Submitted by blazej on Sat, 11/10/2018 - 12:58

ON READING MY fellow Canadian Todd Boland’s article about the serpentine barrens of the Northern Labrador Peninsula of Eastern Canada (RGQ, summer 2015), I felt compelled to echo his article by enlightening the readership about a special plant-rock association that occurs at the other end of Canada, on its wild and wet west coast: the alpine, limestone plateaus of Vancouver Island.

Vancouver Island is the largest island on the west coast of North America. With a length of 286 miles (460 km) and width of 62 miles (100 km) at its widest point, it is an ecologically diverse and special place. With a relatively small population of 750,000, the island is mostly an uninhabited wilderness, save for some remote native communities and isolated fishing villages. Most islanders are crammed into the small coastal plain that runs down the south-east coast, a tiny fraction of the island’s area. Here on the plain, in the rain shadow of the Pacific Insular Mountains, the Garry oaks (Quercus garryana) and camas (Camassia quamash/C. leichtlinii) grow in what is the northernmost extension of the Mediterranean rain shadow climate that reaches all the way down to central California. We even have large areas of hairy manzanita (Arctostaphyllos columbiana), another plant whose range extends half the length of California. By contrast, out on the west coast of the island, the temperate rainforests reach their peak of grandeur, as the highest precipitation rates in North America produce some of the biggest trees on the planet. These forests of Douglas fir (Pseudotsuga menziesii), Sitka spruce (Picea sitchensis), and western red cedar (Thuja plicata), growing on rich alluvial floodplains, rival the great trees of California in size and splendor. Between these two vastly different ecosystems rise our mountains, known as the Vancouver Island Ranges.

Reaching a height of 7200 feet (2200 m), our mountains are not exceptionally high. However, due to the immense snowpack resulting from the high winter precipitation levels, our subalpine zone starts at just 4500 feet (1400 m), and the alpine tundra starts at around 5000 feet (1500 m) Here, snow can linger well into mid-August, creating true alpine conditions and giving the plants only a very short window to do their thing. Very few roads penetrate this wilderness, and virtually none of it is ever seen, even by most locals. The only way to experience the alpine meadows, pocket glaciers, and turquoise lakes is to walk in, which in itself poses some problems. Solid wilderness skills are crucial here because once you’re in, you’re on your own, with no cell phone reception, no roads, and no people to rely on. Perhaps what’s best about Vancouver Island is how easily one can find solitude. Most islanders don’t venture into our rugged backcountry. In fact, since very few paved roads cross the island, most locals don’t even know what’s in there! Being an island with no bridge to the multitudes of the lower mainland, finding your own piece of remote wilderness is relatively easy. 

Geologically, Vancouver Island is part of the outer coastal insular ranges. These mountains were created 100 million years ago as the North American plate collided with the terranes of western North America, folding and thrusting upwards to form these mountains, as well as the Olympic ranges to the south and Haida Gwaii to the north. Existing in the “ring of fire,” most of the island’s rocks are volcanic in origin. These hard rocks limit the diversity of plant growth and result in the most common Vancouver Island alpine vegetation regime: the subalpine heath. These landscapes are dominated by ericaceous shrubs such as pink and white alpine heather (Phyllodoce empetriformis and Cassiope mertensiana), and white-flowered rhododendron (R. albiflorum), with sporadic groves of twisted mountain hemlock (Tsuga mertensiana) and subalpine fir (Abies lasiocarpa). Although these areas have a rugged charm of their own, the flower displays are, generally speaking, not overwhelming. The lower pH soils and poor drainage of this ericaceous landscape tend to limit the floral diversity and, with some exceptions, these are not great places to botanize. Glaciation has also played a role in limiting the flora. Mountain areas to the south, even as close as the Olympic Mountains (which mostly escaped the advancing ice) often have richer floras. Despite this, you can find some interesting treasures such as white-flowered penstemon (P. davidsonii subsp. menziesii f. albus) and Arctic species such as alpine azalea (Kalmia procumbens) in the sub-alpine heath. Stepping off the volcanic rock and onto the limestone, however, changes everything. Except where karst processes are extreme and have left no substrate, the floral displays become spectacular.

Only about 4% of Vancouver Island is composed of limestone, but the influence of high coastal precipitation levels on the soft carbonate rock results in a diverse karst landscape characterized by caves and underground streams, sinkholes, arches, fossils, and all the other typical karst landforms. Due to the dense forest cover, most of Vancouver Island’s limestone is difficult to see, save the occasional outcrop or cave entrance. However, in a few places, these limestones have been thrust up into the alpine zone above 5000 feet (1500 m), leaving exposed alpine epikarsts. These high alpine occurrences are not huge, ranging in size from 470 acres (190 hectares) on the Clayoquot Plateau to small outcrops of just a few hectares. Some areas are flat and some are super-steep, but they all contribute to plant diversity. All are covered in snow for most of the year and host a distinct and varied flora. Not all limestones are created equal, though all originate on the shallow ancient sea floor and are composed of marine organisms such as corals and seashells. Some are soft, such as dolomite; while others, like marble, become much harder due to heat and pressure. Vancouver Island’s limestones are all referred to as the Quatsino formation, and though dolomite is absent here, a range of consistencies exist.

 Stepping off the dark volcanic rock onto the white-grey of the limestones, one is instantly struck by how the limestones host significantly richer plant communities. Why is this? The simple answer would be that these lime-loving species have evolved over millennia to thrive in the higher pH soils of the dissolved limestone. Scientists are just starting to discover the secrets of limestone-plant associations. On Vancouver Island, a unique association exists between karst and the lowland coastal temperate rainforests. Coastal forest karst ecosystems are more productive than similar forest sites on non-karst terrain. The reason for the increased productivity on karst ecosystems is the nutrient cycling associated with the carbonate bedrock. As this rock is dissolved by the generally acidic rain, it releases calcium carbonate (CaCO3), carbon dioxide, (CO2) and mineral micronutrients into the soil, encouraging better plant development and growth. 

Another reason why the plants seem to grow better in these alpine karst environments is the ability of the limestone to buffer pH levels. The rain that falls over these alpine limestone areas is on the acidic side to begin with (pH 5.6), but the limestone acts as a buffer, allowing a flora that can flourish in higher pH soils (pH 6.5) rich in calcium and magnesium. Rock gardeners take note! Drainage is also a factor. So many of the plants we love to grow require perfect drainage, and these limestone plateaus, with their sinkholes, fissures and caves, offer no chance for water to pool and settle. This is in stark contrast to the volcanic areas which are riddled with alpine tarns and mountain streams. For the traveler, this poses a problem as drinking water is almost impossible to find, and one must typically melt snow to quench one’s thirst.

 Descriptions of how limestones influence plant life, a very old topic among European botanists, started late on Vancouver Island. For instance, an early botanical expedition on these alpine areas didn’t happen until 1984 when a team of government botanists flew onto the Clayoquot Plateau near Tofino to gather data needed to propose an ecological reserve (eventually, the area became an undeveloped provincial park). The team spent two nights camping on the plateau and expanding the species list for the island, discovering previously unknown disjunct populations and range extensions of many alpine plants. That this happened as recently as 1984 reflects how unknown and how rarely visited these areas are. As mentioned above, the plateaus are very difficult to access especially given that many of the areas are found within the boundaries of the large, rugged, and relatively trail-less (given the park’s size) Strathcona Park. Here, fly-ins are not allowed, which limits these areas to only those who are extremely fit and able to carry a heavy pack for multiple days. Carrying a crammed pack also limits plant specimen collecting, the documentation on which current plant knowledge is based. As none of these areas have access trails, steep and epic bushwhacks are the order of the day. Add to that the heat of doing this in the summer (when the flowers are blooming) and the dreaded hordes of mosquitoes, plus no water for drinking or lakes to swim in. Only those with an iron constitution should venture here. Once through the shroud of thick bush that guards these alpine areas, other issues come into play. Travel over the limestone involves navigating the often sharp and steep rocks that we call the limestone cheese grater, more than capable of ripping you to shreds if you were to fall. The high precipitation rates have eroded these soft limestones into incredibly sharp knife blades that test the durability of all but the best hiking boots. On top of this, falling into one of the huge sinkholes that riddle some of the plateaus is always a possibility. From a distance, the plateaus resemble moonscapes in many places, but on closer inspection, there is much here to offer the rock gardener and wildflower hunter. 

Alpine plant enthusiasts will find a plethora of plants here. Many of these are restricted to the limestones, which makes them rare on Vancouver Island. These would be considered disjunct populations, separated geographically from the main range of the species distribution. My early days of mountain botanizing on Vancouver Island led me to believe that these plants were rare everywhere. However, having traveled and explored off-island in recent years, I have found that many of our rare plants are common on the mainland ranges such as the Cascades and Rockies.  Of course, this is due to the fact that we live on an island, where plant populations are generally poorer. I reflected on this in Calgary this past summer when I saw cutleaf anemone (Anemone multifida) in a natural area of a city park. This plant requires a minimum of two days’ hard travel to see on Vancouver Island! Moss campion (Silene acaulis), a circumpolar species, is abundant on the limestones and more showy than on the adjacent igneous rocks. It can make huge, ancient buns, entirely covered with bright pink flowers pressed tight against the foliage. Saxifrages are well represented here, with at least 10 species including a new record for the island, wedge-leaf saxifrage (Saxifraga adscendens), found just this past summer. One saxifrage of note is the purple mountain saxifrage, (Saxifraga oppositifolia), another circumpolar species. Many cultivars and wild selections of this plant are grown by rock gardeners, but I’ve never seen this plant growing as tightly as here on the west coast. The buns are as hard as rocks, with the rosettes packed much tighter than any cultivated form I’ve seen. Sadly, I’ve never seen it flowering on the island, as it blooms very early. Getting to them this early would involve not only the above-mentioned hardships, but also camping and traveling in winter conditions to access the vertical, snow-free rock faces where this species grows. Spreading phlox (Phlox diffusa) is the only phlox to be found here, but of interest to gardeners is the diversity of color forms that may be found, from deep purple to pure white and all variations in between. Arctic aster (Eurybia siberica) makes an appearance here too. This plant was well separated from its main range, which extends all the way to the Arctic, as the common name implies. Another rarity for the island is mountain death camas (Anticlea elegans), another disjunct population which also looks different from mainland forms with larger flowers and greener leaves. Yellow mountain avens (Dryas drummondii), while common in the interior ranges, is also disjunct here and never forms the great mats seen in the Rockies. Thus a real treat whenever one stumbles across its tiny nodding yellow blooms. Western sweetvetch (Hedysarum occidentale) of the pea family, with pink-purple flowers, is another species with disjunct distribution. The yellow-flowered cascade wallflower (Erysimum arenicola) also occurs here, though not exclusively on limestone. 

Among some of the more common ferns such as maidenhair fern (Adiantum aleuticum) and lady fern (Athyrium alpestre var. americanum), two other interesting ferns occur here: green spleenwort (Asplenium viride), a hairless spleenwort with green leafstalks and only found on limestone on Vancouver Island; and the curiously named sinful spleenwort (Asplenium adulterinum). This small fern, while extremely rare in North America, is also found in Europe (disjunct indeed!), and is believed to have evolved as a hybrid between the non-limestone species Asplenium trichomanes and the above mentioned A. viride.  

Shrubs are poorly represented here, but Arctic willow (Salix arctica) can be abundant, forming ground-hugging mats that conform to the shape of the very rocks over which they’re growing. The plateaus also host a variety of western species, not always associated with limestone. Some of these include the field locoweed (Oxytropis campestris), a large-flowered, showy form of tufted saxifrage (Saxifraga cespitosa), subalpine daisy (Erigeron glacialis), pussytoes (Antennaria spp.), louseworts (Pedicularis spp.), Sitka mistmaiden (Romanzoffia sitchensis), silky phacelia (Phacelia sericea), scarlet paintbrush (Castilleja miniata), subalpine buttercup (Ranunculus eschscholtzii), and common harebell (Campanula rotundifolia). Also occurring here is the smallest dandelion you’ll ever see (Taraxacum cf. ceratophorum). This is just a small sampling of the diverse flora encountered on these plateaus. 

In the past few years, my friends and I have been exploring these remote areas in the hopes of discovering special things. While we haven’t found any “new” plants, there certainly have been some surprises and adventures. Perhaps the best part of traveling here is that we get to immerse ourselves in a unique and beautiful alpine landscape that few people ever see.