Ecological succession

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Ecological succession is the process of change in the species structure of an ecological community over time. Ecological succession_sentence_0

The time scale can be decades (for example, after a wildfire), or even millions of years after a mass extinction. Ecological succession_sentence_1

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. Ecological succession_sentence_2

The "engine" of succession, the cause of ecosystem change, is the impact of established organisms upon their own environments. Ecological succession_sentence_3

A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment. Ecological succession_sentence_4

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. Ecological succession_sentence_5

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. Ecological succession_sentence_6

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. Ecological succession_sentence_7

Succession was among the first theories advanced in ecology. Ecological succession_sentence_8

Ecological succession was first documented in the Indiana Dunes of Northwest Indiana and remains at the core of much ecological science. Ecological succession_sentence_9

History Ecological succession_section_0

Precursors of the idea of ecological succession go back to the beginning of the 19th century. Ecological succession_sentence_10

The French naturalist Adolphe Dureau de la Malle was the first to make use of the word succession concerning the vegetation development after forest clear-cutting. Ecological succession_sentence_11

In 1859 Henry David Thoreau wrote an address called "The Succession of Forest Trees" in which he described succession in an oak-pine forest. Ecological succession_sentence_12

"It has long been known to observers that squirrels bury nuts in the ground, but I am not aware that any one has thus accounted for the regular succession of forests." Ecological succession_sentence_13

The Austrian botanist Anton Kerner published a study about the succession of plants in the Danube river basin in 1863. Ecological succession_sentence_14

H. C. Cowles Ecological succession_section_1

Henry Chandler Cowles, at the University of Chicago, developed a more formal concept of succession. Ecological succession_sentence_15

Inspired by studies of Danish dunes by Eugen Warming, Cowles studied vegetation development on sand dunes on the shores of Lake Michigan (the Indiana Dunes). Ecological succession_sentence_16

He recognized that vegetation on dunes of different ages might be interpreted as different stages of a general trend of vegetation development on dunes (an approach to the study of vegetation change later termed space-for-time substitution, or chronosequence studies). Ecological succession_sentence_17

He first published this work as a paper in the Botanical Gazette in 1899 ("The ecological relations of the vegetation of the sand dunes of Lake Michigan"). Ecological succession_sentence_18

In this classic publication and subsequent papers, he formulated the idea of primary succession and the notion of a sere—a repeatable sequence of community changes specific to particular environmental circumstances. Ecological succession_sentence_19

Gleason and Clements Ecological succession_section_2

From about 1900 to 1960, however, understanding of succession was dominated by the theories of Frederic Clements, a contemporary of Cowles, who held that seres were highly predictable and deterministic and converged on a climatically determined stable climax community regardless of starting conditions. Ecological succession_sentence_20

Clements explicitly analogized the successional development of ecological communities with ontogenetic development of individual organisms, and his model is often referred to as the pseudo-organismic theory of community ecology. Ecological succession_sentence_21

Clements and his followers developed a complex taxonomy of communities and successional pathways. Ecological succession_sentence_22

Henry Gleason offered a contrasting framework as early as the 1920s. Ecological succession_sentence_23

The Gleasonian model was more complex and much less deterministic than the Clementsian. Ecological succession_sentence_24

It differs most fundamentally from the Clementsian view in suggesting a much greater role of chance factors and in denying the existence of coherent, sharply bounded community types. Ecological succession_sentence_25

Gleason argued that species distributions responded individualistically to environmental factors, and communities were best regarded as artifacts of the juxtaposition of species distributions. Ecological succession_sentence_26

Gleason's ideas, first published in 1926, were largely ignored until the late 1950s. Ecological succession_sentence_27

Two quotes illustrate the contrasting views of Clements and Gleason. Ecological succession_sentence_28

Clements wrote in 1916: Ecological succession_sentence_29

while Gleason, in his 1926 paper, said: Ecological succession_sentence_30

Gleason's ideas were, in fact, more consistent with Cowles' original thinking about succession. Ecological succession_sentence_31

About Clements' distinction between primary succession and secondary succession, Cowles wrote (1911): Ecological succession_sentence_32

Modern era Ecological succession_section_3

A more rigorous, data-driven testing of successional models and community theory generally began with the work of Robert Whittaker and John Curtis in the 1950s and 1960s. Ecological succession_sentence_33

Succession theory has since become less monolithic and more complex. Ecological succession_sentence_34

J. Ecological succession_sentence_35 Connell and R. Slatyer attempted a codification of successional processes by mechanism. Ecological succession_sentence_36

Among British and North American ecologists, the notion of a stable climax vegetation has been largely abandoned, and successional processes have come to be seen as much less deterministic, with important roles for historical contingency and for alternate pathways in the actual development of communities. Ecological succession_sentence_37

Debates continue as to the general predictability of successional dynamics and the relative importance of equilibrial vs. non-equilibrial processes. Ecological succession_sentence_38

Former Harvard professor F. A. Bazzaz introduced the notion of scale into the discussion, as he considered that at local or small area scale the processes are stochastic and patchy, but taking bigger regional areas into consideration, certain tendencies can not be denied. Ecological succession_sentence_39

Factors Ecological succession_section_4

The trajectory of successional change can be influenced by site conditions, by the character of the events initiating succession (perturbations), by the interactions of the species present, and by more stochastic factors such as availability of colonists or seeds or weather conditions at the time of disturbance. Ecological succession_sentence_40

Some of these factors contribute to predictability of succession dynamics; others add more probabilistic elements. Ecological succession_sentence_41

Two important perturbation factors today are human actions and climatic change. Ecological succession_sentence_42

In general, communities in early succession will be dominated by fast-growing, well-dispersed species (opportunist, fugitive, or r-selected life-histories). Ecological succession_sentence_43

As succession proceeds, these species will tend to be replaced by more competitive (k-selected) species. Ecological succession_sentence_44

Trends in ecosystem and community properties in succession have been suggested, but few appear to be general. Ecological succession_sentence_45

For example, species diversity almost necessarily increases during early succession as new species arrive, but may decline in later succession as competition eliminates opportunistic species and leads to dominance by locally superior competitors. Ecological succession_sentence_46

Net Primary Productivity, biomass, and trophic properties all show variable patterns over succession, depending on the particular system and site. Ecological succession_sentence_47

Ecological succession was formerly seen as having a stable end-stage called the climax, sometimes referred to as the 'potential vegetation' of a site, and shaped primarily by the local climate. Ecological succession_sentence_48

This idea has been largely abandoned by modern ecologists in favor of nonequilibrium ideas of ecosystems dynamics. Ecological succession_sentence_49

Most natural ecosystems experience disturbance at a rate that makes a "climax" community unattainable. Ecological succession_sentence_50

Climate change often occurs at a rate and frequency sufficient to prevent arrival at a climax state. Ecological succession_sentence_51

Additions to available species pools through range expansions and introductions can also continually reshape communities. Ecological succession_sentence_52

The development of some ecosystem attributes, such as soil properties and nutrient cycles, are both influenced by community properties, and, in turn, influence further successional development. Ecological succession_sentence_53

This feed-back process may occur only over centuries or millennia. Ecological succession_sentence_54

Coupled with the stochastic nature of disturbance events and other long-term (e.g., climatic) changes, such dynamics make it doubtful whether the 'climax' concept ever applies or is particularly useful in considering actual vegetation. Ecological succession_sentence_55

Types Ecological succession_section_5

Primary succession Ecological succession_section_6

Main article: Primary succession Ecological succession_sentence_56

Successional dynamics beginning with colonization of an area that has not been previously occupied by an ecological community, such as newly exposed rock or sand surfaces, lava flows, newly exposed glacial tills, etc., are referred to as primary succession. Ecological succession_sentence_57

The stages of primary succession include pioneer microorganisms, plants (lichens and mosses), grassy stage, smaller shrubs, and trees. Ecological succession_sentence_58

Animals begin to return when there is food there for them to eat. Ecological succession_sentence_59

When it is a fully functioning ecosystem, it has reached the climax community stage. Ecological succession_sentence_60

Secondary succession Ecological succession_section_7

Main article: Secondary succession Ecological succession_sentence_61

Successional dynamics following severe disturbance or removal of a pre-existing community are called secondary succession. Ecological succession_sentence_62

Dynamics in secondary succession are strongly influenced by pre-disturbance conditions, including soil development, seed banks, remaining organic matter, and residual living organisms. Ecological succession_sentence_63

Because of residual fertility and pre-existing organisms, community change in early stages of secondary succession can be relatively rapid. Ecological succession_sentence_64

Secondary succession is much more commonly observed and studied than primary succession. Ecological succession_sentence_65

Particularly common types of secondary succession include responses to natural disturbances such as fire, flood, and severe winds, and to human-caused disturbances such as logging and agriculture. Ecological succession_sentence_66

In secondary succession, the soils and organisms need to be left unharmed so there is a way for the new material to rebuild. Ecological succession_sentence_67

As an example, in a fragmented old field habitat created in eastern Kansas, woody plants "colonized more rapidly (per unit area) on large and nearby patches". Ecological succession_sentence_68

Secondary succession can quickly change a landscape. Ecological succession_sentence_69

In the 1900s, Acadia National Park had a wildfire that destroyed much of the landscape. Ecological succession_sentence_70

Originally evergreen trees grew in the landscape. Ecological succession_sentence_71

After the fire, the area took at least a year to grow shrubs. Ecological succession_sentence_72

Eventually, deciduous trees started to grow instead of evergreens. Ecological succession_sentence_73

Secondary succession has been occurring in Shenandoah National Park following the 1995 flood of the Moorman's and Rapidan rivers, which destroyed plant and animal life. Ecological succession_sentence_74

Seasonal and cyclic dynamics Ecological succession_section_8

Main article: Cyclic succession Ecological succession_sentence_75

Unlike secondary succession, these types of vegetation change are not dependent on disturbance but are periodic changes arising from fluctuating species interactions or recurring events. Ecological succession_sentence_76

These models modify the climax concept towards one of dynamic states. Ecological succession_sentence_77

Causes of plant succession Ecological succession_section_9

Autogenic succession can be brought by changes in the soil caused by the organisms there. Ecological succession_sentence_78

These changes include accumulation of organic matter in litter or humic layer, alteration of soil nutrients, or change in the pH of soil due to the plants growing there. Ecological succession_sentence_79

The structure of the plants themselves can also alter the community. Ecological succession_sentence_80

For example, when larger species like trees mature, they produce shade on to the developing forest floor that tends to exclude light-requiring species. Ecological succession_sentence_81

Shade-tolerant species will invade the area. Ecological succession_sentence_82

Allogenic succession is caused by external environmental influences and not by the vegetation. Ecological succession_sentence_83

For example, soil changes due to erosion, leaching or the deposition of silt and clays can alter the nutrient content and water relationships in the ecosystems. Ecological succession_sentence_84

Animals also play an important role in allogenic changes as they are pollinators, seed dispersers and herbivores. Ecological succession_sentence_85

They can also increase nutrient content of the soil in certain areas, or shift soil about (as termites, ants, and moles do) creating patches in the habitat. Ecological succession_sentence_86

This may create regeneration sites that favor certain species. Ecological succession_sentence_87

Climatic factors may be very important, but on a much longer time-scale than any other. Ecological succession_sentence_88

Changes in temperature and rainfall patterns will promote changes in communities. Ecological succession_sentence_89

As the climate warmed at the end of each ice age, great successional changes took place. Ecological succession_sentence_90

The tundra vegetation and bare glacial till deposits underwent succession to mixed deciduous forest. Ecological succession_sentence_91

The greenhouse effect resulting in increase in temperature is likely to bring profound Allogenic changes in the next century. Ecological succession_sentence_92

Geological and climatic catastrophes such as volcanic eruptions, earthquakes, avalanches, meteors, floods, fires, and high wind also bring allogenic changes. Ecological succession_sentence_93

Mechanisms Ecological succession_section_10

In 1916, Frederic Clements published a descriptive theory of succession and advanced it as a general ecological concept. Ecological succession_sentence_94

His theory of succession had a powerful influence on ecological thought. Ecological succession_sentence_95

Clements' concept is usually termed classical ecological theory. Ecological succession_sentence_96

According to Clements, succession is a process involving several phases: Ecological succession_sentence_97

Ecological succession_ordered_list_0

  1. Nudation: Succession begins with the development of a bare site, called Nudation (disturbance).Ecological succession_item_0_0
  2. Migration: refers to arrival of propagules.Ecological succession_item_0_1
  3. Ecesis: involves establishment and initial growth of vegetation.Ecological succession_item_0_2
  4. Competition: as vegetation becomes well established, grows, and spreads, various species begin to compete for space, light and nutrients.Ecological succession_item_0_3
  5. Reaction: during this phase autogenic changes such as the buildup of humus affect the habitat, and one plant community replaces another.Ecological succession_item_0_4
  6. Stabilization: a supposedly stable climax community forms.Ecological succession_item_0_5

Seral communities Ecological succession_section_11

Main article: Seral community Ecological succession_sentence_98

A seral community is an intermediate stage found in an ecosystem advancing towards its climax community. Ecological succession_sentence_99

In many cases more than one seral stage evolves until climax conditions are attained. Ecological succession_sentence_100

A prisere is a collection of seres making up the development of an area from non-vegetated surfaces to a climax community. Ecological succession_sentence_101

Depending on the substratum and climate, different seres are found. Ecological succession_sentence_102

Changes in animal life Ecological succession_section_12

Succession theory was developed primarily by botanists. Ecological succession_sentence_103

The study of succession applied to whole ecosystems initiated in the writings of Ramon Margalef, while Eugene Odum’s publication of The Strategy of Ecosystem Development is considered its formal starting point. Ecological succession_sentence_104

Animal life also exhibit changes with changing communities. Ecological succession_sentence_105

In lichen stage the fauna is sparse. Ecological succession_sentence_106

It comprises few mites, ants and spiders living in the cracks and crevices. Ecological succession_sentence_107

The fauna undergoes a qualitative increase during herb grass stage. Ecological succession_sentence_108

The animals found during this stage include nematodes, insects larvae, ants, spiders, mites, etc. Ecological succession_sentence_109

The animal population increases and diversifies with the development of forest climax community. Ecological succession_sentence_110

The fauna consists of invertebrates like slugs, snails, worms, millipedes, centipedes, ants, bugs; and vertebrates such as squirrels, foxes, mice, moles, snakes, various birds, salamanders and frogs. Ecological succession_sentence_111

Microsuccession Ecological succession_section_13

Succession of micro-organisms including fungi and bacteria occurring within a microhabitat is known as microsuccession or serule. Ecological succession_sentence_112

Like in plants, microbial succession can occur in newly available habitats (primary succession) such as surfaces of plant leaves, recently exposed rock surfaces (i.e., glacial till) or animal infant guts, and also on disturbed communities (secondary succession) like those growing in recently dead trees or animal droppings. Ecological succession_sentence_113

Microbial communities may also change due to products secreted by the bacteria present. Ecological succession_sentence_114

Changes of pH in a habitat could provide ideal conditions for a new species to inhabit the area. Ecological succession_sentence_115

In some cases the new species may outcompete the present ones for nutrients leading to the primary species demise. Ecological succession_sentence_116

Changes can also occur by microbial succession with variations in water availability and temperature. Ecological succession_sentence_117

Theories of macroecology have only recently been applied to microbiology and so much remains to be understood about this growing field. Ecological succession_sentence_118

A recent study of microbial succession evaluated the balances between stochastic and deterministic processes in the bacterial colonization of a salt marsh chronosequence. Ecological succession_sentence_119

The results of this study show that, much like in macro succession, early colonization (primary succession) is mostly influenced by stochasticity while secondary succession of these bacterial communities was more strongly influenced by deterministic factors. Ecological succession_sentence_120

Climax concept Ecological succession_section_14

According to classical ecological theory, succession stops when the sere has arrived at an equilibrium or steady state with the physical and biotic environment. Ecological succession_sentence_121

Barring major disturbances, it will persist indefinitely. Ecological succession_sentence_122

This end point of succession is called climax. Ecological succession_sentence_123

Climax community Ecological succession_section_15

Main article: Climax community Ecological succession_sentence_124

The final or stable community in a sere is the climax community or climatic vegetation. Ecological succession_sentence_125

It is self-perpetuating and in equilibrium with the physical habitat. Ecological succession_sentence_126

There is no net annual accumulation of organic matter in a climax community. Ecological succession_sentence_127

The annual production and use of energy is balanced in such a community. Ecological succession_sentence_128

Characteristics Ecological succession_section_16

Ecological succession_unordered_list_1

  • The vegetation is tolerant of environmental conditions.Ecological succession_item_1_6
  • It has a wide diversity of species, a well-drained spatial structure, and complex food chains.Ecological succession_item_1_7
  • The climax ecosystem is balanced. There is equilibrium between gross primary production and total respiration, between energy used from sunlight and energy released by decomposition, between uptake of nutrients from the soil and the return of nutrient by litter fall to the soil.Ecological succession_item_1_8
  • Individuals in the climax stage are replaced by others of the same kind. Thus the species composition maintains equilibrium.Ecological succession_item_1_9
  • It is an index of the climate of the area. The life or growth forms indicate the climatic type.Ecological succession_item_1_10

Types of climax Ecological succession_section_17

Ecological succession_description_list_2

  • Climatic Climax: If there is only a single climax and the development of climax community is controlled by the climate of the region, it is termed as climatic climax. For example, development of Maple-beech climax community over moist soil. Climatic climax is theoretical and develops where physical conditions of the substrate are not so extreme as to modify the effects of the prevailing regional climate.Ecological succession_item_2_11
  • Edaphic Climax: When there are more than one climax communities in the region, modified by local conditions of the substrate such as soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity, it is called edaphic climax. Succession ends in an edaphic climax where topography, soil, water, fire, or other disturbances are such that a climatic climax cannot develop.Ecological succession_item_2_12
  • Catastrophic Climax: Climax vegetation vulnerable to a catastrophic event such as a wildfire. For example, in California, chaparral vegetation is the final vegetation. The wildfire removes the mature vegetation and decomposers. A rapid development of herbaceous vegetation follows until the shrub dominance is re-established. This is known as catastrophic climax.Ecological succession_item_2_13
  • Disclimax: When a stable community, which is not the climatic or edaphic climax for the given site, is maintained by man or his domestic animals, it is designated as Disclimax (disturbance climax) or anthropogenic subclimax (man-generated). For example, overgrazing by stock may produce a desert community of bushes and cacti where the local climate actually would allow grassland to maintain itself.Ecological succession_item_2_14
  • Subclimax: The prolonged stage in succession just preceding the climatic climax is subclimax.Ecological succession_item_2_15
  • Preclimax and Postclimax: In certain areas different climax communities develop under similar climatic conditions. If the community has life forms lower than those in the expected climatic climax, it is called preclimax; a community that has life forms higher than those in the expected climatic climax is postclimax. Preclimax strips develop in less moist and hotter areas, whereas Postclimax strands develop in more moist and cooler areas than that of surrounding climate.Ecological succession_item_2_16

Theories Ecological succession_section_18

There are three schools of interpretations explaining the climax concept: Ecological succession_sentence_129

Ecological succession_unordered_list_3

  • Monoclimax or Climatic Climax Theory was advanced by Clements (1916) and recognizes only one climax whose characteristics are determined solely by climate (climatic climax). The processes of succession and modification of environment overcome the effects of differences in topography, parent material of the soil, and other factors. The whole area would be covered with uniform plant community. Communities other than the climax are related to it, and are recognized as subclimax, postclimax and disclimax.Ecological succession_item_3_17
  • Polyclimax Theory was advanced by Tansley (1935). It proposes that the climax vegetation of a region consists of more than one vegetation climaxes controlled by soil moisture, soil nutrients, topography, slope exposure, fire, and animal activity.Ecological succession_item_3_18
  • Climax Pattern Theory was proposed by Whittaker (1953). The climax pattern theory recognizes a variety of climaxes governed by responses of species populations to biotic and abiotic conditions. According to this theory the total environment of the ecosystem determines the composition, species structure, and balance of a climax community. The environment includes the species' responses to moisture, temperature, and nutrients, their biotic relationships, availability of flora and fauna to colonize the area, chance dispersal of seeds and animals, soils, climate, and disturbance such as fire and wind. The nature of climax vegetation will change as the environment changes. The climax community represents a pattern of populations that corresponds to and changes with the pattern of environment. The central and most widespread community is the climatic climax.Ecological succession_item_3_19

The theory of alternative stable states suggests there is not one end point but many which transition between each other over ecological time. Ecological succession_sentence_130

Forest succession Ecological succession_section_19

Forests, being an ecological system, are subject to the species succession process. Ecological succession_sentence_131

There are "opportunistic" or "pioneer" species that produce great quantities of seed that are disseminated by the wind, and therefore can colonize big empty extensions. Ecological succession_sentence_132

They are capable of germinating and growing in direct sunlight. Ecological succession_sentence_133

Once they have produced a closed canopy, the lack of direct sun radiation at the soil makes it difficult for their own seedlings to develop. Ecological succession_sentence_134

It is then the opportunity for shade-tolerant species to become established under the protection of the pioneers. Ecological succession_sentence_135

When the pioneers die, the shade-tolerant species replace them. Ecological succession_sentence_136

These species are capable of growing beneath the canopy, and therefore, in the absence of catastrophes, will stay. Ecological succession_sentence_137

For this reason it is then said the stand has reached its climax. Ecological succession_sentence_138

When a catastrophe occurs, the opportunity for the pioneers opens up again, provided they are present or within a reasonable range. Ecological succession_sentence_139

An example of pioneer species, in forests of northeastern North America are Betula papyrifera (White birch) and Prunus serotina (Black cherry), that are particularly well-adapted to exploit large gaps in forest canopies, but are intolerant of shade and are eventually replaced by other shade-tolerant species in the absence of disturbances that create such gaps. Ecological succession_sentence_140

Things in nature are not black and white, and there are intermediate stages. Ecological succession_sentence_141

It is therefore normal that between the two extremes of light and shade there is a gradient, and there are species that may act as pioneer or tolerant, depending on the circumstances. Ecological succession_sentence_142

It is of paramount importance to know the tolerance of species in order to practice an effective silviculture. Ecological succession_sentence_143

See also Ecological succession_section_20

Ecological succession_unordered_list_4

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: succession.