Chap.28 Community Development

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28.1 succession follows an orderly pattern of species replacements.

28.2 Primary succession develops in habitats newly exposed to colonization by plants and animals.

28.3 The intensity and extent of disturbance influence the pattern of secondary succession.

Community Development

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28.4 Succession results from variation in the ability of organisms to colonize disturbed areas and from changes in the environment following the establishment of new species.

28.5 Succession in old fields and glacial areas illustrates the development of the sere.

28.6 Analytical models of succession are based on transitions from one successional stage to the next.

28.7 The character of the climax is determined by local conditions.

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28.1 succession follows an orderly pattern of species replacements.

Primary succession and secondary succession

autogenic succession and allogenic succession

climax and seres continuum index: (Fig. 28-4)

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Fig. 28-1 Stages of succession leading to an oak-horneam forest in southern Poland.

(a) the time just after clear-cutting

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(b) after 7 years.

Fig. 28-1 Stages of succession leading to an oak-horneam forest in southern Poland.

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(c) After 15 years

Fig. 28-1 Stages of succession leading to an oak-horneam forest in southern Poland.

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(d) after 30 years

Fig. 28-1 Stages of succession leading to an oak-horneam forest in southern Poland.

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(e) after 95 years

Fig. 28-1 Stages of succession leading to an oak-horneam forest in southern Poland.

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(f) after 150 years

Fig. 28-1 Stages of succession leading to an oak-horneam forest in southern Poland.

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Fig. 28-2 An old field on the Piedmont of North Carolina. Such habitats develop after abandonment of agricultural land.

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Fig. 28-3 Initial stages of plant succession on sand dunes along the coast of Maryland. (a) Beach grass.

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Fig. 28-3 Initial stages of plant succession on sand dunes along the coast of Maryland. (b) Invasion back

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Fig. 28-4 Relative importance of several tree species in forest communities, arranged along a continuum index. Soil moisture, exchangeable calcium, and pH increase toward the right of the continuum index.

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28.2 Primary succession develops in habitats newly exposed to colonization by plants and animals.

冰河退去，或是火山爆發過後，都可有新生地。新生地的生物群落之發展，就稱為 primary succession 。

早期就進入的生物物種，即稱為 pioneer species 。

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28.3 The intensity and extent of disturbance influence the pattern of secondary succession. Physical disturbance and biological dist

urbance Disturbed sites are colonized from three

sources. 1. The area surrounding the disturbance. 2. Pools of dispersants. 3. The buried seeds or eggs ( 原本存在 ).

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Succession in Marine Epifaunal habitats

Keough investigated the colonization of artificially created patches, ranging in size from 25 to 2,500 cm2, by various subtidal encrusting invertebrates that grow on hard surfaces.

The major epifaunal taxa vary considerably in their colonizing abilities and competitive abilities, which are generally inversely related (Table 28-1)

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Succession in Marine Epifaunal habitats

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Bryozoans and polychaetes are disturbance-adapted species, what botanists call weeds.

They get into open patches quickly, mature and produce offspring at an early age, and then often are eliminated by more slowly colonizing but superior competitors.

Such weedy species require frequent disturbances to stay in the system.

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Succession in rocky intertidal algal communities

Rabbits rarely feed far from the cover of brush or trees to avoid being seen by predators far from safety.

Limpets similarly do not venture far from the safety of mussel beds to feed on algae.

Because this behavior limits their foraging range (Fig. 28-5), densities of limpets in the small patches exceeded those in the large patches.

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Fig. 28-5 A natural cleared patch in a bed of mussels. The patch about 1 m across and has been colonized by a heavy growth of the green alga.

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Succession after disturbance by fire

The intensity of a fire is determined by a number of factors, including the types, amount, and location of available fuel, moisture conditions, and the direction and strength of winds.

A fire in the crown of stands of the trees opens the cones, releasing the seeds, a phenomenon called serotiny.

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28.4 Succession results from variation in the ability of organisms to colonize disturbed areas and from changes in the environment following the establishment of new species.

Two factors interact to determine the position of a species in a sere: 1. the life history characteristics of the

species and 2. the nature of the changes that occur

through the course of succession.

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1. Life history features and succession

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Fig. 28-6 Relationship between seed weight and mortality of seedlings after 3 months under shaded conditions.

The survival of seedlings in shade is directly related to seed weight.

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2. Effects of species on one another

Connell and Slatyer (1977) suggested three mechanisms by which the presence of one species affects the others. (1) Facilitation (2) Inhibition (3) Tolerance

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28.5 Succession in old fields and glacial areas illustrates the development of the sere.

Three mechanisms and the life history characteristics of species are important in every sere.

Succession in an old field (Fig. 28-8) (Fig. 28-9)

Succession in an area of glacial retreat (Fig. 28-10) (Fig. 28-11)

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Fig. 28-8 Schematic summary of the life histories of five early successional species of plants that colonize abandoned fields in North Carolina.

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Fig. 28-9 Growth response of aster (dry weight) and soil water content as a function of distance from broomsedge plants in an old field.

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Fig. 28-10 A valley exposed by a receding glacier, visible at the top center, in North Tongass National Forest, Alaska.

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Succession in an area of glacial retreat

Four different successional stages have been identified in the glacier area.

1. A pioneer stage, consisting of blue-green algal mats, lichens, liverworts, some forbs, and a scattering of willows, cottonwoods, and spruce, along with a mat-forming dwarf shrub that is capable of fixing nitrogen.

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2. A second stage characterized by a thick mat of Dryas, interspersed with a few willows, cottonwoods, alder, and spruce, that emerges about 30 years after deglaciation. This stage is referred to as the Dryas stage.

3. A third stage, featuring alder, that appears after about 50 years, called the alder stage.

4. A spruce climax stage, appearing after about 100 years.

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Fig. 28-11 Diagram showing the complex influences of early successional stages on the establishment of spruce seedlings at Glacier Bay, Alaska.

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生態體系的演進 (succession)

(1) 它是一種有次序的過程，且是具有方向性的，因此是可以預測的。

(2) 它是由於群落 (群落是在某一地區內，各種生物種類的集合 )對於其生存環境的改變所造成的。雖然其生存環境決定演進的形態、演進的速率以及限制演進最終所能達到的界線，然而演進過程卻是由生態體系中的生物本身 (即是群落 )所控制。

(3) 演進的最高峰是一個穩定的生物體系，在其內的所有生命體能共同生活且其內的能量遞移及物質的循環效率達到最高。它們均在增加控制其生活環境的能力以及維持其生活環境平衡的能力。因而使保護生命的能力達到最高且使整個體系免於動盪不安。

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28.6 Analytical models of succession are based on transitions from one successional stage to the next.

Fig. 28-12 Markov process model. A state vector, N, and matrix transition probabilities, P, in a system in which two species (A and B) colonize open space (O) or replace each other.

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Fig. 28-13 Transition probabilities for successional systems behaving according to different models of species interaction.(a) Facilitation model.

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Fig. 28-13 Transition probabilities for successional systems behaving according to different models of species interaction.(b) Inhibition model.

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Fig. 28-13 Transition probabilities for successional systems behaving according to different models of species interaction.(c) Tolerance model.

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Fig. 28-13 Transition probabilities for successional systems behaving according to different models of species interaction.(d) Cyclic model.

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Fig. 28-14 Diagram of the relationships between the three states of the Larrea-Ambrosia communities of the deserts of Arizona.Markovian Dynamics in a desert plant community.

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McAuliffe used a variety of information about plant densities, mortality rates, wood decay rates, and recruitment to calculate transition probabilities for a simple Markov transition matrix (Table 28-3)

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The results of this analysis show considerable concordance between the predictions of the Markov model and the communities observed.

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Markovian dynamics in a forest community

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Fig. 28-15 Predicted transitions in a deciduous forest community near Princeton based on the probabilities shown in Table 28.5. (a) The thickness of the arrows are proportional to the transition probabilities. (b) The sizes of the circles represent the relative abundances of each species.

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28.7 The character of the climax is determined by local conditions.

In the absence of strong disturbance, succession eventually leads to a situation in which environmental conditions change slowly and newly invading species are not able to replace existing species at a site.

The end of successional change does not mean the end of community development.

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Fig. 28-16 Composition of a forest undisturbed for 67 years.

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Nature of the Climax

Monoclimax theory sub-climax, preclimax, postclimax

polyclimax theory pattern-climax theory transient climaxes cyclic climax

stable cyclic climaxes

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Fig. 28-17 (a) A stand of longleaf pine in North Carolina shortly after a fire.

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(b) their growing shoots are protected by the dense, long needles, shown on an unburned individual (c)

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Fig. 28-18 Zebras and Thompson's gazelles feed side by side in the Serengeti ecosystem, but utilize different food plants.

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Fig. 28-19 Vultures feeding on a wildebeest carcass in Masai Mara Park.

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Fig. 28-20 Waves of regeneration in balsam fir forests on the slopes of Mt. Katahdin.

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Fig. 28-21 Sequence of wind damage and regeneration in the dwarf heaths of northern Scotland.

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Suggested readings Callaway, R. M. and F. W. Davis (1993) veget

ation dynamics, fire, and the physical environment in coastal central California. Ecology 74:1567-1578.

Christernsen, N. L. and R. K. Peet (1984) Convergence during secondary forest succession. Journal of Ecology 72:25-36.

Connell, J. H. and R. O. Slatyer (1977) Mechanisms of succession in natural communities and their role in community stability and organization. American Naturalist 111:1119-1144.

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Keough, M. J. (1984) Effects of patch size on the abundance of sessile marine invertebrates, Ecology 65:423-437.

Riggan, P. J., S. Goode, P. M. Jacks and R. N. Lockwood (1988) Interaction of fire and community development in chaparral of southern California. Ecological Monographs 58:155-176.

Sousa, W. P. (1984) Intertidal mosaics: Patch size, propagule availability, and spatially variable patterns of succession. Ecology 65:1918-1935.

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