Restoration / Rehabilitation / Planting Techniques

The Wairambar Rainforest is almost entirely mature rainforest. 

Techniques list only apply to one rainforest edge that borders on cleared dairy land. 

The other three borders are contiguous with the UNESCO Wet Tropics World Heritage Rainforest.

Rainforest restoration in north Queensland Australia is not like gardening. Planting takes place during the cyclone season when it can get pretty hot and humid by 10:00am. Slopes can be steep and slippery with  many hidden surprises that crawl, slither or hop. Commercial nursery seedling stock  is generally pretty useless -  a limited range of "pretty" plants, most often identical clones (so if one gets dies they all die), source areas are uncertain and often from out of the local area, stock often carries pests and problems and may introduce new pests and problems.  The best source is via seed / fruit collection from nearby local rainforest of the same rainforest type. Cassowary scats are a good source of viable seed with  much higher germination rates.

To plant one seedling takes ten steps:

1. collect seed from wild- seed needs to be local to maintain rainforest integrity - soak for 24 hours to drown grubs if required

2. seed preparation - deflesh +/- any of (remove from husk, sandpaper surface of nut, crack in vise) done with rubber gloves as many fruit are toxic

3. place in seedling trays for germination, required shaded insect-proof enclosure

4. re-pot into small sterile planting tube

5. trim and re-pot into large sterile planting tube

6.  trim seedling and roots for robust shape

7. ground preparation a few months in advance mostly weed killing but may labour intensive involve removal of invasive species

8. auger holes add fertiliser +/- water crystals generally a few hours before the plant

9. plant - there is a window for annual planting of only about 8 to 10 weeks, planting is done between about 7:30 am and 11:00am 

10. mulch - return to weed if necessary - emergency watering if necessary

Why coastal rainforests are so important to the Great Barrier Reef and Inland Australia 

This area is an ancient "refugia", while the rest of Australia's climate changes over time from rainforest to desert and back again, unique circumstances assure reliable rainfall here  over millions of years. On shore breezes push humid air up the mountains to form cloud / rain. This happens when...

1. there is a a low pressure system at sea to the north or...

2. there is a high pressure system at sea to the south... and

3. via convection, every time the land is hotter than the sea.

Our critical conveyor belt:

The rainforest  effectively harvests this water as rain or through effective "cloud stripping" design features in the leaves. Rainforest s  are generally found on nutrient poor soils so in order to get the essential trace elements they need , they draw up vast amounts of water which they then eject back into the atmosphere via transpiration.  In the process of changing liquid water in the leaves to water vapour, heat is removed from the air - rainforests thus create their own cooler climate.  Rainforests filter out sediment in water and slow the draining of the land so rivers will flow clearer and that flow will be maintained longer over the year. With a constant flow over  time the rivers will deepen, become navigable again and restore coastal fishing.  Rivers emerging from rainforest filter out sediments and  will circulate cooler water onto the Great Barrier Reef in effect "air-conditioning " the reef. The dark vegetation  moves this moisture upwards via convection, clouds form  and winds move the moisture further  and further inland - the process repeats itself a number of times and like a conveyor belt  moisture is shifted in bulk inland.  Removal of coastal rainforest potentially contributes in inland desertification which we are beginning to see. It is time to stop reviewing and undertaking studies, it has been clear since the 1980's that  revegetating along the  major and minor drainages of coastal north queensland has two-fold benefit  - the Reef and Inland.

Currently restoration techniques are too labour intensive and time consuming to have any significant short term impact.  The largest volunteer group  TREAT http://treat.net.au  manages to plant  30, 000-35,000 trees per year at 1.8m spacings with a 75% to 90% survival rate. Most TREAT volunteers are also heavily involved in other types of volunteer work . The pool of local volunteers is not large enough for the scale of revegetation required. This region suffers from massive under-employment - the labour pool is there  - it is a no brainer!  Significant positive long term impact at current rates could  take a century. Healthy coastal rainforest is the key to transporting valuable moisture in land.     If we are to be serious about improving the quality of run-off onto the Great Barrier Reef then restoration / re-planting need to be done on an industrial scale entailing  the selection of a small variety of robust, resilient species capable of being cloned from multi-sourced cuttings and able to be planted mechanically.  If some of theses species for example: Davidson plum, native tamarind, lemon myrtle, macadamia nut, perfume essences,  exotic wood,  have value added potential and can compensate for the loss of some marginal crop land so much the better. A good target would be to plant at least 3 million trees a year.  Ethiopia in 2018 managed to plant tens of millions of trees in a single day!

Commercial and environmental benefits of coastal river revegetation 

Restoring the rainforest along the margins of the many major rivers that input to the Great Barrier Reef has a number of environmental and commercial benefits.

• soil loss would be reduced / eliminated

• water quality improved cooler, clearer, for longer  -->  less coral bleaching on the Great Barrier Reef

• the rivers with a good flow  for more of the year and be able to clear out the sediment load created  by the current flood / trickle regime

• less flood risk hence lower insurance costs, and once river sediment is cleared the affect of tidal surges can be slowed

• deeper clearer rivers with consistent flow would revive estuary and near-shore fishery stocks and facilitate expansion of seagrass beds

• improved  better oxygenated water quality would revive local  aquiculture initiatives and a constant nearby river flow could be used to convert from costly electrical pumping to inexpensive water powered RAM pumps

• large scale rainforest nurseries could create long-term local employment and a pool of expertise

• the rainforest restoration technology, techniques and expertise could be exported to enhance positive relationships with our nearest neighbours

• coastal forests provide the first link in a ctitical  "conveyer belt" of rain --> evaporation --> cloud --> rain that carries moisture further inland - coastal restoration mitigates  the likelyhood of inland desertification

• 20%+ of the local economies of the region rely on tourism as the rivers clear themselves of sediment and become navigable again we resurrect recreational fishing and boating enterprises lost since the 1960's, we will retain this market share only if we are seen to be proactive on arresting the deterioration of reef and rainforest

The money is there to do the job all that needs to be done is to re-brand rainforest restoration / rehabilitation: 

For example: as a sport  or sporting event, or infastructure for a foreign mining enterprise, as a potential car manufacturer, as a munitions manufacturer, as an overseas "ministers" meeting, or from millions gifted  to  "sequester carbon dioxide" from refining the fossil fuel methane (natural gas) into exportable brown hydrogen  .  ...   and voila we would be in business!

What follows are a number of  

rainforest restoration/ rehabilitation planting techniques

 and ideas that may be used on small scale projects

Technique #1  -  Wedging Out – sealing the rainforest edge

Initially a vertical wall rainforest adjoined a horizontal plain of cleared land. Drying winds could blow into the rainforest, effectively desiccating its understorey. By planting trees at the back and bushes at the front we were able to successfully wedge-out the forest boundary and restore the understorey humidity.

Evaluation of Technique: Several years on the process has proved to be highly effective. Understorey plant density and humidity levels are now similar to levels found deeper under the canopy.

Technique#2  -  Mature Rainforest Understorey Planting in Tree Fall Openings

Our mature rainforest is characterised by diverse mostly large, widely spaced trees, well connected by canopy vines, with relatively few understorey plants and a thick layer of leaf litter. About 15% of light reaches the ground. Most trees “co-operate” to keep the canopy intact with a few rebel emergents poking up into the sky. Collectively the rainforest creates its own more stable micro-climate. While the large trees do not appear to grow larger in the shot term that is just an illusion. A large rainforest tree might display 5Ha of leaf surface to the sun and a patch of mature rainforest sequester 250 tonnes of carbon per hectare per year (source:Australian National University.)

Severe cyclones Larry and Yasi torqued and broke the tops off numerous emergents. The trees struggled to survive for another decade, the loss of branches limited the volume of leaves that could be presented and the trunk fractures facilitated the ingress of fungus. So eventually they fell. Consequently quite a number of clearings in mature rainforest became available for understorey planting. We planted the rare Stockwellia quadrifida In some of the clearings, protected from feral pigs with fencing. From the photo you can see that the pigs have made numerous attempts to enter and turn over the soil in the cleared zone

The tree was discovered in 1975 and formally described for science in 2002. It is is known from only two locations deep in the north Queensland rainforest. These forest giants are relics of wetter times dating back more than 10 million years – but related to the eucalypts (family Myrtaceae) that have prospered as Australia became a drier continent.

Understorey planting is not immediately satisfying as, due to the low light, the trees grow at a very leisurely pace. For some species this may be the only way to regenerate.

Evaluation of Technique: Several years on the technique has proved to be highly effective. Feral pigs dug up a couple of sites but did not uproot the actual plantings. While growth rates under the canopy are very slow, the plantings are very healthy.  In open plantings the growth rate is very high, as a result the planted trees are not as strong and will likely have a shorter lifespan of maybe less than a hundred years. A true restoration in an open planting will take place with second, third generations - trees that can mature more slowly.  So while the instant gratification of understorey planting is not present  these plantings will likely grow up slower and live hundreds of years longer.

image above...rare stockwellia trees (the precursors of all eucalypts) in understorey planting  - notice the attempts by feral pigs to break through the protective fence

Technique#3 -  Co-planting rainforest with non-endemic plants 

Mulberry (Morus alba L) and Beach Almond (Terminalia catappa)

In our greenfield open air plot drying winds and intense heat can affect the growth of rainforest plantings.

Mulberry (Morus alba L) and Beach Almond (Terminalia catappa) grow quickly and well in these conditions.

Both species attract birds and insects with their long lived fruit and flowers. In our climate neither plant appears to be able to grow from seed. The plants we have used all come from cuttings – simply cut and stuck in the soil with about a 30% success rate.

We co-planted these non-native plants with our rainforest seedlings, not only on the windward side of the plot but also scattered through the plot.

They quickly provided a windbreak and a small measure of shade. They assist in preventing soil compaction and increased infiltration thus diminishing grass and weed growth. Birds have been attracted to them and from their droppings new native seedlings are coming up within the plot.

After a year we have about 60% of the plot shaded and anticipate having a canopy in place within about 18-24 months

Both plants have had to be pruned back at times when they interfere with the main planting. Eventually they will either be shaded out or we will have to cut them down.

After  a few years,  we are now in the process of removing the non-endemics which have provided a number of benefits to the planting . In the process of removal which will take place at the beginning of the wet season, we will take large cuttings that will be stuck in the ground to provide a windbreak in another area. Not one seed has germinated from the chosen plants, which was an excellent outcome for us. But we cannot say whether seeding could take place elsewhere - so choose  the plants for this sort of technique VERY CAREFULLY!

Evaluation of Technique: Several years on the process has proved to be highly effective. In particular non-endemics planted on up-wind boundaries have been very successful in preventing wind from drying out the young understorey. It is advisible to remove the non-endemics before they get too big. The non-endemics have now been removed from the plantings. The chosen non-endemics have a short lifespan and their seeds did not germinate, all plantings were made by poking cuttings into the soil prior to a period of rain. About 10% of the cuttings grew into plants. It is likely that if left, the non-endemics  would die of old age within about 20 years, so maybe they could have been left in place

on the left -- a beach almond (grown from cuttings) provides shading for rainforest plant stock within the planting

on the right -- mullberry plants (from cuttings) on the edge of the planting area, fruit early and often, 

 encourage  birds who distribute new rainforest seeds in their droppings

( on this site the seeds of the mullberry and beach almond  do not seem to germinate)

 The mulberry and beach almond have grown so well that they have had to be severely pruned back .

Notice how healthy the surrounding 12 month old trees are.

Carbon Credits: Essentially carbon credits remain a license to pollute

Our calculations of our 2015-2016 plot indicates that our 0.075 Ha plot has sequestered 4 tonnes of dry carbon in 12 months.(assuming dry carbon is 50% of the wet mass of a tree) which equates to 532tC/Ha at current market value (2018) of say $10/tonne which makes $5320/Ha except that it appears rainforests are excluded. Under current considerations  it would be more profitable (though illegal and immoral) to cut down our rainforest and then re-plant it with some non-native species in a monoculture plot so it would be “suitable” for carbon credits.

In the second year we planted about 40 rainforest vines (Aristolochia acuminata). Vines are an essential element of a restoration planting, not only in filling gaps (thus increasing humidity and lowering temperature) and binding everything together(for protection in cyclones) but also in providing pathways to various levels and nesting sites. Many vines are attractive to insects which attracts birds... Without vines (and fungi) it may look like rainforest but is missing a key ingredients.

Update 2022: Carbon credit marketing remains unregulated and deceptive. Essentially carbon credits remain a license to pollute. If there is to be a net benefit to Australia society two minimum criteria should be met,,,

 #1 The carbon credit  should be at least five times the pollution being offset to allow for seedlings not reaching maturity and to provide a net positive social benefit, The credit benefit needs exist before the carbon credit is issued. In other words the remediation methods need to be in place before the pollution happens. This prevents polluters from paying for their pollution via fines. 

 #2 Carbon credits must be for plantings on "non-productive" land in Australia and these plantings need to be rigorously confirmed by external inspectors. Severe penalties are essential for breaches. Penalties should not be fines but multiples of the plantings not undertaken and should not exclude jail time for directors.  Carbon Credits in offshore locations cannot be objectively verified and should be illegal in Australia. Australia should not be a supplier of  Carbon Credits for pollution taking place in foreign lands.

Technique#4  -  Green Mulch 

 using pumpkins in rainforest plantings as a living green mulch

"inoculation" with rainforest soil biota and fungi

By accident we had some compost containing pumpkin seeds fill a small fenced orchard with pumpkin vines. They required no further care The orchard trees responded well to the increased soil humidity and cooler ground 

We decided to try using pumpkins as a living green mulch in the sunny patches between trees in a one year old greenfields open air rainforest plot.

Preliminary Conditions:

• The trees need to be high enough not to get smothered by the pumpkin vines

• The trees need to show that growth spurt they get when their roots have hit the zone of permanent sub-surface moisture. This way the pumpkin and tree are using different water sources.

Benefits to Trees:

• Pumpkin roots reduce soil compaction, increase infiltration of morning dew in dry season

• Cooler ground surface conditions and smaller diurnal temperature variations

• Higher soil humidity and increased earthworm population

• Hopefully advantageous to soil micro-organisms and beneficial fungi

• Mulching affect and nutrient recycling through reduced rate of leaching

Potential problems

• Competition within plot for available water

• Attract feral pigs?

Pumpkins like sunny locations and it is our hope that as the canopy forms the pumpkins will fade away. There is an added benefit of a crop of pumpkins and plenty of seed for the next year. 

So far the green mulch has worked well though coverage is a bit slower than anticipated. Here in the tropics the pumpkin plants seem to not realse they are annuals and some have lasted a couple of years.

We plan to collect some extablished rainforest litter and "inoculate" this area with rainforest soil biota and fungi . Basically we auger shallow holes in areas with visible roots and half-fill the holes with well rotted rainforest litter then backfill with soil. Certain fungii  and micro-organisms play an important role is speeding up the rate of nutrient re-cycling from leaf litter. Will their introduced presence develop nutrient re-cycling relationships sooner?

Evaluation of Technique: Several years on the technique has not been very effective. Basically the pumpkins reach their maximum ground coverage too late in the season when the drying hot temperatures have been around for several weeks. In addition ground coverage is not universal. Having said that, the pumpkin leaf coverage though spotty does keep intense sunlight from overheating the plantings. The big drawback is that the pumpkin growth does not effectively block weed growth, in fact where the ground is shaded by pumpkin leaves the weed growth is greater. Feral pigs were not interested in the pumpkins. The pumpkins do taste good.

Technique#5  -  Removal of a tea invasion (Camellia sinensis) 

through understorey re-vegetation

Our area grows Camellia sinensis – drinking tea commercially so it grows really well here.

Many years ago, we think around 1943, some tea escaped to form a dense invasive patch on the edge and into our rainforest. The tea plants have grown to tree size. The ground is covered with generations of long lived seeds waiting for some sunlight. Once cut the tea grows back with vigour from the stump or emerges as leaves from the shallow roots. 

We do not want to spray with herbicide as in amongst the tea plants are some rare and unusual rainforest species waiting for a chance. It has been suggested that as we cut the trees we “paint “ the stumps with concentrated herbicide – but it is really nasty stuff and never intended to be used in such a concentrated form in a natural environment.We have opted for hand removal, the axe and machete and then going back over an area periodically perhaps half a dozen times to clip emergent greenery. 

Through selective felling we can minimise damage to the native plants that have waited patiently beneath the shroud of tea plants. Most of the tea plants are fallen insitu to block sunlight and provide ground shade and mulch.

By keeping the native trees in place and healthy we are able to keep light levels low enough to prevent tea seed germination. 

We plant appropriate understorey native rainforest species in the understorey. 

Once planted progress is slow but slow tree growth in the rainforest is a good thing – these understorey seedlings will be durable over the next few centuries with many of the necessary constituents of a mature rainforest already in place. 

This project will take about 10 years

Evaluation of Technique: Several years on the technique has been highly successful . The tea invasion has been halted and the growing plantings are now shading out any new germination fo tea seeds. Keeping what native canopy and understorey there was, the shade minimised the germination of the millions of teas seed blanketing the area. But the technique is very labour intensive as the tea repeatedly and tenaciously grows up from the roots of cut plants . The site has to be revisited every few months and new tea leaves clipped by hand. Attempts to "paint" stumps with Glychosphate proved ineffective as widespread new leaves continued to merged from the roots.

Left image – the tea invasion, the dark ground covered in tea seeds, too much sunlight  and all these seeds would germinate

Middle image – tea plants cut and left in situ with existing rainforest seedling left intact under the shade of the canopy 

Right image – new rainforest seedlings planted amongst the fallen tea plants, they will grow very slowly 

Image below:  a variety of favourite cassowary rainforest fruits

Technique #6 - Pre-planting of pioneer species Alphitonia petriei

This technique is to test to see if planting rainforest seedlings in an open grass field can be assisted by having some more mature pioneers species in place at the time of planting. It is hoped the pioneer species will assist the new seedling by reducing the affect of drying winds thereby maintaining humidity , providing some shade for the less sun tolerant species and reduce maximum ground temperature. None of the above factors are directly measured - the proof is in whether the seedlings remain healthy or not.

One year prior to planting  glyphosate general herbicide (150ml to 15L) was sprayed in the open largely grassy field in a small number of  1m wide strips.The dead grass was left in place. Once the grass had died the area was sprinkled with a very light dusting of lime to reduce the acidic top layers in the soil.

After rain had washed the lime in,  small patches were cleared and seeds from nearby Alphitonia petriei (Pink Ash, Sasparilla) were sprinkled on the soil. Alphitonia petriei is a drought tolerant, quick growing, short lived pioneer species only a few Alphitonia petriei came up but they have reached over 3m high in a single year without any care.

Three months prior to planting a blanket spraying of glyphosate was made to kill all the grass.

One month prior to planting the area was given a light sprinkling of lime to reduce soil acidity.

The dead grass was left in place as mulch. 

Seedlings were planted at the beginning of the "Wet" when there was a forecast of a week of wet / cloudy weather.

The rate of growth of the pioneers of course has been at a much greater rate than the seedlings. We are monoitoring this and have trimmed branches of pioneers where their shade is affecting seedling water access. 

Evaluation of Technique: Several years on the technique proved to be highly effective. The pioneer species shaded and protected the new plantings . The challenge was how to remove the fairly large pioneer species after a few years without them falling and damaging the young plantings. The pioneer species worked well on the very early stage of the planting but if left as the planting grew would interfere with the young planted trees obtaining a good even spread of branches. It is possible that leaving the pioneers species in place over their 20 or so year lifespan might be preferable, but in an exposed place the rather brittle branches of the alphitonia could fall and damage the new plantings especially in windy cyclonic weather.

Image above:

One year old Alphitonia petriei trees in restoration area prior to planting of seedlings 

Note the large area of partial shade they provide. They should provide some leeward relief from drying winds

Technique #7 - Early inclusion of rainforest vines

After a couple of  years in the ground,  green field rainforest plantings can be anywhere from 1 to 4 metres tall. The canopy is beginning to form, shade the ground and start to create a microclimate. But an essential ingredient is missing. At this stage we plant rainforest vine seedlings (generally about two years old at planting). About one tree in six gets a vine planted along it's drip line with the tendrils teased in the direction of the nearest trunk. Vines are important for a number of  reasons:

• In green field plantings, young rainforest tree trunks have grown more quickly and have a heavier leaf load  than they would under the canopy thus they are fairly weak and prone to breakage. Vines bind the trees together at all levels,  making it less likely that a trunk will break in the wind. 

• Vines assist in shading the areas between trees, keeping up humidity levels in drier weather. 

• Vines provide a "highway" network for mammals, insects , reptiles and perches for birds. This results in a faster fauna population of the plot.

• Higher fauna populations increase levels of opportunistic seeding and faster introduction of beneficial fungii 

• Vines host  and feed a number of species that would otherwise be absent

For this vine experiment we  used the vine Aristolochia acuminata (tagala) - Native Dutchmans Pipe , the host of the Cairns Birdwing Butterfly . We chose this vine because we had a ready source of viable seed, progress could be monitored by an increase in the numbers of Cairns Birdwing Butterflys, the plant is quite toxic, thus less likely to be eaten by pademelons or other herbivores. The challenge on this technique is getting vine seedlings as vines tend to be ignored in rainforest restoration where the emphasis is one getting trees to grow large quickly. Of course the first trees grown in green field plantings are "sacrificial" . They have grown too quickly and have too much leaf mass to ever survive to an age of 500 - 600 years.  Their is a fatal weakness in the young trunks, larger /  less dense cells, higher water content due to abnormally quick growth rates. Given the historic frequency of cyclones in far north Queensland it is unlikely that these quickly grown trees will ever truly mature , but  in their sacrifice, they serve a useful purpose.  It will be up to their children and grandchildren  who grow up slowly, in the dim light under the canopy  to become the dense robust trees that can survive centuries. Vines may help this first generation of green field planted trees to survive just a bit longer and will assist in increasing plot biodiversity. The vines have proven to be tough in all conditions and survived light frost and exceptionally dry episodes but their gowth so far has been quite slow. Slow rates of vine re-growth have been observed on the property in areas of cyclone damage (Cyclones Larry and Yasi), only recently  increasing as damaged vines finally reach the canopy.

Another challenge is that this particular vine gets ring-barked by the Cairns Birdwing caterpillars. Apparently the caterpillars do this to concentrate nutrients. This is sustainable when the vines are large but create a sizeable attrition rate of younger vines. So mass planting of vines is important - but the added cost of potting mix and pots for mass plantings cost a bit and tie up resources ( the pots are repeatedly re-used so slow growing seedlings tie up scarce resources) In an ideal world, with longer term priorities  we would have the luxury of growing more slower growing rainforest plants resulting in much higher integrity plantings. As things are we race to re-plant areas before the soil integrity degrades to the point where restoration  becomes problematic.

Evaluation of Technique: Several years on the technique has proven to be successful. Once an area has been planted for a few years, the introduction of vines hastens  the arrival of birds, mammals and reptiles. This assists in the natural distribution of seeds/fruit. However vine plantings are slow to grow and there was a high mortality rate amongst the young vines. Successful growth of vines required  some luck - a period of several weeks of moist weather. The butterfly host vines are producing butterflies and the butterflies attract birds.

Technique #8 Innoculation  of  Fungii and Micro-organisms to older plantings

Periodically we get large old treefalls within the canopy. These expose readily accessible rainforest soil and compost which can be harvested in small amounts and transferred to new plantings to provide a micro-organism innoculation. Previously we tried innoculation on new plantings  and may see results in the future.  But with new plantings the ground can dry out and get quite hot for micro-organisms so we have decided to repeat the technique on somewhat older plantings where the canopy is better established , the shaded ground remains cooler and the humidity level remains higher.

The method used is simple...

•  Soil / compost is collected in a bucket

• A planting auger makes a shallow hole along the dripline of  a newly planted tree (generally after year 2)

• some soil is poured into the hole

• the hole is covered over and watered.

This is a probably long term trial. It may be some time before we observe results. An observable measure may be the rate at which leaf litter breaks down in the plantings. Currently some of the leaf liter dehydrates and blows away and only a portion of leaf litter remains to decay.

Evaluation of Technique: Some years on inoculated plantings remain healthy with maybe a little less die-back but perhaps it is too early to tell