Basic properties of phytocenoses. The simplest methods for geobotanical description of phytocenoses. The structure of phytocenoses should be understood

The term phytocenosis and the derived science name phytocenology (the science of plant communities, the relationships of plants with each other in conditions of joint growth) were proposed by the Austrian geobotanist Helmut Gamay in 1918.

The concept of phytocenosis, or plant community, is one of the central ones in phytocenology and in.

A plant community is an open biological system that represents a significant part (in material and energy terms) of a more complex bioinert system - biogeocenosis, consisting of plants, mainly autotrophic (phototrophs), which are in complex relationships with each other, with other components and with an environment that, as a result of the vital activity of its autotrophic components, carries out the fixation of solar energy and - with the participation of other organisms - its transformation and the biological cycle of substances, as well as the fixation of atmospheric nitrogen and has a certain composition and a more or less homogeneous structure within the occupied space.

In other words, a phytocenosis, or plant community, must be called any collection of both higher and lower plants that live on a given homogeneous area of ​​the earth’s surface, with relationships unique to them both among themselves and with habitat conditions.

From these definitions follow two more specific, but very important comments:

a) combinations of plants existing in nature, in which there are practically no relationships between plants, are not phytocenoses; these combinations are called plant groups (for example, vegetation of steep rock walls, vegetation of high Arctic islands, etc.);

b) combinations of plants artificially created by man - forest plantations, crops, etc. - correspond to phytocenoses in almost all respects; In order to separate natural communities from human-created communities, the concept of agrophytocenoses (agrocenoses) was introduced.

Morphological structure of phytocenoses

The morphological structure of any system is determined by the spatial relative position of individual structural elements.

As a rule, phytocenoses can be divided into elementary structures that are fairly well delimited in space (vertically and horizontally), and sometimes in time. They are usually called price elements.

The main cenoelements of phytocenoses include tiers and microgroups. The former characterize the vertical, the latter - the horizontal division of plant communities.

Vertical structure

The layering was first described by the Austrian scientist L. Kerner in 1863. In the spruce forest, he distinguished: the tree layer, the fern layer and the moss layer. Then the Swedish scientist Gult identified 7 tiers in the forests of northern Finland: 1) upper arboreal, 2) lower arboreal, 3) undergrowth, 4) upper herbaceous, 5) middle herbaceous, 6) lower herbaceous, 7) ground.

The vertical structure has two polar options, connected by smooth transitions: tiered and vertical continuum. Thus, layering is not a mandatory characteristic, but different heights of plants are a widespread phenomenon.

Tiering allows species of different ecological qualities to coexist in a community, makes the habitat more ecologically capacious, and creates a large number of ecological niches, especially in relation to the light regime.

In the series single-tiered - two-tiered - multi-tiered - imperfectly layered (vertical-continuous) communities, an increase in floristic richness is observed.

The consistent use of the concept of tiering has a number of theoretical difficulties due to the fact that:

1) not all communities are vertically discrete;

2) it is unclear whether tiers are layers or elements “inserted” into each other;

3) it is unclear where to include vines, epiphytes, and undergrowth.

To overcome these difficulties, Yu. P. Byalovich formulated the idea of ​​a biogeocenotic horizon - a vertically isolated and vertically indivisible structural part of the biogeocenosis. From top to bottom, it is homogeneous in the composition of biogeocenotic components, in their interrelationships, the transformations of matter and energy occurring in it, and in these same respects it differs from the neighboring, higher and lower located, biogeocenotic horizons.

The vertical parts of plant communities, accordingly, form phytocenotic horizons. Each of them is characterized not only by the composition of autotrophic plant species, but also by a certain composition of the organs of these plants. With this approach to the analysis of vertical structure, controversial issues disappear, including where to classify lianas, epiphytes or undergrowth.

Horizontal structure

Most plant communities are characterized by heterogeneity of horizontal composition. This phenomenon is called mosaic phytocenoses. Mosaic elements are most often called microgroups, although a number of researchers have proposed their own terms - microphytocenoses, coenoquants, coenocells. The concept of a parcel stands apart. - element of horizontal heterogeneity of biogeocenosis.

The uneven distribution of species is due to a number of reasons. There are types of mosaics based on their origin:

1) Phytogenic mosaic caused by competition, changes in the phytoenvironment or the specific life forms of plants (the ability for vegetative propagation and the formation of clones).

2) Edaphotopic mosaic, associated with the heterogeneity of the edaphotope (irregularities in the microrelief, different drainage, heterogeneity of soils and litter, their thickness, humus content, granulometric composition, etc.).

3) Zoogenic mosaic caused by the influence of animals, both direct and indirect (mediated) - eating, trampling, laying excrement, and the activity of burrowing animals.

4) Anthropogenic mosaic is associated with human activity - trampling due to recreational load, grazing of farm animals, mowing of grass and cutting down of forest plant communities, resource harvesting, etc.

5) Exogenous mosaic, caused by external abiotic environmental factors - the influence of wind, etc.

Mosaic - special case horizontal heterogeneity of vegetation cover. When studying the horizontal heterogeneity of vegetation in a region, researchers distinguish between two concepts, two circles of phenomena - mosaic and complexity.

In contrast to mosaicism, which characterizes intracenotic horizontal heterogeneity, complexity is the horizontal heterogeneity of vegetation cover at the supraphytocenotic level. It manifests itself in the natural alternation of individual phytocenoses or their fragments within the same landscape.

The complexity of the vegetation cover is determined by micro-or mesorelief, which serves as a kind of redistributor of the load of the main environmental factors and thereby differentiates the landscape into habitats with different ecological regimes.

There are complexes and combinations of communities. Complexes - communities, related friend with a friend genetically, i.e. being successive stages of one succession process.

Sometimes they talk about the sinusial structure of plant communities, thus highlighting the special structural elements of the phytocenosis - synusia.

Synusia are structural parts of a plant community, limited in space or time (i.e., occupying a certain ecological niche) and differing from one another in morphological, floristic, ecological and phytocenotic terms.

The synusia of spring forest ephemeroids, the “pseudo-meadow” synusia in deserts, or the synusia of annuals in some types of vegetation are well distinguished in deciduous forests.

Community dynamics. Succession. Mechanisms and causes of succession

Among the most important features of phytocenoses is their variability over time. In nature, there are 2 classes of phenomena - variability and change.

Variability is characterized by the following features:

a) it takes place against the background of an unchanged floristic composition;

b) the observed changes are reversible;

c) the observed changes are undirected.

Shifts, on the contrary, are characterized by:

a) variability of floristic composition;

b) irreversibility of changes;

Quantitative relationships between species

Floristic composition is a very important, but far from exhaustive, characteristic of a plant community. In practice, it is quite possible (not to mention the theoretical possibility) to encounter communities that have the same floristic composition, but nevertheless differ significantly from each other in their appearance (as geobotanists say - physiognomy), in a number of structural parameters. These differences are associated with differences in the quantitative ratio between species in communities.

Thus, another important indicator is quantitative relationships between species, for the assessment of which there are several approaches:

a) Number, or “abundance” - the number of conventional counting units (shoots) per unit area of ​​the community. The most widely used quantitative ocular scale is Dru-de-Uranov:

litter 3 - very abundantly - less than 20 cm between shoots.

litter 2 - abundantly - 20-40 cm.

litter 1 - quite abundantly - 40-100 cm.

sp - scattered - 100-150 cm.

sol - rarely - more than 150 cm.

soc - when the view forms a solid wall, background.

rr - 2-3 copies per 100 sq. m.

un is the only copy on the site.

In meadow steppes, for example, this figure is 4 thousand/sq. m., and in the meadows of Taimyr - 6.5-12 thousand/sq.m.

b) Projective coverage.

It is clear that the same number of individuals can play different roles in different communities due to different ages, different sizes and, because of this, different environment-forming properties of species. Differences in abundance also do not reflect differences in the cenotic importance of species. For example, even 20 individuals of wood sorrel (Oxalis acetosella) will not play the same role in the plant community as a single individual of Siberian hogweed (Heracleum sibiricum). Therefore, a very important indicator is projective coverage, which reflects the proportion of the area of ​​projections of organs of individuals of a given plant species relative to the area of ​​the entire community. This indicator is expressed as a percentage. Projective coverage can be estimated quite accurately using instruments; expert review can be done by eye using, for example, the logarithmic six-point scale of T. A. Rabotnov.

c) Weight ratios provide the most accurate assessment of the role of a particular species in a community or ecosystem. This is a very important indicator that speaks about the role of this species in the processes of transformation of matter and energy in a given ecosystem.

The first two approaches are based on the above-ground sphere of the community, but we should not forget that a noticeable, sometimes significant part of the plants, and therefore the phytomass, is “underground” (below the soil level). Moreover, for different types of communities, for different types of vegetation, the ratio of above- and underground phytomass is a fairly constant value and, thus, is an important feature of communities.

d) Volume ratios. In some types of communities, for example in communities of aquatic ecosystems, volumetric ratios are a fairly informative indicator.

Cenotypes and their relationships in the plant community (differences in the coenotic significance of species)

At the beginning of the 20th century, researchers I.K. Pachosky, V.N. Sukachev and others drew attention to the fact that the role of some species in the plant community practically does not change from year to year, while the role of other species changes significantly over the years or over periods years. L. G. Ramensky called these groups of species coenotypes.

“Cenotypes,” according to the ideas of L. G. Ramensky, are groups of plant species with a similar change in their coenotic significance depending on growing conditions or their characteristics life cycle" They identified three groups of coenotypes:

1) violents (siloviki) - plants that are powerful in competitive terms;

2) patients (hardy) - plants that do not have great vitality and growth energy, but are able to withstand harsh environmental conditions;

3) explorants (performers) - weakly competitive plants that are capable of quickly capturing habitats that are temporarily freed from the influence of competitors.

In 1979, the English ecologist J. Grime identified three types of plant life strategies, largely similar to Ramensky’s cenotypes, and also characterized the basic ecological and biological properties and characteristics of plants that allow them to implement these types of strategies in nature.

K - competitors; long-living plants that produce a small number of large seeds, which contain a relatively large amount of reserve substances; have low morphological plasticity;

S - stress-tolerant; plants that have morphological and ecophysiological adaptations to exist in harsh environmental conditions;

g - ruderals; short-lived plants that do not have competitive power; produce large numbers of relatively small seeds; have great morphological plasticity.

Composition and structure of species coenopopulations

A coenotic population, or coenopopulation, is a collection of individuals of the same species in a phytocenosis.

Each coenotic population in a plant community has only its own characteristics - number, sex and age (ontogenetic) composition, productivity, phytomass reserve, etc.

Of particular importance for understanding the history of a population and forecasting its development is the age (ontogenetic) composition. Individuals of a species within a community are in different age states. The following age groups (conditions) are distinguished:

I. viable seeds in the soil, fruits, vegetative primordia and other diaspores;

II. shoots;

III. juvenile (“youthful”) plants;

IV. adult vegetative (virginile) individuals;

V. adult generative individuals;

VI. senile (“senile”) individuals.

In accordance with these age-related conditions The following stages of the life cycle are distinguished: latent, virginal, generative and senile periods. Depending on the ratio of individuals at different stages of the life cycle, several main types of populations are distinguished - normal-type populations, invasive-type populations and regressive-type populations. The first, in which plants of all age groups are equally well represented, can exist in the plant community for an indefinitely long time. Invasive populations, represented by individuals of predominantly “young” age stages, are in the phase of introduction into the plant community; populations of the regressive type consist predominantly of senile individuals, and because of this they gradually disappear from the composition of plant communities.

The study of the composition and structure of coenopopulations has, among other things, important applied significance, making it possible to predict the development of a population, which is important, for example, when addressing issues of protecting rare and endangered plant species, issues of rational use of populations of resource plants, issues of effective control of populations of harmful plants. weeds, etc.

Ecobiomorphic composition of a community, or spectrum of life forms

The concept of “life form” was introduced into scientific use in the 80s of the 19th century by the famous Danish botanist Eugene Warming, professor of botany at the University of Copenhagen, director Botanical Garden in Copenhagen, one of the founders of plant ecology.

The life form of a plant, according to Warming, is “... the form in which the vegetative body of the plant (individual) is in harmony with the external environment throughout its entire life, from cradle to grave, from seed to death...”.

The external appearance of plants (habitus) is determined by the shape and size of their vegetative above-ground and underground organs, which together make up the shoot system and root system. Depending on the conditions, some or even all of the shoots and roots can be significantly modified.

Warming was the first to draw attention to the adaptability of the vegetative sphere of a plant to environmental conditions. This was also emphasized by the largest domestic researchers I.G. Serebryakov and E.M. Lavrenko. They believed that a life form is a peculiar habitus of certain groups of plants, arising in ontogenesis as a result of growth and development in certain environmental conditions and historically developed in given soil-climatic and cenotic conditions as an expression of adaptability to these conditions. Life forms, or ecobiomorphs, are typical adaptive organismal systems that exist in certain environmental conditions.

The reason for the adaptability of plant life forms is the different degrees of conservatism of the vegetative and generative organs. Generative organs as temporary formations “escape” mechanisms natural selection. Only the vegetative sphere falls into this “millstone”. An attached way of life, the inability to respond to changes in the environment behaviorally, like animals, leads to the need to respond with the “vegetative sphere.”

Among the numerous systems of life forms and approaches to their classification, one of the most popular to date is the classification proposed by the Danish botanist K. Raunkier (1918). He very successfully identified from the entire set of plant characteristics one extremely important characteristic that characterizes the adaptation of plants to survive unfavorable seasons - cold or dry. This trait is the position of the renewal buds on the plant in relation to the level of the substrate or snow cover (a very logical thesis, since the adaptability of a trait can be assessed through the prosperity of the species, and prosperity is directly dependent on how successfully it renews). Based on this feature, Raunkier identified 5 groups of life forms:

phanerophytes - Ph (from the Greek phaneros - open), plants with buds open to influence unfavorable factors(trees and large shrubs);

chamephytes - Ch (from the Greek chame - low), plants with relatively low-lying renewal buds, covered with snow in winter;

hemicryptophytes - NK (from the Greek hemi - semi), plants with renewal buds located on the soil surface;

cryptophytes - K (from the Greek cryptos - hidden), plants with renewal buds located below the soil surface level;

therophytes - Th (from the Greek theros - summer), plants that do not have renewal buds, i.e. annuals that overwinter in the form of viable seeds.

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1. Characteristics of phytocenoses

1.1 Forest phytocenosis

1.2 Meadow phytocenosis

1.3 Ruderal phytocenosis

1.4 Coastal aquatic phytocenosis

2. Geobotanical description of phytocenosis

1. Characteristics of phytocenoses

1.1 Forest phytocenosis

Forest phytocenosis is a forest community, a community of woody and non-woody vegetation, united by the history of formation, common development conditions and growing territory, and the unity of the circulation of substances. The forest community reaches its maximum degree of homogeneity within the geographic facies, where different plant species are in complex relationships with each other and with the ecotope. Depending on the ecotope, composition, ecology of tree species, and stage of development, simple (single-tier) and complex (multi-tiered) forest communities are distinguished.

The forest is a complex complex. The parts of this complex are in continuous interaction with each other and environment. In the forest there is a variety of tree and shrub species, their combinations, a variety of ages of trees, the speed of their growth, ground cover, etc.

Thus, the main component of the forest as a whole - woody vegetation, when applied to a separate forest cenosis, receives more defined outlines. A relatively homogeneous collection of trees within these boundaries is called a forest stand. Young woody plants included in the forest phytocenosis, depending on their age and development, are usually called self-seeding or undergrowth in a natural forest. The youngest generation is the seedlings.

IN forest plantation Along with woody vegetation there may also be shrubs. Forest phytocenosis is also characterized by ground cover. Consequently, a stand is a forest area that is homogeneous in terms of tree and shrub vegetation and living ground cover.

1.2 Meadow phytocenosis

Meadow - in a broad sense - is a type of zonal and intrazonal vegetation, characterized by the dominance of perennial herbaceous plants, mainly cereals and sedges, in conditions of sufficient or excessive moisture. A property common to all meadows is the presence of grass and turf, due to which the top layer of meadow soil is densely penetrated by the roots and rhizomes of herbaceous vegetation.

The external manifestation of the structure of meadow phytocenoses is the features of the vertical and horizontal placement in space and time of above-ground and underground plant organs. In the existing phytocenoses, the structure took shape as a result of a long selection of plants that have adapted to growing together in these conditions. It depends on the composition and quantitative ratio of the components of the phytocenosis, their growing conditions, the form and intensity of human impact.

Each stage of development of a phytocenosis corresponds to a special type of their structure, which is associated with the most important property of phytocenoses - their productivity. Individual types of phytocenoses differ greatly from each other in the volume of above-ground environment used by their components. The height of short grass stands is no more than 10-15 cm, tall grass stands are 150-200 cm. Short grass stands are typical mainly for pastures. The vertical profile of the grass stand varies seasonally from spring to summer and autumn.

Different types of meadows are characterized by different distribution of phytomass within the used volume of the environment. The most obvious manifestation of the vertical structure is the distribution of mass in layers (along the horizons) from 0 and further in height.

Typically, the first tier consists of grasses and the tallest species of forbs, the second tier is dominated by low species of legumes and forbs, the third tier is represented by a group of small herb species and rosettes. In lowland (waterlogged) and floodplain meadows, a layer of ground mosses and lichens is often pronounced.

In anthropogenically disturbed grass stands, the typically formed layered structure is also disrupted.

In meadow communities, especially multispecies and polydominant ones, more or less pronounced horizontal heterogeneity of the grass stand is always observed (patches of clover, strawberries, golden cinquefoil, etc.). In geobotany, this phenomenon is called mosaic or microgrouping.

Mosaicism in meadow phytocenoses arises as a result of the uneven distribution of individuals of certain species. And each species, even its age groups, are specific in the vertical and horizontal placement of their aboveground and underground organs. The uneven distribution of species within a phytocenosis is also due to randomness in the dispersion of seeds (bulbs, rhizomes), the establishment of seedlings, the heterogeneity of the ecotope, the influence of plants on each other, the characteristics of vegetative propagation, and the influence of animals and humans.

The boundaries between individual types of mosaics cannot always be clearly drawn. Often the horizontal division of phytocenoses is determined not by one, but by several reasons. Episodic mosaic, along with phytogenic, is the most common. It is especially clearly manifested in the distribution of some species (angelica, hogweed) in places where they are massively seeded (under haystacks, near generative individuals), spots with a predominance of these species appear. Their power and participation in the creation of phytomass initially increases and then decreases due to the massive death of individuals as a result of the completion of the life cycle.

In meadows (as opposed to forests), fine-contour mosaic patterns are common. Meadows are also characterized by the movement of microgroups in space: disappearance in some places and appearance in others. Mosaic patterns are widespread, represented by various stages of vegetation restoration after disturbances caused by deviations from average weather conditions, animals, human activities, etc.

1.3 Ruderal phytocenosis

Ruderal plants are plants growing near buildings, in wastelands, landfills, in forest belts, along transportation routes, and in other secondary habitats. As a rule, ruderal plants are nitrophils (plants that grow abundantly and well only on soils sufficiently rich in assimilable nitrogen compounds). They often have various devices that protect them from destruction by animals and humans (thorns, burning hairs, toxic substances, etc.). Among the ruderal plants there are many valuable medicinal (dandelion, common tansy, motherwort, great plantain, horse sorrel, etc.), melliferous (medicinal and white sweet clover, narrow-leaved fireweed, etc.) and forage (awnless brome, creeping clover, wheatgrass creeping, etc.) plants. Communities (ruderal vegetation) formed by species of ruderal plants, often developing in places completely devoid of ground cover, give rise to restorative successions.

1.4 Coastal aquatic phytocenosis

forest ruderal phytocenosis vegetation

The floristic composition of coastal aquatic vegetation depends on the different environmental conditions of water bodies: the chemical composition of water, the characteristics of the soil composing the bottom and banks, the presence and speed of currents, and pollution of water bodies with organic and toxic substances.

The origin of the reservoir is important in determining the composition of phytocenoses. Thus, floodplain lake-type reservoirs, located in similar natural conditions and characterized by similar hydrological characteristics, have a macrophyte flora similar in composition.

The species composition of plants inhabiting the coastal zone of reservoirs and the aquatic environment is quite diverse. Based on their connection with the aquatic environment and way of life, three groups of plants are distinguished: true aquatic plants, or hydrophytes (floating and submerged); air-water plants (helophytes); coastal aquatic plants (hygrophytes).

2. Geobotanical description of phytocenosis

Area№ 1

5 * 5 meters.

June 11, 2013

Habitat:

Ufa, Foresters Park of Bashkiria

Type of phytocenosis: Forest

Projective soil cover 60%.

Crown density 95%.

Tiering:

1st tier Heart-shaped linden lat. Tnlia cordbta family Tiliaceae;

2nd tier Norway maple Acer platanoides Sapindбceae ;

3rd tier Rough elm Ъlmus glbbra Ulmaceae;

Mountain ash Surbus aucupbria Rosaceae;

4th tier Warty euonymus Euonymus verrucosa Celasfraceae;

Norway maple Acer platanoides Sapindбceae.

Herbaceous layer.

Forest chin Lathyrus sylvestris Fabacea;

Dandelion officinalis Tarbxacum officinble.

Area№ 2

Plot 5 * 5 meters.

June 11, 2013

Habitat:

Type of phytocenosis: Forest.

Projective soil cover 80%.

Crown density 60%.

Tiering:

1 tier Rough elm Ъlmus glbbra Ulmaceae;

2nd tier Norway maple Acer platanoides Sapindбceae;

3rd tier Rowan Surbus aucupbria Rosaceae;

English oak Quйrcus rubur Fagaceae.

Herbaceous layer.

Common thistle Cirsium vulgare Asteraceae;

Primulbceae

Stinging nettle Urtнca diуica Urticaceae;

Forest chin Lathyrus sylvestris Fabacea;

Fragrant bedstraw Galium odoratum Rubiaceae;

Bladder sedge Carex vesicaria Cyperaceae;

Urban gravilate Gthum urbbnum Rosaceae;

Dandelion officinalis Tarbxacum officinble Asteraceae;

Site No. 3.

Plot 2*2 meters.

June 11, 2013

Habitat:

Ufa, Foresters Park of Bashkiria.

Type of phytocenosis: meadow

Grass layer:

· Mouse peas Vncia crbcca LegumesFabaceae;

· Cumin Cbrum cbrvi Apiaceae;

· Buttercup acrid Ranúnculus bcris Ranunculaceae;

· Veronica dubravnaya Veronica chamaedrys Plantaginaceae;

· Chickweed Stellaria Holostea L. Caryophyllbceae;

· Ordinary cuff Alchemilla vulgaris Rosaceae;

Meadow bluegrass Poa pratthnsis Poaceae;

· Bonfire without bones Bromus inermis Pobceae;

· Meadow foxtail Alopecurus pratensis Poaceae;

· Clover Trifolium pratthnse Fabaceae;

· Creeping clover Trifolium repensMoths;

· Green strawberries Fragbria virndis Pink.

Site No. 4

Plot 2*2 meters.

Habitat:

Ufa, Foresters Park of Bashkiria.

Type of phytocenosis: spruce forest

Projective soil cover 2%.

Tiering:

1st tier Norway spruce Pnceabbies Pinaceae;

2nd tier Norway maple Acer platanoides L Sapindбceae;

3rd tier Norway maple Acer platanoides L Sapindбceae.

Herbaceous layer.

Geranibceae;

Dandelion officinalis Tarbxacum officinble Asteraceae.

Site No. 5

Plot 2*2 meters.

Habitat:

Projective soil coverage 100%.

White tar Silthne latifatlia Caryophyllbceae;

Timofey grass Phleum pratense Pobceae;

· Umbrella hawkweed Hieracium umbellatum L Asteraceae;

· High wormwood Artemisia vulgaris L. Asteraceae;

· Common cornflower Leucanthemum vulgare Asteraceae;

· Wild lettuce Lactura scariolaAsteraceae;

Soft bedstraw Galium mollugo Rubiaceae;

· Potentilla erecta Potentnlla erecta Rosaceae;

Field bindweed Convolvulus arvensis L. Convolvulaceae;

· Chamomile, odorless Tripleurospermum inodorum Asteræceae;

Field jarutka Thlbspi arvеnse Brassicaceae;

Violet tricolor Vnola trncolor Violbcea;

· Common bruise Ychium vulgbre Boraginaceae;

Common toadflax Linaria vulgaris Crophulariaceae;

· Ikotnik gray-green Bertеroa incбna Brassicaceae;

· Plantain lanceolate Plantbgo lanceolbta Plantaginaceae;

Velcro spread out Lappula squarrosa, Boraginaceae;

· Wormwood Artemnsia vulgbris Asteraceae;

· Thistle leaves Cirsium heterophyllum Asteraceae.

Site No. 6

Plot 2*2 meters.

Habitat:

G. Ufa, Kirovsky district, base of the slope, monument to Salavat Yulaev.

Type of phytocenosis: ruderal community

Projective soil coverage 100%.

Timothy grass Phleum pratense Pobceae;

· Artemisia vulgaris L. Asteraceae;

· Wild lettuce Lactura scariola Asteraceae;

· Soft bedstraw Galium mollugo Rubiaceae;

· Potentilla erecta Rosaceae;

· Salsify Tragopogon pratensis Asteraceae;

· Elm variegated Coronilla varia Fabaceae ;

· Meadowsweet Filipеndula ulmbria Rosaceae;

· Burnet Sanguisurba officinblis Rosaceae;

· Common bruise Chium vulgbre Boraginaceae;

· Gray-green hickory Bertеroa incбna Brassicaceae;

· Artemisia vulgbris Asteraceae;

· Thistle Cirsium heterophyllum Asteraceae.

Summary table of species and families

Families
Linden cordate lat. Tnlia cordbta
Norway maple Acer platanoides
Rough elm blmus glbbra
Burnet Sanguisurba officinblis
Meadowsweet Filipundula ulmbria
Potentilla erecta erecta
Common mountain ash Surbus aucupbria
Common cuff Alchemilla vulgaris
Green strawberry Fragbria virнdis
City gravilate Gйum urbbnum
Euonymus verrucosa
Cirsium heterophyllum
Common wormwood Artemnsia vulgbris
Chamomile Tripleurospermum inodorum
Meadow salsify Tragopogon pratensis
Wild lettuce Lactura scariola
Dandelion Tarabxacum officinble
Common cornflower Leucanthemum vulgare
Artemisia vulgaris
Umbrella hawksbill Hieracium umbellatum
Common thistle Cirsium vulgare
Stinging nettle Urtнca diуica
Variegated Elm Coronilla varia
Mouse peas Vнcia crбcca
Red clover Trifolium pratіnse
Mouse peas. Vнcia crбcca
Creeping clover Trifolium repens
Forest chin Lathyrus sylvestris
Soft bedstraw Galium mollugo
Fragrant bedstraw Galium odoratum
Bladder sedge Carex vesicaria
Caraway seeds Cbrum cbrvi
Ranunculus bcris
Lanceolate plantain Plantbgo lanceolbta
Veronica chamaedrys
Caryophyllbceae
White tar Silеne latiуlia
Starwort Stellaria holostea
Meadow bluegrass Poa pratіnsis
Timothy grass Phleum pratense
Bromus inermis
Meadow foxtail Alopecurus pratensis
Norway spruce Pнcea bbies
Common stork Erudium cicutbrium
Loosestrife Lysimachia nummularia
Field bindweed Convolvulus arvensis
Ikotnik gray-green Bertеroa incбna
Field lily Thlbspi arvеnse
Tricolor violet Vнola trнcolor
Common bruise Jchium vulgbre
Velcro splayed Lappula squarrosa
Common toadflax Linaria vulgaris
English oak Quйrcus rubur

conclusions

We discovered and analyzed 52 species from 24 families. The average number of species in families is 3. Thus, the following families are classified as leading:

Asteraceae

Thistle leaves Cirsium heterophyllum, wormwood Artemnsia vulgbris, odorless chamomile Tripleurospermum inodorum, meadow salsify Tragopogon pratensis, wild lettuce Lactura scariola, dandelion officinalis Tarbxacum officinble, common cornflower Leucanthemum vulgare, high wormwood Artemisia vulgaris, Umbrella hawksbill Hieracium umbellatum, common thistle Cirsium vulgare.

Rosaceae

Burnet plant Sanguisurba officinblis, meadowsweet Filipеndula ulmbria, Potentilla erecta Potentnlla erecta, mountain ash Surbus aucupria, ordinary cuff Alchemilla vulgaris, green strawberries Fragbria virнdis, urban gravity Gйum urbbnum.

Fabacea

Vyazel multi-colored Coronilla varia, red clover Trifolium pratіnse, mouse peas Vнcia crбcca, creeping clover Trifolium repens, forest rank Lathyrus sylvestris.

Poaceae

Meadow bluegrass Poa pratеnsis, timothy grass Phleum pratense, the fire is boneless Bromus inermis, meadow foxtail Alopecurus pratensis.

Conclusions on phytocenoses.

In forest phytocenosis No. 1, the dominant species were cordate linden. Tnlia cordbta and Norway maple Acer platanoides.

In forest phytocenosis No. 2, rough elm Ъlmus glbbra and Norway maple Acer platanoides.

In the meadow phytocenosis, the dominant species were caraway seeds Cbrum cbrvi, meadow bluegrass Poa pratеnsis, the fire is boneless Bromus inermis, acrid buttercup Ranúnculus bcris.

In the spruce forest, the dominant species was the common spruce Pнcea bbies. Grass cover was sparse, with percentage soil cover less than 5%.

General conclusion.

In forest communities, vegetation was represented more by woody forms, such as heart-shaped linden Tnlia cordbta, Norway maple Acer platanoides, rough elm Ъlmus glbbra, common mountain ash Sуrbus aucupрia, pedunculate oak Quйrcus rуbur. The diversity of herbaceous vegetation was not so great compared to the vegetation of meadows.

In meadow communities dominant families were Poaceae And Fabacea.

In ruderal communities, the dominant family was Asteraceae, represented by species: thistle Cirsium heterophyllum, wormwood Artemnsia vulgbris, odorless chamomile Tripleurospermum inodorum, meadow salsify Tragopogon pratensis, wild lettuce Lactura scariola, dandelion officinalis Tarbxacum officinble, common cornflower Leucanthemum vulgare, high wormwood Artemisia vulgaris, Umbrella hawksbill Hieracium umbellatum.

Thus, we can conclude that each phytocenosis is characterized by certain families. There are also species whose presence is typical for all studied phytocenoses, for example the species Dandelion officinalis Tarbxacum officinble.

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STRUCTURE OF PHYTOCOENOSES

THE IMPORTANCE OF STUDYING THE STRUCTURE OF PHYTOCOENOSES

Considering the formation of phytocenoses, we saw that they arise as a result of plant reproduction in conditions of complex interactions between plants and the environment, between individuals and between plant species.

Therefore, a phytocenosis is by no means a random set of individuals and species, but a natural selection and association into plant communities. In them, certain types of plants are placed in a certain way and are in certain quantitative ratios. In other words, as a result of these mutual influences, each phytocenosis receives a certain structure (structure), both in its above-ground and underground parts.1

The study of the structure of the phytocenosis provides morphological characteristics of the latter. It has a double meaning.

Firstly, the structural features of the phytocenosis are most clearly visible and can be measured. Without an accurate description of the structure of phytocenoses, neither their comparison nor generalizations based on comparison are possible.

Secondly, the structure of a phytocenosis is the design of mutual relationships between plants, the ecotope and the environment of the phytocenosis in given local conditions and on at this stage development. And if so, then the study of the structure makes it possible to understand why the observed phytocenosis developed the way we see it, what factors and what interactions between them were the cause of the structure of the phytocenosis we observed.

This indicative (or indicator) significance of the structure of phytocenoses makes its study the first and most important task in geobotanical research. It is by the floristic composition and structure of the phytocenosis that the geobotanist determines the quality of soils, the nature of local climatic and meteorological conditions, establishes the influence of biotic factors and various forms human activity.

The structure of the phytocenosis is characterized by the following elements:

1) floristic composition of the phytocenosis;

2) the total number and mass of the plant population of the phytocenosis and quantitative relationships between species and groups of species;

3) the state of individuals of each species in a given phytocenosis;

4) the distribution of plant species in the phytocenosis and the division of the phytocenosis into its structural parts based on it.

The distribution of plant species in a phytocenosis can be considered from the perspective of their distribution in the space occupied by the phytocenosis, and from the perspective of their distribution in time. Distribution in space can be considered from two sides: firstly, as a vertical distribution - a tiered (or sinusial) structure and, secondly, as a horizontal one, otherwise called addition and manifested in the mosaic of phytocenoses; distribution in time manifests itself as a change in synusia at different times.

FLORISTIC COMPOSITION OF PHYTOCOENOSES

Floristically simple and complex phytocenoses

Based on the number of species that make up the phytocenosis, floristically simple and floristically complex phytocenoses are distinguished:

simple - from one or a few types, complex - from many types. An extremely simple phytocenosis should consist of individuals of one plant species (or even one subspecies, variety, one race, ecotype, etc.). Such phytocenoses do not exist in natural conditions, or they are extremely rare and are found only in some completely exceptional environment.

Only in artificial pure cultures of bacteria, fungi and other plants can their extremely simple groups be obtained. Under natural conditions, there is only relative simplicity or low floristic saturation of some phytocenoses. These are, for example, natural “pure” thickets of some grasses (thickets of sharp sedge, canary grass, southern reed, etc.), almost weed-free crops, dense young forests, etc. We see them as extremely simple only until out of habit, we take into account only higher plants. But as soon as we remember that in any such thicket there are many species of lower plants - bacteria and other microphytes interacting with each other and with this thicket and with the soil - the relativity of its floristic simplicity becomes obvious. Nevertheless, during geobotanical study they can be considered relatively simple, since the higher plants in them determine the main and visible structural features, and microorganisms are still rarely taken into account in this kind of research (although taking into account their activities is absolutely necessary for understanding many aspects of the life of the phytocenosis of higher plants ).

Floristically complex phytocenoses are more complex the more species they contain and the more diverse they are in ecological and biological terms.

(1929) distinguished phytocenoses:

from one type - aggregation; from several ecologically homogeneous species - agglomeration; from several aggregations or agglomerations that can exist separately - semi-association; from similar aggregations and agglomerations, but capable of existing only together - associations.

Grossheim interpreted these types of phytocenoses as successive “stages” in the development of vegetation cover and its complexity. However, the terms he proposed did not receive general recognition in the indicated sense.

An example of very high floristic complexity, or saturation of higher plant species, is the phytocenoses of tropical rain forests. In tropical forests West Africa on an area of ​​100 m2 found from above 100 species of trees, shrubs and herbs, not counting the huge number of epiphytes growing on the trunks, branches and even leaves of trees. IN former USSR The subtropical forests of the humid regions of Transcaucasia and the lower zones of the southern part of Sikhote-Alin in the Primorsky region are floristically rich and complex, but they still do not reach the complexity of tropical moist forests. The herbaceous communities of Central Russian meadow steppes are complex, where 100 m2 There are sometimes up to 120 or more species of higher plants. In a complex (with undergrowth) pine forest in the suburbs of Moscow on an area of ​​0.5 ha 145 species were found (8 species of trees, 13 species of undergrowth shrubs, 106 species of shrubs and grasses, 18 species of mosses). In taiga spruce forests, floristic saturation is less.

Reasons for differences in floristic complexity of phytocenoses

What determines the degree of floristic complexity, or saturation, of phytocenoses? What environmental features does the floristic richness or, conversely, the poverty of the phytocenosis indicate to us? There are several reasons for this or that floristic complexity, namely:

1. General physical-geographical and historical conditions of the area, on which the greater or lesser diversity of the flora of the area depends. And the richer and more ecologically diverse the flora of an area, the greater the number of species competing for any territory in this area, the greater the number of them, under favorable conditions, can live together in one phytocenosis.

The floristic richness of the Central Russian meadow steppes is replaced in the drier southern and southeastern regions by the much less floristic richness of the phytocenoses of the feather grass steppes. Central Russian oak forests are floristically more complex than coniferous taiga northern forests. Phytocenoses in the lakes of the Kola Peninsula are floristically poorer than similar phytocenoses in more southern lakes. In the Arctic, where the flora of higher plants is poor, the complexity of individual phytocenoses is also low.

2. Edaphic conditions of habitat. If soil and ground conditions are such that they allow the existence of only one or a few species of local flora that are most adapted to these conditions, then only they form phytocenoses (the latter, therefore, turn out to be relatively simple even in areas with a very rich flora). And vice versa, if the ecotope satisfies the requirements of many plant species, they form more complex phytocenoses.

Almost pure thickets of sharp sedge or reeds, thickets of saltwort on salt marshes, or pine forests with a carpet of cladonia on the soil therefore consist of very few species, because the inherent waterlogging in these places or too much poverty or dryness, or salinity of the soil, etc. exclude all other plants. In areas of flooded meadows that annually receive thick deposits of sand or silt, phytocenoses of one or a few species are common that can survive the annual burial of their renewal buds by thick deposits of alluvium. Such are the thickets of the underbelly of the present (Petasitesspurius), bonfireless fire (Bromopsisinermis), ground reed grass (Calamagrostisepigeios) and other plants with long rhizomes that can quickly grow through the sediment that buries them. On soils very rich in nitrates, single-species thickets of creeping wheatgrass sometimes form (Elytrigiarepens) or nettle (Urticadioica) and other nitrophils.

Thus, any extreme conditions lead to the formation of phytocenoses of the simplest structure. In the absence of such extremes, more complex phytocenoses are obtained, which is what we see in the example of most forest, meadow, steppe and other phytocenoses.

3. Sharp variability of the ecological regime. The sharp variability of the water regime especially noticeably increases the floristic richness and ecological heterogeneity of the flora of the phytocenosis. Thus, the spring moistening of the feather grass steppe causes an abundance of ephemerals and ephemeroids, which end the growing season before the onset of dry and hot summer. In water meadows, spring moisture ensures the growth of moisture-loving species; summer dryness limits them, but is favorable for species growing here that are moderately demanding of moisture, but can tolerate spring waterlogging. As a result, a large number of ecologically diverse species are observed, together forming a complex phytocenosis. In some floodplain meadows (Ob River, middle Volga), moisture-loving plants (hydrophytes), for example, bogwort, literally grow side by side (Eleocharispalustris), and many mesophytes, and even xerophytes.

The variability of the light regime can have a similar significance. In oak-broad-leaved forests, every year during the growing season, two periods alternate in lighting: in the spring, when the leaves of trees and shrubs that have not yet blossomed do not prevent the penetration of light, many light-loving plants grow and bloom - Siberian scilla (Scitlasibirica), corydalis (Corydalis) and other spring ephemeroids, the later period - the period of shading by developed foliage - is used by other, shade-tolerant plants.

4. Biotic factors. The most obvious example is the influence of wild and domestic animals on vegetation. Livestock grazing changes soil and soil conditions and the species composition of plant groups: the soil either becomes compacted or, conversely, loosens, hummockiness appears, excrement left by animals fertilizes the soil - in short, the air-water, thermal, and salt regimes change. This entails a change in vegetation. Grazing directly affects plants: grazing and mechanical trampling select species that can withstand this impact.

Pasture combined with varying degrees the influence of climate, soil and original vegetation can contribute to either the complication of the original phytocenoses or their simplification. For example, when grazing hummocks form on damp soil, the hummocky microrelief increases the heterogeneity of the environment and the range of species. When grazing animals on moderately moist soil, the turf is often disturbed, and repeated grazing weakens the dominant plants, which promotes the growth of weedy pasture grasses, i.e., the range of phytocenosis species increases. On the contrary, intensive grazing on dense, turfy soil allows the growth of only a few persistent species. Therefore, many previously floristically complex meadow and steppe phytocenoses, now, with their strong pasture use, have turned into extremely simplified ones, consisting of a few species. Mouse-like rodents that inhabit various phytocenoses and loosen the turf and surface layers of soil with their moves, contribute to the settlement of many plants and thereby create and maintain a more complex structure of the vegetation cover.

5. Properties of some components of phytocenosis. For example, on abandoned arable land with fairly rich soil, often after 1–2 years an almost pure thicket of creeping wheatgrass grows. This plant, quickly spreading with the help of long branched rhizomes, takes over arable land faster than many other plant species that can grow here as well as wheatgrass, but spread more slowly. The latter only gradually penetrate into the wheatgrass phytocenosis and complicate it.

Similar and for the same reason, pure thickets of fireweed and ground reed grass grow in forest burnt areas. Here, as on abandoned arable land, there are all conditions for the growth of many species, i.e., for the formation of complex phytocenoses. But the two named species, having great energy in both seed and vegetative reproduction, spread faster than others. The penetration of other species into such thickets is usually delayed by the saturation of the soil with rhizomes and roots of the pioneer species, as well as by the density of their grass stand. Such thickets, however, quickly thin out, since the species that form them are demanding on soil looseness (aeration), and sometimes on its richness in nitrates; their proliferation compacts the soil, impoverishes it, which leads to self-thinning.

There are also plants that are capable of creating conditions for relatively poor flora coexisting with them and maintaining them for many tens and hundreds of years. That's what spruce is like. In a spruce mossy forest there is strong shading, air and soil humidity, soil acidity, an abundance of slowly and poorly decomposing litter and other features of air and soil environment caused by the spruce itself, allow the settlement under its canopy of a few other species of higher plants adapted to the environment of the spruce forest. It is worth looking at a clearing in the middle of such a forest to be convinced by the abundance of many species that are absent in the surrounding forest that this ecotope is completely suitable for them. This means that the low floristic saturation of the spruce forest is the result of the influence of its environment.

The environment of a plant community can also complicate its floristic composition. For example, under the canopy of forest plantings in the steppe, various forest plants appear over time, and initially simple plantings turn into more complex forest phytocenoses.

Thinking about the reasons for the floristic richness or poverty of phytocenoses, we see that they can all be reduced to three groups of factors: firstly, to the influence of the primary environment (ecotope), secondly, to the influence of the environment of the phytocenosis itself (biotope) and, in -third, to the influence of biotic factors. These reasons operate within the framework of the richness or poverty of the area's flora and its ecological diversity, determined geographically, historically and ecologically.

By finding out the reasons for a particular floristic saturation of each phytocenosis, we thereby clarify its indicative significance for characterizing environmental conditions and the degree of their use by plants.

The degree of floristic saturation indicates the complete use of the environment by the phytocenosis. There are no two species that are completely identical in their relationship to the environment and in their use of it. Therefore than more types is located in a phytocenosis, the more versatile and complete the use of the environment it occupies. Conversely, a phytocenosis consisting of one or a few species indicates incomplete, one-sided use of the environment, often only because there were no other species in the local flora that could grow there. For example, a forest without shrubs uses energy less efficiently solar radiation, rather than a forest with shrubby undergrowth. The undergrowth uses rays passing through the upper canopy of the forest. If there is also grass or green mosses under the undergrowth, then they, in turn, use the light passing through the undergrowth. In a forest without undergrowth, grasses and mosses, all the light penetrating through the tree crowns remains unused.

If we remember that green plants are the only natural agents that convert the energy of solar radiation into organic matter with a huge reserve of chemical energy, then it will become clear how important it is for plant communities to be as complex as possible.

The floristic composition of phytocenoses is sometimes increased artificially. This is achieved by sowing or planting other plant species in phytocenoses, even alien to the local flora, but suitable for the given conditions. Sometimes ecological and phytocenotic conditions are changed for the same purpose.

In Germany and Switzerland, spruce forests are converted into more profitable mixed forests by planting other tree species (beech). Instead of single-species crops of forage cereals and the same crops of legumes, they prefer to cultivate mixed cereal-legume crops, not only because they are more appropriate for improving the soil and the quality of hay, but also because their use of field resources and their productivity are greater than pure crops.

Identification of the complete flora of the phytocenosis

All plant species that make up the phytocenosis depend on the conditions of existence, and each species contributes its share to the formation of the phytocenosis environment. The more fully the floristic composition of the phytocenosis is known, the more data the researcher has to judge environmental factors.

Identifying the full composition is not an easy task even for an experienced florist. Some species of higher plants present in a phytocenosis, at the time of observation, can only be found in the form of rhizomes, bulbs or other underground organs, as well as in the form of seeds in the soil, and because of this they often go unnoticed. It is difficult to determine the species of seedlings and juvenile forms. Recognizing the species of mosses, lichens, and fungi requires special training and skills, and identifying the microflora of a phytocenosis requires a special, complex technique.

When studying the floristic composition, as well as when studying other signs of the structure of a phytocenosis, it is necessary that the phytocenosis occupies an area sufficient to reveal all its features. Even the completeness of recording the floristic composition depends on the size of the recorded area. If there is, for example, a herbaceous phytocenosis of several dozen plant species, then by choosing an area of ​​0.25 m2 to take into account the floristic composition, we will find several species on it. Having doubled the area, we will find on it, in addition to those already noted, species that were absent on the first one, and the general list of species composition will be replenished. With a further increase in area to 0.75–2 m2, etc., the list of species will increase, although with each increase in area the profit in the number of species in general list is made smaller. By increasing the sites to 4 m2, 5 m2, 10 m2, etc., we notice that at sites larger than, for example, 4 m2, there is little or no new addition to the list of species. This means that the 4 m2 area we took is the minimum area for identifying the entire species composition of the phytocenosis under study. If we limited ourselves to a smaller area, it would be impossible to fully identify the species composition. There are areas of vegetation cover that differ from neighboring ones, but are so small in size that they do not reach the area for identifying the floristic composition of the phytocenosis to which they belong. These areas are fragments of phytocenoses.

The term “detection area” has been proposed. Foreign authors use the term “minimum range”.

The area of ​​identification of the species composition of phytocenoses of various types is not the same. It is not the same for different parts of the same phytocenosis. For example, for a moss cover on soil in a forest, 0.25–0.50 m2 is often sufficient to meet all types of mosses present in a given phytocenosis in such a small area. For herbaceous and shrub cover in the same phytocenosis, a platform is required large sizes, often at least 16 m2. For a forest stand, if it consists of several species, the detection area is even larger (from 400 m2).

In various meadow phytocenoses, the minimum area for detecting floristic composition does not exceed or barely exceeds 100 m2. Finnish authors consider an area of ​​64 m2.

Bearing in mind the identification of not only the floristic composition of the phytocenosis, but also various other structural features, in the practice of Soviet geobotanists, when describing a complex forest phytocenosis, it is customary to take a sample area of ​​at least 400–500 m2, and sometimes up to 1000–2500 m2, and when describing herbaceous phytocenoses - about 100 m2 (if the area of ​​the phytocenosis does not reach such dimensions, all of it is described). Moss and lichen phytocenoses often have a detection area of ​​no more than 1 m2.

Phytocenosis (or plant community) is any collection of plants living on a given homogeneous area of ​​the earth’s surface, which are characterized only by relationships both among themselves and by habitat conditions and therefore create their own special environment, phytoenvironment (Sukachev, 1954).

Phytocenosis is any specific grouping of plants throughout the entire space it occupies, relatively homogeneous in appearance, floristic composition, structure, living conditions and characterized by a relatively identical system of relationships between plants and with the habitat (Shennikov, 1964).

Phytocenosis - a set of plants growing together - is part of a biocenosis - a set of organisms living together. The science of biocenoses is called biocenology (from the Greek bios - life). Thus, phytocenology is part of biocenology (Voronov, 1963).

V.N. Sukachev proposed to call biogeocenosis (1940) a plant community together with its animal population and the corresponding area of ​​the earth's surface, characterized by certain properties of microclimate, geological structure, soil and water regime.

The first definition of a plant community was given by G.F. Morozov (1904) for a forest, and then (1908) extended by V.N. Sukachev to all plant communities. The term “phytocenosis” was used by I.K. Pachosky for “pure thickets” (formed by one plant species) in 1915 and for all communities - by Sukachev in 1917 and Gams in 1918.

Phytocenosis, or plant community, is a collection of plants growing together on a homogeneous territory, characterized by a certain composition, structure, structure and relationships of plants both with each other and with environmental conditions. The nature of these relationships is determined, on the one hand, by the vital, otherwise, ecological properties of plants, on the other hand, by the properties of the habitat, i.e. the nature of the climate.

Between plants in a phytocenosis there are relationships of two genera. Firstly, growing nearby, plants of the same species or plants of several species (in a phytocenosis, plants often grow nearby different types) compete with each other for their means of living; There is a struggle for existence between them (in the broad metaphorical sense as Charles Darwin understood it). This competition, on the one hand, weakens plants, but on the other hand, it forms the basis of natural selection - the most important factor in speciation and, consequently, the process of evolution. Secondly, plants in a phytocenosis have a beneficial effect on each other: shade-loving herbs live under the canopy of trees, which cannot grow or grow poorly in open places; Plants with weak climbing or climbing stems—lianas—climb tree trunks and branches of shrubs; epiphytes not connected to the soil settle on them (Sukachev, 1956).

A phytocenosis is characterized by a certain set of plants that form it (species composition), a certain structure and confinement to a certain habitat. Due to changes in the environment by plants, the phytocenosis creates its own environment - the phytoenvironment.

Phytoenvironment is the environment of plant communities (Dudka, 1984).

The term phytocenosis (plant community) can be applied to specific areas of vegetation cover, and to designate taxonomic units of various ranks: for an association, for a formation, for a type of vegetation, etc.

Four types of phytocenose boundaries can be distinguished: sharp, mosaic, edged, diffuse. Sharp boundaries of phytocenoses can be observed both with a sharp change in environmental conditions and with a gradual one. Even with very sharp boundaries, the introduction of the edificator of one community into the outskirts of another community is usually observed. Mosaic boundaries are characterized by the fact that in the contact zone of two phytocenoses there is an inclusion of small areas of one cenosis in the mass of another, i.e., complexes formed by both bordering phytocenoses seem to develop. Border boundaries differ from other boundaries in that in the contact zone there is a narrow border of a community that differs from both bordering communities. Diffuse boundaries are characterized by the gradual replacement in space of one phytocenosis by another.

A phytocenosis with its animal population is a biocenosis. Biocenosis is a collection of plants and animals inhabiting an area of ​​habitat with more or less homogeneous living conditions (biotope), formed naturally or under the influence of human activity, continuously developing and characterized by certain relationships between members of the biocenosis and between the biocenosis and the habitat (Pavlovsky, Novikov, 1950).

A population is a group of individuals of a species that is geographically or ecologically separated from other groups of individuals of the same species. A group of individuals of a species in a phytocenosis represents a population of that species.

Different individuals of the same species in a phytocenosis are present in different states, in other words, the population of each species is heterogeneous in its composition. Its individuals may differ from each other, for example, by age phases. The following main periods of plant life are distinguished: latent period (primary dormancy period); virgin (virgin) period, which includes three states of plants: germination, juvenile (youthful) and prematurity (adult virgin); generative period; senile (senile) period (Rabotnov, 1945, 1950).

There are many definitions of life forms. I.G. Serebryakov (1962) points out that the doctrine of life forms has by now acquired at least two aspects - ecological-morphological and ecological-cenotic, closely related to each other.

From an ecological and morphological point of view, a life form, according to I. G. Serebryakov, is “a peculiar general appearance (habitus) of a certain group of plants (including their above-ground and underground organs - underground shoots and root systems), which arises in their ontogenesis as a result of growth and development under certain environmental conditions. This habit historically arises in given soil and climatic conditions as an expression of the adaptation of plants to these conditions.”

From an ecological-coenotic point of view, a life form is “an expression of the ability of certain groups of plants to spatially disperse and establish themselves in a territory, and to participate in the formation of vegetation cover.”

Raunkier in 1905-1913 built a system of life forms based on the position of plant renewal buds when the plant endures an unfavorable period caused by low temperatures or lack of moisture. This system was subsequently modified and supplemented by I.K. Pachosky (1916), who proposed to base it on the amount of losses that a plant incurs when its organs die off during an unfavorable time of year (Voronov, 1963).

The main characteristics of a phytocenosis include the species and age composition of the plants that form it, as well as its spatial structure.

Species composition of phytocenoses. Each phytocenosis is characterized by its own specific species composition. Its complexity or simplicity is determined by the indicator of species (floristic) saturation, which is understood as the number of species per unit area of ​​the phytocenosis.

According to the value of the species richness index, phytocenoses can be divided into three groups: a) floristically simple, consisting of a small number of species (up to one to two dozen), b) floristically complex, including many dozens of species, c) phytocenoses occupying an intermediate position in species saturation .

The species diversity of phytocenoses is influenced by a number of factors. A certain role in this regard is played by general physical-geographical and historical conditions, on which the species richness of the flora of each specific area depends. And the richer the flora of the area, the more candidate species there will be that can settle in each specific phytocenosis.

The floristic diversity of phytocenoses also depends on habitat conditions: the more favorable they are, the more complex the species composition, and, conversely, floristically simple phytocenoses are formed in unfavorable habitats.

Animals and humans can also influence the species diversity of phytocenoses (Prokopyev, 1997).

Age composition of populations - distribution of individuals of a coenotic population by age and development phases. Plant age is the lifespan of a whole plant or its individual part, from its origin to the moment under study. Age is measured in units of time (calendar age) or the number of laid leaves or plastochrons (physiological age) (Dudka, 1984).

Depending on the ratio of age groups, T. A. Rabotnov (1995) distinguishes three types of coenopopulations: invasive, normal and regressive.

Analysis of the age composition of coenopopulations is important when studying phytocenoses. It makes it possible to clarify the current state of individual coenopopulations and the phytocenosis as a whole, and to predict their direction further development, helps to develop a regime for the rational use of phytocenoses, to solve problems of their optimization and protection (Yaroshenko, 1969).

The vertical structure of phytocenoses is determined by the fact that the plants growing in it have unequal heights, and their root systems penetrate the soil to different depths. As a result, the phytocenosis is divided in the vertical direction (in its above-ground and underground spheres) into separate layers, more or less delimited from each other, which leads to a more complete use of habitat resources by plants.

There are three main elements of the vertical structure: layer, canopy and phytocenotic horizon.

In herbaceous plants, layering is expressed in points.

1 point. Tall plants (stems of cereals and tall forbs).

2 points. Plants of the second highest size (stems of lower grasses, forbs and other plants).

3 points. Low growing plants.

4 points. Mosses, lichens and very low-growing herbaceous plants 1-5 cm in height (Zorkina, 2003).

The horizontal structure of phytocenoses is determined primarily by the nature of the distribution of plants over their area. Currently, it is customary to distinguish between three main types of distribution of cenopopulations - regular, random and contagious.

The uneven distribution of plants in phytocenoses depends on several reasons and, first of all, on the characteristics of their reproduction and growth form. In this regard, V.N. Sukachev (1961) proposed to distinguish between two types of plant growth: 1) solitary growth, in which individuals of the cenopopulation grow separately from each other, developing one, sometimes two or three shoots from the root and multiply exclusively by generative means; 2) group growth is characterized by the fact that individual individuals or their shoots grow crowded in groups.

The following main forms of group growth are distinguished: a) bunch (or bush); b) turf (or cushion); c) patch; d) curtain; d) stain.

Depending on the type of distribution of dominant coenopopulations, two types of horizontal structure arise - diffuse and mosaic. The diffuse structure is characterized by a more or less uniform (homogeneous) horizontal structure. It occurs in cases where the dominant coenopopulations are distributed evenly - according to regular or random types. True, practice shows that completely homogeneous natural phytocenoses practically do not occur, since in nature there are not and cannot be cases of absolutely uniform distribution of all coenopopulations of a phytocenosis. Therefore, we can only talk about a relatively diffuse composition of phytocenoses.

The mosaic structure is characterized by a clearly heterogeneous (spotty) distribution of dominant coenopopulations, as a result of which small areas are distinguished in the phytocenosis, differing from each other in composition and structure. There are three main categories of elements of the mosaic structure: a) elements of a larger volume, standing out within the entire above-ground part of the phytocenosis; b) elements of the smallest volume, standing out within one subordinate tier; c) elements of intermediate volume, standing out within several subordinate tiers. There is great discrepancy in the names of these structural parts of the phytocenosis. Following A. A. Korchagin (1976), they are respectively designated as: a) microcenosis, b) microgroup, c) congregation.

In accordance with the above factors of uneven distribution of cenopopulations, L. G. Ramensky (1938) and T. A. Rabotnov (1974) distinguish the following types of mosaic: 1) episodic; 2) ecotopic; 3) phytogenic; 4) clonal; 5) zoogenic; 6) anthropogenic.

Later, T. A. Rabotnov (1995) added several more types of mosaic: a) age mosaic, associated with a change in the impact of plants on the environment as their age increases; b) demutational mosaic associated with the restoration of vegetation in disturbed areas of the community; c) mosaic caused by the formation of nanorelief by plants - hummocks, pillows, etc.; d) mosaicism that occurs under the influence of two factors, for example, aeolian-phytogenic mosaicism, common in arid regions and caused by the accumulation of wind-blown fine earth in clumps of shrubs.

In the Anglo-American geobotanical literature, patterns or spots are considered as structural parts of the horizontal heterogeneity of the vegetation cover (Korchagin, 1976), which, in the understanding of most authors, do not have definite boundaries and regular repetition. Due to the continuous change in environmental conditions over the area of ​​the phytocenosis, the patterns form a motley carpet of continuously changing unstable combinations of various species. Thus, the patterns differ from the more or less time-stable microcenoses, congregations and microgroups discussed above and are apparently characteristic of some herbaceous phytocenoses with a highly variable structure.

Plant productivity is the amount of organic matter (biomass) produced by one plant per year, and seed productivity is the number of seeds produced by one plant per year. In the same sense as productivity, the terms productivity of phytocenosis, annual growth are used plant mass, productivity (Voronov, 1963).

Community products are organic substances produced by a biocenosis or phytocenosis. They differ: total primary production - the amount of organic matter introduced into the cenosis system by producers through photosynthesis and chemosynthesis; net primary production is the same, but minus the substances spent on respiration and consumed by heterotrophic organisms; total secondary production - the amount of organic matter created by heterotrophic organisms - consumers; net secondary production - the same, but minus the substances spent on respiration and consumed by other heterotrophs; stock of products (Bykov, 1973).

Productivity is the amount of useful products obtained from a certain area of ​​a phytocenosis or agrocenosis (Dudka, 1984).

Phytomass (from the Greek phyton - plant and mass) is the amount (wet, dry or deashed) of plant matter (populations, phytocenoses, etc.) expressed in units of mass, per unit area or volume. In different phytocenoses, the phytomass has different stratigraphy and different fractional composition (Bykov, 1973).

Geobotany

Topic 3

PHYTOCENOSIS

Lecture1

Phytocenosis and its features

Phytocenology

Phytocenology studies plant communities (phytocenoses). The object of study is both natural phytocenoses (forest, meadow, swamp, tundra, etc.) and artificial ones (for example, crops and plantings cultivated plants). Phytocenology is one of the biological sciences that studies living matter at the coenotic level, i.e. at the level of communities of organisms (slide 4-5).

The task of phytocenology includes the study of plant communities from different points of view (composition and structure of communities, their dynamics, productivity, changes under the influence of human activity, relationships with the environment, etc.). Great importance is also given to the classification of phytocenoses. Classification is a necessary basis for studying vegetation cover and for compiling maps of vegetation in various territories. The study of phytocenoses is usually carried out by their detailed description using a specially developed technique. At the same time, quantitative methods are widely used to take into account various characteristics of the phytocenosis (for example, the share of participation of individual plant species in the community).

Phytocenology is not only a descriptive science; it also uses experimental methods. The object of the experiment is plant communities. By influencing the phytocenosis in a certain way (for example, applying fertilizers to a meadow), the response of vegetation to this influence is revealed. The relationships between individual plant species in a phytocenosis, etc. are also studied experimentally.

Phytocenology is of great economic importance. Data from this science are necessary for the rational use of natural vegetation (forests, meadows, pastures, etc.) and for planning economic activities in agriculture and forestry. Phytocenology is directly related to land management, nature conservation, reclamation work, etc. Phytocenological data are used even in geological and hydrogeological surveys (in particular, when searching for groundwater in desert areas).

Phytocenology is a relatively young science. It began to develop intensively only from the beginning of our century. Huge contribution Domestic scientists L.G. contributed to its development. Ramensky, V.V. Alekhin, A.P. Shennikov, V.N. Sukachev, T.A. Rabotnov and others. Foreign scientists also played a significant role, in particular J. Braun-Blanquet (France), F. Clements (USA), R. Whitteker ( USA).

Phytocenosis and its features

According to the generally accepted definition of V.N. Sukacheva, phytocenosis (or plant community) should be called any collection of higher and lower plants that live on a given homogeneous area of ​​the earth’s surface, with only their characteristic relationships both among themselves and with habitat conditions, and therefore creating their own special environment, phytoenvironment(slide 6). As can be seen from this definition, the main features of a phytocenosis are the interaction between the plants that form it, on the one hand, and the interaction between plants and the environment, on the other. The influence of plants on each other occurs only when they are more or less close, touching their aboveground or underground organs. A collection of individual plants that do not influence each other cannot be called a phytocenosis.

The forms of influence of some plants on others are varied. However, not all of these forms have the same importance in the life of plant communities. In most cases, the leading role is played by transabiotic relationships, primarily shading and root competition for moisture and nutrients in the soil. Competition for nitrogenous nutrients, of which many soils contain little, is often particularly intense.

The joint life of plants in a phytocenosis, when they influence each other to one degree or another, leaves a deep imprint on their appearance. This is especially noticeable in forest phytocenoses. The trees that form a forest are very different in appearance from single trees that grow in the open. In the forest, the trees are more or less tall, their crowns are narrow, raised high above the ground. Single trees are much lower, their crowns are wide and low.

The results of the influence of plants on each other are also clearly visible in herbaceous phytocenoses, for example in meadows. Here the plants are smaller in size than when growing alone, they bloom and bear fruit less profusely, and some do not bloom at all. In phytocenoses of any type, plants interact with each other and this affects their appearance and vital condition.

The interaction between plants, on the one hand, and between them and the environment, on the other, takes place not only in natural plant communities. It is also present in those sets of plants that are created by man (sowing, planting, etc.). Therefore, they are also classified as phytocenoses.

In the definition of phytocenosis V.N. Sukachev includes such a feature as the homogeneity of the territory occupied by the phytocenosis. This should be understood as the homogeneity of habitat conditions, primarily soil conditions, within the phytocenosis.

Finally, V.N. Sukachev points out that only a collection of plants that creates its own special environment (phytoenvironment) can be called a phytocenosis. Every phytocenosis, to one degree or another, transforms the environment in which it develops. The phytoenvironment differs significantly from the ecological conditions in an open space devoid of plants (light, temperature, humidity, etc. change).