Managing Pseudo-Primary Succession (a.k.a. “planting an empty field”)

Large scale reforestation in Brazil. We can do the same... just a little smaller.

http://www.sutmundo.com/wp-content/uploads/2010/09/re-forestation.jpg

 

I have been writing a lot lately about succession and its phases/stages and how we can use this knowledge to create more diverse and resilient ecosystems and Forest Gardens. If you remember, Primary Succession is the creation of an ecosystem from bare soil with no life in it. Secondary Succession is the regeneration of an ecosystem after a disturbance.

Now in reality, there is no place on earth that is devoid of life but for a very few places which we would not be living anyway. Every location likely had forest or meadow or prairie on it at some point in the past. Often what we find though is a place which one to two hundred years ago was a forest, but now is an abandoned corn or hayfield. The disturbance has been so large and repeated so often that we are almost starting from scratch in these locations. Trying to recreate a vibrant ecosystem, and in our case a food forest woodland, in this scenario is what I call pseudo-primary succession. The most extreme example of this that I have seen is what Geoff Lawton has done in Jordan and is well documented in his Greening the Desert video.

Many people have attempted to create a full forest garden in an abandoned farm field by planting all the fruit trees they wanted at one time. What they often end up with is a large die-off of these plants or lack of vigor in growth. It may take two or three times as long for these plantings to turn into a viable ecosystem than if they would have understood the power of succession. Many of the plants may be stunted or producing a fraction of what they have the potential to produce.

One of the big reasons that the plants do not do well in the above scenario is that they are competing with pioneer species. Pioneer species are plants, often considered weeds, which are just waiting to grow in newly turned soil. An abandoned field is full of these dormant seeds. In nature, pioneer plants are a vital part of succession. They cover the soil quickly and reduce erosion. They often have deep taproots that pull nutrients from the depths. They do well in droughty, full sun, bare soil conditions. As described previously in the stages of succession, the first plants are annuals and herbaceous perennials. Eventually shrubs and then trees appear. Pioneer species can be all of these types of plants, but the larger shrubs and trees often take many years to appear.

Let’s face it. Many of the plants we would want in a forest garden (apples, pears, peaches, etc.; a.k.a. “goal species”) are not known for their ability to withstand harsh environments of poor soil, high evaporation, and low moisture. So when we plant these somewhat weak species in a field that has limited natural fertility and is full of plants made for this environment, our weak plants are just not going to do very well. If they do well, it is because they happened to get placed in a very forgiving microclimate or because we have done a lot of work to provide for their exacting needs.

But I don’t want to do a lot of work if I can let nature do it for me.

This is where managing the pseudo-primary succession comes in to play. We can choose the pioneer species that grow on our land. Granted, there will always be other pioneer species that we did not plant or did not desire, but we will tip the balance in our favor by seeding and direct planting of our desired species.

So what makes a pioneer species desirable? Here is a partial list of attributes we are looking for in pioneer species:

 

ATTRIBUTES FOR PIONEER SPECIES

• Grows Well in the Soil we Have – “poor” soils have different meanings around the world)
• Grows Well with Moisture We Have – typically this is low to very low moisture
• Fast Growing
• Nitrogen Fixing – Having a high proportion of plants that put nitrogen back into the soil will enhance soil fertility; nitrogen fixing trees are strongly recommended
• Produces High Levels of Biomass – leaves and branches that fall off every year which increase the organic components of the soil
• Dynamic Accumulators – plants that put nutrients into their leaves, often mined from well below the soil surface through deep taproots, and then lose those leaves each year increasing the mineral content of the topsoil
• Producer – if the plant can provide us a harvest, all the better!
• Tolerates Frequent Pruning – we can build soil faster by chopping back leaves and spreading them around on the ground (a.k.a. “chop and drop”) when a plant can quickly regrow those leaves. Some plants can tolerate quite heavy prunings two or three times a growing season.
• Intolerant of Shade – I’ll explain why this is important in just a bit

Once we have our bare land ready, and this may take some earthworks (pond creation, swale creation, etc.) which I have and will discuss in other articles, then we can plant our chosen pioneer species. As I said, pioneer species can range in form from annuals to trees. We can blanket the ground in seeds of annuals and herbaceous perennials to start, but we can fast forward the natural progression which can take over a decade, by directly planting pioneer shrubs and trees species as well.

Some people will give anywhere from one to three seasons for the pioneering woodland to mature. Others will just plant the goal species at the same time. I don’t think there has been enough research yet to know which method is better. I think giving things at least one season makes sense. This allows the barren site to begin resembling a small woodland (Oldfield Mosaic stage). Then the goal species are planted near the nitrogen fixing trees. Our goal species then have what is known as a nurse tree growing near it providing wind protection, excessive sun protection, evaporation protection, and excess nutrients primarily of nitrogen but also other nutrients from the other pioneer species near it.

Within a few more years, the goal species are growing vigorously alongside their nurse trees. Eventually, often only after two or three years, our goal species are getting crowded. This is when we cut back or cut down our nurse trees. These trees can be used for firewood, lumber, mulch, mushrooms, etc. Now the goal species has a sudden increase in light and below ground biomass (i.e. nutrient load), and there is often another surge of growth as our goal species become the new canopy layer in our woodland.

Some of the reseeding annuals, herbaceous perennials, and shrubs will continue growing in patches of sunlight, but all the other plants will eventually find themselves in shade. If we chose plants intolerant of shade, which was one of our goals, then they will die out. This leaves us room to plant other goal species of reseeding annuals, herbaceous perennials, and shrubs that thrive in the understory yet still provide us with direct or indirect uses. Direct use would be the harvest of fruit, vegetable, wood, fuel, cordage, medicinals, animal feeds, etc. Indirect use would be beneficial insect attractors, dynamic accumulators, mulch plants, windbreak plants, barrier plants, etc.

Using succession, or what I call managed pseudo-primary succession, will give us a more vibrant, diverse, and fertile ecosystem which is typically established much sooner than a forest garden planted without regard to succession.

I’ll be providing a list of Pioneer Species soon, so stay tuned.
 

Using Succession in Permaculture

Martin Crawford, the UK's premier Forest Gardener in his own Forest Garden.

http://www.tcpermaculture.blogspot.pt/2011/06/permaculture-projects-coppicing.html

 

 

I recently wrote about succession in ecosystems. So, how do we apply that knowledge? This is a great place to utilize Permaculture Principle One: Observe and Interact. Now that we have a better understanding of succession, we can answer an important question when we are evaluating or “observing” a piece of land. What state of succession is this land in right now? Likely, our answer will be something like this: The section over here is in a Steady State (or close to it). The section over there is Oldfield Mosaic. This area that used to be a corn field is just entering Soil Initiation.

The “interact” portion of Permaculture Principle One has a bit more to it. It really depends on our goals. Most people would naturally think that our goal should be do develop and design for a Climax or Steady State. However, we now know that production peaks in mid-succession. When exactly this occurs is a lot more difficult to pin down, but it is typically somewhere from the Oldfield Mosaic stage to the Transition to early Climax stage. We also know that diversity increases with more disturbances. In a sense, we never want our land to arrive at the Climax stage, but we would rather it continuously cycle between disturbance and secondary succession.

It is those disturbances that we will create and manage to keep our ecosystem productive. We don’t do this with burning down our forest or bulldozing all the fruit trees, but we do it with pruning, culling, coppicing, and harvesting. We can also manage the secondary succession, give it direction, and help it on its way.

So how is this done? Let’s take a closer look at each of these methods.

Pruning – this is trimming a plant to accomplish a number of goals. It can be used to trim away diseased portions of the plant. It can be used to trim away dead or old non-productive branches. It can be used to open up space for a view or to cut back overgrowth on a trail or path. It can be used to allow more sunlight through the branches. It can be used to thin a tree to allow more wind to go through the plant than over and around it. It can be used to shorten the plant for easier harvest or to prevent it from growing over a roof or into electric lines. It can be used to train a plant to grow in a certain pattern or direction. The list can go on and on. Whatever the reason for our pruning, it allows more sun and rainfall through, and therefore changes the microclimate underneath. We can plant species that will grow well in this new microclimate or let the understory change on its own.

Culling – this is removing a plant for a number of reasons. We cull plants because they are too big, too small, too expansive, too much work, not productive enough, not a species or variety we like (appearance, fruit, etc.), if it was planted in the wrong place years ago, if it is casting too much shade, blocking too much wind, blocking a view, too disease or pest prone, etc. When we cull a plant, especially a large shrub or tree, we suddenly have a very large area underneath no exposed to sunlight, rainfall, evaporation, decreased shade, decreased leaf fall, etc. This is an opportunity for sun loving plants fill that void. We can let nature decide, but better yet (since this is typically a much larger space) we can immediately fill that gap with plants that would do well in that new microclimate. Fill it will plants that can benefit us and the ecosystem as a whole.

Coppicing – this is cutting trunk and branches from a tree to harvest the wood while not killing the plant. In a number of years, and this varies depending on species and climate, the plant can be harvested again. Read this article for a more in depth description. Coppicing lies between pruning and culling. It significantly opens up a large gap as culling does, but it does not leave that space open for other large shrubs or trees to take over. Plant species with shorter life spans can grow, mature, and produce a good harvest for a few years before the coppiced plant shades out the understory again. Blackberries and gooseberries are shrubs that can fill this niche, but many herbaceous perennials will as well. Herbs and even annual vegetable gardens can be even placed here for a few years. This will take advantage of the good soil that had been building up under the tree, and will give us reason to rotate our annual vegetable plot locations. We just need to keep in mind root depth, as the coppiced tree stump or “chair” is still there in the ground (so root crops like carrots may not be a great idea), and negative allelopathy, the ability for some plants (e.g. black walnut) to produce chemicals from their roots and fallen leaves that inhibit growth of other plants.

Harvesting – this is taking anything from the plant that we are going to use. Harvesting the fruit or leaves off a plant typically is not done in such a way as to change the microclimate around the plant. The type of harvesting that will change the microclimate is with coppicing or significant pruning (e.g. bamboo).

Managing Secondary Succession – As described above, anytime we create a new microclimate and have the opportunity to sow seeds or place new plants in that location, we are, in effect, managing secondary succession. We could let nature do this on its own, but we will likely end up with plants that are considered “weeds”. What this really means is that plants for which we don’t have a significant use have filled a place we would rather grow other species. So let’s beat those less than desirable plants to the punch. If we completely fill that new location with beneficial plants and seeds that are well suited for that microclimate, then our plants will typically out-compete those other plants. If we do this over and over again with any disturbance that occurs, whether planned or unplanned, then we will eventually have a very diverse, very resilient ecosystem that is chock full of plants for which we have direct or indirect use. Direct use would be the harvest of fruit, vegetable, wood, fuel, cordage, medicinals, animal feeds, etc. Indirect use would be beneficial insect attractors, dynamic accumulators, mulch plants, windbreak plants, barrier plants, etc.

So, in closing, this is a general overview of utilizing the concepts of succession in an established woodlot or forest garden. I’ll be writing soon about how to apply succession in the development of an empty field.

 

What is Succession?

Forest Garden Succession

(click on the image to enlarge)

https://lh5.googleusercontent.com/-kdZ4OsavaL8/Tjr8tHReunI/AAAAAAAAIRM/rixJWnv7cC0/Forest_succession_depicted_over_time.jpg

In ecology, as well as in Permaculture, there is a concept known as succession. This is the idea that an ecosystem will transition through stages of growth and maturation. To look at it simply, an empty field will first grow weeds and grasses then shrubs and small fast growing trees then more mature, longer-lived trees until a forest is formed. The individual species and final result will vary depending on where in the world this occurs with its macroclimate and microclimates taken into account.

How do we define the basic steps in succession starting from a piece of bare, lifeless ground to a self-sustaining forest? There are a number of ways to categorize and describe it; following is the system I prefer:

1. Bare soil – No life here at all
2. Soil Initiation – Bacteria then Algae begin to grow and spread
3. Crust – Lichens, Mosses
4. Oldfield – Annual herbs and grasses, then Herbaceous perennials
5. Oldfield Mosaic – Shrubs begin to grow, then Sun-loving trees
6. Stand Initiation – Maturation of Sun-loving trees
7. Understory Repression – the previous herbs, grasses, herbaceous perennials, and shrubs that cannot tolerate shade will die back
8. Stand Differentiation – as faster lived trees die back, the slower growing trees fill in the gaps to complete the canopy layer
9. Understory Reinitiation – this really occurs with Stand Differentiation, and is when shade tolerant plants (sub-canopy trees, shrubs, herbs, etc.) establish under the canopy layer
10. Climax – this is the stable, self-replicating, self-sustaining ecosystem

Of course, since this is nature, there are a number of problems with any simplistic generalizations. First, there really is no place that naturally occurs where there is Bare Soil and no life. Man has created a few of these places, way too many, in fact, but they are very uncommon. Second, at the other end of our succession scale we find Climax. Unfortunately, in nature we rarely find a place that is in true Climax either.

Third, succession is not linear. What we really see in nature is a piece of land in various stages of succession. There may be a large forest somewhere close to a Climax stage when a storm blows down a massive tree. The sudden opening of the canopy, which lets in a lot more light, causes that one section to revert many years or decades, maybe to the Oldfield stage. Forest fires, floods, drought, pests, disease, and man-made interventions like logging, mining, etc. can all cause a disturbance in the natural progression of linear succession. What we actually see in nature is a constant cycling back around through these stages. This is known as a Shifting Mosaic.

In the Shifting Mosaic theory there are a few phases:

1. Primary Succession – described above
2. Disturbance – described above
3. Reorganization – the ecosystem reestablishes control of the energy flows of nutrients, sunlight, water, etc.
4. Aggradation Stage – this is just a fancy way of saying the “building up” stage; has also been called Secondary Succession
5. Transition – this is where the ecosystem is maturing, but is not yet at the Climax stage
6. Steady State – this is another way of describing the Climax stage

Again, this does not perfectly describe what happens in nature. Ecosystems will cycle through the disturbance, reorganization, aggradation, transition phases only to be hit with another disturbance before a steady state has been reached. This will happen over and over again. Also, the idea of a stead state is also not static or stable. There are always shiftings of species diversity and plant density and small disturbances with isolated reorganization and aggradation here and there. I love David Jacke’s phrase for this: Cycles of Succession and Wobbling Stability.

It is important to keep in mind that this non-linear journey of succession actually leads to a more diverse ecosystem in the long run. There are more opportunities for new plant species to grow and develop a niche.

So there you have it. A quick primer on ecosystem succession. I'll be writing soon on how to apply this to Permaculture design.

  

Permaculture Succession

This tiny apple seedling...

http://upload.wikimedia.org/wikipedia/commons/e/ec/Apple_seedling_idared_HDR.jpg

...will one day become a large tree, but it can take a decade.

http://www.hellers.org/ride/OurPics/AppleTree.jpg

When most of us think about landscape design, we think about what goes where. We think about three dimensions. Height. Width. Depth. The X-Y-Z axis... Will this plant "work" here or there? I think I will plant this shrub next to this tree for a specific benefit.

A few of us will think about seasonal changes... This deciduous tree will lose its leaves in Autumn and let sunlight through in the Winter. These bulbs will come up in early Spring, bloom, and die back before my other perennials really start growing tall enough to over-shadow them.

There are even fewer still who will think about the changes that take place over years or decades. This is the realm of Succussion.

Succession is a well known ecological concept.

We need to remember that Permaculture is about modeling the natural world...

so our designed ecosystems should at the minimum acknowledge succession.

http://people.eku.edu/ritchisong/primarysuccession.jpg

Succession, in a Permaculture or Forest Gardening world, deals with the design of plant community changes and transformations over the fourth dimension... time. This is a massive topic. When we starts to think about it in depth, we can get easily overwhelmed. I just want to introduce the topic today. Future articles will tackle specific aspects of succession, but today, I just want to wrap our minds around the idea of design over years.

Let's just take the planting of a single tree. Let's make it a full-sized, or standard, apple tree. This tree will take up to eight years to begin producing and over a decade to begin producing full crops (yet another reason I need to get my land as soon as possible! but that is another story). In a Permaculture design, especially a Forest Garden, we need to remember that this tree will not be growing on its own in a field by itself. There will be other plants around it. There will be other trees nearby. But this tree when first planted is likely only a few years old and no more than a few feet tall... a spindly twiggy shadow of what it will be in future years.

The most important thing we need to do is plan for the future mature size of this tree. The biggest mistake people make in planting trees in a Forest Garden is to plant trees way too close together. This is done often because they have limited space and want to squeeze as many varieties of plants and trees in as they can, and this temptation is made easier when the trees are so small to begin. The second reason, closely related to the first, is that because the tree is so small in its young stage, it is hard to picture what it will be like when full grown. Its hard to see that one foot sapling black walnut as a towering 100 foot (30 meter) colossal tree.

I cannot overemphasize the importance of schematic sketches of our land. We need to have a rough sketch, at the minimum, even if you are not a great artist, of what the land will look like in 1 year, 5 years, 10 years, 20 years, etc. We need to keep in mind how things will change, because they will change! This is not a bad thing. In fact, it is what we want!

I've seen too many people get upset that, for instance, a ten year old raspberry patch just isn't producing anymore. They don't want to pull it out, because they are attached to it. But it isn't producing much anymore, and the birds eat what is produced. It then gets straggly and overgrown and frankly, quite ugly looking. Well, raspberries only have about a ten year useful life! What did you expect? Plan for that change!

How about this? Place that raspberry patch surrounding that young apple tree. We will be using that space that will one day be shaded out by that apple tree. We will be protecting that young apple tree by surrounding it with thorny plants to keep the deer away. We will be collecting a yield from that land until the apple tree really starts to produce. The raspberries will just be fading out as part of their normal life cycle just as the apple is coming into its own. We will be motivated to clear out the old raspberries, so we can harvest the apples easier.

This is the concept of succession. Start thinking in the fourth dimension!