Permit application and minimum information

Applicants for scientific research permits in Tasmanian reserves are required to provide some basic information as part of their request. Similarly, scientists interested in conducting dendrochronological research in Tasmania should be able to provide responses to questions such as the following before being granted permission to conduct their research:
  • Where and when will you sample?
  • What are the species you will be sampling?
  • How will you minimize the impacts of your sampling? (e.g., fewer samples, phytosanitary measures)
  • Could the proposed research be carried out on existing stored material in any collection known to the applicant?
  • How will you communicate the results of your research?
  • How will the relevance to the long-term management and interpretation or understanding of Tasmania’s natural resources be communicated?
  • From what approximate date will other researchers be able to access the sample you have taken? (After 3 years would be an acceptable response, allowing a window for your exclusive research on the samples.)
  • How and where will your collected material be stored and curated while you are working on the material?
 

Risk minimisation and species protection

The type of sample collection will be influenced by the area in which the sampling occurs.  For example, felling trees to collect stem cross-sections will generally not be permitted in reserve areas. In contrast, non-destructive sampling with manual tree corers (5 mm diameter or less) would be permitted in most reserves, if all sampling conditions (e.g. phytosanitary precautions) are met.   Where a tree species is considered rare or threatened (Tasmanian Threatened Species Protection Act 1995), tree coring may be prohibited, restricted to dead trees or to a small number of living individuals.  The recovery plan or listing statement will help to determine whether a permit is issued for a listed threatened species.
 
The conditions provided below relate to the species-level impacts of dendrochronology sampling on individuals.  They are considered independently of the conservation status of the species or vegetation community within which sampling targets occur.
 
We suggest adopting the precautionary principle and minimise both the number of cores taken from a tree and the number of trees sampled. Tree cores are valuable because they are a primary source of data and have a restricted availability. If correctly stored, they can remain equally valuable for multiple studies, thus reducing the need to sample more individuals in the wild. When many cores are taken from one site they form a statistically valid collection, and it is therefore undesirable to separate the collection.  A basic requirement/condition of permit will be that they are stored and curated as a collection in a responsible institution.
 
A substantial amount of time is devoted by the dendrochronologist to preparing, measuring, and analysing tree-ring data. Provision for archiving tree-cores and the tree-ring data associated with them is also important for ensuring that the potential for further information gain is available to land management agencies and other researchers. There are already protocols for storing voucher specimens of botanical collections.  Recommended conditions for storing dendrochronology samples obtained from Tasmanian forests are included below.
 
The suggested permit conditions recommended here relate specifically to the dendrochronology sampling itself and permitting agencies reserve their right to impose other conditions or prescriptions appropriate to the site or the circumstances.  They may be due to a range of factors including access arrangements or Phytophthora hygiene measures.
 

Suggested permit conditions

  • No more than three cores to be taken per tree
    • three cores per tree allows for a sample that accounts for the problem of missing and false rings.  Greater than this number may increase the risk of long-term damage to the tree. As studies suggest it is best to implement the precautionary principle when considering tree coring (Van Mantgem and Stephenson 2004), three cores poses an acceptable risk in terms of long-term damage to the tree.
    • A standard hand corer is to be used and not a motorised corer unless specifically permitted.  (Most hand corers take a core 6 mm in diameter.  There are several kinds of motorised corers which drill out an annulus of wood around a 12 mm in diameter core sample, leaving holes 25 mm in diameter.)
  • In a stand of trees, no more than 20% of the number of trees are to be cored
    • Will allow an opportunity for future analysis of the effect of coring on tree mortality if cored and un-cored trees occur.
  • Trees with a diameter of less than 10 cm should not be cored
    • Some trees this size will suffer splitting when coring is attempted.
  • Cores must be inclined up towards the centre of the tree
    • To prevent water accumulation which increases the chance of rot and infection; can also drain water from a tree where it may be already present.
  • Instruments are to be cleaned with a suitable product such as WD40 following field trips, and between cores they are sterilised with alcohol to reduce pathogen transfer risk (Grissino-Mayer 2003).  The corer drill bit should be very sharp to reduce unnecessary injury to the tree.
  • A motorised corer is not to be used
    • These instruments create a much greater level of damage to the tree, the long term effects of which are unknown.
  • Cores must be glued on wood with water soluble glue, in case cores need to be lifted and re-oriented. The type of glue used must be recorded.
    • Gluing to wood is an efficient method for storage and has been used for many years (Ferguson 1970).
  • Cores and discs must be kept in an institutional collection and not discarded.  Material collected from public land remains the property of the Crown in the right of the State of Tasmania.
    • Under appropriate conditions (acid free) to allow for subsequent use and to reduce the replication of sampling at same sites.
    • Material to be properly marked and cross referenced with metadata.
    • If the custodian of a collection intends to separate material from that collection, such as when changing jobs, retiring, changing to other research interests, then the permitting authority must be notified to provide an opportunity for the repatriation of material to another institution in Tasmania.
  • Samples should be archived digitally.
    • Allows information to be shared and used by different institutions, also reduces unnecessary re-sampling.
  •  Scientific papers and reports resulting from the research should specify which institution holds the physical material.
  •  Information gathered must be stored on international database
  •  High resolution images are to be stored along with the accompanying meta data.
    • Images allow for re-assessment of rings/cores.  Meta data is necessary to give sample context otherwise they are practically useless.
  •  GPS coordinates or accurate map reference for each sampling location must be recorded, along with any other meta data.
  •  When coring Nothofagus cunninghamii, the core hole must be treated with “Garrison”, a fungicide which prevents myrtle wilt.  An off-label permit is required for the use of this chemical and the Agricultural Pesticides and Veterinary Medicines Authority (APVMA) should be contacted.   It must be remembered that sufficient time should be allowed to obtain a permit.

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