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Overview of Mapping Tradescantia fluminensis (Trad) in CWAD’s Project Trad

The Community Weed Alliance of the Dandenongs (CWAD) has received Federal funding to mitigate the threat of Tradescantia (Trad) to the environment of the Dandenong Ranges.

The group has prepared a project plan as part of the funding application, and one aspect of it is the mapping of Trad so that work on the ground to control Trad can be properly prioritised.

In Australia, Trad spreads vegetatively (the plant does not set fertile seed in the Australian environment).  The principal ways that this happens in the Dandenongs are by dumping of garden rubbish and subsequently by water down streams.

The mapping techniques applied therefore concentrate on streams.  Within this, mapping also concentrates on the valuable biodiversity resource found in Cool Temperate Rainforest (CTR).

Priorities for mapping therefore are:

  1. Streams
  2. Within streams, the first priority for mapping is Trad within or near the CTR EVC.
  3. The next priority is Trad in the upper catchments of streams without CTR.
  4. The next priority is Trad in other streams.

The technique to be used in mapping Trad associated with CTR is detailed in “Mapping Technique for Trad_CTR on this website.  Mapping of Trad in other streams is an extension of the same technique.

Priorities for onground work to control Trad will follow the same set of priorities.

 

Technique to be used to map the presence of Tradescantia near Cool Temperate Rainforest in the Dandenongs

The Community Weed Alliance of the Dandenongs (CWAD), has received Federal funding to mitigate the threat of Tradescantia (Trad) to the environment of the Dandenong Ranges.

One important aspect of the threat is seen by the group to be the reduction of biodiversity in stands of Cool Temperate Rainforest (CTR) caused by the encroachment of Trad into these stands (See Action Statement FFG No 238).

The group has prepared a project plan as part of the funding application and one aspect of it is the mapping of Trad where it is threatening stands of CTR.

This document describes the technique we plan to use for this work. The objective is to prepare a map showing places where Trad occurs in or near stands of CTR. The intention is to direct the efficient concentration of control effort on Trad, not to prepare a definitive map of CTR. However, we believe there are areas in DRNP (and maybe outside it) where CTR occurs that are not recorded on the current maps available, so we see some value in recording these occurrences, if not their boundaries.

The technique to be used relies on the Field Identification Key given in Cameron 2011 (A Field Guide to Rainforest Identification in Victoria, DSE). Key no. 2, Central Highlands CTR Floristic Field Identification Key, will be used.

In the field, work will be carried out where we think there is CTR, either on the basis of current EVC maps showing CTR or through local knowledge. The main occurrences will be inside DRNP, but there are also occurrences on other tenures, and we plan to include these in the work, if access can be negotiated.

To collect mapping information, an observer will walk in or near the stream where CTR is thought to be. Mapping will commence when either Southern Sassafras or Trad is found.

Mapping will consist of recording a location using GPS and by listing plant species within about 10m of that point (the distance will not be measured – this is not a formal quadrat). Only the species on the Key list will be recorded (for both EVCs).

Also, at each location, the presence of Trad will be be recorded as either present or absent. If present, the patches will be nominated as one of the following:

  • dense/large (patches of pure Trad larger than 10m2)
  • dense/small (patches of pure Trad less than 10m2)
  • mixed/large (patches of Trad mixed with native spp larger than 10m2)
  • mixed/small (patches of Trad mixed with native spp less than 10m2)

These categories are chosen to guide the sort of control work required to treat Trad in these areas.

These observations will be repeated at about 30m intervals along the bed and banks of the stream.  Observations may be made away from the stream if CTR is thought to be extensive in the area concerned. Mapping will cease in a particular location when Sassafras is not found in two locations.

The product required will be the list of GPS waypoints with species lists and Trad category for each waypoint.

Analysis will consist of allocating the waypoints to Wet Forest or CTR using the Key. The points will be plotted on a map and boundaries drawn around significant occurrences of Trad and CTR (‘significant’ will be determined by experience).

This technique will probably be modified through experience in attempting to apply it, and constructive criticism from users and other interested people.