Rainforest Regeneration

There are four types or subforms of Rainforests in Northern New South Wales, but the one most frequently encountered in this area is known as sub-tropical Rainforest. The others being technically described as Dry Rainforest, Warm Rainforest and Cool Temperate Rainforest. Sub-tropical Rainforest grows on fertile soils such as basalt (of volcanic origin) or alluvial valley deposits where there is a high well distributed annual rainfall of over 1300 millimetres. Nearer the coast there is a variant where, what is described as Littoral Rainforest, is composed of plants adapted to high airborne salt levels.

The reality is often however, that when we go out and look at our property, what was formally lush native vegetation may have become a relative floral desert in the last hundred years or so of European settlement. Those Rainforest patches that do exist have generally been disturbed and invaded by exotic menaces that seem intent on supplanting the locals. The appropriate technique for any type of regeneration will depend on the degree of disturbance including the type and density of exotic weed species and the degree of natural regeneration that is already back, all it needs is an intelligent caring hand to encourage growth in the right direction.

Assuming we start from a cleared area of bare ground, there are four stages to the natural rehabilitation process. Stage 1 consists of soft weeds such as Blue Top ( Ageratum) and Farmer’s Friends or Cobbler’s Pegs that grow rapidly, seed prolifically but cannot tolerate too much shade and are supplanted in varying degrees by Stage 2, which are the pioneer species. Typical of this stage are trees that live up to 15 years such as the Macaranga (M. tanarius), Bleeding Heart (Homalanthus populifolius), Poison Peach (Trema aspera) and the Corkwood (Duboisia myoporoides). These short-lived shrubs also seed prolifically but cannot regenerate in their own shade and are eventually replaced by Stage 3 species. The third stage, species that may live from 15-20 years + are the nomads of the forest, and these are the trees so abundant in regrowth patches of forest or roadside avenues. The list of species is numerous, some of the most frequently encountered being the Guioa (G.semiglauca), the Red Ash (Alphitonia excelsa), Red Kamala (Mallotus phillipensis), Brown Kurrajong (Commersonia bartramia) and the Pencil Cedar (Polyscias murrayi) to name just a few. These too are adverse to living under shaded conditions and contained in their understorey is the source of their own destruction, the 4th Stage succession of trees, These are often slow to grow but may live for over a thousand years, gradually pushing up through the nomads and forming climax trees towering over the forest with other shade tolerant mature stage species occupying descending layers beneath them.

So the first thing to establish is what stage of regeneration is of direct concern to you standing there with spade in hand, complete with a vision of a mighty forest in your third eye as you contemplate a box of Rainforest tree seedlings sitting on the ground wanting to be planted out. Being human, it is our tendency to want to speed things up a bit and in future articles I will outline what we have found to be the best methods to approach various situations.

The first article will concentrate on perhaps the commonest situation … a mixture of Stage 2 & 3 species overrun with Lantana and dominated by that Asian invasion, the Camphor Laurel, and native Sally Wattle (A.melanoxylon). It’s actually not that difficult to convert this sort of mess into beautiful forest in several years; and in the next article I will explain how to go about doing this.