The totality of phytocenoses of a certain territory is called. Characteristics of the main types of phytocenoses of the globe. Interactions of organisms in phytocenoses
Phytocenosis is characterized by species composition, quantitative and qualitative relationships between plants, layering, mosaic, physiognomy, periodicity, synusiality, and the nature of the habitat.
species composition. The composition of phytocenosis includes higher plants, bacteria, algae, accinomycetes, fungi and lichens. They grow on the soil, in the soil, and some are epiphytic plants. The totality of individuals of a species within a plant community forms a coenotic population, or cenopopulation. The species composition of a community is a set of cenopopulations. A species is a system of populations. A population is a group of individuals that is an elementary subdivision of a species, its elementary evolutionary structure.
Cenopopulations of individual species in the same plant community can differ greatly from each other both in the number of individuals per unit area and in the ratio of individuals of different age groups (age spectrum).
The main age periods of plant life are latent, virgil, generative, senile. The presence in the population of a plant species in different age phases ensures the stable position of the species in the community and is an indicator of its normal viability. There are populations of invasive, normal and regressive types.
Populations of an invasive, i.e., invading, type only take root in a phytocenosis and can exist in the form of seedlings, juvenile or immature individuals. Seeds of such species are introduced from outside and eventually occupy an important position in the phytocenosis or do not take root in it at all. Populations of the regressive type have lost the ability for generative renewal. They do not bloom, and if they bloom and bear fruit, then their seeds do not germinate or the seedlings are not viable. The noted signs characterize a population that is dying out, i.e., leaving a given phytocenosis. Plants of populations of the normal type pass through the entire development cycle in the phytocenosis. They are represented by individuals of different periods of life from spores and seeds to adults. In terms of cenosis, these are the main populations of phytocenosis.
The species composition of the phytocenosis is determined by the climate, edaphic conditions, the dissected relief, the impact of biogenic and anthropogenic factors, the biological characteristics of the species, and other reasons.
The number of species growing per unit area is the species (floristic) saturation of the community, which indicates the completeness of the use of the environment within the phytocenosis.
Quantitative and qualitative relationships between plants. A quantitative indicator of the importance of a species in the life of a phytocenosis is its abundance. It is expressed in weight categories, points, the number of individuals per unit area. The ratios between individuals of a phytocenosis are a consequence of the adaptation of species to living together and are determined by environmental conditions. They are not stable. Changes are primarily a reaction to the natural course of meteorological conditions during the season of the year, for many years, or are caused by the peculiarities of the relationship between plants, biogenic and anthropogenic factors.
The qualitative role of different populations in the composition of communities is not the same. In phytocenosis, it is customary to distinguish between dominants (condominants), subdominants, assectators, anthropophytes.
Dominants - species that prevail in the community. By the predominance of a species is meant its greater role in comparison with other species. The predominance is determined by the projective cover of the species, the number of individuals, their weight or volume. This is the most productive population of phytocenosis.
If the phytocenosis is simultaneously dominated by two or more species belonging to the same ecobiomorph, they are called condominants.
Species that mainly determine the specific environment of the community, i.e., have the maximum environmental role, are called edificators. They largely determine its species composition and structure, since they affect the water, temperature regime of the environment and acidity, and at the same time the nature and course of soil-forming processes.
Subdominants - species that prevail in the subordinate layers of the phytocenosis constantly or in certain seasons.
Assectators are secondary species, included in the composition of various tiers.
Anthropophytes are random species in the phytocenosis. Their stay can be completely anthropogenic.
Dominants, subdominants, assectators and arthropophytes are called phytocoenotypes.
Layered. In the process of formation of phytocenosis, plants develop various ecological niches in space. Layering refers to the arrangement of plant organs of various species at different heights above the soil surface and at different depths in the soil. The main structural part of the phytocenosis is the layer. A layer is a part of the population of a phytocenosis, ecologically and phytocenotically isolated in space, and sometimes in time.
Each tier has its own microenvironment (lighting, temperature, humidity, air composition and movement) and is, to some extent, an independent formation. At the same time, the tier is part of a single whole - phytocenosis. In forests, 3-5 tiers are usually distinguished: I (A) - trees of the first size, II (A') - trees of the second and third sizes, III (B) - shrubs (undergrowth), IV (C) - grasses and shrubs, V (D) - mosses and lichens.
Mosaic - horizontal dismemberment within a phytocenosis. Mosaic spots are called microphytocenosis, microassociation, microgrouping.
A microgroup is the smallest element of the horizontal division of a plant community, covering all its tiers and therefore having a certain integrity, which does not exclude a constant relationship with other microgroups both in space and in time.
The presence of microcenoses is primarily a consequence of the heterogeneity of conditions in a phytocenosis, namely, microconditions of a very different order, mutual influences, features of vegetative and mixed reproduction of individual plants. Of paramount importance are the mutual influence and conditions of the ecotope: nanorelief, differences in the mechanical and chemical composition of soils, moisture, shading, litter thickness, and litter features.
Synusality
Synusia are structural parts of phytocenoses, characterized by a certain species composition, a certain ecological character of the species that make them up, and spatial (or temporal) isolation, and, consequently, a special phytocenotic environment (microenvironment) created by the plants of this synusia.
Synusia is not any structural part of a phytocenosis, but formed by a group of plants with a homogeneous or similar ecology. A tier can also be a synusia, if the species that make it up belong to the same life form, and a microgroup (in homogeneous phytocenoses).
Phytocenosis is a complex complex of synusia. The study of individual synusia allows us to more fully understand the species composition, structure and dynamics of phytocenosis.
Physiognomy. The appearance of the phytocenosis, i.e. its physiognomy is determined by the life forms that make up the phytocenosis. The appearance of a phytocenosis, determined by the phases of seasonal development, is called an aspect.
The combination of plants with different rhythms of seasonal development makes it possible for a large number of species to co-exist in communities and make fuller use of the environment by plants.
Periodicity. The seasonal change of aspects is associated with seasonal changes in the life of the community. The frequency of phytocenosis is characterized by seasonal changes in all life processes of plants (transpiration, respiration, photosynthesis and the release and consumption of various substances from the environment, reproduction, etc.), which are determined by the seasonal course of meteorological conditions and physicochemical processes occurring in the soil.
the nature of the habitat is a set of ecological features of a given area, which determine the possibility of the existence of biocenoses. A habitat is understood not only as a place where a phytocenosis grows, but also as a qualitative characteristic of a given area. The quality of the habitat is determined by many factors, the most important of which are the climate of the area, the height above sea level, the shape of the surface (exposure, the angle of inclination of the slopes), rocks and their influence on the soil-forming process, the groundwater regime, the possibility of flooding the area, the origin, type, age of the soil and its physical, chemical and biological features. In the habitat of a phytocenosis, the influences of all components are closely intertwined.
The essential features of phytocenosis are phytocenotic relationships between plants and differences in the phytoenvironment. If mutual influences between plants are not expressed, it means that there is simply a grouping, or aggregation, of plants, but there is no phytocenosis.
Phytocenosis classification units
The classification unit of phytocenoses is an ascending series: an association, a group of associations, a formation, a group of formations, a class of formations, and a type of vegetation.
A plant association (type of phytocenosis) combines phytocenoses with a simultaneous species composition, a homogeneous synusial structure that reflects the composition of ecological plant types, and homogeneous environmental factors that affect the phytocenotic process.
The establishment of associations is, first of all, a generalization, a selection of common and essential features, but not a characteristic or description of it. It should be considered as a type of plant community.
Association Criteria:
One and the same tiered addition, i.e. number and nature of tiers
Similar tiling
The same feeds must be edifiers and dominants in the respective tiers
Similar composition and ratio of the role of species of different ecological affiliation
Similar course of seasonal variability
Similar year-to-year changes
Similar course of age-related changes
Similar vitality of the main components
More or less similar responses to the same impact.
The names of associations are composed of the generic name of the dominant (condominant) and subdominant.
association group. Associations are grouped. One group includes associations that differ in the composition of one of the tiers. Groups of associations form a natural ecological series, reflecting changes in trophicity, moisture content, and soil aeration.
The formation is distinguished by one common feature - the dominant. The name of the group-associations are combined into a formation. Formation is the basic unit of middle rank. Its importance is great in forest typological studies, forestry activities and vegetation mapping.
Formation groups. One group includes all formations, the dominants of which belong to the same life form.
Formation class. One class includes all groups of formations, the dominants of which belong to close life forms.
Vegetation type is the largest subdivision of vegetation cover. Types are distinguished by morphological or ecological-morphological characteristics. One type of vegetation includes all formations whose associations in the dominant layer are composed of the same biomorph.
Vegetation types are zonal, azonal and extrazonal. Zonal vegetation occupies leveled watershed spaces with well-drained soils of medium mechanical composition (sandy loam, loam).
The azonal type of vegetation develops in places where the vegetation cover is more determined by soil conditions than by climate.
Certain areas of herbaceous vegetation are close to extrazonal.
Forest vegetation.
The study of phytocenoses is studied from the forest - the main zonal type of vegetation. A forest is a community, or such a combination of woody plants, in which they mutually influence each other, thereby giving rise to a number of new phenomena that are not characteristic of equally growing trees. The forest is the basis of the green cover of the Earth, the main component of the geographical landscape. It has a decisive influence on the hydrological regime of rivers and reservoirs, protects the soil from erosion, affects the chemical composition of the atmosphere, is a habitat for wild animals and birds, and is of great sanitary, hygienic and aesthetic importance.
4.1 Species structure of forest phytocenosis
Table 4.1 Species structure of forest phytocenosis
Conclusions: when studying the method of laying raunkiers on a trial plot, the vegetation of a forest phytocenosis was studied. The bulk of the vegetation is bilberry (31.6%) and winding pike (17.25%), lingonberries, meadow maryannik and common heather were found with single species. The projective moss cover was 70%, and was represented by one species - Hylocomium proliferum.
4.2 Spatial structure of forest phytocenosis.
The tier is the main structural unit of the vertical composition of the biocenosis. A tier is a layer of biocenosis, which is formed by a group of plants of the same height, this concept:
1. morphological (the layer is formed by the life forms of plants - the more complex the life forms, the more complex the structure)
2. ecological (the tier is composed of species of different groups - the tendency of alignment in the tier)
3. phytocoenotic - this is a layer of the community, saturated with life, which plays an important functional role in the system. All living things are subject to layering.
The composition of the 1st tier includes pine, spruce and birch.
The average age of plants is about 50 years.
The average stand height is 25-28 m.
The average diameter of a pine trunk is 40.6 cm.
The maximum diameter is 60 cm.
Crown density -0.5.
The 2nd tier is represented by: trembling poplar, birch, mountain ash, pine, pedunculate oak.
3 tiers are herbs and shrubs. The composition of the 3rd tier includes: blueberries, lingonberries, heather, reed reed, meadow maryannik, raspberries (juvenile), winding meadow, cat's foot, bark, mosses.
The division of plants into tiers allows each plant to occupy its own ecological niche and reduce competition between species. The spatial structure provides species diversity in the biocenosis.
4.3 Ecological structure of forest phytocenosis
Table 4.2 Ecological structure of forest phytocenosis
Conclusion: During the internship, we analyzed the vegetation of the forest phytocenosis in terms of life forms, relation to light, moisture and soil trophicity. In the blueberry pine forest, we found and described 5 plants. Of these, most are shrubs (60%) and 40% herbs. The most common plants in relation to light are shade-tolerant (60% of the total), the most rare were shade-loving and light-loving plants (20% each). In relation to soil moisture during the study of forest phytocenosis, mesophytes were most common (80% of plants), xeromesophytes were rare (20%). In relation to soil trophicity, oligotrophs (80%) and megatrophs (20%) were most frequently encountered.
Phytocenosis- any specific grouping of plants, throughout the space it occupies, is relatively homogeneous in appearance, floristic composition, structure, and conditions of existence and is characterized by a relatively identical system of relationships between plants and habitat.
The main signs of phytocenoses:
1. Species composition of phytocenosis is determined by climate, edaphic (soil) conditions, dissected relief, the impact of biogenic and anthropogenic factors, and the biological characteristics of species. The totality of individuals of a species within a plant community forms a coenotic population, or cenopopulation. Cenopopulations include plants of different ages, as well as dormant stages, for example, seeds or modified underground shoots of flowering plants.
2. Quantitative ratios of species in the community determine its appearance and reflect the coenotic processes in it. The quantitative relationship between plants in a phytocenosis is expressed by such an indicator as the abundance of a species. It is expressed as the number of individuals per unit area. On the basis of quantity, they distinguish dominants species that dominate the community. Dominance is determined by the projective cover of the species, the number of individuals, their weight or volume. Dominants are the most productive types of phytocenosis. In the event that two or more species simultaneously prevail in the phytocenosis, they are called codominants. anthropophytes– species are random in the phytocenosis, their stay in this community can be short-term. The ratios between the species of phytocenosis are determined by the adaptability of these species to living together and environmental conditions.
Quality Role different populations within the community is also not the same. edificators are the creator species, the builders of the plant community, which determine the main features of its phytogenic environment. Edificators have a maximum environmental role, they affect the water, temperature regime of the environment, the course of the soil-forming process. In this regard, edificators largely determine the species composition and structure of the phytocenosis. Assectaroths- species that have little effect on the creation of a phytogenic environment, these are secondary species that are part of different tiers. satellites- species that are always found only singly.
3. The next sign of phytocenosis is layering – placement of plant organs of various species at different heights above the soil surface and at different depths in the soil. Each tier has its own microenvironment and is, to some extent, an independent entity. At the same time, the tier is part of a single whole - phytocenosis. The number of community tiers is determined by many factors, including climate, soil conditions, and biological and ecological features of the species. Layering ensures the existence of a large number of individuals in a limited area and a more complete use of environmental factors (illumination, water, mineral resources) by plants. The greatest number of tiers is observed in favorable conditions. The tiered arrangement of plants reduces competition and ensures the stability of communities.
4. Mosaic - horizontal dismemberment within the phytocenosis. Mosaic patches are called microgroupings. Usually microgroups are small (up to several meters in diameter). The presence of mosaicity is a consequence of the heterogeneity of microconditions in the phytocenosis: microrelief, differences in the mechanical and chemical composition of soils, and litter thickness. At the same time, the formation of mosaicity is associated with the mutual influence of plants on each other (the creation of shading, the specifics of the litter that affects the soil-forming process,
5. The next feature is synusiality . Synusia- structural parts of a phytocenosis, characterized by a certain species composition, a certain ecological character of the species and spatial isolation. Synusia can be both a tier (if the species that make it up belong to the same life form), and a microgroup (in homogeneous phytocenoses).
Along with spatial synusia, seasonal synusia are also distinguished, represented by species of the same seasonal development. They are characterized by ecological isolation and a certain phytocenotic role in the community.
6. Physiognomy - the appearance of the phytocenosis, which is determined by the life forms that make up the phytocenosis.
7. Periodicity Phytocenoses are characterized by seasonal changes in all vital processes of plants.
8. Nature of the habitat - a set of ecological features of a given area, which determine the possibility of the existence of a biocenosis. A habitat is understood not only as a place where a phytocenosis grows, but also as a qualitative characteristic of a given area. The quality of a habitat is determined primarily by climate, altitude, surface shape, rocks and their influence on soil-forming processes, physicochemical and biological characteristics of soils, groundwater regime, and the possibility of flooding the area.
This assignment is based on theA.S. Bogolyubov and A.B. Pankov.
Such works are based on the methods of description and observation, they are not very difficult, can be carried out by a group of schoolchildren, and give interesting and useful results.
In geobotanical research, the main object of study is phytocenosis.
In the domestic geobotanical literature, the definition given by V.N. Sukachev is most widely used: "A phytocenosis (plant community) should be understood as any set of plants in a given area of the territory that is in a state of interdependence and is characterized both by a certain composition and structure, and by a certain relationship with the environment ...".
Phytocenosis- this is not a random collection of plant species, but a natural set of species that have adapted in the course of evolution to coexistence in certain environmental conditions. The totality of all phytocenoses of a certain territory is called vegetation, or the vegetation cover of this territory.
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 features of the relief, soils and parent rocks of a 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) of various features of natural conditions.
This technique is proposed for use for educational purposes with young geobotanists.
Materials and equipment
When conducting a simple geobotanical description, you will need:
Description form (see sample at the end);
- a simple pencil or pen; it is preferable to use a simple pencil, because. the text written in pencil is not washed out by water, which is important in the field;
- knife - to sharpen a pencil if necessary;
- tape measure or centimeter - for measuring the diameters of tree trunks.
You may also need a plastic bag or herbarium folder to collect unknown plants and paper bags (envelopes) to collect mosses.
If a trial area is to be laid for complex or long-term studies, you will also need a compass or a compass, a tape measure (or a 10 m long rope) for marking, an ax for making and driving marker stakes, a shovel - if marker holes break out and paint - if the site will be marked for multi-year monitoring purposes.
Geobotanical description technique
Task 1. Establishment and marking of a trial plot.
For the geobotanical description, a more or less homogeneous area of 20x20 meters in size (in the forest) is chosen (classic version).
There are many ways to mark out a trial plot, depending on the terrain and possibilities. We can suggest the following markup. In one (arbitrary) corner of the future trial plot, a wooden stake 3-7 cm in diameter and 2 m high is driven in. Near it, from the outside, there is a marker pit about 30 cm deep and wide. Its purpose is to serve as an additional landmark over the next at least 10-15 years. A tree can be used in place of a stake if it grows in a suitable location.
From the stake, using a tape measure or a pre-marked rope, 10 m is measured to the second corner, where a stake is also placed and a marker hole is pulled out. It is somewhat more difficult with the third and fourth corners - you need to repeat the same operation, but keep a right angle between the sides of the square (usually this is done using a compass or compass). On one or several stakes (or a tree), a notch is made, on which the number of the trial plot is written, as well as the dates of its laying and regular visits. Inscriptions can be done 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 plot, a standard description is carried out on it using the form and methodology, which will be described below.
To simplify the description and unification of the described parameters of the physical environment and the phytocenosis itself, a form has been developed for describing the vegetation cover area (see the sample at the end of the text), i.e. a table with pre-lined graphs for each environment description parameter. Forms are filled directly in the field - at the site of the description. Before going out into the forest, you should prepare the forms in the required quantity, and only fill them out during work.
PROCEDURE FOR FILLING OUT THE FORM DESCRIPTION OF PHYTOCENOSIS.
Filling out the form header
First, you need to enter in the form general data about the description and the place of its holding: date, author, number of the description.
It is recommended to describe in detail the geographical and local position - region (region, territory, republic), district, nearest settlements. If possible, the local situation is described in detail - i.e. how to directly find the place of description (this is especially important if monitoring of these sites is planned 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 on 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 point (areas) of the study: on level ground; on a slope to a stream or ravine; on the terrace of the river; in a depression, a ravine, on a hillock, on a river bank, on the edge of a cliff, etc.;
Environment - describes the characteristic features of the area surrounding the work site - a swamp, meadow, field, any forest, river or stream bank, the presence of a road or other anthropogenic object, etc.;
Described area (MxM) - the size of the site laid down or the described biotope For the forest, the size of the sites is usually suggested to be 20 m x 20 m. For greater accuracy of the description, several sites should be laid on different, but similar in conditions, forest areas.
Note. If you select sites with different levels of anthropogenic load and carry out descriptions, then 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 of the work already know the plant species growing in the selected phytocenosis. However, if not all of them are known to you, then you first need to identify plants to a species using determinants or consult a teacher in order to further identify each species without problems.
The name of the community is formed from the names of the dominant species (or ecological groups) of plants in each of the phytocenosis tiers. In this case, the names of species within each tier are listed in ascending order of their relative abundance.
The full name of the 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, one can confine oneself to a simplified name of the type of forest, 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, pine and birch prevail in the stand, in the moss-lichen cover - the ecological group of green mosses (various species), and in the grass-shrub cover - grasses and meadow plants of rich soils.
Forests with a developed moss-lichen cover are usually divided into three types, corresponding to the predominant ecological groups of this tier: white moss (with a cover of lichens), long moss (with a cover of sphagnum and polytrichums) and green moss.
Task 3. Description of the tree and shrub layers of the forest.
After filling in 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 the vegetation description form, it is proposed to determine the indicators of crown density and forest stand formulas separately for each of the high-altitude forest canopies - for a ripe and maturing forest stand - separately, for undergrowth (an independent canopy as part of a tree layer) - separately and for undergrowth (independent tier) - separately. This is due to the practical convenience of such a division and the relative simplicity of the procedure for accounting for the abundance of trees and shrubs. But, if it seems complicated to you, then 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. It is also possible to characterize closeness as that part of the sky that is covered by crowns - in other words, to evaluate the relationship between the "open sky" and crowns.
The density of crowns 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 is taken as 1. In this case, the gaps between the branches are not taken into account - the “crown” is the space outlined mentally along the extreme branches (perimeter) of the crown. To assess the crown density of the tree layer, it is best to lie down on the ground, look up and assess how much the sky is covered with branches and leaves. Of course, the assessment is given approximately, "by eye". Therefore, several people can do this, and then you need to calculate the average value.
After assessing the species composition and canopy density of the tree layer, it is necessary to evaluate these indicators for undergrowth and undergrowth.
Pay attention to the meaning of these terms: young trees of the main forest-forming species of this forest are called undergrowth up to 1/4 of the main canopy (ripe and ripening forest stand).
Undergrowth stands out as an independent tree layer canopy.
Undergrowth is woody and shrubby plants that will never be able to form a stand.
A typical example of undergrowth in a pine-spruce forest can be young spruces, pines, birches, and undergrowth - willows, mountain ash, buckthorn, raspberries, etc.
Determining the "closeness" of undergrowth crowns and undergrowth is a little more difficult - they cannot be "looked into the light" from the bottom up. Therefore, to determine the abundance (relative abundance) of herbaceous and shrubby 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 stand formula.
Having assessed the density of crowns, they proceed to compiling a forest formula - an assessment of what proportion 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 crown volume of all plants is taken as 10 and it is estimated what part each species makes up. Separate plants, which, according to their representation in the forest, do not reach 10% (less than 1 point), are marked in the formula with the "+" sign, and single plants (1-2 in the study area) with the "unit" sign.
The names of species in the forest formula are reduced to one or two letters, for example: birch - B, oak - D, pine - C, spruce - E, aspen -Os, gray alder - Ol.s., black alder - Ol.h., linden - Lp, larch - Lts, buckthorn - Kr, raspberries - Ml, etc.
See examples of formulas for a mature stand canopy:
1) Formula 6E4B means that a mature stand is 60% spruce and 40% birch.
2) Formula 10E means that the plantation is clean, consists of one tree species - spruce.
3) The formula 10F+B means that in the stand, apart from spruce, there is an insignificant admixture of birch.
The difference between the forest stand formula and the density indicator is that the formula includes all types of woody and shrubby plants without exception, even rare and single occurrences. And when assessing the closeness, these species are not taken into account at all, as insignificant in the total space of crowns (because it is practically impossible to quantify the closeness of the crowns of trees or single specimens that are far from each other).
The table below shows a sample entry. It means: in the described forest 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 occur less and in equal numbers. There is a fairly dense undergrowth of spruce in the forest (intensive renewal is underway). The undergrowth is sparse and consists of buckthorn and hazel in approximately equal proportions with individual inclusions of raspberries.
Using such formulas, you can immediately imagine what the forest looks like.
Evaluate these indicators on trial sites and fill in a similar table.
If you have the time and desire, then you can conduct additional research for a more detailed description of the phytocenosis (see information below).
Task 4. Determining the diameter of the trunks, the height of the stand and the age of the plants.
The description of tree and shrub layers also includes such important information about their structure as trunk diameter (D 1.3), stand height (Hd) and plant age.
The diameter of the trunks is measured in several trees typical for the 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 circumference of the trunk is measured on several trees, then the average value is used to determine the diameter according to the formula D \u003d 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 plug is shown, you can make it yourself.
Stand height (Hd) - the minimum, maximum and average values of the height of trees of each species separately.
Height measurement is usually carried out in one of four ways: 1) by eye (which requires a lot of experience), 2) by measuring one of the fallen trees of a given canopy with a tape measure or meter, 3) by counting "little men" and 4) by measuring the shadow.
In the third way, the measurement is carried out together. One person stands next to the tree, and the other, with a good eye, moving a certain distance to cover the whole tree from the butt to the top, "lays" by eye how many people of this height "fit" along the entire length of the trunk. At the same time, it is more rational to postpone the distance each time, twice as much as the previous one, i.e. mentally put off first the height of the two "little 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 of a standing person whose height is known is accurately measured. Next, the shadow from the tree under study is measured. In a dense forest, when the shadow of a particular tree and, especially, its tops are difficult to find, the following method can be recommended. 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 from your own head on the ground - this will be the shadow from the top of the tree. It remains only 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 the shadow of a person / his height - the length of the shadow of the tree / his height.
There are more accurate methods for measuring heights using an eclimeter or altimeter. Detailed characteristics of the design of these devices and measurements with their help can be obtained in the manuals attached to individual models.
The average rock height in a particular phytocenosis is defined as the arithmetic average of several trunks with an average diameter.
It is most reliable to determine the age of plants by the annual rings of cut down trees, which, if desired, can be found in almost any forest. 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. In no case (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 remain along the entire length of the trunk, which grow in bunches - whorls, several branches at the same level around 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 from the whorl count to account for the period of establishment and start of growth.
Task 5. Description of the grass-shrub and moss-lichen layers in the forest or grass layer in the meadow.
The form for describing the area of vegetation cover provides for the presence on the described area of various forms of microrelief - tussocks (in other words, elevated microsites) and interhummocks (i.e. depressions), which usually differ in species composition and distribution of plants. If there are no such forms of microrelief in the described area, then the entire description of the grass-shrub and moss-lichen layers can be written in one column, and the subheadings "tussocks" and "interstitials" can simply be deleted.
The size of test plots in phytocenoses with herbaceous vegetation is usually 10 m x 10 m, and sometimes only a few m2 in raised bogs.
The characterization of the grass-shrub layer in the forest and in the swamp or grass layer in the meadow also begins with the determination of the total 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 the projective coverage can be significantly increased by splitting the sample 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 the Ramensky grid, which is a small plate in which a rectangular hole measuring 2 x 5 or 3 x 7.5 cm is cut. The hole is divided with a white thread or thin wire into 10 square cells (cells), 1 or 1 each, 5 cm2 each. Considering the grass stand through such a mesh hole, it is determined how many cells (i.e., tenths of the hole) fall on the vegetation projection and how many on the uncovered soil surface through the grass stand. Projections or empty gaps are mentally crowded to one end of the mesh. Repeated surveys of the coverage in different places of the trial plot make it possible to obtain the average value of this indicator with a fairly high accuracy. The developed standards of projective coverage gradations help in this.
Standards of gradation of the projective cover (in %) of the herbage considered in the Ramensky grid
When filling out the form in the column "grass-shrub layer", the names of plants are written in one column, or in several, if the entire list does not fit in one column. At the same time, it is desirable 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 cover of less than 5% are combined with a curly bracket, opposite which is placed the total value of their projective cover. Single plants, as well as in the case of the tree-shrub layer, are marked with the "unit" icon.
In the same way as the grass-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 of the species.
Unknown plant species encountered during the description are selected for the herbarium and taken with them for further identification. At the same time, they are given a specific number (index) in the description form, 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 trial area and characterizing each plant species. It is best to start listing species from one corner of the site, first writing down all the plants that fall into the field of view. Further, slowly moving along the sides of the square, the list is supplemented with new species and only after that they cross the trial plot diagonally. You should look at the herbage very carefully, since not all plants can be seen from the height of human growth. Many of them, smaller ones, are well hidden under the leaves and stems of large herbs and can be found only when pushing the herbage apart with your hands and examining the most hidden corners.
After the compilation of the list of species as a whole is completed, one can start assigning them to one or another substage. In some cases, the identification of the tiered structure of the herbaceous cover is a rather difficult task, and then one can limit oneself only to 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 the highest to the lowest, and for each, the dominant species and heights of development are indicated.
The degree of participation of individual species in the herbage is determined by the methods of accounting for 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 indicated by points based on the smallest distances between individuals of a species and their occurrence.
TABLE 1. Abundance scale according to Drude (with additions by A.A. Uranov)
Abundance designation according to Drude Abundance characteristic Average smallest distance between individuals (counting units) of a species, cm
Points Sor (copiosae) at the same time, abundant plants are designated, the average smallest distance between individuals is no more than 100 cm. As a result, plants also have a high occurrence - not less than 75%. In this case, plants of large and medium sizes usually play a significant role in the general appearance of a phytocenosis or a separate layer, becoming fully or partially background. Within this score, three steps are distinguished:
sor3 - very abundant, the average smallest 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;
cop2 - plentiful, the average smallest distance is from 20 to 40 cm. The 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 site of the association, creating a solid background;
cop1 - quite abundant, the average smallest distance is from 40 to 100 cm. The occurrence usually does not fall below 75%. The role of such plants in the appearance of the site is smaller, they do not constitute a background, but they can significantly affect the appearance of vegetation, representing numerous inclusions in the herbage mass, especially noticeable with a specific form of growth or large sizes of individuals.
Ballom Sp scattered plants are noted, the average smallest distance between which is 1–1.5 m. They are found almost at every 1–2 steps, but, as a rule, they do not form a background (with the exception of very large plants) and have physiognomic significance in the herbage only in case of marked contrast with others.
Single plants are designated by the Sol score. They are far apart from each other - the smallest distance is always more than 1.5 m. The occurrence is low, not higher than 40%. These plants do not have a background value, 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 steps, combined estimates are sometimes used, for example, sol–sp, sp–cop1, 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 selection of the main species from the total mass. An idea of how the results obtained using the Drude scale correlate with those 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 refers to one or another phase of its development. To designate them in the description of phytocenosis, the system proposed by V.V. Alekhin (1925) - tab. 3.
TABLE 3. Phenophase designation system according to V.V. Alekhine (with additions)
If you conduct such a study several times over the summer, you will get a graph of the change in plant phenophases. If the species diversity is high, select a few species that are most interesting to you. You can also note the air temperature on the days of observation. As a result, if you monitor for several years, you can find out what affects the development of plants more - 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 - total and by species. It is also very important to show the nature of the distribution of mosses and lichens, which depends on the microrelief, the influence of crowns of trees and shrubs, fallen trunks, etc., as well as the substrate on which they grow.
Task 7. Filling in the phytocenosis description form.
Land cover description form
Description No.:
The date:
Geographical and local location:
Position in relief:
Environment:
Described area (m x m):
Name of the community (according to the dominants of the main tiers):
D (1.3) - the average diameter of the trunks at chest height (1.3 meters) in cm; H(d) - the average height of the forest stand in meters.
Herb-shrub layer
bumps:
Interstitial:
moss layer
bumps:
Interstitial:
We wish everyone to combine business with pleasure - to walk through beautiful forests and meadows and at the same time do research work.
Phytocenosis- a plant community characterized by relative homogeneity of species composition, determined mainly by habitat conditions, and relative isolation from other communities, consisting of coenopopulations connected by differentiation relations ecological niches and interference, located in conditions of relatively homogeneous habitat conditions and capable of independent existence.
Forest phytocenosis
Phytocenosis is a conditional concept, since, firstly, a community of some plants cannot really exist without interaction with other components. biogeocenosis- zoocenosis, microbiocenosis, biotope, and secondly, according to the concept that dominates today vegetation continuity, any isolation of isolated communities from it is artificial and serves only for the practical purposes of studying vegetation at all levels.
The modern concept of phytocenosis as a conditional, non-existent entity arose on the basis of an individualistic hypothesis developed by the Russian scientist L. G. Ramensky and the American G. Gleason. The essence of this hypothesis is that each species is specific in its relationship to the environment and has an ecological amplitude that does not completely coincide with the amplitudes of other species (that is, each species is distributed "individualistically"). Each community forms species whose ecological amplitudes overlap under given environmental conditions. When any factor or group of factors changes, gradually decrease abundance and some species disappear, other species appear and increase in abundance, and in this way the transition from one type of plant communities to another is carried out. Due to the specificity (individuality) of the ecological amplitudes of species, these changes do not occur synchronously, and with a gradual change in the environment, the vegetation also changes gradually. Thus, plant communities do not form distinctly isolated units, but are connected by transitional communities into a continuously varying system.
The main directions in the interpretation of the concept of "phytocenosis structure"
Depending on the specifics of research in the concept of "biocenosis structure" V.V. Mazing (1973) distinguishes three directions developed by him for phytocenoses.
1. Structure as a synonym for composition (species, constitutional). In this sense, they speak of species, population, biomorphological (composition of life forms) and other structures of the cenosis, meaning only one side of the cenosis - the 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 confinement to ecological niches and occupy a certain space. This also applies to other components of biogeocenosis. Between the parts of the spatial division (tiers, synusia, micro-groups, etc.) one can easily and accurately draw boundaries, put them on the plan, calculate the area, and then, for example, calculate the resources of useful plants or animal feed resources. Only on the basis of data on the morphostructure, it is possible to objectively determine the points of setting up certain experiments. When describing and diagnosing communities, a study of the spatial heterogeneity of cenoses is always carried out.
3. Structure, as a synonym for sets of connections between elements (functional). The understanding of the structure in this sense is based on the study of relationships between species, primarily the study of direct relationships - the biotic connex. This is the study of food chains and cycles that ensure the circulation of substances and reveal the mechanism of trophic (between animals and plants) or topical relationships (between plants - competition for nutrients in the soil, for light in the aboveground sphere, mutual assistance).
All three aspects of the structure of biological systems are closely interconnected at the coenotic level: the species composition, configuration and placement of structural elements in space are a condition for their functioning, i.e. vital activity and production of plant mass, and the latter, in turn, largely determines the morphology of cenoses. And all these aspects reflect the environmental conditions in which biogeocenosis is formed.
Phytocenosis in the system of organization of living matter
Phytocenosis is a part of biocenosis along with zoocenosis and microbiocenosis. The biocenosis, in turn, in combination with the conditions of the abiotic environment (a biotope consisting of an edaphotope and a climatotope) form a biogeocenosis. Phytocenosis is the central, leading element of biogeocenosis, as it transforms the primary ecotope and creates a coenotic habitat for living organisms, and is also the first link in the energy cycle. Soil properties, microclimate, composition of the animal world, such characteristics of biogeocenosis as biomass, bioproductivity, etc. depend on vegetation.
In turn, the elements of the phytocenosis are the coenopopulations of plants - the totality of individuals of the same species within the boundaries of the phytocenosis. Cenopopulations of the same species have different characteristics in different phytocenoses.
Factors of organization of phytocenosis
Factors of plant community organization can be divided into four groups: characteristics of the environment, the relationship between plants, the effect of heterotrophic components on vegetation, and disturbances. These three groups of factors determine the combination and characteristics of species coenopopulations in a phytocenosis.
Ecotope is the main factor in the organization of phytocenosis, although it can be largely transformed by biotic influences of plants or disturbances. Abiotic factors influencing community organization include:
- climatic (light, heat, precipitation, air humidity, etc.);
- edaphic (granulometric and chemical composition, humidity, porosity, water regime and other properties of soils and soils);
- topographic (relief conditions).
- competitive relations;
- non-competitive environment formation (plants can affect the environment in different ways, through shading, desiccation, thickness bedding etc., and through it - on the composition and structure of the community). Among the plants stand out edificators that have a decisive influence on the organization of phytocenosis (for example, oak in the oak forest);
- allelopathy(plants act on each other with excreted substances);
- positive interactions (a little-studied form of interaction, manifested in the "mutual assistance" of plants);
- the influence of vines and epiphytes (can be manifested in the destruction of the bark, the "suffocation" of the prop plant, the formation of the environment in which the adventitious roots of the prop plant can develop by the products of the vital activity).
The influence on the organization of phytocenoses of heterotrophic components of biogeocenoses is extremely diverse. Influence animals manifests itself in pollination, eating, dispersal of seeds, changes in tree trunks and crowns and related characteristics, loosening of the soil, the appearance of pores, trampling, etc. Mycorrhizal mushrooms improve the supply of plants with mineral nutrients and water, increase resistance to pathogens. bacteria Nitrogen fixers increase the supply of nitrogen to plants. Other bacteria as well viruses may be pathogens.
Disturbances of both anthropogenic and natural genesis can completely transform the phytocenosis. This happens during fires, clearings, grazing, recreation and much more. In these cases, derivative phytocenoses are formed, which gradually change towards the restoration of the root one, if the impact of the disturbing agent has turned. If the impact is long-term (for example, during recreation), communities are formed that are adapted to exist at a given level of load. Human activities have led to the formation of phytocenoses that did not previously exist in nature (for example, communities on toxic dumps of industrial production).
Structural elements of phytocenosis
Phytocenosis consists of a number of structural elements. There are horizontal and vertical structure of phytocenosis. The vertical structure is represented tiers allocated 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, undergrowth layer, etc. The number of layers may vary. The evolution of phytocenoses goes in the direction of increasing the number of layers, as this leads to a weakening of competition between species. Therefore, in the older forests of the temperate zone of 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 that is somewhat different from the environment in the inter-canopy space), relief heterogeneities (which cause changes in the groundwater level, different exposure), species characteristics of some plants (reproducing vegetatively and forming monospecies "spots" , changes in the environment by one species and response to this by other species, allelopathic effects on surrounding plants), animal activities (for example, the formation of spots of ruderal vegetation on rodent burrows).
Regularly repeating spots (mosaics) in a phytocenosis, differing in the composition of species or their quantitative ratio, are called microgroups(Yaroshenko, 1961), and such a phytocenosis is mosaic.
Heterogeneity can also be random. In this case it is called variegation.
The main characteristics of phytocenosis
The main characteristics of a phytocenosis include the species composition of the plants that form it, diversity and abundance, ecological structure, and the spectrum of life forms.
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