Ecology: Biology of Interactions. III-09. Trends in Successions
In a typical succession sequence (e.g., in an artificial microcosm or during colonization of a new habitat in primary autotrophic succession), fast-growing species dominate first, then are replaced by slower but more competitive species.
III-9. Trends in Succession. Typically, during succession (e.g., in an artificial system - a microcosm, or when colonizing a new habitat during primary autotrophic succession), the processes shown in Fig. III-9.1 are observed. Initially, production increases rapidly, respiration lags behind, and this leads to biomass accumulation. After reaching climax, respiration catches up with production, and all system parameters stabilize. Fig. III-9.1. Change in productivity during autotrophic succession. Species diversity (or, for example, the number of species) during primary autotrophic succession usually increases, reaches a maximum when the climax community has already appeared, and the last serial community has not yet disappeared, and then slightly decreases (Fig. III-9.2). Fig. III-9.2. Dynamics of species diversity during succession. Some of the trends observed in successions are summarized in Table III-9.1, which concerns the "typical" case of primary autotrophic succession. The early series described in the table (inhabiting a relatively favorable environment) differ from the low-productive pioneer communities that settle during primary successions on inhospitable inorganic substrates. Table III-9.1. Typical trends in autotrophic primary succession (after E. Odum, 1975).
|
Early Maturation |
Early series |
Climax |
|
P/R (ratio of gross production to respiration) |
Differs from 1 |
Approximately 1 |
|
P/B (gross production/standing crop) |
High |
Low |
|
B/E (biomass/energy flow) |
Low |
High |
|
Standing crop |
High |
Low |
|
Food chains (see item III-11) |
Linear, mostly grazing |
Branched, many detrital ones |
|
Accumulated organic matter |
Few |
Multiple events |
|
Inorganic biogenic substances |
Free |
Linked |
|
Species diversity |
Low |
High |
|
Biochemical diversity |
Low |
High |
|
The structuredness of the environment |
Free resources are rare, occupied by competitors |
Complex |
|
The width of ecological niches (see item IV-12) |
Wide |
Narrow |
|
Sizes of the organisms |
Small |
Including large ones |
|
Life cycles |
Short, simple |
Complex, long |
|
Mineral cycles |
Open |
Closed |
|
Metabolic rate |
Late |
Reproductive rate |
|
The role of detritus in the regeneration of biogenic elements |
Insignificant |
Substantial |
|
The nature of selection (see item IV-15) |
r- |
K- |
|
r- |
K- |
Quality |
|
Internal mutualism |
Undeveloped |
Developed |
|
Stability (resistance to influences) |
Reproductive rate |
Late |
|
Entropy |
Late |
Reproductive rate |