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5 - Fauna
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 16 September 2009
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- 06 January 2000, pp 125-174
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Summary
Cliffs worldwide support a variety of protists and animals including a vast array of invertebrates, amphibians, reptiles, birds and mammals. Cliffs in one area of highland in southern British Columbia, Canada, for example, supported 41 per cent (22 of 54) of the faunal species of high conservation value for the region (Sinnemann, 1992). Most studies of cliff fauna, however, have focused on one or a small number of species. This is in striking contrast to the floristic studies reviewed in the last chapter that generally focused on the determination of the composition of the entire plant community. In most faunal studies, the focus of the research is usually not on the habitat but rather directly on the species that occur there. Exceptions to this trend in the faunal literature include Johnson (1986), Reitan (1986), Ward and Anderson (1988), and Camp and Knight (1997). As a result, the organization of this chapter is quite different from the preceding one. This chapter summarizes the information that is presently available in the scientific literature on the ecology and distribution of faunal cliff species and presents it in broad taxonomic groups.
Avifauna
General trends
Cliffs appear to support a greater species richness of birds than equal areas within the surrounding habitat, although not all of these birds nest on the cliffs. This difference between adjacent land and cliffs is partly attributable to cliffs being ‘permanent habitat edges’ characterized by abrupt changes in soil, topography, geomorphology and microclimate combined with local conditions that minimize interspecific competition and predation (Matheson & Larson, 1998).
2 - Geology and geomorphology
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 16 September 2009
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- 06 January 2000, pp 19-42
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Summary
In most discussions of terrestrial ecology, the weathering patterns and age of the bedrock are an important part of the ecological context. This is especially true on cliffs where soil formation is either absent or minimal and there is direct contact between the rock face and the biota at all times. On level ground, the underlying geology becomes less critical and the processes of soil formation more critical to plant and animal communities over time (Oettli, 1904). The persistence of the contact between the biota and the rocks on cliffs (most often without soil) makes it necessary for us to present a broad summary of the important geological and geomorphological characteristics of cliffs which may influence the abundance and distribution of the biota on the surface.
Bedrock composition and strength
The emergence of cliffs in the landscape is dependent on both the mechanical strength and the variability in the strength of the bedrock. These traits are built into the rock, both during the initial deposition of the materials and in the subsequent reshaping of the strata by crustal plate movement and large-scale geomorphological events such as glacial advances or the outflows from rivers. The variability built into different strata results in differences in the physical expression of weathering processes, with the removal of weaker materials and the retention of stronger ones. The pronounced series of cliffs interrupted by talus slopes lining the walls of the Grand Canyon, USA, is caused in part by this vertical mgeological heterogeneity in wear resistance (see Fig. 1.2).
3 - Physical environment
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 16 September 2009
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- 06 January 2000, pp 43-78
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Summary
The vertical orientation of cliffs represents the primary (if obvious) difference from other landscape types, but verticality affects the environmental conditions on cliffs in a number of important ways that are not always obvious to ecologists who study the microclimate of level ground or slopes. The function of this chapter is to point out the various ways in which the physical environment of cliffs is distinct from that of horizontal surfaces. Its purpose, therefore, is not to give a complete account of all components of the physical environment. The reader is referred to standard texts, such as Monteith and Unsworth (1990), Arya (1988), Oke (1987) and Gates and Schmerl (1975), for basic information on microclimate and energy balance.
The first subsection briefly outlines the various components of the physical environment that are affected by vertical orientation of the substrate, and shows how these factors are interconnected in a complex way to make the cliff environment drastically different from surrounding level ground. More detail on each of these factors is then provided in the subsections that follow.
The effects of vertical orientation
Vertical orientation affects the total amount of direct radiation a surface receives and the way radiation input varies diurnally, seasonally and latitudinally. It also affects wind speeds on the surface and the amount of direct precipitation received. Radiation, wind and moisture together control the temperature of the rock. Absorption of radiant energy increases rock temperature, while wind speed controls the amount of energy that is dissipated by the heating of air and the evaporation of moisture, thus cooling the cliff surface.
4 - Flora
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 16 September 2009
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- 06 January 2000, pp 79-124
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Cliffs are largely inaccessible to people and their livestock and are therefore generally free from disturbances such as grazing and fire. As we have already shown, cliffs cannot support organisms with high productivity and therefore most vegetation on cliffs is small and unassuming. We believe that these features are the reasons why cliffs have attracted far less attention from biologists than other more accessible habitats with large numbers of productive macroscopic organisms. Maycock and Fahselt (1992) studied the vegetation of high arctic cliff faces and scree slopes in Canada that had previously been described as ‘unvegetated’. On these surfaces they found 156 plant species, of which half were lichens, one-quarter were macroscopic higher plants and one-quarter were bryophytes. The authors offer no satisfactory explanation as to why others might have so grossly misrepresented the diversity of species in these habitats, but they hint that the appearance of low productivity has discouraged close scrutiny in the past. The same suggestion was also offered by Larson (1990) to explain the lack of prior discovery of an ancient forest of stunted Thuja occidentalis on the apparently bare cliffs of the bare-looking Niagara Escarpment in southern Ontario, Canada. The small size of many cliffs often results in them being viewed as ‘break-points’ or transition-points in landscapes, rather than as separate landscape elements. This view leads to the characterization of cliffs as the ‘edges’ of other places, rather than places in their own right.
We feel that all of these factors help to explain the small amount of scientific literature dealing with the vegetation of cliffs compared to the vast amount of literature on level-ground forests, grasslands, wetlands, deserts, and tundras of the world.
1 - Introduction
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- 06 January 2000, pp 1-18
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Summary
In the six decades since Sir Arthur Tansley first coined the word ecosystem, an enormous amount of ecological research has been carried out in every imaginable habitat on earth. Forests, grasslands, deserts, tundra, wetlands and oceans have all been mapped in their distribution on the earth's surface and have revealed their structure and some aspects of their function to ecologists. Until recently, however, vertical cliffs have been almost completely overlooked as subjects for ecological study, even though some workers in Europe have included areas of steep rock in analyses of vegetation communities. For example, McVean and Ratcliffe (1962) described plant communities for the Scottish highlands but only a handful of stands had slopes greater than 60° and only one had a slope value of 80°. In other words, cliffs as defined in this book were not really included even if subsequent authors said that they were. McVean and Ratcliffe were also aware of the difficulty in dealing with cliff vegetation at the community scale. They stated:
To many botanists this heterogeneous cliff vegetation is the most interesting of all but to the phytosociologist it is easily the most baffling. The larger, stable ledges usually bear tall herb communities and are amenable to the normal method of analysis but the open and patchy vegetation consisting of small herbs, sedges, grasses and bryophytes is very difficult to describe. … We have therefore analyzed only those cliff communities which provided stands of at least the normal minimal area of 2 × 2 m. … Description of the micro-communities naturally confined to open rocks is best reserved for detailed studies of individual rupestral species.
(McVean & Ratcliffe, 1962, p. 88)
8 - Summary, opportunities and synthesis
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 06 January 2000, pp 283-301
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To a very great extent, cliffs are places that are of interest to everyone and no-one at the same time. This paradox attracts us and we think it will attract others when it becomes better known. People on all continents see images of cliffs in a wide variety of mass media and are consequently drawn as though pulled by a magnet to cliffs or habitats with extreme topography. Cliffs are sites with enormous spiritual value and may even be habitats that have given rise to a wide variety of our food plants, garden weeds and commensal animals. Yet these same sites have zero area when photographed from space, have attracted little scrutiny from scientists, and have received almost no legal protection from various forms of commercial exploitation. Some may be inclined to protest the last two statements based on the content of the book so far, but when one compares the vast and easily accessed literature for other habitat types, our conclusions are justified.
The literature that we have reviewed and discussed in the preceding chapters almost always focuses on particular organisms, groups of organisms or specific aspects of cliff ecosystems without considering them as ‘places’ in the same way as lakes are considered as distinctive habitats by limnologists or forests by forest ecologists. A result of the particular organization that we have selected is that we may have reinforced rather than eliminated the idea of separate structures and functions on cliffs.
Contents
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- 06 January 2000, pp ix-xii
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6 - Controlling processes
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 06 January 2000, pp 175-246
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While inaccessibility has protected cliffs from significant amounts of disturbance, it has also limited the amount of experimental work that deals with questions of the genesis and maintenance of cliff communities. Most previous studies have inferred mechanisms of community or ecosystem function from descriptions of the cliff biota. In this chapter, literature on the growth of individual species and populations, the establishment of patterns of relative abundance, and the development of species composition is briefly reviewed. Ideas about how physical factors influence the biota of cliffs are presented first, followed by a discussion of the control of communities through biotic interactions.
Bedrock composition
There are three aspects of geology and geomorphology that influence the biotic communities of cliffs: bedrock composition, structural heterogeneities, and erosion. Bedrock composition falls into three large categories: (1) hard siliceous rocks, mainly of igneous origin but also including some sedimentary rocks such as sandstones; (2) hard calcareous rocks, mainly of sedimentary origin but also including igneous or metamorphic rocks such as basalt and marble; (3) unconsolidated or indurated materials such as sand, gravel or loess. It is generally known that siliceous rocks produce acid soils that select for an array of plant species commonly called calcifuges (‘lime avoiders’). Conversely, calcareous rocks produce chalky soils with neutral to high pH values that select for a different array of plants known as calcicoles (‘lime seekers’) (Fitter & Hay, 1987). The low pH values of soils derived from acid rocks cause the accumulation of toxic levels of Fe2+/Fe3+ or Al3+ ions.
Frontmatter
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 06 January 2000, pp i-viii
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Cliff Ecology
- Pattern and Process in Cliff Ecosystems
- Douglas W. Larson, Uta Matthes, Peter E. Kelly
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Cliffs are present in virtually every country on earth. The lack of scientific interest in cliffs to date is in striking contrast to the commonness of cliffs around the world and to the attraction cliffs have had for humans throughout history. Cliffs provide a unique habitat, rarely investigated from an ecological viewpoint. This book aims to destroy the impression of cliffs as geological structures devoid of life, by reviewing information about the geology, geomorphology, microclimate, flora and fauna of both sea and inland cliffs. For the first time, evidence is presented to suggest that cliffs worldwide may represent an invaluable type of ecosystem, consisting of some of the least disturbed habitats on earth and contributing more to the biodiversity of a region than their surface coverage would indicate.
Index
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- 06 January 2000, pp 331-342
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7 - Interactions with humans
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 06 January 2000, pp 247-282
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The attraction of humans to cliffs is not new. Cliffs have often formed the subject matter for visual arts and sculpture, particularly in China, Japan and Korea, where cliffs have always evoked strong emotional feelings (Fig. 7.1). The human population has always been fascinated with mountains, rock outcrops and cliffs. In many ways, this interest is a practical one, for cliffs and caves at their base have always offered protection and shelter from the elements and from rival populations of humans competing for similar resources. Hominid fossils from Homo erectus to Homo sapiens neandertalensis have been collected from caves at the base of cliff sites in Africa, Asia and Europe (Hoebel, 1966; Jurmain et al., 1990) including Mt Carmel, Israel (Fig. 7.2). It is impossible to claim that cliffs and the caves within them were actively sought more than other habitats by palaeohumans because cave environments preserve artifacts that would rapidly degrade if exposed directly to weathering. Despite this, cave dwellings in Greece and other locations around the Mediterranean and into central Asia span the time period within which agriculture was started (Bogucki, 1996), and at the very least caves and the cliffs above them were sought out by humans as sites for occasional dwellings, tool manufacturing, and animal carcass reprocessing (Schepartz, personal communication). These sites include abundant remains of early tools and, later, evidence of fire. Similar sites in southern France (Ruspoli, 1987) are well known for abundant cave paintings made prior to the last glacial advance.
Acknowledgements
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 06 January 2000, pp xv-xviii
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Preface
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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We have given ourselves the assignment of trying to write a book about places everyone sees, but no-one knows. In completing the work, we have tried to keep a number of things in mind. First, we recognize that readers have an insatiable curiosity for the truth, and within the context of natural history and ecology this is especially true because the answers to questions about non-human taxa sometimes help us interpret the significance of Homo to the world. This can comfort us. Second, we acknowledge the message that ‘complex questions have simple, easy to understand, wrong answers’. Thus, the kinds of simple questions we ask may not provide simple answers, and in the work that follows we will try to simplify only when such efforts can provide reasonably precise and accurate versions of the truth. Given that this is the first book on the topic of cliff ecology, it may also happen that certain topics have been so understudied that no effective summaries or syntheses can be made. When problems like this are encountered, we will try to bring them to the reader's attention. Lastly, we will try not to misrepresent to the reader the source of the motivation for doing science in general, and cliff ecology in particular – we love cliffs. Sometimes in the writing of science these motivations become lost in the intricacies of logic. You all know the wording: ‘In order to test whether species packing densities could be predicted from the equilibrium theory of island biogeography we sampled …’ which translates into English as ‘islands are fascinating.’
References
- Douglas W. Larson, University of Guelph, Ontario, Uta Matthes, University of Guelph, Ontario, Peter E. Kelly, University of Guelph, Ontario
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- Cliff Ecology
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- 06 January 2000, pp 302-330
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