STRUCTURE OF COMMUNITIES
Biocoenosis – community: totality of populations living in the same habitat and time. Union of
populations with determined environmental demand and coordinated behavior. Habitat of
communities is the biotope. It’s a supraindividual organizational unit. Plant community:
phytocoenosis, animal community: zoocoenosis. Diversity expresses the multiplicity of communities.
Genetic erosion and ecological degradation counteract to the variability. Communities can be
characterized by structural and functional features: changes in time or space, extension, feeding
interactions, species variability, flow of material and energy.
Characteristics of biocoenosises: Analytical features: number of individuals (A), density of
individuals, value covering the area expressed in percentage (D), sociability (S) (abundance sole, by
threads or grouped), vitality (viability) (whole lifecycle: developing, e.g. germ stage, mature
vegetative stage, then mature fertile stage, flowering, fruit bearing as well). Synthetic features:
stability, constancy (K), proportion of the population in other populations of the community
expressed in percentage frequency (Fr) proportion of the population within the population
expressed in percentage, fidelity character, accompanying species.
Indicators – lifestyle types: 1. woody plants: overwintering organs and buds are high above the
surface. There are trees and shrubs. 2. Overwintering organs are lower above the surface (10-30 cm),
stem can be woody (dwarf shrubs) and crawling. 3. Perennial herbaceous plants: Overwintering
organs are on the surface or just under surface. Great majority of herbaceous plant belong to this
group. 4. Overwintering organs are deeper in the soil (e.g. onion) or in the water (aquatic plants), 5.
Biannual plants: there isn’t flower in the end of the first year, overwinter, then in the second year
flower and fruit are developed, 6. Annual plants: Bearing fruit within 1 year, then the plant perishes
and only the seed survives, 7. plants living on trees, such as mistletoes.
Flora elements: Expressing the plant geographical character, geographical distribution and the origin
of species living in the examined area,.
TIME DIMENSION OF COMMUNITIES: aspect: Rhythmic recurrence in time of the community’s
members. Seasonal changes of plant communities e.g. deciduous forest in the moderate zone.
Changing of animal communities: changing in daily activity (daylight predators, night predators,
animals active during the night e.g. hedgehog), seasonal changes, e.g. bird migration. Succession:
series of one-way changing during period of time. Partial variation of populations formulating the
community, hereby the habitat is changing: settling and population. Beginner – pioneer –
community: consists of wide tolerant species, Closing – klimax – community: consists of narrow
tolerant species. Types of succession: 1. Natural succession: secular succession e.g. ice ages, (sand
succession: moss, lichen open sand steppe (annual, later perennial species)  closed sand steppe
 juniper steppe (appearance of shrub-level), juniper-poplar steppe (poplar and juniper) sand steppe
oak woods – convallaria oak woods. The time of the process is about 100 years). Biotic succession
e.g. sedimentation of a lake, population of a refuse dump (microscopic protozoan  floating
pondweed, moss  rooted pondweed  cane, reed-mace  bog, carex, sedge waterside areas 
willow, willow scrubs  willow poplar (soft wood) woods (Salicetum albae fragilis)  ash-oak-elm
(hard wood) forests. 2. secondary succession: changing of communities in habitats formed by human
activities (e.g. river control – salinisation). SPATIAL DISTRIBUTION OF COMMUNITIES: Results are
levels vertically, patterns horizontally. Appearance of community’s members in vertical levels: herb
layer, shrub layer, tree layer e.g. observable in nesting birds: arboricol (e.g. finches), dendricol (e.g.
Picidae, Paridae), friticikol (Red-backed Shrike), terricol (bustard). Guild: smaller species group within
the community, which uses the exploits sources. Due to the changing of temperature by higher
altitude above sea level in higher mountains, the vegetation zones change as well. In tropical
mountainous rainforests equatorial vegetation can be found till 1000 meters altitude. Between
altitudes of 1000-2500 meters subtropical and later moderate zone species appear. Between
altitudes of 2000-3500 meters the cold tolerant species of cooler moderate zone appear. Above
altitude of 3500 m there isn’t any vegetation, permanent snow is typical. Pattern: horizontal
distribution of community’s members (e.g. due to the fight for the light, soil and water features,
coverage of the surface by vegetation = VEGETATION)
FOOD CHAINS, FOOD WEBS, FLOW OF MATERIAL AND ENERGY IN BIOCOENOSIS
Food chains create cycling of material and energy, materials remain in the biocoenosis and their
amount is unchangeable  cycle. However, the amount of the created cycling of material and energy
of biocoenosis can differ in different trophic levels (organic material) of the food chains (e.g.
production level, .herbivore level, predation level). In natural biomes material and energy always
flow to the direction of individuals of the population,  dynamic equilibrium state  the energy
balance of natural biomes is balanced. FEEDING STRUCTURE OF BIOCOENOSIS:
FOOD CHAINS: Each population of the community is a link in the food chains. Food chains can be
different, but the initial member is always the same: a plant able to photosynthesis or its decayed
parts. Populations based on their role in the food chain can be: 1. Producers (organisms producing
organic matters), 2. consumers (not able to produce organic matters independently, pick up when it
is ready), 3. reducents and decomposers (consuming decayed plants or animal debris). PRODUCERS:
generate organic matter from air (CO2) and soil water-soluble anorganic materials (e.g. C, O, H, N, P,
K) by using the energy of sunlight, photosynthesis – by photochemical process. Produced amount of
organic matters: floral biomass  determines the number of animals living from it. CONSUMERS:
organisms feeding upon organic matters of other organisms (plants or animals): herbivorous – primer
consumers, 2. carnivorous – secondary consumers, 3. tercier consumers, top predators: predators
that have no predators of their own (excluded parasites), 4. hylophagous – feeding on waste (e.g.
earthworms, dung-eating snails), 5. recuperative – resaving organisms (e.g. planarias, vultures,
hyenas) REDUCENTS (DECOMPODERS) micro and macrosized organisms that decompose and reuse
the organic matters of decayed plants and animals: bacteria and fungi. material cycling of ecosystem
is closed by material circuit. Process of decomposition: 1. crushing (some of the soil animals, macromezofauna), 2. disintegration: humification (formation of humus) + mineralization (decomposition
into mineral particles), (microorganisms). UTILIZATION OF ENERGY – EFFICIENCY – ENERGY LOSS:
energy efficiency is better at lower trophic level; the amount of transferred energy is decreased to
one tenth part by each link. Efficiency of herbivorous food chain is worse than producer level under
it. The shorter the food chain, the better the energy efficiency, namely the food-utilization efficiency.
FOOD CHAIN TYPES: HERBIVOROUS (PLANT-EATER) FOOD CHAIN: living plant herbivorous animal
 predator consuming herbivorous animal predator consuming predator, (e.g. corn field mouse
 weasel  sea eagle); PARASITE FOOD CHAIN): living or decayed plant  herbivorous or
saprophyte animal  parasite  parasite of a parasite, (e.g. grass  sheep sheep nasal bot fly 
parasite fragellary protest  bacterium) SAPROPHYTE FOOD CHAIN: decayed plant  saprophyte
animal  saprophyte predator  predator eating predator (e.g. dead-wood  earthworm 
predator centipede  mole).
FOOD PYRAMID: express the qualitative and quantitative aspects of food chain (body size increases
upwards, number of individuals increases downwards). The law of relative size prevails, as producers
are usually smaller than consumers. There are exceptions as well, e.g. parasite food chains. In natural
ecosystems number of individuals of producers increases, but the number of species decreases from
the Equilibrium to Arctics. FOOD WEB: plenty of well-separated food chains exist in biocoenosis and a
lot of food chains form a complex food network. Incomplete communities: 1. Lack of producers:
deep sea, caves dependant situation, permanent organic matter income, 2. Lack of consumers:
characterized by lack of special functions e.g. fail of pollination, 3. Lack of decomposers: Fail of
decomposition of organic matters, accumulation, peat formation, formation of fossil energy sources
in anaerobic stagnant waters, moorlands.
BIOCHEMICAL CYCLES: cycle of water and biogenic elements (oxygen, carbon, nitrogen, sulphur,
phosphorus, etc.) essential to organisms between living organisms and their geochemical
environment. Materials absorbed by the living organisms from their environment return to the
atmosphere, hydrosphere or lithosphere through cycles, and through food chains return to
organisms again. Biochemical cycles are classified into two big groups: 1. gas cycles, 2. sedimentary
cycles. GAS CYCLES: Cycle of the main components of living organisms (carbon, hydrogen, oxygen,
nitrogen). These elements return to the environment in gaseous condition after the decay of the
organisms; therefore these become directly or indirectly absorbable to other organisms. Process of
gas cycles is more balanced than sedimentary cycles. Carbon cycle: 1. emission: burning of fossil fuels
(by industrial plants, traffic), volcanic activities, breathing of organisms, 2. entryism:
photosynthesizing organism, mostly plants absorb and assimilate it and produce organic matter,
glucose from it (C6H12O6). Nitrogen cycle: 1. atmospheric N2 (nitrogen) accumulates in the soil as
nitrate (NO3) by photochemical and electronic processes, or by activities of nitrogen-fixing bacteria.
2. Get into the plants from the soil by moisture, infiltrate and go further into the animals through the
food chain. Get into the sewage and soil in form of faeces and ammonia (NH3), where bacteria
transfer it into nitrate (nitrification) and atmospheric nitrogen (N2, denitrification). In SEDIMENTARY
CYCLES elements (phosphorus, sulphur, calcium, magnesium, natrium, iron, etc.) are usually stored in
anemoclastic rocks, thus it’s more difficult to return those into the cycle. 36 of the 40 elements
building up the organisms participate in this kind of cycles. Velocity of in sedimentary cycle is not
steady; it can consist of accelerating and slowing periods as well. Phosphorus can be found in soil at
inorganic (e.g. apatite mineral) and organic form (e.g. bird or bat faeces, guano). Its amount is
increased by manuring on agricultural areas, and decreased by mining or rivers that carry it with the
riverwash and deposit it in another place e.g. in seas (sea sediment). LOCAL GEOCHEMICAL CYCLES: it
formulates when cycles of elements occurs in located place, in a biotope or zone. In this case we talk
about local material circuit. It has two stages: 1. firstly, materials build into organic compounds, 2.
Return to the environment disintegrate again into inorganic compounds. These two stages are
repeated several times, therefore the atoms of soil water, populations and air layers close to soil can
exchange during terrestrial conditions.  this process is called local geochemical cycles. Cycles of
carbon, nitrogen, phosphorus and water covers the whole biosphere, not only the lesser or greater
habitats, therefore  these are not local geochemical cycles.