Urban Forest Soil Health
Combating the exterminators of soil biology beyond the forest
Written by Geoff Niblett
ISA Certification: ON 1719-A
A remarkable measure of tree health can by attributed to the health of the soil. I say that like the soil is a living thing. In fact, it is! So much of our soils are alive. If you dig your hands into a forest floor and pick up a handful of earth, more than half of what you’re holding may be alive. This active soil biology is responsible for the ongoing nutrient contribution for the roots. The cycle of foliage, branches, and dead trees landing on the forest floor, being broken down and decomposed by insects, fungi and bacteria is critical to a healthy forest.
In an urban setting much of this cycle is interrupted by countless factors. Simply removing downed foliage each Autumn is one of these factors! The foliage each year would provide a source of organic matter which will feed the many living things waiting below the turf. Composting can be an easy way to combat the lack of organic matter and feed the soil biology, but some contributors are not as easy to fix. Some of the most common contributors that I come across regularly are:
- Poor drainage leading the water buildup in a soil (effectively displacing oxygen in the soil) will kill off most soil biology, prompting a long recovery once the drainage is fixed. Soil compaction can have the exact same affect.
- The icy winter months prompt salt use, and since it is not practical for us to say not to use salt, we can help manage the salt buildup in the soil come Spring.
- New construction will disrupt the natural layers of soil, and will also scrape away the topsoil to sell it somewhere else, leaving a light-brown/grey, defunct soil. Good luck to any plants moving into this property. At least you can go to the store and buy your top soil back at a marked up price after it sits in a sealed bag for a few weeks!
- Turf presents competition to trees, but is very minor in comparison to the previously mentioned factors.
I have met with many home-owners who have been paying for services that simply do not address the problem at hand. If the soil is in a condition that cannot support the regular life cycle because it is either completely compacted or saturated, fertilizing will be ineffective. Not only does the soil require oxygen to maintain it’s continuity, but the roots require oxygen to receive the nutrients that surround the root tips in the soil. In addition, over fertilizing (specifically with high phosphorus fertilizer) can trick the tree to end it’s symbiotic relationship with the critical fungi in the soil (mycorrhizae). Since the tree think’s it has more than enough of what it needs (albeit, over a blink of time relative to the tree’s life), it tells the fungi that it is no longer needed, sends the breakup message, and finds out rather quickly (later in the season) that the well has dried up as the fertilizer is leached or absorbed, and the fungi has moved on. This is a sad story.
Since there are so many factors that can negatively affect our soils, there is not a single application that can repair all soil damage. At True North, our consultants are educated and trained to identify these issues, and help create a solution for the problem at hand. Give us a call and we will be happy to provide a free consultation to inspect your property!