Age structure of the population. Assessment of the state of woody plant populations according to geobotanical descriptions Ignoring the age characteristics of workers

With age, the requirements of an individual to the environment and resistance to its individual factors naturally and very significantly change. At different stages of ontogenesis, a change in habitats, a change in the type of nutrition, the nature of movement, and the general activity of organisms can occur. Often, age-related ecological differences within a species are expressed significantly. more than differences between species. grass frogs on land and their tadpoles in water bodies, caterpillars gnawing leaves, and winged butterflies, nectar-sucking, sessile crinoids and their planktonic doliolarian larvae are just different ontogenetic stages of the same species. Age differences in lifestyle often lead to the fact that individual functions are entirely performed at a certain stage of development. For example, many types of insects complete transformation do not feed in the imaginal state. Growth and nutrition are carried out on larval stages, whereas adults perform only the functions of settling and reproduction.

Age differences in the population significantly increase its ecological heterogeneity and, consequently, its resistance to the environment. The probability increases that in case of strong deviations of conditions from the norm, at least a part of viable individuals will remain in the population and it will be able to continue its existence. The age structure of populations has an adaptive character. It is formed on the basis of the biological properties of the species, but always also reflects the strength of the impact of environmental factors.

Age structure of populations in plants. 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. age, or ontogenetic state of the individual - this is the stage of its ontogeny, at which it is characterized certain relationships with the environment. Complete ontogeny, or the long life cycle of plants, includes all stages of the development of an individual - from the emergence of an embryo to its death or to the complete death of all generations of its vegetatively arisen offspring (Fig. 97).

Rice. 97. Age conditions of meadow fescue (A), Siberian cornflower (B):

R- seedlings; j- juvenile plants; im- immature; v- virginal; g 1- young generative; g2- middle-aged generative; g 3- old generative; ss - subsenile; s - senile

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

Juvenile Plants are transitioning to self-feeding. They lack cotyledons, but the organization is still simple, often retaining uniaxiality and leaves of a different shape and smaller size than in adults.

Immature plants have characteristics and properties that are transitional from juvenile plants to adult vegetative ones. They often begin branching of the shoot, which leads to an increase in the photosynthetic apparatus.

At adult vegetative In plants, features of a life form typical of the species appear in the structure of underground and terrestrial organs, and the structure of the vegetative body fundamentally corresponds to the generative state, but the 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 about twice as much colchamine and half as much colchicine as in young and old vegetative individuals; in sverbiga orientalis, 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 gillweed, the content of RNA increases by 2 times, and total nitrogen - by 5 times.

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

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

old generative plants are characterized by a sharp decrease in reproductive function, a weakening of the processes of shoot and root formation. The processes of dying off begin to prevail over the processes of neoformation, 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 shoot and root systems, a simplification of the life form is possible, the appearance of leaves of an immature type.

Senile plants characterized by extreme decrepitude, a decrease in size, few buds are realized during renewal, some juvenile features appear again (the shape of the leaves, the nature of the shoots, etc.).

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

In some trees (pedunculate oak, forest beech, field maple, etc.) quasi-senile age state (the term was proposed by T. A. Rabotnov). These are oppressed, stunted plants, described as stick-ups (Fig. 98). They acquire over time the features of the old vegetative plant without going through the generative phase.

Rice. 98. Ontogeny of English oak in favorable conditions (above) and with a lack of light (according to O. V. Smirnova, 1998)

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

To determine the size of each age group in different types use different counting units. Separate individuals can be a counting unit if they remain spatially isolated during the entire ontogenesis (in annuals, tap-rooted mono- and polycarpic grasses, many trees and shrubs) or are clearly demarcated parts of a clone. In long-rhizomatous and rhizomatous plants, partial shoots or partial bushes can be a counting unit, since with the physical integrity of the underground sphere they often turn out to be physiologically separated, which was established, for example, for May lily of the valley when using radioactive isotopes of phosphorus. In densely sod grasses (pike, fescue, feather grass, serpentine, etc.), along with young individuals, a compact clone can be a counting unit, which acts as a single whole in relations with the environment.

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 the cenopopulation, since their calculation is very laborious and it is practically impossible to obtain statistically reliable values.

If only seeds or young individuals are present in the age spectrum of the cenopopulation at the time of its observation, it is called invasive. Such a cenopopulation is not capable of self-maintenance, and its existence depends on the influx of rudiments from outside. Often this is a young cenopopulation that has just invaded the biocenosis. If the cenopopulation is represented by all or almost all age groups (some age states in specific species may not be expressed, for example, immature, subsenile, juvenile), then it is called normal. Such a population is independent and capable of self-maintenance by seed or vegetative means. It can be dominated by certain age groups. In this regard, young, middle-aged and old normal cenopopulations are distinguished.

A normal cenopopulation consisting of individuals of all age groups is called full member, and if there are no individuals of any age conditions (in unfavorable years, separate age groups may temporarily fall out), then the population is called normal incomplete.

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

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

The age structure of the cenopopulation is largely determined by the biological characteristics of the species: the frequency of fruiting, the number of produced seeds and vegetative primordia, the ability of vegetative primordia to rejuvenate, the rate of transition of individuals from one age state to another, the ability to form clones, etc. A typical age spectrum is called basic(Fig. 99). The manifestation of all these biological features, in turn, depends on the conditions external environment. 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 cenopopulation (Fig. 100).

Rice. 99. The basic type of the spectrum of coenopopulations (according to L. B. Zaugolyyuva, 1976) A - Lensky beetroot; B - leafless anabasis; B - meadow fescue; G - tipchak.

1 - base spectrum; 2 - limits of change of the base spectrum

Different plant sizes reflect different vitality 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 effects, 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 one. In many species, individuals of the same age state in the same cenopopulation may have different vitality. This differentiation of individuals in terms of vitality can be caused by the different quality of seeds, different terms their germination, environmental microconditions, the impact of animals and humans, competitive relations. High vitality can be maintained until the death of an individual in all age states or decrease in the course of ontogeny. Plants high level vitality often pass through all age states at an accelerated pace. In cenopopulations, plants of an average level of vitality often predominate. Some of them go through ontogenesis completely, while others skip part of the age states, passing to a lower level of vitality before dying off. Plants lower level vitality have a shortened ontogeny and often go into a senile state, barely starting to bloom.

Rice. 100. Options for the development of the hedgehog team in different environmental conditions (according to L. A. Zhukova, 1985). Latin letters indicate the age states of plants, and dotted lines indicate their possible sequence.

Individuals of one coenopopulation can develop and move from one age state to another with different speed. Compared with normal development, when age states replace each other in the usual sequence, there may be an acceleration or delay in development, the loss of individual age states or entire periods, the onset of secondary dormancy, some individuals may rejuvenate or die. Many meadow, forest, steppe species, when grown in nurseries or crops, that is, on the best agrotechnical background, reduce their ontogeny, for example, meadow fescue and cocksfoot - from 20-25 to 4 years, spring adonis - from 100 to 10 -15 years old, gillweed - from 10-18 to 2 years old. In other plants, when conditions improve, ontogeny can be lengthened, as, for example, in common cumin.

In dry years and with increased grazing in the steppe species of Shell's sheep, individual age states drop out. For example, adult vegetative individuals can immediately replenish the group of subsenile, less often old generative ones. Tuber-bulbous plants of Colchicum splendid in the central parts of compact clones, where conditions are less favorable (lighting, moisture, mineral nutrition are worse, the toxic effect of dead residues is manifested), quickly pass into a senile state than peripheral individuals. In Sverbiga orientalis, under increased grazing load, when the renewal buds are damaged, young and mature generative individuals may have interruptions in flowering, thereby rejuvenating themselves and prolonging their ontogeny.

Do the team's hedgehogs 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.

In two species of steppe sheep - Shell and pubescent - in Penza region the cyclical change in the age spectra in the long-term dynamics is clearly traced. In dry years, sheep populations age, and in wet years they get younger. Fluctuations in the age spectrum of cenopopulations following weather conditions are especially characteristic of plants in floodplain meadows.

The age spectrum may 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 plants die off before reaching old age (for example, in plain wormwood), in others it contributes to the aging of the cenopopulation due to a decrease in renewal (for example, in the steppe species of Ledebour's gill).

In some species, throughout the range, in a wide range of conditions, normal cenopopulations retain the main features of the age structure (common ash, fescue, meadow fescue, etc.). This age spectrum depends mainly on the biological properties of the species. In it, first of all, the ratios are preserved in the adult, most stable part. The number of newly emerging and dying individuals in each age group is balanced, and the total spectrum is constant until significant changes conditions of existence. Such basic spectra most often have cenopopulations of edificatory species in stable communities. They are contrasted with cenopopulations that relatively quickly change their age spectrum due to unstable relationships with the environment.

The larger the individual, the greater the scope and degree of its impact 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 individuals, then the entire population as a whole will occupy a 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 animal populations. Depending on the characteristics of reproduction, members of a population may belong to the same generation or to different ones. In the first case, all individuals are close in age and pass through the next stages approximately simultaneously. life cycle. An example is the reproduction of many grasshopper species. In the spring, the first-stage larvae appear from the eggs that have overwintered in egg-pods laid in the ground. The hatching of larvae is somewhat extended under the influence of microclimatic and other conditions, but on the whole proceeds quite amicably. At this time, the population consists only of young insects. After 2-3 weeks, due to the uneven development of individual individuals, larvae of adjacent instars can simultaneously occur in it, 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, laying eggs, they die. This is the same age structure of populations in the oak leafworm, slugs of the genus Deroceras, and other species with a one-year development cycle that breed once in a lifetime. The timing of reproduction and the passage of individual age stages are usually confined to a specific 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 affect the entire population at once, causing significant mortality.

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

In May beetles, for example, the females die shortly after laying eggs in the spring. The larvae develop in the soil and pupate in the fourth year of life. At the same time, representatives of four generations are present 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. The ratio of their numbers depends on how favorable the conditions were for the appearance 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 the beetles.

Rice. 101. The ratio of age groups of herring for 14 years. "Productive" generations can be traced for several years (according to F. Schwerdpfeger, 1963)

In species with a single reproduction and short life cycles, several generations are replaced during the year. The simultaneous existence of different generations is due to the prolongation of oviposition, growth and sexual maturation of individual individuals. This occurs both as a result of the hereditary heterogeneity of the members of the population, and under the influence of microclimatic and other conditions. For example, beet moths, which damage sugar beets in the southern regions of the USSR, have caterpillars of different ages and pupae overwinter. During the summer, 4-5 generations develop. At the same time, representatives of two or even three adjacent generations meet, but one of them, the next in terms, always prevails.

Rice. 102. The age structure of animal populations (according to Yu. Odum, 1975; V. F. Osadchikh and E. A. Yablonskaya, 1968):

A - general scheme, B - laboratory populations microtus voles agrestis, B - seasonal changes in the ratio of age groups of the mollusk Adaena vitrea in the Northern Caspian.

Different shading - different age groups:

1 - growing, 2 - stable, 3 - declining population

The age structure of populations in species with repeated reproduction is even more complicated (Fig. 101, 102). In this case, two extreme situations are possible: 1) life expectancy in the adult state is small and 2) adults live long and multiply many times. In the first case, a significant part of the population is replaced annually. Its number is unstable and can change dramatically in individual years, favorable or unfavorable for the next generation. The age structure of the population varies greatly.

In the root vole, the age structure of the population over the summer season gradually becomes more complex. At first, the population consists only of individuals of the last year of birth, then the young of the first and second litters are added. By the period of the appearance of the third and fourth offspring, puberty occurs in representatives of the first two, and generations of the grandchild generation join the population. In autumn, the population consists mainly of individuals of the current year of birth of different ages, since the older ones die.

In the second case, a relatively stable population structure arises, with long-term coexistence of different generations. So, Indian elephants reach sexual maturity by 8-12 years and live up to 60-70 years. The female gives birth to one, less often two elephants, about once every four years. In a herd, usually adult animals of different ages make up about 80%, young animals - about 20%. In species with higher fecundity, the ratio of age groups may be different, but general structure populations always remain quite complex, including representatives of different generations and their offspring of different ages. Fluctuations in the number of such species occur within small limits.

The long-term breeding part of a population is often referred to as reserve. The possibility of population recovery depends on the size of the population reserve. That part of the young that reach puberty and increase the stock is the annual replenishment populations. In species with the simultaneous existence of only one generation, the reserve is practically equal to zero and reproduction is carried out entirely due to replenishment. Species with a complex age structure are characterized by a significant stock size and a small but stable recruitment rate.

When human exploitation of natural populations of animals, taking into account their age structure is of paramount importance (Fig. 103). In species with a large annual recruitment, a larger part of the population can be removed without the threat of undermining its numbers. If, however, many adults are destroyed in a population with a complex age structure, then this will greatly slow down its recovery. For example, in pink salmon, which matures in the second year of life, it is possible to catch up to 50-60% of spawning individuals without the threat of further population decline. For chum salmon that matures later and has a more complex age structure, the removal rates from a mature herd should be lower.

Rice. 103. The age structure of the Taimyr population of wild reindeer during the period of moderate (A) and excessive (B) hunting (according to A. A. Kolpashchikov, 2000)

An analysis of the age structure helps to predict the size of the population over the life of a number of next generations. Such analyzes are widely used, for example, in the fish industry to predict the dynamics of commercial stocks. They use quite complex mathematical models with a quantitative expression of the impact on individual age groups of all environmental factors that can be accounted for. If the selected indicators of the age structure quite correctly reflect the real influence of the environment on natural population receive highly reliable forecasts that allow them to plan their catch for a number of years ahead.

According to the age. This is the most important component of the population structure.

1. Age structure of plant populations

In populations of perennial plants, all individuals are characterized by a set of biomorphic features that determine their age differentiation. For population studies, the definition of age states (biological age) is much more important than absolute age (calendar age). Based on a complex of qualitative traits, 4 periods and a maximum of 11 age states are distinguished in plant ontogeny:

I) latent (seeds) - characterized by long-term storage, constitutes the very reserve of the population; II) pregenerative (seedlings, juveniles, immature, virginal) - the development of plants before the appearance of generative shoots; III) generative (young, medium, old) - the formation of generative shoots; IV) senile (subsenile, senile, dying) - simplification life forms and dying.

The processes of neogenesis and accumulation of energy predominate towards the average generative state, and after that, the processes of death and energy loss.

The age structure is one of the most important characteristics of a population. The age spectrum reflects the vital state of the species in the cenosis, as well as such important processes as reproduction intensity, mortality rate, and the rate of generation change. From this side structural organization depends on the ability of the population system to self-maintenance and the degree of its resistance to the influence negative factors environment including and anthropogenic press. It also characterizes the stage of development of the population (wykovist), and, consequently, the prospects for development in the future.

1.1. Population types

There are three main types of populations depending on the stage:

• invasive - the population is not yet capable of self-maintenance, depends on the introduction of seeds from outside, consists mainly of pregenerative individuals,
• normal - self-maintenance occurs, mainly generative plants predominate,
• regressive - loss of the ability to self-sustain, post-generative predominate.

Among normals there are polynomials and non-polynomials if any age groups are missing, most often through an interruption of "insparmation", the extinction of certain age groups, or factors internal order that control the development of the population itself. With the predominance of a normal population in the age spectrum of individuals of a certain age group, young, mature, aging and old are distinguished.

1.2. Basic age spectra

With a fairly complete imagination of biology and ecological and phytocenotic confinement of a species, basic age spectra are distinguished (modal characteristics of normal populations in an equilibrium state). There are four main types that are distinguished by the position of the absolute maximum in the spectra of age states:

Type I - complete predominance of young individuals; II - generative; III - old generative or senile; IV-determined by two peaks in the old and young parts of the population (bimodal).

Literature

• Krichfalushi VV, Mezev-Krichfalushi GM Population biology of plants. - Uzhgorod., 1994.
• Mezev-Krichfalushiy G.N. Population biology of the Umbelliferae and prospects for its survival in Transcarpathia / / Ecology. - 1991. - No. 3.

INTRODUCTION

Russian hazel grouse ( Fritillaria ruthenica Wikstr.) is a species from the Liliaceae family. F.ruthenica listed in the Red Book of Russia, in the regional Red Books of the Saratov, Volgograd, Samara, Penza, Lipetsk, Tambov, Bryansk regions. Studying the age states of cenopopulations F. ruthenica in the Balashovsky district, as a rare and protected plant species is relevant, which determines the purpose of this study.

This is a perennial bulbous herbaceous plant with drooping flowers (life expectancy up to 20 years). Perianth simple, corolla-shaped, six-membered. The fruit is a box. This is a Eurasian species. Leaf growth begins in the second decade of April and continues until the second decade of May. Vegetation duration F. ruthenica in different age periods from 30 to 80 days. Depending on the timing and time of soil thawing, fluctuations between the start of vegetation in some years can reach 20-22 days. During the dormant period, only the bulb remains. F. ruthenica propagated both by seeds and vegetatively (renewal buds from bulbs or adnexal brood buds). F. ruthenica- xeromesophyte. Demanding on soils.

Category and status F. ruthenica in the Saratov region 2 (V) - vulnerable species. It grows in steppe meadows, among shrubs, on the edges and glades of deciduous forests, in steppe oak forests, on rocky chalk slopes. The limiting factors are - collection by the population and violation of the integrity of habitats.

MATERIALS AND RESEARCH METHODS

To study the state of cenopopulations F. ruthenica trial plots sized 1x1 m were laid. On each trial plot, the total number of individuals per 1 m 2 was taken into account. At 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 a accounting unit. Age conditions were determined according to the works of M.G. Vakhromeeva, S.V. Nikitina, L.V. Denisova, I. Yu. Parnikoz. Indices of recovery, age and efficiency were determined by the method of A.A. Uranov. The recovery index shows how many offspring there are per generative individual at the moment. The age index assesses the ontogenetic level of the CPU at a particular point in time, it varies in the range of 0-1. The higher its value, the older the studied CPU. 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.

Cm. age spectrum.

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"SPECTRUM OF AGE STATES" in books

The development of age-related diseases can be delayed

Chapter 14 He grows, or About age crises