Climate Change vs Trees
How extreme temperature fluctuation can affect tree health
Written by Geoff Niblett
ISA Certification: ON 1719-A
Climate change is a huge bag of worms and will present countless new challenges to ourselves and the trees/plants. My goal is to point out a small sliver of a challenge that we have seen within the recent weeks throughout southern Ontario, where we experienced a change in temperature from -38 degrees Celsius to 8 degrees Celsius within a 48 hour period.
The trees in our forests and landscapes have become accustomed to a fairly consistent routine imposed by our four seasons. The Autumn temperatures initiate a response to liquidate foliage and the moisture/sugars within. Colder Winter months continue the trend as the moisture content in the cambium (veins and arteries of the tree) drop to a safe level to prevent damage from expansion when freezing. This is a simple way to sum up how the trees enter dormancy. This period will take days-weeks depending on the species.
Drastic fluctuation of temperatures will pose a risk for trees both cosmetically and in overall health. Let’s break this down in two parts, above ground and below ground.
A swift freeze in the Autumn months will cause damage to trees that have not yet fully prepped for the winter months. Moisture levels have not yet dropped in the wood fibres, and this flash freeze may cause sun scald (aka Southwest damage) when the moisture expands too quickly and bursts outward of the trunk, sounding similar to a gun shot. This is also called Southwest injury because it is often found on the southwest side the stem, where the sun provides it’s most intense heat in the midday, preventing those fibres to relinquish moisture and creating a buildup of pressure when exposed to instant freezing temperatures. This is most common in thin bark trees such as Beech, Japanese Maple, and many young trees.
The intense change of temperatures we have recently experienced will cause an untimely response from the trees, thinking it is time to kick back into gear and ready-up for Spring. Bud break for foliage or flowers can cause these buds to prematurely be exposed to the elements, killing them off completely. Damaging foliage can be a far worse issue than flowering buds, given the responsibility the foliage has to maintain energy income for the plant. When these buds are damaged, they may not recover and the tree will lose many individual sources of energy. Flower buds can die off, and potentially grow back later in the season than usual, making it a far less significant risk.
The roots are known to be more sensitive to fluctuating temperatures. Luckily for the tree, the soil temperatures do not change as radically as the above ground air temperatures. Root loss can be devastating to overall tree health, since they are solely responsible for nutrient and water uptake.
The larger issue for tree health in the soils is the affect caused to soil biology. A lively soil harbours the environment to provide nutrients that the tree depends on. Recycling foliage to the forest floor, then decomposing from microbes, fungi and bacterial activity will releases nitrogen and other macro/micronutrients that the tree needs. An undisturbed forest soil is better than one we can mimic with fertilizer products. A relationship that is still being studied and understood (largely thanks to a Canadian Scientist, Suzanne Simard at UBC) is with a soil fungi called Mycorrhizae. This fungi relies on a symbiotic relationship with the tree roots, where the tree trades carbon for (virtually) whatever it wants from the mycorrhizae. The mycorrhizae creates a network connecting the trees together in a forest below ground, acting as a storage bank, miner, nutrient collector, chemist and provider of all things good for the trees. It is still unknown how the rapid temperatures can affect the life of the fungi, but one thing that is certain, is that most soil biology requires oxygen. When topographic areas suddenly thaw, creating a pool of water that is unable to drain because of surrounding frozen soil, it will kill off the microbial and fungal life in the soil, halting the natural occurrence of nutrients for the tree.
Obviously climate change is a very widespread topic that is beyond the likes of my knowledge to solve, but we do have options for our local trees. The best thing we can do to prepare or soils for the winter is mulching. There are many types of mulch on the market, and nearly all of them act as an insulator for the soil over the tree roots. This can regulate the temperature and dampen the potential damage of extreme changes. If drainage is found to be a problem, True North is experienced in radial trenching and soil excavation with high power air tools which reduce the risk of root damage posed by mechanical digging.
If something does not look right with your trees or shrubs, do not hesitate to contact us for a free consultation. We will be happy to inspect the property and provide options to keep the trees and shrubs on your property as healthy as possible!