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Dry Rainforest Reconstruction Experiments

Funding:
Xstrata Coal Mount Owen Complex

Background:
In our explorations of the steep gullies in the New Forest and the North West and North East offset areas of the Mount Owen Vegetation Complex, we discovered pockets of dry rainforest communities. Seed from a number of species was collected to start a seedling program culminating in the production of tube-stock that is currently being planted back into the offset areas and onto the rehabilitation area.
 
Aim:
Our goal has been to extend the rainforest areas to increase habitat diversity. Tree guarding and fertilizing were tested to determine whether they will improve survival and, or, growth of the species grown from tube-stock in the shadehouse.

Summary of Results:
Six rainforest species (Melaleuca styphelioides, Melia azedarach, Brachychiton populneus, Hibiscus heterophylla, Pittosporum undulatum and Hymenosporum flavum) were planted on a hillside suspected of previously sustaining a dry rainforest community. Four experimental treatments were applied to them: no treatment control, tree guard (TG), fertilizer (F), or tree guard and fertilizer (TG F). For those species where only a small number of seedlings were available, hot spot plantings were planted to observe survival and provide dispersal sources. Some vines were planted close to undesirable species, such as Olive and Rose bushes, with the aim that the vines would eventually smother them. Additional seedlings were planted in a gully, which divides the site. In total, 1065 seedlings from 18 different species were planted.

Species Planted

Common name

Ecological value

Acacia implexa

Aphaneropetalum resinosum

Brachychiton populeus

Breynia oblongifolia

Citriobatus pauciflorus

Clematis glycenoides

Clerodendron tomentosum

Eremophila debilis

Eustrephus latifolius

Hibiscus heterophylla

Hymenosporum flavum

Melaleuca styphelioides

Melia azedarach

Notelaea microcarpa

Pandorea pandorana

Pittosporum undulatum

Spartothamnaella juncea

Strebulus brunonianus

Hickory wattle

Gum vine

Kurrajong

Coffee bush

Orange thorn

Head ache vine

Downy chance

Winter apple

Wombat berry

Native rosella

Native frangipani

Prickly-leaved tea tree

White cedar

Native olive

Wonga-wonga vine

Sweet Pittosporum

none

Whalebone

small tree, nodulator (nitrogen fixation)

vine, habitat

tree, 20m

shrub, bird food

small thorny bush, bird nesting, habitat

vine, habitat

shrub- small tree, bird food, nectar

ground cover, bird food

vine, bird food

tall prickly shrub, showy flowers, habitat

tree 20m, nectar.

tree 20m, nectar, habitat

tree 20m, bird food, habitat, litter

small tree, bird food

vine, nectar, habitat

tree, 10-20m, nectar, fruit.

shrub, habitat, bird food

tree, 30m , bird food


Of the hot spot species, 56% survived the first year. Survival had decreased from the 6-month survey, probably due to exceptional grass growth smothering smaller plants. In the gully area, 69.5% of seedlings survived. The growth of vines planted around olive and rose bushes, was very slow and any effect of these vines on the introduced bushes will take some time before it can be evaluated.

In the main experiment, 74% of the plants survived after year 1. There are differences between the species, for example Melaleuca survived in all treatments whereas Hibiscus only survived if protected with tree guards (see figures below). Fertilizer often reduced survival, but increased plant growth.

This experiment has lead to the formulation of some recommendations based on the one-year (1) or six month (2) data of survival and growth so far. The table below shows no treatment effect (0), a positive effect (+) or a negative effect (-) on survival (S) or plant height (H), of adding tree guards or fertilizer.


Species

Effect of treatment


Planting recommendation

Tree guard

Fertiliser

S

H

S

H

Melaleuca stypheloides1

0

+

0

++

Direct planting possible, treatments enhance growth

Melia azedarach1

+

0

0

+

Direct planting possible, minimal treatment effects

Brachychiton populneus1

0

0

-

0

Direct planting

Hibiscus heterophylla1

+++

0

-

0

Tree guarding necessary

Pittosporum undulatum2

++

+++

+

++

Tree guards and possibly fertilizer

Hymenosporum flavum2

+++

++

+

++

Tree guards and possibly fertilizer

Conclusions:
Rainforest establishment has been surprisingly successful so far. The requirement for tree guard or fertilizer addition was found to be species-specific. A site set up on the spoil rehabilitation area has also shown great success so far, with 80% survival overall. These results have encouraged us to continue the seed collection and to grow more seedlings for planting dispersal sources into existing vegetation.