Southern Ontario’s Ecoregions in Slow Motion: An Eight-Year Journey Along the Bruce Trail

Guest post by Daniel Stuart, MEnvSc Candidate in the Department of Physical & Environmental Science at the University of Toronto-Scarborough

During the final year of my undergraduate program the idea of hiking all 900-or-so kilometres of the Bruce Trail somehow lodged itself in my head. It was 2010 and I was twenty-one years old, immersed in the idealism of that age and on the doorstep of a career as an ecologist. At the time hiking from Queenston Heights along the Niagara River to the town of Tobermory at the northern tip of the Bruce Peninsula (Figure 1.) seemed an appropriate way to gain a more meaningful appreciation of my home province’s landscape. This would turn out to be true in part, but little did I know that the more valuable takeaway would be a practical education in the transitional ecosystems that define Southern Ontario’s landscape. For those without the time to hike it themselves, take a tour with me along the trail from south to north exploring its subtle but undeniable ecological shifts.

Figure 1: Bruce Trail Map (Bruce Trail Conservancy, 2020

As life sometimes goes, it was another two years before I finally purchased the Bruce Trail Reference guidebook and embarked on my first sojourn, a three day hike that would take me from the southern terminus of the trail at Queenston Heights back to Hamilton where I lived at the time. I hopped on a free shuttle bus heading for a casino in Niagara Falls and upon arriving was accosted by the bus driver when he spotted my backpack and water jug, realizing I had no intention of gambling that day.  It was September 2, 2012 and the first miles of the trail were peppered with sightings of uncommon shrubs and trees like Bladdernut (Staphylea trifolia), Sassafras (Sassafras albidum), Spicebush (Lindera benzoin), Pignut Hickory (Carya glabra), and Hill’s Oak (Quercus ellipsoidalis), many of which display full fruit in the late summer. These shrubs and trees share a common trait: in Canada they are confined to the Carolinan Ecoregion.

The Carolinan Ecoregion (defined as Ecoregion 7E in Ontario; Figure 2.) occupies the southernmost portions of Ontario, extending from the shores of Lake Erie to approximately Grand Bend in the west, London, Hamilton, and Toronto in the east. Named for the forests typical of the Atlantic Coast from Long Island to Georgia, this region is dominated by a large variety of deciduous (or, leafy) trees including those listed above that fail to thrive in cooler climates to the north or west (Colthurst & Waldron, 1993). In the Niagara Region the sheltering cliffs and slopes of the Niagara Escarpment offer a slightly warmer microclimate that encourages the region to “punch above its weight” in terms of plant diversity.

Figure 2: Ecoregions of Ontario (Crins et al., 2009)

My first journey from the Niagara River ended in utter failure when with painfully blistered soles, just 26 kilometres into my expedition I swallowed my pride and called a friend to pick me up at the Brock University campus in St. Catharines. I would eventually work up to 30- and even 40-kilometre days, but this would take years of training and a good deal of re-conditioning every spring to tighten up my legs that would seemingly turn to jelly each winter.

The “southern feel” of the Bruce Trail gradually diminishes as one hikes westward toward Hamilton, the conspicuously common open-grown oaks (Quercus spp.) gently replaced by the familiar Sugar Maple (Acer saccharum)-dominant woodlands that emblemize Canada. The extensive forested tracts of the Dundas Valley offer the final display of southern species before mounting the escarpment where suddenly one stands firmly in the Great Lakes-St. Lawrence Ecoregion (defined as Ecoregion 6E in Ontario; Figure 2.).  The abruptness of the transition surprised me. I recall spotting the northernmost stand of a southern tree, a population of Chinquapin Oak (Quercus muehlenbergii) perched below the escarpment brow next to Sydenham Road in Dundas. Although I understand that southern species are occasionally found north of the official boundaries of the Carolinian Ecoregion, along the Bruce Trail I encountered no other Carolinian-specialist plant. The sheltered valleys of the Hamilton area seem to provide a last bastion for southern plants that struggle to tolerate the exposed landscape above Burlington and beyond.

From the Burlington heights the Great Lakes-St. Lawrence forest extends northward all the way to the edge of the Canadian Shield, which itself transitions into the seemingly endless Boreal forest that blankets the northern part of our continent. Unlike the Carolinian region which comprises mostly deciduous trees, or the Boreal region which compromises mostly coniferous trees, the Great Lakes-St. Lawrence forest is a roughly equal mix of the two. This forest type features strong representation from leafy trees like Sugar Maple (Acer saccharum), American Beech (Fagus americana), and Black Cherry (Prunus serotina) along with their needled counterparts like Eastern White Pine (Pinus strobus), Eastern White Cedar (Thuja occidentalis), and Eastern Hemlock (Tsuga canadensis).

I hiked the central stretches of the Bruce Trail at a slower rate between 2014 and 2018, a section that traverses a hilly complex of woodlots, river valleys, and bucolic landscapes. I came across a Striped Maple (Acer pensylvanica) in the Caledon area and a small Jack Pine (Pinus banksiana) stand on a north-facing slope near the Hockley Valley, both typically northern trees. My first Northern Holly Fern (Polystichum lonchitis) was observed in Noisy River Provincial Park near the village of Creemore, a plant that in places coated the trailside by the time I reached Owen Sound. Similarly, I spotted a tiny American Hart’s Tongue Fern (Asplenium scolopendrium var. americanum) in the Beaver Valley, a globally uncommon species whose core range is concentrated around Owen Sound and the lower reaches of the Bruce Peninsula.

By May of 2019 I was hiking in earnest, setting aside many weekends to cover the approximately 210 kilometres from the west edge of the Beaver Valley near Kimberley, through Owen Sound and to the base of the Bruce Peninsula near Wiarton. The birding that spring was glorious, and I often hiked with binoculars somewhat annoyingly tugging against my neck. In the Beaver Valley I observed my first ever Louisiana Waterthrush (Parkesia motacilla) along the rushing banks of Bill’s Creek. A Philadelphia Vireo (Vireo philadelphicus) flitted between branches in a woodlot near Walter’s Falls, a Golden-winged Warbler (Vermivora chrysoptera) was spotted within a thicket at the Bighead River Overnight Rest Area, and a Green Heron (Butorides virescens) squawked at me near the Bognor Marsh.

In early September 2019 I began the big push up the Bruce Peninsula toward Tobermory, in a four-day period that would take me from the town of Wiarton to Crane Lake Road just before the southeast boundary of Bruce Peninsula National Park. Logistics were more complicated now and I was forced to consider packing lightweight provisions that were adequate but could still be carried on my back. There were also safety considerations specific to the Bruce Peninsula, like establishing a check-in system where cell reception was poor, and to keep aware of Black Bear (Ursus americanus) and the docile but not entirely unthreatening Massasauga (Sistrurus catenatus), Ontario’s only venomous snake. Bear scat was an intermittent sight along the length of the peninsula, first observed just 14 kilometres past Wiarton along Malcolm Bluff.

Although forests remained of mixed composition typical of the Great Lakes-St. Lawrence region, cool northern exposures and thin-soiled areas took on a palpable “northern feel”, often dense with Eastern White Cedar (Thuja occidentalis), pine (Pinus spp.) and Eastern Hemlock (Tsuga canadensis). Wind-beaten crags offered habitat for abundant Bearberry (Arctostaphylos uva-ursi), a northern species yet unseen on my journey so far, and Rattlesnake Plantains (Goodyera spp.) became commonplace. By the time I reached the edge of the National Park the Boreal woods felt much closer.

Sadly, poor weather and low spirits cut my hike short in September, with soggy feet and an approaching storm promising to result in a miserable finale. Despite this setback my goal to finish the Bruce Trail remains firm. At this moment I have booked a campsite in the National Park this May 2020 and (barring any disasters) myself, along with three companions, will finish the final 40 kilometres toward the trail’s northern terminus.

To walk the Bruce Trail is to walk a cross-section of Southern Ontario. For me it has offered an education in landscape ecology earned by traversing it first-hand. It has been a limit-testing and a character-building experience. Although I now hike with a different outlook than my 21-year-old self, I must credit him with having the guts to recognize the journey’s value and for accepting its challenge.

References

Bruce Trail Conservancy. 2020. Explore the Trail. Bruce Trail Conservancy. <https://brucetrail.org//trail-sections>. Retrieved 13 February 2020.

Colthurst, K., Waldron, G. 2013. “What is a Carolinian Forest?”. Essex Region Conservation Authority. Carolinian Canada. <https://caroliniancanada.ca/legacy/SpeciesHabitats_Forests.htm>. Retrieved 13 February 2020.

Crins, William J., Paul A. Gray, Peter W.C. Uhlig, and Monique C. Wester. 2009. The Ecosystems of Ontario, Part I: Ecozones and Ecoregions. Ontario Ministry of Natural Resources, Peterborough Ontario, Inventory, Monitoring and Assessment, SIB TER IMA TR- 01, 71pp.

When do descriptive methods exceed the sum of their points?

The last post here mused on the connection between (but also, distinctness of) the scientific goals of "understanding" and "prediction". An additional goal of science is "description", the attempt to define and classify phenomenon. Much as understanding and prediction are distinct but interconnected, it can be difficult to separate research activities between description and understanding. Descriptive research is frequently considered preliminary or incomplete on its own, meant to be an initial step prior to further analysis. (On the other hand, the decline of more descriptive approaches such as natural history is often bemoaned). With that in mind, it was interesting to see several recent papers in high-impact journals that rely primarily on descriptive methods (especially ordinations) to provide generalizations. It's fairly uncommon to see ordination plots as the key figure in journals like Nature or The American Naturalist, and it opens up the question of 'when do descriptive methods exceed description and provide new insights & understanding?'

For example, Diaz et al.'s 2016 Nature paper took advantage of a massive database of trait data (from ~46000 species) to explore the inter-relationships between 6 ecologically relevant plant traits. The resulting PCA plot (figure below) illustrates, across many species, that well-known tradeoffs between a) organ size and scaling and b) the tissue economic spectrum appear fairly universal. Variation in plant form and function may be huge, but the Diaz et al. ordination highlights that it still is relatively constrained, and that many strategies (trait combinations) are apparently untenable.

From Diaz et al. 2016.

Similarly, a new paper in The American Naturalist relies on ordination methods  to try to identify 'a periodic table of niches' of lizards (Winemiller et al. 2015 first presented this idea) – i.e. a classification framework capturing the minimal, clarifying set of universal positions taken by a set of taxa. Using the data and expert knowledge on lizard species collected over a lifetime of research by E. Pianka and L. Vitt, Pianka et al. (2017) first determine the most important life history axes -- habitat, diet, life history, metabolism, and defense attributes. They use PCoA to calculate the position of each of 134 species in terms of each of the 5 life history axes, and then combined the separate axes into a single ordination (see figure below). This ordination highlights that niche convergence (distant relatives occupy very similar niche space) and niche conservation (close relatives occupy very similar niche space) are both common outcomes of evolution. (For more discussion, this piece from Jonathon Losos is a great). Their results are less clarifying than those in Diaz et al. (2016): a key reason may simply be the smaller size of Pianka et al.'s data set and its greater reliance on descriptive (rather than quantitative) traits.

From Winemiller et al. 2017

Finally, a new TREE paper from Daru et al. (In press) attempts to identify some of the processes underlying the formation of regional assemblages (what they call phylogenetic regionalization, e.g. distinct phylogenetically delimited biogeographic units). They similarly rely on ordinations to take measurements of phylogenetic turnover and then identify clusters of phylogenetically similar sites. Daru et al.'s paper is slightly different, in that rather than presenting insights from descriptive methods, it provides a descriptive method that they feel will lead to such insights.

Part of this blip of descriptive results and methods may be related to a general return to the concept of multidimensional or hypervolume niche (e.g. 1, 2). Models are much more difficult in this context and so description is a reasonable starting point. In addition, the most useful descriptive approaches are like those seen here - where new data or a lot of data (or new techniques that can transform existing data) - are available. In these cases, they provide a route to identifying generalization. (This also leads to an interesting question – are these kind of analyses simply brute force solutions to generalization? Or do descriptive results sometimes exceed the sum of their individual data points?)

References:

Díaz S, Kattge J, Cornelissen JH, Wright IJ, Lavorel S, Dray S, Reu B, Kleyer M, Wirth C, Prentice IC, Garnier E. (2016). The global spectrum of plant form and function. Nature. 529(7585):167.

Eric R. Pianka, Laurie J. Vitt, Nicolás Pelegrin, Daniel B. Fitzgerald, and Kirk O.Winemiller. (2017). Toward a Periodic Table of Niches, or Exploring the Lizard Niche Hypervolume. The American Naturalist. https://doi.org/10.1086/693781

Barnabas H. Daru, Tammy L. Elliott,  Daniel S. Park, T. Jonathan Davies. (In press). Understanding the Processes Underpinning Patterns of Phylogenetic Regionalization. TREE. DOI: http://dx.doi.org/10.1016/j.tree.2017.08.013

Has science lost touch with natural history, and other links

A few interesting links, especially about the dangers of when one aspect of science, data analysis, or knowledge receives inordinate focus.

A new article in Bioscience repeats the fear that natural history is losing its place in science, and that natural history's contributions to science have been devalued. "Natural history's place in science and society" makes some good points as to the many contributions that natural history has made to science, and it is fairly clear that natural history is given less and less value within academia. As always though, the issue is finding a ways to value useful natural history contributions (museum and herbarium collections, Genbank contributions, expeditions, citizen science) in a time of limited funds and (over)emphasis on the publication treadmill. Nature offers its take here, as well.

An interesting opinion piece on how the obsession with quantification and statistics can go too far, particularly in the absence of careful interpretation. "Can empiricism go too far?"

And similarly, does Big Data have big problems? Though focused on applications for the social sciences, there are some interesting points about the space between "social scientists who aren’t computationally talented and computer scientists who aren’t social-scientifically talented", and again, the need for careful interpretation. "Big data, big problems?"

Finally, a fascinating suggestion about how communication styles vary globally. Given the global academic society we exist in, it seems like this could come in handy. The Canadian one seems pretty accurate, anyways. "These Diagrams Reveal How To Negotiate With People Around The World." 

Documenting the sacrifice

Whether working in remote regions or with poisonous animals, biologists often put themselves in peril in the name of discovery. The first organized expeditions of naturalists sailed to exotic lands, their bravery supplemented by their curiosity, were threatened by storms while at sea, new and deadly diseases, unfamiliar animals, and new cultures. Add plane crashes and paramilitary groups to this list and not much has changed.

In a great New York Times piece titled 'Dying for Discovery', Richard Conniff recounts several stories of naturalists, ecologists and conservation biologists killed while pursuing their passion for discovery. But just how many field biologists have died while working to understand life's secrets? This is an interesting question, and begs the further question, are they adequately memorialized?

Gary Polis (1946-2000) desert ecologist, drown with four other biologists during a storm in the Sea of Cortez.

In an attempt to tell the stories of the fallen naturalists, Conniff hosts an interactive list, called the Wall of the Dead, which lists all biologists killed in the field and that he has a record of. People are able to add names, and I've visited this list several times over the past month and it has grown substantially. I've known a few field biologists that have died -and added one to the list, and know several that survived near-death experiences, and this list is a great and important monument to their memories.