What role do dead trees have in the ecosystem?

2024-08-28T17:15:13+00:00

In urban and wild environments, living trees play an essential part in sustain a healthy ecosystem. We rely on trees to maintain our water supply, clean our air, and provide a safe habitat. These benefits are well-known among all tree lovers and they’re a big part of why we’re so passionate about bringing trees to communities across Utah. Did you know the benefits of trees extend past their living years? Dead trees (snags) and downed logs continue to be an important resource for wildlife.

Whether they’re upright or toppled, dead trees continue to play a role in the cycle of life in the ecosystems in which they’re situated. It’s estimated that up to two thirds of all wildlife species rely on downed trees for some aspect of their life cycle. The decaying surface of a snag acts as a growth substrate for many species of fungus, moss, and lichen. Moths, worms, beetles, and snails use spaces under the bark as shelter or a place for foraging. Birds enjoy these hotspots of small invertebrates as a reliable source for food. Primary cavity nesters, such as woodpeckers, prefer the softwood of snags for nesting and secondary cavity nesters use these abandoned holes for their own nests in the next season. These cavities also serve as dens and food storage for small mammals, like squirrels or even bats.

In addition to their benefit as a primary resource for living creatures, dead trees contribute to the cycle of life by cycling nutrients back into the soil. Decomposers, like fungi and snails, help break down the snags as they decay. As the organic matter breaks down into its component parts, it releases nutrients such as nitrogen, potassium, and phosphorus into the soil that go on to nourish plants and other organisms in the ecosystem, including saplings. In effect, these dead trees act as mulch for a growing forest.

Dead trees also continue to play an essential part in helping us fight climate change. Even after a tree dies, the carbon dioxide absorbed while it was living remains trapped in its wood. Dead wood accounts for up to 50% of the carbon currently stored in forests. Their slow, natural decay means this carbon will remain sequestered for years, cycling through the ecosystem at a manageable pace and ensuring the ecosystem remains stable.

While we’re certainly not going to be going out to the forest to create more snags (planting new trees is more fun and makes way more sense), we feel it’s important to take a moment to appreciate the beauty of trees in all stages of their life. As little saplings, as towering giants, and as eroding snags, trees play an incredible role in our ecosystem.

Want to help us create a strong ecosystem? Join us at our tree planting events this Fall!

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Why don't all trees shed their leaves?

2022-10-13T09:00:00+00:00

When Fall rolls around, many trees begin to change colors and eventually drop their leaves in a process called shedding, a topic we explored in last week’s blog post. This week, we’ll be learning about the trees that keep their leaves, both evergreens and the deciduous trees experiencing marcescence.

Marcescence is the phenomenon of plants retaining plant organs that are usually shed, sometimes referring to mushrooms that dry out and later revive, but most commonly used to refer to trees with leaves that change colors but do not drop until outside forces (like wind) remove them from their branches. Trees that experience marcescence are sometimes called “everciduous.” This group of trees includes species of oak and beech. In fact, all oaks display foliage marcescence for at least a portion of their lives, only becoming truly deciduous after reaching their full maturity. The evolutionary advantage of marcescence is not fully understood, but there are two main theories among many. The first being that retaining the leaves will help protect new leaf buds from winter desiccation. The second is that the leaves dropping later in the winter season or even in early spring provide the tree with a delayed source of moisture-preserving mulch, allowing the tree to take full advantage of the snowmelt.

Perhaps more famous than the “everciduous” trees are the evergreens, a group that includes pines, cedars, hemlocks, and spruces. These trees keep their green leaves (called needles) all year long. Instead of shutting down the production of chlorophyll in the winter months, many evergreens continue to produce and benefit from the chemical, one of the necessary ingredients for photosynthesis. With the energy they produce throughout the winter through photosynthesis, evergreens are able to maintain their needles, which allows them to return to full-capacity energy production immediately when spring rolls around. However, some evergreens do cease photosynthesis during the winter months. These evergreens are usually found at higher altitudes, where the soil isn’t as rich in nutrients. The needles of evergreens are able to store vast quantities of nutrients the trees need to survive. These nutrients are typically already scarce in soils at higher altitudes and even harder to access during the winter months due to the cold temperatures. During this time, evergreens are able to use the nutrients stored in their needled to compensate for the lack of nutrients available in the soil around them. The needle-shaped leaves of conifers also help the tree retain water throughout the season by producing a chemical called cutin, a wax-like substance that traps fluids in the needles and protects them from damage. The needles also produce proteins that act like antifreeze by binding to ice crystals, inhibiting their growth and preventing ice damage. These adaptations are also what allow conifers to succeed in drier climates, like Utah. The cutin they produce to retain water works in cold and hot months, lending itself to the trees’ survival all throughout the year.

There are evolutionary advantages in keeping leaves or in dropping them and the evolutionary pathways of tree species depend on the climate in which they find themselves. Deciduous trees found themselves in situations where it was more appropriate to shed their leaves and wait winters out in a dormant state while evergreens found a different way to pass their winters by. Both are marvelous examples of the natural world at work!

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What role do dead trees have in the ecosystem?

Why don't all trees shed their leaves?