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Phytocenosis examples. Composition, structure and structure of phytocenoses. tier Linden cordate lat. Tnlia cordbta family Tiliaceae

Development of views on the nature of phytocenosis

At the dawn of the development of geobotany, the idea of a phytocenosis as a really existing discrete unit of vegetation cover took shape, which at that time seemed quite appropriate, since the identification of individual phytocenoses significantly facilitated the task of studying vegetation as a whole. However, at the beginning of the 20th century, a diametrically opposite point of view was expressed, according to which the vegetation cover seemed continuous, and its division into individual elements- phytocenoses - artificial. The absence of sharp boundaries between plant communities and the presence of transition zones between them contributed to the emergence of the doctrine of continuity of vegetation cover, based on individualistic concept:

Each plant species is individual in its requirements for environmental conditions and has characteristic environmental amplitudes for each environmental factor
Environmental factors change gradually, both in space and time
The transition from one combination of cenopopulations to another occurs continuously: some species gradually decrease their abundance and disappear, others appear and increase.

Extreme supporters of the concept of continuity of vegetation cover considered not a phytocenosis, due to its artificiality, but an individual plant as an object of study of geobotany. Extreme supporters of the idea of discreteness postulated a clear distinction and delineation of individual phytocenoses.

Based on the synthesis of both concepts, the idea of a combination of both discreteness and continuity in the nature of vegetation was put forward. This was presented as one of the manifestations of inconsistency inherent in the material world as a whole. According to this idea, the vegetation cover has the property of continuity, but it is not absolute, but relative. At the same time, it also has the property of discreteness, but this is not absolute, but relative. These properties are organically combined, not excluding, but complementing each other.

Formation of phytocenosis

Primary free area of the earth's surface after a volcanic eruption

The formation of phytocenoses can be considered both in a dynamic aspect (change of communities) and in terms of their formation on free areas of the earth's surface.

Distinguish primarily vacant areas, which in the past were not populated by plants and do not contain their rudiments. Phytocenoses can form on them only when diaspores are introduced from the outside. Such areas include rocky outcrops, fresh river and sea sediments, the exposed bottom of reservoirs, areas freed from glaciers, lava fields, etc. In general, they occupy insignificant areas on Earth.

Secondary vacant areas are formed in places where vegetation previously existed, but was destroyed due to the influence of some unfavorable factor. Examples include burnt areas, scree, unseeded arable land, areas of phytocenoses eaten away by pests or livestock. In most cases, soil and diasporas are preserved on them, and the formation of phytocenoses occurs much faster than in initially free areas.

The formation of a phytocenosis is a continuous process, but can be conditionally divided into stages:

Pioneer group- coenopopulations are small in number, there are no relationships between them
Group-thicket community- coenopopulations are distributed in clumps in which interaction between plants occurs
Diffuse community- coenopopulations mix, a system of interspecific interactions is developed

Migration- introduction of diasporas
Ecesis- consolidation of the first settlers
Aggregation- formation of groups of offspring around mother plants
Invasion- mixing of coenopopulations
Competition- development of competitive relations due to a sharp increase in crowd density
Stabilization- formation of a sustainable closed community

E.P. Prokopiev, summing up the various division schemes of the process of formation of a phytocenosis, proposes to distinguish three stages in it:

Receipt of primordia into a free area. The species composition of the emerging phytocenosis will depend on the species composition of plants in the surrounding area and the nature of the distribution of their diaspores, and the main role will be played by the rudiments of allochoric species, mainly anemochores.
Ecotopic (abiotic) selection. Not all diasporas that land on a free plot will take root on it: some will not germinate, and some of those that have sprouted will die in their young state due to an unfavorable combination of abiotic factors. Established plants will be pioneers for this territory.
Phytocenotic selection. Due to the reproduction and settlement of pioneer species throughout the site, they will begin to influence each other and change the ecotope, forming a biotope (habitat). The primary abiotic environment of the ecotope turns into a secondary biotic - phytoenvironment. Under the influence of the phytoenvironment and the mutual influence of plants, some pioneer species that are not adapted to it fall out. This may occur, for example, due to shading or allelopathy. At the same time, new species, already adapted to the given phytoenvironment, are established on the site.

Factors of phytocenosis organization

Factors in the organization of a plant community can be divided into four groups: characteristics of the environment (ecotope), the relationship between plants, the influence of heterotrophic components (animals, fungi, bacteria) on vegetation and disturbances. These groups of factors determine the combination and characteristics of cenopopulations of species in a phytocenosis.

Ecotop is the main factor in the organization of phytocenosis, although it can be significantly transformed by the biotic influences of plants or disturbances. Abiotic factors influencing community organization include:

climatic (light, heat, water regimes, etc.)
edaphic (granulometric and chemical composition, humidity, porosity, water regime and other properties of soils and soils)
topographic (relief characteristics)

Plant relationships are divided into contact And mediated : transabiotic- through abiotic environmental factors and transbiotic- through third organisms.

Violations, both anthropogenic and natural origin can completely transform the phytocenosis. This occurs during fires, felling, livestock grazing, recreational load, etc. In these cases, derivative phytocenoses are formed, which gradually change towards the restoration of the original one if the impact of the disturbing agent has ceased. If the impact is long-term (for example, during recreation), communities are formed that are adapted to existence at a given level of stress. Human activity has led to the formation of phytocenoses that did not previously exist in nature (for example, communities on toxic industrial waste dumps).

Interactions of organisms in phytocenoses

The presence of a system of relationships between plants is one of the main signs of the existing phytocenosis. Studying them, due to the large overlap and strong influence of abiotic factors, is a difficult task and can be implemented either in the form of an experiment, during which the relationships of two specific species are studied, or by isolating such relationships from a complex of others using methods of mathematical analysis.

Direct (contact) mutual influences

In ecological terms, the relationship between epiphytes and phorophytes is usually represented by commensalism, but elements of competition may also appear:

epiphytes partially intercept light and moisture from phorophytes
by retaining moisture, they contribute to the decay of the phorophyte
By shading the phorophyte, epiphytes reduce its effective photosynthetic surface
growing profusely, can cause deformation or breakage of phorophytes

Transabiotic interactions

The influence of plants on each other, mediated by abiotic environmental factors. They arise due to the overlap of phytogenic fields of neighboring plants. Divided into competition And allelopathy.

Competition develops either due to the initial limitation of habitat resources, or as a result of a decrease in their share per plant due to overpopulation. Competition leads to a decrease in resource consumption by the plant and, as a consequence, a decrease in the rate of growth and storage of substances, and this, in turn, leads to a decrease in the quantity and quality of diaspores. Distinguish inside- And interspecific competition.

Intraspecific competition affects fertility and mortality rates in a coenopopulation, determining the tendency to maintain its numbers at a certain level, when both values balance each other. This number is called maximum density and depends on the amount of habitat resources. Intraspecific competition is asymmetrical - it affects different individuals differently. The total phytomass of the cenopopulation remains constant in a fairly large range of density values, while the average mass of one plant begins to steadily decrease when thickened - law of constant harvest(C=dw, where C is the yield, d is the coenopopulation density and w is the average weight of one plant).

Interspecific competition is also widespread in nature, since the vast majority of phytocenoses (except for some agrocenoses) are multispecies. The multi-species composition is ensured by the fact that each species has an ecological niche characteristic only of it, which it occupies in the community. Moreover, the niche that a species could occupy in the absence of interspecific competition is fundamental, tapers to size implemented. In a phytocenosis, differentiation of ecological niches occurs due to:

different plant heights
different depths of penetration of the root system
contagious distribution of individuals in the population (in separate groups/spots)
different periods of growing season, flowering and fruiting
unequal efficiency of plants' use of habitat resources

With weak overlap of ecological niches, coexistence of two cenopopulations can be observed, while with strong overlap, the more competitive species displaces the less competitive species from the habitat. The coexistence of two highly competitive species is also possible due to the dynamism of the environment, when one species or another gains a temporary advantage.

Allelopathy- the influence of plants on each other and on other organisms through the release of active metabolites into the environment both during the life of the plant and during the decomposition of its remains. Allelopathic activity of one type or another is determined by a certain set of chemical substances of different nature, the qualitative and quantitative composition of which significantly depends on external conditions. Allelopathically active substances are secreted both by above-ground organs (mainly leaves) and underground, mainly in three ways:

active secretion through glands or hydathodes
washout by precipitation
excretion through decomposition of litter by microorganisms

Amount of allocations various plants in a phytocenosis - its biochemical environment. Since the composition of secretions is not constant, we can talk about the existence of an allelopathic regime of phytocenosis, along with water, air, etc.

Transbiotic interactions

Influence of phytocenosis on the environment

Structure of phytocenosis

Depending on the specifics of the research in the concept of “biocenosis structure”, V.V. Masing identifies three directions that he developed for phytocenoses.

1. Structure, as a synonym for composition (specific, constitutional). In this sense, they talk about species, population, biomorphological (composition of life forms) and other structures of the cenosis, meaning only one side of the cenosis - composition in the broad sense. In each case, a qualitative and quantitative analysis of the composition is carried out.

2. Structure, as a synonym for structure (spatial, or morphostructure). In any phytocenosis, plants are characterized by a certain affinity to ecological niches and occupy a certain space. This also applies to other components of the biogeocenosis. Between the parts of the spatial division (tiers, sinusia, microgroupings, etc.) you can quite easily and accurately draw boundaries, you can plot them on the plan, calculate the area, and then, for example, calculate resources useful plants or animal feed resources. Only on the basis of data on the morphostructure can one objectively determine the points at which certain experiments were performed. When describing and diagnosing communities, the spatial heterogeneity of cenoses is always studied.

3. Structure, as a synonym for sets of connections between elements (functional). The basis for understanding structure in this sense is the study of relationships between species, primarily the study of direct connections - the biotic connex. This is the study of chains and nutrition cycles that ensure the circulation of substances and reveal the mechanism of trophic (between animals and plants) or topical (between plants - competition for nutrients in the soil, for light in the above-ground sphere, mutual assistance).

All three aspects of the structure of biological systems are closely interrelated at the coenotic level: the species composition, configuration and placement of structural elements in space are a condition for their functioning, that is, life activity and production. plant mass, and the latter, in turn, largely determines the morphology of cenoses. And all of these aspects reflect the environmental conditions in which the biogeocenosis is formed.

The phytocenosis consists of a number of structural elements. There are horizontal and vertical structure of phytocenosis. The vertical structure is represented by tiers, distinguished by visually determined horizons of phytomass concentration. The tiers consist of plants of “different heights”. Examples of layers are 1st tree layer, 2nd tree layer, ground cover, moss-lichen layer, understory layer, etc. The number of layers may vary. The evolution of phytocenoses is moving in the direction of increasing the number of tiers, as this leads to a weakening of competition between species. Therefore, in more ancient forests temperate zone In North America, the number of layers (8-12) is greater than in similar younger forests of Eurasia (4-8).

The horizontal structure of the phytocenosis is formed due to the presence of tree canopies (under which an environment is formed, somewhat different from the environment in the inter-canopy space), terrain heterogeneities (which cause changes in groundwater levels, different exposures), and the species characteristics of some plants (reproducing vegetatively and forming monospecies “spots” , changes in the environment of one species and the response of other species to this, allelopathic effects on surrounding plants), animal activities (for example, the formation of patches of ruderal vegetation on rodents).

Naturally repeating spots (mosaics) in a phytocenosis, differing in the composition of species or their quantitative ratio, are called microgroups, and such a phytocenosis is mosaic.

Heterogeneity may also be random. In this case it is called variegation.

Dynamics of phytocenoses

dynamic processes: reversible (daily, seasonal, fluctuations) and irreversible (succession, evolution of communities, disturbances of communities). Fluctuations are year-to-year changes associated with unequal conditions for the existence of plants in different years. the composition does not change, the size and age composition of the population may change. Succession is a gradual change in phytocenoses that is irreversible and directional. caused by internal or external reasons in relation to phytocenoses, reasons. primary and secondary successions are distinguished. Primary successions begin on lifeless substrates, while secondary successions begin on substrates on which the vegetation has been disturbed.

Classification of phytocenoses

When classifying phytocenoses, similar communities are combined into groups - classification units.

The lowest unit of classification is association (a set of homogeneous phytocenoses that have more or less the same appearance, similar floristic composition and the same dominant species in tiers). The names of associations are given by listing the Russian names of the dominant plants of each tier of the phytocenosis, starting from the uppermost tier (Scots pine + Norway spruce - lingonberry + blueberry - moss pleurocium) or Latin generic and species names dominants (Pinus sylvestris + Picea abies - Vaccinium vitis-idaea + Vaccinium myrtillus - Pleurozium schreberi) with the addition of suffixes to the base

Phytocenosis is a plant community characterized by relative homogeneity of species composition, determined primarily by habitat conditions, and relative isolation from other communities, consisting of coenopopulations connected by the relations of differentiation of ecological niches and interference, located in conditions of relatively homogeneous habitat conditions and capable of independent existence.

Phytocenosis is a conditional concept, since, firstly, a community of some plants cannot really exist without interaction with other components of biogeocenosis - zoocenosis, microbiocenosis, biotope, and secondly, according to the dominant concept of continuity of vegetation cover today, any isolation of isolated communities from it are artificial and serve only for practical purposes of studying vegetation at all levels.

The modern idea of phytocenosis as a conditional, really non-existent formation arose on the basis of an individualistic hypothesis developed by the Russian scientist L. G. Ramensky and the American G. Gleason. The essence of this hypothesis is that each species is specific in its relationship to the external environment and has an ecological amplitude that does not completely coincide with the amplitudes of other species (that is, each species is distributed “individually”). Each community produces species whose ecological amplitudes overlap under given environmental conditions. When any factor or group of factors changes, the abundance of some species gradually decreases and disappears, other species appear and increase in abundance, and in this way a transition is made from one type of plant communities to another. Due to the specificity (individuality) of the ecological amplitudes of species, these changes do not occur synchronously, and with a gradual change in the environment, the vegetation also changes gradually. Thus, plant communities do not form clearly isolated units, but are linked by transitional communities into a continuously varying system.

Depending on the specifics of the research in the concept of “biocenosis structure” V.V. Masing (1973) identifies three directions that he developed for phytocenoses.

2. Structure, as a synonym for structure (spatial, or morphostructure). In any phytocenosis, plants are characterized by a certain affinity to ecological niches and occupy a certain space. This also applies to other components of the biogeocenosis. Between the parts of the spatial division (tiers, sinusia, microgroups, etc.) you can quite easily and accurately draw boundaries; you can plot them on a plan, calculate the area, and then, for example, calculate the resources of useful plants or food resources of animals. Only on the basis of data on the morphostructure can one objectively determine the points at which certain experiments were performed. When describing and diagnosing communities, the spatial heterogeneity of cenoses is always studied.

All three aspects of the structure of biological systems are closely interrelated at the coenotic level: species composition, configuration and placement of structural elements in space are a condition for their functioning, i.e. vital activity and production of plant mass, and the latter, in turn, largely determines the morphology of cenoses. And all of these aspects reflect the environmental conditions in which the biogeocenosis is formed.

Morphological signs of phytocenosis

Plant communities, despite complex combinations of species, differ in structure. External characteristics that are used to evaluate the structure are called morphological. The main ones are: species composition, tiers, quantitative ratios of species in the phytocenosis. Let's look at each of these signs. The difference between each phytocenosis lies in its floristic composition, which is represented by a combination of certain plant species (trees, shrubs, grasses, mosses, etc.). To determine the species composition in the area, a description of botanical sites is made. The size of the site for grass phytocenoses is 1 m 2, for forest phytocenoses 1600 m 2 (80x20 m). Based on the descriptions, plant species are identified, their botanical identification is made, and the species richness of the phytocenosis as a whole is established.

Tiering in phytocenoses arises because plants have different attitudes to light, heat, moisture, and soil. In phytocenoses, plants of different heights are selected. Thanks to the layering, a larger number of species can settle on a unit area. Simply arranged phytocenoses consist of one tier (willows on sandy sediments); up to 5-9 tiers are found in forest phytocenoses (Fig. 61). The division of a phytocenosis into tiers represents a unique form of qualitative assessment of the ratio of species. As an example, we can cite the characteristics of the layering of a broad-leaved forest in the north of the Central Russian Upland. Typically, in oak forests, the first tier is formed by oak, the second tier by linden and maple, and the third by undergrowth of oak, linden, and aspen. The oak grove is characterized by a dense shrubby undergrowth (IV tier) of hazel, buckthorn, and honeysuckle. The grass cover of an oak forest can also be divided into tiers: fern (tier V), tall grasses (VI), oak forest broad grass (tier VII).

When characterizing a phytocenosis, it is important to establish the quantitative ratio or abundance of species. This characteristic is necessary to determine the predominant species (dominants) that make up the appearance of the phytocenosis. Currently, to determine abundance, the visual 4-point Drude scale is used, in which the following gradations are introduced: soc (sociales) - plants form the background; litter (copiosae) - abundantly represented; sp (sparsae) - found scatteredly; sol (solitarie) - rarely. Abundance can be more accurately determined by counting the number of species per unit area. The abundance indicator is complemented by the characteristic of the projective cover of species, when the area of projections of the terrestrial parts of the species is calculated and expressed as shares (%) of the total surface occupied by the phytocenosis. This characteristic is introduced because abundance does not provide a complete picture of the participation of a species in the composition of the phytocenosis.

Variability of phytocenoses

There are daily, seasonal and annual variability of plant communities.

Daily variability. As a result of fluctuations in the intensity of a number of environmental factors - especially light and temperature - the basic physiological parameters of plants change. Some results of plant reactions to changing factors are visible to the naked eye. This includes the daily rhythm of flowering and pollination, characteristic of most plant species, the phenomena of heliotropism (movements of vegetative and generative organs associated with the position of the sun in the sky), and the phenomena of photoperiodism (plant response to light intensity). The structure of aquatic communities is especially susceptible to daily variability.

Seasonal variability caused by changes in conditions during the year and is associated with the presence in the community of groups of plants that differ in the rhythm of seasonal development (they are found in almost all phytocenoses). Seasonal variability occurs regularly from year to year and can usually be predicted. The exception is sharply anomalous years.
Climate seasonality is a widespread situation in most regions of the globe; it manifests itself almost everywhere, with the exception of rainy areas. tropical forests. Because of this, widespread and climatically determined seasonal variability communities associated with the fall and melting of snow cover, the dynamics of river water in floodplains, semi-rest or dormancy during the hottest period in steppes, semi-deserts, savannas and deserts.

Seasonal variability is not only related to climate. There is cenotically determined seasonal variability associated with changes in the phytoenvironment within the community. It is widely known, for example, that there are two temporary synusias in the herbaceous layer of broad-leaved forests - a synusia of spring ephemeroids, which develops in the spring during the absence of leaves on the trees, and a synusia of shade-loving broad-grass, which appears with the leaves on the trees and the shading of the lower tiers. Finally, there is also anthropogenic seasonal variability associated with seasonal human activities (mowing plants in grass ecosystems, grazing by farm animals, etc.).

Interannual variability (fluctuation variability, fluctuations). The main reasons for the occurrence of fluctuations in phytocenoses include changes from year to year or over periods of years in various environmental conditions affecting the community. There are several types of fluctuations depending on the reasons that cause them: ecotopic fluctuations, caused by differences in meteo-, hydro- and other conditions of ecotopes from year to year, are widespread in meadow communities; anthropogenic fluctuations are caused by differences in the form and intensity of human impact on the phytocenosis. For example, in different years meadow community can be used either as hayfield or as pasture. The timing of haymaking changes from year to year, which creates different conditions for seeding of individual plant species. The species composition of grazing animals also significantly influences; zoogenic fluctuations caused by differences in the impact of herbivores and burrowing animals (especially digging rodents and insects).

Changes in phytocenoses over time

No phytocenosis exists forever; sooner or later it is replaced by another phytocenosis. The ability to change is one of the most important properties of plant communities.
Irreversible and directed, i.e., changes in vegetation cover that occur in a certain direction, manifested in the replacement of one phytocenosis by another, are called succession. It is their irreversibility and directionality that distinguishes them from fluctuations. Changes in phytocenoses have long been noticed and described, but the theory of these processes was most thoroughly worked out by the American scientists Henry Cowles and F. Clements. Clemente created a system of ideas about succession, starting with the emergence of phytocenoses up to the formation of stable, self-renewing plant communities - climaxes. The final stage of any succession - climax - can occupy an area indefinitely and exist for many hundreds of years practically unchanged. The main property of the climax community is a zero balance of matter and energy throughout the year.

There are two main types of successions - primary and secondary. Primary successions are quite rare in nature. They begin with the emergence of phytocenoses on bare mineral substrates, where previously there was no vegetation. Examples of such substrates are scree in the mountains, frozen recent lava flows, bottoms and sides of valleys after glacier retreat, exposed seabed, blown aeolian sands, etc. At the first stages of primary succession, autotrophic nitrogen fixers - both free-living and symbiotic - are of decisive importance associated blue-green algae (lichens). Lichens, in addition, provide chemical and biological weathering of rocks. These successions take several hundred years.

The phytocenosis is characterized by:

certain species composition;
structure, or otherwise, the features of the placement of components in space and time;
conditions of existence.

Species composition of phytocenosis. The established phytocenosis has its own physiognomy and certain characteristics. The most important feature phytocenosisstated floristic composition- a set of plant species included in a phytocenosis. The number of species included in the phytocenosis may vary. Phytocenoses consisting of one plant species are very rare in nature. Single-species phytocenoses formed by lower plants are usually designated by the word “colony”. In the case when one type of higher plant, a “thicket,” takes part in the formation of a phytocenosis, next to the word “thicket” is placed the name of the higher plant that is part of the phytocenosis (nettle thickets, raspberry thickets, etc.).

In nature, there are predominantly complex phytocenoses, which include not only higher plants, but also lower plants. The total number of species found in the phytocenosis over the entire occupied area depends on the conditions of existence (habitat conditions) of the phytocenosis and the history of its development. The size of the area occupied by the phytocenosis is also of considerable importance. The number of species registered on the registration site located within the described phytocenosis gives an idea of its species richness and species diversity.

Phytocenosis (from the Greek φυτóν - “plant” and κοινός - “general”) is a plant community that exists within the same biotope. Characterized by relative homogeneity of species composition, a certain structure and system of relationships between plants and each other external environment. Phytocenoses are the object of study of the science of phytocenology (geobotany).

Phytocenosis is part of the biocenosis along with zoocenosis and microbiocenosis. The biocenosis, in turn, in combination with the conditions of the abiotic environment (ecotope) forms a biogeocenosis. Phytocenosis is the central, leading element of biogeocenosis, as it transforms the primary ecotope into a biotope, creating a habitat for other organisms, and is also the first link in the cycle of substances and energy. The properties of soils, microclimate, the composition of the animal world, such characteristics of biogeocenosis as biomass, bioproductivity, etc., depend on vegetation. In turn, the elements of phytocenosis are cenopopulations of plants - collections of individuals of the same species within the boundaries of phytocenoses.

Tiering was first described by the Austrian scientist L. Kerner in 1863. spruce forest They were distinguished: woody layer, fern layer and moss layer. Then the Swedish scientist Gult identified in the forests northern Finland 7 tiers:

top woody,
lower woody,
undergrowth,
top grass,
medium herbal,
lower grass,
ground

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:

not all communities are vertically discrete;
it is unclear whether tiers are layers or elements “inserted” into each other;
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, there is no need to controversial issues, including where to include vines, epiphytes or undergrowth.

Horizontal structure

Most plant communities are characterized by heterogeneity horizontal folding. 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:

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).
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.).
Zoogenic mosaic caused by the influence of animals, both direct and indirect (mediated) - eating, trampling, laying excrement, and the activity of burrowing animals.
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.
Exogenous mosaic, caused by external abiotic environmental factors - the influence of wind, water, etc.

Mosaic- a special case of 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 plant 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 the 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 are communities related to each other 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.

Sinusia- these 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.

Stands out well in deciduous forests synusia of spring forest ephemeroids, “pseudo-meadow” synusia in deserts, or synusia of annuals in some types of vegetation.

1. The structure of phytocenoses should be understood as:

a) the diversity of species in them and the ratio of numbers and biomass of all populations included in them;

b) ratio environmental groups plants that develop over a long period of time in certain climatic, soil and landscape conditions;

c) spatial arrangement of plants (and their parts) in the plant community;

e) a + b + c.

2. The structure of phytocenoses is determined by:

a) the composition and quantitative ratio of the components of plant communities;

b) plant growth conditions;

c) exposure to animal components;

d) the form and intensity of human impact;

e) a + b + c;

f) all answers are correct.

3. The structure of the phytocenosis gives an idea of:

a) the volume of the environment used by the community;

b) the characteristics of the contact of the plants included in its composition with the environment;

c) efficiency and completeness of use by the plant community natural resources;

d) all answers are correct.

4. The structure of the phytocenosis depends on:

a) ecobiomorphic composition of the plant community;

b) the number and vital state of vascular plant individuals belonging to the main growth forms (trees, shrubs, shrubs, herbs);

c) the presence and quantitative participation of mosses and lichens, protists, algae and macromycetes;

d) height and density of aboveground shoots of community components;

d) all answers are correct

5. The most important features of the structure of the phytocenosis are:

a) the degree of closure of the vegetation cover and the features of the vertical distribution of the leaf surface;

b) the presence of sufficiently differentiated tiers or, conversely, their absence;

c) homogeneity or heterogeneity of horizontal division;

d). a + b + c.

6. The vertical structure of phytocenoses has two polar options, connected by smooth transitions:

a) tiering;

b) phytocenotic horizons

c) vertical continuum;

7. The main factor determining the vertical distribution of plants is:

a) the amount of light that determines the temperature and humidity conditions in the different levels above the soil surface in biogeocenosis;

b) strict competitive relationships between different plant species and their consorts;

c) edaphic, or soil-ground, habitat conditions;

d) terrain

8. A universal synthetic characteristic of the vertical structure of any phytocenosis (both with tiers and with a vertical continuum) is:

a) inversion of vertical belts;

b) aggregation index;

c) leaf surface index;

d) homogeneity index;

e) index of phytocenotic plasticity.

a) the ratio of the surface area of the leaves to the surface area of the soil on which they are located;

b) the ratio of the total area of leaves of a phytocenosis (or its tier) to the area of the territory it occupies, expressed in m 2 / m 2, or ha / ha;

c) the ratio of the total area of leaves of plants of different tiers;

d) the ratio of the surface area of leaves of different plant species.

10. The smallest value of the leaf surface index is typical for:

a) meadow phytocenoses;

b) open desert communities;

c) spruce forests;

d) mixed forests

11. Other things being equal, the leaf surface index in meadows increases:

a) from less acidic to more acidic soils;

b) from more acidic to less acidic soils;

c) from the beginning of the growing season to the period of culmination of grass development;

d) after each mowing and grass removal;

e) with increasing lighting intensity and introducing full mineral fertilizer(NPK)

f) b + c + d + d;

g) b + c + d;

h) a + c + d;

12. The formation of the underground part of phytocenoses is characterized by a decrease in the mass of plant organs from top to bottom. This has been established for such plant communities as:

a) meadow;

b) steppe;

c) deserted;

d) forest;

d) all answers are correct.

13. The mass of underground organs is usually several times (sometimes 10 or more) greater than the mass of above-ground organs in such communities as:

a) meadow;

b) subshrubs;

c) tundra;

d) desert;

d) all answers are correct.

14. To the main price elements of phytocenoses according to Kh.Kh. Track (1970) include:

b) phytocenotic horizons;

c) price cells;

d) microgroups.

15. An element of the vertical structure of phytocenoses, manifested in the case when the community is formed by life forms of plants contrasting in height, is:

a) price element;

b) sinusia;

d) cenotype;

e) phytocenotic horizon.

16. The tiers differ:

a) environmental conditions in the horizons to which the aboveground organs of the plants that form them are confined;

b) features of light and temperature conditions;

c) air humidity;

d). a + b + c + d.

17. There are several types of tiers (according to T.A. Rabotnov):

a) stable over the seasons and over the years (for example, tiers of evergreen trees, shrubs, shrubs, mosses, lichens);

b) existing all year round, but changing sharply from the growing season to the non-growing season (tiers formed by deciduous trees, shrubs, shrubs);

c) formed by herbs;

d) ephemeral, existing for a short time, formed by herbs (ephemera, ephemeroids), sometimes mosses;

e) are formed only in certain years, for example, a layer of annual grasses in those deserts where sufficient precipitation falls only in some years;

f) re-forming during the growing season due to the alienation of above-ground organs as a result of mowing or grazing;

and). a + b + c + d.

18. Tiered arrangement of plants:

a) allows species of different ecological qualities to coexist in a community;

b) makes the habitat more ecologically capacious;

c) creates a large number of ecological niches, especially in relation to the light regime;

d) reduces competition and ensures community sustainability;

d) all answers are correct.

19. In the row single-tiered – two-tiered – low-tiered – multi-tiered – imperfect-tiered (vertical-continuous) communities the following is observed:

a) increase in floristic richness;

b) decrease in floristic richness;

c) a clear correlation between the number of tiers and the number of species that make up the phytocenosis;

d) absence of a certain pattern.

20. In temperate zone forests, the following tiers are usually distinguished:

a) the first (upper) tier is formed by trees of the first size (pedunculate oak, heart-shaped linden, smooth elm, etc.)

b) second - trees of the second size (rowan, apple, pear, bird cherry, etc.);

c) the third tier is the undergrowth formed by shrubs (common hazel, brittle buckthorn, etc.)

d) the fourth tier consists of tall grasses (nettle, common gooseberry) and shrubs (bilberry);

e) the fifth tier is made of low grasses;

f) in the sixth tier - mosses and lichens;

g) all answers are correct.

21. Consistent use of the concept of tiering has a number of theoretical difficulties due to the fact that:

a) not all phytocenoses are vertically discrete;

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

c) it is unclear where to include undergrowth, vines, and epiphytes;

d) all answers are correct.

22. Division into tiers is absent in such types of phytocenoses as:

a) most herbal;

b) tropical rain forests;

c) certain types of broad-leaved forests;

d) a + b + c.

23. The absence (or weak expression) of layers in herbaceous communities can be explained by:

a) the presence of only one life form;

b) small height of plants;

c) the presence of predominantly perennial grasses;

d) approximately the same illumination of all plant individuals, regardless of their height and environmental characteristics.

24. There is no underground layering:

a) in spruce forests;

b) in meadow phytocenoses;

c) on salt marshes and solonetzes;

d) in steppe and desert communities;

e) a + b + d;

g) all answers are correct.

25. Phytocenotic horizon is:

a) a vertically isolated and vertically undivided structural part of the biogeocenosis;

b) the vertical part of the plant community, characterized by a certain floristic composition and a certain composition of the organs of these plants;

c) artificial morphological division of the vegetation cover, in which (in contrast to tiered division 26. In forests of the temperate zone, the following phytocenotic horizons are usually distinguished, formed:

a) tree crowns;

b) under-crown part of trunks tall trees, as well as trees of smaller height, shrubs and corresponding consorts (for example, plants) are, as it were, cut vertically, forming horizontal layers;

d) all answers are correct.

lichens);

c) shrubs or herbs, which, in addition to herbs and shrubs, includes the lower parts of the trunks of trees and shrubs with their characteristic epiphytes;

d) mosses, lichens, creeping plants, including the lower parts of taller plants and their shoots;

d) all answers are correct.

27. When identifying phytocenotic horizons, such controversial issues that arise when delineating tiers, such as:

a) how many tiers does this or that phytocenosis include;

b) at what closeness of the above-ground organs of the corresponding plant species is the layer considered expressed or not expressed;

c) where to include vines, epiphytes, undergrowth;

d) all answers are correct.

28. Lianas and epiphytes are part of:

a) upper horizons;

b) lower horizons;

c) those horizons to which the parts of trees and shrubs that serve as their support belong;

29. Each phytocenotic horizon is characterized by:

a) a certain floristic composition;

b) the composition of the organs of these plants;

c) the degree to which the space is filled with these organs;

d) all answers are correct.

30. An area of vegetation cover within which boundaries cannot be drawn according to given characteristics and thresholds adopted to determine the boundary is called:

a) parcel;

b) price cell;

c) microgrouping;

d) tsenokvantom;

d) price element.

a) one life form;

b) united by individual topical and trophic competitive relationships;

c) one type;

d) different tiers.

32. The morphological expression of the price cell of woody vegetation is determined by:

a) age of the tree stand;

b) group placement of trees and forest stands;

c) the height of the tree stand and plants forming the undergrowth;

d) the vitality of plants.

33. The structural part of a phytocenosis, limited in space or time (occupying a certain ecological niche) and differing from other similar parts in morphological, floristic, ecological and phytocenotic terms, is called:

a) coenopopulation;

b) cenotype;

c) sinusia;

d) tsenokvantom.

34. The following can be considered as synusia:

a) each well-defined layer of forest phytocenoses;

b) a set of epiphytes, lianas, epiphytic lichens;

c) spring forest ephemeroids;

d) groups of annuals that exist in deserts only in years with heavy precipitation;

f) all answers are correct.

35. Among temporary sinuses there are:

a) seasonal;

b) daily allowance;

c) fluctuation;

d) demutational;

e) a + c + d;

e) a + b + c.

36. The most important signs of sinusia are the following:

a) synusia is formed by plants of one or more closely related life forms;

b) plants in the synusia are close together, closed in underground or aboveground parts;

c) ecological similarity of plants belonging to the same synusia;

d) morphological isolation, spatial expression;

e) certain interactions between plants, their influence on the environment and, as a consequence, the creation of their own eco-environment;

f) relative autonomy, expressed in the fact that synusias of the same type can exist with synusias of other types in different combinations;

g) a + c + d + f;

h) all answers are correct.

37. Synusia are:

a) a forest stand formed by spruce, pine or any other species;

b) cover of blueberry or heather;

c) a patch of hairy sedge in an oak forest;

d) mixed stand of spruce and fir;

e) a tree stand formed by a mixture of oak, maple, and ash;

f) cover of ephemeroids in an oak forest;

g) lichen carpet of bushy forms in a pine forest;

h) a + b + d + g;

i) all answers are correct.

38. Sinusia are characterized by the following functional features:

a) the plants included in the synusia have similarities in needs, cenotypic kinship, similarity in transforming the environment in a way favorable for themselves and their partners;

b) in synusia there is a single coenotic process;

c) coenotic and ecological selections take place in synusia;

d) all answers are correct.

39. An example of fluctuation sinusia is:

a) a group of spring ephemeroids, well limited in time from the synusias of grasses of the summer growing season, which differ from the spring ones in their species composition, structure, ecologically and cenotypically.

b) thickets of fireweed in burnt areas and clearings, existing for a short time;

c) a group of annual grasses that appear in some deserts in the years with big amount atmospheric precipitation;

d) synusia of creeping buttercup in flooded meadows during prolonged stagnation of spring floods.

40. Sinusial analysis of phytocenoses comes down to:

a) establishing the synusia that makes up the phytocenosis;

b) study of their species composition and structure;

c) studying the relationship between them and the environment;

e) a + b + c.

41. Sinusial analysis of plant communities helps to determine:

A) environmental conditions habitat;

b) complete use of environmental resources by the phytocenosis;

c) the ecological niche occupied by each specific synusia;

d) a + b + c.

42. Most plant communities are characterized by heterogeneity of horizontal composition; this phenomenon is called:

a) intermittency;

b) mosaic;

c) continuum;

d) emergence.

43. Within phytocenoses, special structural formations can be distinguished, called:

a) microgroups, or microphytocenoses;

b) price elements;

c) price quants;

d) price cells;

e) a + c + d;

f) all answers are correct.

44. The horizontal division of phytocenoses - mosaic - is expressed by the presence in the biocenosis of various microgroups that differ:

a) species composition;

b) quantitative ratio different types;

c) closeness;

d) productivity and other characteristics and properties;

d) all answers are correct.

45. The following variants of mosaic phytocenoses are distinguished (Rabotnov, 1984; Mirkin, 1985):

A) regeneration mosaics– heterogeneity of phytocenosis associated with the renewal process;

b) clone mosaics– heterogeneity of phytocenosis associated with vegetative propagation of plants;

V) phytoenvironmental mosaics– heterogeneity of the phytocenosis associated with changes in the environment by one of the species and the response of other species to this change;

G) allelopathic mosaics caused by the release of strong-smelling aromatic substances by some plant species;

d) zoogenic mosaics are formed as a result of exposure to animals;

f) a + b + c + d + e.

46. The uneven distribution of plant species within the plant community and the associated patchiness is due to a number of reasons. Based on their origin, the following types of mosaic are distinguished:

A) phytogenic caused by competition, changes in the phytoenvironment or characteristics of plant life forms;

b) edaphotopic, associated with the heterogeneity of the edaphotope (irregularities in the microrelief, different drainage, soil heterogeneity, etc.);

V) zoogenic caused by direct or indirect influence of animals (trampling, eating, laying excrement);

G) anthropogenic, the reason for which is human economic activity (grazing farm animals, selective cutting of trees in the forest, fire pits, etc.)

d) exogenous, caused by the action of abiotic environmental factors - the influence of wind, water, etc.

f) a + b + d;

g) all answers are correct.

47. Mosaicism in the forest is least pronounced where:

a) the tree layer is formed by one species;

b) the tree layer is formed by species that are similar in their influence on the environment;

c) the tree layer contains different ecobiomorphs (coniferous and soft-leaved tree species);

d) there are no and poorly developed shrubs;

e) growing conditions for most species are unfavorable;

f) a + c + d;

g) a + b + d + e;

h) all answers are correct.

48. Mosaic pattern is most pronounced:

a) in floodplain meadows;

b) in mixed coniferous-deciduous forests;

c) in raised bogs;

d) in coniferous forests.

49. The reasons for phytogenic mosaic in coniferous-deciduous forests, represented mainly by spruce and linden, may be the following:

a) lower illumination and temperature under the spruce than under the linden;

b) 2.0 – 2.5 times less precipitation in the form of rain penetrates under the crowns of spruce trees than under the crowns of deciduous trees;

c) rainwater flowing from tree crowns has a more acidic reaction than water flowing under the linden tree;

d) under the spruce a soil is formed with a poorly developed humus horizon and a well-defined podzolic horizon;

e) a + b + d;

e). a + b + c + d.

50. Characteristic features of the mosaic nature of many types of phytocenosis are:

a) stability in time and space;

b) dynamism;

c) replacement of some microgroups by others over time;

d) change due to passage life cycle plants;

e) b + c + d.

51. The English scientist Watt (1947) distinguished the following phases of age-related variability of plants and, accordingly, variability of microgroups:

a) pioneer;

b) invasive;

c) construction phase;

d) maturity;

e) degeneration;

f) a + c + d + d;

g) a + b + d + e.

52. The following types of horizontal composition of phytocenoses are distinguished (according to A. P. Shennikov):

a) separate;

b) separate-group;

c) closed group;

d) diffuse;

e) mosaic;

c) a + b + c + d;

g) a + b + c + d + e.

53. The mosaic phytocenosis, with all the diversity of composition and division into fragments, is united:

a) dominance of one of the tiers;

b) the absence of dominance of any tier;

c) small sizes of mosaic elements that mutually influence each other;

d) significant sizes of mosaic elements.

54. In contrast to mosaicism, which characterizes intracenotic horizontal heterogeneity, complexity is the horizontal heterogeneity of vegetation cover at the supraphytocenotic level. The complex consists not of fragments, but of different phytocenoses, which:

a) occupy large areas;

b) are highly dependent on each other;

c) depend less on each other;

d) not connected by a common tier;

e) alternate mosaically in space;

f) a + c + d + d;

g) a + b + d + e.

55. The transition zone between phytocenoses (contact phytocenosis) is called:

a) ecoid;

b) ecocline;

c) ecotone;

d) ecotope.

56. Ecotone can be:

a) narrow or wide;

b) sharp or absent;

c) diffuse or bordered;

d) mosaic-island;

f) all answers are correct.

57. The absence of a pronounced transition strip between phytocenoses is most often due to:

a) a sharp change in growing conditions (for example, on a steep slope, in a clearly defined depression, etc.);

b) human impact (for example, a meadow clearing in the middle of a forest that appeared at the site of deforestation);

c) the environment-forming influence of dominant species in one of the phytocenoses bordering each other (for example, spruce, sphagnum mosses, etc.);

e) a + b + c.

CHAPTER 5

Dynamics of phytocenoses.

1. The dynamics of phytocenoses and vegetation in general (syndynamics) mean:

a) reversible changes in plant communities within a day, a year and from year to year;

b) changes in phytocenoses with increasing age of edificator individuals;

c) various options for gradual directed changes that can be caused by both internal and external factors and, as a rule, are irreversible;

d) long-term cyclical changes caused, for example, by regularly recurring forest fires;

e) a + b + d;

f) all answers are correct.

2. The main forms of vegetation dynamics are:

a) disturbances of phytocenoses;

b) succession of phytocenoses;

c) evolution of phytocenoses;

d) a + b + c.

3. The following types of variability of phytocenoses are distinguished:

a) daily allowance;

b) seasonal;

c) multi-annual;

d) age;

d) all answers are correct

4. Unlike shifts, the variability of phytocenoses is characterized by the following features:

a) variability of floristic composition;

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

c) the observed changes are reversible;

d) irreversibility of changes;

e) the observed changes are undirected;

f) a + g + d;

g) b + c + d.

5. Daily variability of phytocenoses appears only during the period:

a) growing season;

b) the beginning of flowering;

c) flowering;

d) formation of seeds and fruits;

d) fruit ripening

6. During the day, such vital functions of plants change as:

a) photosynthesis;

b) intensity of absorption of water and mineral elements;

c) transpiration;

d) release of metabolites, which, in turn, leads to fluctuations in the composition of the air within phytocenoses (CO 2 content, specific secretions, etc.);

d) all answers are correct.

7. Seasonal variability of phytocenoses is due to changes throughout the year:

a) light and temperature conditions;

b) general climate;

c) hydrological regime;

d) phytoclimate;

e) all answers are correct

8. The stages of phenological development of phytocenoses differ from one another:

a) characteristics of the biotope (phytoenvironment);

b) the intensity of plant growth and reproduction;

c) the degree and methods of influence of some components on others;

d) structural features and floristic composition;

e) aspect (appearance) and economic use;

g) all answers are correct

9. Phenological spectra give an idea of:

a) floristic composition of the studied phytocenosis;

b) changes in the participation of individual species in phytocenoses during the season or year;

c) the composition of life forms;

d) the beginning and end of the growing season, as well as the duration of the growing season;

e) timing of the onset and duration of individual phases of the growing season;

f) changes in the rhythm of seasonal vegetation depending on the characteristics of the environment in the studied cenoses;

g) all answers are correct.

10. Changes that occur in phytocenoses by year or period of year, associated with unequal meteorological and hydrological conditions of individual years, are called:

a) succession;

b) transformation;

c) fluctuation;

d) demutation.

11. According to the causes of occurrence, the following types of fluctuations are distinguished:

A) ecotopic, associated with differences in meteo-, hydro- and other conditions of ecotopes from year to year;

b) anthropogenic, caused by differences in the form and intensity of human impact on the phytocenosis;

V) zoogenic, caused by differences in the effects of herbivores and burrowing animals;

G) phytocyclic, associated with the characteristics of the life cycle of certain plant species and (or) with their uneven seed or vegetative propagation over the years;

f) all answers are correct.

12. Ecotopic fluctuations are the least pronounced:

a) in the forests;

b) in the meadows;

c) in the steppes;

d) in sphagnum bogs.

13. The most significant fluctuation changes are observed in adult individuals of herbaceous plants, which are manifested:

a) in the number and power of shoots;

b) in their vitality;

c) in the ratio of individuals in the generative and vegetative state;

d) a + b + c;

14. According to the degree of severity, fluctuations are divided into several types:

a) hidden;

b) oscillatory (oscillations);

c) cyclical;

d) digression-demutation;

e) all answers are correct

15. Hidden fluctuations occur:

a) in monodominant grass cenoses;

b) in phytocenoses formed by species with perennial above-ground organs (woody plants, mosses, lichens);

c) in complex floristically rich multi-layered forest communities

16. Oscillations are described for:

b) coniferous forests;

c) mixed forests;

17. Examples of oscillation can be:

a) change of dominants in some types of meadows in wet and dry years;

b) seasonal changes in the floristic and ecobiomorphic composition of phytocenoses;

c) fluctuations with alternating changes over the years at the level of subdominants;

d) seasonal dynamics of productivity

18. Digression-demutation fluctuations are characterized by:

a) a change in dominants and subdominants in floodplain meadows as a result of a sharp deviation from the average meteorological and hydrological conditions for these biogeocenoses;

b) changes in the ecobiomorphic composition of phytocenoses;

c) severe disturbance of phytocenoses with their subsequent demutation - a return to a state close to the original one, as soon as the reason that caused the change ceased to operate;

d) seasonal changes in the quantitative ratio of components of phytocenoses

19. Factors causing digression of phytocenoses may be:

a) severe prolonged drought;

b) prolonged stagnation of water on the soil surface in spring;

c) the formation of a thick ice crust;

d) severe winter with little snow;

e) mass reproduction of phytophages;

f) all answers are correct.

20. The most significant disturbances of phytocenoses occur if the adverse effects of meteorological and hydrological conditions, as well as zoo components:

a) is especially pronounced during the growing season of plants;

b) lasts no more than two years (seasons), as a result of which there is no strong oppression or mass extinction of dominant species;

c) continues for several years or several seasons in a row, which leads to mass death or severe suppression of the main components of phytocenoses;

d) lead to disruption of the vegetative propagation of plants in the lower tiers.

21. The duration of the demutation period is determined:

a) the intensity of the community disturbance;

b) the degree of preservation of plants that were dominant before the disturbance;

c) growing conditions during the demutation period;

d) all answers are correct.

22. Examples of digression-demutation fluctuations can be:

a) the replacement of cereal grass stands with creeping grasses, which occurs under the influence of spring stagnation of hollow waters, with the subsequent return of the predominance of cereals;

b) transformation into creeping cenoses with a predominance of various types of cereals;

c) the ability of individuals of many plant species, under the influence of drought, to enter a dormant state, and after the end of the drought, the ability to quickly return phytocenoses to their original state;

d) all answers are correct.

23. Practical significance studying fluctuations of phytocenoses of forage lands (meadow, steppe, etc.), aimed at their effective use and improvement, is determined by the fact that, year by year:

a) their productivity and the quality of the feed obtained from them fluctuates;

b) the timing and even the possibility or feasibility of using forage lands change;

c) the effectiveness of methods for improving forage areas changes

(irrigation, fertilization, overseeding, etc.);

d) all answers are correct.

24. Primary productivity of biogeocenoses is the creation of organic matter:

a) autotrophic organisms (photosynthetic green plants);

b) heterotrophs (bacteria, fungi, animals);

c) all living organisms of the ecosystem

25. When studying biological products, it is necessary to determine the mass:

a) only living plants;

b) only living plants and litter;

c) living plants, litter, dead trunks of trees and shrubs - waste, as well as dead underground organs;

d) all answers are correct.

26. Biomass is:

a) the amount of living matter expressed in mass per unit area or volume of habitat (g/m2, kg/ha, g/m3, etc.);

b) the increase in primary production per unit of space per unit of time (for example, g/m 2 per day);

c) the total mass of individuals of a species, group of species or community of organisms, expressed in units of mass of dry or wet matter per unit area or volume of habitat (kg/ha, g/m2, g/m3)

27. The biomass of living matter in terrestrial ecosystems is represented by:

a) plants, animals, fungi and bacteria in approximately equal proportions;

b) mainly animals and microorganisms;

c) more than 95% by plants.

28. The highest functional activity, i.e. the rate of increase in biomass per unit time, is characteristic of:

a) marine phytoplankton;

b) a complex of plants of rivers and lakes;

c) vegetation of meadows, steppes, arable land;

d) woody vegetation.

29. Gross primary production (gross production) is the amount of organic matter:

a) retained in plants after part of it is used for respiration;

b) created by plants during the process of photosynthesis;

c) created by all living organisms that are part of a particular biocenosis.

30. Vegetation production is determined by:

a) temperature conditions and humidity;

b) provision of plants with mineral nutrition elements;

c) the absence of limiting factors, for example, salinity;

d) all answers are correct

31. Succession is called:

a) repeated variability of phytocenoses over years or periods of years;

b) seasonal variability of phytocenoses, caused by sharp fluctuations in temperature during the growing season;

c) irreversible and directional, i.e., a change in vegetation cover occurring in a certain direction, manifested in the replacement of some phytocenoses by others

32. The main difference between the evolution of phytocenoses and their succession is:

a) during evolution, the composition and structure of phytocenoses remain practically unchanged (the composition may even be simplified), and as a result of succession, new phytocenoses always arise;

b) in the course of evolution, new phytocenoses are formed, and in the case of succession, phytocenoses do not arise, but combinations of species that already existed in the area are formed;

c) succession is always a “repetition of the past”, and in the course of evolution new, previously absent combinations of plant populations arise.

33. The main differences between succession and fluctuations are:

a) irreversibility of changes;

b) continuity of succession;

c) direction of changes;

d) all answers are correct.

34. Based on their origin, there are two main types of successions:

a) permanent;

b) temporary;

c) primary;

d) fluctuation;

d) secondary.

35. Primary successions begin with the emergence of phytocenoses on:

a) rocks;

c) sediments of water flows;

d) cooled lava after a volcanic eruption;

e) clearings in the forest;

f) a + c + d;

g) all answers are correct.

36. The following processes occurring in the case of primary succession are distinguished:

a) formation of a substrate;

b) migration of plants, their establishment and aggregation;

c) plant interaction;

d) changes in the environment by plants;

e) change of phytocenoses;

f) a + b + d + d;

g) all answers are correct.

37. Migration (distribution) of plants is carried out by transferring from one place to another:

a) seeds, spores and other germs;

b) whole plants;

c) vegetative organs of plants;

d) all answers are correct.

38. The survival of plants arising from rudiments brought from outside is possible if:

a) they find themselves in favorable ecotopic conditions;

b) seedlings develop with a homeostasis composition of consorts;

c) they have the ability to reproduce by seeds;

d) all answers are correct.

39. The period from the initial phases of succession to the achievement of a stable state of phytocenoses varies depending on:

a) climate;

b) initial substrate;

c) the possibility of diasporas entering;

e) a + b + c.

40. Primary successions proceed faster:

a) in a warm, humid climate;

b) in cold, dry climatic regions;

c) on rocky ground;

d) on fine-grained substrates

41. Available data on the rate of primary succession indicate that (check the correct answer):

a) in the Alps they take 100 years, in Japan - in 700 years, in the Arctic - more than 7000 years, on the poor quartz sands of the dunes along the coast of Lake Michigan (USA) - in about 5000 years;

b) in the Alps - for 100 years, in the USA (oak forests on the dunes of the Michigan coast) - for 700 years, in Japan - for 1000 years, in the Arctic - for more than 5000 years;

c) in the Alps - for 100 years, in Japan - for 700 years, in the USA (on the dunes of the coast of Michigan) - for 1000 years, in the Arctic - for more than 5000 years;

42. Secondary successions differ significantly from primary ones in that they begin in the conditions of already formed soil, which contains:

a) numerous microorganisms (bacteria, protists, fungi);

b) spores and seeds of plants, their resting underground organs;

c) soil mesofauna;

d) mineral and organic substances;

d) all answers are correct.

43. Secondary successions:

a) occur much faster (about 5-10 times) than the primary ones;

b) pass much more slowly than the primary ones;

c) in terms of speed of origin, they practically do not differ from the primary ones.

44. For reasons of change in biogeocenoses, the following types of successions are distinguished:

a) syngenetic (syngenesis);

b) autochthonous;

c) endoecogenetic (autogenous, or endodynamic);

d) exoecogenetic (allogeneic, or exodynamic);

g) all answers are correct

45. Syngenesis is a process:

a) colonization by plants of places not yet covered with vegetation;

b) the colonization of places by plants after the destruction of previously existing vegetation;

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.

The plant community is an open biological system, representing 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 the environment, which is carried out as a result of the vital activity of their autotrophic components fixation solar energy and - with the participation of other organisms - its transformation and biological cycle of substances, as well as the fixation of atmospheric nitrogen and having a certain composition and 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

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.

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.

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.

Mosaicity is a special case of 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.

There are complexes and combinations of communities. Complexes are communities related to each other 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 the quantitative relationships between species, to 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, therefore, different environment-forming properties of the 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). And for different types 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 characteristics of their 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 of the 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 kind of habitus certain groups 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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