Wednesday, July 25, 2007

How to create a tropical rain forest

This is my response to a recent email: "We intend to create a multi-tier tropical rainforest along the riverbank of our (residential and commercial) scheme. We would like to know what trees and palms you would suggest for the first (uppermost) tier. If possible the tree specifications (diameter, overall height etc,) and the planting pattern and distances. What shrubs and plants would be suitable for the lower tiers including ground covers."

The property is located in Malaysia, where the climate supports tropical rain forest. To recreate such forest would be easy given time, say 20 years. But of course in a commercial property they would want it done within 20 weeks.

At the 'One Utama' shopping mall in Kuala Lumper, we were promised 18 months to create an indoor rain forest, but in the end we were able to plant our first trees only after the builders had finished and moved out. Nevertheless, our rainforest was presentable within 3 months. We had an advantage that the big trees we needed were growing close by on the same property and could be transported on a private road, and with their spreading crowns sticking out of the back of the transporter. We did not lop off any of the branches. On public roads this would not be possible.

So the size and shape of the largest trees will depend on what can be transported and the crowns may have to be trimmed. The species that can be transplanted as big trees are not many, and most are species of seasonally dry tropical forests, not of true rainforests. They include Tabebuia rosea, Pachira aquatica, Hura crepitans, Khaya senegalensis, Pterocarpus indicus and Shorea roxburghii.

Before moving big trees, I would advise removing the leaves by hand, leaving only the growing tips and youngest leaves intact. This will slow down water loss while the roots are recovering from transplanting. Wrapping the trunks in plastic sheets may also help keep the trees from drying out. The presence of growing tips will speed up recovery. Tree with big leaves are easier to deleaf than trees with lots of small leaves.

Trees should be spaced with 1m gaps between crowns. It will take a couple of years for the crowns to close up. Under the gaps, put in the smaller trees and shrubs. Fill up the gaps and plant close to get faster effect. Ground covers are sensitive to shade and moisture and each species has its own requirements. Try out different species and replace those that fade out. Palms have difficulty recovering from leaf loss, so keep as many leaves as possible while transplanting.

Sunday, July 08, 2007

Getting rid of garden refuse

All gardens generate refuse in the form of grass clippings, old leaves, pruned branches, and the trunks and limbs of felled trees. A keen gardener is supposed to enjoy turning all this into compost. Not me!

After spending much money and time on rotating compost bins, electric-powered wood chippers, temperature probes and other equipment, I have decided that composting is not how I want to spend time in the garden. Open burning is not an option. Open burning is illegal and it would irritate the neighbours. So I piled up my refuse in a secluded part of my garden and every few months I would pay for it to be carted away.

In the beginning, my pile got bigger by the week. Then after many months, an equilibrium was established. The new stuff I added to the top of the pile was balanced by the stuff disappearing at the bottom of the pile. Then after some years, a change took place and the piles began to shrink faster than I could add material to them. I think what has happened is that the population of organizms in my pile of garden refuse became more and more efficient in breaking down plant matter. Even tree trunks got broken down in a few months to the extent that they could be easily smashed into little chips with a hammer.

What is doing the work? I see mushrooms of many kinds popping up from time to time. There are lots of fat earthworms. Also insects of many kinds. There are centipedes, presumably living on the insects. There must be zillions of microbes. All they need is a diligent gardener to keep feeding them with new refuse . I no longer need to have my garden refuse carted away.

Lately, a friend working for a big property developer told me he had run out of hollows in the property to dump the tree trunks that he had been clearing. He has been clearing the property for years, phase by phase. Now getting rid of tree trunks was becoming a bigger and bigger problem. I advised him to go back to the old filled areas, excavate all the tree trunks with a backhoe machine, and smash them into chips. Then the holes would be available for refilling with new tree trunks. The rotted chips can be spread onto the lawns and gardens they are making.

In the humid tropics, the turnaround time for decay of tree trunks is less than one year; faster if one learns to feed the ecosystem that does the work. All those manuals on composting are impractical in the humid tropics, where it is moist and warm all the time and where the diversity of breakdown organisms is at the maximum.