Ecological Macrosystems

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The term 'biosphere' was proposed (in the present sense) by E. Suess (1831-1914) in 1875. The author said that the term expresses ideas of C. Darwin and J. B. Lamarck about the unity of life. A great contribution to the development of the biosphere theory was made by V. I. Vernadsky (1863-1945). A. Humboldt (1769-1859) in his book Cosmos (1848) first viewed the Earth as a whole. The modern version of the idea is known as the science of Gaia.

Biosphere is separated from environment much better than other biosystems. It is under the influence of space (the solar radiation - the main source of energy, gravity of the Moon - the flows and deceleration of the Earth's revolution) and geological processes in the Earth (volcanism, continental drift, sea transgression and regression, orogeny). The influence of life on geological processes exists, but it is very small and broadened in time. Its connection with environment can be considered as one-way.

Biosphere is a global open system with properties of homeostasis. Its input is the solar radiation and some substances from the Earth's interior; output is biogenic matters, leaving the cycle for a long time. Biosphere is a centralized cybernetic system with life ('biota') as a central controlling subsystem.

The basis of biosphere is the global biogeochemical cycle (see Matter and Matter Flows in the Biosphere). The big abiotic cycle is, first of all, the water cycle; from 5 x 10 kcal, arriving from the Sun to the Earth, approximately one-half is spent for maintenance of this cycle. The small biological cycle is based on the abiotic one. It uses only 0.1-0.2% of the solar energy, but it is very effective because it has very special, information structure. The biological cycle is a multilayer object, consisting really of a lot of different cycles. Particularly, its oldest part and basis is matter cycling between unicellular synthesizers and destructors.

The previous level of the biological systems hierarchy is 'ecosystem' or 'biogeocoenose'. It is a stable self-reproducing system of interrelated populations of different species from some territory and their abiotic environment. The internal environment of ecosystems is relatively stable, all the species are co-adapted.

Ecosystems form biosphere; they are connected (e.g., in winter we breathe oxygen from the tropics and the other hemisphere), but not very closely. Potentially each type of biogeocoenoses can occupy all the Earth, but the competition of other ecosystems (more effective energetically in certain conditions) does not allow this. Existence of different biogeocoenoses exerting 'biological pressure' upon neighbors makes biosphere stable and adaptive. Data on main kinds of ecosystems are represented in Table 2.

A biogeocoenose is characterized by its own type of biological cycling, but really it is a combination of cycles of different nature, which are called 'ecocycles' or 'co-enomes'. They supplement and duplicate each other; their interweaving creates a strong substance of the bio-geocoenose. Similarly to ecosystem, each coenome can become dominant, but it is restrained by the competition with other coenomes for solar radiation and mineral resources (contrary to ecosystems, they are not separated geographically and share a territory). A kernel of the coenome is a species of plant producer; it introduces energy, revolving the cycle. Other important participants

Table 2 Biomass (dry weight) of different ecosystems

Type of ecosystem

Average biomass (kg m 2 )

Total biomass (109t)

Annual production (kg m 2 )

Tropical forests

52

867

3.1

Tropical and subtropical seasonal forests

40

300

2.2

Savannah

4.5

66

1.9

Deserts and semideserts

0.6

11

0.15

Steppe and forest-steppe

2.6

44

0.85

Forests of the temperate zone

37

408

1.2

Bogs

6.5

13

0.45

Taiga

21

253

0.8

Tundra

0.9

7

0.2

Agricultural lands

2

21

0.7

Continental ecosystems, total

13.3

1990

1.25

Open ocean

0.003

1.0

0.15

Zones of upwelling

0.025

0.01

0.5

Shelf

0.02

0.53

0.4

Sargasso and reefs

2

1.2

2.3

Estuaries

1.5

2.1

1.3

Sea ecosystems, total

0.013

4.8

0.18

Total

3.9

1995

0.44

of the process are species of reducers (mainly bacteria and fungi), which decompose dead organic matter and return it to the cycling. On average, plants produce annually 10% of their biomass; biomass of reducers is a hundred times less, that is, they decompose annually 10 times more than their weight.

Species of consumers (mainly animals), feeding on other organisms (in other words, connected with them by 'trophic relations'), form 'food webs' of the ecosystem and stimulate the cycling. Usually, there are not more than four to six trophic levels. Energy transfer between the levels is about 10%. Trophic relations are not so much the struggle for existence; basically, it is the process of co-adaptation.

The competition of coenomes is mainly a competition between their dominant producers. There are different kinds of the producers: powerful 'competitors', low-powerful 'pioneers', and medium-power suppliers 'opportunists'. The following three competitive situations can take place: evident preference for some species; 'hard competition', when powerfulness ofpopulations is similar, but one population should win; and 'soft competition', when populations can coexist.

The competition of producers for ecological resources is a fundamental motivating force of ecosystems global dynamics. Disturbed biogeocoenose returns to its steady state not smoothly, but in discrete steps (stages), repeating partially the process of the biogeocoenose formation. This process, manifesting the ecosystems property of home-ostasis, is called 'succession'. It is a nonlinear process of step-by-step changing dominant plant association, accounted for by insufficient solar energy utilization by first 'undemanding' succession stages, leaving 'energetic space' for the development of next, more effective stages.

The evolution of biogeocoenose proceeds in the direction of maximal utilization of the solar energy, reaching a final state (state of 'climax'). As a rule, the final stage cannot develop during first stages of the succession. During the evolution of producers, more and more effective associations evolved, but they adapted to conditions of some previous biogeocoenoses. Their development is possible after creation at some succession stage of the corresponding ecological conditions.

The succession process is a process of producing information, if the information is understood as complexity of system response to variations of environmental conditions; the information measure achieves an extreme in the climax state. One of the manifestations of the progress in the course of successions (as well as evolution) is increase of 'biodiversity', multiplicity of different forms of life (an evolutionary point of view: God is 'generator of diversity').

According to W. R. Ashby (1955), diversity is necessary for system adaptability; development of life illustrates this statement. As a result of living forms' divergence, creation and infill of niches, a huge number of species have arisen. At present, there exist about 2 million species, and their number during all the history of life is about 1 billion. The data for different taxonomic groups are represented in Table 3. The numbers are approximate: many species are not discovered, and boarders between species are quite relative.

The level of species is more integrated than the bio-geocoenotic one; it is based on common ancestry and allied bonds. The ability of populations to exponential growth, limited by competitive and trophic relations, creates internal energy of the ecosystem, its resilience.

Table 3 Number of species in taxonomic groups of eukaryotes

Number of species,

Organisms

thousands

Protozoa

26

Sponges

5

Coelenterates and

9.1

ctenophores

Worms

36

Flat worms

9

Round worms

15

Annelids

11

Mollusks

107

Arthropoda

1200

Insects

1100

Tentaculata

4.7

Pogonophora

0.1

Echinodermata

6

Semichordates

0.1

Chordates

39

Tunicates

1.1

Cyclostomes

0.1

Fishes

19

Amphibians

2.9

Reptiles

2.7

Birds

8.6

Mammals

3.7

Animals, total

1440

Algae

20

Diatoms

10

Red algae

2.5

Brown algae

1

Green algae

6.5

Mosses

24

Club-mosses

0.4

Pteridophytes

9

Gymnosperms

0.6

Metasperms

250

Plants, total

305

Fungi

105

Lichens

30

Total

1880

The interpopulation relations are not so much struggle for existence as permanent frontier wars, supporting high level of energy of all their participants.

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