Tropical food forest is a context with more practical (empirical and systemic) knowledge published in Spanish and Portuguese. If you know how to use google translate open the equivalent link from our website : https://anovafloresta.wordpress.com/2016/05/17/reflorestamento-com-acacia-mangium/ and translate it !
Acacia Mangium (Acacia Australiana or Black Wattle) is a leguminous (symbiosis with nitrogen fixing bacteria) coming from Australia and frequently found in Brazil. Acacia Mangium is defined as a support species and provide with additional functions like wind break and wood for furniture or fuel.
It has amazing growing capabilities. The one on the photo below was planted end of March 2013 and the photo was taken the 4th of June 2015. It is 2 years and 2 months old and has been growing on a depleted soil lacking of organic matter and edible minerals.
This shows that you can reforest and regenerate your soil rapidely. 150 Mangium have been planted over 7000 m2 and form now the main forest structure of the farm.
The one of the photo is one of the biggest and you can find on the site various sizes although planted at the same time. Some key factors are the soil compression, the capability for the tree to find and start a symbiosis with the nitrogen fixing bacteria and humidity although A.Mangium can resist well to drought, especially in soils having a fair proportion of clay (e.g. 20%).
With regards to reforestation in the tropics you may have 2 strategies;
1) Immediate forest succession…
…by planting all the trees at the same time (fruit trees, timber trees, emergent trees, leguminous and natural soil improvement trees, under story, ground cover, etc…) including large leguminous like A. Mangium. This implies that your soil has already enough fertility to sustain some species which need a good soil or that you have enough money and time to add compost, water, protect your trees from the sun and mulch intensively.
2) Or conduct a 2 phases rehabilitation
The alternative to immediate forest succession is to plant high density of Acacia Mangium (one every 4 meters) and other resistant species (including smaller leguminous) in between (Pigeon Pea, Leucaena, Gliricidia, giant grass, Pine Apples, Cassava, giant bamboo, Acai, dwarf coconut trees, lemon and orange trees, Citronella, Pau Brasil, Biriba, Umbauba, Monjoleiro, Jabuticaba, Urucum, Aruera, Amenda, Mangaba, …) and should include large fruit perennials (jack fruits, Mango trees, Jamborao, Dende, coconut trees, etc.). The Acacia Mangium represent the fertility grid of your landscape and most of the other trees the pioneers of the future design of your site, accordingly to the different zones you have defined. The population of Mangium and some other leguminous (gliricidia, leucaena) can be pruned the second year and the mulch spread in area where vegetation has issues to develop. If you have limited resources in time and money and an important surface area to reforest you may focus your reforestation;
– on tree clusters spread regularly on the site. They will become green islands you may stretch in the direction opposite to the sun course and/or prevailing drying wind. These tree clusters may as well become the habitat for fruit trees propagators like bats and birds.
– down the swales where water table will raise over time
– around your gray and brown water recycling systems (banana circle, evapo-transpiration tank)
After 1 year you may plant nutrients accumulators (comfrey or tropical alternatives) which will accumulate minerals and carbohydrates.
Over 2 years you may start to have compost and identify fertile and humid spot where you can start to plant demanding or more sophisticated species (Banana, Papaya, Amora, Graviola, lemon grass, sweet potatoes, BiriBiri, Cocoa, Cupuaçu, Cherimoya, Advogado, Cashew trees, Passion Fruits, Genipapo, sugar cane, Xuxu, etc…). These spots need to be mulched intensively with the pruning of Mangium and other leguminous. At this point you may plant more sophisticated leguminous like Inga Edulis smaller than Mangium with a beautiful parasol shape. These Ingas may become part of the permanent 20% leguminous species you’ll keep in your food forest. Being in the tropics trees are not impacted by winter and can handle well the pruning. Ingas can be pruned regularly and propagated easily in the future.
(Picture above : the leaves of an adult acacia mangium are false leaves; a modification of the stem. The real leaves appear here on this seedling.)
At this point some cover ground protecting and improving the soil will be able to settle like Arachis Pintoi.
You may diversify the range of productive species in order to spread the periods of harvesting over time. You may add Mycorrhizae fungi where new species are located to help them get the nutrients and resources provided by the growing forest.
When reforesting an area you’ll face the destruction of leaves cutting ants which can come from long distance (neighborhood) attracted by the new vegetation you are trying to settle. Mulching is one of the best solution to create barriers making their pathway problematic. Another solution is the settlement of Arachis Pintoi which reduces the perimeter of action of these ants.
In zone 1 dedicated to your future kitchen garden you may overload the area with pigeon peas and leucaena (that you keep always small by pruning) which can be even removed each time you need to settle a garden bed. The root systems of such plants will remain non competitive for your vegetables to grow if you keep them under control.
If a Mangium is destined to be removed (accordingly to your design) it means that other productive species can be planted very close to it and will benefit for few years from the nitrogen fixing bacteria nodules of the removed.
To be noted; a small coleopteron (bezouro serador) 3cm long (photo above) may arm your Mangium by digging a regular ring around the trunk of the tree (photo below) causing a fragility where the tree can break. The upward part of the tree over the ring will end up dying eventually. This happened 3 times on a population of 180 A.Mangium and only on A.Mangium species.
Important; plant only at the start of the humid season. Taking care of a forest of seedling planted at start of the dry season is just not sustainable. During the humid season the seedlings, if they are from resistant species, will have time to settle and very few of them will need watering in the following dry period. Mulching is a very good option assuming you have no chicken going errand. In this case put cardboard on top of the mulch so that chicken will not be willing to scratch the soil and damage the young plant. When the cardboard is degraded over time usually the young tree can then handle chicken activity.
Once the food forest reached its climax Acacia Mangium may be kept only in designated areas (wind break and zone 4 dedicated to wood material) since they are described as producing hormones inhibiting the growth of other plants. This impact was not noticed on the field but may play a growth reduction effect on the long term over closed-by vegetation.
Subcategories of support and productive trees
- Trees that accelerate regeneration and soil fertilization
leguminous (nitrogen fixing through symbioses with bacteria)
high level of sugar producers,
high volume of leaves producers
soft leaves allow faster integration in the soil ecosystem
hard leaves allow better protection of the soil over time
small leaves provide better litter density better keeping moisture
- Healing trees (eg Gliricidia. Not. etc.)
- Support trees to vines,
- Barriers against predators the weeds
- Producers of flowers to attract pollinators
- Producers of food and habitat for animals
Rising biodiversity and increasing ecosystem balance
Nitrogen recycling improvement
Attraction of pest control animals
- Windbreaking trees increase humidity
- Trees with deep roots for nutrient cycling and soil unzipping
- Trees lose all their leaves at once giving light to smaller plants periodically
Productive trees and perennials
- Fruit trees and producers of nuts
habitat construction and structures in the garden
fibers and panels (palm leaves)
- Medicine and condiments