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30-407: Shrubland , scrubland , scrub , brush , or bush is a plant community characterized by vegetation dominated by shrubs , often also including grasses , herbs , and geophytes . Shrubland may either occur naturally or be the result of human activity. It may be the mature vegetation type in a particular region and remain stable over time, or a transitional community that occurs temporarily as

60-429: A discontinuity that may have a large influence on the mechanical behavior (strength, deformation, etc.) of rock masses in, for example, tunnel , foundation , or slope construction. A hazard may exist even in undisturbed terrain. On August 17, 1959, a magnitude 7.2 earthquake destabilized a mountain slope near Hebgen Lake , Montana, composed of schist. This caused a massive landslide that killed 26 people camping in

90-553: A schistose metasandstone (if the protolith is known to have been a sandstone ). If all that is known is that the protolith was a sedimentary rock, the schist will be described as a paraschist , while if the protolith was an igneous rock, the schist will be described as an orthoschist . Mineral qualifiers are important when naming a schist. For example, a quartz-feldspar-biotite schist is a schist of uncertain protolith that contains biotite mica, feldspar , and quartz in order of apparent decreasing abundance. Lineated schist has

120-416: A preferred direction in schist, often also forming very thin parallel layers. The ease with which the rock splits along the aligned grains accounts for the schistosity. Though not a defining characteristic, schists very often contain porphyroblasts (individual crystals of unusual size) of distinctive minerals, such as garnet , staurolite , kyanite , sillimanite , or cordierite . Because schists are

150-458: A shrub is defined as a much-branched woody plant less than 8 m high and usually with many stems . Tall shrubs are mostly 2–8 m high, small shrubs 1–2 m high and subshrubs less than 1 m high. There is a descriptive system widely adopted in Australia to describe different types of vegetation is based on structural characteristics based on plant life-form , plus the height and foliage cover of

180-412: A strong linear fabric in a rock which otherwise has well-developed schistosity. Schistosity is developed at elevated temperature when the rock is more strongly compressed in one direction than in other directions ( nonhydrostatic stress ). Nonhydrostatic stress is characteristic of regional metamorphism where mountain building is taking place (an orogenic belt ). The schistosity develops perpendicular to

210-408: A very large class of metamorphic rock, geologists will formally describe a rock as a schist only when the original type of the rock prior to metamorphism (the protolith ) is unknown and its mineral content is not yet determined. Otherwise, the modifier schistose will be applied to a more precise type name, such as schistose semipelite (when the rock is known to contain moderate amounts of mica) or

240-551: Is Carex shreberi . Other representative forbs occurring in these steppe grasslands are Artemisia austriaca and Polygonum aviculare . Other examples of different plant communities include the forests located on the granite peaks of the Huangshan Mountains in Eastern China. The deciduous broad-leaved forest, present from a height of 1,100 metres, is populated by trees such as Pinus hwangshanesis , also known as

270-540: Is a medium-grained metamorphic rock showing pronounced schistosity (named for the rock). This means that the rock is composed of mineral grains easily seen with a low-power hand lens , oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of platy minerals, such as mica , talc , chlorite , or graphite . These are often interleaved with more granular minerals, such as feldspar or quartz . Schist typically forms during regional metamorphism accompanying

300-518: Is discernible, the schist is usually given a name reflecting its protolith, such as schistose metasandstone . Otherwise, the names of the constituent minerals will be included in the rock name, such as quartz-felspar-biotite schist . Schist bedrock can pose a challenge for civil engineering because of its pronounced planes of weakness . The word schist is derived ultimately from the Greek word σχίζειν ( schízein ), meaning "to split", which refers to

330-609: Is in central Westland in the South Island, New Zealand. These forests are the most extensive continuous reaches of podocarp /broadleaf forests in that country. The canopy includes Prumnopitys ferruginea , rimu and mountain totara . The mid-story includes tree ferns such as Cyathea smithii and Dicksonia squarrosa , whilst the lowest tier and epiphytic associates include Asplenium polyodon , Tmesipteris tannensis , Astelia solandri and Lomaria discolor . Schists Schist ( / ˈ ʃ ɪ s t / SHIST )

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360-436: Is similar in concept to a vegetation type , with the former having more of an emphasis on the ecological association of species within it, and the latter on overall appearance by which it is readily recognized by a layperson. A plant community can be rare even if none of the major species defining it are rare. This is because it is the association of species and relationship to their environment that may be rare. An example

390-533: Is the sycamore alluvial woodland in California dominated by the California sycamore Platanus racemosa . The community is rare, being localized to a small area of California and existing nowhere else, yet the California sycamore is not a rare tree in California. An example is a grassland on the northern Caucasus steppes , where common grass species found are Festuca sulcata and Poa bulbosa . The most common species defining this grassland phytocoenosis

420-475: Is the mature vegetation type, and in other places, the result of degradation of former forest or woodland by logging or overgrazing , or disturbance by major fires. A number of World Wildlife Fund biomes are characterized as shrublands, including: Xeric or desert scrublands occur in the world's deserts and xeric shrublands ecoregions or in fast-draining sandy soils in more humid regions. These scrublands are characterized by plants with adaptations to

450-482: Is the orientation of grains in the surrounding medium-grained rock. The composition of the rock must permit formation of abundant platy minerals. For example, the clay minerals in mudstone are metamorphosed to mica, producing a mica schist. Early stages of metamorphism convert mudstone to a very fine-grained metamorphic rock called slate , which with further metamorphism becomes fine-grained phyllite . Further recrystallization produces medium-grained mica schist. If

480-418: Is uncommon but can form from metamorphosis of sedimentary beds containing abundant organic carbon . This may be of algal origin. Graphite schist is known to have experienced greenschist facies metamorphism , for example in the northern Andes . Metamorphosis of felsic volcanic rock , such as tuff, can produce quartz- muscovite schist. In geotechnical engineering a schistosity plane often forms

510-479: The matas of Portugal , which are underlain by Cambrian and Silurian schists . Florida scrub is another example of interior scrublands. Some vegetation types are formed of dwarf-shrubs : low-growing or creeping shrubs. These include the maquis and garrigues of Mediterranean climates and the acid-loving dwarf shrubs of heathland and moorland . Plant community A plant community can be described floristically (the species of flowers or flora

540-444: The shrub layer , composed of vegetation and trees between a height of approximately one to five meters, the herbaceous layer , composed of vascular plants at a height of one meter or less, and sometimes also the moss layer , a layer of non-vascular bryophytes typically present at ground level (approximately 0.15 meters in height or less). In some cases of complex forests there is also a well-defined lower tree layer. A plant community

570-457: The Huangshan pine. The Huangshan mountain also possesses an evergreen broad-leaved forest community, home to a variety of shrubs and small trees. Some examples of species present in the evergreen broad-leaved forest community include Castanopsis eyrei , Eurya nitidia , Rhododendron ovatum , Pinus massoniana , as well as Loropetalum chinense . An example of a three tiered plant community

600-456: The direction of greatest compression, also called the shortening direction, as platy minerals are rotated or recrystallized into parallel layers. While platy or elongated minerals are most obviously reoriented, even quartz or calcite may take up preferred orientations. At the microscopic level, schistosity is divided into internal schistosity , in which inclusions within porphyroblasts take a preferred orientation, and external schistosity , which

630-484: The dry climate, which include small leaves to limit water loss, thorns to protect them from grazing animals, succulent leaves or stems, storage organs to store water, and long taproots to reach groundwater. Mediterranean scrublands occur naturally in the Mediterranean scrub biome , located in the five Mediterranean climate regions of the world. Scrublands are most common near the seacoast and have often adapted to

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660-425: The ease with which schists can be split along the plane in which the platy minerals lie. Before the mid-19th century, the terms slate , shale and schist were not sharply differentiated by those involved with mining. Geologists define schist as medium-grained metamorphic rock that shows well-developed schistosity. Schistosity is a thin layering of the rock produced by metamorphism (a foliation ) that permits

690-527: The metamorphism proceeds further, the mica schist experiences dehydration reactions that convert platy minerals to granular minerals such as feldspars, decreasing schistosity and turning the rock into a gneiss. Other platy minerals found in schists include chlorite, talc, and graphite. Chlorite schist is typically formed by metamorphism of ultramafic igneous rocks, as is talc schist. Talc schist also forms from metamorphosis of talc-bearing carbonate rocks formed by hydrothermal alteration . Graphite schist

720-510: The other two divisions being gneiss , which has poorly developed schistosity and thicker layering, and granofels , which has no discernible schistosity. Schists are defined by their texture without reference to their composition, and while most are a result of medium-grade metamorphism, they can vary greatly in mineral makeup. However, schistosity normally develops only when the rock contains abundant platy minerals, such as mica or chlorite . Grains of these minerals are strongly oriented in

750-403: The plant community contains) and/or phytophysiognomically (the physical structure or appearance of the plant community). For example, a forest (a community of trees) includes the overstory , or upper tree layer of the canopy , as well as the understory , a layer consisting of trees and shrubs located beneath the canopy but above the forest floor. The understory can be further subdivided into

780-400: The process of mountain building ( orogeny ) and usually reflects a medium grade of metamorphism. Schist can form from many different kinds of rocks, including sedimentary rocks such as mudstones and igneous rocks such as tuffs . Schist metamorphosed from mudstone is particularly common and is often very rich in mica (a mica schist ). Where the type of the original rock (the protolith )

810-422: The result of a disturbance, such as fire. A stable state may be maintained by regular natural disturbance such as fire or browsing . Shrubland may be unsuitable for human habitation because of the danger of fire. The term was coined in 1903. Shrubland species generally show a wide range of adaptations to fire, such as heavy seed production, lignotubers , and fire-induced germination. In botany and ecology

840-424: The rock to easily be split into flakes or slabs less than 5 to 10 millimeters (0.2 to 0.4 in) thick. The mineral grains in a schist are typically from 0.25 to 2 millimeters (0.01 to 0.08 in) in size and so are easily seen with a 10× hand lens . Typically, over half the mineral grains in a schist show a preferred orientation. Schists make up one of the three divisions of metamorphic rock by texture , with

870-470: The tallest stratum or dominant species . For shrubs that are 2–8 metres (6.6–26.2 ft) high, the following structural forms are categorized: For shrubs less than 2 metres (6.6 ft) high, the following structural forms are categorized: Similarly, shrubland is a category used to describe a type of biome plant group. In this context, shrublands are dense thickets of evergreen sclerophyll shrubs and small trees, called: In some places, shrubland

900-961: The wind and salt air of the ocean. Low, soft-leaved scrublands around the Mediterranean Basin are known as garrigue in France , phrygana in Greece , tomillares in Spain , and batha in Israel . Northern coastal scrub and coastal sage scrub occur along the California coast, strandveld in the Western Cape of South Africa , coastal matorral in central Chile , and sand-heath and kwongan in Southwest Australia . Interior scrublands occur naturally in semi-arid areas where soils are nutrient-poor, such as on

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