Composition and structure of plant communities (synmorphology)
Phytocenosis, like any other plant object, can be considered as a system. According to L. Bertalanfii (Bertalanfii, 1956), a system is a complex of interacting elements. Any system can be characterized by its composition, i.e., the totality of all elements of the system, structure - the spatial relationship of the elements of the system to each other, and functional structure - the totality of connections that arise between the elements of the system. Therefore, considering phytocenosis as a complex system, in its organization one should distinguish between:
composition of phytocenoses;
The structure of phytocenoses (their spatial structure) - the distribution of aboveground and underground plant organs that make up the phytocenosis;
functional structure of phytocenoses - a set of relationships between elements of phytocenosis;
Composition of plant communitiesVegetation cover is a collection of plant individuals. But in nature it is impossible to find such a phytocenosis, which would be composed of absolutely identical plants. Almost any plant community consists of cenopopulations of different species belonging to different life forms and ecological groups that play different roles in nature. And within the same cenopopulation, individuals most often differ in age, degree of development or depression, and so on. Therefore, to characterize the composition of phytocenoses, such features as the floristic composition of phytocenoses, the composition of life forms, the population composition, the composition of ecomorphs, and the quantitative ratios of species in the phytocenosis are of primary importance. We have considered the last two characters in detail above when considering abiotic environmental factors (composition of ecomorphs) and when considering the specificity of species in terms of their impact on the environment (quantitative ratios of species in a phytocenosis). Therefore, below we will dwell in detail on the first three features that characterize the composition of phytocenoses.
Floral composition
Floral composition - it is the complete set of plant species found within a particular plant community. The floristic composition is the most important constitutional feature, which largely determines the structure and functions of the community. This is a very informative sign that speaks about the ecological conditions in which the community is located, about its history, the degree and nature of its disturbance, etc.
The floristic composition is characterized by a number of indicators. The first is species richness, that is, the total number of species characteristic of a phytocenosis. This indicator can vary from 1 (monodominant single-species communities) to 1000 or more species (some tropical forests). According to the witty remark of R. Margalef (Margalef, 1994), in any case, species richness can be located between two extreme situations: the Noah's Ark model - there are a lot of species, but each is represented by only one pair of individuals, and the "Petri dish" - microbiological culture , which represents a huge number of individuals of the same species. Species richness is the simplest measure of alpha diversity, that is, biotic diversity at the phytocoenosis level.
With all the interest in the indicator of the degree of species richness, it is obvious that its use in comparative analytical constructions is in many cases incorrect. So, for example, in terms of species richness, a small swamp and a patch of tropical forest are incomparable. Therefore, in geobotany it is much more often used species richness index is the number of species per unit area. But here it should be noted that in order to determine the species saturation of a phytocenosis, it is necessary in any case to know its species richness.
If species richness is identified using square or round areas inscribed into each other of increasing size, then, as a rule, with an increase in the area of the accounting unit, the number of species identified in the phytocenosis will increase. If we build a curve from the obtained values, then it will quite well reflect the dependence of the increase in the number of species on the size of the accounting area. As a rule, such a curve will initially rise sharply upwards, and then gradually pass to a plateau. The beginning of the transition to the plateau will show that the vast majority of species in the phytocenosis have already been identified on a site of this size. As a rule, the richer in species the phytocenosis, the smaller the size of the area at which the curve goes to the plateau.
Rice. 1. Curves "number of species / area" for desert (a), as well as for desert (b) and meadow (c) steppes; point * corresponds to the minimum range (Mirkin et al., 2002).
The area size at which the curve "breaks" (Fig. 1) occurs (although it should be noted that it is not clearly expressed in all cases) is called the minimum area (minimum area). Due to the strong correlation of floristic and physiognomic features of the phytocenosis, the area-minimum very often coincides in area with the cenoquant - a site of a homogeneous phytocenosis sufficient to, in addition to the species richness of the phytocenosis, statistically reliably estimate the projective cover of all species in it. Very similar in meaning to these two terms, but somewhat broader, is the concept of the detection area introduced by L. G. Ramensky.
Detection area - the size of the accounting area, on which all the essential features of the phytocenosis are revealed (the floristic composition of the phytocenosis, its structure and the quantitative ratio of species; in forest communities, in addition, the stock of timber and the distribution curve of trees by diameter classes).
The size of the counting area is a very important factor influencing the species richness of the phytocenosis. Thus, for example, on a small scale, alvar meadows found in Estonia and Sweden are characterized by the highest species richness.
These meadows are formed on shallow soils on carbonate rocks, so they are formed by small-sized plants, and even on such a small area as 1 dm 2 up to 40 different species can fit. In the Kursk steppes, V. V. Alekhin counted up to 100 species per 1 m 2. On a large scale (hundreds of square meters), tropical forests are the richest in species, where up to 2000 species of trees, vines and epiphytes can grow on an area of 400 m 2.
The factors that determine the species richness of a phytocenosis are numerous and interact in a complex way. That is why species richness is one of the most difficult to predict characteristics of phytocenosis. So, for example, M. Palmer (Palmer, 1994) gives 120 hypotheses explaining the species richness of phytocenosis.
Consider the main factors affecting the species richness of phytocenosis.
Flora, or pool of species. This is the set of species from which species can be selected to form a particular community. For natural and most semi-natural communities, this factor is decisive in the formation of communities. But, at the same time, ruderal communities that arise under conditions of intense and constant disturbance are relatively weakly affected by this fact, since they are based mainly on adventitious species with a wide range, sometimes even almost or completely cosmopolitan.
Opportunity for diasporas to enter. Following R. Sernander, any part of a plant that serves to spread it is called diaspora. The entry of diasporas depends, on the one hand, on the composition of the local flora. On the other hand, the possibility of diasporas entering is very strongly influenced by the probability of their introduction from other regions, which, in turn, depends on the activity of transfer agents and the absence of barriers to the entry of diasporas. This factor has a particularly strong effect on the species composition of isolated communities, such as, for example, alpine meadows or clearings remote from each other in a large forest massif. The intensity of diasporic entry into such communities is related to the number of seeds produced by different species, and, as a consequence, to the probability of their introduction into such an isolated habitat. At the same time, dominant species that form seeds in large numbers are more likely to form full-fledged populations than rare species with poor seed productivity.
Ecotop. This is the ecological volume of habitats, which is determined by the favorable conditions for the growth of plants that form a phytocenosis. As mentioned earlier, each species is ecologically individual and is characterized by a unique range of tolerance in relation to each ecological factor. This leads to the fact that a specific habitat can be inhabited only by those plant species whose tolerance ranges overlap with the boundaries of the conditions of a given ecotope. If the habitat is favorable, the soils are sufficiently moist, rich in mineral nutrients and have a neutral reaction of the environment, and the climate is mild, then such a habitat has a large ecological volume, that is, many species can potentially grow in one phytocenosis. In extreme conditions (desert, salt marsh, arctic desert, etc.), only a small number of patient species specially adapted to such conditions can potentially grow.
Variability of ecological environment regimes. In a number of cases, fluctuations in the environmental conditions of an ecotope are an important factor in the coexistence of species and an increase in species richness. At the same time, as a result of fluctuations, the range of ecological conditions of a particular ecotope greatly increases. The fact is that the processes of competitive exclusion in plant communities proceed rather slowly, which allows a large number of species to coexist in one place, which differ quite a lot in ecological niches. It should be noted that this is true mainly for short-term fluctuations, when species that find themselves in unfavorable conditions are oppressed, but have not yet been completely ousted from the community. Indirectly, the significance of this factor is confirmed by the fact that the variability of environmental factors is characteristic of many ecotopes with high species richness, for example, meadows and steppes.
Strategic spectrum of species. This is a factor that depends to a very large extent on the conditions of the habitat. If the conditions are severe and, consequently, the ecological volume of the habitat is small, then patients will prevail in the phytocenosis. If the environmental conditions are favorable, then the composition of the phytocenosis with a certain degree of probability may contain violet. In its presence, the species richness decreases sharply, since the powerful violet almost completely uses the resources of the environment. An example of this can be beech and spruce forests, reed beds in river floodplains, etc. If there is no violet, then ecological resources can be divided between different species due to the differentiation of their ecological niches. This leads to the fact that the species richness in such communities will be high. Such conditions are created, for example, in tropical rainforests, in steppes, in meadows with moderately dry, but fairly rich soils.
As the distance from the area of favorable environmental conditions to the area of their pessimal values, the number of species in phytocenoses decreases. Such a decrease is most pronounced where some species are able to absolutely dominate, as this limits the possibility of growth of other species. An example can be the results of observations in the alpine zone of the Eastern Carpathians, where thickets of powerfully developed alpine sorrel are formed in places where excrement accumulates (camps), where, in addition to it, only 1-2 species of higher plants grow. At the same time, under similar conditions, but on poor soil without accumulations of excrement, phytocenoses are formed with a predominance of white beetles, including more than 30 species.
Violation mode. A moderate disturbance regime can somewhat, and sometimes quite significantly, increase the species diversity of the community, but only if it prevents the strengthening of the role of violets. So, for example, the grass cover of a broad-leaved forest moderately visited by vacationers is richer in species compared to a protected forest, where most of the niche space is occupied by snotweed. The species composition of floodplain meadows used as hayfields is always much higher than that of unmowed meadows, where communities of several dominant species are formed, and the rest are forced out. But if the load of the disturbing factor is high, then the species richness of the phytocenosis will sharply decrease, and with the periodic action of the factor (plowing, the passage of machinery with violation of the vegetation cover, etc.), explerents will prevail, and with constant violation (intensive livestock grazing) - patients.
The possibility of coexistence of many plant species increases under the influence of excavating animals. Their activity leads to an increase in the heterogeneity of the environment. The formation of disturbed places with a sharply reduced intensity of competition provides the opportunity for the growth of species with low competitive ability, including annuals. The appearance of spots characterizing various stages of vegetation restoration after its disturbance provides the possibility of the formation of floristically richer phytocenoses. In a heterogeneous environment, individuals of certain species can be distributed over various microhabitats. At the same time, individuals of species within the same community may not interact with individuals of some other species, since they are confined to different microhabitats.
anthropogenic factor. Under the influence of man, the floristic composition of phytocenoses undergoes very strong changes, both towards an increase in species richness, and, much more often, towards its depletion.
Thus, a person often creates new phytocenoses by overseeding or replanting plants, often alien to the local flora. Potato fields in Belarus, forest plantations of North American conifers in Western Europe, New Zealand, etc. can serve as an example of this.
Often, a person deliberately introduces new species into existing phytocenoses, sometimes imported from other regions. An example of this would be overseeding Lupinus polyphyllus and Sarothamnusscoparius in our pine forests.
With the direct participation of man, there is often an accidental introduction of plants from other places, and these plants begin to successfully invade local phytocenoses. Thus brought to the territory of Belarus Acoruscalamus(Central Asia), Elodeacanadensis and Conyzacanadensis from America, etc.
Sometimes plants are first introduced into gardens and parks as ornamental or economically useful crops, from where they are successfully and often massively dispersed into local phytocenoses. An example of this in Belarus would be North American species: Amelanchierspicata, which is currently actively introduced into forest cenoses, and Echynocystislobata, often massively growing in floodplains.
Very often, diaspores of weeds enter natural phytocenoses from fields, which, as a rule, are capable of being transported over long distances by wind or water.
Often a person deliberately destroys plants that he considers undesirable, but the fight against weeds, as a rule, only leads to a reduction in the number of individuals of such species, and not to their complete exclusion from the composition of phytocenoses. The use of meadows as hayfields can cause the disappearance of species that reproduce exclusively by seeds, if the timing and frequency of mowing interfere with their seeding. Human impact on the ecotope (drying, irrigation, liming, fertilizing) leads to the restriction of the growth of some species and to the creation of favorable conditions for others. Of great importance in determining the floristic composition of phytocenoses is such a factor as grazing, especially intensive. This, as a rule, leads to a sharp reduction in the number of species, since very few of them are able to exist in such conditions.
Time (age of the community). Time is a universal factor that manifests itself in any community. However, the value of this factor can vary greatly during the formation of various phytocenoses, just as the time scale can be different. For example, in ruderal communities formed mainly by explerent species, species richness increases on a scale of months and years, while in natural climax communities it increases on a scale of geological time. An example is the species richness of analogous communities on serpentine soils in the mountains of North America, studied by R. Whittaker. These communities are located in areas that have and have not experienced glaciation. As it turned out, the species richness of communities in areas not affected by the glacier was 2 times higher than in similar communities, but formed in areas subjected to glaciation. This is primarily due to the fact that with an increase in the duration of the existence of a phytocenosis, the chances of a larger number of plant species entering the diaspores increase.
The idea of floristic completeness and incompleteness of phytocenoses. By floristically incomplete phytocenoses, he understood communities that do not include all plant species that can exist in them. Ramensky identified phytocenoses as absolutely full-membered, natively full-membered, practically full-membered and clearly incomplete. The completeness or incompleteness of phytocenoses can be accurately established only by conducting experiments with the oversowing of seeds of species that are not part of them. Absolutely full-fledged phytocenoses probably do not exist in nature, but it is impossible to verify this, since it would be necessary to carry out overseeding of all plant species capable of growing in the conditions of a given ecotope. The introduction of plants accidentally introduced by humans from other regions into phytocenoses, as well as the deliberate introduction of many species into natural communities (for example, multi-leaved lupine in pine forests) give reason to talk about the wide distribution of floristically incomplete phytocenoses.
At the same time, many long-established phytocenoses are native full members, that is, they include all types of local flora that can grow in these conditions. To reveal floristic incompleteness, long-term observations are necessary, since often individuals of a species that accidentally introduced or deliberately introduced by the experimenter exist only for 1-2 years, and then die, since the habitat in this phytocenosis is unfavorable for them. It is also necessary to take into account that some species under certain conditions are represented only by dormant individuals (viable seeds, dormant underground organs). The incompleteness established in relation to such species is, therefore, apparent (the so-called false incompleteness or hidden fullness of phytocenoses). Most often, it is a temporary phenomenon. In this case, resting individuals become active as soon as favorable conditions are created for this. This sometimes happens periodically or sporadically, and sometimes only with a continuous or local violation of the phytocenosis as a result of a strong deviation from the average meteorological and hydrological conditions, as well as with the mass reproduction of excavations.
Can be distinguished primary and secondary, or anthropologically conditioned incompleteness. The primary incompleteness of the phytocenosis occurs during its formation and is gradually eliminated as the community structure develops and becomes more complex. An example of anthropologically conditioned incompleteness can be incompleteness associated with the absence of seeding of some plant species that reproduce exclusively by seeds during the transition from single-cut to double-cut use of meadows. It should be noted that the absence of plant seeding can occur both without changes in ecotopic conditions (during haymaking) and when they change (for example, during grazing).
In addition to floristic, there is also the so-called phytocenotic incompleteness, that is, the state when some species are present in the phytocenosis in an amount less than the minimum possible to ensure their seed reproduction. So, for example, cross-pollinating plants can be in a phytocenosis in such a small number and located so rarely that the probability of their pollination will approach zero. As a rule, the phytocenotic incompleteness of phytocenoses turns into floristic after some time, since the coenopopulations of such plant species simply die out.
The floristic and phytocenotic incompleteness of phytocenoses can be of great practical importance. Thus, the absence in phytocenoses of species that can potentially be included in their composition (or if they are, but potentially can be in much greater numbers) and thereby increase their productivity or improve product quality, gives us the opportunity to introduce them into communities. An example would be the overseeding of legume seeds to improve meadows or lupine in pine forests. And vice versa, if in phytocenoses there are no plant species of little value or harmful from the human point of view that can grow in these conditions, then measures must be taken to prevent the introduction of such species into the community.
All of the above factors in the formation of species richness interact, which explains the complexity of predicting this characteristic of communities. Nevertheless, if we ignore the particulars and consider the general trends in the change in species diversity on a global scale, then we can talk about some the main gradient of diversity. R. Whittaker defined it as changes in communities from the high latitudes of the Arctic to the tropics on the plains and from the highlands to the plains. The most species-rich communities are tropical forests, savannahs, while the poorest communities are alpine and arctic desert communities.
It is clear that adjustments to the gradient on the plain must be made taking into account the continentality of the area, that is, its distance from the ocean and, accordingly, changes in the amount of precipitation and the nature of temperature changes in the annual cycle. Heat without moisture, as well as moisture without heat, cannot serve as a source of improving conditions and increasing the physical hyperspace of resources, and, consequently, of alpha diversity. For this reason, at low latitudes, if it is a desert, the alpha diversity will be low. A similar picture is observed in the mountains. The gradient of increasing species diversity will be observed only if in the area where the mountain system is located, the ratio of heat and moisture is optimal, that is, if it is an area of humid tropics or subtropics. If, say, a mountain system is located in a desert, then the change in species diversity will be described by a parabolic curve with a maximum in the middle part of the gradient. So, at first it will increase, that is, the desert will be replaced by a steppe or savannah, and only then it will decline. Thus, Whittaker's statements about the main gradient of diversity should be taken with caution.
Quite interesting is Whittaker's conclusion about the well-known independence of changes in the richness of communities with species belonging to different life forms. So, on a north-south gradient (that is, from the Arctic to the tropics), the number of tree species increases, but the number of grasses decreases. This just reflects the success of Raunkier's system of life forms and makes it possible to derive the so-called "normal spectra" of life forms of different variants of zonal vegetation.
The constitutional structure of phytocenoses
concept constitutional structure phytocenosis proposed by T.A. Rabotnov (1965), reflects its composition in a broad sense, including species, population, ecological and biological composition, composition of phytocoenotypes and coenogenetic groups, etc. The main features of the constitutional structure of phytocenoses are briefly considered below.
Species composition of phytocenoses
Each phytocenosis is characterized by a special species composition peculiar to it. The complexity or simplicity of it is determined by the indicator in species (floristic) saturation, which is understood as the number of species per unit area of a phytocenosis. The dependence of the value of this indicator on the accounting area is determined by the regression curve, which initially goes up sharply, and then becomes flatter (Fig. 12). The nature of such a curve indicates that in order to identify the species composition of a phytocenosis, the counting area should not be less than a certain threshold value (S), which very much depends on the size of the plants forming the cenosis. Therefore, when establishing the species composition of communities of different types, trial plots(registration areas) of unequal sizes, for example, forest phytocenoses are usually described on a trial plot of 0.25 hectares, grass - 100 sq.m, moss and lichen - 1 sq.m. m.
According to the value of the species saturation indicator, phytocenoses can be divided into three groups: a) floristically simple, consisting of a small number of species (up to one to two dozen), b) floristically complex, including many dozens of species, c) phytocenoses, occupying an intermediate position in terms of species saturation . However, when determining species saturation, only higher plants and macrophytic lichens are usually taken into account. If we take into account that the composition of phytocenoses also includes species of algae, fungi, bacteria, the number of which is usually several times greater than the number of higher plants, then it must be recognized that in nature, apparently, there are no floristically simple phytocenoses, as evidenced by the following table 3.
The species diversity of phytocenoses is influenced by a number of factors. A certain role in this regard is played by the general physiographic and historical conditions, on which the species richness of the flora of each particular region depends. And the richer the flora of the area, the more there will be candidate species that can settle in each specific phytocenosis. So, for example, the species saturation of phytocenoses of humid tropical forests, which are formed in conditions of exceptionally rich tropical flora, is estimated by hundreds of species of higher plants, and the species saturation of Siberian taiga forests, which are formed against the background of poor boreal flora, varies, as a rule, within 15-30 species. .
Table 3
Complete species composition of phytocenoses of the deserted steppes of Kazakhstan (Rabotnov, 1978)
| Numbers of phytocenoses | |||||||||
| plant groups | Number | % | Number | % | Number | % | Number | % | |
| Flowering | 12,5 | 10,5 | 10,5 | 12,0 | |||||
| mosses | 0,8 | 0,5 | |||||||
| Lichens | 4,6 | 6,0 | 9,0 | 7,0 | |||||
| Seaweed | 9,9 | 17,0 | 11,5 | 4,5 | |||||
| microscopic mushrooms | 32,3 | 34,5 | 34,0 | 39,0 | |||||
| Bacteria and actinomycetes | 39,9 | 32,0 | 34,5 | 38,0 | |||||
| Total | |||||||||
The floristic diversity of phytocenoses also depends on the habitat conditions: the more favorable they are, the more complex the species composition, and, conversely, floristically simple phytocenoses are formed in unfavorable habitats. For example, in the undisturbed phytocenoses of the meadow steppes of the European part of Russia, associated with moderately moistened fertile chernozem soils, there were (Alekhin, 1935) per 100 sq. m. up to 120 or more species of higher plants, while in the same areas along the banks of reservoirs with unfavorable highly waterlogged soils or on salt marshes, phytocenoses of 5-10 species of higher plants are formed.
Thus, the unfavorable factors of the ecotope exclude the possibility of many species growing in it and create the so-called ecotopic isolation phytocenosis, which in this case determines the simplicity of its composition. Therefore, M.V. Markov (1962) rightly considered the species richness of a phytocenosis as an indicator of the ecological capacity of a habitat.
In addition to ecotopic factors, the species diversity of phytocenoses is also influenced by coenotic conditions, which manifests itself, firstly, in the competitive exclusion of some plant species by others and, secondly, in the formation of a specific internal environment in communities that prevents the introduction of species adapted to a given environment into them. environment. So, for example, on the site of the destroyed dark coniferous forests of the taiga zone of the Western Siberian Plain, derivative birch forests are formed, which over time are replaced by birch with dark coniferous tree species. Together with it, some of its satellites disappear from the lower tiers and later on, they can not stand the significant shading created in dark coniferous forests by abundant coniferous litter, increased soil acidity. This phenomenon, named by A.K. Kurkin (1976) cenotic isolation phytocenoses, widespread in nature. At the same time, the ecotopic and coenotic aspects of isolation are interrelated with each other and jointly determine the general ecological the isolation of the phytocenosis and limit the capacity of its habitat.
Animals and humans can also influence the species diversity of phytocenoses. Thus, prolonged intensive grazing of domestic animals leads to a significant simplification of the species composition of the initially floristically rich meadow and steppe phytocenoses. A person sometimes deliberately destroys undesirable plants in phytocenoses and thereby simplifies their species composition. For example, this is done when clearing agrophytocenoses from weeds. In other cases, on the contrary, a person introduces new useful plants into the composition of natural phytocenoses, complicating the species composition. This is done when improving the composition of natural pastures by overseeding valuable fodder grasses. Most often, a person consciously or unconsciously influences the habitat, changing it and thereby causing a change in the species composition of phytocenoses: fertilizing meadows, draining swamps, irrigating natural phytocenoses of steppes and deserts.
In addition, the species diversity of a phytocenosis may depend on the mode of entry of plant primordia into its territory from outside, which is primarily determined by the landscape position of the phytocenosis. The more diverse and in greater quantities the primordia of plants enter the phytocenosis from the outside, the higher the probability that this phytocenosis will be floristically rich. And although this pattern is not always realized in nature, but the tendency of its manifestation is constantly preserved. Back in the early twenties, L.G. Ramensky (1971) drew attention to the fact that in natural phytocenoses there are by no means always viable rudiments of all those plant species that could grow in them. Considering this circumstance, he introduced the concepts floristic fullness and floristic incompleteness phytocenoses and proposed to distinguish between two similar categories of phytocenoses.
Floristically full members phytocenoses include all species capable of growing in them. It was later established (Rabotnov, 1978) that apparently, absolutely complete phytocenoses do not exist in nature, since in any case there will be species from other floristic regions that can grow in one or another particular phytocenosis. This is evidenced by the facts of the wide distribution and introduction into natural phytocenoses of species accidentally introduced by humans from other regions. Therefore, one can only assume the existence of native full-membered phytocenoses, which include all types of local flora that can grow in them. Such phytocenoses should be sought among resistant "ecological-phytocenotic closed"(Kurkin, 1976) communities.
Obviously not full members phytocenoses do not contain all types of local flora that can grow in them. When the rudiments arrive naturally or with the help of humans, these species take root in these phytocenoses. Apparently, most natural phytocenoses are floristically incomplete (Vasilevich, 1983), as evidenced, in particular, by the facts of the successful artificial introduction of useful plants into many natural phytocenoses.
In general, the question of the completeness or incompleteness of phytocenoses is not easily solved, since it is based on long-term observations of the fate of new species sown or replanted in order to verify the results of their establishment. At the same time, this issue is of great practical importance, since the presence of floristic incompleteness of phytocenoses is associated with the possibility of deliberately introducing plants useful to humans into natural phytocenoses, successfully controlling weeds, increasing the productivity of natural hayfields and pastures, and solving a number of other problems of rational use of vegetation.
These are the main factors that determine the species diversity of phytocenoses. In addition, there are some other reasons that affect species saturation, for example, a sharp variability of ecological regimes in a number of habitats, some ecological and biological features of species, etc.
cenopopulations
Each species in a phytocenosis is almost always represented by a more or less significant number of individuals, which together form cenopopulation. The concept of cenopopulation was developed in the forties and early fifties of TA. Rabotnov (1945, 1950a, etc.), and the term coenopopulation was introduced into geobotany later by V.V. Petrovsky (1960) and A.A. Korchagin (1964). In the future, the doctrine of cenopopulation was intensively developed by A.A. Uranov and his students, who published many interesting works, including the two-volume monograph "Cenopopulations of Plants" (1975, 1989).
To date, an idea has been formed about the cenopopulation as one of the main elements of the composition of the phytocenosis, and phytocenosis often defined as a system of coenopopulations associated with each other and with the environment. Each cenopopulation occupies its own ecological niche. When species grow together in a phytocenosis, the niches of coenopopulations partially overlap, but their centers are always differentiated (Mirkin and Rozenberg, 1978). Cenopopulations are a heterogeneous formation. It consists of individuals that differ in age, size, life condition, reaction to external influences, etc. It is believed that the internal differentiation of the coenopopulation is a stability factor. Due to the continuity of the vegetation cover and the weak discreteness of natural phytocenoses, coenopopulations of one species from neighboring phytocenoses turn out to be connected by gradual, continuum-like transitions and are not clearly delimited from each other (Mirkin, Rozenberg, 1983).
Ministry of Education and Science of the Russian Federation.
Volgograd State University.
Faculty of Management and Regional Economics.
Department of Economics and Nature Management.
Control work on geobotany
1 option
Volgograd 2006
1. Geobotany as a science, connection with other disciplines.
2. Main properties of phytocenoses.
2.1 Indicator properties of plants and phytocenoses
3. Classification of phytocenoses
Geobotany - the science of phytocenoses and the vegetation cover they make up. Geobotany is also called phytocenology. This science arose at the end of the 19th century. and is closely connected with plant geography as a branch of its ecological direction. The term "geobotany" was introduced by A. Grisebach in 1866, who used this term in a broad sense, including botanical geography. Geobotany is also called synecology. This name was adopted at the botanical congress in Brussels in 1910, it is used mainly abroad. There are two parts of plant ecology: autecology (ecology of individual species) and synecology (ecology of communities). In this sense, geobotany is only a part of ecology.
In Russia, it is generally accepted that, in addition to synecology, geobotany includes sections: the morphology of phytocenoses, the geography of phytocenoses, the dynamics of phytocenoses, and the classification of phytocenoses. Thus, geobotany studies the structure of phytocenoses; relationships between plants forming a phytocenosis; relationship between phytocenosis and environment; dynamics of phytocenoses; classification of phytocenoses; spatial distribution of phytocenoses and their combinations with other phytocenoses.
In the system of sciences, geobotany occupies a borderline position, being part of botany and part of geography, as it is part of the geographical science - biogeocenology. In addition to the general features of plant communities, geobotany studies the features of certain types of phytocenoses, therefore, such subdivisions as tundra science, marsh science, meadow science, forest science are distinguished.
Geobotanical knowledge is important in the practical activities of man. The exploitation and restoration of natural plant resources is based on knowledge of the laws of formation and reproduction of natural resources. Geobotany can substantiate the mode of logging, the mode of use of pastures and hayfields, etc. Geobotanical survey of lands makes it possible to draw conclusions about the degree of soil fertility, its acidity, water supply, salinity, etc., since plants and plant communities are indicators of habitat conditions. The role of geobotanists in the development of measures for the protection of nature is great.
The main task of geobotany is to determine the value of vegetation cover as the most important natural resource, fixing the current vegetation cover and its development trends on geobotanical maps, which make it possible to establish the potential of vegetation cover, use it correctly and transform it in the right direction. Land surveyors use geobotanical methods when choosing land for plowing, guided by the indicator properties of vegetation, and for drainage, when planning forestry, etc. Geobotanical knowledge is necessary when creating artificial phytocenoses, as well as when developing measures to improve natural phytocenoses, protected areas.
Geobotanists need to know the taxonomy and geography of plants. Plant geography studies the distribution of plants over the surface of the Earth and establishes the patterns of this distribution (plant chorology). The most important section of plant geography is the botanical geography of Russia and the world. The object of its study is the flora of the globe, i.e., the totality of plant species belonging to different systematic groups and confined to different types of habitats (i.e., included in different phytocenoses), but limited geographically - by confinement to a certain part earth's surface.
The area of distribution of a species is called its area. The boundaries of species ranges are ecologically and historically determined. The earliest ideas about the geographical differentiation of the flora of the Earth and the patterns of its distribution depending on the habitat conditions are in the writings of Theophrastus, who used the actual data collected during the campaigns of Alexander the Great. The history of modern plant geography begins much later. The great geographical discoveries, as well as the works of K. Linnaeus, I. G. Gmelin, P. S. Pallas, and others, were of great importance. materials of a long-term expedition to the countries of South and Central America. The works of A. Decandol (1855), A. Grisebach (1872), C. Darwin (1859) should also be noted. The historical principle, based on the evolutionary teachings of Charles Darwin, was introduced into the geography of plants by A. Engler.
The data of plant genetics and cytology are widely used in ecologo-geobotanical and chorological studies; N. I. Vavilov was the “pioneer” of such studies.
The range of a species unites all its specific locations, i.e., all points on the earth's surface where this species is found. The degree of population of the area by individuals of the species may be different. It depends on the confinement of the species to certain types of habitats. Areas completely inhabited by any species do not exist in nature. The species within its range is present only in its habitats.
The range of the species can be continuous and discontinuous (disjunctive). Criterion continuous range - the regular occurrence of a species in habitats corresponding to its nature. For example, species of the genus Nymphaea can only be observed in water bodies. If the species does not occur in large areas, then such an area intermittent. For example, common sour has two parts of its range: European-Siberian and Far Eastern. For a correct idea of the range of the species, a map is drawn up. In this case, a predominantly dot method is used, when each known locality of a species is plotted on a blank map in the form of a dot or a small circle.
The size and shape of the ranges are different. If the range covers almost the entire land surface, or is found in all parts of the world, then this is a cosmopolitan range, and the species is cosmopolitan. The phenomenon of cosmopolitanism is most often observed in aquatic plants, which is associated with a greater constancy of the conditions of the aquatic environment than the air environment (weeds, etc.). Widespread terrestrial plants are less common (bracken fern). Many species, on the contrary, have a narrow distribution (some bluebells, grains, etc.).
Plant species differ in their geographical origin. The formation of new plant species is carried out in a certain space inhabited by the ancestral form, which is original for this species. This is primary range of the species. Having arisen, the species settles (with biological progress) and increases its range. The rate of settling depends, in particular, on the ability to spread seeds, fruits, etc. The conditions that prevent the settling of plants are usually considered as barriers: topographic (seas, mountains), ecological and biological.
A special place in a number of factors of the distribution of the species belongs to human activity. This is an accidental or deliberate introduction (introduction) of plant species into some area in which they have never met.
With a decrease in the number and extinction of species, regressive changes in habitats are observed. Species found in a particular geographic area are called endemics. Endemism can be associated with the recent emergence of new species (neoendemism) and with the reduction of the range of a species as a result of regression and extinction (paleoendemic). For example, on the territory of Russia there are relics of the Tertiary age (yew, boxwood, albizia, etc.) in the humid subtropics of Transcaucasia.
Within their range, some species - occur - in fairly diverse habitats - eurytopic species with a wide ecological amplitude (pine, etc.). Species confined to a narrow set of habitats are called stenotopic(these include aquatic, marsh and other plants).
Each flora is a historically established set of species. Its composition reflects modern conditions and conditions of past eras. The commonality of certain species or genera indicates the commonality of the history of the development of the flora. Therefore, in the botanical and geographical analysis of the flora, geographical elements of flora, i.e., groups of species (genera) that are similar in distribution and origin. For example, in the forest zone of the European territory of the country, the following geographical elements of flora can be distinguished: arctic; arctoalpine (formed during the ice age); boreal (associated in their distribution with taiga forests); Atlantic (western); Siberian (eastern); Pontic (southern); nemoral (oak).
In the genetic analysis of the flora, the following are distinguished: autochthonous elements (species that have arisen within the space occupied by the flora) and allochthonous(alien species). Species that have recently appeared in the flora and brought from other places are called adventitious(advanced).
Flora species belong to different systematic groups (families, orders, genera). Each flora has its own systematic structure. In addition, any flora can be analyzed by the presence of ecological groups of species, phytocenotic and economic.
The use of wild plants as an indicator (indicator) of certain soil and climatic conditions has been used for a long time. Indicators of natural conditions can be both plant species and plant communities. Among plant species, species with a narrow ecological amplitude (stenobionts) serve as the best indicators. For example, stinging nettle indicates soils rich in nitrogen (with high abundance and viability). The Law of "Ecological Individuality of Plants" served as an impetus for a more systematic study of the ecology of species in connection with their confinement to certain habitats, which led to the creation of ecological scales.
The scientific direction that uses plants and vegetation to determine the ecological properties of habitats is called indicator geobotany. A great contribution to the development of indicator geobotany was made by the works of S.V. Viktorova, B.V. Vinogradova, E.A. Vostokova and others. Their works emphasize that the main directions of geobotanical indications are as follows:
Soil indication (pedo indication);
Rocks (lithoindication);
Underground waters (hydro indication);
permafrost (geocryological indication);
Salinity (halo indication);
Phytocenoses are also indicators of habitats, since they are confined to certain environmental conditions. Vegetation analysis is one of the objective means of soil indication.
Geobotanical indication of soils is used in all zones, but the degree of study of the indication properties of vegetation depends on the needs of agriculture. The most complete indicative properties of vegetation have been studied in the forest zone.
The vegetation cover is diverse, and therefore, in order to correctly take into account and use plant resources, it is necessary to bring all this diversity into a certain system, i.e. classify. A distinction should be made between the classification of flora and vegetation cover. The basis for the classification of flora was laid by the Swedish scientist Carl Linnaeus. He described about 1200 genera of plants, established more than 8000 species. For plant species, K. Linnaeus proposed double names (binary nomenclature) in Latin. In the name of a species, the first word (noun) denotes the genus, the second (adjective) denotes the species. For example, red clover (Trifoliumpratanse L.). The letter "L" means that the species was described by K. Linnaeus. Double names indicate the relationship between species, their origin from a common ancestor. Similar genera are grouped into families. So, the clover genus, together with the genera of alfalfa (Medicago), rank (Lathurus), peas (Pisum) and others, belongs to the legume family (Zeguminosae). Families are combined into orders, orders - into classes, classes - into departments (types).
The taxonomy of plants, created by K. Linnaeus, was largely artificial, since he did not take into account the relationship of species, which is explained by the little knowledge of vegetation at that time. Subsequently, scientists from different countries created a natural system of plants. Currently, to establish the relationship between species, not only the whole complex of ecological and morphological characteristics of plants is taken into account, but also their genotype, in particular, the set of chromosomes, is studied. The achievements of biochemistry (chemosystematics) are widely used. Related species, genera and families have a similar chemical composition. This is taken into account, in particular, when searching for medicinal plants.
The basic unit of land cover classification is the association. In 1910, at the Brussels Botanical Congress, the following definition of an association was adopted: “An association is a plant community of a certain floristic composition with special conditions of existence, a special physiognomy,” that is, an association is a type of phytocenosis. Phytocenosis is a specific concept, it is confined to a certain territory. Association as a type of phytocenosis is abstract. For example, the association "sorrel spruce forest" is characteristic of many areas of the southern taiga and coniferous-deciduous forests. All oxalis spruce forests are similar in terms of plant species dominating in their layers and synusia. The tiers of the forest stand are formed by spruce, the undergrowth consists of mountain ash, buckthorn, willows, etc.; in the grass-dwarf shrub cover, oxalis dominates, the brushing is weak, the moss of Schreber's pleurosis prevails.
The classification systems of vegetation in Russia are based on the principle of phytocenotic similarity, which is expressed in the presence of common dominants, edificators, and life forms in communities. When identifying units of a higher rank, the ecological and physiological proximity of edificators is taken into account.
In Russia, it is customary to distinguish the following taxonomic categories of vegetation: association, group of associations, formation, group of formations, class of formations, type of vegetation. Sometimes a taxon is also used - a class of associations and some others. The association includes phytocenoses with a homogeneous species composition, the same structure, confinement to similar habitat conditions. Associations are distinguished by the homogeneity of the species composition, but not by complete generality. Dominants and co-dominants should be common.
The group of associations includes all associations that differ in the composition of one of the tiers, while the main features of the other tiers, including the main tier, are identical: It includes associations of lingonberry-green-moss, blueberry-green-moss, sour-green-moss and pure green-moss spruce forests (without shrubs).
AT formation includes groups of associations characterized by common edificators. So, in the taiga forests, formations are distinguished: European and Siberian spruce, Scots pine, silver birch. Formation is the basic taxonomic unit of middle rank.
The group of formations includes such formations, the edificators of which belong to the same life form. Thus, formations of Siberian and European spruce, Siberian fir and other shade-tolerant coniferous trees form a group of dark coniferous forest formations. And the formations of light-loving coniferous trees (Scots pine, Siberian larch, etc.) make up the group of light-coniferous forest formations. Groups of formations with edificators similar in life form are combined into formation classes. Thus, groups of formations of dark coniferous and light coniferous forests combine coniferous forests into a class of formations. Groups of formations of small-leaved and broad-leaved forests of the temperate zone form a class of formations of deciduous forests with foliage falling in winter.
Formation classes are combined into a vegetation type. It is most correct to distinguish the type of vegetation according to morphological and ecological characteristics. Classes of formations coniferous and deciduous forests with foliage falling in winter are classified as forest types of vegetation (forests). The following main types of vegetation are distinguished: forest, swamp, meadow, steppe, floodplain.
The vegetation classification system considered above is subordinate, as it is represented by a number of taxa, successively subordinate to one another.
The name of the association is given in Russian and Latin according to the dominant types of vegetation layers in the community. For example, if pine dominates in the forest stand, heather dominates in the grass-shrub cover, and lichens dominate in the moss-lichen cover, then this association will be called heather-lichen pine forest. If the undergrowth is well expressed in the forest phytocenosis, then the dominant species of the undergrowth are also included in the name of the association - hazel-oxalis spruce forest.
Russian names of meadow associations can be given, therefore the same principle. At the same time, according to the decision of the botanical congress, the plant prevailing in the association is put in the last place in the name - the fragrant spikelet-meadow fescue association. The following method of naming associations is also used: dominants - belonging to the same tier, are connected with the “+” sign, and to different ones - with the “-” sign. For example, meadow foxtail + hedgehog team - fragrant spikelet. Popular names are used: boron, subor, etc.
The name of associations in Latin can consist of two words. For example, the spruce-sour forest association: Picetumoxalidosum. The name is formed from the root of the Latin name of the spruce edificator - Picea (to which the ending "etum" is added) and the root of the Latin name of the sub-edifier of sour - Oxalis (to which the ending "osum" is added).
There are many classifications according to the soil cover; when describing phytocenoses, especially complex ones, a strict subordination of units of various ranks is observed. The classification of phytocenoses is needed for studying, long-term monitoring, tracking the presence of successions, for practical purposes - to create maps of various vegetation areas. Before mapping, a classification of the vegetation cover is carried out, a survey of the vegetation that occurs.
1. Aleksandrova V.D. Vegetation classification. L.: Nauka, 1969
2. Bykov B.A. Introduction to phytocenology. Alma-Ata: Science, 1983
3. Vasilevich V.I. Essays on theoretical phytocenology L.: Nauka, 1983
4. Viktorov S.V., Vostokova E.A. Introduction to indicator geobotany. M.: Publishing House of Moscow State University, 1962
5. Soil science with the basics of geobotany, ed. L.P. Gruzdeva, A.A. Yasin. Moscow: Agropromizdat, 1981.
6. Shumilova M.V. Phytogeography. Tomsk: TGU Publishing House, 1989
41. Phytocenosis: variety of phytocenoses, structure of phytocenosis.
Phytocenosis (from the Greek φυτóν - "plant" and κοινός - "general") - a plant community that exists within the same habitat. It is characterized by the relative homogeneity of the species composition, a certain structure and system of relationships between plants with each other and with the external environment. According to N. Barkman, phytocenosis is a specific segment of vegetation in which internal floristic differences are less than differences with surrounding vegetation. The term was proposed by the Polish botanist I. K. Pachoski in 1915. Phytocenoses are the object of study of the science of phytocenology (geobotany).
Phytocenosis is a part of 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 circulation of matter and energy. Soil properties, microclimate, composition of the animal world, such characteristics of biogeocenosis as biomass, bioproductivity, etc. depend on vegetation. In turn, the elements of phytocenosis are plant cenopopulations - aggregates of individuals of the same species within the boundaries of phytocenosis.
Depending on the specifics of research in the concept of “biocenosis structure”, VV Mazing (1973) distinguishes three directions developed by him for phytocenoses.
1. Structure as a synonym for composition (species, constitutional). In this sense, they talk about species, population, biomorphological (composition of life forms) and other structures of the cenosis, meaning only one side of the cenosis - composition in the broad sense. In each case, a qualitative and quantitative analysis of the composition is carried out.
2. Structure, as a synonym for structure (spatial, or morphostructure). In any phytocenosis, plants are characterized by a certain 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). Understanding 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 cenotic level: the species composition, configuration and placement of structural elements in space are a condition for their functioning, that is, the 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 consists of a number of structural elements. There are horizontal and vertical structure of phytocenosis. The vertical structure is represented by tiers identified 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 called mosaic.
Heterogeneity can also be random. In this case, it is called variegation.
1. The structure of phytocenoses should be understood as:
a) the diversity of species in them and the ratio of abundance and biomass of all populations included in them;
b) the ratio of ecological groups of plants, which develops over a long time in certain climatic, soil and landscape conditions;
c) spatial mutual arrangement of plants (and their parts) in a plant community;
e) a + b + c.
2. The structure of phytocenoses is determined by:
a) the composition and quantitative ratio of the components of plant communities;
b) growing conditions of plants;
c) exposure to zoocomponents;
d) the form and intensity of human impact;
e) a + b + c;
e) All answers are correct.
3. The structure of phytocenosis gives an idea of:
a) the amount of media used by the community;
b) the features of the contact of its constituent plants with the environment;
c) the efficiency and completeness of the use of natural resources by the plant community;
e) All answers are correct.
4. The structure of phytocenosis depends on:
a) ecobiomorphic composition of the plant community;
b) the number and vital status of individuals of vascular plants belonging to the main forms of growth (trees, shrubs, shrubs, grasses);
c) the presence and quantitative participation of mosses and lichens, protists, algae and macromycetes;
d) height and closeness of aboveground shoots of community components;
e) all answers are correct
5. The most important features of the phytocenosis structure are:
a) the degree of closeness of the vegetation cover and the features of the vertical distribution of the leaf surface;
b) the presence of sufficiently differentiated stages or, conversely, their absence;
c) homogeneity or heterogeneity of the horizontal division;
e). a + b + c.
6. The vertical structure of phytocenoses has two polar variants connected by smooth transitions:
a) tiered;
b) phytocenotic horizons
c) vertical continuum;
7. The main factor determining the vertical distribution of plants is:
a) the amount of light that determines the temperature regime and humidity regime at different levels above the soil surface in the biogeocenosis;
b) tough competitive relations between various plant species and their consorts;
c) edaphic, or soil-ground, habitat conditions;
d) terrain
8. The universal synthetic characteristic of the vertical structure of any phytocenosis (both with tiers and with a vertical continuum) is:
a) inversion of vertical belts;
b) aggregation index;
c) leaf surface index;
d) index of homogeneity;
e) index of phytocenotic plasticity.
a) the ratio of the surface area of the leaves to the surface area of the soil on which they are located;
b) the ratio of the total area of leaves of a phytocenosis (or its layer) to the area of the territory it occupies, expressed in m 2 /m 2, or ha / ha;
c) the ratio of the total area of leaves of plants of different tiers;
d) the ratio of the surface area of the leaves of different plant species.
10. The smallest value of the leaf surface index is typical for:
a) meadow phytocenoses;
b) open desert communities;
c) spruce forests;
d) mixed forests
11. Ceteris paribus, the leaf area index in the meadows increases:
a) from less acidic to more acidic soils;
b) from more acidic to less acidic soils;
c) from the beginning of the growing season to the period of the culmination of the development of the herbage;
d) after each mowing and grazing;
e) when increasing the intensity of lighting and applying full mineral fertilizer (NPK)
f) b + c + d + e;
g) b + c + e;
h) a + c + e;
12. For the addition of the underground part of phytocenoses, a decrease in the mass of plant organs from top to bottom is characteristic. This is established for plant communities such as:
a) meadow;
b) steppe;
c) desert;
d) forest;
e) All answers are correct.
13. The mass of underground organs is usually several times (sometimes 10 or more) higher than the mass of above-ground organs in such communities as:
a) meadow;
b) semi-shrub;
c) tundra;
d) desert;
e) All answers are correct.
14. To the main cenoelements of phytocenoses according to Kh.Kh. Track (1970) include:
b) phytocenotic horizons;
c) price cells;
d) microgroups.
15. An element of the vertical structure of phytocenoses, which manifests itself when the community is formed by life forms of plants contrasting in height, is:
a) price element;
b) synusia;
d) cenotype;
e) phytocenotic horizon.
16. Tiers differ:
a) environmental conditions in the horizons to which the aboveground organs of the plants that form them are confined;
b) features of light and temperature regimes;
c) air humidity;
e). a + b + c + d.
17. There are several types of tiers (according to Rabotnov T.A.):
a) resistant to seasons and years (for example, layers of evergreen trees, shrubs, shrubs, mosses, lichens);
b) year-round existing, but sharply changing from the growing season to the non-growing season (layers formed by deciduous trees, shrubs, shrubs);
c) formed by herbs;
d) ephemeral, existing for a short time, formed by herbs (ephemers, ephemeroids), sometimes mosses;
e) are formed only in certain years, for example, a layer of annual grasses in those deserts where atmospheric precipitation falls in sufficient quantities only in some years;
f) re-forming during the growing season due to the alienation of above-ground organs as a result of mowing or grazing;
g). a + b + c + d.
18. Longline arrangement of plants:
a) allows species of different quality in their ecology to coexist in the community;
b) makes the habitat ecologically more capacious;
c) creates a large number of ecological niches, especially in relation to the light regime;
d) reduces competition and ensures the sustainability of the community;
e) All answers are correct.
19. In the series single-tier - two - low-tier - multi-tier - imperfect-tier (vertical-continuous) communities, the following is observed:
a) increase in floristic richness;
b) decrease in floristic richness;
c) a clear correlation between the number of layers and the number of species that make up the phytocenosis;
d) the absence of a certain pattern.
20. In the forests of the temperate zone, the following tiers are usually distinguished:
a) the first (upper) tier is formed by trees of the first size (pedunculate oak, heart-shaped linden, smooth elm, etc.)
b) the second - trees of the second size (rowan, apple, pear, bird cherry, etc.);
c) the third tier is undergrowth formed by shrubs (common hazel, brittle buckthorn, etc.)
d) the fourth tier consists of tall grasses (nettle, common gout) and shrubs (blueberries);
e) the fifth tier is composed of low grasses;
f) in the sixth tier - mosses and lichens;
g) All answers are correct.
21. The consistent use of the concept of tiering has a number of theoretical difficulties associated with the fact that:
a) not all phytocenoses are vertically discrete;
b) it is not clear whether the tiers are layers or “inserted” elements into each other;
c) it is not clear where to attribute the undergrowth, creepers, epiphytes;
e) All answers are correct.
22. There is no division into tiers in such types of phytocenoses as:
a) most herbal;
b) tropical rainforests;
c) certain types of deciduous forests;
d) a + b + c.
23. The absence (or weak expression) of layering in herbaceous communities can be explained by:
a) the presence of only one life form;
b) small height of plants;
c) the presence of predominantly perennial grasses;
d) approximately the same illumination of all plant individuals, regardless of their height and ecological characteristics.
24. There is no underground tiering:
a) in spruce forests;
b) in meadow phytocenoses;
c) on solonchaks and solonetzes;
d) in steppe and desert communities;
e) a + b + d;
g) All answers are correct.
25. Phytocoenotic horizon is:
a) a vertically isolated and vertically further undivided structural part of the biogeocenosis;
b) the vertical part of the plant community, characterized by a certain floristic composition and a certain composition of the organs of these plants;
c) artificial morphological division of the vegetation cover, in which (unlike tiered division 26. In the forests of the temperate zone, the following phytocenotic horizons are usually distinguished, formed:
a) crowns of trees;
b) the undercrown part of the trunks of tall trees, as well as trees of a smaller height, shrubs and corresponding consorts (for example, plants) are, as it were, cut vertically, forming horizontal layers;
d) all answers are correct.
lichens);
c) shrubs or grasses, which, in addition to grasses and shrubs, include the lower parts of tree trunks and shrubs with their characteristic epiphytes;
d) mosses, lichens, creeping plants, including the lower parts of taller plants and their seedlings;
e) All answers are correct.
27. When identifying phytocenotic horizons, such controversial issues that arise when delimiting tiers, such as:
a) how many tiers this or that phytocenosis includes;
b) at what closeness of the aboveground organs of the corresponding plant species should the layer be considered expressed or unexpressed;
c) where to place creepers, epiphytes, undergrowth;
d) all answers are correct.
28. Lianas and epiphytes are part of:
a) upper horizons;
b) lower horizons;
c) those horizons to which parts of trees and shrubs belong, serving as their support;
29. Each phytocenotic horizon is characterized by:
a) a certain floristic composition;
b) the composition of the organs of these plants;
c) the degree of occupancy of the space by these organs;
e) All answers are correct.
30. A section of vegetation cover, within which it is impossible to draw boundaries according to given characteristics and thresholds adopted to determine the boundary, is called:
a) parcel;
b) price cell;
c) microgrouping;
d) price quant;
e) price element.
a) one life form;
b) united by individual topical and trophic competitive relations;
c) one type;
d) different tiers.
32. The morphological severity of the cell of woody vegetation is determined by:
a) the age of the stand;
b) group placement of trees and stands;
c) the height of the forest stand and plants forming the undergrowth;
d) plant vitality.
33. The structural part of a phytocenosis, limited in space or time (occupying a certain ecological niche) and differing from other similar parts in morphological, floristic, ecological and phytocenotic terms, is called:
a) cenopopulation;
b) cenotype;
c) synusia;
d) price quant.
34. As sinusia can be considered:
a) each well-limited layer of forest phytocenoses;
b) a collection of epiphytes, creepers, epiphytic lichens;
c) spring forest ephemeroids;
d) groups of annuals that exist in deserts only in years with heavy precipitation;
e) All answers are correct.
35. Among temporary synusias there are:
a) seasonal;
b) daily allowance;
c) fluctuation;
d) demutational;
e) a + c + d;
f) a + b + c.
36. The most important signs of sinusia are the following:
a) synusia is formed by plants of one or more closely related life forms;
b) plants in synusia are close together, closed in underground or aboveground parts;
c) ecological similarity of plants included in one synusia;
d) morphological isolation, spatial expression;
e) certain interactions between plants, their impact on the environment and, as a result, the creation of their own eco-environment;
f) relative autonomy, expressed in the fact that synusias of the same type can exist with synusias of other types in different combinations;
g) a + c + e + e;
h) All answers are correct.
37. Synusia are:
a) a forest stand formed by spruce, pine or any other species;
b) blueberry or heather cover;
c) a spot of hairy sedge in an oak forest;
d) mixed stand of spruce and fir;
e) a tree stand formed by a mixture of oak, maple, ash;
f) a cover of ephemeroids in an oak forest;
g) lichen carpet of bushy forms in a pine forest;
h) a + b + d + g;
i) All answers are correct.
38. Synusia are characterized by the following functional features:
a) the plants that make up the synusia have a similarity in needs, coenotypic kinship, similarity in the transformation of the environment in a direction favorable for themselves and their partners;
b) in synusia there is a single coenotic process;
c) coenotic and ecological selections take place in the synusia;
d) all answers are correct.
39. An example of fluctuation sinusia can be:
a) a group of spring ephemeroids, well limited in time from synusia of herbs of summer vegetation, which differ from spring ones in their species composition, structure, ecologically and coenotypically.
b) thickets of willow-herb on burned areas and clearings, existing for a short time;
c) a group of annual grasses that occur in some deserts in years with a large amount of precipitation;
d) synusia of creeping ranunculus in water meadows with prolonged stagnation of spring floods.
40. Synusial analysis of phytocenoses is reduced to:
a) the establishment of synusia that make up the phytocenosis;
b) study of their species composition and structure;
c) study of the relationship between them and the environment;
e) a + b + c.
41. Synusial analysis of plant communities helps to determine:
a) environmental conditions of the habitat;
b) the completeness of the use of environmental resources by the phytocenosis;
c) the ecological niche occupied by each particular synusia;
d) a + b + c.
42. Most plant communities are characterized by heterogeneity of horizontal composition; this phenomenon is called:
a) discontinuity;
b) mosaic;
c) continuum;
d) emergence.
43. Within phytocenoses, special structural formations can be distinguished, called:
a) microgroups, or microphytocenoses;
b) price elements;
c) price quants;
d) price cells;
e) a + c + d;
e) All answers are correct.
44. The horizontal division of phytocenoses - mosaic - is expressed by the presence in the biocenosis of various microgroups that differ:
a) species composition;
b) the quantitative ratio of different species;
c) closeness;
d) productivity and other features and properties;
e) All answers are correct.
45. There are the following variants of mosaicity of phytocenoses (Rabotnov, 1984; Mirkin, 1985):
a) regeneration mosaics- heterogeneity of phytocenosis associated with the renewal process;
b) clone mosaics- heterogeneity of phytocenosis associated with vegetative propagation of plants;
in) phytoenvironmental mosaics- heterogeneity of phytocenosis associated with a change in the environment by one of the species and the response to this change of other species;
G) allelopathic mosaics due to the release of some plant species of strongly smelling aromatic substances;
e) zoogenic mosaics are formed as a result of the impact of animals;
f) a + b + c + d + e.
46. Irregularity in the distribution of plant species within a plant community and the resulting mosaic pattern is due to a number of reasons. By origin, the following types of mosaics are distinguished:
a) phytogenic, due to competition, changes in the phytoenvironment or characteristics of life forms of plants;
b) edaphotopic associated with the heterogeneity of the edaphotope (roughness of the microrelief, different drainage, heterogeneity of soils, etc.);
in) zoogenic caused by direct or indirect influence of animals (trampling, eating, deposition of excrement);
G) anthropogenic, the reason for which is human economic activity (grazing of farm animals, selective felling of trees in the forest, campfires, etc.)
e) exogenous, due to the action of abiotic environmental factors - the influence of wind, water, etc.
f) a + b + d;
g) All answers are correct.
47. Mosaic in the forest is least pronounced where:
a) the tree layer is formed by one species;
b) the tree layer is formed by species similar in their influence on the environment;
c) different ecobiomorphs (coniferous and softwood tree species) are represented in the tree layer;
d) shrubs are absent and poorly developed;
e) growing conditions for most species are unfavorable;
f) a + c + e;
g) a + b + d + e;
h) All answers are correct.
48. Mosaic is most pronounced:
a) in floodplain meadows;
b) in mixed coniferous-deciduous forests;
c) on raised bogs;
e) in coniferous forests.
49. The causes of phytogenic mosaicity in coniferous-deciduous forests, represented mainly by spruce and linden, can be the following:
a) lower illumination and temperature under spruce than under linden;
b) 2.0 - 2.5 times less precipitation in the form of rain penetrates under the crowns of spruce than under the crowns of deciduous trees;
c) rainwater flowing from the crowns of trees has a more acidic reaction than water flowing under a linden tree;
d) soil with a poorly developed humus horizon and a well-defined podzolic horizon is formed under the spruce;
e) a + b + e;
e). a + b + c + d.
50. Characteristic signs of mosaicity of many types of phytocenosis are:
a) stability in time and space;
b) dynamism;
c) change in time of some microgroups by others;
d) change due to the passage of the life cycle of plants;
e) b + c + d.
51. The English scientist Watt (Watt, 1947) distinguished the following phases of the age variability of plants and, accordingly, the variability of microgroups:
a) pioneer
b) invasive;
c) construction phase;
d) maturity;
e) degeneration;
f) a + c + d + e;
g) a + b + d + e.
52. There are the following types of horizontal addition of phytocenoses (according to A. P. Shennikov):
a) separate;
b) separate-group;
c) closed-group;
d) diffuse;
e) mosaic;
c) a + b + c + e;
g) a + b + c + d + e.
53. Mosaic phytocenosis, with all the diversity of composition and division into fragments, is combined:
a) the dominance of one from the tiers;
b) the absence of the dominance of any tier;
c) small sizes of mosaic elements mutually influencing each other;
d) significant sizes of mosaic elements.
54. In contrast to mosaic characterizing the intracenotic horizontal heterogeneity, complexity is the horizontal heterogeneity of the vegetation cover at the supraphytocenotic level. The complex is formed not from fragments, but from different phytocenoses, which:
a) occupy large areas;
b) are highly dependent on each other;
c) are less dependent on each other;
d) are not connected by a common tier;
e) mosaically alternate in space;
f) a + c + d + e;
g) a + b + d + e.
55. The transition zone between phytocenoses (contact phytocenosis) is called:
a) ecoid;
b) ecoclin;
c) ecotone;
d) ecotope.
56. Ecotone can be:
a) narrow or wide;
b) sharp or absent;
c) diffuse or bordered;
d) mosaic-island;
e) All answers are correct.
57. The absence of a pronounced transitional band between phytocenoses is most often due to:
a) a sharp change in growing conditions (for example, on a steep slope, in a clearly defined depression, etc.);
b) human impact (for example, a meadow clearing in the middle of a forest that arose at a clearing site);
c) environmental impact of dominant species in one of the adjacent phytocenoses (for example, spruce, sphagnum mosses, etc.);
e) a + b + c.
CHAPTER 5
Dynamics of phytocenoses.
1. Under the dynamics of phytocenoses and vegetation in general (syndynamics) is understood:
a) reversible changes in plant communities within a day, year and from year to year;
b) changes in phytocenoses with an increase in the age of edificators;
c) various options for gradual directed changes that can be caused by both internal and external factors and, as a rule, are irreversible;
d) long-term cyclical changes caused, for example, by regularly recurring forest fires;
e) a + b + d;
e) All answers are correct.
2. The main forms of vegetation dynamics are:
a) violations of phytocenoses;
b) succession of phytocenoses;
c) evolution of phytocenoses;
d) a + b + c.
3. There are the following types of variability of phytocenoses:
a) daily;
b) seasonal;
c) multi-year;
d) age;
e) all answers are correct
4. Unlike shifts, the variability of phytocenoses is characterized by the following features:
a) variability of floristic composition;
b) it takes place against the background of an unchanged floristic composition;
c) the observed changes are reversible;
d) irreversibility of changes;
e) the observed changes are non-directional;
f) a + d + e;
g) b + c + e.
5. Daily variability of phytocenoses appears only during the period:
a) vegetation;
b) the beginning of flowering;
c) flowering;
d) formation of seeds and fruits;
e) fruit ripening
6. During the day, such vital functions of plants change as:
a) photosynthesis;
b) intensity of absorption of water and mineral elements;
c) transpiration;
d) excretion of metabolites, which, in turn, leads to fluctuations in the composition of the air within phytocenoses (CO 2 content, specific emissions, etc.);
e) All answers are correct.
7. Seasonal variability of phytocenoses is due to changes during the year:
a) light and temperature regimes;
b) general climate;
c) hydrological regime;
d) phytoclimate;
e) all answers are correct
8. The stages of phenological development of phytocenoses differ from one another:
a) features of the biotope (phytoenvironment);
b) the intensity of growth and reproduction of plants;
c) the degree and methods of influence of some components on others;
d) features of the structure and floristic composition;
e) aspect (appearance) and economic use;
g) all answers are correct
9. Phenological spectra give an idea of:
a) floristic composition of the studied phytocenosis;
b) change in the participation of certain species in phytocenoses during the season or year;
c) composition of life forms;
d) the beginning and end of the growing season, as well as the duration of the growing season;
e) the timing of the onset and duration of individual phases of vegetation;
f) changes in the rhythm of seasonal vegetation depending on the characteristics of the environment in the studied cenoses;
g) All answers are correct.
10. Changes occurring in phytocenoses over years or periods of years, associated with unequal meteorological and hydrological conditions of individual years, are called:
a) succession;
b) transformation;
c) fluctuation;
d) demutation.
11. In accordance with the causes of occurrence, the following types of fluctuations are distinguished:
a) ecotopic, associated with differences in weather, hydro and other conditions of ecotopes from year to year;
b) anthropogenic, due to differences in the form and intensity of human impact on phytocenosis;
in) zoogenic, caused by differences in the effects of herbivorous and burrowing animals;
G) phytocyclic, associated with the peculiarities of the life cycle of certain plant species and (or) with their uneven seed or vegetative reproduction over the years;
e) All answers are correct.
12. Ecotopic fluctuations are the least pronounced:
a) in the forests;
b) in the meadows;
c) in the steppes;
d) in sphagnum bogs.
13. The most significant fluctuation changes are observed in adult individuals of herbaceous plants, which are manifested:
a) in the number and power of shoots;
b) in their vitality;
c) in the ratio of individuals in the generative and vegetative state;
d) a + b + c;
14. According to the degree of severity, fluctuations are divided into several types:
a) hidden;
b) oscillatory (oscillations);
c) cyclic;
d) digression-demutation;
e) all answers are correct
15. Latent fluctuations occur:
a) in monodominant grass cenoses;
b) in phytocenoses formed by species with perennial aboveground organs (woody plants, mosses, lichens);
c) in complex floristically rich multi-tiered forest communities
16. Oscillations are described for:
b) coniferous forests;
c) mixed forests;
17. Examples of oscillation can be:
a) change of dominants in some types of meadows in wet and dry years;
b) seasonal changes in the floristic and ecobiomorphic composition of phytocenoses;
c) fluctuations with alternating year-to-year changes at the level of subdominants;
d) seasonal dynamics of productivity
18. Digression-demutation fluctuations are characterized by:
a) the change of dominants and subdominants in floodplain meadows as a result of a sharp deviation from the average meteorological and hydrological conditions for these biogeocenoses;
b) changes in the ecobiomorphic composition of phytocenoses;
c) a strong violation of phytocenoses with their subsequent demutation - a return and a state close to the original, as soon as the cause that caused the change ceased to operate;
d) seasonal changes in the quantitative ratio of the components of phytocenoses
19. Factors causing digression of phytocenoses can be:
a) severe prolonged drought;
b) prolonged stagnation of water on the soil surface in spring;
c) the formation of a powerful ice crust;
d) severe winter with little snow;
e) mass reproduction of phytophages;
e) All answers are correct.
20. The most significant violations of phytocenoses occur if the adverse effects of meteorological and hydrological conditions, as well as zoocomponents:
a) is especially pronounced during the growing season of plants;
b) lasts no more than two years (seasons), as a result of which there is no strong oppression or mass extinction of dominant species;
c) continues in a row for several years or several seasons, which leads to mass extinction or severe suppression of the main components of phytocenoses;
d) lead to disruption of vegetative reproduction of plants of the lower tiers.
21. The duration of the demutation period is determined by:
a) the intensity of community disturbance;
b) the degree of conservation of plants that dominated before the disturbance;
c) growth conditions during the demutation period;
d) all answers are correct.
22. Examples of digression-demutation fluctuations can be:
a) the replacement of grass stands by creeping grass stands under the influence of spring stagnation of hollow waters, followed by the return of the predominance of grasses;
b) transformation into creeping cenoses with a predominance of various types of cereals;
c) the ability of individuals of many plant species under the influence of drought to go into a dormant state, and after the cessation of the drought - the possibility of a quick return of phytocenoses to their original state;
e) All answers are correct.
23. The practical significance of studying fluctuations in forage phytocenoses (meadow, steppe, etc.), aimed at their effective use and improvement, is determined by the fact that over the years:
a) their productivity and the quality of the feed obtained from them fluctuate;
b) the terms and even the possibility or expediency of using fodder lands change;
c) the effectiveness of methods for improving fodder lands is changing
(irrigation, fertilization, overseeding, etc.);
d) all answers are correct.
24. The primary productivity of biogeocenoses is the creation of organic matter:
a) autotrophic organisms (photosynthetic green plants);
b) heterotrophs (bacteria, fungi, animals);
c) all living organisms of the ecosystem
25. When studying biological products, it is necessary to determine the mass:
a) only living plants;
b) only living plants and litter;
c) living plants, litter, dead trunks of trees and shrubs - waste, as well as dead underground organs;
e) All answers are correct.
26. Biomass is:
a) expressed in mass, the amount of living matter per unit area or volume of habitat (g / m 2, kg / ha, g / m 3, etc.);
b) the increase in primary production per unit of space per unit of time (for example, g / m 2 per day);
c) the total mass of individuals of a species, group of species or community of organisms, expressed in units of mass of dry or wet matter, per unit area or volume of habitat (kg / ha, g / m 2, g / m 3)
27. Biomass of living matter in terrestrial ecosystems is represented by:
a) plants, animals, fungi and bacteria in approximately equal proportions;
b) predominantly animals and microorganisms;
c) more than 95% by plants.
28. The highest functional activity, i.e. the rate of increase in biomass per unit of time, is characteristic of:
a) marine phytoplankton;
b) a complex of plants of rivers and lakes;
c) vegetation of meadows, steppes, arable land;
d) woody vegetation.
29. Gross primary production (gross production) is the amount of organic matter:
a) remaining in plants after using part of it for respiration;
b) created by plants in the process of photosynthesis;
c) created by all living organisms that are part of a particular biocenosis.
30. Vegetation production is determined by:
a) temperature conditions and humidity;
b) provision of plants with elements of mineral nutrition;
c) the absence of limiting factors, such as salinity;
d) all answers are correct
31. Succession is called:
a) repeated variability of phytocenoses over years or periods of years;
b) seasonal variability of phytocenoses, due to sharp fluctuations in temperature during the growing season;
c) irreversible and directed, i.e., occurring in a certain direction, a change in the vegetation cover, manifested in the change of some phytocenoses by others
32. The main difference between the evolution of phytocenoses and their succession is:
a) in the course of evolution, the composition and structure of phytocenoses remain practically unchanged (the composition can even be simplified), and as a result of succession, new phytocenoses always arise;
b) in the course of evolution, new phytocenoses are formed, and in the case of succession, phytocenoses do not arise, but combinations of species that already existed in the area are formed;
c) succession is always a “repetition of the past”, and in the course of evolution new, previously absent combinations of plant populations arise.
33. The main differences between succession and fluctuations are:
a) the irreversibility of the changes;
b) continuity of succession;
c) direction of changes;
e) All answers are correct.
34. By origin, two main types of successions are distinguished:
a) permanent;
b) temporary;
c) primary;
d) fluctuation;
e) secondary.
35. Primary successions begin with the emergence of phytocenoses on:
a) rocks;
c) deposits of water streams;
d) cooled lava after a volcanic eruption;
e) glades in the forest;
f) a + c + d;
g) All answers are correct.
36. There are the following processes occurring in the case of primary succession:
a) the formation of a substrate;
b) plant migration, their engraftment and aggregation;
c) interaction of plants;
d) change by plants of the environment;
e) change of phytocenoses;
f) a + b + d + e;
g) All answers are correct.
37. Migration (distribution) of plants is carried out by transferring from one place to another:
a) seeds, spores and other germs;
b) whole plants;
c) vegetative organs of plants;
e) All answers are correct.
38. The survival of plants arising from germs brought from outside is possible if:
a) they find themselves in favorable ecotopic conditions;
b) seedlings develop with the homeostatic composition of consorts;
c) they have the ability to reproduce by seeds;
d) all answers are correct.
39. The period from the initial phases of successions to the achievement of a stable state of phytocenoses varies depending on:
a) climate;
b) initial substrate;
c) opportunities for diasporas to enter;
e) a + b + c.
40. Primary successions proceed faster:
a) warm, humid climates
b) in cold dry climatic regions;
c) on rocky ground;
d) on fine-grained substrates
41. Available data on primary succession rates suggest that (tick the correct answer):
a) in the Alps they pass in 100 years, in Japan - in 700 years, in the Arctic - in more than 7000 years, on poor quartz sand dunes along the coast of Lake Michigan (USA) - in about 5000 years;
b) in the Alps - for 100 years, in the USA (oak forests on the dunes of the coast of Michigan) - for 700 years, in Japan - for 1000 years, in the Arctic - for more than 5000 years;
c) in the Alps - for 100 years, in Japan - for 700 years, in the USA (on the dunes of the coast of Michigan) - for 1000 years, in the Arctic - for more than 5000 years;
42. Secondary successions differ significantly from primary ones in that they begin in conditions of already formed soil, which contains:
a) numerous microorganisms (bacteria, protists, fungi);
b) spores and seeds of plants, their resting underground organs;
c) soil mesofauna;
d) mineral and organic substances;
e) All answers are correct.
43. Secondary successions:
a) occur much faster (about 5-10 times) than the primary ones;
b) pass much more slowly than the primary ones;
c) in terms of the rate of origin, they practically do not differ from the primary ones.
44. For reasons of changes in biogeocenoses, the following types of successions are distinguished:
a) syngenetic (syngenesis);
b) autochthonous;
c) endoecogenetic (autogenous, or endodynamic);
d) exoecogenetic (allogenic, or exodynamic);
g) all answers are correct
45. Syngenesis is a process:
a) settlement by plants of places not yet covered with vegetation;
b) colonization of places by plants after the destruction of pre-existing vegetation;