Conifer Adaptations

Snow on spruce trees is a hallmark of the Canadian winter. While most PEI plants lose their leaves or disappear altogether as temperatures drop, you may not have thought about how and why conifers take a different approach. Today, we take a look!

Broad-leaved trees like Maple, Beech, and Birch produce big leaves with huge surface areas that are very efficient at catching sunlight and turning it into food for the tree. Even if those leaves didn’t freeze, they lose water and catch wind – major disadvantages in the dry and windy winter. As a result, these trees cut their losses and drop their leaves in fall.

Unlike deciduous leaves, conifer needles are designed for cold, dry, windy weather. Their small size has far less surface area than a broad leaf, making them more resistant to water loss and wind damage. Needles also have a waxy coating to further reduce water loss, along with proteins and sugars that act as anti-freeze and lower the freezing point within their cells. 

Nature is all about return on investment, and a structure (such as a leaf) must give its owner more energy than it took to create. The small surface area of a conifer needle means it produces much less energy (food) than a broad leaf. To compensate for this, the needle lives longer – from two years in White Pine, up to a decade in White Spruce. 

In addition to a longer lifespan, conifer needles further increase their energy output by becoming active on warmer, sunny winter days. Once air temperature approaches 0C, chlorophyll can start to do its job; this means conifers can start making food long before deciduous trees have their leaves out and operational in spring. 

A broad-leaved tree has only one growing season to recoup its investment. Needles have a longer payback period; they produce less food each year but over their lifespan, productivity matches or exceeds that of a broad leaf.  This allows conifers to live in colder climates and places with shorter growing seasons and explains why you can find conifers on mountaintops and in the far north where broad-leaved trees can’t survive. 

So, two different strategies, each with its own advantages and disadvantages. Broad-leaved trees grow big leaves that produce lots of energy in a short time. But those big leaves can’t survive winter and would be liabilities to the tree during winter storms, so the tree must get rid of them and spend energy to grow new leaves every year. This annual cycle also means one year of defoliation (from insects or windstorms, for example) doesn’t usually kill the tree. 

Conifers grow small leaves that produce less energy in a growing season but are adapted to survive winter and live longer. That not only allows conifers to grow in areas broadleaved trees can’t, it also means the trees don’t have to spend energy growing a full set of new leaves each year. But it also makes conifers more vulnerable to defoliation: the premature loss of many years of investment all at once is often fatal.

Adaptations and trade-offs are all part of survival on PEI Untamed!