Wind-thrown Ironwoods: tales from a splintered land

The forest at Iroquois Heights has a unique composition and a strong diversity of plants, mammals, and birds. Forest fragmentation is a cause of this uniqueness but also makes the forest vulnerable.

The humble Hop Hornbeam's shredded bark

Traffic passes by below us in an endless, noisy, polluting stream. Where the Bruce trail runs through Hamilton, it is squeezing through the most urbanized stretch of the Niagara Escarpment ecosystem. Inevitably, the trail here includes crossing massive city infrastructure, like the section of trail that is the 403 pedestrian overpass.

We’re on our way to explore Iroquoia Heights, a patch of forest and field on the edge of the escarpment in Ancaster. It’s been in the news a fair bit over the last year or so, because of its unhealthily large deer population. The forest there is no longer connected to any other suitable deer habitat, and the Meadowlands development encroaches from the south, so the deer can’t disperse. To animals, it is an endless, impassible barrier, keeping Iroquoia Heights to the East cut off from the much larger forests to the West.

Once across the bridge, we’ve entered Iroquoia Heights. We catch the Bruce Trail heading North-East into some scrubby lands, old fields that have re-wilded into tangled groves of Hawthorn and Dogwood. These shrub lands are ideal songbird habitat. As we walk the narrow path, we move through circles of the sharp ‘chip-chip’ alarm sound of cardinals. To encourage birds here further, folks have attached birdfeeders into many trees along the trail.

The trail descends slightly and the shrubs thin out, leaving us in a flat, low meadow. Now that the ground is clear, we can see that this land lacks the characteristic hills and bowls that form in an old forest as trees uproot and logs slowly decompose. The flatness of this land means that it was likely graded and ploughed after the original forest was cut. A hawk circles slowly above, and we get down into the grasses to excitedly watch a tiny black shrew squirm between Goldenrod roots.

To the east of the meadow is a dense deciduous forest. Approaching it along the trail, we observe that its border with the meadow is quite sharp. Typically, borders between forest and meadow are gradual, with distinct edge communities of shrubs forming a buffer between the two. But here, we see a large White Pine right next to open ground. One of the uses of that buffer area is to slow down the wind, and as we step into the forest, we’re immediately struck by the very large number of downed trees within the first fifty feet.

The most astonishing thing about this forest is the odd composition of tree species. Ironwood, or Hop-Hornbeam, is by far the most dominant tree species throughout. Normally, Ironwoods are scattered sparsely throughout Oak or Maple-Beech dominated forests, but here, there are more of them than all other tree species combined. So we wonder, why is that?

We remember what we know about Ironwood: their wood is very hard and dense, and they grow very slowly. It’s likely this forest was once used as a woodlot— a source of firewood, building material, and saleable timber that is selectively logged by many generations of farmers. On this site, we find some of the largest Ironwoods we have ever seen, but usually, their small size means they are of little economic importance. As well, their  density means that they are difficult to cut down, to the point that someone doing so risks dulling or damaging their equipment.

In trying to follow the story of this land, we realize Ironwoods were the only trees that were not cut by humans during probably over a century of logging. It seems that Maples, Beech, and White Pine were selectively cut out of this forest as they reached maturity. Today, these species stand sparsely and mostly as young trees. We find several very large Red Oak, White Oak, White Ash, and the largest Black Cherry we’ve ever met, all scattered throughout, but these species likely experienced some logging as well, preventing them from dominating the forest.

So the humble Ironwood, with its flaky bark and hanging fruits, emerged to fill the canopy. The fruits are a favourite of White-tailed Deer, and are perhaps a key reason why this tiny forest has supported such a large population of them. Since it’s not connected to any other forests, there are no seeds arriving to help restore a more common balance of trees, and so this amazingly odd Hop-Hornbeam dominated forest has endured.

This forest is very unique and beautiful. Fragmentation is one of the causes of this uniqueness, but it also makes the forest vulnerable.

An herbalist friend gave us a definition of health that we use to guide our understanding of wild spaces: Health is the ability of a system to respond to stress and change. This forest seems healthy now, but it has almost no ability to respond to stress, whether that be a wind storm or a large population of hungry deer – it’s just too isolated. No amount of deer-culling, bird-feeding, or native-species-planting is going to fix that. It’s hard to say what would. To state, we can preventing further fragmentation of the wild spaces that exist today by resisting the types of mindless urban sprawl that persist on the west mountain. And by supporting projects to create wildlife corridors beneath or above highways to create space that is slightly less impossible to navigate. It’s hard to imagine solutions when this forest’s capacity for health has been damaged so.

With these thoughts in mind, we continue East through the forest, and within a few minutes it is reduced to a thin strip, at the place where the Chedoke Radial Trail and the Bruce Trail merge. We consider that this trail was once a rail line linking Hamilton to Brantford, built about one hundred years ago. Today, the rail lines are long removed, and the rich thicket we see lining the trail is what re-wilding traintrack lands can look like when left to heal for 50 years. The 403 was built about fifty years ago. What will this land look like in 50 more years?

Winter really shows off the beauty of a forest’s conifers…

One striking thing about Iroquios Heights is the few towering white pines, with their brush stroke-like branches towering above the canopy. It’s easy to estimate the age of a white pine, since these trees grow a new round of branches each year. The branch of a white pine begins to grow from deep within the heartwood of the tree’s trunk. That’s good reason to give in to your urges to climb up these towering giants! Their branches are the most secure and trustworthy, all the way up!
Hemlocks are also thriving here. These conifers can stay tiny for centuries, growing slowly in the shade of fast-growing deciduous trees and waiting for an opening in the canopy. When the tree their beneath finally falls (or in this case, was logged out), the Hemlock can shoot up quickly to giant size, finally giving its delicate branches of small, tightly packed and flat needles their turn in the sun.

Advertisements

4 responses to “Wind-thrown Ironwoods: tales from a splintered land

  1. Please see my comment at Mayday but basically it is incorrect to say the deer at Iroquoia Heights is unhealthily large or unhealthy at all for that matter. I have not only been studying the issue and the deer for some time but have attended all the meeetings and heard all the experts at the commitee meetings on the issue of the deer as well s doing my own research on deer and the ecosystem as well as looked at the patterns as well as the growing development.
    Indeed it would have been nice to see more people come forward and learn about the issue to help stop unnecessary “management”.

    • Hey Paul, thanks for taking the time to elaborate on this issue.

      We definitely agree with you that the ‘problem’ of the deer population is greatly overstated – it seems absurd for the spec and other news sources to spend so much energy blaming deer for issues that are caused by short-sighted developments.

      It seems like the issue you have is over whether or not the population of deer is unhealthily large. It is true that this is a rather subjective term. We chose to use it because of observations we have made over many years in the area. There has been an increase in browsing damage to the trunks and lower branches of trees. There is a near total absence of undergrowth in some areas, and a sharp divide between forest and field that suggests intense browsing pressure on new growth. This is consistent with what we’ve observed in Guelph and other places where populations of deer have their migration restricted by new road and housing growth. We wanted to acknowledge these signs of ill-health, but certainly we are not placing blame for the unbalance on the deer themselves. That is the differerence between what we are talking about and just parroting the rhetoric coming out of the spec. One of the reasons we wrote this article is because we have been hearing those stories about how the deer are ‘problems’, were skeptical, and wanted to see for ourselves.

      We agree with you that of course the deer population is a vital part of the forest and are playing an important role in healing that land. The problem is forest fragmentation – that is what the article is about. You wrote that deer do come and go from the area – could you tell us more about that? Where have you observed deer leaving the site, or heard about them leaving? We’d be interested in hearing any stories or experiences you have with that area, and I’m sure the other folk who read this site would be as well.

      Thanks,

      klr

  2. I’ve also heard that a predominately Hop-Hornbeam forest could indicate that a herd of cattle has grazed that area at some time in its history, as they are known to eat and injure most tree species, except the hardy Hop Hornbeams.

    • That’s so interesting! We’ve heard that about Junipers and Roses (the start of the headwaters trail in the Dundas valley is a good example of roses doing this), but not about Ironwoods. So you’re suggesting that perhaps cows from a nearby field might have also grazed in the forest? Or that perhaps parts of this forest have rewilded from cleared pasture? What are some other signs of cattle grazing that you know about?

      We’ve found other evidence of agriculture in that forest, including two lines of very large trees, with their limbs growing towards what was once open space, that probably formed borders along fence lines and now divide two areas of very different succession.

      Thanks so much for sharing your knowledge here!

What do you think? Share a story

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s