Tools for building species lists for a Little Forest
One of the most common questions we get from prospective forest planters is: How do we choose the trees that we plant in Little Forests or Pocket Forests? A Little Forest might have hundreds, or even thousands, of trees!
We’ve developed tools that we use to build species lists that generally align with the Miyawaki method. This article explains the framework and tools, so that hopefully you can find them useful as well. We’ll start by outlining the Miyawaki Method concepts that we build into our forests, then we’ll describe our two species building tools:
Framework: The Miyawaki Method
We typically follow the Miyawaki method, which lays out a formula of sorts for selecting trees. Dr. Akira Miyawaki discovered that dense plantings of saplings of varying eventual heights (layers) leads to the saplings growing more quickly than in more traditional plantings, and a vast array of biodiversity achieved in a relatively short time period. These advantages are critical when we so urgently need healthy forests to help reverse and recover from the biodiversity crisis we’re facing, and to help cool our warming planet.
The Miyawaki method divides trees into four layers by height, from tallest to shortest at maturity: Canopy, Tree, Understory Tree, and Shrub. A Miwaki forest would aim for the following layer percentages:
- Canopy 20%
- Tree 40-50%
- Subtree 25-30%
- Shrub 8-12%
Further, Miyawaki forests have Dominant Species, which are planted in larger numbers, and Supporting Species, of which there are fewer planted. There are also Rare Species, which would just be planted in small numbers.
- 5 Dominant Species make up 40-50% of total saplings.
- Supporting Species make up 25-40% of total saplings.
- Rare Species make up the rest.
One thing to note that isn’t part of the Miyawaki framework but something that we do in our little forests is to limit the coniferous species to 10% or so as, due to climate change, our area is transitioning from a Mixedwoods to Deciduous (Carolinan) forest ecosystem.
Within this framework, it is up to the community to determine which species to use, and how many of each. This allows for a wonderful creative process to unfold, in which the community studies the land, its history and its anticipated future in order to understand which species have the best chances of thriving in the forest. We also get to envision intentions for the forest in the years and decades to come, such as providing refuge for a certain bird, food for threatened pollinators, shade for children at play or stormwater management (or a combination of all of these, and more!).
So while the Miyawaki method provides a framework, there is still a lot of choice available to the community. Further, the layer percentages are just guidelines. There could be reasons you wish to have different breakdowns than what's suggested. For example, you might want a higher percentage of the shorter trees if there are reasons that taller trees are undesirable in your location. Or perhaps you want to design a graduated (soft) edge, which means you'd need more understory and shrub species.
With all of this in mind, let’s get into the nuts and bolts of building species lists. We have two primary tools that we use. The Forest Builder
and the Species list template. The Forest Builder helps us choose which species we want in our forest, and the Species List Template helps us build species lists that meet our layer percentage targets and have the appropriate distributions of Dominant, Supporting and Rare species.
Introducing the Forest Builder Spreadsheet
The Forest Builder (FB) is a Spreadsheet Database that contains information about all of the species that we would generally consider planting in our Little Forests and Pocket Forests. The FB is a constant work in progress as we are continually adding species and incorporating new knowledge as we learn more about the trees and how we can better understand where and why we would want to plant them. Your feedback is most welcome, please let us know if you have questions or comments on anything you see!
The FB currently lists over 130 species. For choosing species for our forests, we need to understand which species will work in the given site conditions, what characteristics will make them useful in a Miyawaki planting, and what our intentions are for the forest (i.e. are there any particular traits of the forest we would like to see, such as providing habitat for a particular pollinator).
So, for each species, we list things like physical characteristics, optimal growing conditions, and what a species will and won’t tolerate, so we can understand which species might work in a planting given the site’s current and future conditions. Noting whether a species is early, mid or late successional helps us ensure our forest will have trees maturing at appropriate rates for them to live well in community with one another (more to be written on this in future!). We also give particular advantages of species, such as whether a species is nitrogen fixing or provides food for humans. And we list threats that species face so that we can understand risks in planting them, and also do our best to repopulate threatened species where possible.
The 2nd tab, called Climate Mitigation - iTree Database, assigns species relative values based on their effectiveness for particular climate mitigating abilities. Examples are effectiveness at carbon storage, streamflow reduction, air temperature reduction, and air pollutant removal. This data is from the i-Tree Species Database and is not available for all species, which is why it is in a separate tab. The numbers range from 0-10, with 0 being the least and 10 being the most effective.
Filtering the species list
A note on filtering - because the FB is View-Only, filtering must be done differently than if you had full access to the sheet. We must create temporary filter views if we want to be able to filter the information (which is useful if you want to find all species that are shrubs and also tolerate drought, for example). See this document for how to create temporary filter views.
The Species List Template
Once we have an idea of species that we might want to include in our forest, it’s time to use the Species List Template to actually build our list!
We created an instruction document for building a Miyawaki species list using the Species List Template which walks you through everything from saving a copy of the template to your personal drive, to choosing Dominant, Supporting and Rare species, to determining the quantity of each species that you’ll want to order.
Please read through and then play around! We're here to help, so feel free to reach out with questions. If we have enough interest, we're happy to host a workshop to walk you through this process and discuss issues that arise. So please let us know if you’re interested in joining one of those.
Summary - the Cycle of Species List Building
We hope you find these tools and information useful!
Putting this all together, our recommendation is to start by dreaming up your forest. What species do you love? What will bring beautiful blooms or fall colours? Is there a threatened species you’d like to include? Are there particular species that would suit your site well? Use the Forest Builder in this stage to help you choose your dominant species and the supporting cast of characters.
Then, move over to the Species List template to build your list.
You’ll likely find that you’ll need to continually revisit the FB and make adjustments to your list. The FB will be particularly helpful if you find you can’t source a species that you were hoping for. You can use the FB to search for species that enjoy similar growing conditions, have similar physical characteristics, etc. You will also come up with new ideas as you learn more about your site and your vision for its future.
Planning the trees you’ll plant in your forests is a fun and rewarding process. Enjoy! And again, remember to reach out with questions or if you’d like to attend a workshop to go over all of this.
Authored by Chloe Wilson