Drylands Corridor Planting

Application and Example

Regeneration and sustenance can be difficult tasks in drylands areas which warrants careful planning and unique strategies and techniques. This is why Bill Mollison advocates breaking from traditional zone thinking when necessary as to take advantage of even just a few days of

Camino das Fades at Terra Alta, foreground away from stream brown and tough to grow, back ground along the stream and lots of growth and existing trees to build off of

Camino das Fadas at Terra Alta, foreground away from stream brown and tough to grow, back ground along the stream and lots of growth and existing trees to build off of

moisture in a stream bed.  Thus when we approach laying out reforestation, tree crops, or even locations of gardens, it is often advantageous to go stream-side in a strategy called corridor planting.  When coupled with other techniques of restoring natural stream hydrology, this strategy becomes even more potent for promoting life in these harsh places.  Even in our fairly soft Mediterranean climate in coastal Portugal at Terra Alta, we have had tremendous success on one part of our food forest that is known as Caminho das Fadas (Fairy Path) with this strategy.  There we took advantage of a flowing creek by planting many tree crops and their guilds along the waterways edge.  We dotted trees in around those that were already existent as the people of the past had also planted tree crops in this area of the land. There was also windbreak trees that extended to the creek side like lemonwood (Pittosporum eugenioides) and trees like willow that were already thriving because of their roots systems being connected to the stream. This is not a new and wonderful strategy; rather one that can be observed through how nature operates and past agricultural traditions. As a practical example we planted avocado’s in two different locations in this section of our overall food forest.  One has thrived which was planted near the stream and after four years started flowering and now in its fifth year is over 4 meters (13 ft) tall (2016).  The other place away from the stream had two trees die and we have tried to plant again there for pollination reasons after a couple of years of soil building.

Because of the extra moisture present in dry stream beds areas, it is best to start there with your plantings and break from traditional permaculture zone thinking.  There will be a flow of moisture in those runoff moments of storms but then the area itself will stay laden with moisture for longer.  This is critical as young tree roots dive for water after their transplant shock wears off or their tap-root develops if done by seed.  The depth of the water will also depend on the depth of the stream channel which is why it is so critical to restore natural hydrology in part by understanding and utilizing the sinuous form.  At Terra Alta we have been progressively adding gabions over the years.  These rock walls in the stream have created an edge; a sieve for sand, silt, and organic matter that would normally go cascading down to our local beach just a couple of kilometers away.  However significant amounts of this material is now caught by the gabions creating further filtration but also a reduction in the creek incising thus raising the water table.  Incising is the natural path of streams to go deeper and deeper in degraded systems. By adding the gabion this helps to disperse the water at a higher level as water does so out of streams in a horizontal fashion to the surrounding landscape.  If the creek is really incised then a young tree in the corridor may have to reach down two meters instead of just 50 cm to reach this extra moisture, which can mean the difference between life and death.  As these gabions trapped sands and silts we also added plants in-stream to further the edge and increase filtration and provide much-needed soil building biomass. Then biomass for mulching is produced in relative location to our plantings in the corridor. Furthermore the trees that were already existing provide us with quite a bit of woody and leafy chop and drop material.

The Process (Slideshow animation at the bottom)

Thus in true drylands areas start near the dry river beds and do what you can to slow the water and bring up the water level within it.  Plant hardy trees at first that can withstand extreme conditions of drought and heat such as acacias.  As they begin to thrive, tree crops can be added.  You can raise them on your own or purchase from nurseries.  They should be quite big before you plant them and make sure you protect them from browsers and also give them shade through an artificial shade structures and mulch them well.  The hardy trees planted initially maybe able to provide mulch after a couple of years and build on these islands of refuge.  The trees will create shade, build organic matter, and slow drying winds thus making a better microclimate for the tree crops. Keep working with the stream over the years by building more gabions and raising the level of it further over the years.  Utilize biomass that grows in the stream or on its banks to chop and drop for soil building around your tree crops.  As the system is progressing keep adding in more islands of hardy trees including nitrogen fixers and keep spreading your tree crops to these islands once they begin to take off and provide a less hostile microclimate.  Let these nuclei merge over time, small scale intensive style, and you will have established a system along the corridor even if it means walking further from the house than a traditional zone planting.  I have seen this in many places in Portugal where the valleys are full of still thriving, but abandoned, fruit trees, plant species of biodiversity, and a place where the chorus of song birds echoes.  There is more life near these water concentration points and its for you to slow down the waters cascade and take on planting in this corridor. Energy is further cycled here and as the corridor thrives, hydrology is improved, the other parts of the site can be built for further regeneration.

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Written by Doug Crouch

Header Art by Bonita Edwards

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