:: wikimiki.org ::
| Topsoil |
TopsoilTopsoil is the uppermost layer of soil, usually the top 15-20 cm. It has the highest concentration of organic matter and microorganisms, and is where most of the Earth's biological soil activity occurs. Plants generally concentrate their roots in, and obtain most of their nutrients from this layer. Topsoil can be measured as the depth from the surface to the first densely packed soil layer known as hardpan.
A major environmental concern known as topsoil erosion, occurs when the topsoil layer is blown or washed away. Without topsoil, little plant life is possible.
A variety of soil mixtures are sold commercially as topsoil, usually for use in improving gardens and lawns.
As one of the layers of soil on the Earth's surface, topsoil is sometimes referred to as the A horizon.
Category:Soil science
Soil
Soil is unconsolidated rock particles mixed with organic matter from plant decay.
Soil is vital to all life on Earth because it supports the growth of plants, which supply food and oxygen and absorbs carbon dioxide and nitrogen. Soil serves as a habitat for animal life from microorganisms to small animals.
Soil components
Soils vary widely in composition and structure from place to place. Soils are formed through the weathering of rock and the breakdown of organic matter. Weathering is the action of wind, rain, ice, sunlight and biological processes on rocks, which breaks them down into small particles. The proportions of minerals and organic matter determine the structure and other characteristics of a particular soil.
Soils can be divided into two general layers or strata: topsoil, the topmost layer, where most plant roots, microorganisms, and other animal life are located, and subsoil, which is deeper and often more dense and less rich in organic matter.
Water and air are also components of most soils. Air, trapped in spaces between soil particles, and water, trapped in spaces and on the surface of particles, comprises about half of the soil by volume. Both are important to plant growth and other life in the soil profile of a particular ecosystem.
The rock and mineral content of soil is categorized according to particle size as sand (coarsest), silt or clay (finest); the ratio of these particles to a great degree determines the soil classification and characteristics.
Former soils which become buried below the effects of organisms are called paleosols.
Soil develops naturally over time through the action of plants, animals, and weathering. Soil is also affected by human habitation. People can alter soil to make it more suitable for plant growth through the addition of organic material and natural or synthetic fertilizer, and by improving its drainage or water-retaining capacity. Human actions also can degrade soil through the depletion of nutrients, pollution, contamination, and compaction, and by increasing the rate of erosion, which is the relocation of soil through the movement of water or wind.
Natural soil development
An example of soil development from bare rock occurs on recent lava flows in warm regions under heavy and very frequent rainfall. In such climates plants become established very quickly on basaltic lava, even though there is very little organic material. The plants are supported by the porous rock becoming filled with nutrient bearing water, for example carrying dissolved bird droppings or guano. The developing plant roots themselves gradually break up the porous lava and organic matter soon accumulates but, even before it does, the predominantly porous broken lava in which the plant roots grow can be considered soil.
Chemical processes in soils
Weathering releases ions such as Potassium (K+) and Magnesium (Mg2+) into the soil solution. Some of these elements (as ions) are taken up by plants, but the majority not left in solution are absorbed through ion exchange by clays such as montmorillonite. When the level of ions is low in the soil an equilibrium process forces ions back into solution, where they can be used by plants.
However if acid is introduced into soil, e.g. by acid rain, hydrogen ions bind in preference to clays, forcing ions out where they can be washed away during rain. Acidity also encourages the weathering of clays, releasing toxic aluminium ions (of which clays are composed) into the solution. To stop this occurring, farmers may apply alkaline materials such as slaked lime.
Although the elements nitrogen, potassium and phosphorus, which are necessary for plant growth, may be abundant in soil, only a fraction of these elements may be in a chemical form which plants can use. In processes such as nitrification and mineralisation, bacteria and other organisms convert unusable forms (such as NH4+) to usable forms (such as NO3-). The raw products are initially present as gases in the atmosphere. Processes such as the nitrogen cycle and carbon cycle continually exchange nutrients between the soil and atmosphere.
The organic component of soils originate in plant debris (such as fallen leaves), animal excreta, and other decomposing organic materials. These materials, when broken down, form humus, a dark, nutrient-rich material. Chemically, humus is composed of very large molecules including esters of carboxylic acid, phenolic compounds, and derivatives of benzene. Organic material in soil provides nutrients necessary for plant growth. Organic material also contributes to water retention, drainage ability, and oxygenation of soil.
If oxygen enters a wet soil, because of lowered ground water table, organic matter in the soil will be broken down further by oxidation, which can lead to subsidence. An example of this can be seen in soils in the Everglades region of Florida, which have been drained by canals for agriculture, primarily sugar production. Originally very high in organic content, oxygenation and compaction have led to breakdown of the soil structure and nutrient content, and degradation of the soil's ability to support continued high crop yields.
Biological processes in soil
Wetland soil processes
The diffusion of dissolved oxygen in saturated soils is slower than in unsaturated soils. Wetland (also referred to as hydric) soils form due to soil microbial cellular respiration in excess of soil oxygen supply, resulting in oxygen depletion. Anaerobic soil chemistry results, which creates a reducing environment. This eliminates plants and creatures not adapted for life in saturated soil conditions.
Biological soil crusts
Biological soil crusts are formed by living organisms and their by-products, creating a surface crust of soil particles bound together by organic materials.
References
- Soil Survey Staff. (1975) Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. USDA-SCS Agric. Handb. 436. U.S. Gov. Print. Office. Washington, DC.
- Soil Survey Division Staff. (1993) Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18.
- Logan, W. B., Dirt: The ecstatic skin of the earth. 1995 ISBN 1573220043
- Faulkner, William. Plowman's Folly. New York, Grosset & Dunlap. 1943. ISBN 0933280513
- Jenny, Hans, Factors of Soil Formation: A System of Quantitative Pedology 1941
- [http://jan.ucc.nau.edu/~doetqp-p/courses/env320/lec1/Lec1.html Why Study Soils?]
- [http://www.hort.purdue.edu/newcrop/tropical/lecture_06/chapter_12l_R.html Soil notes]
- [http://www.home2garden.org/soil.html Soil articles]
See also:
- Alluvium
- Compost
- Denitrification
- Derelict soil
- FAO - Soil Unit Classification Scheme
- Humus
- Manure
- Nitrification
- Nitrogen cycle
- Nitrogen fixation
- Pedology
- Pedogenesis
- Soil degradation
- Soil moisture
- Soil pH
- Soil profile
- Soil salination
- Soil science
- Soil structure
- Soil survey (soil mapping)
- Soil test
- Soil types
- Topsoil
- USA soil taxonomy
Category:Ecology
Category:Soil science
ja:土
MicroorganismA microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). Microorganisms are often illustrated using single-celled, or unicellular organisms; however, some unicellular protists are visible to the naked eye, and some multicellular species are microscopic. The study of microorganisms is called microbiology.
Micro-organisms and unicellular organisms
Micro-organisms may be found almost anywhere in the taxonomic structure. Unicellular organisms carry out all the functions of life. Bacteria and archaea are almost always microscopic. A number of eukaryotes are also microscopic, including most protists and a number of fungi. Unicellular species are those whose members consist of a single cell throughout their life cycle. This latter qualification is significant since most multicellular organisms consist of a single cell at the beginning of their life cycles.
Usually, unicellular organisms contain only a single copy of their genome (except when undergoing cell division), although some organisms have multiple cell nuclei (see coenocyte).
Habitats and ecology
Microorganisms are found everywhere in nature. Even in hostile environments, like the poles, deserts, geysers, rocks, and the deep sea, some types of microorganisms have adapted to the extreme conditions and sustained colonies; these organisms are known as extremophiles. Some extremophiles have been known to survive for a prolonged time in a vacuum, and some can be unusually resistant to radiation.
Microorganisms are used in brewing, baking, biotechnology, recycling of other organisms' remains and waste products, and many other processes. They can also be harmful as pathogens when, as parasites, they cause infections.
Microorganisms have an important place in all ecosystems and in most higher-order multicellular organisms. For mankind they are important because they participate in the earth's element cycles (such as the Carbon cycle), and because of their use in the creation of certain types of food, medicines and biological weapons.
See also
- Biology
- Microbiology
- Microscope
- Prokaryote
- Eukaryote
- Archaea
- Cell
- Nanobacterium
External links
- [http://www.genomenewsnetwork.org/categories/index/microbes.php Microbe News from Genome News Network]
- [http://news.bbc.co.uk/1/hi/sci/tech/1569264.stm BBC News, 28 September, 2001: The microbes that 'rule the world'] Citat: "... The Earth's climate may be dependent upon microbes that eat rock beneath the sea floor, according to new research....The number of the worm-like tracks in the rocks diminishes with depth; at 300 metres (985 feet) below the sea floor, they become much rarer..."
- [http://news.bbc.co.uk/1/hi/sci/tech/827063.stm BBC News, 10 July, 2000, Snow microbes found at South Pole] Citat: "...able to survive the large doses of ultraviolet radiation, extreme cold and darkness...The microbes have DNA sequences similar to a category of bacteria known as Deinococcus..."
- [http://news.bbc.co.uk/1/hi/sci/tech/1764716.stm BBCNews: 16 January, 2002, Tough bugs point to life on Mars] Citat: "...This research demonstrates that certain microbes can thrive in the absence of sunlight by using hydrogen gas..."
- [http://news.bbc.co.uk/1/hi/sci/tech/1765792.stm BBCNews: 17 January, 2002, Alien life could be like Antarctic bugs]
- [http://gsbs.utmb.edu/microbook/toc.htm Microbiology]
ko:미생물
ja:微生物
th:จุลินทรีย์
Plant
- Land plants (embryophytes)
- Non-vascular plants (bryophytes)
- Marchantiophyta - liverworts
- Anthocerotophyta - hornworts
- Bryophyta - mosses
- Vascular plants (tracheophytes)
- Lycopodiophyta - clubmosses
- Equisetophyta - horsetails
- Pteridophyta - "true" ferns
- Psilotophyta - whisk ferns
- Ophioglossophyta - adderstongues
- Seed plants (spermatophytes)
- †Pteridospermatophyta - seed ferns
- Pinophyta - conifers
- Cycadophyta - cycads
- Ginkgophyta - ginkgo
- Gnetophyta - gnetae
- Magnoliophyta - flowering plants
Magnoliophyta
Plants are a major group of living things (about 300,000 species), including familiar organisms such as trees, flowers, herbs, and ferns. Aristotle divided all living things between plants, which generally do not move or have sensory organs, and animals. In Linnaeus' system, these became the Kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts. Indeed, any attempt to match "plant" with a single taxon is doomed to fail, because plant is a vaguely defined concept unrelated to the presumed phylogenic concepts on which modern taxonomy is based.
Embryophytes
:See main article at Embryophytes
Most familiar are the multicellular land plants, called embryophytes. They include the vascular plants, plants with full systems of leaves, stems, and roots. They also include a few of their close relatives, often called bryophytes, of which mosses and liverworts are the most common.
All of these plants have eukaryotic cells with cell walls composed of cellulose, and most obtain their energy through photosynthesis, using light and carbon dioxide to synthesize food. About three hundred plant species do not photosynthesize but are parasites on other species of photosynthetic plants. Plants are distinguished from green algae, from which they evolved, by having specialized reproductive organs protected by non-reproductive tissues.
Bryophytes first appeared during the early Palaeozoic. They can only survive where moisture is available for significant periods, although some species are desiccation tolerant. Most species of bryophyte remain small throughout their life-cycle. This involves an alternation between two generations: a haploid stage, called the gametophyte, and a diploid stage, called the sporophyte. The sporophyte is short-lived and remains dependent on its parent gametophyte.
Vascular plants first appeared during the Silurian period, and by the Devonian had diversified and spread into many different land environments. They have a number of adaptations that allowed them to overcome the limitations of the bryophytes. These include a cuticle resistant to desiccation, and vascular tissues which transport water throughout the organism. In most the sporophyte acts as a separate individual, while the gametophyte remains small.
Devonians (Pteridophyta) more closely allied to seed plants than they are to clubmosses (Lycopodiophyta)]]
The first primitive seed plants, Pteridosperms (seed ferns) and Cordaites, both groups now extinct, appeared in the late Devonian and diversified through the Carboniferous, with further evolution through the Permian and Triassic periods. In these the gametophyte stage is completely reduced, and the sporophyte begins life inside an enclosure called a seed, which develops while on the parent plant, and with fertilisation by means of pollen grains. Whereas other vascular plants, such as ferns, reproduce by means of spores and so need moisture to develop, some seed plants can survive and reproduce in extremely arid conditions.
Early seed plants are referred to as gymnosperms (naked seeds), as the seed embryo is not enclosed in a protective structure at pollination, with the pollen landing directly on the embryo. Four surviving groups remain widespread now, particularly the conifers, which are dominant trees in several biomes. The angiosperms, comprising the flowering plants, were the last major group of plants to appear, emerging from within the gymnosperms during the Jurassic and diversifying rapidly during the Cretaceous. These differ in that the seed embryo is enclosed, so the pollen has to grow a tube to penetrate the protective seed coat; they are the predominant group of flora in most biomes today.
Algae and Fungi
The algae comprise several different groups of organisms that produce energy through photosynthesis. However, they are not classified within the kingdom plantae but in the kingdom protista instead. The most conspicuous are the seaweeds, multicellular algae that often closely resemble terrestrial plants, but as stated above are not plants, found among the green, red, and brown algae. These and other algal groups also include various single-celled creatures and forms that are simple collections of cells, without differentiated tissues. Many can move about, and some have even lost their ability to photosynthesize; when first discovered, these were considered as both plants and animals. Now they are considered neither, but protists.
The embryophytes developed from green algae; the two are collectively referred to as the green plants or Viridiplantae. The kingdom Plantae is now usually taken to mean this monophyletic group, as shown above. With a few exceptions among the green algae, all such forms have cell walls containing cellulose and chloroplasts containing chlorophylls a and b, and store food in the form of starch. They undergo closed mitosis without centrioles, and typically have mitochondria with flat cristae.
The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. The same is true of the red algae, and the two groups are generally believed to have a common origin. In contrast, most other algae have chloroplasts with three or four membranes. They are not in general close relatives of the green plants, acquiring chloroplasts separately from ingested or symbiotic green and red algae.
Unlike embryophytes and algae, fungi are not photosynthetic, but are saprophytes: they obtain their food by breaking down and absorbing surrounding materials. Most fungi are formed by microscopic tubes called hyphae, which may or may not be divided into cells but contain eukaryotic nuclei. Fruiting bodies, of which mushrooms are the most familiar, are actually only the reproductive structures of fungi. They are not related to any of the photosynthetic groups, but are close relatives of animals. Therefore, fungus has a kingdom of its own.
Importance
The photosynthesis and carbon fixation conducted by land plants and algae are the ultimate source of energy and organic material in nearly all habitats. These processes also radically changed the composition of the Earth's atmosphere, which as a result contains a large proportion of oxygen. Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively few, anaerobic environments.
Much of human nutrition depends on cereals. Other plants that are eaten include fruits, vegetables, herbs, and spices. Some vascular plants, referred to as trees and shrubs, produce woody stems and are an important source of building material. A number of plants are used decoratively, including a variety of flowers.
Growth
It is a common misconception that most of the solid material in a plant is taken from the soil, when in fact almost all of it is actually taken from the air. Through a process known as photosynthesis, plants use the energy in sunlight to convert carbon dioxide from the air into simple sugars. These sugars are then used as building blocks and form the main structural component of the plant. Plants rely on soil primarily for water (in quantitative terms), but also obtain nitrogen, phosphorus and other crucial nutrients.
phosphorus
Simple plants like algae may have short life spans as individuals, but their populations are commonly seasonal. Other plants may be organized according to their seasonal growth pattern:
- Annual: live and reproduce within one growing season.
- Biennial: live for two growing seasons; usually reproduce in second year.
- Perennial: live for many growing seasons; continue to reproduce once mature.
Among the vascular plants, perennials include both evergreens that keep their leaves the entire year, and deciduous plants which lose their leaves for some part. In temperate and boreal climates, they generally lose their leaves during the winter; many tropical plants lose their leaves during the dry season.
The growth rate of plants is extremely variable. Some mosses grow less than 0.001 mm/h, while most trees grow 0.025-0.250 mm/h. Some climbing species, such as kudzu, which do not need to produce thick supportive tissue, may grow up to 12.5 mm/h.
Fossils
Plant fossils include roots, wood, leaves, seeds, fruit, pollen, spores, phytoliths, and amber (the fossilized resin produced by some plants). Fossil land plants are recorded in terrestrial, lacustrine, fluvial and nearshore marine sediments. Pollen, spores and algae (dinoflagellates and acritarchs) are used for dating sedimentary rock sequences. The remains of fossil plants are not as common as fossil animals, although plant fossils are locally abundant in many regions worldwide.
Early fossils of these ancient plants show the individual cells within the plant tissue. The Devonian period also saw the evolution of what many believe to be the first modern tree, Archaeopteris. This fern-like tree combined a woody trunk with the fronds of a fern, but produced no seeds.
Archaeopteris
The Coal Measures are a major source of Palaeozoic plant fossils, with many groups of plants in existence at this time. The spoil heaps of coal mines are the best places to collect; coal itself is the remains of fossilised plants, though structural detail of the plant fossils is rarely visible in coal. In the Fossil Forest at Victoria Park in Glasgow, Scotland, the stumps of Lepidodendron trees are found in their original growth positions.
The fossilized remains of conifer and angiosperm roots, stems and branches may be locally abundant in lake and inshore sedimentary rocks from the Mesozoic and Caenozoic eras. Sequoia and its allies, magnolia, oak, and palms are often found.
Petrified wood is common in some parts of the world, and is most frequently found in arid or desert areas were it is more readily exposed by erosion. Petrified wood is often heavily silicified (the organic material replaced by silicon dioxide), and the impregnated tissue is often preserved in fine detail. Such specimens may be cut and polished using lapidary equipment. Fossil forests of petrified wood have been found in all continents.
Fossils of seed ferns such as Glossopteris are widely distributed throughout several continents of the southern hemisphere, a fact that gave support to Alfred Wegener's early ideas regarding Continental drift theory.
Distribution
References and further reading
- Kenrick, Paul & Crane, Peter R. (1997). The Origin and Early Diversification of Land Plants: A Cladistic Study. Washington, D. C.: Smithsonian Institution Press. ISBN 1-56098-730-8.
- Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (2005). Biology of Plants (7th ed.). New York: W. H. Freeman and Company. ISBN 0-7167-1007-2.
- Taylor, Thomas N. & Taylor, Edith L. (1993). The Biology and Evolution of Fossil Plants. Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-651589-4.
See also
- Biosphere
- Botany
- Garden
- Flower
- Forest
- Fruit
- Plant cell
- Prehistoric plants
- Tree
- Vegetable
- Vegetation
External links
- [http://tolweb.org/tree?group=Green_plants&contgroup=Eukaryotes Tree of Life]
- Chaw, S.-M. et al. [http://mbe.library.arizona.edu/data/1997/1401/7chaw.pdf Molecular Phylogeny of Extant Gymnosperms and Seed Plant Evolution: Analysis of Nuclear 18s rRNA Sequences (pdf file)] Molec. Biol. Evol. 14 (1): 56-68. 1997.
- [http://florabase.calm.wa.gov.au/phylogeny/cronq88.html Interactive Cronquist classification]
Botanical and vegetation databases
- [http://www.efloras.org/index.aspx e-Floras (Flora of China, Flora of North America and others)]
- [http://plants.usda.gov/ United States of America]
- [http://rbg-web2.rbge.org.uk/FE/fe.html Flora Europaea]
- [http://www.anbg.gov.au/cpbr/databases/ Australia]
- [http://davesgarden.com/pdb/ 'Dave's Garden' horticultural plant database]
- [http://www.chilebosque.cl Chilean plants at Chilebosque]
Category:Plants
Category:Plant_taxonomy
zh-min-nan:Si̍t-bu̍t
ko:식물
ms:Tumbuhan
ja:植物
simple:Plant
th:พืช
NutrientNutrients and the body
A nutrient is any element or compound necessary for or contributing to an organism's metabolism, growth, or other functioning. Six nutrient groups exist, classifiable as those that provide energy, and as those that otherwise support metabolic processes in the body:
Some of them are essential because they cannot be synthesized in the body and must be obtained from a food source.
Substances that provide energy
- Carbohydrates: compounds made up of sugars used or stored as energy Carbohydrates have three different types of simple sugars, which provide short-term energy that are mostly found in fruits. These are monosaccharide, disaccharide, and polysaccharide. There are also complex carbohydrates, which provide sustained energy, for example, starches and fibers. Complex carbohydrates are stored in the body as glycogen.
- Proteins: nitrogenous organic compounds, including amino acids, that provide the building blocks (amino acids) for enzymes and other proteins within the body. The body does not manufacture certain amino acids (termed essential amino acids): the diet must supply these. Proteins are the most abundant component in the human body. Complete proteins include all nine of the required amino acids in adequate amounts. Incomplete proteins are proteins that lack at least one or two of the essential amino acids.
- Fats: fats can be defined as the basic nutrients composed of carbon and hydrogen atoms and oxygen; they are needed for the proper functioning of cells, insulation of body organs against shock, maintenance of body temperature, and needed for healthy skin and hair. including fatty acids (a fat consists of an assemblage of three fatty acids linked to a central glycerine molecule). The body does not manufacture certain fatty acids (termed essential fatty acids): the diet must supply these. Triglycerides make up 95% of our total body fat. The remaining 5% is composed of cholesterol.
Fat has an energy content of 9 kcal/g; proteins and carbohydrates 4 kcal/g. Ethanol (grain alcohol) has an energy content of 7 kcal/g.
Substances that support metabolism
- Minerals: generally trace elements, salts, or ions such as copper and iron; essential to normal metabolism
- Vitamins: organic compounds essential to the body's functioning, usually acting as coenzymes
- Water: absolute requirement for normal growth and metabolism directly involved in all the chemical reactions of life — sometimes referred to as the forgotten nutrient.
Any classification of "nutrients" is likely to be arbitrary given the status of nutrition as a developing science. Researchers are becoming more aware of a wider range of nutrients esential for health.
An organism will metabolise any organic compound to use for its energy content, for structural purposes (growth or replacement of living structures), or for participation in chemical reactions necessary for life. Any particular substance can play more than one role in the body, though researchers lack a good understanding of these roles.
The discovery of the group of nutrients called phytonutrients reinforces the provisional nature of our knowledge. We know little about phytonutrients, organic compounds from plants, which play an essential role in the normal functioning of a body and have complex hormonal effects on health, or play an active role in the amelioration of disease. They do not fit readily into the scheme of the traditional nutrition categories.
Nutrients and the environment
phytonutrients
While in essence true to the definition above, the term nutrients has a more limited meaning within the specialised fields of water quality and water pollution, referring specifically to plant fertilizers. In this context, certain mineral compounds can have an adverse impact on water quality because of their ability to promote plant and algae growth. An excessive growth of aquatic plants can clog waterways (see giant salvinia for example), and over-stimulation of algae and microbes leads to an ecological process called eutrophication.
A surprisingly small number of elements provide interest or concern in this context: really just nitrogen and phosphorus in most aquatic systems. Mineral compounds involved are ammonia, nitrites, nitrates, and orthophosphates. Organic compounds also may contribute, in as much as they also contain nitrogen and phosphorus. The reason only a few chemicals are of concern has to do with the fact that plants are made up mostly of compounds of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P), and lesser amounts of sulfur (S), potassium (K), magnesium (Mg), and calcium (Ca). These elements constitute the macronutrients. Many other elements, though necessary for growth, classify as micronutrients due to the very small quantities required.
Plants obtain carbon, hydrogen, and oxygen (elements most needed for growth) from the air and water, where all three elements occur in great abundance as water and as carbon dioxide. Nutrients having greatest potential to influence plant growth in aquatic environments is those elements needed for plant growth in proportionately large amounts (that is, macronutrients) but likely to become limiting—that is, present in amounts that could be depleted by continued growth. Once used up, further growth will not be possible. Of the nine macronutrients, nitrogen and phosphorus are most likely to become limiting. The others always remain present in great abundance (C, H, O) or usually in amounts that exceed the requirements of aquatic plants or algae.
Farmers apply fertilizer nutrients in the form of nitrogen, phosphorus, and potassium (N, P, and K with perhaps micronutrients) to prevent these elements from becoming limiting in the soil. These elements become concentrated in wastewaters from animal pens and septic or sewage systems. And these elements (especially N and P) in runoff or wastewater discharges reaching streams, lakes, or seas will promote aquatic plant growth. Abundant plant growth itself gives cause for concern in assessing water quality. The most abundant "plants" in most aquatic environments are algae. When essential nutrients are plentiful, algae multiply. If these algae are microscopic phytoplankton, their growth increases the turbidity of the water. The water then becomes cloudy, colored a shade of green, yellow, or brown (sometimes red; see algal bloom). A super abundance of algae, or of higher plants, in an aquatic system can signal excessive inputs of nutrients.
References
- Donatelle, Rebecca J. Health: The Basics. 6th ed. San Francisco: Pearson Education, Inc. 2005. ISBN 0805328521
External links
- [http://www.sankey.ws/dietref.html recommendations for human diet]
Category:Chemical oceanography
Category:Ecology
Category:Nutrients
Category:Nutrition
Category:Soil science
ko:영양소
ja:栄養素
Hardpan
In soil science, agriculture and gardening, hardpan is a general term for a dense layer of soil, residing usually below the uppermost topsoil layer. There are different types of hardpan, all sharing the general characteristic of being a distinct soil layer that is largely impervious to water. Some hardpans are formed by deposits in the soil that fuse and bind the soil particles. These deposits can range from dissolved silica to matrices formed from iron oxides and calcium carbonate. Others are man-made, such as hardpan formed by compaction from repeated plowing particularly with moldboard plows and /or heavy traffic and pollution from man made sources.
Formation
Soil structure strongly affects its tendency to form a hard pan. One such common soil condition related to hardpan is soil pH. Acid soils are most often affected use to the propensity of certain mineral salts, most notably iron and calcium, to form hard complexes with soil particles under acid conditions.
Another major determinant is the soil particle size. Clay particles are one of the smallest particales in commonly found in soils. Due to their structure the spaces between individual clay particlee is quite small and already restricts the passage of water, negatively impacting drainage.Soils with a high clay conenetration are also easily compacted and effected by man made discharges. Clay particles have a strong negative electrostatic charge and will readily bond to positively charged ions dissolved in the soil water matrix. Common salts such as sodium molecules contained in wastewater can fulfil this roll and lead to a localized hardpan in some soil types. This is a common cause of septic system failure due to the prevention of proper drainage in field.
Problems and Workarounds
Hardpan can be a problem in farming and gardening by impeding drainage of water and restricting the growth of plant roots. In these situations, the hardpan can be broken up by either mechanical means such as digging or plowing, or through the use of soil amendments. The broadfork is a manual tool specifically designed for this task; a digging fork or a spade might also be used. The chisel plow does a similar job with the help of a tractor.
The use of soil amendments can also be employed to alter the soil structure and promote the dissolution of the hard pan. It has been observed that increasing the amount of organic matter in the soil through the working-in of manure, compost or peat can both improve local drainage and promote the proliferation of earth worms that can, over time, break relatively thin hardpan layers.
More difficult hardpans may be further improved through the action of both adjusting the soil pH with lime if the soil is acidic, and with the addition of Gypsum. This combination can help loosen clay particles bound into a hardpan by the actions of hard salts such as iron, calcium carbonate and sodium, by promoting their mobility through a higher pH while proving a suitable source of exchanging minerals (the gypsum). This works due to the fact that gypsum salts, although not "soft" are still water permeable and have a larger, more open structure, the results of which do not promote as hard a matrix as was repaced. However, unlike when employing mechanical means, breaking a hardpan through the use of amendments may require action over the course of years, and even then one is by no means assured success. The results are primarily determined by how extensive and / or intractable the hardpan is.
Category:Soil science
CommerceThis article is about the business concept; Commerce is also the name of several places in the United States.
Commerce is the trading of something of value between two entities. That "something" may be goods, services, information, money, or anything else the two entities consider to have value. Commerce is the central mechanism from which capitalism and all other economic systems are derived.
The process of transforming something into a commercial activity is called commercialization.
History of Commerce
Commerce has its origins from the very start of communication in prehistoric times. Trading was the main facility of prehistoric people, who bartered what they had for goods and services from each other. Peter Watson dates the history of long-distance commerce from circa 150,000 years ago.
Later, currency was introduced as a standardized money to facilitate a wider exchange of goods and services. Numismatists have examples of coins from the earliest large-scale societies, although these were initially unmarked lumps of precious metal. The major advantage to commerce of circulating a standardized currency is that money overcomes the "Double coincidence of wants" necessary for barter trades to occur. For example, if a man who makes pots for a living needs a new house, he must hire someone to build it for him. But he cannot make an equivalent number of pots to equal this service done to him, and even if he could the house builder might not want the pots. Currency solved this problem by allowing values to be assigned to things so that goods and services can in a way be effectively collected and stored for later use, or split among several providers.
Today commerce involves a complex system of companies that try to maximise their profits by offering products and services to the market, which consists both of individuals and other companies, at the lowest production cost. There is a system of world wide commerce, which some argue has gone too far (see main: Free trade).
See also
- Advertisement
- Agriculture
- Business
- Capitalism
- Distribution (marketing)
- Wholesaler
- Harvesting
- Retailer
- Industry
- Economy
- Electronic commerce
- Fishery
- Laissez-faire
- Manufacturer
- Manufacturing
- Marketing
- Mass production
Notes
# Introduction.
# Gold was an especially common form of early money, as described in [http://www.ex.ac.uk/~RDavies/arian/origins.html Origins of Money and of Banking]
category:Business
-
Garden: The Garden can also refer to Madison Square Garden.
A garden is a planned space, usually outdoors, set aside for the display, cultivation, and enjoyment of plants and other forms of nature. The garden can incorporate both natural and man-made materials. The most common form is known as a residential garden. Western gardens are almost universally based around plants. Zoos, which display wild animals in simulated natural habitats, were formerly called zoölogical gardens. Some traditional types of eastern gardens, such as Zen gardens, use plants sparsely or not at all. Food-producing gardens are distinguished from farms by their smaller scale, more labor-intensive methods, and their purpose (enjoyment of a hobby rather than produce for sale); this distinction is not always clear-cut, however. The gardening article discusses the differences and similarities between gardens and farms in greater detail.
Gardening is the activity of growing and maintaining the garden. This work is done by an amateur or professional gardener. A gardener might also work in a non-garden setting, such as a park, a roadside embankment, or other public space. Landscape architecture is a related professional activity with landscape architects tending to specialise in design for public and corporate clients.
Relating to the garden
A garden can have many purposes— aesthetic, functional, and recreational. People develop a relationship with the space. That relationship can take many forms; among these are:
- Cooperation with nature
- Plant cultivation
- Observance of nature
- Bird- and insect-watching
- Reflection on the changing seasons
- Relaxation
- Family dinners on the terrace
- Children playing in the yard
- Reading and relaxing in the hammock
- Maintaining the flowerbeds
- Pottering in the shed
- Basking in warm sunshine
- Growing useful produce
- Flowers to cut and bring inside for indoor beauty
- Fresh herbs and vegetables for cooking
Other similar spaces
Other outdoor spaces that are similar to gardens include:
- A landscape is an outdoor natural space of a larger scale, often considered from a distance.
- A park is a planned outdoor space, usually of a larger size, often for public use.
- An arboretum is a planned outdoor space, usually large, for the display and study of trees.
- A farm or orchard is for the production of food stuff.
- A botanical garden is a type of garden where a wide variety of plants are grown both for scientific purposes and for the enjoyment and education of visitors.
- A zoological garden, or zoo for short, is a place where wild animals are cared for and exhibited to the public.
Garden planning and design
Garden planning and garden design may be undertaken by a professional. A landscape architect is a trained, certified and registered professional who can plan and realise outdoor spaces. A garden designer is usually trained to plan and realise residential gardens.
The planner must give consideration to many factors:
- Purpose
- Existing conditions
- Financial constraints
- Maintenance implications
Elements of a garden
The elements of a garden consist of natural conditions and materials, as well as man-made elements:
Natural conditions and materials:
- Soil
- Rocks
- Light conditions
- Wind
- Precipitation
- Air quality
- Pollution
- Proximity to ocean (salinity)
- Plant materials
Man-made elements:
- Terrace, patio, deck
- Paths
- Lighting
- Raised beds
- Outdoor art/ sculpture, such as Gazebos
- Pool, water garden, or other water elements
Types of gardens
Gardens may feature a particular plant or plant type:
- Cactus garden
- Fernery
- Herb garden
- Lawn
- Orchard
- Rose garden
- White garden
- Wildflower garden
Gardens may feature a particular style or aesthetic:
- Alpine or rock garden
- Bonsai or miniature garden
- Chinese garden
- Cottage garden
- Tropical garden
- Formal garden
- Geometric garden
- Informal garden
- Japanese garden
- Zen garden
- Naturalistic garden
- Water garden
- Wild garden
Gardens may function in a particular manner:
- Botanical garden
- Community garden
- Forest garden
- Raised bed gardening
- Residential garden
- Roof garden
- Vertical garden
- Water or soil-less gardening ( hydroponics)
- Walled garden
- Windowbox
- Zoological garden
History of gardens
See history of gardens page.
Gardens in literature
- The Garden of Eden
- Romance of the Rose
- Nathaniel Hawthorne's short-story " Rappaccini's Daughter"
- Frances Hodgson Burnett's The Secret Garden
- Midnight in the Garden of Good and Evil
- Wolfgang Amadeus Mozart's opera La Finta Giardiniera
See also
- List of botanical gardens
- List of public gardens
- List of notable historic gardens in the history of gardens article
- Garden design
- Paradise garden
External Links
- [http://www.gardenvisit.com/garden_history/garden_types/garden-types.htm Classification of garden types]
Category:Gardening
ja:庭園
A horizonThe A horizon is the layer of soil near the surface, and is roughly equivalent to topsoil. Plant roots and seeds grow in this layer, which is primarily composed of humus and minerals. The A horizon is below the O horizon and above the B horizon.
External link
- [http://www.enchantedlearning.com/geology/soil/ Soil layers]
Category:Soil science
Category:Soil science
Category:Agriculture
Category:Agronomy
Category:Ecology
Category:Gardening
Category:Geology
Devonport, New Zealand
Stanley Bay
Stanley Bay
Devonport is a seaside suburb of Auckland, New Zealand. Its population is about 10,000.
It is located on the North Shore, at the southern end of a peninsula that runs south from near Lake Pupuke in Takapuna, extending five kilometres into the Waitemata Harbour. At the southern end of the peninsula is North Head, the northern promontory guarding the mouth of the harbour. Directly opposite it on the south shore is Bastion Point. To the east it is separated from Rangitoto Island by the Rangitoto Channel.
A regular ferry service runs across the Waitemata between Devonport and the central business district of Auckland.
History
Devonport is one of the oldest areas on Auckland's North Shore. First settled by Europeans in 1840. it was initially called Flagstaff because of the flagstaff raised on nearby Mount Victoria (Takarunga).
Because of a nearby deep water anchorage suitable for naval vessels a naval base was established, which is still the primary base for the Royal New Zealand Navy. The settlement was renamed Devonport, after the English naval town of Devonport.
External link
- [http://www.devonportdirectory.co.nz/ Devonport website] The Devonport Directory
category: Auckland urban districts
gry sportowe hostel krakow hoteles en Praga tuszcze gry zrcznociowe |
|
|
| :: RELATED NEWS :: |
Tinctures
In heraldry, tinctures are the colours used to blazon a coat of arms.
Basic tinctures
There are seven principal tinctures, consisting of two metals (light tinctures) and five colours (dark tinctures).
Or
Or is usually spelt with a capital letter (e.g. Gules, a fess Or) so as not to confuse it with the conjunction or.
Sometimes the word gold is used for Or in blazon, either to prevent repeti
|
Penn Singers
Penn Singers is a light opera company at the University of Pennsylvania. It was formed in 1957 by two students, Meryl Moss and Edie Herman, who wanted to create a group of female singers to serve as an alternative to The University of Pennsylvania Glee Club, which was all-male. The original name of the group was Pennsyngers, which was changed to its current form in 1971 when it came under the direction o
|
Sufist
Sufism (Arabic تصوف taṣawwuf) is a mystic tradition of Islam based on the pursuit of spiritual truth as it is gradually revealed to the heart and mind of the Sufi (one who practices Sufism).
It might also be referred to as Islamic mysticism. While other branches of Islam generally focus on exoteric aspects of religion, Sufism is mainly f
|
Marmorata
Marmorata, or Soča trout, Slovenian: Soška postrv, scientific Latin name Salmo trutta marmoratus, is a subspecies of trout indigenous to the Soča (Italian: Isonzo) river in
Slovenia. Today only small populations survive in inaccessible side valleys. Marmorata
is know
|
Satyam
Satyam Computer Services Limited is a consulting and information technology services company.
__TOC__
About
Satyam offers a variety of IT services to many different types of businesses. Satyam's network spans 46 countries, across six continents, and the company employs over 20,000 IT professionals, who work in development centers in India, the United States, the Germanic sacrifice to Norse gods and Elves. The word is related to the English word bless and they are derived from blood, an important component in the rites.
blood (1915)]]
Rites and beliefs
The verb blóta meant to "strengthen" and the intention was to strengthen the powers (gods and Elves). The mos
|
Ponte dei Sospiri
:For other bridges of this name, see Bridge of Sighs (Cambridge) and Bridge of Sighs (Oxford).
Bridge of Sighs (Oxford)
:Bridge of Sighs is also the title of a classic rock album by Robin Trower
The Bridge of Sig
|
Pan African Parliament
The Pan-African Parliament is the governing body of the African Union; however at present it can only exercise advisory and consultative powers. Broadly based on the European Parliament of the European Union (but more like the Parliamentary Assembly of the Council of Europe, as representitives are appointed from member states' legislatures rather than b
|
Anarchists Against the Wall
Anarchists Against the Wall (AAW), sometimes called "Anarchists Against the Fence" or "Jews Against Ghettos", is a loose-knit organization comprised of Israeli anarchists and anti-authoritarians who oppose the construction of the Israeli Gaza Strip barrier and Israeli W
|
The Black League
The Black League are a metal band from Finland. They were formed in 1998 by Taneli Jarva, three years after his departure from Finnish metal heavyweights Sentenced. The Black League's first two full-lengths carry on the spirit from Taneli's work with his former band, seasoning their metal with elements of traditional rock 'n' roll. On their third release,
|
|
