Monthly Archive for December, 2005

Lichens: Unusual Partners

Posted December 12, 2005 in Articles.

It’s not hard to find lichens, you simply have to look where other forms of life find the conditions too harsh. Sheer cliff walls, the surface of large boulders, tree trunks, the branches of living and dead trees, and the shaded acidic soils under pines, are all places where lichens thrive. They have even been found on the shells of living tortoises and on exoskeletons of insects.

Lichens are able to grow in these places because they are a combination of a fungus and a photosynthetic partner. The fungus gives the lichen its overall shape and structure and produces pigments that shield its partner from ultraviolet light. These pigments are responsible for the wide variety of colors found in lichens.

The fungus also has fine but tough threads that securely attach the lichen to the surface it’s growing on. The fungus also secretes acids that break down materials into nutrients for the lichen. These acids are so strong that they break down rock into minerals that are used by the lichen.

The photosynthetic part of the lichen is usually an algae, but in some cases it is a type of photosynthetic bacteria known as cyanobacteria. The algae or cyanobacteria (the photosynthetic partners) produce the food for the lichen. Since one part of the lichen makes food by photosynthesis and the other is good at extracting nutrients, together they make a potent combination. Due to this potent combination, lichens can thrive on brances of dead trees and other unlikely places.

A variety of lichens grow on a two-inch long portion of a small branch of a dead black spruce. (Many other lichen photos can be found in the Photography section of this website)

This type of close association between two different species is known as a symbiotic relationship. Most biologists believe that both the fungus and its partner benefit from this relationship. The fungus gets food that the algae or cyanobacteria make, while the algae or cyanobacteria get a protective place to live and nutrients that the fungus extracts from its environment. Recently, biologists have discovered lichens composed of a fungus and both an algae and a cyanobacteria. A close association between two species seems unusual, but the existence of lichens composed of three different species opens up a whole new world of interactions.

Not all biologists, however, think that all the partners in these relationships benefit equally. Some propose that only the fungus benefits and that the photosynthetic partner is a captive of the fungus. Lichenologist Trevor Goward has described lichens as Afungi that have discovered agriculture.@ Many of the fungal partners appear to be unable to exist on their own, while the algae and cyanobacteria are usually able to survive by themselves. It may be that in some cases only the fungus benefits and in other cases both the fungus and its photosynthetic partner benefit.

Whatever the nature of the relationship, it is apparent that lichens can exist in places that neither of the partners can live in on their own. They are found in some of the hottest and driest places on this planet and also in some of the coldest. They are found in Antarctica where no plants or fungus exist on their own and where few bacteria can survive. These lichens simply shut down in the extreme cold of winter, but are able to start functioning again when the temperatures start to rise. Lichens are known to photosynthesize at temperatures as low as -20 Celsius (about 0 Fahrenheit).

This ability to photosynthesize at temperatures well below freezing gives lichens a huge advantage over plants in cold climates. It also allows those in areas like the Boundary Waters to begin producing food in late winter when there is still ice on the lakes and deep snow in the woods. At the other end of the growing season, lichens also extend the period for photosynthesis well into the winter.

They can also grow on a wide variety of surfaces, including man-made ones. Lichens are found on asphalt shingles, brick buildings, cement bridges and even on stained glass. A study in France showed that 16 species of lichen grew on one large old stained glass church window. The growth of lichens on stained glass is a problem on many of the old churches in Europe.

Lichens are also found in specialized natural habitats in the Boundary Waters. Those that are nitrogen-loving are found on cliff faces and boulders that regularly get splattered with bird droppings. Below bird nests and bird perches are located unusual lichens that can utilize the nutrients found in these droppings.

Vertical cliffs have many different kinds of lichens because, depending on their pitch and orientation, they have different habitats. Those lichens that require more water can be found on north-facing cliffs or areas that regularly get run-off from above. Species that can survive with very little moisture are usually found on unshaded south-facing cliffs. Only those places where rock has recently broken off, or areas of exceptional dryness, are totally devoid of lichens. Areas that have a combination of adequate light and some moisture trickling down from above are usually the richest in lichen diversity and growth.

This cliff on Ottertrack Lake is covered with a mosaic of colourful lichens.

The type of rock is also an important factor in what species of lichen grow. The cliffs on Quetico Park’s Emerald Lake are high in lime and have a very different variety of lichens than the siltstone cliffs on Knife Lake or the granite cliffs on Quetico Lake. Some of Quetico’s cliffs  have striking orange lichens, usually from the genus  Caloplaca or Xanthoria, that brighten up the lake even on the dullest of days. These bright, eye-catching lichens can be found on the Man Chain and on the high cliffs of Ottertrack Lake.

The crusty lichens that grow on cliffs, bedrock and boulders, can be found in a variety of colors. Shades of grey seem to dominate, but brown, black, white, orange, red, yellow and even blue ones can also be found. The only place I remember seeing blue lichens was on sloping bedrock at Kings Point on Basswood Lake.

The very large, scaly lichens that are commonly seen on lakeside boulders are known as “tripe desroche” or rock tripe. This lichen, like many others, can withstand long periods of hot and dry conditions. It commonly becomes dry and brittle during July and August. It then looks like large, black, lifeless, scales on the rock.

It survives these dry periods and quickly revives with the first rain. It still looks like large grey or black scabs, but is now softer to the touch. This unappealing lichen can be boiled and eaten as an emergency source of food. Survivors of airplane crashes and others who have run out of food have survived on rock tripe. The Franklin Expedition in the 1820’s subsisted for 11 days in the Canadian Arctic eating these lichens.

In addition to the crusty lichens that primarily grow on rock, there are also a wide variety of small, shrub-like lichens that grow on the ground. Some of these, known as reindeer lichens, are ash-grey in color and stand 2 to 5 inches high. They are commonly found growing in the acidic soils under black spruce and jack pine. These lichens, also known as caribou moss, are the primary source of food for caribou in the winter.

Caribou use their large hooves to dig through the snow to get to the lichens. They leave large circular depressions, known as “craters”, when they are feeding on lichens in the winter. The word caribou comes from a Micmac Indian word that means “one who digs”.

When woodland caribou occupied the Boundary Waters area they undoubtedly relied on reindeer lichens, which are fairly common in this area, for a major part of their winter diet. These caribou, who lived here just sixty years ago, were not the only large mammals to feed on lichens. Moose also eat reindeer lichens, but not nearly to the extent that caribou do.

White-tail deer also eat lichens but, like moose, apparently in relatively small amounts. The exception can be in the winter when the snow is deep and food hard to find. Deer have small hooves and, unlike caribou, are not adept at digging through snow to get at plants underneath. Some lichens, such as Old Man’s Beard, hang down from tree branches. This hair-like lichen can be well over a foot long and is commonly found on trees that are have been killed by spruce budworm.

Old Man's Beard Lichen hanging from a branch of a dead spruce tree.

Since it hangs down from branches, it is accessible even when snow is deep. Deeper snow can even make some available that the deer couldn’t reach when there was little or no snow. There is often a browse line visible, with Old Man’s Beard found only above where the deer can reach. Although important as a survival food, Old Man’s Beard is evidently not heavily utilized when other foods are available.

Years ago I was told that Old Man’s Beard made a tasty snack when walking in the bush. I found that it has a pleasant but bland taste that changed to bitter if chewed very long. Many lichens are reported to have a bitter taste, possibly because the fungus produces toxic chemicals to keep insects and animals from eating them.

Lichens are found on the same cliffs where pictographs are located and in many sites they have grown over the paintings. The location of pictographs was undoubtedly influenced by the presence or absence of lichen growth. Places that had overhangs that reduced the amount of moisture, and therefore the amount of lichen growth, were ideal locations for placing paintings.

If conditions remained the same, pictographs placed in these locations should still have very little lichen growth and still be visible today. However, cliffs also change with time and ideal locations in the past may now have thick lichen growth that totally obscures paintings underneath. Some species of lichens grow so slowly that their progress in covering a pictograph has been used to try and date pictographs.

In some places in North America, lichen was scraped away to leave an image behind. These images, known as lichenoglyphs or lichenographs obviously have a limited life span unless they are periodically renewed. They have been found on Lake Superior and Lake of the Woods, but nowhere in the Boundary Waters to my knowledge.

Although lichens are extremely hardy, they don’t stand up very well to air pollution. They obtain a lot of their moisture from rain and consequently also take up many of the pollutants that are dissolved in the rain water. For this reason, lichens were among the most radioactive organisms tested after the Chernoble nuclear disaster. Lichen diversity drops dramatically when air pollution increases. Many species that were common in urban areas are now difficult to locate.

Although much is known about many of the common lichen species, some of the lichens in our region are unknown and unnamed. Recent studies in forests in the Pacific Northwest found many new species in the canopies of old-growth trees. Undoubtedly new species also exist in the canopies of the old-growth red and white pines in our region also.

The biologist Lewis Thomas, in his book “The Lives of the Cell”, once said: “A century ago there was a consensus that evolution was a record of open warfare amongst competing species, that the fittest were the strongest aggressors. Now it begins to look different. The greatest successes in evolution, the mutants who have made it, have done so by fitting in with, and sustaining the rest of life.”

Lichens are superb examples of how organisms that cooperate can out-compete other organisms. Lichens are remarkable, they photosynthesis like a plant and at the same time they decompose like a fungus. They utilize their dual natures to survive in places where other organisms can’t. They undoubtedly were among the first organisms to grow in our area after the glacier retreated through here about 11,000 years ago. They helped to set the stage for the rich and diverse ecosystems that followed.

These tough but fragile pioneer organisms continue to thrive in the Boundary Waters. There is hardly a cliff, large boulder, patch of ground more than a few metres across, or trunk of a mature tree, that doesn’t have lichens growing on it. They are so common that they become part of the background and go unnoticed.

This summer go out of your way to paddle slowly alongside a cliff and carefully check out the variety of lichens growing on the rock. Run your hands over the cliff face and feel the variety of shapes and textures of the lichens. Cliffs are vertical mosaics with almost as many kinds of lichens as the number of plants you’d find on a similar-sized plot of ground. Lichens of the North Woods, a recent book by Joe Walewski, is an excellent source of information about identifying lichens in Quetico Park and other northern forests.

The next time you are having lunch on the rocky shore of a lake, take a good look at the lichens that you have been walking and sitting on. A small hand magnifier, like those that geologists use, will give a clearer view of these fascinating organisms. The colors and shapes are astounding. You can spend hours exploring a habitat just a few yards wide.

Ice Age Journey

Posted December 12, 2005 in Articles.
Charlie Brooks holding Caribou Antler

Charlie Brooks holding a 10,000 year old caribou antler

Quetico Park contains a wide variety of different habitats: large stands of mature red and white pine, even-aged jack pine and poplar stands (the result of recent fires), wet areas with an understory of moss and overstory of black spruce, and open bogs composed of leather leaf, sphagnum moss and orchids. These and a variety of other habitats in Quetico are home to many different plants and animals.

These familiar habitats and the animals that inhabit them evolved out of the last ice-age, which reached its maximum about 20,000 years ago. At the peak of the last glacial period, called the Wisconsin, virtually all of Canada and a large portion of the northern United States were covered with ice. All of Minnesota was covered by glacial ice except for the southeast corner of the state.

It has been estimated that this glacier may have been up to one mile thick. A glacier of this size obviously had an enormous impact on the land, both as the glacier was getting larger and as it was shrinking. As it grew, its enormous weight gouged out weak areas in the bedrock and ground up boulders and bedrock into a mixture of sand, gravel and small rocks. This glacial till is found throughout Quetico today. Boulders frozen into the ice sometimes left deep scratches called glacial straiae that are visible on the shores of many lakes, including Ottertrack, Knife and Cirrus. When the glacial advance stopped, long ridges of glacial till, called moraines, were left behind. A large terminal moraine, known as the Seep Rock Moraine, passes through the northeast corner of the park.

The slow retreat of the glacier was equally dramatic. The enormous amounts of water melting off the glacier created numerous lakes and ponds, and water levels were generally higher than they are today. A huge island-studded lake called Lake Agassiz temporarily covered half of Quetico Park. Big, fast-moving rivers deposited sand and silt into these enlarged lakes. When the lakes shrunk to their present size, they created flat, generally boggy areas from what had been shallow bays. The best example of this in Quetico is the flat, sandy area east of Kawa Bay of Kawnipi Lake. The Wawiag River now winds through silt and sand that was deposited in a shallow bay of what is now Kawnipi Lake.

The changes in vegetation that have occurred since the glacier retreated are striking. Fortunately, a record of the past plant communities that succeeded the glacier can be found in the bottom of lakes and ponds. Wind-blown pollen settles on lakes and sinks to the bottom, where it is eventually covered with more pollen. Since pollen from different types of plants is of different sizes and shapes, the pollen can be used to give an idea of past plant communities.

Pollen cores from the bottom of a variety of lakes and ponds in Northwestern Ontario and northern Minnesota have been analyzed, although no detailed pollen studies have been done from lakes in Quetico. Lake of the Clouds, a small lake in the BWCAW just south of Ottertrack Lake, has had an analysis of the pollen from the bottom of the lake, as has Rattle Lake, which is located just 100 miles northwest of Quetico Park. The pollen from both lakes shows similar trends in change in vegetation with time.

The bottom layer of pollen represents the first plants after the glacial retreat and the top layer represents plants from more recent years. In between is the pollen that represents the history of plant succession of the long intervening period. One of the many complicating factors is that some plant species produce large amounts of pollen that can be carried hundreds of miles by the wind, while others produce very little pollen. Analysis of pollen cores gives a picture, although somewhat fuzzy, of the vegetation change in a particular area.

It is currently thought that Lake of the Clouds became free of glacial ice about 11,500 years ago, and that Rattle Lake, being father north, became ice free a few hundred years later. The pollen from the oldest zone in both lakes indicates sparse vegetation that was composed mainly of lichens, herbs and shrubs. Pollen from higher lavels showed an increase in levels of spruce and birch. About 9,200 years ago at Lake of the Clouds and 8,600 years ago at Rattle Lake, the levels of spruce declined and levels of species of pine greatly increased.

The pollen from both lakes shows a strikingly similar pattern from tundra or tundra-like conditions, changing to a spruce-birch forest, which evolves into a predominantly pine and spruce forest. It apparently took over 2000 years for Quetico to make the transition from a land just freed from glacial ice to a forest mosaic similar to what is present today. Prior to the forest mosaic was a period when the vegetation was much different from today and when, consequently, the animals were not those we expect to see in Quetico.

This post-glacial period was characterized by a warming climate, large lakes produced by the melting of glacial ice, and vegetation that was a rich patchwork of herbs, grasses, mosses, fungus, shrubs and small trees that could have supported a high density of animals. This tundra-like vegetation is thought to have been unique, and no environment exists today that matches it. The tundra-like environment that was home to a variety of ice-age mammals is sometimes referred to as the mammoth steppe – named after the woolly mammoths, the largest of the ice-age mammals.

When the southern part of Quetico was first freed of glacial ice about 11,500 years ago, the land to the south contained a staggering array of large mammals known as the ice-age megafauna. They included woolly mammoths, mastodons, sabre-tooth tigers, camels, horses and woolly rhinoceroses. Some of these animals were of spectacular size, such as 500-lb. beavers, giant sloth that were 12 feet tall standing on their hind legs, and dire wolves weighing up to 200 pounds.

By 11 000 years ago, when all of Quetico was free of glacial ice, many of the large ice-age mammals were extinct or on their way to extinction. It is not known what caused their extinction, but there is no shortage of theories. The warming of the climate and the accompanying changes in vegetation may have made survival impossible for cold-adapted species like the woolly mammoth and woolly rhinoceros.

When the ice was retreating through Quetico, there was a Palaeoindian culture in the Americas known as the Clovis culture. The Clovis culture is characterized by large, fluted spearpoints called Clovis points. In numerous locations, Clovis points have been associated with the fossil remains of woolly mammoths. The Clovis people were successful hunters of woolly mammoths and other megafauna. Clovis points have been found in central and southern Minnesota and throughout Wisconsin, except for the northern extreme. No evidence of the Clovis culture has been found in the BWCAW or Quetico, but recently a Clovis point was reported from the Duluth area.

The extinction at the end of the last ice age left ecological niches that remain empty to this day. The warming of the climate caused a slow but steady replacement of the rich tundra-like environment, which had provided a side variety of food for grazers and browsers, with a predominantly forested environment. In North America, the mammoths, horses, camels, ground sloths, and giant beavers that once were prominent mammals disappeared with the rich post-glacial environment that they thrived in. The noted zoologist Alfred Russel Wallace once stated: “We live in a zoologically impoverished world, from which all the largest, the fiercest, and strongest forms have disappeared.”

There are skeletal remains of these megafauna throughout the Americas. In areas with hot, dry climates, such as much of the American Southwest, there are numerous well preserved remains of ice-age mammals. The LeBrea Tar Pits in Los Angeles contain thousands of skeletons from this time period, especially of carnivores such as dire wolves, sabre-tooth tigers and the American lion. In Siberia and Alaska, virtually intact woolly mammoths have been recovered from permafrost. In 1901, portions of a woolly mammoth that had been frozen for 20,000 years were eaten by a dog team when a Russian scientist came across a woolly mammoth eroding out of the ice in northern Siberia.

The acid soils of the Canadian Shield are, however, very hard on bone and antlers, and only in unusual situations do they last a decade, yet alone thousands of years. Moose bones and antlers two or three years old are usually heavily chewed by rodents and covered with fungus, moss and bacteria that rapidly recycle the valuable nutrients. Only unusual conditions, where the remains settle into a peat bog or are quickly covered with silt at the bottom of a lake, allow for long term preservation of bone.

However, the remains of a few ice-age animals have been recovered near Quetico. A skull of an extinct form of bison was found while dredging for peat on the edge of a bog near Kenora, Ontario. The skull of this bison was picked up intact by the backhoe. The operator of the backhoe joked, “I told my friends that I dug up the Devil himself.” The presence of a bison north of Lake of the Woods was a shock, but it is consistent with the concept of a tundra-grassland environment after the retreat of the glacier.

The bones of woolly mammoths have been recovered in southern Minnesota, Wisconsin and Manitoba; and recently, the bones of a mastodon were recovered in southern Wisconsin. In a few cases, the remains of large mammals have been found in association with human artefacts. The most clear-cut correlations are a bison kill site near Lake Itasca that dates back to about 8,000 years ago and a woolly mammoth in southern Wisconsin that dates to 11,000 years ago. Both of these sites had animal bones and stone tools found close together and were apparently kill sites.

The most spectacular find, however, occurred just north of Atikokan, deep in the silt at the bottom of a lake. Iron ore was discovered at Steep Rock Lake in 1938, and diamond drilling showed that a rich ore body was located at the bottom of the lake. The demand for iron ore was high because of World War II, so the decision was made to drain the lake to get at the ore. Huge dredges were brought in to pump out the silt that covered the ore. The dredges were able to pump the silt from the bottom of the main body of the lake, but along the lakeshore the silt had to be washed into the rapidly draining lake using high pressure hoses.

On April 16, 1957, Charlie Brooks and Dick Kaemingk were surveying the monitored area along the shore. They noticed a large antler in the silt and dug it out and set it aside. Since the goal of the operation was to remove the silt and get at the ore underneath, the exact depth of the antler in the silt was not recorded. However, at the time of discovery, it was estimated that the antler was located beneath 60 to 100 feet of silt and clay. The astounding depth of silt above the antler indicated that it was probably quite old. It is of interest that there was about 450 feet of silt in the deepest part of Steep Rock Lake. The antler was deeply buried, but there were still hundreds of feet of silt below it.

The enormous amount of silt in Steep Rock was undoubtedly due to the fact that the fast flowing Seine River dropped its glacial debris into the lake when it slowed down upon entering the lake. The antler was found less than a thousand feet from the falls where the river enters the lake. Since the antler is in such good shape, it probably did not come down the Seine River and over the falls into the lake.

The caribou antler recovered by Brooks and Kaemingk was not the only one that had been noticed. Brooks remembers seeing other antlers on top of the monitor barges, presumably put there by other workers and later discarded. It is not surprising that the presence of caribou antlers was not considered unusual since woodland caribou were common in the area until the 1930’s. What is extremely fortunate is that someone had the curiosity and foresight to set one aside. (see photo of Charlie Brooks holding the 10,000 year old caribou antler from Steep Rock Lake at beginning of article)

It is ironic that the caribou antler was found near Atikokan, since Atikokan means “caribou bones” in Ojibwa. There are other references to caribou in the area, with a Caribus Lake and Caribus Creek just south of Atikokan. There is also a Caribou Lake in the eastern BWCAW. When I first saw the antler in the mid-1970’s, it had been hanging for over a decade in the entrance to the building that houses the Atikokan Library and Museum, a log building near the main street of Atikokan.

Lawrence Jackson, an archaeologist associated with Trent University, recently had the antler carbon-dated, and it was found to be approximately 10,000 years old. Originally thought to be from a woodland caribou, it was analyzed by experts and is now thought to be from a male barren ground caribou. The presence of barren ground caribou on Steep Rock Lake 10,000 years ago seems surprising, but it is consistent with evidence from pollen studies that strongly indicate that this area was primarily a mixture of spruce, birch and tundra at that time.

Barren ground caribou migrate in large herds and shed their antlers in early winter after the completion of the rut in the fall. A male caribou probably shed his antlers on the ice surface of Steep Rock Lake after spending the summer somewhere north of Atikokan. The caribou then continued on its journey with the rest of the migrating herd to its winter range to the south.

The herd of barren ground caribou that shed their antlers on Steep Rock Lake as they began their migration to their wintering grounds to the south would have been a major food resource for Palaeoindians living in the area. Caribou are hunted during the fall migration for both their hides and for food. The location of these ancient migration routes is a mystery.

In the winter of 1983, a local trapper named Phil Sawdo discovered some rock paintings on a creekside cliff north of Montgomery Lake. At this site, there are two sets of paintings about fifty metres apart. One set portrays a caribou and human-like figures and other a moose or caribou. These paintings are unique in Quetico in that they are not located on a navigable body of water; you can paddle up to all the other known pictograph sites in the park. Phil Sawdo thought that the caribou were formerly ambushed in the narrows formed by the pictograph cliff and a high hill directly opposite. Two creeks come into the area north of Montgomery, and the small valleys associated with them could have funnelled migrating caribou into the narrows where the pictographs are located.

It is not known how old the Montgomery Lake rock paintings are, and there are no rock paintings that are known to date back to Palaeoindian times. However, it is certainly possible that the Montgomery lake rock paintings depict caribou at a spot where they were hunted during migrations thousands of years ago.

Because of the similarity between barren ground caribou and woodland caribou that were present in Quetico until the 1930’s and the unknown date of the rock paintings, it is just speculation that there is a connection between the barren ground caribou antler from Steep Rock Lake and the rock paintings on Montgomery Lake. There is, however, other evidence that caribou were in the area 10,000 years ago and that they were hunted by humans. A large Palaeoindian site near Thunder Bay produced fragments of bone that have been tentatively identified as caribou. Archaeologists have suggested that this site, which is also about 10,000 years old, and others from the same time period are evidence of caribou hunting by bands of Palaeoindians along the north shore of Lake Superior.

There are also numerous Palaeoindian sites in Quetico and BWCAW that apparently date back at least 10 000 years. The culture in the area at that time is known as the Plano and is thought to have succeeded the Clovis that ended about 11 000 years ago. Because of the lack of organic material, none of these sites have been carbon dated. They have been primarily dated by the presence of large spearpoints which are very similar to those found at dated Palaeoindian sites to the south. The large spearpoints that are characteristic of Palaeoindian sites are beautifully worked and made from a variety of stones.

By the time the Clovis culture had evolved into the Plano culture, many of the ice-age megafauna were extinct. All of the evidence for Palaeoindians in Northwestern Ontario and the BWCAW is believed to be from the Plano culture. The Clovis people, and the woolly mammoths and other megafauna they co-existed with, may never have reached Quetico. However, the area was free of glacial ice in time for people of the Clovis culture and the ice-age animals they hunted to have entered and lived in Quetico. They would have, however, had to live close to the leading edge of the glacier.

So . . . I’m still looking for a Clovis point, a faced pictograph that depicts a woolly mammoth, and the bones of a mastodon or dire wolf eroding out of the silt banks of the Wawiag River. I may never find any of them, but the thought that it is possible adds another dimension to a trip into Quetico.  (An updated and enlarged treatment of Quetico’s Ice Age legacy can be found in my book.)