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Island Biogeography and
the Effects of Fragmentation
on Ontario’s Boreal Forests
Copyright 1996 by Lynna Landstreet. Please don't
reproduce or redistribute this paper without asking
me first. I'll probably say yes if you do ask, but I do like to know
where my work is going.
If you wish to cite this paper in your own work, the following format
is suggested: Landstreet, Lynna. “Island Biogeography and the Effects
of Fragmentation on Ontario’s Boreal Forests.” Unpublished paper,
available electronically on Wild Ideas (http://www.wildideas.net).
This is better than using the specific URL of this document, because I
may reorganize the directory structure of this site from time to time,
causing the addresses of specific pages to change.
 ver the past ten to twenty years, there has been an upsurge of interest among environmentalists and the general public in the fate of Ontario’s northern forests. This has centred to a large extent on high-profile land use conflicts such as the debate over logging in Algonquin Park, the more recent concern over road-building and logging in the Algoma Highlands, and of course the Native land claim that led to the now famous road blockades in Temagami during the late 1980’s (see Hodgins & Benedickson 1989; Bray & Thomson 1990). This has paralleled an increasing scientific interest in the ecological role and dynamics of boreal forests in general (see Wein et al., 1983; Sherman 1991).
Part of the reason for this concern is the fact that the forest industry has become increasingly focussed on the northern forests as those in the south have been depleted, or fallen to agriculture or urbanization. As well, advances in logging (and mining) technologies have opened up many hitherto inaccessible areas to resource extraction. In short, many people are beginning to wonder if what was once viewed as a vast, limitless wilderness may not have its limits after all.
The potential ecological impacts of increased resource extraction in the various types of forests in Ontario are too many and varied to cover fully in this paper. Thus, I will focus here on habitat fragmentation caused by logging, and the potential use of island biogeography theory in analyzing its effects. As well, while the Great Lakes-St. Lawrence forests face serious threats and the Carolinian forests of southern Ontario have been almost eliminated, this paper will focus on the boreal forest biome which covers the majority of the province and contains most of the largest tracts of intact wilderness.
I will first briefly review the major ecological and biogeographical characteristics of northern Ontario’s boreal forests, and then the fundamentals of island biogeography theory as applied to habitat islands, with particular reference to Larry D. Harris’s work in applying it to the old-growth forests of the US Pacific Northwest (1984). Finally, I will consider the applicability of the theory, and of Harris’s management recommendations, to Ontario’s boreal forest region.
The boreal forest biome is a circumpolar region covering large areas of Canada, the former Soviet Union, and northern Europe and Asia. It is the northernmost section of the temperate zone before it gives way to the Arctic, the northernmost extent of continuous forest in the northern hemisphere, and the largest forest region in the world. (Carleton 1991)
The region is characterized climatically by long, harsh winters and short, mild summers. Soils vary from shallow, sandy, mineral soils overlaying bedrock and in places giving way to the bare rock, to the rich but poorly drained organic soils of the extensive wetlands and peat bogs. Moisture levels vary at least as widely; upland areas are often very dry, while lowland areas may be quite wet. (Sims et al., 1990: 2)
The major tree species found in Ontario’s boreal forest are coniferous: white and black spruce, balsam fir, tamarack, eastern white cedar and jack pine, with some red and white pine occurring along the southern regions where it begins to approach the Great Lakes-St. Lawrence forest. Black spruce is probably the most prevalent, since it can grow in a wide variety of conditions from Sphagnum bogs to nutrient-poor upland sites with less than 20 cm of soil. (Wickware et al., 1990) Dr. Terry Carleton (1991) has suggested it should replace the sugar maple as our national tree. Black spruce is classed as a pioneer species, as is jack pine, another hardy species that thrives in poor conditions and disturbed areas. (Sims et al., 1990: 31, 46)
White spruce and balsam fir, on the other hand, are shade-tolerant trees that grow primarily in the understory, or succeed the pioneer species if the area avoids fire long enough. (Carleton 1991) Tamarack and cedar are associated primarily with wet areas such as peatlands, with tamarack in particular tending to colonize areas that were previously too wet to support trees, since it requires less shade than does cedar. (Sims et al., 1990: 39-40, 67-68)
The few deciduous trees associated with the boreal forest (apart from tamarack, which is both coniferous and deciduous), white birch, balsam poplar and trembling aspen, tend to be pioneer species as well — fast-growing, opportunistic species that thrive on disturbance, and frequently displace slower-growing conifers. Aspen and poplar, in particular, tend to reproduce by root suckering, meaning that they can spread rapidly from any residual trees left after fire or logging. White birch tends to produce sprouts from cut stumps — sometimes as many as six or seven from one cut tree. (Sims et al., 1990: 89)
Boreal forests tend to support much less in the way of a shrub layer than do deciduous forests, particularly in predominantly coniferous stands; birch and poplar stands support a wider variety of shrubs. But in most boreal forest stands, the major plant communities apart from the trees are the feathermosses and fungi at ground level. While plant diversity is much less than in the tropics, the gradient is reversed when looking at fungi; the boreal forests support more. Both the feathermosses and fungi play an important role in nutrient cycling. (Carleton 1991)
One of the most commonly noted features of the boreal forest is that it is exceptionally well adapted to disturbance, generally in the form of fire. Wein (1990) has called fire “the most overpowering natural influence in the boreal forest, both in time and space... the plants and animals have to dance to the musical score of fire.”
This fact has enabled many, particularly in the forest products industry and related government ministries, to justify intensive logging operations on the grounds that they mimic the effects of fire, a claim that has been contested by environmentalists but still enjoys widespread acceptance. As University of Alberta plant ecologist George La Roi (1991) puts it: “We are now in the process of shifting over to a new kind of disturbance regime, in which fire is being suppressed and we are now taking the wood and using it for purposes other than incinerating it up into the atmosphere.” (51-52)
Currently, the boreal forest is facing record levels of pressure due to intensified logging operations. Recent satellite data have shown considerable acceleration in logging-related disturbance in northern Ontario. Since the 1940’s, the disturbance rate has quadrupled from 2,000 km2/decade to 8,000 km2/decade, and the majority of this was due to logging; only 4% of the surveyed area had been affected by fire while 30% had been logged. The greatest impacts can be seen in the richest, most productive forest areas; 70% of the eskers and almost 100% of the outwash plains had been logged since 1940. (Pereira 1994)
In addition, clearcutting is on the rise. In the 1970’s, it accounted for 70% of the logging operations in Ontario; the proportion has now risen to 90%. (NFD 1993) Reliance on this method of cutting, as compared to less disruptive techniques such as shelterwood logging, means that differences between cut and uncut areas are maximized, increasing the potential effects of fragmentation of the forest.
But what does this mean? What are the long-term effects of dividing a formerly intact forest region in to a patchwork of clearcuts? Is it really equivalent to natural disturbances such as fire? What are the likely impacts on wildlife populations? For clues, let us look to theory of island biogeography.
Island biogeography theory, as we know now it, was pioneered by Robert H. MacArthur and Edward O. Wilson (1967). Looking at the population fluctuations of species on various islands and archipelagos, they attempted to derive mathematical formulas for the rates of colonization and extinction of that could be expected under different conditions. While their work focused on literal, oceanic islands, rather than islands of fragmented habitat, they noted at the outset the relevance of their work to other ecosystems, particularly in the light of increasing environmental change:
Insularity is... a universal feature of
biogeography. Many of the principles graphically displayed in the Galápagos
Islands and other remote archipelagos apply in lesser or greater degree
to all natural habitats. Consider, for example, the insular nature of
streams, caves, gallery forest, tide pools, taiga as it breaks up in
tundra, and tundra as it breaks up in taiga. The same principles apply,
and will apply to an accelerating extent in the future, to formerly
continuous natural habitats now being broken up by the encroachment
of civilization... (3-4)
The foundation of MacArthur and Wilson’s theory is the relationship between island area and species richness, or the species area curve. This can be expressed mathematically by the equation S = CAz, where S is the number of species, A is the area of a given island, C is a parameter that varies widely depending upon the taxon or taxa being considered and the unit of area measurement, and z is a constant which generally falls between 0.2 and 0.35. (17-18)
This equation is a more flexible version of the frequently heard claim that division of an island’s area by ten results in a halving of the fauna, which originates with P.J. Darlington’s work with amphibians and reptiles in the West Indies during the 1950’s, but has been broadly generalized to other areas. The inclusion of the parameter C allows for variations in taxon, biogeographic region and population density, any one of which could skew the results away from Darlington’s rule. (8-9)
Other factors identified as influencing island biogeography are distance of an island from the mainland, and between-island distance. They propose a model of species equilibrium based on the intersection of an immigration curve, determined by distance from the island to the mainland (source of the population from which new immigrants are arriving), and an extinction curve, based on the island area. (21-22)
As an aside, it has more recently been noted that some metapopulations in which local dynamics are affected significantly by migration may in fact have multiple equilibria rather than a single predictable equilibrium point. In a study based on a Finnish butterfly, occurring in 65 separate patches in a highly fragmented habitat, Hanski et al. (1995) found a bimodal pattern that suggested two alternative stable equilibria were possible. This shows that the species area relationship may not be as linear as is usually assumed. The possibility of multiple equilibria makes it difficult to precisely predict population fluctuations in highly fragmented landscapes. Metapopulations with multiple equilibria may suddenly collapse toward extinction even if an area is degrading only slowly.
Between-island distance comes into play with what MacArthur and Wilson term the stepping-stone effect, wherein the immigration rate of distant islands that occur in clusters can be influenced more by the proximity of the other islands (some of which are presumably closer to the mainland) than by the distance to the mainland itself. This raising of the immigration curve in clustered islands has the effect of lowering the overall species-area curve, so that species richness is less directly dependent upon the area of the specific island. (29-30)
Others have since built on MacArthur and Wilson’s theories, specifically with reference to habitat islands. One of the most influential books in this respect has been Larry D. Harris’s The Fragmented Forest: Island Biogeography Theory and the Preservation of Biotic Diversity (1984). In it, Harris applies the principles of island biogeography theory to the increasingly fragmented forests of the US Pacific Northwest region in an attempt to come up with an ecologically sound management plan that will ensure both a sustainable forest industry and long-term survival of old growth forests.
Harris notes two key distinctions between oceanic islands and habitat islands. The first, which can help to mitigate the effects of fragmentation, is that the “sea” surrounding old-growth forest islands is not uniformly hostile. There are bound to be differences in colonization rates between two old-growth islands separated by an area of mature second-growth forest, and two such islands separated by a clearcut, or a housing subdivision. (88-89)
The second, more worrying distinction is the lack of a source population from which potential colonizers might come. Island biogeography typically assumes that islands are located at some distance from a continent which is presumed to serve as a virtually inexhaustible source pool of potential immigrants. But with the rate of conversion from natural forest to short-rotation monoculture plantations, the time is not far off (and indeed, has arrived in many areas) when there will be no source population upon which habitat islands may draw; the island system will be the only species pool there is. (89) This obviously has serious consequences for the preservation of biodiversity in protected areas.
Another point with relevance for protected areas is the distinction between oceanic islands formed by volcanic processes, which begin with a barren substrate and gradually accumulate colonists, and islands which were initially part of a continent but were separated by rising sea levels. The former start with no flora or fauna, and are gradually built up by immigration to progressively more complex levels of diversity. The latter start with a full complement of species, and gradually lose them due to localized extinctions. Both can be assumed to gradually reach some sort of equilibrium, but even allowing for size and degree of isolation, volcanic islands almost never attain the same degree of species richness as continental shelf islands. (71-72)
The parallel Harris draws for habitat islands is as follows: old-growth islands salvaged from existing large tracts are likely to resemble continental shelf islands in terms of their species assemblages, while isolated second-growth replacement stands following clearcut logging will bear more resemblance to volcanic islands. (73-74)
What Harris proposes as a solution is a system of old growth islands, each surrounded by a larger patch of long-rotation managed forest, divided radially into sections which are cut on an alternate basis at a predetermined interval (see diagram). For the Oregon Cascades region which he uses as an example, he proposes a total rotation time of 320 years, which is one-third more than the minimum age required to classify a stand of forest in that region as “old growth,” 240 years. This would ensure that at any given time 25% of the managed forest within a long-rotation island would consist of old growth and 75% regeneration stands of varying ages, thus providing habitat for both species requiring mature forest and those inhabiting other successional stages. If the managed area is divided into nine wedge-shaped stands, as he proposes, then one stands would be cut every 35 years, or, if two thinnings were used per short rotation rather than one clearcut, every seventeen years. Cutting the wedges on an alternate basis would ensure both maximum protection against windthrow and other disturbances for the central old growth core, because no one side of it would be too exposed, and also assure a certain amount of edge effect for those species that benefit from it, because each newly cut section would be positioned next to a relatively mature one. (130-134)
One problem that immediately comes to mind with this system, which Harris does not address, is whether or not a 240 year old stand of managed forest is really equivalent to a stand that has never been logged. By basing his classification of forest stands simply upon age, he ignores the fact that logging may have other impacts than simply removing an existing stand of trees and starting over with a new, and presumably equivalent one.
Modern industrial forestry practices such as whole-tree harvesting and mechanical site preparation typically remove the slash, or coarse woody debris, which could otherwise have sheltered young seedlings and provided much-needed nutrients to the soil, as well as disrupting the nitrogen-replenishing moss and fungal layers — a matter of no small importance in the boreal forest, as we shall discuss in more detail later. (Noss 1993; WL 1995b) Additionally, the structural simplification resulting from the removal of snags and dead logs has been shown to reduce species richness in the forests of the Pacific Northwest. (Noss 1993)
Feller-bunchers and other heavy equipment used in clearcut logging can have considerable impact upon the soil, causing rutting, compaction and/or erosion, depending upon local conditions (WL 1995b). Mou et al. (1993) recount an experiment at the Hubbard Brook Experimental Forest in New Hampshire wherein they compared vegetation recovery and nutrient accumulation on sites where the soil had been severely disturbed by whole-tree harvesting to less disturbed sites, and found that the level of disturbance had significant impacts, both on overall biomass accumulation and on the species composition, with some species being more able to thrive on bare mineral soils than others.
There are also other factors that need to be taken into account in the evaluating the concept of a system of habitat islands. MacArthur and Wilson’s stepping stone effect, which Harris relies upon in his long-rotation islands proposal, may have its limits. Burkey’s (1995) comparison of extinction data from various archipelagoes casts some light on what has been termed the SLOSS — Single Large Or Several Small — controversy in protected area planning. Consistently, he found that species found on a number of small islands as well as one larger one were more likely to become extinct on all of the small islands before they would on the single large island. Data on lizards, birds and mammals on mountaintops and in isolated nature preserves showed similar trends. Clearly, while a system of small islands may be better than nothing, it is not the same, from a biodiversity standpoint, as preserving a large intact area.
Then there is the possibility that habitat fragmentation may affect not merely overall species richness, but also the behaviour of individual animals of a particular species. Redpath’s study of tawny owls (1995) showed that size of forest patches had observable effects on breeding success, territorial behaviour and turnover, indicating that the effects of fragmentation upon particular species could vary widely from what might be predicted by the basic rules of island biogeography. The owls, for example, bred better in intermediate-sized woods than in either continuous wood or small fragments. Redpath cautions that attempts at evaluating the effects of fragmentation on any species must take into account not only general principles, but also the particular needs of the species in question regarding territory, mating behaviour, etc.
The key question here is precisely how well does Harris’s work which, as noted earlier, is based on the ecology of the Pacific Northwest, and in particular the Cascades region within Oregon, apply to Ontario’s boreal forest, a very different ecoregion?
One of the key traits of the boreal forest system, as discussed briefly earlier, is that it is in large part a disturbance-based system, well adapted to the occurrence of periodic forest fires. This fact is often cited, as noted earlier, as justification for intensive logging practices. On the face of it, it might also appear to suggest that these forests would be less susceptible to the effects of fragmentation than other forest types which are less adapted to disturbance, since fire, presumably, has the capacity to fragment habitat as well.
But there are certain key differences between clearcutting and fire that are often overlooked. And while that topic could undoubtedly fill a paper in its own right, I will attempt to briefly address some of them here, since they are of some importance in assessing the difference between natural and anthropogenic disturbances.
It has been frequently noted that jack pine, one of the predominant boreal forest tree species, is assisted in reproduction by fire. Its serotinous cones can remain closed for up to 25 years without the influence of heat to open them, which clearcutting cannot provide. Some will open on exposed ground that receives enough full sunlight to heat it to a temperature of 50 , but this is not as efficient as fire and tends to result in lower rates of regeneration. (Sims et al., 1990: 46-47) Postcut burning has been used to assist jack pine regeneration, but results are mixed. (Chrosciewicz 1983a, 1983b, 1988). Black spruce cones are also assisted in opening by heat. (Sims et al., 1990: 31)
Fire also has the effect of releasing nutrients to the soil which were previously tied up in the overstory layer. (Hawkes 1983) Also, wildfires do not necessarily kill all the trees in the stands they affect. While young trees, and highly flammable species such as white birch and balsam fir, are easily killed by fire, many other boreal species, such as balsam poplar, red and white pine and tamarack, can survive small fires. (Sims et al., 1990) These superficial patch fires are in fact more common than the devastating large-scale fires that make the news; due to poor drainage in many areas of the boreal forest, and the relative infrequency of droughts of sufficient duration to completely dry out the organic layer on the forest floor, many fires only burn off the drier top layers of litter, while leaving intact an organic layer of variable thickness. (Thomas & Wein, 1983)
In addition, both the heat of the fire and smoke blown offsite can kill pathogens that would otherwise threaten the surrounding forest. And the heating and cooling process can crack rocks, assisting them in breaking down into soil. (WL 1995b)
Logging, on the other hand, offers little assistance to heat-opened cones. The mature trees which a fire might have left intact are often the highest priority for cutting. And, especially when whole-tree harvesting is used, nutrients are not returned to the soil, and, as noted earlier, there are serious impacts on both the soils and the moss and fungal layer. While leaving the woody slash onsite, and postcut burning, may help to alleviate some of these problems, obviously the bulk of the organic material — the trees themselves — is taken offsite for processing, so a clearcut still cannot be said conclusively to mimic a natural fire.
Another major difference between fires and logging, and one with serious implications for the applicability of Harris’s island system, is the issue of hardwood conversion. The major boreal hardwoods — white birch, balsam poplar and trembling aspen — are disturbance-adapted, pioneer species that regenerate quickly following either burning or logging. While the initial rush of nutrients into the soil following a fire can greatly stimulate root suckering in aspen and poplar, suckering also tends to proceed fairly quickly after logging, as it is stimulated by damage to the stem or roots. (Sims et al., 1990: 74, 81, 85) White birch, as mentioned earlier, sprouts copiously from stumps, often replacing one cut stem with 6 or 7 new ones. Conifers, however, enjoy no such reproductive advantages after logging, and substituting clearcutting for wildfire, far from replacing one disturbance with another equivalent one, can have serious impacts on ecological succession. Under normal circumstances, the faster-growing hardwoods provide shade for the slower-growing, fire-generated coniferous seedlings, and are eventually succeeded by them, if the stand escapes a second fire for long enough. (Carleton 1991) White birch is particularly effective as a “nurse crop.” (Sims et al., 1990: 93) But if the conifers fail to regenerate successfully after cutting, the species composition of the entire forest can change.
This is not mere speculation; a 1992 government study of more than 1,000 clearcut plots in northern Ontario confirmed that spruce regeneration has dropped by 77%, while birch and poplar regeneration has increased 216% (Hearnden et al., 1992) Rather than concern for the declining conifers, the government has instead expressed optimism regarding the new “surplus of hardwood,” and encouraged the industry to find uses for it with generous financial incentives. This has resulted in, among other things, four new oriented strandboard plants in northern Ontario, which use small-diameter trees such as poplar, aspen and birch to produce a type of construction panel similar to plywood. This has provided a serious disincentive for the industry to manage forests sustainably, since if money can be made from fast-growing, undersized hardwoods as efficiently as from mature conifers, there is little economic reason to stem the tide of hardwood conversion. (WL 1995a)
However, there is certainly reason on ecological grounds to be concerned about a landscape-level shift in forest composition. Different forest types support different wildlife species, and any change in the availability of specific types of habitat is likely to induce comparable changes in abundance of animals that use the declining habitats. And it raises serious doubts about the applicability of Harris’s long-rotation island system in the boreal forest. The system is based on the assumption that at a certain age, a regenerating clearcut stand becomes functionally identical to an old-growth stand, while in a northern Ontario context, this may not be the case at all. Putting such a system into practice there would involve much more complex planning; rather than the wedge-clearcutting system Harris recommends, a combination of shelterwood cutting and prescribed burning might be needed in some areas to maintain the existing species balance.
The hardwood conversion issue also raises the question of whether the already existing level of fragmentation might be more severe than it appears at first sight. The “sea” that surrounds the islands of mature coniferous forest, increasingly, is not composed simply of younger forest, but of a completely different forest type. Large areas of what is considered to be contiguous forest may in fact be composed of smaller fragments of different forest types, with attendant implications for MacArthur and Wilson’s species-area curve.
Obviously, those implications are dependent on the habitat requirements of the species in question. Moose, deer, and hares, for example, can browse on either cedar foliage, the undergrowth of spruce-fir stands, or on trembling aspen, so they are less likely to be affected by stand conversion. (Sims et al., 1990: 37, 71, 85) Other species, however, may not be as adaptable. While Canadian old-growth boreal forests have yet to be as prominently linked with a specific species as has happened in the Pacific Northwest with the northern spotted owl, there has been a certain amount of research done on the pine marten (Martes americana) as an indicator species.
Thompson (1994) compared marten population levels in cut and uncut boreal forests in Ontario, and found that marten density indices were about 90% higher in the uncut forests. The marten resident in old growth forests, in addition, had higher mean ages, were more productive, and suffered lower mortality, both natural and via trapping, than did the marten found in the second-growth forests. Significantly, the old growth forests were dominated by coniferous tree species, while the logged forests, regardless of age, were now dominated by deciduous trees, which is likely to have influenced the magnitude of the difference; other studies performed in cut and uncut deciduous forests showed a smaller, but still significant, difference. Thompson hypothesizes that the closed canopy of mature coniferous forests in winter provides greater protection from predators, particularly raptors. A further study by Thompson and Colgan (1994) on marten activity attempted observed that martens enjoyed considerably more hunting success in old-growth coniferous forests as well.
Sadoway (1986) also found that marten have a strong preference for mature, unlogged forests with dense canopy cover and numerous deadfalls. In winter, fallen logs protruding from snow act as runways and provide access to prey underneath, and the thermal stability of mature forests reduces environmental stress. Female martens are more restricted to mature forests than are the males, who may occasionally venture into clearcut areas for short periods of time.
In addition, Sadoway found that many bat species preferred mature forests, since they commonly roost in natural or excavated cavities in standing dead trees. Although some species are known to be able to adapt to roosting in cavities in built structures, clearcutting eliminates the original roosts without substituting any manmade alternatives, and hence eliminates bat habitat. Also, partially aquatic mammals such as mink and otter are adversely impacted by the hydrological impacts of clearcutting which reduce availability of prey.
Even selective logging may not be a panacea for the fragmentation problem, since it, too, causes habitat alteration to a degree. Pettersson et al. (1995) studied the effects of selective logging in Swedish boreal forests on canopy-dwelling invertebrates in an attempt to explain the decline of several species of non-migratory passerine birds in the area. Natural forests, they found, had significantly greater invertebrate diversity in their canopies, and nearly five times the invertebrate abundance. Differences were consistently observed in population levels of the large invertebrates (mainly spiders, and fly and butterfly larvae) upon which the birds in question habitually feed. The invertebrate population levels seemed to be linked to abundance of lichen.
Another Swedish study by Bader et al. (1995) looked at the effects of logging on wood-inhabiting fungi in spruce forests. Eleven sites were studied, with logging histories ranging from extensive to virtually none. The researchers found significant differences in species richness, and particularly in the numbers of certain threatened species of fungus, depending on the degree of human impact. Even forests that were selectively logged as much as 100 years ago showed a decline in fungal diversity. And while fungi on rotting logs may not be as charismatic as spotted owls or even martens, considering the important role played by fungi in nutrient cycling within boreal forest systems, any decline in their numbers or diversity is worthy of serious concern.
These factors are of particular importance when one considers that old growth habitat is much scarcer in Ontario than in the area that Harris studied. This is particularly notable in the case of red and white pine, which have declined to a mere 3% of Ontario’s productive forest lands, with old growth being an even smaller fraction. (WL 1995b) Given these proportions, and the level of uncertainty as to the long-term effects of current logging practices, Harris’s suggestion that within the Willamette National Forest in Oregon, 260,000 acres of old growth should be slated for long-rotation cutting would be cause for incredulity in an Ontario context. In regions such as Temagami, where the debate over old growth preservation is most heated, I believe that it is entirely reasonable to suggest that all extant old growth be protected.
In conclusion, however, I believe that Harris’s model could be adapted to provide an ecologically sound management plan for much of Ontario’s boreal forest, as well as transitional boreal/Great Lakes-St. Lawrence forest areas such as Temagami. But numerous modifications would be needed.
As discussed above, the hardwood conversion issue must be addressed. Simply using the cut-and-run techniques all too common in Ontario forestry with a longer rotation period would not be sufficient. Care must be taken that regeneration stands are of the same type that they are replacing. Shelterwood cutting, or strip or patch cutting (depending on the species and site conditions), the leaving and/or burning of considerable quantities of slash onsite, larger old growth cores, a reduction in fire suppression, and modification in logging techniques to avoid soil damage would all be helpful. Large scale clearcuts, whole tree harvesting, and the use of heavy equipment such as feller-bunchers should be discontinued immediately. In areas that have already suffered high levels of hardwood conversion, prescribed burning and replanting of indigenous conifers would be appropriate to redress the balance.
Attention must also be paid to ensuring connectivity between protected areas. As discussed previously, the “stepping stone” approach has its weaknesses; physically contiguous corridors are a better solution. Harris addresses this to some extent, suggesting that riparian strips be used as habitat corridors to connect old-growth islands with one another. (141-144) Given the existing network of rivers and small lakes in northern Ontario, this is an idea with excellent applicability. (Noss 1993)
There is also a serious need for further research on many of the dynamics of the boreal forest region, and on the effects of specific logging techniques in particular. There is a great deal that we simply do not know about how boreal forests work. Given the importance of the moss/fungal layer on the forest floor in nutrient cycling, it is vital that the effects of logging-related soil disturbance on these organisms be studied in more detail. The existing data from Swedish forests (see Bader et al. 1995) should be analyzed to see how it applies in the context of Ontario’s boreal region.
Most of all, it is vital that these concerns be addressed quickly. One of the most salient points in the reading I have done for this paper is how little we actually understand about the boreal forest — the largest forest system in the world. Almost every author, particularly in the Boreal Forest Conference proceedings (Sherman 1991) commented on the lack of knowledge concerning the area. But I think we can safely say that the current rate of logging, and its concomitant effects of fragmentation and conversion of forests, is unsustainable. We are conducting what amounts to a large-scale experiment on an ecoregion that covers most of this province, with virtually nothing in the way of a control group, and even less idea of what the consequences may be, for either human or nonhuman communities, if it fails. We must begin working toward a more in-depth understanding of this complex ecoregion, or we will lose something we have not even begun to truly understand.
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