Types of populations by age spectrum. Fundamentals of population ecology. The development of age-related diseases can be delayed

Basic concepts and terms : latent, pregenerative, generative and postgenerative periods of ontogenesis; age states of plants: seedlings, juvenile, mature, young vegetative, adult vegetative, young generative, middle-aged generative, subsenile and senile individuals; age spectrum; invasive and regressive coenopopulation.

When characterizing the age structure of populations in plants, one must keep in mind that the absolute age of a plant and its age state are different concepts.

Age state of a plant individual - this is the stage of individual development of a plant, at which it has certain environmental and physiological properties.

A large life cycle includes the stages of plant development from the formation of the seed embryo to death or the death of all its generations that arose from it vegetatively. In a large life cycle, ontogenetic periods and age states are distinguished (Table 5.1, Fig. 5.14).

Table 5.1.

Periods and age states in the life cycle of plants

Periods	Age conditions	Conditional designations
I. Latent	Seeds	S m
II. Before generation	Sprouts (ladder)
(virgin)	Juveniles
	imaturni individuals	I m
	Young vegetative individuals
	Adult vegetative individuals
III. Generative	Young generative individuals
	Medieval generative individuals
	Old generative individuals
	Subsenile individuals
Postgenerative	Senile individuals
(senile)

Rice.5.14. Age states of plant ontogenesis : A - meadow fescue (grass family), B -

Siberian cornflowers (Asteraceae family).

p- sprouts; j- juvenile plants;i m - imaturni;v- virgin;g 1 - young generative;g 2 - middle-aged generative;g 3 - old generative;ss - subsenile;s - senile plants.

In plants, there are four periods of individual ontogenesis:

1) latent- the period of primary dormancy, when the plant is in the form of seeds or fruits;

2) virginal or pregenerative - from seed germination to the formation of generative organs;

3) generative- period of plant propagation by seeds or spores;

4)senile or postgenerative - this is a period of sharp decline and loss of the ability to sexually reproduce, which ends with the complete death of plants.

Each period is characterized by corresponding age-related conditions. The duration of individual periods of individual development, the nature and time of transition from one age state to another is a biological feature of the plant species and its adaptation to environmental conditions in the process of evolution.

Seedscharacterized by relative rest, when metabolism in it is reduced to a minimum. Ladders have rudimentary roots and cotyledon leaves; they also feed on the reserve nutrients of the seeds and photosynthesis of the cotyledons.

Juvenileplants switch to self-feeding. Mostly they lack cotyledons, but the leaves are still atypical, smaller in size and of a different shape than those of adults.

imaturni plants show signs of transition from juvenile to adult. Their shoots begin to branch and typical leaves appear. Juvenile characteristics are gradually replaced by those typical for the plant species. This condition is long-term in some species.

Vegetativeindividuals (virginile) are characterized by the process of formation of a typical life form of plants with the corresponding typical characteristics of the morphological structure of underground organs and above-ground pagon system. Plants are finishing pregenerative period of its life cycle. Generative organs are still missing. At different stages of the formation of a typical vegetative sphere, young and adult vegetative individuals are distinguished, ready to enter the generative phase of development.

Generative individuals characterized by the transition to flowering and fruiting. Young generative individuals complete the formation of the typical structures of the species. Generative organs (flowers and inflorescences) appear in them, and their first flowering is observed.

Middle-aged generative individuals are marked by an annual maximum increase in the vegetative sphere due to the development of new enrichment shoots, abundant flowering and high seed productivity. Plants can remain in this state for different periods of time, depending on the life expectancy and biological characteristics of the species ontogenesis. This is one of the most important periods in the life of a plant, which attracts the attention of theoreticians and practitioners. The regulatory influence on cultivated forage and ornamental garden plants makes it possible to prolong their youth and increase the productivity of the former and the decorative qualities of others.

Old generative and individuals weaken the process shoot formation, sharply reduce seed productivity. The processes of death begin in them, which gradually prevail over the processes of formation of new pagon structures.

Senile individuals are distinguished by a clearly defined aging process. Small shoots with juvenile-type leaves appear. The plant dies over time.

The age distribution of individuals in a plant cenopopulation is called age spectrum. If the age spectrum of plants is represented by seeds and young individuals, such a cenopopulation is called Invasive.

More often than not, there is a young population that has just been introduced into the phytocenosis of a certain biogeocenosis.

There are normal and complete normal inferior cenopopulations.

Normal full-fledged coenopopulation represented by all age conditions and is capable of self-care by seeds or vegetative propagation.

Inferior normal coenopopulation called one in which there are no individuals of certain age conditions (ladder or, most often, senile individuals). These are plant populations

Monocarpics that bear fruit once in a lifetime. These are annual and biennial plants.

A detailed classification of plant populations was developed by T.A. Rabotnov (1946). Among plant populations within the phytocenosis, he distinguishes several types:

I. Invasive populations. Plants are just taking root in phytosenosis and do not complete the full development cycle.

This type has subtypes:

1) plants are found only in the form of a ladder, arising from introduced seeds from other populations;

2) plants are found in the form of seedlings, juveniles and vegetative individuals. For various reasons, they do not bear fruit and reproduce only by introducing seeds.

II. Normal type populations. Plants go through a full development cycle in a phytocenosis.

It has subtypes:

1) the plants are in optimal conditions. The population has a high percentage of generative individuals;

2) plants of this species are in average conditions and, accordingly, the population contains significantly fewer generative individuals;

3) the plants are not in very favorable conditions; there are few generative individuals in the population.

III. Populations of regressive type. The generative reproduction of plants in it has ceased.

This population type includes subtypes:

1) the plant blooms, produces seeds, but non-viable shoots grow from it; or the plant does not produce seeds at all. Therefore, in such populations there is no young juveniles;

2) the plant has completely lost the ability to flower and is only vegetating. Consequently, the population consists of old individuals.

This classification of plant populations makes it possible to determine their development prospects in a given ecosystem based on an analysis of the action of environmental factors.

Cenopopulations, which include only old subsenile and senile individuals, are not capable of self-care, are called regressive. They can exist due to the introduction of seeds or rudiments from other coenopopulations.

The age structure of coenopopulations is determined by such properties of the species as: frequency of fruiting, rate of transition from one age state to another, duration of each state, duration of a large life cycle, ability for vegetative reproduction and formation of clones, resistance to diseases and adverse natural conditions, etc.

In the case when a cenopopulation is characterized by high seed productivity and mass emergence of seedlings with significant death of young individuals and the rapid transition of those that remain into a vegetative and generative state, its age spectrum has a left-handed character. This is the spectrum of young coenopopulations (Fig. 5.15).

Rice.5.15. Age spectra of coenopopulations:

A - left-sided spectrum of Colchicum lush;

B - right-hand spectrum of the Meadow fire;

1, 2 - variability over the years.

If seed productivity is low, there are few young individuals, and the accumulation of adult individuals occurs due to the significant duration of their age states and during the formation of a clone, the cenopopulation spectrum will have a right-handed character. It is a sign of her aging.

The age spectrum of the cenopopulation and its size determine the role of the species in the phytocenosis.

Counting units. Calculations of age (ontogenetic) spectra in plants are based on the identification and use of counting units.

The issue of identifying a counting unit is quite complicated due to the ability of plants as modular organisms to form vegetative structures (partial bushes and shoots, tubers, bulbs, adventitious buds on roots, etc.) within a physically integral individual, capable of independent existence and development and protruding as units of impact on the environment. In plant population studies, two counting units are used. The first unit is morphological; when identifying such units, the main feature is the physical integrity of the analyzed structure, i.e. individuals. This approach is quite legitimate and appropriate if the researcher is dealing with a single-trunk tree, compact bush, bulbous plant, etc.

When the object of study is a physically integral system of root shoots, for example, aspen, consisting of mature, young trees and shoots that have just begun to develop, it is physically impossible and impractical to distinguish morphological units from the point of view of analyzing the age and spatial structure of populations. In this regard, the idea of ​​a second - phytocenotic - counting unit was formed.

Counting units differ significantly in plants of monocentric, clearly polycentric and implicitly polycentric biomorphs, identified on the basis of the characteristics of the spatial distribution of shoots, renewal buds and roots (Smirnova, 1987).

Adult individuals of monocentric biomorphs are characterized by the fact that roots, shoots (shoots) and renewal buds are concentrated in a single center, which is the center of growth of the individual and the center of influence on the environment. Adult individuals of clearly polycentric biomorphs have several clearly defined centers of growth of the individual, which represent a relatively autonomous part of the individual. Such centers can be partial bushes, and in the absence of branching (tillering), partial shoots. Adult individuals of implicitly polycentric biomorphs, as in the previous type, have several growth centers (Smirnova, 1987), however, during plant ontogenesis these centers appear so close that it is practically difficult to distinguish between them. In this regard, an implicitly polycentric individual is conventionally considered as a single center of influence on the environment.

Types of ontogenetic (age) spectra of populations. The most easily determined sign of a stable state of a population is a complete ontogenetic spectrum, in which the numerical ratio of individuals of different ontogenetic groups is determined by the biological properties of the species: 1) the total duration of ontogenesis and individual states; 2) the rate of development of individuals in different states; 3) a method of self-sustaining populations: deeply rejuvenated diasporas (seeds and vegetative rudiments), shallowly rejuvenated vegetative individuals, or various combinations of the above methods; 4) the intensity and frequency of inspermation and elimination of individuals, 5) the ability to create a soil reserve of seeds, 6) the size of the area of ​​resource absorption by individuals of different ontogenetic states (synonym - feeding area). Such spectra are called basic (characteristic); they characterize the definitive (dynamically stable) state of populations (Cenopopulations..., 1988).

The types of basic spectra are distinguished by the position of the absolute maximum in the spectrum of ontogenetic states. Within each type, depending on the method of self-maintenance of the population, variants are distinguished.

Specific spectra of populations can show either great similarity to the basic spectra or significantly differ from them. The variety of specific spectra can be combined into several types, corresponding to a particular state (or life stage) of the population:

Invasive state - only pregenerative (sometimes young generative) plants are represented in the spectrum;

Normal condition:

A) a full spectrum, in which all or almost all ontogenetic groups of plants (of seed and/or vegetative origin) are represented; can be left-sided, single-vertex (with a maximum on generative plants) and right-sided;

B) vegetative-full spectrum, where plants of only vegetative origin are represented;

B) discontinuous spectrum, where most of the ontogenetic groups are represented;

Regressive state - the population consists only of post-generative plants;

A condition in which only a few (often one) ontogenetic groups are represented - a fragmented spectrum.

Invasive populations are in their infancy and, depending on the ontogenetic composition and number of individuals, on the one hand, and ecological and cenotic conditions, on the other, have more or less likely prospects for development into normal ones. The latter are fully capable of spontaneous self-maintenance by seed and/or vegetative means. The absence of individual ontogenetic groups in the spectrum of normal populations may be associated with the periodicity of fruiting and, as a rule, is not evidence of an unstable state of the species in the community.

Populations become regressive when older plants stop bearing fruit or community conditions prevent the development of young growth. In addition to the listed options, in disturbed forest communities, populations can be represented by individual individuals of certain age conditions (population fragments). This usually indicates the episodic establishment of a species at an extremely low level of abundance, and is typical for populations of insecticide species. The prospects for the development of such populations are very difficult to assess. Diagnostics of the state of populations, based on the above characteristics, makes it possible to predict the further development of coenopopulations, and also allows one to approach the assessment of the successional state of the community. At the same time, to adequately assess the prospects of the population, it is necessary to take into account the biological and ecological characteristics of the species.

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INTRODUCTION

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MATERIALS AND METHODS OF RESEARCH

To study the state of coenopopulations F. ruthenica Test plots measuring 1x1 m were laid out. At each trial plot, the total number of individuals per 1 m 2 was taken into account. U F. ruthenica The following biometric indicators were measured: height, number of lower, middle and upper leaves, number of flowers, length of tepals. When analyzing these indicators, the age states of individuals were determined and ontogenetic spectra were compiled. When determining the age structure of the population, individuals of seed and vegetative origin were taken as the accounting unit. Age conditions were determined according to the Works of M.G. Vakhromeeva, S.V. Nikitina, L.V. Denisova, I. Yu. Parnikoza. Recovery, age and efficiency indices were determined according to the method of A.A. Uranova. The recovery index shows how many descendants there are per generative individual at a given moment. The age index evaluates the ontogenetic level of CP at a specific point in time; it varies in the range of 0-1. The higher its indicator, the older the CPU under study. The efficiency index, or average energy efficiency, is the energy load on the environment, called the "average" plant. It also varies from 0 to 1, and the higher it is, the older the age group of the “average” plant.

1

The purpose of the research was to study the spatial structure and age spectra of Medicago L. cenopopulations in the ravine-gully complexes of the south of the Central Russian Upland. The landscape and climatic conditions of the ecotopes of gully-gully complexes with chalk outcrops create conditions for the introduction of new synanthropic species, such as species of the genus Medicago. Most of the alfalfa cenopopulations identified under these conditions are complete and have a continuous (continuous) distribution of individuals across age groups, which indicates the stability of the adaptive microevolutionary changes occurring in them. The identified adaptation processes in local cenopopulations of alfalfa are aimed at preserving individuals with morphological, biochemical and other properties similar to those of endemic calciphyllous vegetation. The formation of cenopopulations of a certain “carbonate” ecotype occurs, close to cultural forms in a number of morphological characteristics, and at the same time possessing a pronounced type of competitive-stress-tolerant adaptive strategy. In this regard, the observed adaptive microevolutionary processes in phytocenoses on carbonate soils allow us to consider the Cretaceous south of the Central Russian Upland as a secondary anthropogenic microgenetic center for the formation of M. varia. From a practical point of view, it is possible to effectively select leguminous grass individuals to create highly productive competitive and environmentally sustainable coenopopulations on carbonate soils.

coenopopulations

age spectrum

vitality

spatial structure

carbonate soils

gully-beam complexes

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4. Dumacheva E.V., Chernyavskikh V.I. Population analysis of species of the genus Medicago in natural plant communities of the south of the Central Russian Upland // Problems of general botany - traditions and prospects: Coll. Proceedings of the Internet conference / Rep. editor Izotova E.D. – Federal State Autonomous Educational Institution of Higher Professional Education “Kazan (Volga Region) Federal University, November 10–12, 2011. – Kazan, 2011. – P. 82-84.

5. Dumacheva E.V., Chernyavskikh V.I. The influence of the method of cultivating hybrid alfalfa on the seed productivity of the first generation offspring on carbonate soils of the Central Chernobyl region // Kormoproizvodstvo. – 2014. – No. 2. – P. 23-26.

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8. Kotlyarova E.G., Chernyavskikh V.I., Tokhtar V.K. and others. Dynamics of vegetation cover of agricultural landscapes of model territories of the Krasnogvardeisky station of the Belgorod region // Modern problems of science and education. – 2013. – No. 3; URL: www.site/109-9427

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Introduction

The most important complex characteristics that make it possible to assess the hereditary adaptive potential and competitiveness of cenopopulations in interaction with environmental conditions are their age spectrum and spatial structure. Ontogenetic spectra of populations obtained as a result of long-term observations reflect the dynamic processes occurring in the “soil - plant - community” system when interacting with the ecotope, the course of renewal and death of individuals, indicate the rate of generational change, succession processes, etc. .

The most common species cultivated in the south of the Central Russian Upland are: alfalfa, or blue ( M. sativa, 2n = 32), alfalfa variable or medium ( M.varia(or M. media Pers.), 2n = 32) and yellow or crescent alfalfa ( M. falcata, 2n = 32). In this regard, it is the populations Medicago, distributed on carbonate soils in natural communities, are of greatest interest as an object of environmental research and a possible material for creating productive varieties that are resistant to heavily eroded carbonate soils and chalk outcrops in the region.

Purpose research was the study of the spatial structure and age spectra of cenopopulations Medicago L. in gully-gully complexes in the south of the Central Russian Upland.

Objects and methods of research

The methodological basis for the research was the doctrine of the centers of origin and diversity of cultivated plants. Geobotanical research was carried out on the territory of the Belgorod region (2002-2013). To assess the ecological status of blue-hybrid alfalfa M. varia in the conditions of gully-beam complexes with chalk outcrops, stationary reference points were identified, the local cenopopulations of which were considered as model ones:

1) Plyushchevka tract, chalk outcrops, x. Evdokimov, Volokonovsky district;

2) outcrop, lower slope part, border with steppe communities, chalk eluvium fan, village. Verkhnie Lubyanka, Volokonovsky district;

3) Belaya Gora tract, chalk outcrop, lower slope part, chalk eluvium fan, village. Vatutino, Valuysky district;

4) outcrop, chalk eluvium fan, p. Varvarovka, Alekseevsky district;

5) chalk outcrops, chalk eluvium fans, p. Salovka, Veidelevsky district;

6) Kogai Yar, chalk outcrops, chalk eluvium fan, village. Bogorodskoye, Novooskolsky district.

We studied the area of ​​cenopopulations (m2), the absolute number of individuals (pcs.), specimen saturation (density) (pcs./m2), and the age spectrum of local cenopopulations. Observations, records and data processing were carried out according to standard methods.

Results and its discussion

In plant communities of chalk outcrops of the Belgorod region, cenopopulations M.varia clearly confined to habitats associated with human economic activity: they grow in ravine-beam complexes near fields previously used in the system of soil protection and farm crop rotations. In these fields, until the early 90s of the last century, perennial grasses were most often grown, occupying 50% or more of the crop rotation structure.

Formation and further development of coenopopulations M.varia in the contrasting conditions of ravine-gully complexes can be explained by the fact that these ecotopes are similar to the foothills with the distribution of gravelly soils, where cultivated alfalfa originates (for example, the Central Asian region, the North Caucasus, the Mediterranean), but with the specific carbonate content of the soils of the eroded landscapes of the region.

It is noteworthy that in the geobotanical descriptions made in the area of ​​our research V.I. Taliev 100 years ago, blue-hybrid alfalfa was never mentioned on chalk outcrops. This may indicate a relatively recent widespread distribution of this species in the region. Currently, as our research has shown, M. varia found in plant communities of steppe, meadow and calciphylle erosional landscapes.

For cenopopulations M. varia in difficult environmental conditions, the determining factor is the combination of resources at a specific point in the ecotope. In the gully-beam complexes, microrelief is well defined, influencing the spatial distribution of species. Cenopopulations of blue-hybrid alfalfa are concentrated at the mouths of ravines with alluvial fans and in alluvial fans of active ravines, i.e. in more humid habitat conditions, on gravelly soils. Spatial structure of coenopopulations Mvaria experiments at stationary points in gully-beam complexes of the Belgorod region are presented in Table 1.

Table 1. Spatial structure of cenopopulations M. varia
in reference stationary points (2008-2013)

Stationary point	Area, m2	Abs. number of individuals, pcs.	Instance saturation (density), pcs./m2
X. Evdokimov, Volokonovsky district
With. Verkhnie Lubyanka, Volokonovsky district
With. Vatutino, Valuysky district
With. Varvarovka, Alekseevsky district
With. Salovka, Veydelevsky district
With. Bogorodskoye, Novooskolsky district
Average

Note: Cv is the coefficient of variation.

The area of ​​the studied cenopopulations varied widely - from 200 m2 to 8000 m2 and averaged 1983.3 m2 (Cv = 153.7%). The largest cenopopulations by area were found near x. Evdokimov Volokonovsky district and village. Varvarovka, Alekseevsky district. All habitats are characterized by a random group arrangement of alfalfa individuals. The size of the groups varied, but aggregations of 10-30 individuals were most often observed. Single specimens were rare. The number of individuals in cenopopulations averaged 226.3, and this indicator varied within fairly narrow limits (Cv = 11.8%), which indicated its homogeneity and evenness. The largest population was found near the village. Salovka, Veidelevsky district.

The cenopopulation near the village was characterized by maximum density. Verkhnie Lubyanka of the Volokonovsky district, which had the smallest total area. On average, the specimen saturation of alfalfa was 0.5 pieces. / m 2 with a high level of variability of the indicator (Cv = 81.4%).

To study the influence of ecological-coenotic factors on the age spectrum, the ontogenetic states of individuals of local cenopopulations of alfalfa were analyzed. The immature and virginal states of individuals were considered as one group of vegetative plants.

The predominance of plants of a certain age category in the spectrum makes it possible to characterize the stability of cenopopulations in given ecological and cenotic conditions. Each age state has its own morphological and physiological-biochemical characteristics, which affect the relationship of individuals with the ecological and phytocenotic environment. Under optimal growing conditions, coenopopulations are characterized by a normal statistical distribution of the ratios of individuals of different ages.

The analysis made it possible to identify the peculiarities of the influence of conditions on the ontogenetic spectrum of the studied cenopopulations. The four studied cenopopulations were complete and had a continuous (continuous) distribution of individuals across age groups. Two were discrete: in the cenopopulation from the village. Vatutino there were no senile ones, and in the cenopopulation from the village. Salovka - seedlings and juveniles.

A bimodal ontogenetic spectrum with two peaks: the first in the pregenerative, the second closer to the senile part of the spectrum was identified in a coenopopulation from x. Evdokimov. In this habitat, 33.4% of individuals were in a pregenerative state, 23.7% were old generative and 17.1% were subsenile. This ratio indicates an active process of self-renewal, as well as the stability of this local coenopopulation over time.

Cenopopulations in which generative plants predominate, and the proportion of individuals in all other states is approximately balanced, are considered normal. In our studies, these were cenopopulations of variable alfalfa from the village. Verkhnie Lubyanka and village. Vatutino and s. Bogorodskoe. In these coenopopulations, generative plants predominated (g 1, g 2, g 3), which accounted for 67.1; 67.2; 73.3% respectively. The subsenile and cyanotic state of individuals in these coenopopulations was weakly expressed. The centered spectrum of coenopopulations indicates their stable status in the community.

The right-sided ontogenetic spectrum, indicating a weakening of the renewal process, was identified in our studies in coenopopulations from the village. Varvarovka and village Salovka. In these habitats, groups of individuals in a senile state predominated - 39.4% and 38.5%, respectively. In the cenopopulation from the village. Salovka, the proportion of individuals in the pregenerative state (p, j, V) was 7.3%, and in the cenopopulation from. Bogorodskoye, 2.1% of vegetative plants were found in the complete absence of individuals of age p, j. Observations of these local coenopopulations for three years indicate their instability and gradual loss from phytocenoses.

Reproductive effort is considered in modern phytocenology as one of the most informative and complex genetically determined indicators, which determines the dependence of the level of the production process both on the state of individuals in coenopopulations and on the ecological and cenotic situation.

High seed productivity and, accordingly, reproductive effort were revealed in individuals of cenopopulations x. Evdokimov and S. Vatutino. Cenopopulation s. Verkhnie Lubyanka tended to increase the productivity of the total phytomass due to an increase in the power of development of the root system, which was reflected in the magnitude of the reproductive effort towards its reduction (Table 2).

Table 2. Indicators of general productivity and reproductive effort of alfalfa individuals at reference stationary points (2008-2013)

Stationary point	Aboveground phytomass of individuals, g abs. dry in-va	Total phytomass of individuals, g abs. dry in-va	Number of seeds, pcs./1 plant.	Reproductive effort, %
X. Evdokimov, Volokonovsky district
With. Verkhnie Lubyanka, Volokonovsky district
With. Vatutino, Valuysky district
With. Varvarovka, Alekseevsky district
With. Salovka, Veydelevsky district
With. Bogorodskoye, Novooskolsky district
Average

In individuals of coenopopulations with. Varvarovka, village Salovka and village Bogorodskoe revealed a general trend towards a decrease in the above-ground phytomass, seed productivity and, as a consequence, reproductive effort.

Conclusion

The landscape and climatic conditions of the ecotopes of gully-gully complexes with chalk outcrops form the conditions for the introduction of new synanthropic species, such as species of the genus Medicago. They are not only one of the most valuable economically, but also in most cases determine the value of the biological capacity of eroded agricultural landscapes.

Most of the alfalfa cenopopulations identified under these conditions are complete and have a continuous (continuous) distribution of individuals across age groups, which indicates the stability of the adaptive microevolutionary changes occurring in them. The identified adaptation processes in local cenopopulations of alfalfa are aimed at preserving individuals with morphological, biochemical and other properties similar to those of endemic calciphyllous vegetation. The formation of cenopopulations of a certain “carbonate” ecotype occurs, close to cultural forms in a number of morphological characteristics, and at the same time possessing a pronounced type of competitive-stress-tolerant adaptive strategy.

In this regard, the observed adaptive microevolutionary processes in phytocenoses on carbonate soils allow us to consider the Cretaceous south of the Central Russian Upland as a secondary anthropogenic microgenic center of morphogenesis M. varia. From a practical point of view, it is possible to effectively select leguminous grass individuals to create highly productive competitive and environmentally sustainable coenopopulations on carbonate soils.

Reviewers:

Sorokopudov V.N., Doctor of Agricultural Sciences, Professor of the Belgorod State National Research University, Belgorod.

Sorokopudova O.A., Doctor of Agricultural Sciences, Professor, Professor of the Faculty of Biology and Chemistry of the Belgorod State National Research University, Belgorod.

Bibliographic link

Dumacheva E.V., Chernyavskikh V.I. SPATIAL STRUCTURE AND AGE SPECTRUM OF MEDICAGO L. CENOPOPULATIONS IN GULISH-BULK COMPLEXES OF THE SOUTH OF THE CENTRAL RUSSIAN UPLANDS // Modern problems of science and education. – 2014. – No. 4.;
URL: http://science-education.ru/ru/article/view?id=13868 (access date: 02/01/2020). We bring to your attention magazines published by the publishing house "Academy of Natural Sciences"

With age, an individual's requirements for the environment and resistance to its individual factors naturally and very significantly change. At different stages of ontogenesis, changes in habitats, changes in the type of food, the nature of movement, and the general activity of organisms can occur. Often, age-related ecological differences within a species are expressed to a much greater extent than differences between species. Grass frogs on land and their tadpoles in water bodies, caterpillars gnawing leaves and winged butterflies sucking nectar, sessile crinoids and their planktonic doliolaria larvae - total only different ontogenetic stages of the same species. Age-related differences in lifestyle often lead to the fact that certain functions are performed entirely at a certain stage of development. For example, many species of insects with complete metamorphosis do not feed in the adult state. Growth and nutrition are carried out during the larval stages, while adults perform only the functions of dispersal and reproduction.

Age differences in a population significantly increase its ecological heterogeneity and, consequently, its resistance to the environment. The likelihood increases that, in the event of strong deviations of conditions from the norm, at least some viable individuals will remain in the population and it will be able to continue its existence.

The age structure of populations is adaptive in nature. It is formed on the basis of the biological properties of the species, but always also reflects the strength of the influence of environmental factors.

Age structure of plant populations. In plants, the age structure of the cenopopulation, i.e., the population of a particular phytocenosis, is determined by the ratio of age groups. The absolute, or calendar, age of a plant and its age state are not identical concepts. Plants of the same calendar age can be in different age states. The age state of an individual is the stage of its ontogenesis, at which it is characterized by certain relationships with the environment. Complete ontogenesis, or the large life cycle of plants, includes all stages of the development of an individual - from the emergence of the embryo to its death or to the complete death of all generations of its vegetatively arising offspring.

Seedlings have mixed nutrition due to the reserve substances of the seed and their own assimilation. These are small plants, which are characterized by the presence of embryonic structures: cotyledons, an embryonic root that has begun to grow, and, as a rule, a uniaxial shoot with small leaves, which often have a simpler shape than those of adult plants.

Juvenile plants begin to feed independently. They lack cotyledons, but the organization is still simple, uniaxiality is often preserved, and the leaves are of a different shape and smaller in size than those of adults.

Immature plants have characteristics and properties that are transitional from juvenile plants to adult vegetative ones. Their shoots often begin to branch, which leads to an increase in the photosynthetic apparatus.

In adult vegetative plants, features of a life form typical of the species appear in the structure of underground and above-ground organs, and the structure of the vegetative body fundamentally corresponds to the generative state, but reproductive organs are still absent.

The transition of plants into the generative period is determined not only by the appearance of flowers and fruits, but also by a deep internal biochemical and physiological restructuring of the body. In the generative period, Colchicum splendid plants contain approximately twice as much colchamine and half as much colchicine as in young and old vegetative individuals; in the eastern sverbiga, the content of all forms of phosphorus compounds sharply increases, as well as the activity of catalase, the intensity of photosynthesis and transpiration; in the reznikovaya gill, the RNA content increases 2 times, and total nitrogen increases 5 times.

Young generative plants bloom, form fruits, and the final formation of adult structures occurs. In some years there may be breaks in flowering.

Middle-aged generative plants usually reach the greatest power, have the greatest annual growth and seed production, and may also have a break in flowering. In this age state, clone-forming species often begin to exhibit disintegration of individuals and clones arise.

Old generative plants are characterized by a sharp decrease in reproductive function and weakening of the processes of shoot and root formation. The processes of death begin to prevail over the processes of new formation, and disintegration intensifies.

Old vegetative (subsenile) plants are characterized by the cessation of fruiting, a decrease in power, an increase in destructive processes, a weakening of the connection between the shoot and root systems, a simplification of the life form is possible, and the appearance of immature-type leaves.

Senile wounds are characterized by extreme decrepitude, a decrease in size; upon renewal, few buds are realized, and some juvenile features reappear (shape of leaves, character of shoots, etc.).

Dying individuals are an extreme expression of the senile state, when only some tissues of the plant remain alive and, in some cases, dormant buds that cannot develop above-ground shoots.

The distribution of individuals of a cenopopulation according to age states is called its age spectrum. It reflects the quantitative relationships of different age levels.

To determine the number of each age group in different species, different counting units are used. The counting unit can be individual individuals, if throughout the entire ontogeny they remain spatially isolated (in annuals, taproot mono- and polycarpic herbs, many trees and shrubs) or are clearly demarcated - clone parts. In long-rhizome and root-sprouting plants, the counting unit can be partial shoots or partial bushes, since with the physical integrity of the underground sphere they often turn out to be physiologically separated, which was established, for example, for lily of the valley when using radioactive phosphorus isotopes. In dense-turf grasses (pike, fescue, feather grass, snake grass, etc.), the counting unit, along with young individuals, can be a compact clone, which in relations with the environment acts as a single whole.

The number of seeds in the soil reserve, although this indicator is very important, is usually not taken into account when constructing the age spectrum of a coenopopulation, since counting them is very labor-intensive and it is almost impossible to obtain statistically reliable values.

If in age spectrum cenopopulation at the time of its observation, only seeds or young individuals are represented, it is called invasive. Such a coenopopulation is not capable of self-sustaining, and its existence depends on the supply of rudiments from the outside. Often this is a young coenopopulation that has just entered the biocenosis. If a coenopopulation is represented by all or almost all age groups (some age conditions in specific species may not be expressed, for example, immature, subsenile, juvenile), then it is called normal. Such a population is independent and capable To self-sustainment by seed or vegetative means. It may be dominated by one or another age group. In this regard, young, middle-aged and old normal coenopopulations are distinguished. A normal coenopopulation, consisting of individuals of all age groups, is called full-membered, and if individuals of any age conditions are absent (in unfavorable years, certain age groups may temporarily drop out), then the population is called normal incomplete.

The regressive coenopopulation is represented only by senile and subsenile or also generative, but old, not forming viable seeds. Such a coenopopulation is not capable of self-sustaining and depends on the introduction of rudiments from the outside.

An invasive coenopopulation can turn into a normal one, and a normal one into a regressive one.

The age structure of the coenopopulation is largely determined by the biological characteristics of the species: the frequency of fruiting, the number of produced seeds and vegetative rudiments, the duration of seed germination, the ability of vegetative rudiments to rejuvenate, the rate of transition of individuals from one age state to another, the ability to form clones, etc. The manifestation of all these biological characteristics, in turn, depend on environmental conditions. The course of ontogenesis also changes, which can occur in one species in many variants (polyvariance of ontogenesis), which affects the structure of the age spectrum of the coenopopulation

Different plant sizes reflect the different vitality of individuals within each age group. The vitality of an individual is manifested in the power of its vegetative and generative organs, which corresponds to the amount of accumulated energy, and in resistance to adverse influences, which is determined by the ability to regenerate. The vitality of each individual changes in ontogenesis along a single-peak curve, increasing on the ascending branch of ontogenesis and decreasing on the descending branch. In many species, individuals of the same age state in the same coenopopulation may have different vitality. This differentiation of individuals in terms of vitality can be caused by different quality of seeds, different periods of their germination, microconditions of the environment, the influence of animals and humans, and competitive relations. High vitality can remain until the death of an individual in all age states or decrease during ontogenesis. Plants with a high level of vitality often go through all age-related states at an accelerated pace. Plants with an average level of vitality often predominate in coenopopulations. Some of them go through ontogenesis completely, while others skip some of the age-related states, passing to a lower level of vitality before dying. Plants of a lower level of vitality have a shortened ontogeny, often passing into a senile state as soon as they begin to flower.

Individuals of the same coenopopulation can develop and move from one age state to another at different rates. Compared to normal development, when age-related states replace each other in the usual sequence, there may be an acceleration or delay in development, the loss of individual age-related states or entire periods, the onset of secondary dormancy, and some individuals may rejuvenate or die. Many meadow, forest, and steppe species, when grown in nurseries or crops, i.e., in the best agrotechnical background, shorten their ontogeny, for example, meadow fescue and hedgehog grass - from 20-25 to 4 years, spring adonis - from 100 up to 10-15 years, the reznikovaya gill - from 10-18 to 2 years. In other plants, when conditions improve, ontogenesis can lengthen, such as in caraway seeds.

In dry years and with increased grazing, the steppe species Schell's sheep loses certain age-related conditions. For example, adult vegetative individuals can immediately replenish the group of subenile, or less often, old generative ones. Corm plants of Colchicum splendidus in the central parts of compact clones, where conditions are less favorable (poor lighting, moisture, mineral nutrition, toxic effects of dead residues), quickly pass into a senile state than peripheral individuals. In the eastern sverbiga, under increased pasture load, when renewal buds are damaged, young and mature generative individuals may have breaks in flowering, thereby seeming to rejuvenate and prolong their ontogenesis.

In the common hedgehog, in different conditions, from 1-2 to 35 paths of ontogenesis are realized, and in the great plantain, from 2-4 to 100. The ability to change the path of ontogenesis ensures adaptation to changing environmental conditions and expands the ecological niche of the species.

Fluctuations in the age spectrum of the cenopopulation following weather conditions are especially characteristic of plants in floodplain meadows. In two species of sheep - Shell and fur-bearing sheep - in the Penza region, a cyclic change in age spectra in long-term dynamics is clearly observed. In dry years, sheep populations become older, and in wet years, they become younger.

The age spectrum can vary not only due to external conditions, but also depending on the reactivity and stability of the species themselves. Plants have different resistance to grazing: in some, grazing causes rejuvenation, since the plants die off before reaching old age (for example, in lowland wormwood), in others it contributes to the aging of the coenopopulation due to a decrease in regeneration (for example, in the steppe species of Dedebur's gill).

In some species, throughout the entire range in a wide range of conditions, normal coenopopulations retain the main cherries of the age structure (common ash, fescue, meadow fescue, etc.). This age spectrum depends primarily on the biological properties of the species and is called basic, It primarily preserves the relationships in the adult, most stable part. The number of newly emerging and dying individuals in each age group is balanced, and the overall spectrum turns out to be constant until significant changes in living conditions. Basic spectra most often have cenopopulations of edificator species in stable communities. They are contrasted with cenopopulations that relatively quickly change the age spectrum due to unestablished relationships with the environment

The larger the individual, the greater the scope of its influence on the environment and on neighboring plants (“phytogenic field”, according to A.A. Uranov). If the age spectrum of the cenopopulation is dominated by adult vegetative, young and middle-aged generative ones, then the entire population as a whole will occupy stronger position among others

Thus, not only the number, but also the age spectrum of the cenopopulation reflects its state and adaptability to changing environmental conditions and determines the position of the species in the biocenosis.

Age structure of populations in animals. Depending on the reproductive characteristics of the species, members of the population may belong to the same generation or to different ones. In the first case, all individuals are close in age and approximately simultaneously go through the next stages of the life cycle. An example is the reproduction of many species of non-gregarious locusts. In the spring, first instar larvae emerge from eggs that have overwintered in egg capsules laid in the ground. The hatching of larvae is somewhat prolonged under the influence of microclimatic and other conditions, but on the whole it proceeds quite smoothly. At this time, the population consists only of young insects. Through 2- 3 weeks, due to the uneven development of individual individuals, larvae of adjacent ages can be found in it at the same time, but gradually the entire population passes into the imaginal state and by the end of summer consists only of adult sexually mature forms. By winter, having laid eggs, they die. The age structure of populations is the same oak budworm, slugs of the genus Deroceras and other species with an annual development cycle that reproduce once in a lifetime. The timing of reproduction and the passage of individual age stages is usually confined to a certain season of the year. The size of such populations is, as a rule, unstable: strong deviations of conditions from the optimum at any stage of the life cycle immediately affect the entire population, causing significant mortality

Species with the simultaneous existence of different generations can be divided into two groups, those that reproduce once in a lifetime and those that reproduce many times.

In May beetles, for example, females die soon after laying eggs in the spring. The larvae develop in the soil and pupate in the fourth year of life. At the same time, there are representatives of four generations in the population, each of which appears a year after the previous one. Every year one generation completes its life cycle and a new one appears. Age groups in such a population are separated by a clear interval. Their ratio in numbers depends on how favorable the conditions turned out to be during the emergence and development of the next generation. For example, the generation may be small if late frosts destroy some of the eggs or cold rainy weather interferes with the flight and copulation of beetles.

In species with single reproduction and short life cycles, several generations occur throughout the year. The simultaneous existence of different generations is due to the protracted nature of oviposition, growth and sexual maturation of individual individuals. Ego occurs both as a result of the hereditary heterogeneity of members of the population, and under the influence of microclimatic and other conditions. For example, the beet moth, which harms sugar beets in the southern regions of the USSR, has caterpillars of different ages and pupae overwintering. Over the summer, 4-5 generations develop. Representatives of two or even three adjacent generations meet at the same time, but one of them, the next in time, always prevails.