I’m a big fan of permaculture, and I also jointly manage a small forest (48 hectares) in the Netherlands. In the past few years, I’ve been looking for ways in which to apply permaculture principles to managing that forest. After a few years of wishing and thinking, I’ve finally hit on a great opportunity.

Doing permaculture in the forest

So far, the primary way in which permaculture has informed my choices and ideas is on the theme of diversity: adding missing species to increase nutrient retention and improve resilience to extreme weather and various scenarios of climate change. That applies to any tree, shrub or herb, native or exotic, so long as it is likely to occupy a modes niche and not take over the whole forest.

This line of thinking has been fun and I am still learning and taking bigger steps every year: I’m growing seedlings of several ‘new’ species in my back yard, to be transplanted when they reach rabbit-proof or deer-proof height, and I’m working on a plan to purchase and plant nursery-grown plug seedlings on a slightly larger scale.

Permaculture in wood harvesting

But in our forest, the big human impact is the five-year wood harvest. Our wood management co-op marks individual trees, sometimes in small clusters, and these are machine-harvested and sold to pay for taxes, insurance, building upkeep and other costs.

In that area, I have so far not been able to see much room for improvement in terms of going with the grain of nature: the selective harvesting by the co-op already mimics the missing temperate elephants that used to pull down trees for forage before humans hunted them to extinction.

Most permaculture interventions just do not scale up very well from garden to forest. In fact, there are good reasons to wonder why you would want to apply culture to a form of nature that does very well on its own, thank you. I’m currently working on post about that issue.

Very recently, however, the first meaningful opportunity for forest-scale permaculture experimentation has availed itself: the wood harvest is coming up, and part of the co-op’s plan is small-scale clear-cutting. This is the moment when big machines and paid labor are available, and when the landscape both needs protection and allows intervention.

My idea in a nutshell is to use contours, one of the penultimate permaculture design elements, to reduce the negative effects of clear-cutting and improve the soil.

Contour planting on a garden scale: slowing downhill movement of water helps the water table rise and plants grow better. On a micro scale, the furrows between the beds retain more moisture than flat land would (source: naturallivingmama.com)  

The why of it

Our forest is a flatland version of managed forests the world over: it’s located near human settlements and agriculture, it has seen intensive cattle grazing over many centuries, and it’s on the uphill part of the land (which in this area means it’s between 5 and 20 meters above the surrounding farmland).

The tops of hills always get a bad deal from nature: more exposed to wind, the soil there dries out more easily than it does downhill. Downhill areas continually receive nutrients dissolved in rainwater from areas higher up, but the highest-up parts don’t have that luxury. Human exploitation (cattle grazing) usually exacerbates this natural pattern.

These things have relevance for the upcoming wood harvest. Our co-op’s proposal is to clearcut a rectangular section of about 1 hectare, which includes the top of a hill and whose surface gently slopes down southward by about 5 meters. It was planted by a previous owner circa 1980, with a mix of Scots pine and spruce, in rows.

The area where the co-op proposes the clearcut. The white dot is the highest point, the surfaces slopes downhill about ten meters north to south (data: Algemene Hoogtekaart Nederland)

The co-op proposes this clearcutting on the argument that the trees were badly planted and not thinned in time: they have grown poorly and with too many low branches, and by now they will never grow into valuable wood, so better to harvest them now and start over with a better plan. They have a point.

But putting all of the poor growth down to bad planting and thinning is not fair to the previous owners and their hired tree planters: a bit further downhill, the same plantation is growing quite nicely. As you walk downhill, the trees get progressively taller, which is why the co-op only wants to clearcut the uphill part.

Biomass harvesting and soil poverty

Now evidently, clearcutting is not a very permaculture thing to do (although small-scale forest destruction was a natural phenomenon until 100.000 years ago, when forest elephants lived here and tore down trees for forage). It’s an economically motivated choice, but in the long run ecology is economy, so minimizing the damage from clearcutting is important.

The reason why clearcutting is damaging to nature is that exposing the soil to the elements is likely to kill most fungal life, especially if we are going to harvest not only the stems, but also the branches (to sell as biofuel), as the co-op proposed. Soil life, and fungi in particular, keep water and nutrients available for the trees, and they hold the soil together.

When soil life is killed, the soil itself quickly decays and its nutrients are washed out by the rain (or, after binding to oxygen, blown off by the wind). This is not wise, particularly with a soil that has already demonstrated how poor it is.

This is why sustainable forestry involves spreading out branch material over the bare soil to give it at least some protection from the elements.

Contour lines used as permaculture design element, in this case for farming, with a water basin near the top of the area to be cultivated. Source: Global Land Repair

Keeping the debris and spreading it around is useful for another reason: a tree stores most of its nutrients in the branches and leaves (the stems are mostly carbon, iron and calcium, which are sufficiently available even in poor soils, most of the time). Removing the debris means the new trees, especially when young and lacking deep roots, may have trouble acquiring enough nutrients.

Of course, the co-op doesn’t propose branch removal without a good reason. A major drawback to keeping the branches lying around is that it means slower regeneration, especially of pioneer species like pine and spruce. Those trees will only succeed in dry, humus-poor soil, where their faster-growing competitors like birch and black cherry are at a disadvantage.

Disc trencher with furrow. Source: Bosgroepen.nl

In order to promote pine and spruce, which are the only valuable trees that will grow well on poorer soil, the co-op proposes using a disc trencher, which is basically a funny wheel behind a tractor which opens narrow, shallow trenches of bare soil by pushing the humus aside. One reason they propose to harvest the branch material is to give the trencher good access to make these furrows.

Nutrient retention

In contrast to the almost immediately visible value of removing branches and creating bare-soil furrows, the value of decomposing branch material only proves itself in the medium term. After a few years of slow decay which mostly releases unneeded carbon, the other, more valuable nutrients will become available just when the young trees on their disturbed soil need them most.

Thus, my instinct is to leave the debris there. But leaving the soil entirely undisturbed means we’ll get another hectare or low-value birch and shrubby black cherry. Evidenty, a smart compromise is needed, and this is where permaculture finally started providing some forestry guidance.

So the puzzle is: we need a way to keep the branch material lying around and yet we also need to allow the disc trencher access so that we can have regeneration of valuable tree species. How is that possible?

Debris on contour

My plan is to ask the co-op to use their machines somewhat differently. Instead of selling the branch material for money or spreading it out for optimum soil protection, I want to ask them to pile it up in a few long lines across the clearcut, on contour. The highest-up line should run along the ridge, so that it forces winds to pass over the hill at some distance from the bare ground.

In general, I want to ask the co-op to move the branches somewhat uphill from the place where they came from: this amounts to a net uphill transport of nutrients, to counterbalance the usual downward direction of nature that will be temporarily accellerated by the blow to soil life when tree cover is suddenly removed.

Leaving branch debris behind protects and feeds seedlings (source: Silviculture Canada)

Concentrating the dead wood into lines also creates wide bands, also on contour, where the disc trencher can dig its trenches, and the dead wood will actually help to protect those trenches: in the five to ten years before they fully decompose, the branches will offer some wind protection at ground level, reducing evaporation.

Trenching on contour

In addition, I want to ask the co-op to run their disc trencher along contour lines as well. This means that the tiny ridges of pushed-up humus on either side of each trench will help to slow the downhill movement of water. With a large number of these furrows running on contour, there will be no opportunity for rainstorms to create large masses of water that might flush some of the soil downhill, as often happens on clearcut areas with an incline.

Thus, when seedlings that sprout on the bare soil in the furrows start growing their roots sideways, they will quickly find a humus layer that’s moister than it would have been on a full clearcut. Additionally, it means that most of the spruce and fir will grown in clearly visible lines, which makes it easier to protect them from competitors in their early years.

With a little help from our friends

That benefit in competitr protection, although a side effect, is quite significant for us for another reason. Removing black cherry (and sometimes birch) in the crucial first ten years after a clearcut is the one bit of forest management that we don’t farm out to the co-op: we do it by ourselves, with the help of many friends and family. In this area, there are actually two benefits.

For one, it is much nicer (and less labor-intensive) if we can instruct everyone to pull out only those cherry that directly threaten the pine and fir seedlings in the contour lines. This way our more sensitive city souls will feel that they are fundamentally protecting trees (pine) instead of fundamentally killing trees (cherry).

Incidentally, this also means that pulling out (native) birch can be part of our philosophy about keeping the forest healthy. Up till now, we have looked at our cherry-clearing as a way of protecting the forest from invasive exotic species. That’s partly true, but it sits uncomfortably with the fact that many of our most valuable timber trees are also exotic and also outcompete some native trees.

Mixing in rows

The second plus is that the pine and fir can actually benefit from those birch and cherry that grown nearby without shading them. The birch and cherry being broadleaves, their leaf litter is better able to seal off the soil surface than the needle litter from the conifers, keeping the soil moist and encouraging fungal growth that improves tree growth. Leaves also decay faster than needles, keeping more nutrients in the local cycle.

After a decade or two, this patch of land will need to be thinned in order for the pine and fir to grow to their full potential. Then, again, the contour lines will prove their worth: mowing down the birch and cherry in between the pine will be a linear job instead of criss-cross. It will also create unmistakable tractor paths for future thinnings, reducing the amount of soil that gets compacted by their wheels.

Later improvement

Once the clearcutting, branch moving and disc trenching is done, I want to try one final permaculture approach on this site. On the lower end of each of the lines of piled up branches, I want to plant a few trees of favored species that need richer soil than fir or spruce do.

On a slope, trees with high moisture and nutrient requirements should always be planted below a source of moisture or nutrients. In this image, swales filled with mulch fulfill that purpose. Source: temperate climate permaculture blog (link).

These trees would ordinarily struggle and fail in this soil. My theory is that when planted just downhill of a pile of steadily leaching nutrients, in their wind shadow and near the moist soil right below the branches, more demanding species can succeed even in poor soil.

Finally, one way we can further improve the soil and protect it from the downsides of being uphill is to use the relatively thin cherry and birch logs that we get from the first few rounds of thinning. These logs can be positioned on contour along the trunks of the remaining pine, improving once more the moisture and runoff protection.