Four layers sharing the same ground on different clocks. Native canopy trees at wide spacing for the long term, fast growing biomass rows between them cut on a short cycle, dry land horticulture and medicinal crops in the understory, and below the surface a thickening topsoil layer with roots working at several depths.
The layout
Stand in an established block and you are looking at four things occupying the same ground.
Native canopy, planted at wide spacing, eventually forming the upper layer. Slow. These are the trees that will still be there when the lease ends.
Biomass rows between them. Fast growing, coppicing species that regrow from the stump after cutting. Planted densely, harvested on a short cycle, cut and regrown repeatedly.
Understory, on the ground between rows. Dry land horticulture and medicinal crops suited to partial shade as the block closes.
Below ground, the layer nobody photographs. Roots working at different depths, topsoil thickening, biochar worked in, and a water table that should be rising over the term.
This is the arrangement drawn in section on the land restoration page.
Why the layers are chosen to avoid each other
The design rule is separation. Species are selected so that they use different resources rather than the same ones.
Different rooting depths mean the canopy draws from deeper moisture while the understory uses the surface layer. In the months when water is shortest, that difference is what stops them competing.
Different heights mean light that passes the upper canopy is used lower down rather than wasted.
Different clocks mean the block is never entirely between harvests. Something is producing while something else is growing.
When multi tier planting disappoints, it is almost always because species with similar root depth and similar height were put together. That is a planning error, and it is avoidable by reading a soil test and choosing for role rather than for name.
How the block changes
Year one. Bare ground with small plants and protection. Structures are in: contour bunds, trenches, basins. Establishment watering where the site needs it. Weeding matters more than anything else, because young plants lose to grass before they lose to drought.
Years two and three. The period that decides the block. Losses show up now, gaps get filled now, and the maintenance budget is the thing most likely to run out now. Biomass rows are visibly ahead. Canopy trees still look small.
Years four to seven. The first cutting cycles come off the biomass rows, and the block starts funding more of its own upkeep. Understory crops are producing. Canopy is establishing and beginning to cast useful shade. Soil cover closes, runoff drops, weeding eases.
Year eight onward. Canopy takes over the upper layer. Biomass rows continue on their cycle underneath. Soil organic carbon and infiltration are measurably different from the baseline. This is the point at which the land is doing what the lease was signed for.
What each layer is for, in money terms
The biomass rows exist to pay for the block. Cut material becomes pellets or digester feedstock, and that revenue covers the maintenance, the protection and the people during the years when nothing else is producing.
The understory brings income forward into the early years, when a block has costs and no output.
The canopy is the long asset. It holds carbon durably, it is the layer that changes the soil and water position most, and it is what the landowner receives at the end.
Take the fast layers away and the slow layer needs somebody willing to fund a decade with no return. That is the arrangement most restoration projects assume and few sustain, and it is why the layers exist.
What it demands
More design. A planting plan per block rather than a species list, with spacing, roles and a maintenance commitment stated for a number of years.
More skill on site. Somebody has to understand both the forestry and the cropping, because the block is running both at once.
More measurement. Four layers on different clocks means survival is counted per layer rather than as a single block figure, on a fixed schedule set before planting.
What it returns for that is a block that spreads its risk, earns before the trees are grown, and hands back land in better condition than it was leased in.
See also multi tier planting, agroforestry and why tree planting projects fail.
Related questions
- How is this different from a normal plantation?
- A block plantation puts one or two species in rows at a single spacing, which is quick to establish and simple to count. Multi tier planting puts several species with different roles and different growth rates on the same ground. It takes more planning and more management, and it produces income earlier and holds up better over a long term.
- Do the layers compete with each other?
- They are chosen so that they compete as little as possible. Different rooting depths draw water from different layers, and different canopy heights use light that the others do not. Competition happens when species with similar root depth and similar height are planted together, which is a design error rather than a property of the approach.
- When does each layer start earning?
- Understory crops can return something in the first years. Biomass rows come into a cutting cycle once established and then repeat. Native canopy returns little directly for a long time, and it is the layer that holds carbon durably and remains at the end of the lease. The early layers fund the protection the slow layer needs.
- How much maintenance does it need?
- More than a single species block in the first years, mainly weeding, gap filling and protection, and the cutting cycle on the biomass rows thereafter. Maintenance in years two and three is where most restoration projects are decided, because that is when budgets usually run out and losses accumulate unnoticed.