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46-449: The vegetation type is defined by characteristic dominant species, or a common aspect of the assemblage, such as an elevation range or environmental commonality. The contemporary use of vegetation approximates that of ecologist Frederic Clements' term earth cover , an expression still used by the Bureau of Land Management . The distinction between vegetation (the general appearance of

92-421: A community) and flora (the taxonomic composition of a community) was first made by Jules Thurmann (1849). Prior to this, the two terms (vegetation and flora) were used indiscriminately, and still are in some contexts. Augustin de Candolle (1820) also made a similar distinction but he used the terms "station" ( habitat type) and "habitation" ( botanical region ). Later, the concept of vegetation would influence

138-407: A cyclical pattern. Ecosystems that form under these conditions are often maintained by regular disturbance. Wetland ecosystems, for example, can be maintained by the movement of water through them and by periodic fires. Different types of disturbance events occur in different habitats and climates with different weather conditions. Natural fire disturbances for example occur more often in areas with

184-447: A good example of such a cycle involving insect outbreaks. The mountain pine beetle ( Dendroctonus ponderosae ) plays an important role in limiting pine trees like lodgepole pine in forests of western North America. In 2004 the beetles affected more than 90,000 square kilometres. The beetles exist in endemic and epidemic phases. During epidemic phases swarms of beetles kill large numbers of old pines. This mortality creates openings in

230-542: A higher incidence of lightning and flammable biomass, such as longleaf pine ecosystems in the southeastern United States. Wildfires , droughts , floods , disease outbreaks, changes in hydrology , tornadoes and other extreme weather, landslides, and windstorms are all examples of natural disturbance events that may form a cyclical or periodic pattern over time. Other disturbances, such as those caused by humans, invasive species or impact events, can occur anywhere and are not necessarily cyclic. These disturbances can alter

276-445: A long period of time and can impact the biodiversity within an ecosystem. Major ecological disturbances may include fires , flooding , storms , insect outbreaks and trampling . Earthquakes , various types of volcanic eruptions , tsunami , firestorms , impact events , climate change , and the devastating effects of human impact on the environment ( anthropogenic disturbances) such as clearcutting , forest clearing and

322-414: A major portion of the organization and spatial patterning of natural communities. Disturbance variability and species diversity are heavily linked, and as a result require adaptations that help increase plant fitness necessary for survival. Disturbance in ecosystems can form a way of modeling future ability of ecosystems to adapt to climate change . Likewise, adaptation of a species to disturbance may be

368-527: A regular and recurring part of the long-term system dynamic. Fire and wind disturbances are prevalent throughout many vegetation types worldwide. Fire is particularly potent because of its ability to destroy not only living plants but also the seeds, spores, and living meristems representing the potential next generation, and because of fire's impact on fauna populations, soil characteristics and other ecosystem elements and processes (for further discussion of this topic see fire ecology ). Temporal change at

414-404: A result grow quickly. Their fast growth is usually balanced by short life spans. Furthermore, although these species often dominate immediately following a disturbance, they are unable to compete with shade-tolerant species later on and replaced by these species through succession. However these shifts may not reflect the progressive entry to the community of the taller long-lived forms, but instead,

460-507: A slower pace is ubiquitous; it comprises the ecological succession field. Succession is the relatively gradual structure and taxonomic composition change that arises as the vegetation modifies various environmental variables over time, including light, water, and nutrient levels. These modifications change the suite of species most adapted to grow, survive, and reproduce in an area, causing floristic changes. These floristic changes contribute to structural changes inherent in plant growth even in

506-428: A tree is blown over, gaps typically are filled with small herbaceous seedlings but, this is not always the case; shoots from the fallen tree can develop and take over the gap. The sprouting ability can have major impacts on the plant population, plant populations that typically would have exploited the tree fall gap get over run and can not compete against the shoots of the fallen tree. Species adaptation to disturbances

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552-497: Is controlled burns used by Native Americans to maintain fire-dependent ecosystems. These disturbances helped maintain stability and biodiversity in ecosystems, enhancing overall ecosystem health and functioning. Anthropogenic climate change is considered a major source of change in future successional trajectories of ecosystems. Immediately after a disturbance there is a pulse of recruitment or regrowth under conditions of little competition for space or other resources. After

598-418: Is in ponderosa pine ( Pinus ponderosa ) forests in the western United States, where surface fires frequently thin existing vegetation allowing for new growth. If fire is suppressed, douglas fir ( Pesudotsuga menziesii ), a shade tolerant species, eventually replaces the pines. Douglas firs, having dense crowns, severely limit the amount of sunlight reaching the forest floor. Without sufficient light new growth

644-499: Is severely limited. As the diversity of surface plants decreases, animal species that rely on them diminish as well. Fire, in this case, is important not only to the species directly affected but also to many other organisms whose survival depends on those key plants. Diversity is low in harsh environments because of the intolerance of all but opportunistic and highly resistant species to such conditions. The interplay between disturbance and these biological processes seems to account for

690-707: Is species specific but how each organism adapts affects all the species around them. Another species well adapted to a particular disturbance is the Jack pine in boreal forests exposed to crown fires. They, as well as some other pine species, have specialized serotinous cones that only open and disperse seeds with sufficient heat generated by fire. As a result, this species often dominates in areas where competition has been reduced by fire. Species that are well adapted for exploiting disturbance sites are referred to as pioneers or early successional species. These shade-intolerant species are able to photosynthesize at high rates and as

736-705: The Federal Geographic Data Committee (FGDC), and originally developed by UNESCO and The Nature Conservancy ), the classification is hierarchical and incorporates the non-floristic criteria into the upper (most general) five levels and limited floristic criteria only into the lower (most specific) two levels. In Europe, classification often relies much more heavily, sometimes entirely, on floristic (species) composition alone, without explicit reference to climate, phenology or growth forms. It often emphasizes indicator or diagnostic species which may distinguish one classification from another. In

782-756: The nutrients previously held in plant biomass is returned quickly to the soil as biomass burns. Many plants and animals benefit from disturbance conditions. Some species are particularly suited for exploiting recently disturbed sites. Vegetation with the potential for rapid growth can quickly take advantage of the lack of competition. In the northeastern United States, shade-intolerant trees (trees stenotopic to shade) like pin cherry and aspen quickly fill in forest gaps created by fire or windstorm (or human disturbance). Silver maple and eastern sycamore are similarly well adapted to floodplains. They are highly tolerant of standing water and will frequently dominate floodplains where other species are periodically wiped out. When

828-663: The phytosociological approach in the study of vegetation relies upon a fundamental unit, the plant association , which is defined upon flora. An influential, clear and simple classification scheme for types of vegetation was produced by Wagner & von Sydow (1888). Other important works with a physiognomic approach includes Grisebach (1872), Warming (1895, 1909), Schimper (1898), Tansley and Chipp (1926), Rübel (1930), Burtt Davy (1938), Beard (1944, 1955), André Aubréville (1956, 1957), Trochain (1955, 1957), Küchler (1967), Ellenberg and Mueller-Dombois (1967) (see vegetation classification ). There are many approaches for

874-550: The Earth's surface. Vegetation classification is often performed by state based agencies as part of land use, resource and environmental management. Many different methods of vegetation classification have been used. In general, there has been a shift from structural classification used by forestry for the mapping of timber resources, to floristic community mapping for biodiversity management . Whereas older forestry-based schemes considered factors such as height, species and density of

920-474: The FGDC standard, the hierarchy levels, from most general to most specific, are: system, class, subclass, group, formation, alliance, and association . The lowest level, or association, is thus the most precisely defined, and incorporates the names of the dominant one to three (usually two) species of a type. An example of a vegetation type defined at the level of class might be " Forest, canopy cover > 60% "; at

966-487: The absence of further disturbance forces, many ecosystems trend back toward pre-disturbance conditions. Long lived species and those that can regenerate in the presence of their own adults finally become dominant. Such alteration, accompanied by changes in the abundance of different species over time, is called ecological succession . Succession often leads to conditions that will once again predispose an ecosystem to disturbance. Pine forests in western North America provide

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1012-428: The absence of species changes (especially where plants have a large maximum size, i.e., trees), causing slow and broadly predictable changes in the vegetation. Succession can be interrupted at any time by disturbance, setting the system back to a previous state or off on another trajectory altogether. Because of this, successional processes may or may not lead to some static, final state . Moreover, accurately predicting

1058-460: The characteristics of such a state, even if it does arise, is not always possible. In short, vegetative communities are subject to many variables that set limits on future conditions' predictability. Generally, the larger an area under consideration, the more likely the vegetation will be heterogeneous. Two main factors are at work. First, the temporal dynamics of disturbance and succession are increasingly unlikely to be in synchrony across any area as

1104-432: The classification of vegetation (physiognomy, flora, ecology, etc.). Much of the work on vegetation classification comes from European and North American ecologists, and they have fundamentally different approaches. In North America, vegetation types are based on a combination of the following criteria: climate pattern, plant habit , phenology and/or growth form, and dominant species. In the current US standard (adopted by

1150-434: The environment, with compounding variables such as extreme temperature or precipitation changes—which all play a role in the diversity and succession of an ecosystem. With environmental moderation, diversity increases because of the intermediate-disturbance effect, decreases because of the competitive-exclusion effect, increases because of the prevention of competitive exclusion by moderate predation, and decreases because of

1196-750: The forest floor. New conditions support a wider variety of plants, often rich in nutrients compared to pre-disturbance vegetation. The plants in turn support a variety of wildlife, temporarily increasing biological diversity in the forest. Biological diversity is dependent on natural disturbance. The success of a wide range of species from all taxonomic groups is closely tied to natural disturbance events such as fire, flooding, and windstorm. As an example, many shade-intolerant plant species rely on disturbances for successful establishment and to limit competition. Without this perpetual thinning, diversity of forest flora can decline, affecting animals dependent on those plants as well. A good example of this role of disturbance

1242-407: The forest for new vegetation. Spruce, fir, and younger pines, which are unaffected by the beetles, thrive in canopy openings. Eventually pines grow into the canopy and replace those lost. Younger pines are often able to ward off beetle attacks but, as they grow older, pines become less vigorous and more susceptible to infestation. This cycle of death and re-growth creates a temporal mosaic of pines in

1288-593: The forest. Similar cycles occur in association with other disturbances such as fire and windstorms. When multiple disturbance events affect the same location in quick succession, this often results in a "compound disturbance", an event which, due to the combination of forces, creates a new situation which is more than the sum of its parts. For example, windstorms followed by fire can create fire temperatures and durations that are not expected in even severe wildfires, and may have surprising effects on post-fire succession. Environmental stresses can be described as pressure on

1334-415: The gradual emergence and dominance of species that may have been present, but inconspicuous directly after the disturbance. Disturbances have also been shown to be important facilitators of non-native plant invasions. While plants must deal directly with disturbances, many animals are not as immediately affected by them. Most can successfully evade fires, and many thrive afterwards on abundant new growth on

1380-420: The impacts on populations, disturbance determines the future shifts in dominance, various species successively becoming dominant as their life history characteristics, and associated life-forms, are exhibited over time. The scale of disturbance ranges from events as small as a single tree falling, to as large as a mass extinction. Many natural ecosystems experience periodic disturbance that may broadly fall into

1426-774: The initial pulse, recruitment slows since once an individual plant is established it is very difficult to displace. Because scale-dependent relationships are ubiquitous in ecology, the spatial scale modulates the effect of disturbance on natural communities. For example, seed dispersal and herbivory may decrease with distance from the edge of a burn. Consequently, plant communities in the interior areas of large fires respond differently than those in smaller fires. Although disturbance types have varied on ecosystems, spatial scale likely influences ecological interactions and community recovery from all cases because organisms differ in dispersal and movement capabilities. Often, when disturbances occur naturally, they provide conditions that favor

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1472-418: The introduction of invasive species can be considered major disturbances. Not only invasive species can have a profound effect on an ecosystem, but also naturally occurring species can cause disturbance by their behavior. Disturbance forces can have profound immediate effects on ecosystems and can, accordingly, greatly alter the natural community ’s population size or species richness. Because of these and

1518-465: The level of a formation as " Winter-rain, broad-leaved, evergreen, sclerophyllous, closed-canopy forest "; at the level of alliance as " Arbutus menziesii forest"; and at the level of association as " Arbutus menziesii-Lithocarpus dense flora forest", referring to Pacific madrone-tanoak forests which occur in California and Oregon, US. In practice, the levels of the alliance and/or an association are

1564-405: The local extinction of prey by severe predation. A reduction in recruitment density reduces the importance of competition for a given level of environmental stress. A disturbance may change a forest significantly. Afterwards, the forest floor is often littered with dead material. This decaying matter and abundant sunlight promote an abundance of new growth. In the case of forest fires a portion of

1610-510: The most often used, particularly in vegetation mapping, just as the Latin binomial is most often used in discussing particular species in taxonomy and in general communication. Like all biological systems, plant communities are temporally and spatially dynamic; they change at all possible scales. Dynamism in vegetation is defined primarily as changes in species composition and structure. Temporally, many processes or events can cause change, but for

1656-432: The plant communities and understand how these patterns are influenced by environmental factors. Disturbance (ecology) In ecology , a disturbance is a temporary change in environmental conditions that causes a pronounced change in an ecosystem . Disturbances often act quickly and with great effect, to alter the physical structure or arrangement of biotic and abiotic elements. A disturbance can also occur over

1702-636: The sake of simplicity, they can be categorized roughly as abrupt or gradual. Abrupt changes are generally referred to as disturbances ; these include things like wildfires , high winds , landslides , floods , avalanches and the like. Their causes are usually external ( exogenous ) to the community—they are natural processes occurring (mostly) independently of the natural processes of the community (such as germination, growth, death, etc.). Such events can change vegetation structure and composition very quickly and for long periods, and they can do so over large areas. Very few ecosystems are without some disturbance as

1748-439: The sixties, A. W. Kuchler coordinated an extensive review of vegetation maps from all the continents, compiling the terminology used for the types of vegetation. The Braun-Blanquet method focuses on the composition of plant species within a community. It examines which species grow together, looking at patterns and differences in species groups across different areas. This method uses data collected from specific plots to compare

1794-405: The size of that area increases. Different areas will be at various developmental stages due to other local histories, particularly their times since the last significant disturbance. This fact interacts with inherent environmental variability (e.g., in soils, climate, topography, etc.), also a function of area. Environmental variability constrains the suite of species that can occupy a given area, and

1840-402: The study of vegetation is common among biogeographers working on vegetation on a world scale, or when there is a lack of taxonomic knowledge of someplace (e.g., in the tropics, where biodiversity is commonly high). The concept of " vegetation type " is more ambiguous. The definition of a specific vegetation type may include not only physiognomy but also floristic and habitat aspects. Furthermore,

1886-516: The success of different species over pre-disturbance organisms. This can be attributed to physical changes in the biotic and abiotic conditions of an ecosystem. Because of this, a disturbance force can change an ecosystem for significantly longer than the period over which the immediate effects persist. With the passage of time following a disturbance, shifts in dominance may occur with ephemeral herbaceous life-forms progressively becoming over topped by taller perennials herbs, shrubs and trees. However, in

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1932-792: The trajectory of change within an ecosystem permanently. Extinction vortices may result in multiple disturbances or a greater frequency of a single disturbance. Logging, dredging, conversion of land to ranching or agriculture , mowing, and mining are examples of anthropogenic disturbance. Human activities have introduced disturbances into ecosystems worldwide on a large scale, resulting in widespread range expansion and rapid evolution of disturbance-adapted species. Agricultural practices create novel ecosystems, known as agroecosystems , which are colonized by plant species adapted to disturbance and enforce evolutionary pressure upon those species. Species adapted to anthropogenic disturbance are often known as weeds . Another example of anthropogenic disturbance

1978-422: The two factors interact to create a mosaic of vegetation conditions across the landscape. Only in agricultural or horticultural systems does vegetation ever approach perfect uniformity. There is always heterogeneity in natural systems, although its scale and intensity will vary widely. Vegetation type Vegetation classification is the process of classifying and mapping the vegetation over an area of

2024-483: The usage of the term biome with the inclusion of the animal element. Other concepts similar to vegetation are " physiognomy of vegetation" ( Humboldt , 1805, 1807) and "formation" ( Grisebach , 1838, derived from " Vegetationsform ", Martius , 1824). Departing from Linnean taxonomy , Humboldt established a new science, dividing plant geography between taxonomists who studied plants as taxa and geographers who studied plants as vegetation. The physiognomic approach in

2070-671: The woody canopy, floristic community mapping shifts the emphasis onto ecological factors such as climate, soil type and floristic associations. Classification mapping is usually now done using geographic information systems (GIS) software. Following, some important classification schemes. Although this scheme is in fact of a climate classification , it has a deep relationship with vegetation studies: Wagner & von Sydow (1888) scheme: Vegetationsgürtel (vegetation belts): Warming (1895, 1909) oecological classes: Warming's types of formations: Schimper (1898, 1903) climatic chief formation types: Schimper formation types across

2116-518: The zones and regions Formation-types: Ellenberg and Mueller-Dombois (1967) scheme: A vegetation classification with six main criteria ("hierarchical attributes", with exemplified categories applicable mainly to Neotropical region): Other important schemes: Grisebach (1872), Tansley and Chipp (1926), Rübel (1930), Burtt Davy (1938), Beard (1944, 1955), André Aubréville (1956, 1957), Trochain (1955, 1957), Dansereau (1958), Küchler (1967), Webb and Tracey (1975). In

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