Ecosites for Ecological Design & Permaculture: What Are They, and Why Are They Important to You (Part 1)
Intro
In this article, we are going to talk about the concept of ecosites and how they can be useful to ecological designers in the pursuit of working with nature rather than against it. Ecosites are “a distinctive kind of land with specific physical characteristics that differs from other kinds of land in its ability to produce a distinctive kind and amount of vegetation” (Range Plant Communities & Range Health Guidelines for the Foothills Parkland Natural Subregion of Alberta p. 9).
Fortunately, many provincial governments have published ecosite and plant community guides that are designed for land managers to take observed site conditions and determine what natural plant communities exist on their lands.
Why Are Ecosites Important?
The concept of ecosites will directly concern anyone who is responsible for creating and managing a garden, landscape, or a farm where the core objectives include:
- Creating a positive ecological footprint – where a design for a human landscape can contain and preserve wildlife habitat and provide ecological services and functioning.
- Reducing work – aligning your design to your project or operation’s ecosite will help you make choices that will help you avoid unnecessary maintenance work in the long term.
- Increasing resiliency – ecosites are an expression of nature’s evolved wisdom that we can learn from and apply in our designs. We’re particularly excited by how understanding ecosites can guide our planting and cropping decisions in ways that are bulletproof when it comes to climate extremes!
Having an understanding of ecosites puts us way ahead if our task is to create some sort of ecological design, be it a regenerative farm, a food forest, a schoolyard naturalization, or an ecological restoration project. The key opportunity that comes with a good understanding of the ecosite is that your design efforts will go a long way towards working with the nature of a site rather than against it. This is important in order to conceive a design that requires minimal work to maintain, preserves and enhances wildlife habitat, and achieves appropriate yield opportunities. With even a basic understanding of a landscape’s ecosite, you will be equipped to learn:
- How to interpret characteristics of the site to help make strategic design decisions with the best return on investment.
- What plants will succeed best on your site (and which ones won’t), as well as how to substitute native species with improved varieties or appropriate analogous plant species for improved yield in a way that maintains ecosystem function.
- What the disturbance regime is for the site, and how to utilize ecological disturbance to your advantage. Healthy ecosystems require some sort of disturbance regime or disruption (such as periodic fire, grazing, etc.) to maintain health, and will atrophy and lose health without it.
- Understanding ecosites gives you the keys to understanding and interpreting the biome of your property at the site scale, helping you to make design choices that are most appropriate for your property or areas within it.
What Are Ecosites?
Ecosystems are nearly infinite and interrelated systems that really don’t have clear boundaries. Fortunately, it is possible to approximate our understanding of them to make design and policy decisions that can lead to a positive human footprint. I would argue that in ecological design, we are in the practice of creating well-chosen starting points for ecosystems to develop and thrive. In other words, our design projects serve to create an initial configuration of landscape elements, plants etc. that result in a good starting point for success, and with some initial guiding through stewardship practices (see our blog posts about stewardship here), we leave the remaining complexity for the ecosystem to weave as the project ages.
Regarded this way, we can take advantage of the fact that many provincial/state governments have created approximations of the native natural environments within their jurisdictions that are differentiated by broad factors such as geography, geology, climate, broad vegetation type, and soil type. These are termed Natural Regions or some other similar name. In the province of Alberta, Canada, where we are currently based, examples of Natural Regions are the Rocky Mountain, Parkland, and Grassland natural regions to name a few.
| A note about scientific reductionism: Scientific reductionism involves approximating the real world into isolated models and ‘chunks’ where an understanding of the parts is gleaned, but a utilization of a systematic understanding of the connections between things becomes secondary. While reductionism has its place in discrete scientific applications, ecological design is a holistic science and practice, where ‘wicked’ problems demand ‘wicked’ solutions; ‘wicked’ meaning complex and interrelated issues that demand systematic and holistic solutions. As an example, spraying crops with pesticides destroys beneficial biology in the farm ecosystem that functions to help manage problematic pest species. Because ‘pest’ species reproduce faster than their predators, the crops are in fact more vulnerable after pesticide applications, begetting further and more intense pesticide applications. But the root cause is likely to do with missing predator habitat as well as poor diversity in the first place. Monocultures of a single crop create the conditions for pest infestation, whereas crop diversity makes it harder for pest populations to find their hosts, and also creates predator habitat. Reductionism tells us to respond with pesticides, holism tells us to respond by creating predator habitat and increasing crop diversity, among others. This dichotomy can explain mountain pine beetle infestations, superbugs in the hospital, destructive flooding and many other ‘wicked’ problems. I say all of this because it’s important to understand that ecosites, while themselves could validly be regarded as reduced models of the real world, should instead be utilized as points of observation and act as starting points for design. They can point you in an excellent direction for understanding the nature of your site and its story. |
Each of these Natural Regions are further divided into Natural Subregions. The way subregions are divided can be different depending on the Natural Region. In Alberta, for example, the Boreal Forest Natural Region is divided into subregions according to major changes in vegetation type as well as geological factors. In the Grassland Natural Region, subregions are divided by vegetation, but also by soils and climate factors.
In our site assessment and design work, we pay a lot of attention to the Natural Subregion level, because at this level, we can see and recognize tangible differences and characteristics in the landscape at a relatively local scale that will broadly affect how we understand the nature of our site. The Natural Subregion level groups “areas with similar landscape and climatic features”. For example, a large portion of Calgary and the lands to the west of it lie within the Foothills Parkland natural subregion of the Parkland Natural Region. Characteristic to this subregion are thick black soils, and more plant-available moisture than the grassland regions of Alberta. The dominant vegetation type is forest stands of Trembling Aspen (Populus tremuloides).
Within the subregion is a further division, and it’s at this next level of division that we have found this approach to be most useful, and thus represents the main topic of this post.
Forested natural subregions are divided into Ecological Sites, or ecosites for short. Grassland natural subregions are divided into Ecological Range Sites. The key difference between these units is that Ecological Sites are differentiated heavily by vegetation structure and type, whereas Ecological Range Sites are heavily influenced by landscape and soil type. For this article, we will base the discussion primarily on the Ecological Site (ecosite), because, in our opinion and experience, this unit provides a framework for both woody (tree and shrub) and herbaceous (grasses and forbs) plant communities for design. The core strategies presented here, however, are largely applicable to forest as well as grassland.
As mentioned above, an ecosite is defined as “a distinctive kind of land with specific physical characteristics that differs from other kinds of land in its ability to produce a distinctive kind and amount of vegetation” (Range Plant Communities & Range Health Guidelines for the Foothills Parkland Natural Subregion of Alberta p. 9).
More specifically (and of great use to ecological designers), ecosites are defined by areas of similar nutrient and moisture availability. For example, in the Foothills Parkland natural subregion, a plant called Shrubby Cinquefoil (Potentilla fruticosa) grows in an ecosite where the nutrients available to plants are poor to medium, and the average moisture availability is dry to medium (subxeric to submesic) which corresponds to ecosite ‘b’ below. Alternatively, Cow Parsnip (Heracleum maximum), thrives in an ecosite where available nutrients are rich, and available moisture is moderate to nearly wet (hygric to subhydric) which corresponds to ecosite ‘g’ below.
Many provincial governments have defined ecosites by using what is known as an edatopic grid (pictured below). This grid is a way of illustrating the character of various ecosites in the subregion based on nutrient and moisture regimes. More on this below.
Each ecosite is made up of a series of what are known as Phases. Phases refer to dominant vegetation types that naturally occur in an ecosite. The dominant vegetation can change through time, depending on when and how the site was last disturbed. This is a property of ecological succession. For example, many ecosites in the Foothills Parkland will have a grassland phase, followed by a deciduous tree and shrub phase dominated by Trembling Aspen (Populus tremuloides), and then a mixedwood phase where White Spruce (Picea glauca) grows in the understory of the aspen, and then eventually to a conifer-dominated phase of White Spruce if the site goes without a major disturbance, such as a fire.
Soil Nutrient Regime (SNR)
All plants require nutrients to grow. Soil and nutrient availability is a complete topic by itself, and we won’t be able to investigate it in depth here. All soils have some spectrum of nutrients available, and these are mostly derived from mineral particles that have originated from rocks, but are made available by soil microbes, or are locked up and rendered unavailable through lack of soil biology, or soil pH, among others. To dive into this fascinating topic, check out Doug Weatherbee’s work, Elaine Ingham, and a local Alberta authority on the subject is Mike Dorion with Living Soil Solutions.
The nutrient regime is a relative scale that is used to describe the degree of nutrients in an ecosite to which essential plant nutrients are available for plant growth. In Alberta, a 5 degree scale is used. To put this into practical context, we’ve suggested common, recognizable, and useful plants that thrive in each of the nutrient scale degrees based on our experience (native and non-native):
- Very poor – Common juniper
- Poor – Bearberry, blueberry
- Medium – Saskatoon, strawberry, bee balm
- Rich – Honeyberry, raspberry, most fruit trees
- Very rich – Lovage, rhubarb, most annual vegetables
Learning what the nutrient regime is of a particular soil is not straightforward. However, using indicator species, plants with a narrow band of ecological tolerances, can greatly help with this, such as the species suggested above. Indicator species for each ecosite are suggested in each of the Range Plant Communities & Range Health Guidelines documents which we highly recommend getting familiar with. We are working on creating a separate post about this topic in the future. Plant vigour can also provide a rough idea of available nutrients as well, where more plant vigour relates to higher nutrient availability. Soil colour is another good indicator. Black soils are typically correlated to good nutrient availability, and light coloured soils typically have poorer nutrient availability.
Soil Moisture Regime (SMR)
Soil moisture is also critical to defining the niche of various kinds of plants. Specifically, soil moisture is the ability for soil to make moisture available to plants, not how much moisture plants need. A site with high moisture availability is one that can adequately supply moisture more reliably between events that deliver water to the site, and thus has the opportunity of growing plants that have higher water needs.
The soil moisture regime is generally regarded as a relative scale that describes the degree of average moisture availability in the soil that’s available to plants. As an example, in Alberta’s range plant community guide for the Foothills Parkland natural subregion, the moisture regime is as follows. To anchor this spectrum with context, we’ve suggested examples of common and useful plants that thrive each moisture degree:
- Xeric (dry) – Prickly pear
- Subxeric – Common juniper
- Submesic – Canada buffaloberry, bearberry
- Mesic – Trembling aspen, most fruit shrubs and trees
- Subhygric – Red osier dogwood, cow parsnip
- Hygric – Labrador tea, horsetail
- Subhydric – Cattail, watercress
- Hydric (wet) – Water lotus
Quantitative and qualitative information that’s presented in a practical form is relatively sparse on this topic, however as a starting point for more information, we would recommend checking out the Alberta Government publication: Rangeland Health Assessment for Grassland, Forest & Tame Pasture, as well as the Field Manual for Describing Terrestrial Ecosystems, produced by the Government of British Columbia.
Reference Plant Community (RPC)
The final level of division of the native natural environment approximations is the plant community level. In each phase of each ecosite, plant communities have been observed and documented in terms of their plant compositions. Typically, what’s termed a reference plant community is described, along with other documented plant communities that are in different states of disturbance, especially due to grazing pressure. At least in the Alberta context, the Range Plant Communities & Range Health Assessment Guidelines documents are designed for ranchers. An RPC represents an evolved plant community that represents maximal ecological functioning and health, and is considered as a point of reference when observing other plant communities in similar ecosites. With the information contained in the Guidelines, ranchers are able to compare the plant communities found on their lands with a RPC to directly gauge if grazing activities or other disturbances are impacting plant communities (and thus ecological functioning and services) to a state away from the RPC.
We are excited about this whole concept because we would argue that if an RPC represents the evolved wisdom of nature, then the RPC also should serve as a schematic for creating the most resilient approaches to regenerative agroforestry and landscape design possible! In Part 2 of this article, we are going to get into this more, and we will discuss the applications this knowledge has for design.
Resources
- Range Plant Community Guides – scroll down to section entitled “Range Plant Community Guides”.
- BC E-Flora Electronic Atlas of the Flora of British Columbia – While this is calibrated for the more climatically-diverse BC climate, this is quite a helpful tool for determining what ecosite thousands of native plants belong to. When you search for a plant, most listings will have an “Ecology” section, and this is where you can get a picture of the ecosite that that plant thrives in. This is fantastic for using plants you might find on your land as indicator species! We use this tool all the time as we expand our knowledge of plant communities for design.
- Field Manual for Describing Terrestrial Ecosystems (BC Government) – While we haven’t yet found overly quantitative definitions of the Soil Nutrient Regime and Soil Moisture Regime, this guide provides some qualitative information on how to define those properties that define an ecosite.
- Rangeland Health Assessment for Grassland, Forest, & Tame Pasture (Alberta Government) – This is a handy field guide for understanding the health of plant communities. Among others, this guide helps you evaluate their health by comparing what plant communities you see to a reference plant community, which can be used as an indicator of disturbance, particularly grazing, to indicate when the landscape is tipping over into a destructive phase whose effects could negatively impact the ability of the land to deliver ecosystem services.
Stay tuned for Part 2 of this article, we are going to talk about specifics of how to apply this thinking to ecological design, including food forests, naturalized plant design, and ecological restoration. We will also explore what this means for land management and stewardship.
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