View topic - Slate Islands, Lake Superior - natural features

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PostPosted: September 2nd, 2014, 8:39 am 
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Location: Bancroft, Ontario Canada
http://www.whitesquall.com/pdf/Slate_Islands.pdf

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PostPosted: September 2nd, 2014, 10:31 am 
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Thanks for the link, frozentripper! What an excellent article!


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PostPosted: September 2nd, 2014, 7:19 pm 
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Thanks for posting that article FT!

There are a few errors to clarify.
quote: "The caribou arrived on the Slate Islands in 1907, when Lake Superior froze over. The Lake has not frozen over since and the caribou are essentially stranded. Actually, Lake Superior froze over in 1995 and there is anecdotal evidence that wolves made it over the ice and began to cull the herd".

Despite the confusing contradiction, the caribou did not first "arrive" on the Slates in 1907. This was the first reference in published literature that someone cited. Caribou have lived throughout Lake Superior, and its predecessor, post-glacial Lake Minong, and of course much further south during the recession of glaciers, and the much colder period of the Little Ice Age up until 1850 when the Little Ice Age ended. Lake Superior has frozen over from mainland to the Slates many times before 1907. There is no archeological evidence studies showing caribou were not there prior to 1907. No doubt they have gone through repeated local extinction events, just like on the much larger Michipicoten Island further east. Local extinction events are common for large animals on small islands. The Slates are the only place in Canada where populations have been documented to be limited by food, and they go through boom and bust cycles, also theoretically synced with budworm cycles which provide bursts of arboreal lichen abundance (see below for link with balsam fir). Accessible terrestrial lichens have been eliminated by grazing caribou. On the mainland, there is no population that has ever been documented to be limited by food. Its always been predation as the limiting factor.

In fact the Lake froze with an ice bridge to the Slates this past winter in March, and 4 caribou were confirmed having arrived on the mainland in March. This is not an implausible event. There were two wolves on the Slates in the early 2000's, and I and a colleague confirmed one living wolf in the early part of that decade in March (I cannot recall exact year as my records are at the office not at home here).

The description of the north shore forest lists a dominance of white spruce in the uplands. In fact black spruce is dominant in the uplands with white spruce as present throughout as a component, but not as the leading dominant species except for a few small pockets.

The entire north shore and the Slates are have a natural background spruce budworm cycle. Spruce budworm outbreaks actually are triggered here when balsam fir reaches a critical mass, then the budworm insect population explodes, approximately in 40 years cycles, give or take. The white spruce gets eaten heavily causing mortality, and black spruce have some mortality but most make it through, thus sustaining black spruce dominance in the long term. Dead balsam fir and dead white spruce branches are the best known substrates for arboreal lichens. Budworm mortality of fir and spruce branches produces vast abundance of the preferred Bryoria black lichens and the less palatable light green Uznia lichens. That pale green "old man's beard" you see there is actually only marginally nutritious, and that’s why you see big gobs of it hanging down all over the place there. Its the black arboreal lichen that is preferred by caribou. If you look closely you will see a distinct browse line for the black arboreal lichens.

The Slates and the mainland are in a current condition where most of the post-budworm killed balsam and spruce from the 1980's and 90's are now down and gone as a substrate. So the population, last time I heard, has declined. We don't know true cause and effect, but it is correlated with the marked decline in arboreal lichen standing biomass. Meanwhile the understories are booming with young balsam fir, and I expect in about 30 years we will see another huge budworm outbreak and the cycle of food abundance will repeat.

Black spruce also does well with fire, being semi-serotinous, whereas balsam fir is killed off by fire, and white spruce is hit as miss for its survival in fire. Hence black spruce is king for area dominance. But fir catches up quickly, and white spruce grows the tallest and does really well in the rich silty valleys along the north shore rivers.

I could go on, but suffice to say, caribou lived off and on the Slates over the centuries, long before 1907. :D

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PostPosted: September 2nd, 2014, 7:58 pm 
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I was told by the shuttle captain that caribou are often found foraging in firepits for charcoal as there are no more forest fires allowed on the Slate Islands and they cannot chew on burnt tree trunks or branches.

I don't know if that is true at all, but finding a caribou in the campfire ashes to me was bizarre.

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PostPosted: September 3rd, 2014, 3:33 pm 
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Thanks to all.
I updated the Slate Islands entry at
http://myccr.com/phpbbforum/viewtopic.php?f=107&t=33998
Scan to near the bottom of the page.

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PostPosted: September 27th, 2014, 11:17 am 
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There is an article on the canoeing the Slate Islands in the fall 2014 issue of Real Fishing Magazine


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PostPosted: October 19th, 2014, 8:53 am 
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Thank you all for posting. Interesting stuff.

Hoop, thank you. "Serotinous" has been added to my vocabulary. :thumbup:

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