Report for the Halifax Field Naturalist, Fall 2012 Issue|
Writer's Final Draft
Sept. 14, 2012
A Tail of Two TrailsPCCL's Flora and Fauna Saturday, Aug. 18
Sun & cloud, approx 24 degrees
Leaders: Alice Morgan (NSNT) & David Patriquin (HFN)
Colpitt Lake Back Country Saturday, Aug. 25
Sun & cloud, approx 25 degrees
Leader: Burkhard Plache
Report by David Patriquin
On successive weekends in August, HFN walks took us over two trails into "The Backlands" on the Halifax south mainland. This large block of undeveloped land lies between Williams Lake Road and Powers Pond (near Herring Cove) 6 km to the SE and is bounded by Purcell's and Herring Cove Roads to the NE and SW. Approximately 16 km2 in area, it is rough, glacial terrain of mostly exposed bedrock with the dark Meguma rocks prominent near Williams Lake, and granitic rock over the remainder. There are only pockets of alluvial and lacustrine deposits or till, but till cover is extensive towards Herring Cove. Macintosh Run flows across part of it. Although commonly described as "undeveloped land", it is better described as a wilderness: there are no roads across it, (currently, only a few residential streets penetrate at the margins) and exotic species are rare in the vegetation. A relatively short walk into the area leaves the sounds of urban life behind. Unless one of the few well marked trails is followed, hikers may have to do some bushwhacking.
On Aug. 12th, we followed Alice Morgan of the Nova Scotia Nature Trust (NSNT) over a trail that traverses the only formally protected land in The Backlands: the Purcell's Cove Conservation Lands. They occupy a long strip, approx 260 m wide, extending from Purcell's Cove Road, over Purcell's Pond to Flat Lake, approximately 1.4 km inland. They were donated to the Nova Scotia Nature Trust (NSNT) by members of the Field and Napier families in 2003 and 2009 respectively. HFN contributed towards initial legal costs and conducts an annual species inventory of the properties for the NSNT.
The trail crosses land outside of the PCCL initially, entering the PCCL near Purcell's Pond. In the past, our annual species inventory covered species encountered over the entire trail. This year, we restricted the inventory to the portion of the trail that lies only within the PCCL. Further, we documented species in burnt and unburnt areas separately. The "Spryfield Fire" of 2009, moved from beyond Flat Lake towards Purcell's Pond, stopping at a large wetland between the two lakes. Mostly what burned were barrens with Jack Pine and ericaceous bushes and some mixed forest (mainly black spruce, red maple, birch and big tooth aspen) on shallow soil over granitic bedrock. This landscape dries quickly and so is prone to recurrent fires. HFNers have watched with interest the recovery of vegetation at this and other barrens sites after the 2009 fire.
In our 2012 inventory, 30 species of vascular plants were observed only in the unburnt sections of the trail, 10 only in burnt sections, while 21 occurred in both sections. Of the ten species observed only in burnt sections, Bristly Sarsparilla is typically a transient, early successional, post-disturbance species and could well be restricted to the burnt sections; possibly the same is true for Pinweed. It is likely that the others occur also in unburnt areas. Many of the total of 31 species observed in the burnt sections are in some way adapted to fire, e.g. the Jack Pine, whose cones require high temperatures to open; Black Huckleberry, which sprouts new shoots from belowground rhizomes; and Broom Crowberry which re-establishes from buried seed after a fire.
On the other hand, many or most of the 30 species observed only in unburnt sections of the trail are wetland species (e.g., round-leaved sundew, Tawny Cotton grass) or species not generally associated with landscapes where there are frequent fires (e.g., Hobblebush, Witch-hazel).
Missing in our inventory of 2012 were a number of species previously encountered on the trail only between the trailhead and Purcell's Pond. That section of the trail, which is not in the PCCL, goes alongside, across, or close to the stream draining Purcell's Pond, also it goes through areas where there is some accumulation of till and through steep embankments leading down to the stream. Moisture-loving species and species characteristic of older forests such as Hobblebush, Striped Maple and Yellow Birch are common in that area, but are largely absent from the trail beyond the bottom of Purcell's Pond. In future efforts, we need to examine the area that lies within the PCCL between Purcell's Cove Road and Purcell's Pond, as well as to give more attention to wetlands and to some groups that we have not documented at all (e.g., mosses), or not very thoroughly (e.g. sedges).
Always, newcomers to this annual HFN/NSNT walk and to the PCCL marvel at the rugged beauty of the landscape we traverse. Even the burnt forest now offers its own splendor in the striking contrast between the burnt trees and regenerating deciduous vegetation, the latter providing 100% cover of the burnt ground after only three years. And there was a special treat in 2012: ripe blueberries and huckleberries in abundance.
The second walk, a week later, took us over a less well trodden trail between Williams Lake and Colpitt Lake. It was led by HFN member Burkhard Plache, who knows The Backlands intimately. Located less than 2 km away from the PCCL, the landscape is broadly similar to that of the PCCL with an undulating topography, high barrens, mixed forest and low-lying wetlands. In spite of many efforts by the Williams Lake Conservation Company and others to restrain development of private lands adjacent to these lakes, new developments are ongoing and afoot and the route we took will be almost completely transformed to residential landscapes within the next decade.
We began at a popular swimming spot by the dam at Williams Lake, proceeded south through lush mixed forest, skirted 0, and then descended again through mixed woods to the western tip of Colpitt Lake. The exposed rock consisted mostly of black slates and siltstones of the Meguma group (Cambo-Ordivician) close to Williams Lake, with fairly abrupt transitions to Devono-Caroniferous granites well away from Williams Lake. (Exposed rock at PCCL is granitic except close to the trailhead.)
As for the PCCL, there is a history of recurrent fires in the Williams & Colpitt lakes area, with large areas last burnt in the 1960s. The tall, massive pines around the eastern side of Williams Lake are apparently survivors of those fires, perhaps approaching a century in age. Otherwise, the oldest trees likely date back only to the 1960s. As at PCCL, Jack Pines abound on the high barrens, a sure indicator of a long history of recurrent fires.
As we walked, we took particular note of streams and wetlands and speculated on how development might affect the hydrological regimes of the area and the water quality of Williams Lake. At a lush gully just east of Williams Lake, we could hear water moving below massive boulders; surface flows occur there only in the spring and during heavy rainfalls. The vegetation in the gully was much like that along the stream draining Purcell's Pond, with a beautiful subcanopy of Striped Maple.
We noted one area which held no water on the day but was muddy from runoff at other times, and wondered it if would qualify as a wetland to be protected when construction starts in the area, similarly we wondered about the fate of a small picturesque wetland dominated by graminoids. We passed by two relatively large wetlands which we assumed, would not be developed, but we speculated that new roads and developments on higher land would affect their integrity nonetheless.
We took a bit of side-trip to reach a high point on the recently burnt barrens. One could turn 360 degrees and see buildings at only a few points on the far horizon. Lower down, one can't see those at all, it is largely bushwhacking territory, and all urban noise is blocked out which is remarkable given the presence of fully urban landscapes and traffic within a kilometer or so.
The burnt barrens shared the vegetation and visual aspects of the burnt lands in the PCCL during the first summer after the spring fire of 2009. Cones of burnt Jack Pine had opened to spread their seed and already there was substantive regeneration of huckleberry and sprouts from birch and red maple. Interestingly, Pinweed, which we had seen at only one small site on the burnt barrens of the PCCL, was quite abundant on some of these burnt barrens.
At one point on the high barrens we encountered a gleaming boulder perched on a granitic outcrop. Two artists amongst us immediately recognized it as "Michael's Rock" and were quite excited to see this fabled artwork. It consisted of a large boulder covered with tin (or aluminum) foil. It had been constructed 4 or 5 years previously and Michael had apparently maintained it, even recently after the fire. It was interesting to think about a piece of art to be so situated, with no plaques to indicate the artist or the purpose and few to observe it. I saw it as an acknowledgment of the wilderness as its own world.
Also intriguing were several lower lying areas where there were massive accumulations of large, angular boulders, most of them composed of the dark Meguma rock. I sent photos to two geologist friends and was referred to John Gosse of the Dalhousie Department of Earth Sciences. He commented: "They do look like small localized felsenmeer (sea-of-rocks) fields, but the slope suggests that there may be a different genesis. Without being there it is difficult to be certain, but these kinds of boulder zones are common in glaciated regions. They form either subglacially or, more commonly, along the sides of retreating ice margins. Specifically this looks like a lateral meltwater channel, formed along the side of an ice lobe, with the water flowing downslope. The meltwater stream would have removed the finer sediment and left the larger boulders alone. The angularity of the boulders is also interesting. This is typical in these situations, where the stream was short lived and did not have the energy to round the boulders' edges. On the other hand, boulders that are transported some distance by glaciers will also lose their angularity (depending on hardness and distance of course). That these boulders appear so angular suggests to me that they may not have been transported very far subglacially (though they were certainly covered by ice during the last major glaciation), and therefore may indicate a zone of the ice sheet that was cold-based (stuck to the substrate for most of its history, instead of sliding and transporting the boulders a long way)."
As we descended towards Colpitt Lake, we again entered some pleasantly cool, mixed forest. We lunched at the western end of the lake where a stream flows out of the lake and, eventually, into Williams Lake. Amongst us was Geoffrey Grantham, a local landscape artist who lives on Purcell's Cove Road and paints wonderful impressions of the "Purcell's Backlands" en plein air. He told us about one of his favourite spots, just up the lake a bit and we asked him to take us there. We passed by a solitary fly fisher on they way, then sat on the shore of a small cove. It was a nice setting to pause before our return hike. Geoffrey talked about the scene and how it changed through the day and the seasons. Not far away, heavy machinery was at work bashing up more barrens to further extend a new development above Colpitt Lake. Soon, these mechanical dinosaurs would be devouring most of the landscape over which we had walked. I felt compelled to take lots of photographs. A few weeks later I went to the opening of Geoffrey's "Images from the Purcell's Cove Backlands" at the Swoon Gallery. I was grateful that Geoffrey had captured so well a sense of these places before they are lost, and to the NS Nature Trust for conserving a few of them.