Foreword
In 2018 I wrote this article for my friend’s website called Awkward Botany, where I have published other articles that are not as tree-focused. His website is a great place for readers to learn about the awesomeness of plants.
Ecosystems
Ecological systems are everywhere, interconnected and interdependent systems of biology, meteorology, geography, and many more systems. It’s called an ecosystem. The inside of your house is an ecosystem with its own climate, life (including, but not limited to you), and topography. Everywhere you go, you’re in some kind of ecosystem.
The same is more obviously true about your landscape. In my area of the U.S. (southeast Michigan), oftentimes forests and wetlands are removed to build suburbs. Both the appropriate soil and ecologically relevant plants are removed from a site. After the construction, these areas are re-planted with genetically inadequate plants in a poor soil. The ecosystem is modified at a rate faster than most organisms can adapt. This design of landscapes commonly used in the suburbs is inadequate in maintaining biodiversity and healthy natural ecosystems.
In some lucky areas, there are communities doing their best to maintain a strong and natural forest canopy. Leaving the secondary forests relatively untouched during the construction of the home should be the standard when developing areas for humans.
Ecosystems evolve and change, and one can argue the human-caused mass deforestation is simply another driver of ecosystem evolution. While this may be true, it is a driver that influences the ecosystem at a much greater magnitude than the other factors. It just so happens to be mitigatable or avoidable altogether.
What can cause an ecosystem to grow and change?
Let’s use a basic natural forest ecosystem. For example, the trees:
Disturbances in any ecosystem drive biological adaptation and behavioral changes from the organisms within it. Disturbances such as fire, wind events, floods, drought, and pathogens each alter the forest canopy. Fire may kill the smaller trees, wind events can blow trees over--either open the canopy up to allow dormant seeds to germinate in the new sunlight. That gives the newest genetic material a shot at the world.
Ecological disturbances are vital to plants, animals, and microbes because it keeps their genetic material up-to-date with the evolving pathogens and changing environment. More up-to-date trees means your trees need less work. The trees are more prepared for their environment and its diseases, as evidenced by their parents successfully reproducing.
We can’t control all of the ecological disturbances. But, in the urban environment, we do our best to not have large ecological disturbances. Understandably, right? We aren’t fond of wildfire, nor do we want flooding anywhere near our homes.
Applied ecosystem principles on the job
The context of my ecosystem explanation
Often times in large manmade modified landscapes, there are only an upper and middle canopy; the subcanopy layers are missing. This is a surprisingly common phenomenon in forest ecosystems, especially in urban and suburban areas. We would describe such a forest as closed-canopy.
Closed-canopy forests are naturally occurring and are not necessarily bad. The thick shade casted by the upper canopy is very dense, and as a result prevents most understory growth. Over time the closed-canopy forest will evolve and change: a large tree or limb can come down due to wind, flood, lightning may strike, or a virulent disease might move in. Whatever the disturbance, the newly-opened canopy will once again help move the ecosystem forward.
Disturbance by Pruning
A client of ours lives on a beautiful property in a dry-mesic southern forest (a closed-canopy forest). Due to all of the trees on the property, this client wanted arborist advice on landscaping solutions. The client’s smart choice lead us to an important solution.
Various large species of both white and red oaks dominate the overstory and upper emergent layers of the canopy. The trunks of these towering trees are far apart. Below these titan trees are some slightly shorter oaks, an american beech, and a few hickory species residing in the midstory. About 40 feet below are various types of moss, some stunted sedges, violets, forest grasses; a sparse herbaceous understory. Several patient serviceberries here and there, and a single red maple, about 1.5 inches in diameter and 15 feet tall at most.
The area has been undisturbed for a long time (it doesn’t even get mowed), and with the presence of oak wilt in southeast Michigan, we steered away from planting anywhere in the root zone, as it it poses a risk for oak wilt infection. Sure, we could plant an over-designed landscape to be manicured, but we had other ideas in mind.
Direct application with Two Solutions
We asked the client how long ago the red maple and serviceberries volunteered themselves into their landscape. Together, we traced the germination back to when a wind event occurred that knocked a large limb down years ago.
The red maple and serviceberries popped up as a result of new sunlight. Yet according to the client, these plants hadn’t grown much in height during the last decade or so. Why might this be? A mature plant can close holes in the canopy faster than lower story plants can, and now they don’t receive as much as light as they once had.
Now, the next time a limb falls, the maple and serviceberries will have another explosive growth spurt. There will also be other dormant seeds to germinate every time a disturbance like that occurs. This is an example of another natural phenomenon called forest succession. It is another way forest ecosystems change.
Planting foreign species in place of the native ones takes away important food sources and habitat for surrounding wildlife. So rather than landscaping in cultivar clones, and ecologically useless plants, or plants that don’t support other lifeforms, into the existing ecosystem, we proposed we could either do strategic crown thinning, or just wait for mother nature to do it for them.
Course of action
My associates and I operate on a “less is more” approach. Not touching this ecosystem is our alternative to modifying the canopy. Like a human patient undergoing surgery, cutting open any organism exposes it to infection. In time, either a natural disturbance will come through to modify the canopy, or the trees will naturally shed lower limbs on their own in a process called cladoptosis.
Strategic method of branch removal will open up the canopy, allowing more sunlight to the ground below, while keeping the trees looking true to their natural form. The climbing team would be using a type of pruning called refracturing. The openings will simulate a wind event disturbance. As a result, the landscape plants that germinate are the proper, most competitive, most hardy, most resistant, most genetically up-to-date plants. This is the true “right plant, right place,” provided no invasive buckthorns pop up.
If the customer does want to go forward with the disturbance-by-pruning, the proposal is to open the canopy during winter, as most of the canopy are oak trees. The risk of infecting these trees is reduced significantly by pruning in the winter when the vectors for oak wilt are dormant.
The canopy holes would be placed where the homeowner wants more trees. One benefit of pruning the trees is that the disturbance is controlled, rather than a wind disturbance causing a chaotic breakage into the house, for example.
Observation would begin early the following spring. We will watch for germination; it’s expected that the plants that do germinate won’t survive the competition.
What’s important about any of this?
The arborist-homeowner relationship highlighted above is an important exemplar of proper arboriculture. We offered expertise along with our services. The exchange saved the homeowner hundreds of upfront costs from the installation of a landscape, as well as future maintenance costs.
Assuming it isn’t under human-induced stress, no forest really needs human intervention. In this project, we would be looking to observe natural phenomena form the landscaping in this client’s yard. It is our preference to leave the current closed-canopy forest alone. As it stands currently, this homeowner has not yet made a decision.
The benefits of using the naturally occurring trees are plentiful. In general, up-to-date trees are more prepared for your ecosystem and support the wildlife that coevolved with them. An ever-increasingly displaced wildlife population will happily occupy new habitat; they’re here too, after all.