The big story of the understory

A forest is made up only of trees, right? Wrong! A forest has layers, including the understory. This stop has many examples of understory bushes, small trees and flowering plants, all critically important to the forest ecology.

The herbaceous layer of the understory may be made up of small leafy, non woody plants but these play an outsized part in the health of a forest ecosystem. They represent less than 1% of the biomass of the forest, yet can contain 90% or more of the plant species of the forest and contribute up to 20% of the foliar litter to the forest floor. —litter that is generally of higher nutrient content than that of trees. You can read this article for more detailed scientific information about this “herbaceous” layer, or understory:https://academic.oup.com/bioscience/article/57/10/845/232416

In the pine and spruce dominated forests of the northern part of the Haliburton Highlands, forests typically contain about 300 plant species. Only about 20 of those species are trees; the rest are understory plants. Typically, the large trees in the forest – the “overstory” – impact the amount of light getting to the forest floor and the nutrients that are available to the many small plants living at the feet of the trees.

You’ve maybe heard about how forests are very good at storing carbon. Would you be surprised to learn that relative to their size, the herbaceous layer does a better job storing carbon and nutrients like nitrogen and phosphorus than large trees? So next time you walk through a forest, take note of the little plants underfoot. And on your own property don’t clear your woods of so-called “brush” but learn the names of these plants and tell their stories to all who will listen.

There are quite a few understory herbaceous plants and native woody shrubs and small trees that can be viewed at this tour stop. They include:

Red Osier Dogwood (Cornus sericae)

Meadowsweet (Spiraea alba)

Highbush Cranberry (Viburnum opulus)

Elderberry (Sambuca nigra)

Black Cherry (Prunus serotina)

Ninebark (Physocarpus opulifolius)

Did you know another, mostly hidden part of healthy forests? Mushrooms! Underground, the fibers of fungi or mushrooms (which are really the fruiting bodies of fungi) form an amazing network or web. These fibers, or mycelia, have a unique connected relationship with trees, providing trees with vital nutrients. This underground connection is nicknamed the “wood wide web”. Read more about it here: https://naturecanada.ca/news/blog/wood-wide-web/ . What can you do to support this? Provide fungi with the food they need and leave fallen logs, branches and leaves on the forest floor to slowly be broken down by fungi.

If you’re out walking during the fall, you may see the distinctive white silk webbing of the Fall Webworm (Hyphantria cunea). At this stop they’ve created a nest at the furthest reach on the cherry tree branch extending over the water. Fall Webworms are unusual in that they build their webbed nests in the fall; they are often confused with Tent Caterpillars, who build their webbed nests at the crotch of branches in the spring. Since they emerge late in the growing season, Fall Webworms will rarely kill a tree by skeletonizing it. The fall webworm is a moth caterpillar native to southern Ontario and the United States.

As unsightly as they are, populations of Fall Webworms will be kept under control by ladybugs and beetles like our native Twelve-spotted Lady Beetles (Coleomegilla maculata), as well as by ants, spiders, wasps and birds.

The Haliburton Master Gardeners “Guide to Native Plants” has a full listing of native shrubs and other shade loving woodland plants that are part of a healthy, diverse forest ecosystem. The understory plants also serve as food and shelter for forest creatures and pollinating insects.

U-Links Species Profile:

Fall Webworm, Hyphantria cunea

While you walk along the river, there is a slight chance that you may collect a hitchhiker when you wander under a tree. A tiny fuzzy worm may have created a silk thread to propel itself down towards your shoulder if there is enough rustling of the top tree leaves. They however, are harmless to you and are only in search of food or hiding from predators.

The fall webworm is a native moth caterpillar that ranges all around southern Ontario and the United States, and has since spread to Europe and Asia (Edosa et al., 2018). These small worms are uncommon for their interesting caterpillar (larval) phase, which occurs around the fall season. As previously mentioned, it can be confused with the Tent caterpillar, however a distinction between the two of them is where they set up their ‘tents’, as the tent caterpillar will spin its silk at the connecting point of the large branches and the tree trunk, whereas the fall webworm will spin its silk webs at the ends of branches (Showalter & Ring, 2017). Even though the fall webworm has a large appetite and can skeletonize the branches and leaves that they consume (Edosa et al., 2018), the location of their silk casings as well as the season in which they are active, their destructive feeding habits do not cause major damage or losses to their host plant. They can however leave the plant more susceptible to damage from other trees if there are a large number of webworms at a specific site.

The morphology (physical makeup) of the fall webworm will change slightly as they grow. They begin their life cycle as tiny greenish yellowish worms with tufts of patchy hair along their bodies. The fall webworm will spin its web and gorge on leaves and fruits, growing and changing from its original colour to a darker grey pattern (Showalter & Ring, 2017). Their heads will change from a black colour to a reddish colour prior to going into its pupa phase, cocooning itself until it develops into a full grown moth (Showalter & Ring, 2017). They will then change into a vibrant white moth that will roam around at night looking for mates (Edosa et al., 2018).

Researcher: Caleb Brown, Trent University