The simplest methods for geobotanical description of phytocenoses. Basics of phytocenology How to compare phytocenoses

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) the ratio of ecological groups of plants that develops 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 of natural resources by the plant community;

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 at different levels above the soil surface in the 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;

V) spruce forests;

G) 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 light intensity and applying complete 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 the woods temperate zone 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 nettle) 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) the under-crown part of the trunks of tall trees, as well as trees of shorter 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 tier 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) studying them species composition and buildings;

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 of the 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 economic activity human (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;

e) 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 The mosaics 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 the passage of the plant life cycle;

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) change in participation in phytocenoses individual species throughout 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;

G) seasonal changes in the quantitative ratio of the 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 hydration;

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 slower 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.

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.

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.

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.

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). 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 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 cenopopulations 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 resource plant populations, issues effective fight with populations of harmful 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” the mechanisms of 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 adverse 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.

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:

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

1. Migration- introduction of diasporas
2. Ecesis- consolidation of the first settlers
3. Aggregation- formation of groups of offspring around mother plants
4. Invasion- mixing of coenopopulations
5. Competition- development of competitive relations due to a sharp increase in crowd density
6. 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:

1. 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.
2. 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.
3. 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, thermal, water regime y, etc.)
• edaphic (particle-size 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 released both aboveground 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

The sum of secretions of various plants in a phytocenosis is 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, 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.

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 cenotic level: the species composition, configuration and placement of structural elements in space are a condition for their functioning, that is, life 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.

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 older temperate forests 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 the 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 - pleurocium moss) or the Latin generic and species names of the dominants (Pinus sylvestris + Picea abies - Vaccinium vitis-idaea + Vaccinium myrtillus - Pleurozium schreberi) with the addition of suffixes to the base

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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 the 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 Linden heart-shaped armor. 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, the 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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Each phytocenosis, including forest, is characterized by a set of characteristics that give a clear idea of ​​its structure and structure. The main features of a phytocenosis are species composition, layering, abundance, quantitative and qualitative relationships between species, occurrence, projective cover and vitality. There are quantitative indicators to assess these characteristics.
When describing phytocenoses, a test area in the shape of a rectangle or square is allocated. The size of the trial plot should fully reflect all the features of the phytocenosis. It has been established that for forest communities its minimum size is 400-500 m2.
In geobotany, certain rules have been adopted for describing phytocenoses. They boil down to the following: all descriptions are numbered, the date of work, the author, the size of the trial plot, the geographical location of the trial plot, the position on the relief are indicated, and the microrelief, moisture conditions, ground (dead) cover, soil type with a description of the soil section and analysis are also characterized soil samples.
The main component of the forest phytocenosis is the tree stand, which includes certain tree species. On the registration (test) area, a complete count of the trunks of each species is carried out (only mature trees are taken into account). Mature trees of the first size form the first tier, and mature trees of the second size form the second. Teenagers are especially taken into account. Within each tier, a numerical estimate of the ratio of trees is given different breeds in a phytocenosis or in fractions of a unit, or for 10 trunks, i.e., how many trunks out of 10 are for each species. For example, the recording form D6B4 means that there are 6 trunks per oak, and 4 trunks per elm. The diameter of the trunks is measured with a taxator fork at chest height (1.3 m) or with a tailor's meter, at the same height the circumference of the trunk is determined and the resulting value is divided by 3.14. All trees in the trial plot are measured.
The height of the tree is determined using an eclimeter. To do this, depending on the height of the tree, measure 10, 20 or 30 m from it and from the found point sight the top and find the angle. The height of the tree is determined based on the angle and distance from the trunk using tables.
When characterizing a tree stand, the diameter of the crowns is taken into account as measured by a tape measure stretched along the ground from the base of the trunk to the edge of the crown projection in the direction from north to south and from west to east. The average value is derived from the four measurements. At the same time, the height of crown attachment is calculated by eye or instrumentally as the distance from the base of the trunk to the place of attachment of the lower branches of the crown.
In the taxation characteristics of a forest stand, the sum of cross-sectional areas per hectare is important. This indicator is assessed with a Bitterlich full-meter (circular sampling method). A full gauge is a ruler 0.5-1.0 m long with attachments at the end in the form of a fork with a solution of the last 1.0-2.0 cm, respectively. Through the slot of the fork, the diameter of the tree is visible; being at one point and turning 360°, the observer sights all the trees. If, when sighting, the diameter of the tree is greater than the diameter of the full diameter, then the tree is taken into account; if it is equal to it, then every second tree is taken into account. When one tree is covered by another, you need to move 0.5-2 m away in order to clearly see the tree being assessed, and then return to its original place. The number of trees taken into account is noted separately for each species. Sum of cross-sectional areas in square meters per 1 hectare is equal to the number of trees recorded. For example, 15 trees are taken into account, therefore, the cross-sectional area is 15 m2/ha. The sum of cross-sectional areas can be determined by the predominant diameter of trunks and their number in the sample plot for each tree species.
The state of seedlings and undergrowth, their number per unit area is the most important indicator of phytocenosis.
The regeneration of the forest stand is assessed on five 2x2 m plots, located in an envelope in the corners and in the center of the trial plot. For each breed, the number of specimens of undergrowth and seedlings of different ages is determined separately. Then the average is calculated. Undergrowth with a height of more than 1.5 m is taken into account throughout the entire sample area.
Accounting for undergrowth involves assessing the species composition, crown density, and the nature of distribution over the sample plot. The crown density of the undergrowth is determined, as for the main tree stand, in fractions of one or as a percentage.
The total projective cover of soil with grass and shrubs is determined as the percentage of the area occupied by projections of above-ground parts of plants - grasses and shrubs. Characterized by the greatest species saturation mixed forests, the main components of which are light coniferous and small-leaved tree species. In such forest communities, thanks to the see-through crowns, favorable conditions are created for the development of shrub and herbaceous vegetation. The aspect of a phytocenosis consists of the most striking features of the structure of a phytocenosis: the abundance of a species, its density, color, dominance in tiers.
In phytocenoses there is often no homogeneity; there is a mosaic pattern in the form of individual spots and clumps. This applies to both the arboreal and terrestrial herbaceous layers. This phenomenon is sinusia- determined by microrelief conditions, lighting, soil type, hydrological conditions. When describing a phytocenosis, each synusia is assessed by size, configuration, and order of placement on the terrain.
The species composition of plants is described in the form of Russian and Latin names; ecological and biological groups are also distinguished here - one-, two-, perennials, forest, forest-meadow, steppe species, weeds and others, as well as shrubs, subshrubs, herbs.
Abundance is an estimate of the number of wasp species in a community. In geobotany, they usually use the scale of the Danish botanist Dru-de, based on an eye assessment of the abundance of each species in the phytocenosis. A more accurate, but more labor-intensive method for assessing abundance is the method of counting individuals of a species per unit area. An estimate of abundance can also be given by the weight method.
The Drude scale includes six levels of abundance:
Socialis (Soc) - plants close together with above-ground parts, forming a general background, background plants;
Copiosus3 (Cop3) - plants are found very abundantly;
Copiosus2 (Cop2) - quite a lot of plants, scattered;
Copiosus1 (Cop1) - plants are found occasionally;
Sparsus (Sp) - few plants;
Solitarius (Sol) - solitary plants, there are very few of them.
The Drude scale can be combined with the projective coverage scale. This indicator of species abundance provides a more objective assessment of the importance of the species in the plant community.
The method for recalculating the abundance of a species is based on the allocation of census plots, the size of which depends on the nature of the forest phytocenosis. The trees in the phytocenosis are counted on an area of ​​1,000 m2 (10x100), 1,600 m2 (20x80) or 2,000 m2 (20x100), shrubs and herbaceous vegetation are analyzed on areas measuring 100 m2.
The weight method of accounting for the abundance of species is mainly used in geobotanical studies in herbaceous phytocenoses, but it can also be used in forest phytocenoses for the herbaceous layer. In this case, 20 plots of 0.1 m2 each are allocated on the trial plots and the plants are cut at soil level, then the cut plants are laid out by type and weighed. After completing the work, the average indicators of participation of each species in the formation of the ground mass of the phytocenosis are calculated for all recording sites.
Projective coverage- an indicator characterizing the magnitude of the horizontal projection of the above-ground parts of all plants of a given species found on the trial plot, in relation to the size of the trial plot. Express projective coverage as a percentage. This indicator is highly variable both by year and by season.
An important characteristic of species in phytocenoses is their vitality, which is assessed by the degree of development or suppression of the species in the phytocenosis. The most objective assessment of the vitality of a species can be obtained during flowering or fruiting of a tree species. There is a vitality scale for assessment: For - “good vitality” - the species blooms steadily, bears fruit, and produces normal annual growth; 36 - the same, but the species does not reach normal growth sizes; 2 - “satisfactory vitality” - the vegetative part of the species is well developed, but it does not bear fruit; 1 - “poor vitality” - the species does not bloom, does not bear fruit, and vegetates poorly.
When describing phytocenoses, the phenophases of plants must be noted, which is important for characterizing the seasonal rhythm of phytocenoses as a whole.
In forest phytocenoses, the following stages of seasonal development, or phenological phases, are usually distinguished: vegetation, budding, flowering, fruiting, vegetation after fruiting, dying, dormancy. NOT. Bulygin evaluates the phenological development of woody plants, dividing them into two stages of ontogenesis: the first is juvenile, the second is virginal and subsequent ones. The second stage, in turn, is divided into observations of generative and generative-growth shoots.
Forest phytocenoses often contain lichens and mosses, such as component ground cover. General characteristics of these groups of plants are given, their abundance and projective cover are indicated. Here, without detailed characteristics, the presence of algae and fungi is noted.
In descriptions of forest phytocenoses, epiphytic vegetation on trunks, stones, and dead wood is also noted, and the size and configuration of the phytocenosis, its environment, transitions to adjacent phytocenoses, and the place of the phytocenosis in the ecological series are also assessed.