Published on January 3, 2008
Biomes: Biomes Developed by Adam F Sprague Biomes : Biomes A major biotic community having well-recognized life forms and a typical climax species. Slide3: The terrestrial world is characterized by distinctive assemblages of plant species. Examples are the temperate forest around Marietta, the tropical rain forests of South America and Africa, the tundra of northern Canada, the taiga of Siberia. We use plant species to distinguish biomes because they are immobile and long-lived (at least the trees). If you used, say geese, to characterize the taiga, what would you do when they flew south in the winter? The characteristic plants which define each of the biomes constitute part of what is known as the climax community. The types of plants that characterize each biome have evolved to the unique climatic conditions in that part of the world. If such a community is destroyed (by fire, logging, plowing, etc.) - and then left alone - the biome will regenerate itself over a period of time. It will go through a number of intermediate stages until it reached the climax stage again. This process is called succession. Succession : Succession orderly succession of communities to a climax community (biome) sequence of communities --> sere each transitory community --> seral stage For instance, in Ohio, a simple description of a sere that would develop on an abandoned field might be: grass -> shrubs -> trees -> oak-hickory forest In this sere, the grass is the pioneer community and the oak-hickory forest is the climax community. Each step in the sere (grass, shrubs, trees, oak-hickory forest) is individually known as a seral stage. There are two main types of succession: 1. Primary succession : 1. Primary succession begins with bare rock exposed by geologic activity example sere: rock -> lichen -> moss -> grass -> shrub -> trees -> oak hickory forest 2. Secondary succession : 2. Secondary succession begins on soil from which previous community has been removed (by fire, agriculture, etc.) old field succession example sere: grass -> shrub -> trees -> oak hickory forest secondary succession can proceed much faster because the soil has been prepared by the previous community General trends in succession: : General trends in succession: Early seral stages are highly productive but require large inputs of nutrients and also tend to lose nutrients. Biomass increases, but there is low productivity and fluctuations in biomass are common. These seral stages are dominated by "weedy" or "r-adapted" species which reproduce quickly, but often die young. Most of their energy goes into reproduction. There are relatively few species in early seral stages. Climax seral stages are much more complex, with many species. They create a favorable environment for many species. Biomass does not fluctuate, and decomposition rates are roughly equivalent to new production. Nutrients are cycled efficiently, and rarely leave the ecosystem. Individual organisms are longer-lived, since they invest more resources in themselves and less in producing offspring. General trends in succession cont.: General trends in succession cont. A recently cleared field is an example of an early seral stage. It is colonized by grasses and other plants that produce many seeds, such as many annuals. These plants may live only one year, set seed, then die. The organisms in the field will not be able to cycle all of the nutrients, and many nutrients will run off with rainfall. On the other hand, the climax forest is characterized by trees, which are long-lived. There are many species, and each provides living space and food resources for other plants and a host of animals. Decomposing materials are recycled; few escape though the waters of the forest streams. If one farms in a rain forest, the community is moved from a climax community to an artificial community which resembles an early seral stage. The farm field will lose a lot of nutrients, something that tropical soils do not have in abundance. The land will be useless for farming in a few years. This table summarizes the differences between pioneer and climax communities: : This table summarizes the differences between pioneer and climax communities: Productivity of biomes: : Productivity of biomes: Biomes vary in their productivity (the amount of effective photosynthesis per year). These are the biomes, in order of their productivity (highest first) estuaries and tropical rain forest temperate forest agricultural land temperate grassland lakes and streams coastal zone tundra open ocean desert To understand the nature of the earth's major biomes, one needs to learn for each: : To understand the nature of the earth's major biomes, one needs to learn for each: The global distribution pattern: Where each biome is found and how each varies geographically. A given biome may be composed of different taxa on different continents. Continent-specific associations of species within a given biome are known as formations and often are known by different local names. For example,the temperate grassland biome is variously called prairie, steppe, pampa, or veld, depending on where it occurs (North America, Eurasia, South America, and southern Africa, respectively). The general characteristics of the regional climate and the limitations or requirements imposed upon life by specific temperature and/or precipitation patterns. Aspects of the physical environment that may exert a stronger influence than climate in determining common plant growthforms and/or subclimax vegetation. Usually these factors are conditions of the substrate (e.g., waterlogged; excessively droughty, nutrient-poor) or of disturbance (e.g., periodic flooding or burning). The soil order(s) that characterize the biome and those processes involved in soil development. The dominant, characteristic, and unique growthforms; vertical stratification; leaf shape, size, and habit; and special adaptations of the vegetation. Examples of the last are peculiar life histories or reproductive strategies, dispersal mechanisms, root structure, and so forth. The types of animals (especially vertebrates) characteristic of the biome and their typical morphological, physiological, and/or behavioral adaptations to the environment Ecosystem: Ecosystem interacting system of plants, animals and humans and their surrounding physical environment. An ecosystem contains living and non-living organisms that each provide or contribute to a unique service or function that other organisms depend upon. An ecosystem in not merely a collection of organisms. It is a system of interrelationships, interactions and processes. Food webs -Ecosystems can be defined by different scales or sizes from as small as a puddle or a rotting log to a whole forest or the planet. All ecosystems are nested within a system of larger ecosystems. Your assignment: Your assignment You will research an ecosystem of your choice. You will be required to research the different aspects that make that ecosystem unique “ as presented for biomes on the previous slide”. You will be required to find a peer reviewed primary research article related to your ecosystem that will be presented along with the other topics in your presentation. This will be done via Power point. The Tundra : The Tundra Tundra: Tundra The word tundra derives from the Finnish word for barren or treeless land. The tundra is the simplest biome in terms of species composition and food chain Vegetation: lichens, mosses, sedges, and dwarfed shrubs, (often heaths, but also birches and willows). Climate: The high latitude conditions of climate type that impact life in this biome include extremely short growing season (6 to 10 weeks) long, cold, dark winters (6 to 10 months with mean monthly temperatures below 32° F or 0° C.) low precipitation (less than five inches/year) coupled with strong, drying winds. Snowfall is actually advantageous to plant and animal life as it provides an insulating layer on the ground surface. Tundra: Tundra Soil: No true soil is developed in this biome due to the edaphic factors mentioned above. Fauna: Strategies evolved to withstand the harsh conditions of the tundra can be divided among those species that are resident and those that are migratory. - Among the small number of bird (e.g., ptarmigan) and mammal (e.g., muskox, arctic hare, arctic fox, musk ox) species that reside year-round on the tundra one commonly finds: - Migratory species such as waterfowl, shorebirds and caribou adapt to the tundra by avoiding the most severe conditions of winter. Each year at the end of the short growing season they move southward into the boreal forest or beyond, but return to the tundra to breed. Taiga or Boreal Forest : Taiga or Boreal Forest Introduction : Introduction The taiga or boreal forest exists as a nearly continuous belt of coniferous trees across North America and Eurasia. Overlying formerly glaciated areas and areas of patchy permafrost on both continents, the forest is mosaic of successional and subclimax plant communities sensitive to varying environmental conditions. Taiga is the Russian name for this forest which covers so much of that country. However, the term is used in North America as well. Climate: : Climate: The taiga corresponds with regions of subarctic and cold continental climate (Koeppen's Dfc, Dfd, and Dwd climate types). Long, severe winters (up to six months with mean temperatures below freezing) and short summers (50 to 100 frost-free days) are characteristic, as is a wide range of temperatures between the lows of winter and highs of summer. For example, Verkhoyansk, Russia, has recorded extremes of minus 90 ° Fand plus 90 ° F. Mean annual precipitation is 15 to 20 inches, but low evaporation rates make this a humid climate. Vegetation: : Vegetation: Needleleaf, coniferous (gymnosperm) trees are the dominant plants of the taiga biome. A very few species in four main genera are found: the evergreen spruce (Picea), fir (Abies), and pine (Pinus), and the deciduous larch or tamarack (Larix). In North America, one or two species of fir and one or two species of spruce are dominant. Across Scandanavia and western Russia the Scots pine is a common component of the taiga. Growthforms: : Growthforms: Conical shape - promotes shedding of snow and prevents loss of branches. Needleleaf - narrowness reduces surface area through which water may be lost (transpired), especially during winter when the frozen ground prevents plants from replenishing their water supply. The needles of boreal conifers also have thick waxy coatings--a waterproof cuticle--in which stomata are sunken and protected from drying winds. Evergreen habit - retention of foliage allows plants to photosynthesize as soon as temperatures permit in spring, rather than having to waste time in the short growing season merely growing leaves. [Note: Deciduous larch are dominant in areas underlain by nearly continuous permafrost and having a climate even too dry and cold for the waxy needles of spruce and fir.] Dark color - the dark green of spruce and fir needles helps the foliage absorb maximum heat from the sun and begin photosynthesis as early as possible. Fauna: : Fauna: Fur-bearing predators like the lynx (Felis lynx) and various members of the weasel family (e.g., wolverine, fisher, pine martin, mink, ermine, and sable) are perhaps most characteristic of the boreal forest proper. The mammalian herbivores on which they feed include the snowshoe or varying hare, red squirrel, lemmings, and voles. Temperate Broadleaf Deciduous Forest: Temperate Broadleaf Deciduous Forest Introduction : Introduction The Temperate Broadleaf Deciduous Forest (TBDF)--especially in eastern North America, where is remains most intact--is known for the turning of the colors of its leaves to brilliant reds, oranges, and golds in autumn. The shortening days of fall stimulate the plants to withdraw chlorophyll from their leaves, allowing a brief but beautiful display of other pigments before the leaves are shed completely and plants enter an extended period of dormancy. Climate: : Climate: There is an approximately 6 month growing season. The 20 to 60 inches of precipitation is distributed evenly throughout the year. The non-growing season is due to temperature-induced drought during the cold winters. Vegetation: : Vegetation: Many of the same genera, previously part of an Arcto-Tertiary Geoflora, are common to all three of the disjunct northern hemisphere expressions of this biome. Included among these genera are Quercus (oak), Acer (maple), Fagus (beech), Castanea (chestnut), Carya (hickory), Ulmus (elm), Tilia (basswood or linden), Juglans (walnut), and Liquidamber (sweet gum). Different species of these genera occur on each continent. Structure and Growthforms: : Structure and Growthforms: a tree stratum, 60 -100 feet high, dominated regionally by various combinations of the genera listed before; a small tree or sapling layer, with not only younger specimens of the tall trees with species limited to this layer such as (in Virginia) Allegheny serviceberry or shadbush, sourwood, dogwood, and redbud; a shrub layer often with members of the heath family such as rhododendron, azaleas, mountain laurel, and huckleberries; an herb layer of perennial forbs that bloom primarily in early spring; and a ground layer of lichens, clubmosses, and true mosses. Lichens and mosses also grow on the trunks of trees. Soil: : Soil: Podzolization occurs as a result of the acid soil solution produced under needleleaf trees. Fauna: : Fauna: North American herbivores include white-tail deer, gray squirrel, and chipmunk. Omnivores include raccoon, opossum, skunk, and black bear. Carnivores have been largely eliminated through the deliberate effort of humans but should include timber wolves, mountain lions, and bobcats. The coyote, native to the western grasslands and deserts, has recently dispersed east and taken over the niche of its departed cousin, the timber wolf. Tropical Broadleaf Evergreen Forest: The Rainforest : Tropical Broadleaf Evergreen Forest: The Rainforest Introduction. : Introduction. The tropical rainforest is earth's most complex biome in terms of both structure and species diversity. It occurs under optimal growing conditions: abundant precipitation and year round warmth. There is no annual rhythm to the forest; rather each species has evolved its own flowering and fruiting seasons. Sunlight is a major limiting factor. A variety of strategies have been successful in the struggle to reach light or to adapt to the low intensity of light beneath the canopy. Climate: : Climate: Mean monthly temperatures are above 64 ° F; precipitation is often in excess of 100 inches a year. There is usually a brief season of reduced precipitation. In monsoonal areas, there is a real dry s eason, but that is more than compensated for with abundant precipitation the rest of the year. Vegetation: Layers: Vegetation: Layers A layer: the emergents. Widely spaced trees 100 to 120 feet tall and with umbrella-shaped canopies extend above the general canopy of the forest. Since they must contend with drying winds, they tend to have small leaves and some species are deci duous during the brief dry season. B layer: a closed canopy of 80 foot trees. Light is readily available at the top of this layer, but greatly reduced below it. C layer: a closed canopy of 60 foot trees. There is little air movement in this zone and consequently humidity is constantly high. Shrub/sapling layer: Less than 3 percent of the light intercepted at the top of the forest canopy passes to this layer. Arrested growth is characteristic of young trees capable of a rapid surge of growth when a gap in canopy above them opens. Ground layer: sparse plant growth. Less than 1 percent of the light that strikes the top of the forest penetrates to the forest floor. In such darkness few green plants grow. Moisture is also reduced by the canopy above: one third of the precipitation is intercepted before it reaches the ground. Growthforms: : Growthforms: Epiphytes: the so-called air plants grow on branches high in the trees, using the limbs merely for support and extracting moisture from the air and trapping the constant leaf-fall and wind-blown dust. Bromeliads (pineapple family) are especially abundant in the neotropics; the orchid family is widely distributed in all three formations of the tropical rainforest. As demonstration of the relative aridity of exposed branches in the high canopy, epiphytic cacti also occur in the Americas. Lianas: woody vines grow rapidly up the tree trunks when there is a temporary gap in the canopy and flower and fruit in the tree tops of the A and B layers. Many are deciduous. Climbers: green-stemmed plants such as philodendron that remain in the understory. Many climbers, including the ancestors of the domesticated yams (Africa) and sweet potatoes (South America), store nutrients in roots and tubers. Stranglers: these plants begin life as epiphytes in the canopy and send their roots downward to the forest floor. The fig family is well represented among stranglers. Heterotrophs: non-photosynthetic plants can live on the forest floor. Parasites derive their nutrients by tapping into the roots or stems of photosynthetic species. Rafflesia arnoldi, a root parasite of a liana, has the world's largest flower, more than three feet in diameter. It produces an odor similar to rotting flesh to attract pollinating insects. Saprophytes derive their nutrients from decaying organic matter. Some orchids employ this strategy common to fungi and bacteria. Soil:: Soil: infertile, deeply weathered and severely leached, have developed on the ancient Gondwanan shields. Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminum oxides by the laterization process gives the soil a bright red color and sometimes produces minable deposits (e.g., bauxite). On younger substrates, especially of volcanic origin, tropical soils may be quite fertile. Fauna: : Fauna: Animal life is highly diverse. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to an arboreal life (for example, the prehensile tails of New World monkeys), bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits. Tropical Savannas : Tropical Savannas Introduction. : Introduction. Tropical savannas or grasslands are associated with the tropical wet and dry climate type, but they are not generally considered to be a climatic climax. Instead, savannas develop in regions where the climax community should be some form of seasonal forest or woodland, but conditions or disturbances prevent the establishment of those species of trees associated with the climax community. The vegetation. : The vegetation. Savannas are characterized by a continuous cover of perennial grasses, often 3 to 6 feet tall at maturity. They may or may not also have an open canopy of drought-resistant, fire-resistant, or browse-resistant trees, or they may have an open shrub layer. Distinction is made between tree or woodland savanna, park savanna, shrub savanna and grass savanna. Furthermore, savannas may be distinguished according to the dominant taxon in the tree layer: for example, palm savannas, pine savannas, and acacia savannas Climate. : Climate. A tropical wet and dry climate predominates in areas covered by savanna growth. Mean monthly temperatures are at or above 64° F and annual precipitation averages between 30 and 50 inches. For at least five months of the year, during the dry season, less than 4 inches a month are received. The dry season is associated with the low sun period. Soils. : Soils. Soils vary according to bedrock and edaphic conditions. In general, however, laterization is the dominant soil-forming process and low fertility soils can be expected. Fauna. : Fauna. The world's greatest diversity (over 40 different species) of ungulates (hoofed mammals) is found on the savannas of Africa. The antelopes are especially diverse and including eland, impalas, gazelles oryx, gerenuk, and kudu. Buffalo, wildebeest, plains zebra, rhinos, giraffes, elephants, and warthogs are among other herbivores of the African savanna. Desert scrub : Desert scrub Introduction: : Introduction: Desert areas are rarely devoid of life. Instead, they abound with wonderfully adapted plants and animals that have evolved various mechanisms for tolerating or avoiding the extremes of aridity and temperature that might be encountered in their environment. Climate. : Climate. Arid climates are those which average less than 10 inches of precipitation a year. Potential evaporation exceeds precipitation in the annual water budget. Furthermore, rainfall is highly localized and relatively unpredictable in terms of when it will occur, although usually there are seasons of highest probability for precipitation. Annual variation in total precipitation may also be great. Temperatures are also variable. They may exceed 100° F on summer afternoons, but dip by 20-30 degrees or more at night. Vegetation. : Vegetation. Shrubs are the dominant growthform of deserts. They may be evergreen or deciduous; typically have small leaves; and frequently have spines or thorns and/or aromatic oils. Shallow but extensive root systems (Phreatophytes) procure rainwater (Succulents) from well beyond the canopy of the shrub whenever it does rain. These are the true xerophytes adapted to tolerate extreme drought. They form an open canopy and, except after rains when annuals may cover the desert floor, the ground between shrubs is bare of vegetative growth. Soils. : Soils. Calcification is the dominant soil-forming process, if indeed soil forming even occurs. There is poor development of horizons, with accumulation of calcium carbonate at or near the surface. Sparse vegetative cover and tiny leaves results in little humus and soils typically have a light gray color. Fauna. : Fauna. Like the plants, the animals of the desert have evolved an array of strategies for dealing with aridity Reptiles, tough skin, uric acid Birds, fly Temperate Grasslands : Temperate Grasslands Introduction. : Introduction. Temperate grasslands are composed of a rich mix of grasses and forbs and underlain by some of the world's most fertile soils. Since the development of the steel plow most have been converted to agricultural lands. Climate: : Climate: Semiarid, continental climates of the middle latitudes typically have between 10 and 20 inches of precipitation a year. Much of this falls as snow, serving as reservoir of moisture for the beginning of the growing season. Warm to hot summers are experienced, depending on latitude. Vegetation. : Vegetation. Perennial grasses and perennial forbs [especially Compositae (or Asteraceae, depending on the taxonomic system used) and Leguminosae--the sunflower and pea families, respectively] are dominant growthforms. Soils. : Soils. Calcification is the dominant soil-forming process in semiarid regions. Mild leaching, high organic content, and concentration of calcium carbonate in the B horizon typifies the dark brown soils developed under the temperate grasslands. Calcium rich, the world's most fertile soils are created Fauna. : Fauna. The temperate grassland fauna is very low in diversity, especially in comparison with the tropical grasslands or savannas of Africa. In North America the dominant herbivores are bison Bison bison) and pronghorn (the sole member of the Nearctic endemic family, Antilocapridae). Rodent herbivores include the pocket gopher (another Nearctic endemic), ground squirrels, and the prairie dog. Carnivores include coyote (actually an omnivore), badger, and the federally endangered black-footed ferret, the last two members of the weasel family. Mediterranean Shrublands : Mediterranean Shrublands Introduction. : Introduction. Regions of Mediterranean-type climate occur roughly between 30° and 40° latitude on the west coasts of continents, where offshore there are cold ocean currents. Comparative studies of the several regional expressions of this biome reveal interesting examples of convergent evolution in plant families and birds (but not among reptiles or small mammals) on the different continents.