Climax community

In ecology, climax community, or climatic climax community, is a historic term for a biological community of plants, animals, and fungi which, through the process of ecological succession in the development of vegetation in an area over time, have reached a steady state. This equilibrium was thought to occur because the climax community is composed of species best adapted to average conditions in that area. The term is sometimes also applied in soil development. Nevertheless, it has been found that a "steady state" is more apparent than real, particularly if long-enough periods of time are taken into consideration. Notwithstanding, it remains a useful concept.

The idea of a single climax, which is defined in relation to regional climate, originated with Frederic Clements in the early 1900s. The first analysis of succession as leading to something like a climax was written by Henry Cowles in 1899, but it was Clements who used the term "climax" to describe the idealized endpoint of succession.[1]

Daintree Rainforest
The Daintree Rainforest in Queensland, Australia, is an example of a climax forest ecosystem.
Beech Tree in Warren Woods, MI, USA
Warren Woods in Michigan, USA, is an example of a beech-maple climax forest. Beech (center) and sugar maple (bottom left) dominate the forest due to their towering height and tolerance of shade.

Frederic Clements' use of "climax"

Clements described the successional development of an ecological communities comparable to the ontogenetic development of individual organisms.[2] Clements suggested only comparisons to very simple organisms.[3] Later ecologists developed this idea that the ecological community is a "superorganism" and even sometimes claimed that communities could be homologous to complex organisms and sought to define a single climax-type for each area. The English botanist Arthur Tansley developed this idea with the "polyclimax"—multiple steady-state end-points, determined by edaphic factors, in a given climatic zone. Clements had called these end-points other terms, not climaxes, and had thought they were not stable, because by definition climax vegetation is best-adapted to the climate of a given area. Henry Gleason's early challenges to Clements's organism simile, and other strategies of his for describing vegetation, were largely disregarded for several decades until substantially vindicated by research in the 1950s and 1960s (below). Meanwhile, climax theory was deeply incorporated in both theoretical ecology and in vegetation management. Clements's terms such as pre-climax, post-climax, plagioclimax and disclimax continued to be used to describe the many communities which persist in states that diverge from the climax ideal for a particular area.

Though the views are sometimes attributed to him, Clements never argued that climax communities must always occur, or that the different species in an ecological community are tightly integrated physiologically, or that plant communities have sharp boundaries in time or space. Rather, he employed the idea of a climax community—of the form of vegetation best adapted to some idealized set of environmental conditions—as a conceptual starting point for describing the vegetation in a given area. There are good reasons to believe that the species best adapted to some conditions might appear there, when those conditions occur. But much of Clements's work was devoted to characterizing what happens when those ideal conditions do not occur. In those circumstances, vegetation other than the ideal climax will often occur instead. But those different kinds of vegetation can still be described as deviations from the climax ideal. Therefore, Clements developed a very large vocabulary of theoretical terms describing the various possible causes of vegetation, and various non-climax states vegetation adopts as a consequence. His method of dealing with ecological complexity was to define an ideal form of vegetation—the climax community—and describe other forms of vegetation as deviations from that ideal.[4]

Continuing usage of "climax"

Despite the overall abandonment of climax theory, during the 1990s use of climax concepts again became more popular among some theoretical ecologists.[5] Many authors and nature-enthusiasts continue to use the term "climax" in a diluted form to refer to what might otherwise be called mature or old-growth communities. The term "climax" has also been adopted as description for a late successional stage for marine macroinvertebrate communities.[6]

Additionally, some contemporary ecologists still use the term "disclimax" to describe an ecosystem dominated by invasive species that competitively prevent the re-introduction of once native species. This concept borrows from Clement's earliest interpretation of climax as referring to an ecosystem that is resistant to colonization by outside species. The term disclimax was used in-context by Clements (1936), and despite being an anthropogenic phenomenon which prevents the facilitation and succession to a true climax community, it is one of the only examples of climax that can be observed in nature.[7][8]

References

  1. ^ Cowles, Henry Chandler (1899). "The Ecological Relations of the Vegetation on the Sand Dunes of Lake Michigan". Botanical Gazette 27(2): 95-117; 27(3): 167-202; 27(4): 281-308; 27(5): 361-391.
  2. ^ Clements, Frederic E. 1916. Plant Succession: An Analysis of the Development of Vegetation. Washington D.C.: Carnegie Institution of Washington.
  3. ^ Hagen, Joel B. 1992. An Entangled Bank: The Origins of Ecosystem Ecology. New Brunswick: Rutgers University Press.
  4. ^ Eliot, Christopher. 2007. Method and Metaphysics in Clements’s and Gleason’s Ecological Explanations. Studies in History and Philosophy of Biological and Biomedical Sciences 38(1): 85–109.
  5. ^ See, for example, Roughgarden, Jonathan, Robert M. May and Simon A. Levin, editors. 1989. Perspectives in Ecological Theory. Princeton: Princeton University Press.
  6. ^ Rosenberg R., S. Agrenius, B. Hellman, H. C. Nilsson, and K. Norling. 2002. Recovery of marine benthic habitats and fauna in a Swedish fjord following improved oxygen conditions. Marine Ecology Progress Series 234: 43-53.
  7. ^ Clements, Frederic E. 1936. Nature and Structure of the Climax. Journal of Ecology. Vol. 24, No. 1, pp. 252-284
  8. ^ Johnson, K. 1984. Prairie and plains disclimax and disappearing butterflies, in the central United States. Atala. Vol. 10-12, pp. 20-30

External links

Ballard Down

Ballard Down is an area of chalk downland on the Purbeck Hills in the English county of Dorset. The hills meet the English Channel here, and Ballard Down forms a headland, Ballard Point, between Studland Bay to the north and Swanage Bay to the south. The chalk here forms part of a system of chalk downlands in southern England, and once formed a continuous ridge between what is now west Dorset and the present day Isle of Wight. Old Harry Rocks, just offshore from the dip slope of the down, and The Needles on the westernmost tip of the Isle of Wight, are remnants of this ridge. The scarp slope of the down faces south, over Swanage, meeting the sea as Ballard Cliff.

The down was an area of calcareous grassland for up to 1000 years until World War II, when there was a sudden rise in the need for arable agricultural land. The down is now owned by the National Trust, and has largely been returned to grassland. The National Trust allows grazing on the down to prevent it becoming a natural beech woodland climax community.

The obelisk at Ballard Down commemorates the provision of a new supply of drinking water for Swanage in 1883. It was taken down in 1941 as it was a landmark that might have aided enemy aircraft during World War II, but was re-erected in 1952.

Ballard Down forms the easternmost part of the Jurassic Coast World Heritage Site.The BBC's adaptation of EM Forster's novel 'Howards End' (2017) used Ballard Down as a location.

Beech–maple forest

A beech-maple forest or a maple beech forest is a climax mesic closed canopy hardwood forest. It is primarily composed of American beech and sugar maple trees which co-dominate the forest and which are the pinnacle of plant succession in their range. A form of this forest was the most common forest type in the Northeastern United States when it was settled by Europeans and remains widespread but scattered today.

Boulder Glacier (Washington)

Boulder Glacier is located on the southeast slope of Mount Baker, a stratovolcano near the Pacific coast of North America in the Cascade Range of Washington. Boulder Glacier is the sixth largest on Mount Baker with an area of 1.3 square miles (3.4 km2). It flows from the summit crater between Grant Peak (10,781 ft (3,286 m)) and Sherman Peak (10,141 ft (3,091 m)) to about 5,000 ft (1,500 m). It is noteworthy for retreating 1,610 ft (490 m) between 1987 and 2008, leaving newly exposed rock and soil behind.Between 1850 and 1950, the glacier retreated 8,700 ft (2,700 m). William Long of the United States Forest Service observed the glacier beginning to advance due to cooler and wetter weather in 1953. This was followed by a 2,438-foot (743 m) advance by 1979. The 1979 terminus position is where the small stream enters Boulder Creek from the southwest. Observations in 2005 suggest that the lowest thousand feet or several hundred meters of the glacier is stagnant and will likely disappear. In the pictures, this section of the glacier is gray with rock debris and has few crevasses. On the west side of Boulder Creek is a small waterfall revealed by the recent recession of the glacier.

Boulder Glacier may be approached via the Boulder Ridge Trail number 605. The trail passes through a climax community of pacific silver fir and related species of disparate ages with many standing snags. In the fall, a large variety of mushroom species emerge. Near 4,300 ft (1,300 m) elevation, the trail ascends a lateral glacial moraine. At 4,600 ft (1,400 m) the route ascends about 20 ft (6.1 m) of Class 2 rock and 120 ft (37 m) of steep subalpine forest to reach the ridge crest. Soon thereafter, the trail disappears.

Boulder Ridge consists of scenic heather-covered benches and a number of lateral moraines left by vanished glaciers. Glacial retreat has left the upper portion of the ridge barren and unstable and rockfall from the terminus of that portion of the glacier is a hazard to the unwary visitor.

Boulder Glacier is one of the more popular climbing routes on Mount Baker. First climbed on August 24, 1891, it is most often ascended in combination with the cleaver between Boulder and Park Glacier to the north to bypass densely crevassed sections of the glacier. At about 10,000 ft (3,000 m) elevation, the route passes to the southwest of steep rock and ice to reach the summit ridge east of Grant Peak.

Climax, Saskatchewan

Climax is a village within the Rural Municipality of Lone Tree No. 18, Saskatchewan, Canada. The village is located in the southwestern region of the province, just north of the U.S. border, situated on Highway 18 (E-W) between Frontier and Canuck and on Highway 37 (N-S) between Shaunavon and the Port of Climax.

The community was named after Climax, Minnesota, the home town of early homesteader Christ Fuglestad.

Climax species

Climax species, also called late seral, late-successional, K-selected or equilibrium species, are plant species that will remain essentially unchanged in terms of species composition for as long as a site remains undisturbed. They are the most shade-tolerant species of tree to establish in the process of forest succession. The seedlings of climax species can grow in the shade of the parent trees, ensuring their dominance indefinitely. A disturbance, such as fire, may kill the climax species, allowing pioneer or earlier successional species to re-establish for a time. They are the opposite of pioneer species, also known as ruderal, fugitive, opportunistic or R-selected species, in the sense that climax species are good competitors but poor colonizers, whereas pioneer species are good colonizers but poor competitors. Climax species dominate the climax community, when the pace of succession slows down, the result of ecological homeostasis, which features maximum permitted biodiversity, given the prevailing ecological conditions. Their reproductive strategies and other adaptive characteristics can be considered more sophisticated than those of opportunistic species. Through negative feedback, they adapt themselves to specific environmental conditions. Climax species are mostly found in forests. Climax species, closely controlled by carrying capacity, follow K strategies, wherein species produce fewer numbers of potential offspring, but invest more heavily in securing the reproductive success of each one to the micro-environmental conditions of its specific ecological niche. Climax species might be iteroparous, energy consumption efficient and nutrient cycling.

Cyclic succession

Cyclic succession is a pattern of vegetation change in which in a small number of species tend to replace each other over time in the absence of large-scale disturbance. Observations of cyclic replacement have provided evidence against traditional Clementsian views of an end-state climax community with stable species compositions. Cyclic succession is one of several kinds of ecological succession, a concept in community ecology.

When used narrowly, 'cyclic succession' refers to processes not initiated by wholesale exogenous disturbances or long-term physical changes in the environment. However, broader cyclic processes can also be observed in cases of secondary succession in which regular disturbances such as insect outbreaks can 'reset' an entire community to a previous stage. These examples differ from the classic cases of cyclic succession discussed below in that entire species groups are exchanged, as opposed to one species for another.

On geologic time scales, climate cycles can result in cyclic vegetation changes by directly altering the physical environment.

Ecological succession

Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction.The community begins with relatively few pioneering plants and animals and develops through increasing complexity until it becomes stable or self-perpetuating as a climax community. The "engine" of succession, the cause of ecosystem change, is the impact of established organisms upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment.It is a phenomenon or process by which an ecological community undergoes more or less orderly and predictable changes following a disturbance or the initial colonization of a new habitat. Succession may be initiated either by formation of new, unoccupied habitat, such as from a lava flow or a severe landslide, or by some form of disturbance of a community, such as from a fire, severe windthrow, or logging. Succession that begins in new habitats, uninfluenced by pre-existing communities is called primary succession, whereas succession that follows disruption of a pre-existing community is called secondary succession.

Succession was among the first theories advanced in ecology. Ecological succession was first documented in the Indiana Dunes of Northwest Indiana and remains at the core of ecological science.

Frederic Clements

Frederic Edward Clements (September 16, 1874 – July 26, 1945) was an American plant ecologist and pioneer in the study of vegetation succession.

Lithosere

A lithosere (a sere originating on rock) is a plant succession that begins life on a newly exposed rock surface, such as one left bare as a result of glacial retreat, tectonic uplift as in the formation of a raised beach, or volcanic eruptions. For example, the lava fields of Eldgjá in Iceland where Laki and Katla fissures erupted in the year 935 and the solidified lava has, over time, begun to form a lithosere.

Pioneer species are the first organisms that colonise an area, of which lithoseres are an example. They will typically be very hardy (i.e., they will be xerophytes, wind-resistant or cold-resistant). In the case of a lithosere the pioneer species will be cyanobacteria and algae, which create their own food and water—i.e., they are autotrophic and so do not require any external nutrition (except sunlight). For example, the first lithosere observed after the volcanic explosion of Krakatoa was algae. Other examples of lithoseres include communities of mosses and lichens, as they are extremely resilient and are capable of surviving in areas without soil.

As more mosses and lichens colonize the area, they, along with natural elements such as wind and frost shattering, begin to weather the rock down. This over time creates more soil, leading to increased water retention. Early on, when there is little water, lichens dominate as they are more suited to a lack of water; but as water retention increases, mosses become more dominant as they are faster growing, and these further break the rocks down. The amount of soil is also increased by the decaying mosses and lichens. This improves the fertility of the soil as humus is increased, allowing grasses and ferns to colonise. Over time, flowering plants will emerge, followed by shrubs. As the soil gets progressively deeper, larger and more advanced plants are able to grow. This is the case in Surtsey, a "new", small volcanic island located off the south coast of Iceland. Surtsey was "created" in the 1960s and currently its plant succession has reached the stage where ferns and grasses have begun to start growing in the south of the island where the lava cooled first.As the plant succession develops further, trees start to appear. The first trees (or pioneer trees) that appear are typically fast growing trees such as birch, willow or rowan. In turn these will be replaced by slow growing, larger trees such as ash and oak. This is the climax community on a lithosere, defined as the point where a plant succession does not develop any further—it reaches a delicate equilibrium with the environment, in particular the climate.

In the off chance of a phenomenon which effectively removes most of the lifeforms in these areas, the resultant landscape is considered to be a disclimax, where there is a loss of the previous climax community. Factors which interrupt succession include: human intervention (plagioclimax), change in relief of land (topoclimax), change in animal species (biotic climax) or change in soil such as an increase in acidity (edaphic climax) . In most cases, should the area be left to regenerate as normal when the limiting factor is removed, the area eventually becomes a climax community again (secondary succession).

Old-growth forest

An old-growth forest — also termed primary forest or late seral forest — is a forest that has attained great age without significant disturbance and thereby exhibits unique ecological features and might be classified as a climax community. Old-growth features include diverse tree-related structures that provide diverse wildlife habitat that increases the biodiversity of the forested ecosystem. The concept of diverse tree structure includes multi-layered canopies and canopy gaps, greatly varying tree heights and diameters, and diverse tree species and classes and sizes of woody debris.

Old-growth forests are valuable for economic reasons and for the ecosystem services they provide. This can be a point of contention when some in the logging industry may desire to cut down the forests to obtain valuable timber, while environmentalists seek to preserve the forests for benefits such as maintenance of biodiversity, water regulation, and nutrient cycling.

Old field (ecology)

Old field is a term used in ecology to describe lands formerly cultivated or grazed but later abandoned. The dominant flora include perennial grasses, heaths and herbaceous plants. Old fields are canonically defined as an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community, a concept which has been debated by contemporary ecologists for some time.Old field sites are often marginal lands with soil quality unsuitable for crops or pasture. Examples include abandoned farmlands in central Ontario, along the edge of the Canadian Shield.

Stress tolerant species with wide seed dispersal ranges are able to colonize cultivated fields after their initial abandonment, usually followed by perennial grasses. The succession of old fields culminates in takeover by trees and shrubs.

Plagioclimax community

A Plagioclimax community is an area or habitat in which the influences of the humans have prevented the ecosystem from developing further. The ecosystem may have been stopped from reaching its full climatic climax or deflected towards a different climax by activities such as:

Cutting down the existing vegetation

Burning as a means of forest clearance

Planting trees or crops

Grazing and trampling by domesticated animals

Harvesting of planted cropsThese are known as disturbances, or arresting factors.

In each case, human activity has led to a community which is not the climax community expected in such an area. If the human activity continues, the community will be held in a stable position and further succession will not occur until the human activity ceases.

Priority effect

In ecology, a priority effect is the impact that a particular species can have on community development due to prior arrival at a site.There are two basic types: inhibitory priority effects occur when a species that arrives first at a site negatively impacts a species that arrives later by reducing the availability of space or resources. Facilitative priority effects occur when a species that arrives first at a site alters abiotic or biotic conditions in ways that positively impact a species arriving later. Priority effects are a central and pervasive element of ecological community development. These effects have important implications for natural systems as well as ecological restoration efforts.

Productivity (ecology)

In ecology, productivity refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square metre per day (g m−2 d−1). The mass unit may relate to dry matter or to the mass of carbon generated. Productivity of autotrophs such as plants is called primary productivity, while that of heterotrophs such as animals is called secondary productivity.

Psammosere

A psammosere is a seral community, an ecological succession that began life on newly exposed coastal sand. Most common psammoseres are sand dune systems.

In a psammosere, the organisms closest to the sea will be pioneer species: salt-tolerant species such as littoral algae and glasswort with marram grass stabilising the dunes. Progressing inland many characteristic features change and help determine the natural succession of the dunes. For instance, the drainage slows down as the land becomes more compact and has better soils, and the pH drops as the proportion of seashell fragments reduces and the amount of humus increases. Sea purslane, sea lavender, meadow grass and heather eventually grade into a typical non-maritime terrestrial eco-system. The first trees (or pioneer trees) that appear are typically fast-growing trees such as birch, willow or rowan. In turn these will be replaced by slow-growing, larger trees such as ash and oak. This is the climax community, defined as the point where a plant succession does not develop any further because it has reached equilibrium with the environment, in particular the climate.

In an idealised coastal psammosere model, at the seaward edge of the sand dune the pH of the soil is typically alkaline/neutral with a pH of 7.0/8.0 particularly where shell fragments provide a significant component of the sand. Tracking inland across the dunes a podsol develops with a pH of 5.0/ 4.0 followed by mature podsols at the climax with a pH of 3.5 - 4.5.

Seral community

A seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained. A prisere is a collection of seres making up the development of an area from non-vegetated surfaces to a climax community.

A seral community is the name given to each group of plants within the succession. A primary succession describes those plant communities that occupy a site that has not previously been vegetated. These can also be described as the pioneer community. Computer modeling is sometimes used to evaluate likely succession stages in a seral community.Depending on the substratum and climate, a seral community can be one of the following:

Hydrosere

Community in water

Lithosere

Community on rock

Psammosere

Community on sand

Xerosere

Community in dry area

Halosere

Community in saline body (e.g. a marsh)

Tree

In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years. It is estimated that there are just over 3 trillion mature trees in the world.A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development.

Trees usually reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but tree ferns produce spores instead.

Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies.

Xerosere

Xerosere is a plant succession that is limited by water availability. It includes the different stages in a xerarch succession. Xerarch succession of ecological communities originated in extremely dry situation such as sand deserts, sand dunes, salt deserts, rock deserts etc. A xerosere may include lithoseres (on rock) and psammoseres (on sand).

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