Demographic Factors

Demographic limits to plant distribution include those factors that adversely affect recruitment or increase mortality. Demography therefore involves many factors that are not the property of species or populations but are instead a function of habitat and location (Antonovics et al., 2001). Thus geographic barriers to dispersal as well as the provision of microsite space within a habitat both come under this heading. The principles of Island Biogeography (MacArthur & Wilson, 1967) relate...

Human Settlement In Peripheral Areas

Adaptability is a feature of mankind, with the result that even the most marginal habitats are seldom devoid of human settlements. Furthermore, once having populated a peripheral area the community often appears reluctant to abandon what they have come to consider as their home territory, even when deteriorating environmental conditions have brought prolonged periods of hardship. Ecologically, the range of habitats in which prehistoric human settlements developed knew few boundaries. There is...

Carbon

Compared with animals plants lack variety in their basic resources, namely carbon dioxide and water. However, this does not mean that there is no element of choice available as to where these resources can be found. Given the relatively low levels ofcarbon dioxide now present in the atmosphere compared with some previous geological epochs, such as the early Carboniferous, and the Jurassic (when it might have been as high as 3000 ppm), it is not surprising that many species in marginal habitats...

Environmental Limits To Reproduction

Limits to plant distribution can arise either from a failure to grow or an inability to reproduce. In many cases a failure to reproduce may be a more common response to environmental limitations than a failure to grow, probably because reproductive success requires more than just the development of viable seed. Reproduction is accomplished only when there is successful establishment of a new generation of reproductive individuals. The continued existence of viable populations in marginal areas...

Flooding And Unflooding

Those species that live by the water's edge or in seasonally flooded communities are exposed to a double jeopardy in relation to the level of the water table. The first is flooding, and the second is unflooding. The physiological problems that can arise from the first stress include cellular dysfunction due to a reduction in metabolic energy (ATP) and an increase of cytoplasm acidity due to proton pump failure (cytoplasmic acid-osis), which can lead to rapid cell death. Oxygen deprivation...

Human settlement in reed beds

In southern Iraq the Shatt al-Arab Marshes and their reed beds that straddle the confluence and lower reaches of the Tigris and Euphrates rivers have also provided a habitat for marsh peoples that have preserved a unique way of life for the past 7000 years. The area is now shrinking as upstream dams and irrigation projects siphon off vast volumes of water and lower the water levels of the rivers. The marshes are highly heterogeneous. Some parts are permanent marsh while others are only flooded...

Carbon balance

The concept of carbon balance has a logical appeal when predictions are required for forest productivity in relation to changing climatic conditions. Increasing temperatures and higher levels of atmospheric carbon dioxide are climatic variables that demand an assessment oftheir likely effects on growth, photosynthesis, respiration, litter production and quality, soil respiration and other aspects of carbon sequestration in forests. As conditions become more severe with increasing altitude or...

Habitat Preferences In High Arctic Plant Communities

The flora of the High Arctic is made up predominantly of a series of coastal plant communities. There are of course plants on mountains. There are also many coastal nunataks (mountain tops that are not perman- Table 6.2. Examples of ancient, indigenous (autochthonous) species widespread in the Arctic Saxifraga oppositifolia S. hyperborea S. tenuis Ranunculus pygmaeus Dryas octopetala Loiseleuria procumbens Cassiope tetragona Diapensia lapponica (2n 26) (2n 26) (2n 20) (2n 16) (2n 18) (2n 24)...

Info

Garcilaso de la Vega (1608) The Royal Commentaries of the Incas. English edition (1869) by the Hakluyt Society, London. Gee, D. & Anderson, L.W.J. (1998) Influence of leaf age on responsiveness of Potamogeton nodosus to ABA-induced heterophylly. Plant Growth Regulation, 24, 119-125. Geoghegan, I. E. & Sprent, J. I. (1996) Aluminium and nutrient contents in species native to central Brazil. Communications in Soil Science and Plant Analysis, 27, 2925-2934. Gerloff, L.M., Hills, L.V. &...

Limits To Distribution

In many demographic studies, edge effects or boundaries have traditionally been regarded as merely 'nuisances'. Nevertheless, they can be modelled and investigated for the dynamic properties of populations at the edge of their distribution. Such studies can be used to provide graphic demonstrations that the distribution patterns of individuals at population edges have distinctive properties due to the influence of space on population margins. Processes occurring at the margin ofpopulations are...

Future uses for wetlands

Although the use of wetlands as a zone for marginal pastoral activity has declined there is increasing awareness of their value as 'the kidneys of the landscape' for their capacity to absorb wastewaters, disperse floods and detoxify organic wastes. The growth of wetlands in coastal habitats, which receive sediment loads from periodic flooding, can help to raise shorelines, especially where they are adjacent to salt marshes. If undisturbed, they remain one of the few true wilderness areas, where...

Endangered Species

Many countries publish lists as red data books of species that are in danger of becoming at least locally extinct. Such lists have prompted many studies into the ecology of these species in an effort to ensure their survival. In most cases the marginality of the species is due to the destruction of their habitat by human activity. In some cases the species have very narrow climatic and habitat limits which makes them highly dependent on the preservation of a restricted set of environmental...

Ecological Sensitivity Of Woody Plants To Oceanic Conditions

Sensitivity to oceanic versus continental conditions is found in many northern dwarf woody species (Crawford et al, 2003 Crawford & Jeffree, 2007). Oceanic conditions have long been known to lower both the altitudinal and latitudinal position of the treeline. It appears that this is also the case for a number of shrubby, woody species. The blanket bogs of Scotland and Ireland stand out as highly oceanic habitats. The basis on which the blanket bog vegetation is distinguished from less...

Future Prospects For Marginal Areas

In a time of climate change the problems of conservation are increased. Nature reserves as they are commonly constituted are usually centred on areas that are biologically outstanding, either as representing examples of valued plant communities or as sites that have a special interest for the species they harbour. Whatever the reason for the decision that brought about their designation they are normally classified as representing a recognized community. In the British cases this usually...

Subject index

Page numbers in italics refer to figures Abisko - northern Sweden 319, 322 acetaldehyde 287 post-anoxic generation 279, 297 tolerance 280 achlorophyllous species 90 acorn production 145 acrotelm 105, 277 active layer see also acrotelm 205 adversity selection 83 aerenchyma 98 aerobic metabolism 215 age and area concept 36 agriculture 24 Alaska air temperatures 202 reduced growth of black spruce 178 alcohol dehydrogenase induction by flooding 279 alder growth forms monocormic 301 polycormic 301...

Mycorrhizal Associations In Nutrientpoor Habitats

The role of mycorrhizal associations in plant nutrition increases with vegetation succession. As ecosystems develop and mineral soils give way to soils with increasing organic matter so does the importance of mycorrhizal associations increase for plant nutrition. There are three main types of mycorrhizae (1) endo-mycorrhizae, (2) ectomycorrhizae and (3) vesicular-arbuscular mycorrhizae (VAM). In endomycorrhizae, the fungus penetrates and lives within the cells of the root cortex and external...

Phenology

Examples of the necessity for appropriate timing of reproductive processes can be found in marginal areas from the poles to the tropics. The brief growing seasons of polar and alpine regions contain many examples of the necessity for prompt and precise phenological control in relation to flowering. Similarly, marginal areas in the tropics, such as lake and river margins, also provide examples where seedling establishment faces pheno-logical problems due to fluctuating environments. 4.4.1...

The Arctic As A Marginal Area

Types Vegetation Zones

The Arctic is possibly unique in being the northern hemisphere's ultimate peripheral habitat for it is here that continental convergence brings together the northern limits of the flora of three continents. The observation that in many polar areas some populations of plants are not fully self-sustaining has prompted the assertion that the Arctic as a whole should be considered as a marginal area (Svoboda & Henry, 1987). Such a concept implies that polar deserts and semi-deserts are marginal...

Variation In Peripheral Areas

The special nature of isolated or marginal and peripheral areas with regard to variation and evolution was first discussed in relation to tropical ants and gave rise to the recognition of the phenomenon known as ecological release (Wilson, 1959). Areas studied included savannas, monsoon forests, sunny margins of lowland rainforests and salt-lashed beaches. In ants, the expanding dominant species became adapted to such marginal areas, in which the relatively small numbers of (ant) species that...

Tundrataiga Interface

Climatic warming in northern latitudes will undoubtedly create new ecological opportunities for vegetation advance as ice sheets retreat and permanent snow cover is reduced and the climate extremes are reduced with a great degree of oceanicity (Fig. 5.27). For some species, however, particularly those that show a preference for continental climates there may be disadvantages from warmer winters, which are a marked feature of the current warming trend. Examination of potential changes in...

Acknowledgements

This book would never have been finished if it were not for the many colleagues and friends who have been willing to give me the time and benefit of their specialist knowledge. I am especially grateful to colleagues who have read particular chapters, Professor R.J. Abbott (St Andrews), Professor R. Br ndle (Berne), Professor F.-K. Holtmeier (M nster), Professor Ch. K rner Bale, Professor D. Tomback (Colorado), Dr L. Nagy (Glasgow), Professor S. Payette (Quebec) and Dr C. Vassiliadis (Paris)....

Km Guba

Fig. 5.6 (Above) Location of the northern limits to the boreal tundra forest and West Siberian Lowlands, as recorded by a Normalized Difference Vegetation Index (NDVI) satellite image recorded in May 1998 while the tundra was covered in snow. The snow-covered region does not register on the NDVI scale as there is no photosynthetically active visible vegetation. The evergreen forest emerging above the snow gives positive readings, shown by various shades ofgreen with the more intense colours...

Conclusions

Throughout the world, dwarf woody plants living beyond the treeline are a significant component of the vegetation. They are found in a wide variety of habitats from coastal heaths to upland and alpine moorlands. With human disturbance of forest regeneration, beginning already in the Neolithic, their geographical range has been greatly extended. More recently, the last hundred years has seen the so-called reclamation of these peatlands with deep ploughing and reseeding. In many of the remaining...

Oceanic mountain environments

Paradoxically, the greatest danger to mountain floras from rising temperatures is probably not to be found in continental mountains, as in the central Swiss Alps, but in mountains with oceanic climates. It might have been expected that oceanic mountains would be buffered against climatic change due to a reduction in annual temperature range. The relatively species-poor mountain flora of the Scottish Highlands and southwest Norway is considered to be due, at least in part, to the mild periods of...

Ice encasement and the prolonged imposition of anoxia

The probability of the imposition of anoxia on overwintering vegetation is probably higher in the Arctic than anywhere else on Earth. When snow melts and refreezes, or late rains fall on frozen ground, a thick covering of ice can result which can last from November until June. Temperatures are low under ice and metabolism will therefore be reduced. However, this does not mean that low temperature anoxia is not

Mean annual warming 0 C

Fig. 9.23 Cassiope hypnoides and possible responses to seasonal differences in relation to climatic warming. For explanation see Fig. 9.21. (4) The polar willow (Salix polaris), shown here for comparison, also exhibits differential effects between summer and winter temperature changes, with winter warming being the most disadvantageous and winter cooling the most advantageous for its presence in north-western Europe (Fig. 9.24). The maps in Figs. 9.21-9.24 offer insights into the possible...

Phenological responses of mountain plants

A question that always arises in relation to climatic warming, particularly in areas where spring can be late and the growing season short, is whether or not photoperiodic control of phenology will limit the use that plants might be able to make of earlier warmer springs. An experiment to answer this question in Austria on a number of high-elevation species (26003200 m a.s.l.) found that the number of days between soil thawing and flowering was sensitive to photoperiod in just under half of the...

PLANTSat the MARGIN

Ecological Limits and Climate Change Ecological Limits and Climate Change Plants at the limits of their distribution are likely to be particularly affected by climate change. Biogeography, demography, reproductive biology, physiology and genetics all provide cogent explanations as to why limits occur where they do. The book brings together these different avenues of enquiry, in a form that is suited to students, researchers and anyone with an interest in the impact of climate change. Margins...

Homeostasis And Treeline Stability

The ability to postpone the moment of death enables many trees to survive long enough to Fig. 5.24 Norway spruce (Picea abies) clonal group at an altitude of c. 450 m in Yllastunturi Fjell, Finnish Lapland (67 N). All the lower lateral branches contacting the ground and embedded in the litter layer and moss cover have produced adventitious roots. Seedlings on this exposed site are rare but occur at high density in the closed forest below. (Photo Prof. F.-K. Holtmeier.) outlive...

Genetic Boundaries

The use of molecular genetic markers has now opened up an entirely new dimension in our ability to trace the migration and development of plant populations, especially during the post-glacial vegetation re-advance into marginal areas. We now know that Britain received oaks, shrews, hedgehogs and bears from Spain, and alder, beech, newts and grasshoppers from the Balkans (Hewitt, 1999). In relation to marginal oceanic areas the postglacial history of oak is of particular interest. The...

Cambridge University Press

Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao Paulo Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title www.cambridge.org 9780521623094 R. M. M. Crawford 2008 This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place...

Plant functional types

The concept of categorizing plants into broad groups has a long history, beginning with Aristotle's disciple and successor Theophrastus of Erosos (c. 370 285 BC) who grouped terrestrial plants into three categories trees, herbs and vines. This process of categorization has continued with ever-increasing inventiveness, particularly in modern times, as some degree of rationalization is necessary, Fig. 3.19 The arctic poppy (Papaver radicatum). This specimen is growing at sea level at Mesters Vig...

Preface

Margins have long provided key questions for ecological investigation. Today with climatic warming becoming ever more apparent margins as regions of ecological change invite an assessment of their responses to environmental alteration. The purpose of this book is therefore to examine how marginal plant communities in different parts of the world are responding to climate change. Practically every aspect of modern biological enquiry can be used to address the nature of margins. Biogeography,...

Challenges Of The Maritime Environment

Coastal regions present both opportunities and challenges to plants. On one hand, reduction of temperature extremes, combined in many instances with freedom from frost and drought, extends the potential distribution for species that are intolerant of climatic extremes. On the other hand, the constant threat of habitat destruction, coupled with the physical stresses of wind exposure, salt drenching, burial and flooding, renders coastal regions marginal areas for many species (Fig. 7.1). Climatic...

W

Fig. 3.5 Iceland purslane (Koenigia islandica), a species limited by time for successful reproduction, growing in patchy moss communities in Iceland. This species, approximately 3 cm high (see 1 cm scale), is the only annual species to survive in the Arctic and for the size of the plant succeeds in producing relatively large seeds in a very short growing season. Fig. 3.5 Iceland purslane (Koenigia islandica), a species limited by time for successful reproduction, growing in patchy moss...

Preadaptation Of Plants In Marginal Areas To Climatic Change

There is an alternative hypothesis to consider in relation to marginal plant populations and their responses to climatic change. As climatic fluctuations are frequent in marginal areas regions the vegetation may be pre-adapted to climatic change. If this is the case the plant communities have to be robust in maintaining their identity and biodiversity and if they do migrate there may be a considerable lag phase before this becomes noticeable. The habitat tenacity of the arctic flora, and the...

Pleistocene History Of The Arctic Flora

6.4.1 Reassessment of ice cover in polar regions Past climatic histories mark out the Arctic as an area that has probably endured an unending series of Table 6.1. Climate and vegetation characteristics of bioclimatic arctic vegetation zones Table 6.1. Climate and vegetation characteristics of bioclimatic arctic vegetation zones

Responses To Shortterm Flooding During The Growing Season

Plants that are tolerant of short periods of flooding in summer tend to respond to oxygen deprivation in the opposite manner to that which can be seen in the over wintering organs of flood-tolerant species. Instead of down-regulating metabolism there is usually observed an acceleration of glycolysis. In the growing season this type of response can maintain tissues with an adequate supply of metabolic energy that gives the plant time to improve root aeration through the development of...

S

R. caucasicum x R. sochadzeae - outliers Fig. 4.12 Distribution of populations of the hybrid Rhododendron X sochadzeae and its parent species on Tiryal Dag in eastern Turkey. (Reproduced with permission from Milne et 4.5.3 Spartina anglica - common cord grass One of the most striking examples in Europe of hybridization leading to the creation of a new species with an ecological amplitude that is greater than either parent is that which arose between European cord grass (Spartina maritima) and...

Caff 431

Di Tomaso 92 Dickinson 267 Diemer 348 Diggle 137 Dodgshon 399 Dormann 317 Duncalf 366 Dunning 409 Edwards 6 Ehlers 208 Eiten 51 Ellenberg 354 Elvebakk 205, 206 Emmerson 251 Emms 120 Ennos 35 Eriksen 57 Eriksson 18 Erkamo 6, 7, 146 Erschbaner 348 Ewel 301 Fjeldsa 219 Fleisher 50 Fleming 334 Forbes 118, 319 Forchhammer 181 Fossitt 397 Fox 286 Frankel 33 Fredskild 324 Freedman 220 Freeman 151 French 251 Fries 5, 173, 218, 237, 314, 326 Fukao 279 Gaelic 225 Gamache 170, 171 Gansert 303 Garcia 328...

Vegetation Responses To Climate Change

An underlying question throughout this book has been whether or not marginal areas will be sensitive to climate change. Although treelines may be slow to advance, just as they are slow to retreat, there are many other species which have a capacity to invade and which may therefore readily migrate with a changing climate. Changes in both location and species composition of some marginal communities are one of the possible consequences of climatic change. A threat that cannot be ignored is that...

Adaptation To Habitats With Limited Resources

Avoidance or tolerance is probably the most apt description of the principal survival strategies that are associated with plants in marginal areas. Either the plants adapt to reduced access to light, nutrients, water or oxygen, or else they have some means of avoiding acute deprivation of these essential resources. Low growth rates and a diminutive size are the commonest responses. Genotypic variation resulting in populations adopting this minimalist approach is often particularly evident in...

I1111111

Fig. 1.9 (Above) The Swiss stone pine (Pinus cembra) growing as a timberline tree in the Alps with the Matterhorn in the background. The stone pine is an example of a tree which shows no signs of suffering a carbohydrate shortage even at its highest locations. (Below) Seasonal course of daily carbon balance and the net cumulative carbon exchange of an experimental Pinus cembra tree. The data were collected between 5 November 2001 and 31 December 2002. (Reproduced with permission from Wieser et...

Heathlands

The concept of heaths is of ancient origin. The word itself can be traced back to Old Saxon hetha and Middle High German Heide, meaning wasteland. The people who lived on the heath were the heathens (Gothic haithi) in the same way that plants that grow on the heath. The genera that constitute the heaths all belong to the Ericaceae (e.g. Erica, Calluna, Vaccinium, Empetrum (Figs. 9.4-9.8), Arctostaphylos, Cassiope, Andromeda, Ledum, and Loiseleuria). All these genera of dwarf woody shrubs that...

References

Aanes, R., Saether, B.-E. & 0ritsland, N. A. (2000) Fluctuations of an introduced population of Svalbard reindeer the effects of density dependence and climatic variation. Ecography, 23, 437-443. Aanes, R., Saether, B. E., Solberg, E. J., Aanes, S., Strand, O. & Oritsland, N. A. (2003) Synchrony in Svalbard reindeer population dynamics. Canadian Journal of Zoology-Revue Canadienne de Zoologie, 81, 103-110. Aas, B. & Faarlund, T. (2001) The holocene history of the nordic mountain birch...

Capacity adaptation

Marginal habitats frequently limit growing season length and reduce metabolic activity due to low temperatures. For many species these limitations can be overcome by the ability to increase metabolic rates at low temperatures by means of increased amounts of active enzymes, an adaptation which is referred to as Fig. 3.7 Capacity adaptation as a result of genotypic variation. Contrasting internal morphology of pairs of lowland (L) and upland (H) species in their development of leaf thickness and...

1

Reduction in Depletion of Accumulation of toxic Hydrolysis of Hormonal ATP generation carbohydrate metabolites cyanogenic glycosides dysfunction Fig. 8.4 An attempt at segregating the diversity of effects brought about by flooding on higher plants. Level 1 lists four ways in which flooding stress can impinge on plant growth and survival. In level 2 just one of these possibilities is subdivided, namely oxygen deprivation. Five different aspects of anoxic injury are then listed in level 3....

Latitude

Fig. 5.11 Arctic and subarctic treeline elevation as seen in the maximum elevation for the occurrence of spruce stands (forest and krummholz black circles) according to latitude from the continuous forest limit to the arctic treeline and the species limit in the tundra. The amplitude of the lowering of the subarctic treeline (red circles) is shown according to latitude. The shaded area corresponds to the topographic corridor of maximum and minimum ground altitudes according to latitude from 55...

Biodiversity At The Periphery

Biodiversity has now become an integral element in environmental monitoring. Much attention has been given in recent years to the species-rich areas of the Earth, as there is an obvious concern that regions that contain so much of the world's evolutionary heritage do not become biologically impoverished. There is, however, a strong case for giving attention to marginal areas in the preservation of biodiversity even if the numbers of species that they contain cannot compare with the biological...

Tropical Versus Temperate Trees In Wetland Sites

Outside the tropics most of these ultra-flood-tolerant swamp forests usually have either a relatively short winter or no winter, and trees do not have the stress of preserving an extensive root system in anaerobic conditions throughout long, non-productive winter periods. In the cold and cool-temperate regions of the world, particularly where the climate is oceanic, flooding is generally unfavourable for tree survival unless the ground is frozen during the period of potential inundation. The...

Im 200 300 400

Fig. 3.22 Carbon assimilation rate as affected by sex in male and female trees of box elder (Acer negundo) growing under common garden conditions. Plot of assimilation rate (A) as a function of intercellular CO2 concentration (ci) and the rate of oxygen evolution (right panel) for male (circles) and female (squares). Plants were well watered or droughted for 14 days then measured. Arrows of the A c curves show c at ambient CO2 of 353 ppm. (Reproduced with permission from Dawson et al., 2004.)...

Exploiting The Wetlands

Wetlands in cool temperate climates are a hindrance to agriculture, particularly in those regions of the world where there is a long winter. In tropical climates wetlands can be used for growing rice and in many areas swamp forests and bottomland forests provide excellent growing conditions for tree growth. In lands where there is a prolonged dormant season waterlogged soils are generally harmful to overwintering crops as well as being an obstacle to tilling and harvesting. Drainage has...

Man In The Mountains

Mountain peoples are outstanding throughout the world for their strong affiliation to their homeland, combined with a tolerance of an environment that is usually noticeably poorer in resources than in the adjacent lowland plains. Historically, mountains have provided a sense of independence to their inhabitants. The resulting long-term survival of groups of peoples in montane retreats has preserved the customs and languages of many ancient cultures from assimilation by larger and more powerful...

Availability In The Arctic As A Result Of Climatic Warming

No discussion of resource utilization by plants in marginal areas can be considered complete without some speculation as to the possible consequences of climatic warming. Particular attention has been given recently to this aspect of environmental change in relation to polar regions, which may be subject to substantial climatic warming. One of the most likely consequences of any substantial change will be an alteration in mineral nutrient availability (Chapin & Shaver, 1996 Wookey &...

Physiological Implications For Plant Survival On High Mountains

10.4.1 Water availability at high altitudes Water retention at high altitudes is highly dependent on topography and soil development, as well as on exposure and the seasonal distribution of precipitation. In common with other skeletal soils, such as sand dunes and deserts (see Section 7.1.2) the top surface is prone to desiccation and plants in these areas are dependent on being able to extract water from the deeper soil layers which are frequently absent in mountain habitats. The so-called dry...

Man In The Terrestrial Arctic

Human beings, as noted above, are no newcomers to the tundra. Late Palaeolithic hunters roamed over a landscape that enjoyed ecological conditions very different from those that exist in the tundra today. The warmth that caused the ice retreat after the Last Glacial Maximum produced higher temperatures at the icevegetation interface than those that now prevail. Consequently, there developed a more luxuriant vegetation, the tundra-steppe, which comprised a combination of plant communities...

Arctic Oases

In the Arctic it is possible to detect sites which in comparison to adjacent areas are relatively rich either in species or genetic diversity or both. Genera that show high species diversity at high latitudes in such areas include Salix, Saxifraga and Draba. Arctic species-rich hotspots, sometimes referred to as polar desert oases, include Peary Land, Devon and Ellesmere Islands as well as Bathurst Inlet (Figs. 6.20-6.24). The first polar oasis to be studied in detail was Truelove Lowland at 75...

G35

Biome During Last Glacial Maximum

2-3 layers, moss layer 5-10 cm thick, herbaceous dwarf shrub layer 20-50 cm tall, sometimes with low shrub layer to 80 cm. a Sum of monthly mean temperatures above 0 C. Source Based on Elvebakk (1999). extinctions, migrations and invasions. However, even at the height of the Pleistocene glaciations the Arctic was never entirely covered in ice. The extent of the Pleistocene glaciations in subarctic regions in western Europe (Fig. 6.11) can lead to an erroneous assumption that all the land north...

Isbn13 9780511393372 Isbn13 9780521623094

Cambridge University Press has no responsibility for the persistence or accuracy of urls for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. and all who inhabit, study and value marginal lands Fortunatus et ille, Deos qui novit agrestes Virgil, Georgics Book II

Plant Diversity In The Arctic

Cold climates do not feature frequently in discussions of biodiversity and the Arctic is normally not included in global maps showing sites of high plant biodiversity (Myers, 2003). Nevertheless, within the Arctic there is ample evidence of diversity within species and of the presence of recognizable subspecies (Table 6.4 Fig. 2.24). As discussed above (Section 2.1), peripheral populations, provided they are not isolated into populations of minimal size and subjected to genetic drift, can be...

Nutrient Retention In Marginal Areas

Iron Precipitation Ions Soil

Bryophytes and in particular the various species of Sphagnum that are common in wetland and oceanic regions have long been recognized as chelators of mineral ions. The rapid drop in soil pH after the colonization of wetlands by Sphagnum spp. is well known, Similarly, in many nutrient-deficient landscapes abandoned human settlements frequently stand out for the verdure of their immediate surroundings. The fifteenth-century abandoned Norse settlements in Greenland (c. 1450), Bronze Age and...

Produce A Tree And Show The Water Movement

Fig. 8.24 (A) Transverse section of sector of a 1-year-old alder stem red autofluorescence under blue light is due to chloroplasts in secondary cortex, secondary phloem, secondary xylem and medulla. Scale bar 200 mm. (B) As (A) but at higher magnification showing individual chloroplasts fluorescing red in secondary phloem and in secondary xylem ray cells. Scale bar 25 mm. (C) Sector of a 3-year-old alder stem showing red autofluorescence from chloroplasts in medulla and the inner two annual...

Coastal wetlands

Europe's largest coastal wetlands lie along the southern coast of the North Sea from Holland and North Germany through to the west coast of Denmark. The Wadden Sea, and its coastal marshes, are enriched by the effluent from the great rivers that cross the North German Plain, the Ems, the Weser, and the Elb. The highly productive marshes have a 7500-year record of human settlement which over the years has adapted to the considerable risks involved in harvesting the outstanding productivity of...

Sexual Reproduction In Marginal Habitats

4.2.1 Pre-zygotic and post-zygotic limitations to seed production Inability to reproduce sexually may arise from numerous causes, which can be grouped under two headings, namely pre-zygotic and post-zygotic limitations (i.e. before or after fertilization). Flower development may be prevented or delayed due to unfavourable environmental conditions. Even if a flower and receptive ovules are produced, pre-zygotic limitations may occur due to a lack of suitable vectors for pollination. If...

I

Lobelia Dortmanna

Synthesis of Preservation of Metabolism of adaptive enzymes membrane integrity anaerobic products Increase in relative use of pentose phosphate pathway Reversal of end stages of fermentation increase in role of glycolysis in maintaining ATP levels Fig. 8.5 Diagrammatic representation of the diversity of adaptations in higher plants that can contribute to their tolerance of flooding. (Reproduced from Crawford & Braendle, 1996.) Table 8.2. Summary of aspects of anaerobic physiology that impact...

Resource Acquisition In Marginal Areas

Tillandsia Peten

Strategy theories are devised to explain different modes of plant life in a manner which aids human understanding. Convenient and useful as these theories can be (see Chapter 2) they merely reflect human perceptions and inevitably discard information in the desire to produce conformity with a set ecological philosophy. One such dangerous simplification can be seen in the concept of environmental stress which is usually conceived as a permanent feature of particular habitats. Thus plants that...

Montane And Arctic Willows

As a genus, the willows are a widespread group containing approximately 400 species occurring mostly in the northern hemisphere. In the arctic and subarctic regions of Europe and North America there are approximately 28 boreal species with numerous subspecies and hybrids. However, only five of these species achieve circumpolar distribution, namely S. arctica, S. glauca, S. lanata, S. phylicifolia, and S. reticulata (Figs. 9.9-9.12 Hulten & Fries, 1986). The genus Saltx also stands out for...

Biased Sex Ratios

Male Biased Sex Ratios

Polar and warm deserts are marginal areas that are notable for a marked presence of dioecious species. In the Arctic, although the number of dioecious species is not significantly greater than the global average of 2-3 , the extent to which they provide a large degree of ground cover is very noticeable due to the ecological success of the various species of dwarf willow that grow at high latitudes. Observations of sex ratios in dioecious species often record a bias. A preponderance of males is...

Arctic Light Limitation

Ligusticum Scoticum Planting

U 00 ZOO MM 0 500 600 TOO 00 900 llM) 1100 l tKl Fig. 3.9 Change in stomatal density with altitude for V. myrtillus. (a) In situ observations. (b) Transplants from 200 900 m. (Reproduced with permission from Woodward et al., 2002.) U 00 ZOO MM 0 500 600 TOO 00 900 llM) 1100 l tKl Fig. 3.9 Change in stomatal density with altitude for V. myrtillus. (a) In situ observations. (b) Transplants from 200 900 m. (Reproduced with permission from Woodward et al., 2002.) Vaccinium myrtillus show an...

Assessing Biodiversity

Biodiversity is commonly understood to describe all aspects of variation in living organisms. To be scientifically meaningful, however, diversity has to be both qualified and quantified. The first requirement, qualification, refers to the level of assessment whether it be ecosystem complexity, species richness, or genetic variation. This last category, genetic variation, is the fundamental issue as it represents the only means of assessing the heritable properties that result from DNA variation...

Margins And Climate Change

Despite varying concepts as to what constitutes a margin, boundaries provide an opportunity for observing Fig. 1.2 Limes convergens as seen in two natural treelines in Patagonia at the frontier between Chile and Argentina (40 30' S 70 50' W). Below the snow-covered peaks can be seen an upper limit to tree survival with the deciduous southern beech (Nothofagus pumilio). Below is the upper limit for the evergreen Nothofagus dombeyi. Fig. 1.2 Limes convergens as seen in two natural treelines in...

Agricultural Margins

A striking feature of many early human settlements is the early date at which farmers settled in areas that would have been climatically peripheral for agriculture even under climatic conditions that were warmer than at present. Mesolithic and early Neolithic sites are to be found in northern coastal sites in Scotland and northern Scandinavia that must have been subject to a substantial risk ofcrop failure. Here and elsewhere Fig. 1.20 Early Neolithic settlement at the Scord of Brouster,...

Aspects Of Highaltitude Habitats

High-altitude environments vary geographically, meteorologically, geologically and also historically. Despite this heterogeneity, they nevertheless have certain features in common. Mountain summits are generally the coldest habitats in their particular region, prone to erosion (Fig. 10.9), with poor soils and widely fluctuating day and night temperatures as well as being exposed to strong winds and high UV radiation, and in the temperate, boreal and arctic zones a short growing period. The...

Acquisition of natural resources at high latitudes

Arctic peoples, who live off the land as opposed to the maritime food chain, have always had to contend with uncertainty in relation to their future food supplies. The unpredictable environmental fluctuations in the Arctic have profound effects on plant and animal populations. Polar animal populations constantly run the gamut from super-abundance to near extinction and back. The human race's intelligent provisioning for future needs is a particular advantage in combating the inherent variation...

Climates Orkney an oceanic exception

Living in proximity to the ocean clearly has both advantages and disadvantages for farming. For early settlers in north-western Europe the advantages of mild winters and warmer conditions for plant growth in summer in early Neolithic times were clearly advantageous both for pastoral farming and cropping. However, the development of heathlands and the growth of peat deposits subsequent to human settlement show that oceanic conditions can create problems for sustaining soil fertility, especially...

Boreal Forest Productivity At High Latitudes

The general question of whether or not trees are responding positively to climatic warming in boreal regions can elicit different answers depending exactly on whether the response is measured as a northward expansion of forest or an improvement in tree growth. In terms of forest expansion there is considerable inertia for movement in much of the tundra-taiga interface in response to climatic warming. The most noticeable advances appear to be a spread north in sheltered river valleys as seen in...

Cyclical Destruction And Regeneration In Coastal Habitats

Coastal Habitat Destruction

Coastal vegetation faces disturbance from rising sea levels and human disturbance on unprecedented levels. Under natural conditions the rich variety of coastal communities and the easy dispersal of propagules by sea has in the past enabled the plant communities of maritime habitats to recover from sea level changes and other natural disturbances. Probably the greatest danger to maritime vegetation will be the measures employed by human populations to save themselves from sea inundations,...

Impoverishment in oceanic regions

Ice Age Tundra

The absence of prolonged periods of frost in coastal regions results in the leaching of soils of their nutrients by high rainfall. On arable lands this is particularly severe in winter when the lack of plant cover deprives the soil of the principal means of nutrient retention. In areas near the sea drenching with salt spray can accelerate ion exchange and further deplete soils of nutrients. Nevertheless, for early farmers oceanic pastures made it possible to overwinter greater numbers of mature...

Future prospects for the tundra and its native peoples

The future looks uncertain for large-scale reindeer herding as developed over the last 200-300 years, and particularly so for the very large herds that were developed as a consequence of the collectivization that was enforced in Eurasia by Soviet Russia. During the 1960s the collectivization of herding brought the number of reindeer on the Chukotka Peninsula to over 100000, exceeding the capacity of the winter range (Krupnik, 1993). Consequently, the essential lichens were seriously overgrazed...

Marginal Areas And Conservation

Saltmarsh Conservation Grazing

When nature reserves are examined in detail it is often apparent that the greatest areas of species richness are localized. In many cases the regions with greater biodiversity are at margins or ecotones where one community merges with another. In the case illustrated above (Fig. 12.2) at the Tentsmuir Nature Reserve, the immediately visible loss from erosion was the disappearance of 10 m high dunes and replacing them with a deeply cut bay reaching back to where the shoreline had been almost a...

Resource Necessities In Nonproductive Habitats

Plant survival in exposed habitats with minimal resources frequently attracts attention for tenacity in an unpromising environment (Fig. 3.2). Despite impoverished soils, harsh physical conditions, and a lack of resources, such areas can provide habitats for a wide range of diverse communities (see Chapter 2). Plants vary enormously in their needs for resources and recognition of this phenomenon has been a driving force in the development of many ecological concepts including competition,...

Dwarf Birches Betula Nana And B Glandulosa

The dwarf birches Betula nana and B. glandulosa share the same propensity for hybridization as the mountain birches. Betula nana is circumpolar in distribution and represented by two subspecies ssp. nana in Europe and western Asia and ssp. exilis in North America and central and eastern Asia. Betula glandulosa is also a closely related shrub found across North America and Greenland, and where the two species overlap there is much hybridization as well as taxonomic confusion (DeGroot et al.,...

Polyploidy At High Latitudes

The distinction between long-term and short-term residence in the Arctic makes it possible to re-examine the properties that allow certain plant species to have a long history of survival at high latitudes. One characteristic which is particularly notable in arctic species is polyploidy. The Arctic is one the Earth's most polyploid-rich areas it is also noted for a high incidence of recently evolved polyploids (Brochmann et al., 2004). The frequency and level of polyploidy increases markedly on...

Longevity And Persistence In Marginal Habitats

Examples of long-lived trees can often be seen at treelines. The two species of bristlecone pines (Pinus longaeva and P. aristata) are probably the most famous of ancient trees that have survived for millennia on high ridges in hostile montane environments. Pinus longaeva is the best known from the Methuselah tree in California's White Mountains which has an age of over 4700 years (Fig. 4.39). The oldest known living Great Basin bristlecone pine had 4862 countable annual rings when it was cut...

Phenological Responses To Increased Temperatures

This account of arctic vegetation so far has been orientated towards a discussion of the likely long-term effects of climate change in the belief that for an ancient and heterogeneous arctic flora the main impacts of climatic change will be found at a population or species level. There is no doubt that phenotypic responses to increasing temperatures are already taking place. In the Arctic these have already been mentioned in relation to the profuse flowering by the purple saxifrage that can now...

Mutualism In Arctic Subspecies

Subspecies variation has been repeatedly noted as present in many arctic species (Table 6.2). A common explanation advanced for ecotypic variation is based on the need for plants to optimize their use of resources in response to competition. There is, however, an alternative interpretation for the frequency of ecotypic variation, which does not depend on competition and which has a particular aptness for the High Arctic situation where competition is minimal, and that is the increase in...

Transhumance

As a natural resource, mountains wherever they are have provided over the millennia one common feature that has aided the agricultural survival of mountain people, and that is the phenomenon of transhumance. The practice of seasonal migration with sheep and cattle to summer pastures in alpine habitats can be found across Europe and Asia. These summer grazings have their own specific names in many languages. In the Celtic world of Scotland and Ireland it is sheiling, in Norway saeter or stel, in...

Habitat Productivity And Competition

Dominant Plants The Arctic

A long-standing ecological question of particular relevance to resource utilization marginal areas is whether or not intensity of competition is a direct function of habitat productivity. It can be argued that as productivity rises so will the intensity of competition increase. The obverse situation would be that communities with low productivity are made up of species that have lower growth rates and therefore make lower demands on their habitat for resources and create communities with lower...

The Seed Bank

The seed bank is one of the most successful means employed by flowering plants to maintain populations in a wide range of habitats. Therophytes (annual plants) are entirely dependent on their seed bank for survival from one growing season to another. Many perennial species also have considerable banks of buried and viable seed which, depending on the species, have different expectations of longevity. Variation in the persistence of viable buried seed has prompted a classification of seed banks...

Climatic Change And Forest Migration

In the early Holocene, around 9000 BP, tree migration rates of 1 to 2 km yr have been reported both in Europe and Canada, causing a substantial and rapid reduction in the area of the tundra biome (Huntley & Birks, 1983 Ritchie, 1987 Huntley & Webb, 1988). However, since the passing of the Hypsithermal period, cooler weather has prevailed over the past 6000 years and this has been reversed only recently due to the current global climatic warming trend. Since the Hypsithermal temperature...

High Mountain Plants And Climate Change

Timberline Vegetation Mountains

Concern is often expressed for the future fate of mountain vegetation should there be sustained and marked climatic warming. The specific sources of danger fall into two categories (1) an upward migration of sedge heaths and forest that will eliminate the subnival and high-alpine communities from mountain summits (Grabherr et al., 1994) (2) the disappearance of snow patches and their associated species in the subnival zone (Guisan et al, 1995). In the Central European Alps the vertical extent...

Climatic Limits Of The Boreal Forest

5.2.1 Relating distribution to temperature Throughout North America and Eurasia trees reach a northern distribution limit, which can be compared with a number of thermal indicators. However, this does not mean that in all these areas the same natural processes are limiting the northern extension of boreal forests. Traditionally, the northern boundary of the boreal forest (the tundra-taiga interface) has tended to be considered as a purely thermal phenomenon. In North America this has been...

Genetic Invasion In Marginal Areas

Genetic invasion can be said to have taken place when hybridization leads to the substitution of the genes in a Fig. 4.15 The recently evolved Senecio hybrid species S. cambrensis (2n 60) flanked by its parents, S. vulgaris (2n 40) and S. squalidus (2n 20). (Photo Professor R.J. Abbott.) Fig. 4.15 The recently evolved Senecio hybrid species S. cambrensis (2n 60) flanked by its parents, S. vulgaris (2n 40) and S. squalidus (2n 20). (Photo Professor R.J. Abbott.) S. aethnensis X 5....

Trees By The

Two Mangroves Bahrain

Worldwide there are many areas where trees or even forests survive due to the combination of climatic amelioration, reduced competition and habitat protection from grazing and human disturbance that is found in many coastal habitats. Even in the exposed islands of the North Atlantic, sheltered gullies, protected from excessive sea spray, as on the upper areas of the cliffs, harbour a number of species that are more typical of woodlands, with large stands of the greater woodrush (Luzula...

Flooding Endurance

Scots Pine Water Edge

From the poles to the tropics water table levels and their fluctuations are powerful discriminators in plant distribution. Any body of water - a lake, a river or just a small stream - strongly influences the zonation of neighbouring plant communities (Figs. 8.1-8.3). The fringes of willow, alder, reeds, rushes and sedges that flourish at the water's edge provide striking evidence of the ability of certain plant species to survive in these marginal situations with ever-fluctuating water tables....

Light

There is no real alternative to light for flowering plants unless it is parasitism on other species. The dependence of parasitic plants on their hosts ranges from hemi-parasitism in chlorophyllous species such as the louseworts (Pedicularis spp.) and mistletoes (Viscum spp.). An arctic example is Pedicularis dasyantha shown in the frontispiece to this chapter (Fig. 3.1). Achlorophyllous species are obligate parasites entirely dependent on soluble sugars from their hosts for their energy supply....

Woody Plants Beyond The Treeline

Flower Cliff

Beyond the limits for the survival of forest, woody plants in shrub form exist as viable and even major components of ecosystems. Plants with lignified stems and branches can be found on mountains, moors, coastal heaths (Fig. 9.1), as well as across the tundra to the very north of Greenland and south to remote sub-Antarctic islands. The woody shrub or bush form is highly flexible and can be almost of tree stature as in krummholz pine or diminutive as in some arctic heather species (Figs....

Physical Fragility Versus Biological Stability And Diversity

The sight of major physical disturbance inevitably creates alarm and anxiety for the well-being of the biota. When widespread areas are devastated by fire or erosion these anxieties may be well founded. However, an area may be physically fragile and subject to periodic disturbance such as flooding, erosion, drought or insect attack yet nevertheless be biologically diverse as these episodic events often serve to reduce the presence of dominant species. Dune and slack systems are more diverse...

Northern Hemisphere Coastal Vegetation

Sand Dunes Embryo

The foreshore flora, although at the mercy of the sea, nevertheless derives from this perilous situation the advantage of oceanic seed dispersal. Consequently, beaches on either side of the North Atlantic from Quebec, Newfoundland and Labrador, to the northwestern shores of Europe have very similar strand-line plant communities dominated in summer by annual species such as orache (Atriplex spp.), sea rocket (Cakile maritima), and sea sandwort (Honckenya peploides) as a result of transatlantic...

Disturbance And Biodiversity

Greenland Vegetation And Wildlife

Disturbance has both positive and negative effects on species richness. Disastrous ecosystem destabilization through frequent burning, logging, and overgrazing can be found in every part of the world. The logging of tropical rainforests, the destruction of African savannas by elephants or fire, the denudation of Iceland from overgrazing by domestic livestock, and the destruction of arctic salt marshes by large populations of nesting geese, are but a few examples where repeated disturbance, from...