Phytocenosis. Composition of phytocenosis: participation of species and its assessment (abundance, cover, phytomass). Vertical and horizontal composition of phytocenosis. Morphology of phytocenosis Phytocenosis examples

Geobotany

Topic 3

PHYTOCENOSIS

Lecture1

Phytocenosis and its features

Phytocenology

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

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

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

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

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

Phytocenosis and its features

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

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

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

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

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

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

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

This task is based on the manualA.S. Bogolyubov and A.B. Pankova.

Such work is based on methods of description and observation, they are not very difficult, can be performed by a group of schoolchildren, and give interesting and useful results.

In geobotanical research, the main object of study is phytocenosis.

In domestic geobotanical literature, the definition given by V.N. Sukachev is most widely used: “A phytocenosis (plant community) should be understood as any collection of plants in a given area of ​​territory, in a state of interdependence and characterized by both a certain composition and structure, and a certain relationship with the environment...”

Phytocenosis- this is not a random collection of plant species, but a natural collection of species that have adapted in the course of evolution to coexistence under certain environmental conditions. The totality of all phytocenoses certain territory called vegetation, or the vegetation cover of a given area.

To describe phytocenoses, the following main features are used:

1) species (floristic) composition;

2) quantitative and qualitative relationships between plants - the abundance of different species and their different significance in the phytocenosis;

3) structure - vertical and horizontal division of the phytocenosis;

4) the nature of the habitat - the habitat of the phytocenosis.

Geobotanical research is the main form of work of field botanists. Such work includes a comprehensive study of both the plants themselves and their habitat.

The existence and development of phytocenoses directly depends on a complex of physical and geographical factors, primarily on the characteristics of the relief, soils and parent rocks of the given territory. In turn, plants and the phytocenoses formed by them change their habitat and therefore can be used as indicators (especially species and phytocenoses with a narrow ecological amplitude) various features natural conditions.

This technique is proposed for use for educational purposes with young geobotanists.

Materials and equipment

When carrying out the simplest geobotanical description You will need:

Description form (see sample at the end);
- a simple pencil or pen; preferable to use with a simple pencil, because text written in pencil is not blurred by water, which is important in field conditions;
- knife - to sharpen a pencil if necessary;
- tape measure or centimeter - for measuring the diameters of tree trunks.

May also be required plastic bag or a herbarium folder for collecting unknown plants and paper bags (envelopes) for collecting mosses.

If a trial plot is to be laid out for complex or long-term research, you will also need a compass or compass, a tape measure (or a rope 10 m long) for marking, an ax for making and hammering marker stakes, a shovel - if marker holes are torn out, and paint - if The site will be marked for long-term monitoring purposes.

Technique of geobotanical description

Task 1. Establishment and marking of a trial plot.

To carry out a geobotanical description, a more or less homogeneous area (in the forest) of 20x20 meters in size (classic version) is selected.

You can mark a trial area different ways, depending on the area and capabilities. You can suggest the following markup option. A wooden stake 3-7 cm in diameter and 2 m in height is driven into one (arbitrary) corner of the future trial area. Near it, from the outside, a marker pit with a depth and width of approximately 30 cm is dug. Its purpose is to serve as an additional landmark for the next at least 10-15 years. A tree can be used instead of a stake if it grows in a suitable location.

From the stake, using a tape measure or a pre-marked rope, measure 10 m to the second corner, where a stake is also placed and a marker hole is dug out. It is somewhat more difficult with the third and fourth corners - you need to repeat the same operation, but maintain a right angle between the sides of the square (usually this is done using a compass or compass). A notch is made on one or several stakes (or trees), on which the number of the trial plot is written, as well as the dates of its laying and the next visits. Inscriptions can be made with a pencil, pen, marker or felt-tip pen. It is advisable to mark each stake (tree) with bright paint to make it easier to find the site on subsequent visits.

After marking the trial area, a standard description is carried out on it using a form and methodology that will be described below.

To simplify the description and unify the described parameters of the physical environment and the phytocenosis itself, a form for describing an area of ​​vegetation cover has been developed (see sample at the end of the text), i.e. a table with pre-drawn graphs for each parameter of the environment description. The forms are filled out directly in the field - at the place where the description is being carried out. Before going into the forest, you should prepare the required number of forms, and only fill them out during work.

PROCEDURE FOR COMPLETING THE PHYTOCOENOSIS DESCRIPTION FORM.

Filling out the header of the form

First, you need to fill in the form with general information about the description and the place where it was held: date, author, description number.

It is recommended to describe in detail the geographical and local location - region (region, territory, republic), district, nearest settlements. Where possible, the local situation is described in detail - i.e. how to directly find the location of the description (this is especially important if you plan to monitor these areas in the future). For example: 0.4 km north of the village of Nikitina, on a hill, near the corner of the forest; or 0.85 km along the road to the highway from the village of Luzhki, then 80m to the southeast, near a large boulder.

Position in the relief - an arbitrary description of the location of the research point (areas): on level ground; on a slope towards a stream or ravine; on the river terrace; in a depression, ravine, on a hill, on a hillock, on a river bank, on the edge of a cliff, etc.;

Environment - described character traits surrounding the place work of the area - a swamp, meadow, field, any forest, the bank of a river or stream, the presence of a road or other man-made object, etc.;

Described area (MxM) - the size of the established site or the described biotope. For a forest, a site size of 20 m x 20 m is usually proposed. For greater accuracy of the description, several sites should be established in different, but similar in terms of conditions, areas of the forest.

Note. If you select areas with different levels of anthropogenic load and carry out descriptions, you will simultaneously receive work on ecology - an assessment of the level of anthropogenic impact.

Task 2. How to correctly name the described phytocenosis.

The technique assumes that the participants already know the plant species growing in the selected phytocenosis. However, if you do not know all of them, then you first need to identify plants to species using identification guides or consult with a teacher in order to identify each species without problems in the future.

The name of the community is formed from the names of the dominant species (or ecological groups) of plants in each of the tiers of the phytocenosis. In this case, the names of species within each tier are listed in increasing order of their relative abundance.

The full name of a forest phytocenosis includes four main components of the vegetation cover - tree layer, shrub layer, grass-shrub layer and moss-lichen layer.

In the name of the phytocenosis they are listed in the same order. Depending on the purpose of the description, you can limit yourself to a simplified name of the forest type, listing the main ecological groups of plants that form the phytocenosis, for example: birch-pine green moss-forb forest. This means that in such a forest the forest stand is dominated by pine and birch, and the moss-lichen cover is dominated by the ecological group of green mosses ( different kinds), and in the grass-shrub cover there are cereals and meadow plants of rich soils.

Forests with a developed moss-lichen cover are usually divided into three types, corresponding to the prevailing environmental groups of this tier: white moss (with a cover of lichens), long-moss (with a cover of sphagnum and polytrichum) and green moss.

Task 3. Description of the tree and shrub layers of the forest.

After filling out the header of the form ( general information about the biotope), it is necessary to describe the tree and shrub layers.

According to this method, when filling out a vegetation description form, it is proposed to determine the indicators of crown density and tree stand formulas separately for each of the high-altitude forest canopies - for a ripe and ripening tree stand - separately, for undergrowth (an independent canopy as part of a tree layer) - separately, and for the undergrowth (independent tier) - separately. This is due to the practical convenience of such a division and the relative simplicity of the procedure for recording the abundance of tree and shrub plants. But, if this seems complicated to you, the description can be simplified.

Determination of crown density

The description should begin with an assessment of crown density. Density refers to the proportion of the earth's surface area occupied by crown projections. One can also characterize density as that part of the sky that is covered by crowns - in other words, evaluate the relationship between " open air" and crowns.

Crown density is usually expressed in fractions of a unit - from 0.1 to 1, i.e. the absence of crowns is taken as zero, and the complete closure of crowns - as 1. In this case, the gaps between the branches are not taken into account - the “crown” is considered to be the space outlined mentally along the outer branches (perimeter) of the crown. To assess the canopy density of a tree layer, it is best to lie on the ground, look up and assess how much the sky is covered by branches and leaves. Of course, the assessment is given approximately, “by eye”. Therefore, several people can do this, and then the average value must be calculated.

After assessment species composition and crown density of the tree layer, it is necessary to evaluate these indicators for regrowth and undergrowth.

Pay attention to the meaning of these terms: young trees of the main forest-forming species of a given forest are called young trees with a height of up to 1/4 of the main canopy (ripe and ripening tree stand).

The undergrowth stands out as an independent canopy of the tree layer.

Undergrowth is woody and shrubby plants that can never form a tree stand.

A typical example of undergrowth in a pine-spruce forest can be young spruce, pine, birch, and undergrowth - willow, rowan, buckthorn, raspberry, etc.

Determining the “closeness” of the crowns of undergrowth and undergrowth is a little more difficult - they cannot be “seen in the light” from bottom to top. Therefore, to determine the abundance (relative abundance) of herbaceous and shrub plants in geobotany, another indicator is used - projective cover. It is expressed as a percentage - less than 10% - single plants, 100% - complete "closeness" of plants.

Determination of the forest stand formula.

Having assessed the canopy density, we move on to compiling a forest formula - estimating what share each individual species makes up in the tree and shrub layers.

The share of species in the forest formula is usually expressed in points - from 1 to 10. The total volume of the crowns of all plants is taken as 10 and the proportion of each species is estimated. Separately standing plants, according to their representation in the forest not reaching 10% (less than 1 point), are marked in the formula with a “+” sign, and single plants (1-2 in the study area) with a “unit” sign.

The names of species in the forest formula are abbreviated to one or two letters, for example: birch - B, oak - D, pine - C, spruce - E, aspen - Os, gray alder - Ol.s., black alder - Ol.ch., linden - Lp, larch - Lts, buckthorn - Kr, raspberry - Ml, etc.

Look at examples of formulas for the canopy of a mature tree stand:

1) Formula 6E4B means that a mature forest stand is 60% spruce and 40% birch.
2) Formula 10E means that the planting is clean and consists of one tree species - spruce.
3) Formula 10E+B means that in the forest stand, in addition to spruce, there is a slight admixture of birch.

The difference between the forest stand formula and the density indicator is that the formula includes all species of tree and shrub plants without exception, even rare and isolated ones. And when assessing the density, these species are not taken into account at all, as they are insignificant in the overall crown space (since it is almost impossible to quantify the density of the crowns of trees or single specimens located far from each other).

The table below shows a sample entry. It means: in the forest described there is a dense, closed canopy of ripe and ripening trees. 80% of the space in the upper part of the forest is occupied by crowns. At the same time, spruce predominates; pine and birch are found in smaller numbers and in equal quantities. There is a fairly dense spruce regrowth in the forest (intensive regeneration is underway). The undergrowth is sparse and consists of buckthorn and hazel in approximately equal proportions with individual patches of raspberries.

Using these formulas, you can immediately imagine what the forest looks like.

Evaluate these indicators on test sites and fill out a similar table.

If you have the time and desire, you can conduct additional research for more detailed description phytocenosis (see information below).

Task 4. Determination of trunk diameter, tree stand height and plant age.

The description of the tree and shrub layers also includes the following: important information about their structure such as trunk diameter (D 1.3), tree stand height (Hd) and plant age.

The diameter of the trunks is measured for several trees typical for a given forest at breast height (~1.3 m) and then the average value is calculated. If necessary, you can also mark the minimum and maximum values ​​for each canopy. Measurements are carried out either with a special fork (large caliper) or through the circumference. To do this, the trunk circumference of several trees is measured, then the average value is used to determine the diameter using the formula D = L / p, where D is the diameter, L is the circumference, and p is a constant number "Pi" equal to approximately 3.14 ( in the field, the circumference is simply divided by three).

On the image The device of such a measuring fork is shown; you can make it yourself.

Tree stand height (Hd) - minimum, maximum and average height values ​​of trees of each species separately.

Height measurement is usually carried out in one of four ways: 1) by eye (which requires great experience), 2) by measuring with a tape measure or meter one of the fallen trees in a given canopy, 3) by counting the “men,” and 4) by measuring the shadow.

The third method is to measure together. One person stands next to the tree, and the other, with a good eye, moving some distance away to take in the entire tree from the butt to the top, “puts down” by eye how many people given growth"lays" along the entire length of the trunk. In this case, it is more rational to set aside a distance each time that is twice as large as the previous one, i.e. mentally first set aside the height of two “men”, then add two more to them, then four more, then eight more, etc. (i.e. according to the scheme 1-2-4-8 -16). From the point of view of the human eye, this is simpler and more accurate. Knowing the height of the “little man”, you can calculate the height of the tree.

The fourth method - the most accurate of the indirect methods - is used in sunny weather. The shadow from standing man, whose height is known. Next, the shadow of the tree under study is measured. In a dense forest, when the shade of a particular tree and, especially, its tops is difficult to find, we can recommend the following method. Move away from the tree in such a way that the person’s gaze (head), the top of the tree and the sun lie on the same line, and then find the shadow of your own head on the ground - this will be the shadow of the top of the tree. All that remains is to measure the distance between this point and the base of the tree and determine the height of the tree according to the proportion: the length of a person’s shadow/his height - the length of the tree’s shadow/its height.

There are also more accurate methods for measuring heights using an eclimeter or altimeter. Detailed Specifications The design of these instruments and the measurements they can take can be obtained from the manuals supplied with the individual models.

The average height of a rock in a particular phytocenosis is determined as the arithmetic mean of several trunks with an average diameter.

The age of plants is most reliably determined by the annual rings of cut trees, which, if desired, can be found in almost any forest. The rings should be counted as close to the base of the tree as possible. You can also use a fresh stump, if there are any in the forest. Under no circumstances (even for the sake of science) should you cut down a tree yourself. Try to find stumps of the appropriate diameter. If the forest was planted, then you can find out when this happened and determine the approximate age of the trees.

The age of undergrowth, especially spruce and pine, can be determined by whorls. In these plants at a young age (up to 30-40 years), dead (in the lower part of the crown) or living (in the upper part) branches are preserved along the entire length of the trunk, which grow in bunches - whorls, several branches at the same level along the circumference of the trunk. The number of such whorls, from the base of the trunk to its top, approximately corresponds to the age of the tree, because in one growing season the tree grows by one whorl. Three years should be added to the number of years obtained when counting whorls to take into account the period of rooting and the beginning of growth.

Task 5. Description of the grass-shrub and moss-lichen layers in the forest or the grass layer in the meadow.

The form for describing an area of ​​vegetation cover provides for the presence of various forms of microrelief in the area being described - hummocks (in other words, elevated micro-areas) and inter-humocks (i.e., depressions), which usually differ in the species composition and distribution of plants. If there are no such forms of microrelief in the area being described, then the entire description of the grass-shrub and moss-lichen layers can be written in one column, and the subheadings “tussocks” and “inter-tussocks” can simply be crossed out.

The size of sample plots in phytocenoses with herbaceous vegetation is usually 10 m x 10 m, and in raised bogs it is sometimes only a few m2.

The characteristics of the herb-shrub layer in a forest and swamp or grass layer in a meadow also begin with the determination of the general projective cover. In this case, the ratio of plant projections (minus the gaps between leaves and branches) to the total area, taken as 100%, is visually taken into account. The accuracy of accounting for projective coverage can be significantly increased by dividing the trial area into smaller areas: in each resulting square, the coverage is taken into account separately, and then the average value is determined.

For the same purpose, geobotanists use a Ramensky grid, which is a small plate in which a rectangular hole measuring 2 x 5 or 3 x 7.5 cm is cut out. The hole is divided with white thread or thin wire into 10 square cells (cells) of 1 or 1, 5 cm2 each. By examining the grass stand through such a mesh hole, it is determined how many cells (i.e., tenths of the hole) are in the vegetation projection and how many are in the uncovered soil surface showing through the grass stand. At the same time, projections or empty spaces are mentally crowded towards one end of the grid. Repeated surveys of coverage in different places of the trial plot make it possible to obtain average value this indicator with fairly high accuracy. The developed standards of gradations of projective coverage help in this.

Standards of gradations of projective cover (in%) of grass stand, considered in the Ramensky grid

When filling out the form in the “herb-shrub layer” column, the names of the plants are written in one column, or in several if the entire list does not fit in one column. It is advisable to indicate shrubs (blueberries, lingonberries, etc.) first in the list, and then herbaceous plants in descending order of their number (projective cover). Rare plants, with a projective coverage of less than 5%, are combined with a curly bracket, opposite which the total value of their projective coverage is placed. Single plants, as in the case of the tree and shrub layer, are marked with the “unit” icon.

In the same way as the herbaceous-shrub layer, the moss-lichen layer is then described, also indicating the names of the mosses and lichens encountered (if they are present on the soil and their identification is possible) and the projective cover of each species.

Unknown plant species encountered during the description are selected for the herbarium and taken with them for further identification. At the same time, in the description form they are given a certain number (index), which, after the determination is made, is replaced by the species name.

After completing the general characteristics of the grass cover of the phytocenosis, they proceed to identifying the floristic composition of the sample plot and the characteristics of each plant species. It is best to start compiling a list of species from one corner of the site, first writing down all the plants that come into view. Then, slowly moving along the sides of the square, the list is supplemented with new species and only after that the sample area is crossed diagonally. You should examine the grass stand very carefully, since from a height of human height it is not possible to see all the plants. Many of them, smaller ones, are well hidden under the leaves and stems of large grasses and can only be discovered by moving the grass stand apart with your hands and examining the most hidden corners.

After compiling the list of species as a whole is completed, you can start assigning them to one or another substage. In some cases, identifying the layered structure of the herbaceous cover is quite difficult, and then you can limit yourself to only indicating the height of the plants and the upper level of the densest phytomass. In cases where individual tiers are well differentiated from each other, they are numbered from highest to lowest and for each the dominant types and heights of development are indicated.

The degree of participation of individual species in the grass stand is determined by methods of recording their relative abundance. The most common of these methods is the use of the Drude scale (Table 1), in which different degrees of abundance are designated by scores based on the values ​​of the smallest distances between individuals of a species and their occurrence.

TABLE 1. Abundance assessment scale according to Drude (with additions by A.A. Uranov)
Abundance designation according to Drude Characteristics of abundance Average shortest distance between individuals (counting units) of the species, cm

Points Sor (copiosae) in this case, abundant plants are designated, the average shortest distance between individuals is no more than 100 cm. As a result, plants also have a high occurrence - no less than 75%. Large and medium-sized plants usually play a significant role in the overall appearance of a phytocenosis or a separate layer, becoming completely or partially background. Within this score there are three levels:

sor3 – very abundant, the average shortest distance is no more than 20 cm. The occurrence is therefore, as a rule, 100%. Such plants usually (with the exception of very small plants) form the main background of vegetation or a separate layer;

sor2 – abundant, average shortest distance – from 20 to 40 cm. Occurrence sometimes (with a somewhat uneven distribution) is slightly below 100%. Such plants often, especially in the absence of others, more or equally abundant, but larger, play the main or at least significant role in the physiognomy of the association site, creating a continuous background;

cop1 – quite abundant, average shortest distance from 40 to 100 cm. Occurrence usually does not fall below 75%. The role of such plants in the appearance of the site is smaller; they do not form a background, but they can significantly influence the appearance of vegetation, representing numerous inclusions in the mass of herbage, especially noticeable with a specific growth form or large size of individuals.

Point Sp scattered plants are noted, the average shortest distance between which is 1–1.5 m. They are found almost every 1–2 steps, but, as a rule, they do not form a background (except for very large plants) and have physiognomic significance in the herbage only in case of noticeable contrast with others.

Single plants are designated by a Sol score. They are far apart from each other - the shortest distance is always more than 1.5 m. The occurrence is low, no higher than 40%. These plants have no background significance, although sometimes, differing in their growth form, bright color and size, they are quite noticeable among the rest.

In the case of fluctuations in abundance between two stages, combined estimates are sometimes used, for example sol–sp, sp–сop1, etc.

The Drude scale is extremely simple and easy to use. But this method is suitable only for a schematic, largely subjective, determination of the relationship between species and the identification of the main species from total mass. An idea of ​​how the results obtained using the Drude scale compare with those obtained using other, more accurate methods can be obtained by considering Table. 2.

TABLE 2. Drude scale scores

Task 6. Determination of plant phenophases.

The phenophase or phenological state of a plant means one or another phase of its development. To designate them when describing phytocenosis, the system proposed by V.V. is most often used. Alekhine (1925) – table. 3.

TABLE 3. Designation system for phenophases according to V.V. Alekhine (with additions)

If you conduct such a study several times over the summer, you will get a schedule of changes in plant phenophases. If species diversity is high, select a few species that are most interesting to you. You can also note the air temperature on observation days. As a result, if you monitor for several years, you can find out what has a greater influence on plant development – ​​day length or temperature. But this is a topic for a separate work.

When characterizing moss-lichen cover The percentage of soil coverage with mosses is noted - overall and by type. It is also very important to show the nature of the distribution of mosses and lichens, which depends on the microrelief, the influence of the crowns of trees and shrubs, fallen trunks, etc., as well as the substrate on which they grow.

Task 7. Filling out the form for describing the phytocenosis.
Vegetation area description form
Description No:

Date of:
Geographical and local location:
Position in relief:
Environment:
Described area (m x m):
Name of the community (by dominants of the main tiers):

D (1.3) - average diameter of trunks at chest height (1.3 meters) in cm; N(d) - average height of the tree stand in meters.

Herbaceous-shrub layer
Bumps:
Mezhkochya:
Moss layer
Bumps:
Mezhkochya:

We wish everyone to combine business with pleasure - walk through beautiful forests and meadows and at the same time do research work.

In forest phytocenoses, all the features of plant communities are most clearly expressed, which is probably due to the very long history of their evolutionary formation. This allows us, based even on the consideration of one example, to say what a phytocenosis is.

Phytocenosis(from the gr. phyton - plant and koinos - general) - a stable system of autotrophic and heterotrophic organisms (biota) co-existing on a certain area of ​​the earth's surface and the phytocenotic environment created by them and their predecessors (including soil and phytoclimate), a system characterized by a specific structure and complex relationships of components (cenobionts) both among themselves and and with the phytocenotic environment, which is productive and participates in the circulation of substances.

This definition excludes the possibility of classifying various unstable temporary systems or forms of coexistence of organisms as phytocenoses, which, as a rule, are only the initial (procenoses) or intermediate (ancenoses) stages of the formation of stable communities. Such unstable forms are the vast majority of cultural cenoses created by man, the existence of which is supported by man himself (agrocenoses) and which, when his tutelage ceases, embark on a long path of restoration of phytocenoses. For the same reason, so-called heterotrophic phytocenoses cannot be classified as phytocenoses (biocenoses) (Rabotnov, 1976). If these important divisions are not made, then the vegetation cover may appear to the geobotanist as something completely chaotic, difficult to delimit and map. S.I. Korzhinsky had this point of view (1888, see also section 1.1), as G.F. Morozov (1904) wrote that “only a set of sustainable plantings can and should be called a forest.”

The presence of a phytoenvironment in phytocenoses (Reverdatto, 1935; Bykov, 1953), or, better said, a phytocenotic environment (Lavrenko, 1959), is recognized by most geobotanists (social - according to Pachosky, 1921; biologically modified - according to Sukachev, 1928; endogenous - according to Gounot, 1956; internal - according to Yaroshenko, 1961), however, as a rule, it does not appear in definitions of phytocenosis. If we add to this that autotrophic, like many heterotrophic components in phytocenoses, for example fungi, draw all nutrients, including carbon and oxygen, from resources internal environment communities, that many relationships of coenobionts with each other occur through this environment, and that it itself is not only inseparable from the phytocenosis, but also quickly degrades or even disappears after its destruction, then it will become clear that the phytocenosis cannot be considered only a collection of organisms.

Life exists on different conditions its organizations are cell, organism, population, species and biocenosis, each of them has its own characteristics. One of the features of the last level of life - biocenosis - is its biocenotic environment.

For geobotanists, all this is quite clear; it is not without reason that many of them, while studying the vegetation cover, simultaneously study the soils underneath it or do this in collaboration with soil scientists. Without such a study, many features of phytocenoses, in particular environmental ones, are especially difficult to understand and explain.

When considering and defining phytocenosis, we include in it not only autotrophic, but also heterotrophic organisms, and not only heterotrophic plants, but also animals. Of course, a geobotanist is not a zoologist, but without taking into account the activities of a number of animals, especially phytophages, it is impossible to understand many aspects of the autoregulation of communities and their stability. And almost no serious geobotanist ignores pests of forests, meadows and pastures. Some geobotanists (Gams, 1918; Du-Rietz, 1930, 1965) in this regard prefer to use the term “biocenosis” rather than “phytocenosis.”

The share of participation of the animal population in phytocenoses usually does not exceed 0.1% by biomass. Comprehensive studies of phytocenoses (stationary) usually take place under the auspices of geobotanists. In all this lies the depth and attractiveness of geobotanical research.

Having accepted phytocenoses as terrestrial biocenoses, we, of course, will focus on their floristic composition and phytocenotic environment, and only in necessary cases will we turn to the biota as a whole.

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 the 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.

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, thanks to which upper layer 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.

For various types 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 every kind, even his age groups 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.

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.

Coastal aquatic phytocenosis

forest ruderal phytocenosis vegetation

The floristic composition of coastal aquatic vegetation depends on different environmental conditions of water bodies: chemical composition water, characteristics of the soil that makes up the bottom and banks, the presence and speed of currents, 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. In connection with aquatic environment and lifestyle, three groups of plants are distinguished: true aquatic plants, or hydrophytes (floating and submerged); air-water plants (helophytes); coastal aquatic plants (hygrophytes).

The phytocenosis is characterized by:

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

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

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

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

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

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 in the forests northern Finland 7 tiers:

1. top woody,
2. lower woody,
3. undergrowth,
4. top grass,
5. medium herbal,
6. lower grass,
7. ground

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

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

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 to vegetative propagation and 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, water, etc.

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

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

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

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

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

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

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