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...

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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...

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Fig. 3.14 Overwintering root respiration rate at a range of temperatures for four coastal species. (a) Ligusticum scoticum, a northern species, and Crithmum maritimum, a southern species. (b) Mertensia maritima, a northern species, and Limonium vulgare, a southern species. (Data from Crawford & Palin, 1981.) related to their latitudinal or altitudinal distribution. Intuitively, it might be expected that woody plants which devote a considerable part of their resources to the formation of...

Resource Acquisition In Marginal Areas

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

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...

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Mertensia Maritima Range

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,...

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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...

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 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

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...

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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...

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

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

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

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

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

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

Auroch Skeleton

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...

Global Shore Communities

Salt marshes and mudflats are soft shores and therefore vulnerable to both natural and human disturbance. Given a slow and steady rise in sea levels and an adequate input of sediment, it might be expected that mudflats and salt marshes will be able to grow apace with rising sea levels and provide a natural means of increasing coastal defences. If this were to happen it might offer some redress for the long-term reduction of salt marshes due to so-called 'land reclamation' and infill from...

Anoxia Tolerant

Saxifraga caespitosa S. oppositifolia S. foliosa Ranunculus sulphureus Cardamine nymanii Eriophorum scheuchzeri Juncus biglumis Carex misandra Luzula arctica Dryas octopetala Puccinellia vahliana Deschampsia alpina Alopecurus borealis Anaerobe Jar ANOXIA-INTOLERANT Saxifraga hieracifolia S. cernua Ranunculus pygmaeus Oxyria digyna Pedicularls hirsuta Cochlearia groenlandica Fig. 3.28 Experimental testing of anoxia tolerance in some High Arctic perennial species. The experiments were carried out...

Agricultural uses of wetlands

Mires, marshes and bogs have some of the highest levels of productivity to be found in any natural ecosystem. Although not generally part of mainstream agriculture they have long been skilfully diverted to human needs, particularly in areas of marginal farming. Marshes that dry out sufficiently in summer can provide grazing or in some cases a crop of hay. Well-managed water meadows Fig. 11.22 An Indian island dwelling on Lake Titicaca (3810 m). The present-day descendants of the Uro Indians who...

Man On Coastal Margins

In a world without roads coastlines provide convenient migration routes as well as access to the resources of the land and the sea. The early Mesolithic and later Neolithic coastal settlements that are found from the extreme north of Norway to the Atlantic islands of the Hebrides are a clear testimony to an early exploitation of the advantages of northern oceanic environments. The maritime conditions caused by the ameliorating influence of the North Atlantic Drift on Europe's north-western...

Amphibious Plant Adaptations

Most amphibious herbaceous species in temperate zones are either rhizomatous or tuberous geophytes (plants with their perennating buds below ground) and rely more on vegetative propagation than seed for regeneration. Seed germination is often very low in many amphibious species and successful sexual reproduction takes place only during periods of exceptional drought when water table levels have receded long enough for seeds to germinate and produce established juvenile plants. This restricted...

Mean annual warming 0 C

Podocarpus Totara

Fig. 9.24 Salix polaris and possible responses to seasonal differences in relation to climatic warming. For explanation see Fig. 9.21. than usual winter this species suffered lethal injuries. During a mild winter it was found that rehydrated shoots were at their greatest degree of cold-hardiness when tested early in winter and that they gradually lost their frost tolerance as the mild winter weather progressed. This loss of frost tolerance was accompanied by a decrease in the solute content of...

The Tundrataiga Interface

Will climatic warming allow the boreal forest to advance onto the treeless tundra This is one of the most tantalizing questions that can be asked in any discussion in relation to vegetation margins. The zone between the northern limit of the boreal forest (taiga) and the southern extent of the arctic tundra is the world's only circumpolar vegetation boundary and stretches for 13 400 km around the northern hemisphere and across three continents (Figs. 5.1-5.3). It is probably more exact to refer...

Past And Present Concepts Of Marginality

The concept of marginality in relation to land use varies historically. In the modern world, where local economies are affected by the existence of competitors in distant parts of the globe, the successful pursuit of agriculture depends on more than just the fluctuations of local environmental conditions. The concept of marginality in relation to modern land use therefore requires some elaboration. An area that may be marginal for wheat production may not be marginal for other cereals such as...

Defining The Arctic

Taiga Tundra Satellite

The Arctic is a large and heterogeneous area (Figs. 6.1-6.2) and it cannot be expected that all regions will respond equally to global warming. It is therefore necessary to define the Arctic and its major ecological regions. These divisions can be geographical, climatic, or ecological. Climatically, the Arctic can be considered as that region of the Earth's surface that is underlain by permafrost, or permanently frozen ground. This is not entirely satisfactory as permafrost underlies...

Life History Strategies

Life Strategy Ecology

The ability of less competitive species to survive when more aggressive species are hindered from reaching maximum productivity by environmental variation or uncertainty has long been realized as fundamental to species diversity. Many attempts have been made to look for combinations of adaptations or strategies that can be used to describe the manner in which different species respond to the pressure of competition for resources or interference from neighbours. The term strategy, when applied...

Establishment In Marginal Areas

Marginal areas present both advantages and disadvantages for seedling establishment as compared with more central situations. In many forests regeneration is often episodic as it is dependent on some form ofdisturbance or catastrophe to create space for the next generation. In the southern beech forests (Nothofagus dombeyii and N. pumilio) of south-central Chile the beeches at lower elevations are dependent on large-scale disturbance by landslides, blowdown, or even rooting by wild pigs. By...

Aquatic Graminoids

Rushes (Juncus spp.), sedges (Carex spp.) and reeds (Phragmites, Scirpus, Bolboschoenus) are among the commonest groups of species to be found at the edges of streams and lakes. The rushes (Juncus spp.) are also prevalent in poorly drained pastures. Despite their common occurrence in wet soils, rushes (Juncus spp.) are generally not tolerant of prolonged anoxia and the rhizomes of all species of this genus so far tested die after a few days of being placed in an anaerobic incubator. A notable...

Signs Of Change

We live in times of change and the impact of climatic warming can already be seen in many marginal areas. Effects that appear to be directly attributable to climate change are most noticeable in polar and alpine regions with the retreat of glaciers and snow and ice cover regions (Fig. 12.1). Coastal erosion as a result of rising sea levels is also having a noticeable impact. Archaeological rescue excavations of ancient coastal settlement sites exposed by erosion are now numerous. Several...

Agricultural sustainability in marginal areas

Marginal areas frequently show signs that their limited resources are being over exploited, or else managed in such a way as to cause a gradual and sustained deterioration of the environment. This is not a recent phenomenon. Evidence of soil exhaustion around early agricultural settlements is often noted in archaeological excavations. The proximate cause of abandonment around 1500 BC of an early settlement at the Scord of Brouster in Shetland (see Section 1.8) has been attributed to a...

Relict Species And Climate Change

Definition Relicit Species

Climatic change lies at the base of the restricted range of most relict species. Species that were once widespread and now exist in isolated 'islands' provide examples of a marginal existence that in many cases can be related to specific causes (Milne & Abbott, 2002). Not all relict species are in danger of extermination as some of the colonies that still exist, although only covering a fraction of their former distribution, frequently contain populations that are both numerous and viable in...

Recent developments in bog cultivation

An increase in the demand for fruit juices in a modern health-conscious world has caused a marked increase in the use of bogs for the cultivation of cranberries. The American cranberry (Vaccinium macrocarpon) is indigenous to northern America where it grows naturally in acid peat bogs and has a distribution that includes areas that are prone to frost at any time of the year. Commercial cranberry production started in the mid nineteenth century and is now a major industry occupying about 14 000...

Physiological Adaptations In Coastal Vegetation

Rich Pinea

Tolerance of drought and the ability to regenerate in disturbed sites are two of the outstanding features of sand dune vegetation. Many of the moss and lichen species, which hold the surface of the sand dunes, have the remarkable property of being able to allow their tissues to dry out without losing viability. After prolonged periods of desiccation (e.g. lying on a herbarium sheet for 70 years ) some moss species begin to resume metabolic activity within 30 minutes of gaining access to water....

Mountain Birches

The term mountain birches encompasses a diverse taxo-nomic group which can be defined most easily in terms of growth habit and location. Mountain birches are distinguished from all other birches by their ability to live in the alpine or subarctic zone above the treeline and have the potential to adopt the many-stemmed growth (polycormic) habit as opposed to the pole form (monocormic). The silver birch (Betula pendula) grows only as the pole form, which in Scotland requires a minimum of 1100 day...

Flowering In Arctic And Alpine Habitats

Individual Organisms The Tundra

Like deserts after rain, arctic and alpine habitats are also noted for their remarkable floral displays. The diminutive nature of plant vegetative organs in these marginal areas is not accompanied by a proportional reduction in the size of the flowers. Consequently, summer flowering displays are highly visible. Despite the abundance of flowers that is often found in montane and arctic habitats, it is necessary to determine the effectiveness of sexual reproduction, first in producing viable seed...

Reproduction In Marginal Habitats

Clonal reproduction is particularly suitable for plants in marginal areas and there are many examples of relict species where their continued survival appears to be due largely to being able to reproduce through clonal spread and fragmentation. It is therefore not surprising that marginal areas, whether they be on mountains, or at high latitudes, or in more widespread temperate habitats such as riverbanks and lakesides, are frequently rich in clonal species. Clones enable plants to resist...

Hybrid Zones

A hybrid zone is created when hybrids between two taxa flourish in the marginal area (hybrid zone) that lies between two parents and is more common with plants where fertility barriers are weaker than in animals (see below). Marked environmental gradients such as those that occur in relation to exposure (e.g. near the sea, or in zones of varying flooding frequency, or across altitudinal zones on mountains) create marginal sites where hybrids can be more frequent than either parent. Examples of...

Woody Plants Of The Tundra

The tundra is commonly described as treeless. Trees growing upwards with a clearly visible trunk are only found in isolated pockets near the tundra taiga interface (see Chapter 5). However, this does not necessarily exclude the presence of woodlands in the tundra. Whether or not trees can be considered to be present in polar regions is merely the imposition of an arbitrary human judgment. Willows that grow upwards in the temperate zone survive better in the Arctic if their trunks lie flat along...

Responses To Longterm Winter Flooding

Less attention has been given to understanding the consequences of high water tables in winter than during the growing season, possibly because the study of flooding tolerance has been strongly influenced by the need for research on annual crop plants. The relative neglect of winter studies into flooding tolerance is also possibly due to the erroneous assumption that marsh and bog plants owe their ability to survive entirely to their capacity to aerate their submerged organs by the downward...

Terrace farming

Although use of upland areas in Europe is declining there are other regions of the world where mountainsides are used intensively for agriculture, usually due to Fig. 11.28 Terraces on the mountain below the Lost Inca City ofMachu Picchu near Cuzco (Peru). The development ofterracing in Andean agriculture reached its peak in the Inca Empire and produced a form of mountain horticulture that has never been surpassed in terms of soil and water conservation. (Photo Barbara Crawford.) Fig. 11.28...

The Geography Of Marginal Plant Diversity

In terrestrial plant communities species richness in terms of alpha diversity generally decreases from the Equator to the poles. It is therefore understandable that biodiversity studies are frequently concerned with species assemblages at low latitudes. Conditions that limit plant distribution and create marginal areas can also be expected to influence biodiversity. Globally, tropical rainforests are commonly considered to be the Fig. 2.12 Heather burning on a Scottish moor. Burning mature...

Altitudinal Limits To Plant Survival

High Altitude Mountain Plant

Plants that live at high altitudes demonstrate a remarkable ability to survive in some of the most challenging environments on Earth. The permanent snowline is generally taken as marking the principal upper altitudinal limit for flowering plant colonization (Fig. 10.2). There are however, peaks or horns of rock that rise above the snow, ice fields known internationally by the Inuit term nunataks where plants can manage to live above the snow. These emergent mountaintops have sides that are too...

Reproduction In Hot Deserts

4.7.1 Diversity of plant form in drought-prone habitats The flowering plants of warm deserts include every variety of life-form (Figs. 4.21, 2.22). Desert floras contain trees and shrubs, as well as annual and perennial herbaceous species. Although none of these groups is excluded as a result of drought not all are visible at any one time (see also Section 3.6.2). The relative contribution of each life-form to desert communities differs depending on the particular conditions of each desert in...

Plant Diversity In Drylands

Prosopis Juliflora Tree

The ability to withstand long periods of moisture shortage is not a prerogative of any one plant group or life-form. In trees, shrubs, grasses, ferns, mosses and lichens there are species which are drought tolerant (Figs. 2.21-2.22) and others which are restricted to areas of plentiful water. This evolution of drought-resistant species in all the major life-forms of plants is sometimes overlooked as it is easy to be deceived by the dramatic changes in vegetation that take place when passing...

Mountaintop Isolation

Precambrian Period Climate

High mountain peaks, wherever they lie, from the poles to the tropics, with or without snow, are places of isolation for plant life. Lacking the mobility of most birds and animals, the plants that grow in these upper altitude zones are confined there for life (Fig. 10.5). In temperate and tropical regions, the slopes and valleys below the mountain peaks or tablelands will usually be covered in a vegetation type that belongs to a totally alien environment as compared with the region above the...

Zonation Case Studies

Comparison Alps Himalaya

The definition of alpine vegetation as the plant communities that are found between the upper limit of tree growth and the snowline (nival zone) is used globally. As might be expected in any global categorization many differences can be found between the species that inhabit this broad zone in various parts of the world. Variation in the alpine environment is not just a question of temperature reduction with increasing altitude. Aspect, exposure, snow cover and water availability also play a...

Species index

Page numbers in italics refer to figures Acorus calamus 88, 88, 158, 277, 281, 287, 295-297, 298, 300, 300 Aegiceras corniculatum 261, 261 Aetoxilon punctatum 114 Agave americana 66 Alces alces 37 alders see Alnus spp. Alkanna orientalis 56 Alnus fruticosa 193, 194 Alnus glutinosa 103, 302 Alnus incana 103, 321 Alnus japonica 229 Alnus rubra 103 Alnus spp. 199, 301, 303, 312 Ammophila arenaria 130, 130, 234, 235, 238, 239, 250, 263, 264 Ammophila brevigulata 238, 264 Ammophila spp. 238, 239...

Juniper

Juniper (Juniperis communis) is a highly polymorphic species with a widespread circumpolar distribution. Juniper, like willow, is dioecious. It is a wind-pollinated shrub or small tree and produces cones which develop into berry-like fruits which are readily dispersed by birds. Several subspecies are commonly recognized, which together with intermediate forms provide a source of extensive genetic diversity. As a genus, the junipers are slow-growing conifers of marginal areas as they can survive...

Mast Seeding

Tussock Grass Non Polar Alpine Regions

Mast seeding in trees, with a synchronous super abundance of fruit and seed production by certain species over an extensive geographic area at irregular intervals, is a familiar concept. Less well known is the fact that masting (or mast fruiting) behaviour can also be found in marginal areas in a number of herbaceous species. Despite the striking floral displays that can be observed in early summer in most alpine habitats not all alpine Fig. 4.29 A stand of the tussock snow grass Chionochloa...

Ffd First Flowering

Mastadon Locations

Fig. 4.24 A triangular ordination of flowering phenology in 80 species from Latnjajaure, Swedish Lapland. FFD, first flowering day Julian day number PI, phenology index E, early L, late and D, delayed. The dates when 10 , 50 , and 90 of the valley is snow free are inserted as lines. The dotted circles represent two species each. Abbreviations Aa, Arctostaphylos alpina Aba, Arabis alpina Ana, Antennaria alpina Bn, Betula nana Ca, Cerastium alpinum Cb, Cardamine bellidifolia Ch, Cassiope...