Key words: tropical forest restoration, habitat connectivity, small mammal recolonisation, ecological processes, community partnerships.
Introduction. Closed forest species are considered especially susceptible to the effects of forest fragmentation and habitat isolation. The Wet Tropics of north Queensland contains many forest fragments between 1ha and 500ha, mostly surrounded by dairy and beef pastures, and crops such as maize, sugar cane and bananas. Larger blocks are often internally fragmented by roads and powerlines. The Lake Barrine section of Crater Lakes National Park is a 498ha fragment that is 1.2km distant from the 80,000ha Wooroonooran N.P, and ecologically isolated since the 1940s with detectable effects on genetic diversity of rainforest mammals.
In 1995 the Qld Parks and Wildlife Service, along with landholders and the local ecological restoration group TREAT Inc., began riparian forest restoration along Toohey Creek to re-connect the Barrine fragment to Wooroonooran and to document colonisation by small mammals and native plants typically associated with rain forest environments (Fig 1).
Connectivity Works. Prior to works commencement, small mammal communities (e.g. Rattus spp. and Melomys spp.) along and adjacent to Toohey Creek were sampled, along with a full vegetation survey, to determine base-line community composition and structure. Permanent stock exclusion fencing was erected and off-stream stock watering points established.
A 100m wide corridor of vegetation was established over a four year period using local provenances of 104 native species comprising around 25% pioneer species, 10% Ficus spp., and the remainder from selected primary and secondary species. In total, 20,000 trees, shrubs and vines were planted along the creek, and a three-row shelterbelt was planted adjacent to the corridor to reduce edge effects. Species were selected on a trait basis, including suitability as food plants for targeted local fauna e.g. Cassowary (Casuarius casuarius johnsonii).
Ecological furniture (e.g., rocks, logs) was placed prior to planting. On completion, the 16ha Donaghy’s Corridor Nature Refuge was declared over the area, recognising the Donaghy family’s significant land donation and the corridor’s protection by legislation. A three year monitoring program, conducted quarterly, commenced on completion of planting.
Monitoring. Flora monitoring was conducted along transects bisecting the four annual plantings (1995/96/97/98), and small mammal colonisation in 11, 20m x 20m plots located in the plantings, adjacent open paddocks, and in forests at either end. Small mammal sampling included mark-recapture and DNA studies, to determine colonisation and movement patterns and genetic effects.
Results. Three years after establishment, over 4000 native plants were recorded – representing 119 species from 48 families. This included 35 species naturally dispersed from the adjacent forest (Figs 2 and 3). Small mammal sampling showed 16 long-distance movements by Rattus species and the appearance of an FI hybrid Bush Rat (Rattus fuscipes) in the central section of the corridor in the third year of the study. The rainforest rodent Fawn-footed Melomys (Melomys cervinipes) had established territories in the second year of the study. A study of wood-boring beetles (Coleoptera)in ecological furniture showed 18 morpho-species in a three year period. Many other orders/families were also recorded.
Water quality in Toohey Creek was not studied but has continued to increase since the replacement exotic grasses with woody vegetation, and the exclusion of cattle from accessing the stream. There is increased shade available for stock and less pressure on the limited number of existing paddock shade trees.
What we learned.
- Plant colonisation was rapid, dominated by fleshy-fruited species (10-30mm diameter), of which a proportion are long-lived climax species
- Plant colonisation was initially highest in the interior, close to the creek margin, but has become more even over time
- Vegetation structural complexity and life form diversity have continued to increase since establishment
- Small mammal communities changed in response to habitat structure, grassland species dominate until weeds are shaded out when they are replaced by closed forest species
- Many long distance mammal movements occurred that were only detected by genetic analysis
- Monitoring showed small mammals used the new habitat to traverse from end to end until resources were worth defending: at that time long distance movements declined and re-capture of residents increased
- Partnerships between government, research bodies, community groups, and landholders are essential if practical solutions to fragmentation are to be developed and applied
Acknowledgements: Trees for the Evelyn and Atherton Tableland acknowledges and appreciates the support of all the volunteers involved in this project, staff from the Qld Parks and Wildlife Service-Restoration Services, , James Cook University, University of Qld, Griffith University and UCLA Berkely. In particular we would like to acknowledge the Donaghy family.
Contact: TREAT Inc. PO Box 1119, Atherton. 4883 QLD Australia. http://www.treat.net.au/
Global Restoration Network Top 25 report: http://www.treat.net.au/projects/index.html#donaghy
Watch the video on RegenTV – presented by Nigel Tucker