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Features of the generative activity of steppe phytocenoses
S. V. Levykin, Ph.D. in Geology, G. V. Kazachkov, Ph.D. in Biology,
Steppe Institute, Ural Branch of the Russian Academy of Sciences, Orenburg
The zonal biota of the steppe, formed under specific conditions of high insolation and insufficient moisture, has a wide range manifestations of generative activity. When weather conditions are favorable for the development of certain species, the steppe repeatedly changes its appearance during the vegetative period. With the mass manifestation of the generative activity of certain plants in the steppe, a dense canopy of generative shoots is formed, creating a certain color background.
The regularities of the change of steppe aspects, which characterize the differentiation of natural zonality, were studied in detail by the classics of steppe studies at the scientific stations of the BIN of the USSR Academy of Sciences, in the Streletskaya and Cossack steppes near Kursk, the Starobelsky and Askaniysky steppes of Ukraine. The main aspective stages of vegetation, characteristic of the steppes of Northern Eurasia, are given below.
1. Meadow steppes of the Russian Chernozem region
In the meadow steppes of the Central Chernozem region (Streltskaya steppe near Kursk), 18 aspects are replaced during the mowing regime, while 16 brightly flowering dominant plants stand out.
2. Forb-feather grass steppes of Ukraine
In the northern variants of forb-feather grass steppes (Starobelsky steppes of Ukraine), 7 phases of vegetation development are described.
3. Fescue-feather grass steppes of southern Ukraine
In the fescue-feather grass steppes of Ukraine (Askanian virgin lands), up to seven aspects are noted.
4. Forb-feather grass steppes of the Southern Urals and Trans-Urals
For 1993-2005 On the steppe standards of the Southern Urals and Trans-Urals, the intensity of the seasonal change of the main phenological aspects of the standard steppe areas was studied. 10 aspects are allocated.
5. Xerophyto-fescue-feather grass dry steppes Northern Kazakhstan
The change of aspects in the dry infant-fescue-feather grass and chamomile-fescue-feather grass steppes (the most xerophytic variant of the soddy-cereal steppes of Northern Eurasia, Kazakhstan) includes seven phases of vegetation development.
6. Thin wormwood-fescue-feather grass desert steppes of Central Kazakhstan
Aspects of these steppes were studied in their northern part on the example of the scientific station of the Botanical Institute of the USSR Academy of Sciences (Karaganda region). In total, seven phases of vegetation development were noted.
7. Thin wormwood-tyrsic desert steppes of Central Kazakhstan
Aspects of the steppes were studied in their northern and central parts on the example of the scientific station of the Botanical Institute of the USSR Academy of Sciences (Karaganda region). Thin sagebrush-tyrsik steppes represent the southern boundary of the steppe type of vegetation in Northern Eurasia. 7 periods of the seasonal state of vegetation were noted.
8. Forb-cereal steppes of Dauria
A somewhat different phenological pattern is observed in the steppes of the Mongolian type in Southeastern Transbaikalia. This type of steppe is characterized by a shortened growing season and a shift in the maximum summer precipitation to the middle of the season. Six main seasonal and particular aspects are noted.
The peculiar appearance of the virgin steppe is determined by a combination of many types of grasses and different intensity of their flowering. In different years, different types of plants can intensively develop in the same area of the steppe: in dry years - cereals and semi-shrubs, in wet
Forbs.
In modern conditions of territorial disunity of small steppe areas, each of them rarely coincides with phases of plant biorhythms favorable for mass flowering and climatic conditions. Scientists have long noticed that the "old" absolutely protected steppe areas rarely show bright aspects. According to our observations, the most intensive generative activity is shown by "young" steppes - fallows, pastures. Plants-pioneers, mastering the vacant living space, find themselves in better ecological conditions than plants in the virgin lands. They have more food area, better lighting. The loose soil of the deposit has a higher productivity.
The ratio of heat and moisture plays a key role in the generative activity of the zonal flora. Moreover, the intensity of the formation of generative shoots depends on these two climatic factors in the previous and current years. In general, in the climax community, the intensity of flowering of plant dominants is associated with the alternation of favorable and unfavorable conditions in individual years. Manifestation
mass flowering only in some years due to the high cost of the plant nutrients for the formation of flowers and seeds. The next year (or several years), a plant that no longer has a sufficiently high energy reserve cannot bloom and bear fruit, especially if previous years were not favorable due to weather conditions. Under favorable conditions of the vegetative period, plants can accumulate a sufficient amount of nutrients by autumn, which can be used next year in case of unfavorable weather conditions. It has been proven that there is a "memory" of plants about previous weather conditions.
For example, we found that the formation of a bright silvery aspect of feather grasses in 2005 was facilitated by the fact that during previous years, feather grasses developed predominantly vegetative shoots. In addition, the autumn period of the previous 2004 was distinguished in 2002 by an increased amount of precipitation (by 110-245%) and high (by 1-5° above the norm) average daily temperatures.
Summarizing the above, we note that the seasonal aspects of the steppes are determined by the seasonal rhythms of the dominants, including autumn-winter period. As a rule, individual seasonal aspects are monotonous and relatively stable. Only their duration and brightness vary, due to weather features of the year. Plant dominants, and other plants, are also capable of creating a characteristic color background of varying intensity - a particular aspect that appears irregularly. For example, the May green background and the August straw-yellow aspect of the withering grasses are seasonal phenomena. Medium-intensive flowering of feather grasses
Seasonal late spring aspect, and their mass flowering is a private aspect.
An intensive change of particular aspects is most characteristic of the meadow steppes. There are so-called privately perspective species that can create a bright color background: tulips, feather grass, sage, bedstraws; and weakly aspective (gray) species: fescue, thin-legged, wormwood, etc., which give the seasonal aspect only a slight color tint.
The change and intensity of seasonal and particular aspects in the steppes is due to natural and climatic conditions, but is disturbed by irregular catastrophic events (fire, flooding, plowing, etc.).
Let's look at the main factors affecting the intensity of flowering and fruiting of one of the steppe dominants - feather grass (Bira \essingiand). This is the most typical petrophilic but calciphilic upland-steppe species. Formerly dominated vast areas, especially
in the subzone of southern chernozem and dark chestnut soils. This particular aspect of the steppe dominant
At the same time, the best of the feather grasses in terms of nutrition. In the virgin steppe, it makes up 75-90% of the total herbage yield. In this regard, we believe that this species may well claim the role of a "visiting card" of the zonal Ponto-Caspian steppes. The vegetative shoots of the feather grass form a stable seasonal green aspect, and its massive flowering and fruiting form a silvery private aspect.
The annual yield of feather grass seeds and, accordingly, the intensity of its characteristic silvery aspect can vary greatly depending on weather and other environmental conditions. Thus, according to research conducted at scientific stations of the Academy of Sciences of the USSR, yields of feather grass seeds can range from 0 seeds/m2 to 1683 seeds/m2. According to our observations (1991-2005), carried out in the first half of June on the steppe standards of the Southern Urals (Orenburg region, Kazakhstan), the feather grass intensively blossomed and fruited in 1991, 1998, 1999, 2000, 2002, 2005. A moderate aspect was observed in 1993, 1994, this species did not bloom at all in 1992, 1995, 1996, 2001, 2003, 2004. According to climatic conditions 1992, 1994, 2003 - abnormally wet, in 1995, 1996, 1998. there was a drought. In general, depending on the combination of favorable factors, “feather-grass” and “non-feather-grass” years are noted without obvious signs of cyclicity of their change. According to our observations, the year 2005 was the most “feather grass” in the Orenburg-Kazakhstan steppe ecoregion. feather grass seeds per 1 m2.
As mentioned above, young feather grass blooms most intensively, especially in conditions of fallow successions. The age of plants was determined solely by the age of the fallow (up to 10 years). It is believed that the feather grass has a lifespan of tens of years, so the natural change of generations is slow. In this regard, detailed studies of the intra- and interpopulation interaction of steppe dominants are required. Many questions need to be studied: does the aging of the steppe herbage exist in principle, the process of renewal inside the herbage is ongoing; whether steppe grass stands have age classes similar to those of woody vegetation; how much, as the grass stand matures and ages (if any), its generative activity and, accordingly, the intensity of generative reproduction decrease.
Frequent steppe fires, destroying the undergrowth of grasses and wormwood, contribute to the dominance of old large grass clumps, including feather grasses. While it is accepted that in modern
In steppe phytocenoses, the proportion of generative individuals is about 70%. However, it should be noted that it is still not known exactly to what age the grass stand needs to be regenerated by seeds. Is it possible to single out separate groups of different ages of one plant species in a phytocenosis? It is possible that the oldest individuals of the steppe dominants are not capable of seed reproduction at all.
Below we consider a system of environmental factors that affect the intensity of generative reproduction: the characteristics of a particular population of the steppe dominant, namely: the age of the population, the proportion of juvenile and mature individuals, the duration of the pause between two intensive flowering typical of the species (for feather grass, this period averages 3 years) ; meteorological factors, namely: temperature regime current year, the amount of precipitation in the autumn of the previous year, the amount of precipitation in the spring of the current season; anthropogenic factors, namely: the intensity of grazing, the timing and regularity of haying, the dynamics and intensity of the pyrogenic impact, the degree of territorial disunity of virgin lands.
For feather grass, favorable conditions for mass flowering are a combination of the optimal mode of economic use, heavy rainfall in the autumn of the previous year and spring of the current season, the optimal temperature regime in the spring of the current season and the end of the period.
yes pause after the last intensive flowering. In general, the factors that predetermine the intensity of fruiting of feather grasses can be differentiated as follows (Table 1).
Accordingly, the coincidence of not all favorable factors causes the flowering of feather grasses in the usual average mode. The coincidence of the majority adverse factors causes an adequate reaction of vegetation: only vegetative shoots develop, awns atrophy in their infancy and dry up. There is a "false" flowering and the formation of empty seeds.
Taking into account all of the above, including the fragmentation of the modern territory of the virgin steppes, in our opinion, simultaneously with the introduction of a territorial protection regime on them, it is advisable to carry out ecosystem care on some of these territories, which consists, in particular, in regulating the generative activity of the main steppe phytodominants. The expediency of these processes is primarily due to two reasons: the need to maintain high seed productivity of steppe genetic reserves in order to replicate agrosteppes according to the method of S. Dzybov and the high aesthetic significance of steppe aspects, in particular, for the development of ecotourism.
Literature
1 Alekhin, V. V. Essay on vegetation and its successive change in the area of the Streltsy steppe near Kursk // Proceedings of the St. Petersburg Society of Natural Sciences. 1909. Vol. 11.
2 Alekhin, VV Vegetation of the USSR. M.: Sovietskaya nauka, 1951. S. 256-321.
3 Borisova, I. V. Rhythms of seasonal development of steppe plants and zonal types of steppe vegetation in Central Kazakhstan // Tr. Bot. Institute im. V. L. Komarova Academy of Sciences of the USSR. Series III (geobotany). Issue. 17. M.-L.: Publishing House of the Academy of Sciences of the USSR, 1965. S. 64-100.
4 Borisova, I.V. Change of aspects and seasonal conditions // Biocomplex research in Kazakhstan. L., 1976. Part 3. Complex characteristic the main plant communities of the desert steppes of Central Kazakhstan. S. 7881; 145-148.
5 Gorshkova, A. A. Biology of steppe pasture plants in Transbaikalia. Moscow: Nauka, 1966.
6 Zhmykhova, V.S. Change of aspective patterns of the Streletskaya steppe under mowed and unmowed regimes of conservation // Biography and National economy: abstracts of reports. M., 1974. S. 27-30.
7 Lavrenko, E. M. Vegetation of the Starobelsk steppes / E. M. Lavrenko, G. I. Dokhman // Journal of the biobotanical cycle of VUAN. Kyiv, 1933. No. 5-6.
8 Pachosky, I.K. Vegetation of the Kherson province 2. Steppes. Kherson, 1917.
9 Rabotnov, T. A. Life cycle of perennial herbaceous plants in meadow cenoses // Tr. Bot. Institute im. V. L. Komarova Academy of Sciences of the USSR. Series III (geobotany). Issue. 6. M.-L., Publishing House of the Academy of Sciences of the USSR. 1950.
10Smenova-Tyan-Shanskaya AM Dynamics of steppe vegetation. M; L.: Nauka, 1966. 172 p. pTanfilyev, G.I. Botanical and geographical research in the steppe zone // Proceedings of Special Exped. Lesn. Department, St. Petersburg. 1898.
12Shalyt, M.S. Geobotanical essay Gos. Steppes. Reserve "Chapli", approx. Askania-Nova // Bulletin of the photographic station of the Steppe Institute "Chapli". 1930. Vol. 1.
1. Factors determining the intensity of fruiting of feather grasses
Factors favoring the abundant formation of generative shoots Factors reducing generative energy
Loose fallow soils Dense virgin soils
Territorial-ecological advantages of pioneer stages of demutation Competition
Population youth Population climax
Grazing of ungulates, especially horses Oppression of herbage by excessive grazing
Single fire in the autumn-winter period Frequent burning of herbage
Hay rotation Felt accumulation
Wet autumn Early hayfields during seeding period
Warm wet spring Dry autumn
Peak nutrient accumulation by the plant three years after the last mass flowering Dry early hot spring
lingering cold spring
Accumulation of solid precipitation below normal
Stretching for considerable distances from north to south and from west to east, the steppes on the territory of our country do not remain the same in terms of floristic composition and structure. In the forest-steppe zone, forbs take a significant part in the formation of steppe phytocenoses, among which, along with steppe xerophytes, meadow species are common.
The nature of the herbage of the steppe is influenced by the animal world, in particular, the activity of mouse-like rodents.
Steppe soils are predominantly various chernozems, which are replaced by chestnut soils in the south. Steppe plants have a high ash content, and the humus layer, whose thickness can reach 80-100 cm or more, is rich in mineral compounds, including calcium salts, and has a lumpy structure.
On the whole, the areas occupied by steppe vegetation are characterized by a continental climate; the degree of its continentality especially increases from west to east.
Steppe plants develop a deep root system covering a large volume of soil.
Adaptations to high temperature and lack of moisture are also manifested in the internal structure of organs: in cell sclerification, in an increase in the number of veins and stomata per unit area, etc.
Among the plants of the steppe there are those that “run away” from drought, completing the development cycle at a more favorable time of the year.
A greater number of species bloom in the first half of summer, during the best water supply for plants.
Ballista plants are common in the steppe, which have adaptations to keep fruits and seeds from spontaneous fall; but along with this, properties have developed that contribute to the scattering of the primordia and their removal from the mother's organism.
An even greater effect on the distribution of seeds and fruits is achieved in tumbleweed plants.
The steppes are characterized by a large species diversity, and it is richer in the northern steppes than in the southern ones.
In the northern steppes, with a large species and shoot saturation of the herbage, seven tiers are distinguished; the lower one is composed of species with shortened and creeping shoots; plants with tall erect shoots emerge in the upper tier. There are no clear boundaries between the individual tiers, and in each of them there is practically no dominant species, which distinguishes the northern steppes from the southern ones.
In the meadow steppes, the above-ground layer of green mosses is often well developed.
Great saturation of the herbage becomes possible in the presence of plants of different life forms. Plants differ from each other not only in the nature of the underground organs and the ability to root shoots, but also in the form of the shoot, the method of their renewal, the duration of the growing season of the monocarpic shoot before the transition to flowering, and the position of the shoot in space.
Among the cereals there are long rhizome, loose bush, rhizome and loose bush, dense bush.
According to their ecological characteristics, in particular in relation to water, the plants of the northern steppes are also different: among them are numerous xeromesophytes and mesoxerophytes.
In terms of the abundance of species and their participation in the herbage in the northern steppes, forbs predominate, and among grasses, horse and loose broad-leaved forms predominate.
Changes in the herbage take place not only in space, but also in time.
The multi-tiered structure of the steppe phytocenosis in the air is complemented by the tiered placement of underground shoots and root systems in the soil.
In the southern steppes, in contrast to the northern steppes, the role of cereals increases and, accordingly, the participation of forbs in the composition of the herbage decreases.
From rhizomatous cereals in the southern steppes grow wheatgrass, creeping wheatgrass, hairy wheatgrass. The bluegrass is a sharp-leaved - kotneischno - friable bush grass - characteristic of meadow steppes.
With the advancement from north to south, the steppes become less colorful, floristically poorer, the density of vegetation decreases, the edificatory role of large-turf grasses increases, the aerial parts of plants do not always close, the layered structure is less complex, the xeromorphic organization of long-term vegetative plants increases, the role and participation in the addition of the herbage of short-vegetating plants, the number of drought-resistant shrubs and semi-shrubs increases, and the summer break in the growing season becomes more pronounced.
It is necessary to preserve the entire diversity of species, with all their varying properties and traits, in protected areas and sanctuaries, and to preserve the gene pool created by nature.
Goals:
Expand based on
practical study of students' knowledge about the phytocenosis of the steppe area;
Promote learning
students' ability to observe, analyze, draw conclusions.
Raising a culture of communication with nature.
Equipment: camera, meter rulers, thermometers, magnifiers, notebooks and pencils, 4 pegs, 40 m of clothesline.
Place of excursion: steppe area
Course of the tour:
I. Orgmoment
TB instruction.
1. Introductory talk about BGC
BIOGEOCENOSIS (from bio... geo... and Greek koinos - general), a homogeneous area of the earth's surface with a certain composition of living (biocenosis) and inert (ground layer of the atmosphere, solar energy, soil, etc.) components and dynamic interaction between them (the exchange of matter and energy). The term was proposed by V. N. Sukachev (1940).
2. Repetition of the methodology of geobotanical descriptions.
1.1 Research methodology.
The main task of the study is to create a list of the Cretaceous flora and vegetation of the “bald mountain of the Veydelevsky region”, and their botanical-geographical aspect.
Flora is a collection of plant species that live in a certain area.
Vegetation is a set of plant communities.
Plant community - (phytocenosis) - a set of plants in a given territory, interdependent on each other and the environment.
Association - as an elementary plant community, is the basic unit in geobotany. The association is characterized by the following main features:
1.floristic composition; 5.coating;
2.aspect; 6.occurrence;
3.tiered; 7. vitality;
4.abundance; 8. life forms.
1. The floristic composition determines the structure of the association and is decisive for its characteristics.
2. Aspect - the appearance of the community, which determines its " physiognomy". It is characterized by dynamism, the following symbols are used to indicate the role of various plants in the aspect:
Δ - the view that plays a primary role in the aspect;
Δ - minor participation;
Δ - tertiary;
Δ - no participation.
Symbols of the phenological state:
----! -vegetation to flowering;
^-budding;
ŋ - flowering;
o - full bloom;
with - flowering;
Fruiting;
# - fruits crumble;
The fruits fall off.
3. Layering is the arrangement of plants in different horizons. Species that dominate in a certain tier are called dominants.
4. Abundance - an indicator characterizing the quantitative representation of a species in a given association.
For a subjective assessment of abundance, we use the notation proposed by the Danish scientist Drude and revised by our scientists
(Drude scale):
soc - plants create background 100 !
cop 3 - very abundant 90-80 } per 100 m 2
cop 2 - abundant 70-60
cop 1 - quite abundant 50-40
sp 3 - scattered 30
sp 2 - occasionally 20) per 100 m 2
sp 1 - rarely 10
sol - alone< 10
Un - one copy
Plants of the same species occur in patch(s)
Point counting is carried out by counting the number of specimens of a part of all plant species in small areas (1.0; 0.5 or 0.25).
5. Cover - the degree of soil occupancy by plants. The assessment is done visually in percentage terms.
6. Occurrence - determined by the Ramensky method by laying test sites of 0.1 m 2.
Occurrence - the frequency of detection of plants of each species in phytocenosis. Determination of a sufficiently large frequency by taking into account species on small sites (usually 1 x 1) and is expressed as the percentage of areas where this species was encountered:
B = 100 n
no
where B is the occurrence in %,
n - number of sites,
n o is the total number of sites.
Completing of the work.
Description Form No.
Association name:
Geographical position:
The general nature of the relief:
The position of the association area in the relief (indicate the exposure of the slope):
Microrelief (nature of elevations and depressions, their sizes):
Soil and description of the soil section:
Other features:
species composition
Participation in an aspect
Coating
Layered
Fen. condition
Vitality
Occurrence rate
Species composition encountered outside the sampling site at a distance of 10 m
Species composition of animals encountered during route passages
III. Summing up.
IV. Homework. Prepare a group report in the form of stands or presentations, including tables, sketches and photographs.
480 rub. | 150 UAH | $7.5 ", MOUSEOFF, FGCOLOR, "#FFFFCC",BGCOLOR, "#393939");" onMouseOut="return nd();"> Thesis - 480 rubles, shipping 10 minutes 24 hours a day, seven days a week and holidays
Avanesova Anna A. Succession of steppe phytocenoses of the European forest-steppe: 03.00.05 Avanesova, Anna Alexandrovna Succession of steppe phytocenoses of the European forest-steppe (on the example of the VV Alekhin Central Chernozem Biosphere Reserve): Dis. ... cand. biol. Sciences: 03.00.05 Voronezh, 2006 166 p. RSL OD, 61:06-3/1309
Introduction
Chapter 1. Studies of the vegetation cover of the Streletskaya steppe 7
1.1. Characteristics of virgin upland steppe phytocenoses of the Streletskaya steppe 7
1.2. Study of the flora of the Streletskaya steppe 14
1.3. Studies of productivity and species saturation of steppe phytocenoses 18
1.4. Successional changes in steppe phytocenoses under different protection regimes 22
1.5. The study of biomorphological features of plants of the Streletskaya steppe 35
Chapter 2. Area, materials and research methods 45
Chapter 3 The current state of phytocenoses of the Streletskaya steppe 50
3.1. Species composition and productivity in absolutely protected and adjacent mowing phytocenoses in the western part of the Streletskaya steppe 50
3.2. Species composition and productivity in absolutely reserved and adjacent mowing phytocenoses in the central part of the Streletskaya steppe 61
Chapter 4 Successions of steppe phytocenoses under the influence of an absolutely protected regime 71
4.2. Expansion of trees and shrubs on the Streletskaya steppe 77
4.3. Stages of succession of steppe phytocenoses in areas with an absolutely reserved regime 90
Chapter 5 Successions of steppe phytocenoses under the influence of haymaking 95
5.2. Stages of succession of steppe phytocenoses in areas with periodic mowing 103
Chapter 6
Conclusion 115
Findings 117
Suggestions for using research results 120
List of used literature 121
Applications 137
Introduction to work
Relevance of the topic. The study of succession is not only of deep theoretical interest, but also of practical importance. It is also important to study the succession of the vegetation cover, which occurs as a result of the changes that a person makes at the present time. economic activity(Kamyshev, 1964).
Central Chernozem State Biosphere Reserve named after V.I. prof. V.V. Alekhin (Kursk region) is the basis for studying changes in virgin steppe phytocenoses under the influence of certain protection regimes. The meadow steppes of the Central Chernozem Reserve are unique systems that have almost disappeared throughout Eurasia due to plowing and human economic activity (Alekhin, 1936). The processing of biological material accumulated in the Central Black Earth State Biosphere Reserve has a large scientific significance in connection with the alignment of the UNESCO Man and the Biosphere (MAB) Program and the Convention on Biological Diversity of Species wildlife adopted in 1992.
The successions of meadow-steppe phytocenoses under various protection regimes have not been sufficiently studied. It is necessary to know the direction of these changes in order to correct the processes occurring in them and optimize the steppe nature management (Lavrenko, 1959).
A large number of studies of vegetation cover have been carried out in the forest-steppe zone. This is due to its economic importance, as well as the fact that the study of steppe vegetation leads to the identification of phytocenological and floristic problems (Kultiasov, 1981). One of the problems is the "steppe issue", which reveals the reasons for the lack of forests of the steppes (Komarov, 1951).
Recently, great changes have been observed in steppe phytocenoses and the spread of trees and shrubs in areas with a reserved regime.
Data on the state of meadow-steppe phytocenoses, obtained in different years, are the material for identifying succession stages.
Purpose and objectives of the study. The purpose of this study is to study the succession of steppe phytocenoses of the European forest-steppe (on the example of the Central Chernozem Biosphere Reserve named after V.V. Alekhin).
To achieve this goal, the following tasks were set:
1. Reveal features state of the art steppe phytocenoses with a periodic mowing regime (RPK) and an absolutely reserved regime (RAS), paying special attention to the distribution of trees and shrubs.
2. Determine the directions of succession of steppe phytocenoses with RAS and RPC.
3. Identify stages of succession of steppe phytocenoses during RAS and RPK.
4. Compare ongoing successions of the vegetation cover of the Central Chernozem Reserve with changes in similar meadow-steppe communities of the European forest-steppe.
Scientific novelty of the work. For the first time, the stage of light forests in phytocenoses with an absolutely reserved regime was described, and the stages of vegetation succession were identified under an absolutely reserved regime of protection and a regime of periodic mowing. The dynamics in the expansion of trees and shrubs in all unmowed areas of the Streltsy section of the Central Chernozem Reserve has been established. Meadow formation was established in areas with the PKK regime and afforestation in areas with RAS in the steppe phytocenoses of the Streletskaya steppe.
Basic provisions for defense.
1. Analysis of changes in the species composition, species saturation, productivity and moisture indices according to L.G. Ramensky indicates the meadowing of the steppe communities of the Streletskaya steppe during the period of the reserve's existence.
2. In phytocenoses with PKK, the moisture index changed (from 51.9 to 52.7 on the moisture scale of L.G. Ramensky). Currently, phytocenoses with PKK are located on the border between meadow steppes and dry, fresh meadows. Phytocenoses with RAS are characterized as fresh meadows (level 56 on the moisture scale of L.G. Ramensky) with the expansion of forest species, trees and shrubs.
3. Evaluation of the succession of phytocenoses with RAS and RPC of the Streletskaya steppe and others protected areas showed that the identified changes are characteristic of protected meadow-steppe communities throughout the European forest-steppe.
Practical significance. The materials presented in the dissertation summarize the accumulated experience in the protection of meadow steppes in the Central Chernozem Reserve, allow you to choose rational methods for the protection of meadow steppes, confirm the assessment of the absolutely reserved regime of N.S. Kamyshev (1965), as a regime leading to the loss of meadow-steppe phytocenoses and the emergence of light forests.
Approbation of work. The main provisions of the dissertation were presented and discussed at scientific conferences "Phytocenoses of the northern forest-steppe and their protection" (Kursk, 2001), "Flora and vegetation of the Central Chernozem region" (Kursk, 2002,2003,2004), "Anthropogenic impact on flora and vegetation" (Lipetsk , 2001), "Studying and protecting the nature of the forest-steppe" (Kursk, 2002), II International Conference on anatomy and morphology of plants (St. Petersburg, 2002), "Historical landscape. Nature, Archeology. History "(Tula-Kulikovo field, 2002).
Workload. The dissertation of 166 pages consists of an introduction, 6 chapters, a conclusion, conclusions and 29 pages of an appendix; contains 120 pages of main text, 22 figures, 9 tables. The list of references includes 217 titles, of which 9 are foreign languages.
Characteristics of virgin upland steppe phytocenoses of the Streletskaya steppe
The Central Black Earth State Reserve was established in 1935. on the initiative of the famous botanist-geographer V.V. Alekhin with the aim of preserving and studying virgin areas of forb-cereal (or meadow) steppes and oak forests adjacent to them. The reserve consists of 6 separate sections, the largest of which are Streletsky (2.2 thousand hectares), Cossack (1.5 thousand hectares).
Before the creation of the reserve, its meadow-steppe areas, judging by historical documents, were used over the past 200-300 years as hay and pasture lands and, thus, were subjected to relatively weak anthropogenic changes.
The most representative section of the reserve is Streletsky. Here, the most complete and versatile studies of natural geosystems characteristic of the central forest-steppe were carried out. The Streltsy section of the reserve is located in the interfluve of the upper reaches of the river. The Seim and its tributary - Mlodati, in the middle part of the Central Russian Upland, in the Central forest-steppe. Most of this area (911 ha) is virgin steppe (Zozulin, 1950), which is known as the Streletskaya steppe (Fig. 1).
V.V. Alekhin refers the Streletskaya steppe to the northern steppes, which occupy the northern parts of the steppe zone and are sometimes called "meadow" in their resemblance to the meadow, and characterizes them as colorful-forb with broad-leaved grasses (Alekhin, 1936: 522-529).
The Streltsy steppe, according to the summary "Vegetation of the USSR", refers to meadow steppes, steppe meadows in combination with forest areas (forest-steppe). This is part of the East European forest-steppe, which stretches on the "Geobotanical Map of the USSR" in the form of a continuous strip from the Prut and Dnieper basins to the southern Urals. (Lavrenko, 1956: 670-671).
According to F.N. Milkov (Milkov, 1961: 46-57) the Streltsy steppe belongs to the forest-steppe zone, the forest-steppe province of the Central Russian Upland, the typical forest-steppe subzone, the Sudzhansky district, located in the basin of the upper Seim, Psel, and Vorkla rivers.
N.S. Kamyshev (1961) calls the Streletskaya steppe a northern pinnate-feather grass-fescue-forb steppe. Later, during the botanical and geographical zoning of the Central Chernozem regions, N.S. Kamyshev (1964) refers the Streletskaya steppe to the area of snotty oak forests of pinnate feather grass-fescue steppes of the Central Russian forest-steppe province.
EAT. Lavrenko et al. (1991: 26-42) attribute the Streletskaya steppe to the steppes of the Black Sea-Kazakhstan subregion, the East European block of the province, to the type of Central Russian meadow steppes and steppe meadows. I. A. Bannikova (1998) classifies the Streletskaya steppe as part of the Kursk region of the Eurasian forest-steppe. Meadow-steppe phytocenoses of the Central Russian forest-steppe began to form after the last glaciation, from the middle of the Holocene, i.e. 20,000 years ago. These are the oldest established communities (Dohman, 1968). A.M. Semenova-Tyan-Shanskaya (1966) refers the upland phytocenoses of the Streltsy steppe to steppe meadows. “Comparing them in a number of indicators with real steppes and northern meadows emphasizes their intermediate position and undoubted connections with both types of herbaceous vegetation, thus confirming its general zonality and gradual transitions between steppes and meadows through an intermediate link of steppe meadows, which includes the studied archery communities” (Semenova-Tyan-Shanskaya, 1966:140). Meadow-steppe phytocenoses in the Kursk region are formed by steppe turf grasses, feather grass, fescue, and thin-legged with numerous colorful herbs. These communities are confined to the highest parts of the watersheds and their gentle slopes and dominate the steep slopes of southern exposure beams. They are found in the Kursk region mainly in the Central Russian forest-steppe subprovince, which lies in the southeast of the river. Seim. The remaining virgin steppes of the Central Chernozem Reserve are also located here (Atlas of the Kursk Region, 2000) Asteraceae (61.1%), Poaceae (13%), Brassicaceae (7.6%), Fabaceae (7.3%), Lamiaceae (6.6%), Caryophyllaceae (6.1%), Scrophulariaceae (5 .9%"), Rosaceae (5.4%), Ranmculaceae (3%), Apiaceae (2.5%) (Sapronova, 2001). The steppe flora and steppe phytocenoses have been formed throughout their history under the influence of changing environmental conditions. Diversity environmental factors usually grouped as follows (Mirkin et al., 2000:16): 1. Climatic factors. 2. Edaphic factors. 3. Topographic factors. 4. Biotic factors. 5. Anthropogenic factors Abiotic factors that unite the first three groups: geographical location (temperate-cold climate zone), amount of precipitation (average annual precipitation - 582.3 mm), mean annual temperature(+5.4С), the complexity of the soil cover, well-developed micro- and macrorelief are favorable for the development of steppe phytocenoses. “The combination and existence of ecologically different species in small areas is primarily due to the variable nature of moisture, due to which drought-resistant steppe species and real meadow and forest-meadow mesophytes, as well as the meadow-steppe species most characteristic of the forest-steppe (in a broad sense) can develop here. plants” (Semenova-Tyan-Shanskaya, 1966:32-33). The main features of meadow steppes are that: 1) mesoxerophilic and euxerophilic elements predominate in the herbage composition, but mesophytes still play a significant role; 2) turf grasses predominate with an abundance of northern steppe mesophilic forbs, rhizomatous grasses play a subordinate role; 3) synusia of annuals and ephemeroids, as well as shrubs, are weakly expressed; 4) a moss cover is often developed on the soil (Lavrenko, 1940; Kultiasov, 1981). Abiotic factors determine the polydominance and ecological diversity of steppe communities and high species saturation (up to 80 species per 1 m), which distinguishes meadow-steppe phytocenoses from all herbaceous watershed communities of the Russian Plain (Coupland, 1993).
Species composition and productivity in absolutely protected and adjacent mowing phytocenoses in the western part of the Streletskaya steppe
Standard geobotanical descriptions were carried out from 2001-2005 on sample plots of 100 m using the methods of "Field Geobotany" (1959-1976). In 2001, research was carried out in 19, 20 quarters. In the 19th quarter, sites were laid along the eastern dividing line of the mowing and non-mowed parts in steppe phytocenoses with an absolutely reserved regime (description No. 3, 4, 10, 11), a periodic mowing regime (descriptions No. 1,2,9,12). Sites with periodic mowing were also studied in quarter 20 near the curtain with a peony, near the first hole in Petrina Log (description No. 5, 6, 7, 8). with the mode of periodic mowing (description No. 13, 14, 15, 16.17) and the absolutely reserved mode (description No. 18,19,20,21,22). When studying the meridional profile in 2003. on unmowed section No. 2, passing from the fire tower to Petrin log, test sites of 100 m2 were laid in quarters 8 and 13 (description No. 23, 24, 25, 26). In 2005, descriptions were made in steppe phytocenoses under an absolutely reserved regime in the 19th quarter (descriptions No. 27,28,29,30,31,32,33,34,35,36).
The abundance of plants was considered according to the Drude scale, since All previous researchers used this method in the reserve. According to this scale, seedlings of trees and shrubs included in the grass layer were taken into account in absolutely protected areas. The name of associations was determined by dominants. In the last place in the name, the dominant plant was indicated. The classification of vegetation was carried out according to the ecological-morphological (dominant) principle (Yaroshenko, 1953)
Species saturation of steppe phytocenoses was determined on meter squares with three repetitions (U shteker, 1980). The biomorphological analysis is based on the system of life forms of Raunkiaer (Raunkiaer, 1937) with additions for the analysis of the vegetation of the Central Russian forest-steppe by M.I. Paderevskaya (1977, 1979) and data on biomorphological structures identified by V.N. Golubev (1962). Moisture steps were calculated according to the scales of L.G. Ramensky (Ramensky et al., 1956)
The determination of the productivity of steppe phytocenoses with an absolutely protected regime and a regime of periodic mowing was carried out by the value of the aboveground phytomass during its maximum development, when at least 80% of vascular plant species pass into the generative phase (phenological maximum). Taking into account the lag in the development of plants under conditions of an absolutely reserved regime, cuttings were taken in these areas two weeks later (Sobakinskikh, 1996).
In 2001, cuttings were taken in the 19th quarter on plots with a periodic mowing regime on July 3, 2001 and on plots with an absolutely reserved regime on July 16, 01. In 2002, cuttings were taken on a site with a periodic mowing regime in the 17th quarter on July 2, 2002 and on a site with an absolutely reserved regime in the 17th quarter on July 16, 02
Samples were taken using a counting frame of 0.25 m in 8 replicates. Mowing was carried out at the level of the soil with the cutting of all dense turfs. Litter and moss were collected in separate bags. The entire aboveground phytomass (t) was differentiated by us into green (t) and dead parts (n/). In the green part of the aboveground phytomass, fractions were distinguished - economic and botanical groups: turf grasses (h), rhizomatous and loose shrub grasses (hcr), sedges (o), legumes (b), forbs (p) and mosses (m). The dead part of the cut was subdivided into rags (c) and litter (p). Rag - dead shoots that have retained a connection with the mother plant. Litter (felt) is dead plant residues that form on the surface of the soil. Dry samples were subjected to weight analysis. In 2001-2003, the distribution of trees and shrubs was studied on all unmown areas. On the first and second unmowed plots, trial plots of 500 m were laid, the size of which is provided by the method of V.N. Sukacheva (1957) revealing the features of forest phytocenoses. Sections No. 3 and No. 4 were mapped completely. A re-mapping of the profile (6 ha) laid down by V.D. Sobakinskikh in 1980-1981 was carried out, which runs in the meridional direction from the fire observation tower to Petrin Log. Horizontal projections of crowns of trees and shrubs and their heights were recorded for the listed areas. As the main criterion for identifying the ratio of the species composition of trees, shrubs and their cumulative role in phytocenoses, preference was given to the area of crown projections - projective cover. The projections of the crowns of continuous thickets of shrubs were plotted along the contours on the plan.
Based on the analysis of the literature sources mentioned above, with the involvement of the results of our own research, the main stages of vegetation succession were distinguished in areas with periodically and absolutely reserved regimes over the past 70 years. When determining the time limits, the time of the description of phytocenoses by the researchers was taken into account, and for the initial - the classical description of 1933 (Alekhin, 1936). The stages of succession were distinguished according to the main indicators of species composition, species saturation, the ratio of economic and botanical groups, dominants of the main associations, moisture indices of L.G. Ramensky (1956), chronoclines (Mirkin, 1978).
The direction of vegetation change in areas with an absolutely protected regime
The successions mentioned above are due to irreversible changes in steppe phytocenoses, which occurred under the influence of changing interconnected ecological conditions in complex systems of plant communities of meadow steppes.
The complexity of the meadow steppes lies in the combination in them of plants that are different in their biological characteristics, which belong to different ecological groups, various ecological and phytocenotic elements, and various life forms.
During the time that has passed since the establishment of the reserve (1935), changes in vegetation have occurred, leading to the replacement of some communities by others.
The absolutely reserved regime created for the steppe phytocenoses in the reserve has never been characteristic of these communities. In the pre-agricultural steppe, herds of herbivores grazed, later people used the steppes for pastures and hayfields. Throughout the existence of the steppes, alienation of terrestrial phytomass and grazing were constantly taking place.
Absolutely protected regime (grazing and haying), as exogenous anthropogenic factor, led to the emergence of new endogenous factors, which were expressed: 1. In the accumulation of rags and bedding. 2. Delay snow, its slow melting. 3. Changing the temperature regime. 4. Changing the moisture regime (Semenova-Tyan-Shanskaya, 1966). Since changes in vegetation occur due to the interaction of phytocenosis and ecotope, caused by the processes of reproduction and growth of plants, this successional process is an autogenous syngenesis (Mirkin, 1989). Gradual changes in phytocenoses can be traced in the works of previous researchers V.V. Alekhin (1935, 1938, 1936, 1940), N.A. Prozorovsky (1940), G.M. Zozulina (1955, 1959), V.N. Golubeva (1962.1965), D. Radulescu-Ivan (1967.1968), Semenova-Tyan-Shanskaya (1960.1966), G.I. Dokhman (1965, 1966, 1968), I.F. Petrova (1990), V.D. Sobakinsky (2000, 2002). Analysis of descriptions of communities, their characteristics, yield tables make it possible to detect the features of changes in the main indicators. At the same time, stages in the development of phytocenoses are indicated, the boundaries of which are determined by the time of the most full descriptions phytocenoses. Chronoclines of the average abundance of the main plant species in the available descriptions (Alekhin, 1935; Prozorovsky, 1940; Zozulin, 1955; Radulescu-Ivan, 1965, 1967; Dokhman, 1968; Semenova-Tyan-Shanskaya, 1966; Petrova, 1990; Sobakinskikh, 2000) and our own data show that Festuca valesiaca and Carex humilis fall out from RAS in phytocenoses. Increased their abundance of Calamagrostis epigeios, Arrhenaterum elatius over the past 40 years. There is an increase in the abundance of Bromopsis reparia, Stipa pennata in the 60s and a decrease in their present time. The abundance of the main aspecting species decreased with complete loss of Salvia pratensis, Myosotis popovii (Fig. 12).
In the absence of grazing and haymaking at the second stage of development, feather grasses grew, especially in unmowed areas. Stipa pennata has larger tufts than Festuca sulcata and has a longer individual development cycle, up to 50 years. The originally existing tufts of feather grass, in the absence of grazing, naturally grew, reaching their maximum size and age in unmowed areas, creating a hobble, together with young individuals of seed renewal, which was facilitated by a relatively small total projective cover in the original phytocenoses. Hogging was less common in mowed areas, because it is known that haymaking inhibits feather grasses (Dokhman, 1966).
The distribution of Calamagrostis epigeios at the third stage of succession in unmowed areas, which, however, is not observed in areas with periodic mowing, is associated with its biological features. Reed grass spreads and self-sustains with numerous seeds, which are carried by the wind over long distances, and rhizomes. This plant, which reaches large sizes (up to 170 cm), is well leafy and forms thickets. Other cereals, including feather grass and bonfires, cannot compete with reed grass.
The successional processes occurring in phytocenoses with RAS are indicated by the change in moisture indices according to the ecological scales of L.G. Ramensky. When processing materials according to ecological scales, full lists of descriptions of phytocenoses were used with an indication of abundance according to the category of projective cover Yu.N. Neshataeva (1987). For comparison, in addition to our own data, the moisture indices of steppe phytocenoses were determined according to the lists of V.V. Alekhina (1936), D. Radulescu-Ivan (1965), G.I. Dokhman (1968), data of M.I. Paderevskaya (1967), I.F. Petrova (1990), obtained on the uplands of the Streletskaya steppe in the same habitats.
The processing of descriptions on ecological scales indicates a change in the direction of increasing moisture content (Table 5), which indicates the transition of meadow steppes to fresh meadows. According to L.G. Ramensky (1956), meadow steppes are characterized by the ecological scale level with indices 47-52, and dry and fresh meadows are characterized by the 53-63 level.
The direction of vegetation change in areas with periodic mowing
Some of the species indicated by V.V. were not included in our lists. Alekhin: Vicia cracca, Androsace septentrionalis, Acinos arvensis, Cerastium holosteoides Fries, Dianthus andrzejowskianus (Zapal.) Kules., Helichrysum arenarium (L.) Moech, Hieracium pilosella L., Sisymbrium polymorphum (Murr.) Roth, Bertoroa incana (L. )DC, Prunella grandiflora (L.) Scholl., Erysimum hieracifolium L., Potentilla heptaphylla Jusl., Rumex acetosella L..
Chronoclines of the average abundance of the main plant species of the available descriptions (Alekhin, 1935; Prozorovsky, 1940; Zozulin, 1955; Radulescu-Ivan, 1965, 1967; Dokhman, 1968; Semenova-Tyan-Shanskaya, 1966; Petrova, 1990; Sobakinskikh, 2000) and own data show that there have been quantitative changes in the characteristics of phytocenoses in the mown areas. The abundance of Elytrigia repens, Festuca valesiaca (cop - sol, sp), Carex caryophyllea (sol - un), Carex humilis (cop - sol), Carex praecox (sp - sol), Onobrychis arenana (cop - sp, sol), Lathyrus is decreasing lacteus (sp - sol), Achillea millefolium (sp -»sol), Asperula cynanchica (sp-sol), Asperula tinctoria (sp- - sol), Campanula sibirica (sp-sol, un), Erigeron acris (sp - un) , Filipendula vulgaris (cop2- sp), /im/a /wrta L. (sp - sol), Ms aphylla L. (sp - sol, un), Jurinea arachnoidea (sp - un), Leucanthemum vulgare (cop - sol) , Z/ww/w perenne (sp - sol, un), Salvia nutans (sol -» un), Polygala comosa (sp - sol, un), Myosotis popovii (sp - un), Thymus marschalianus (sp-sol), Tragopogon orientalis (cop - un), Valeriana rossica (sp - nin), FzWa rupestris (cop - sp, sol). The abundance of Elytrigia intermedia (sol - sp), Helictotrichon pubescens (sp - sp), i?r / za media (sol - sp), Poa angustifolia (sp - "sp), Stiapa pennata (sol-" sp), "Ufa / /LUYA (2-3 - "sp), Stachis officinalis (2-3 -" sp, sol), Centaurea scabiosa (2-3 - sp), Delphinium cuneatum (2-3 - sp, sol), Primula veris (sp - cop), Sa/v/a pratensis (sp -»copl), Seiratula heterophylla (un-sp). Two grasses appeared in the steppe areas with periodic mowing: Arrhenaterum elatius, Bromopsis riparia, not listed by V.V. Alekhine and currently found in significant abundance (sp, sor 2). There was a change in the abundance indicators of the main aspecting species in the plots with PKK. Observations of aspects in mowed phytocenoses currently show that the aspects have changed compared to the original ones noted by V.V. Alekhin (1909), Pokrovskaya (1940). Aspects of Adonis vernalis and Pulsatilla patens are observed only in places, in fragments. The aspect of forget-me-not drops out on mowed areas. The aspect of Primula veris and Draba sibirica is well expressed, during the flowering of which, the entire steppe turns yellow (Fig. 20). From the middle of summer, an aspect of Arrhenatherum elatius is observed, the generative shoots of which cover the fading forbs. An analysis of the descriptions according to ecological scales shows that the steppe phytocenoses with PKK have grown and are located on the border between meadow steppes and dry and fresh meadows (Table 1). 9). The currently noted differences arose over 68 years, under the influence of changing environmental conditions, after the cessation of livestock grazing in these areas, which until 1935 was intensive in spring and autumn after the aftermath, and hay mowing regimes carried out throughout the entire existence of the reserve. The study of mowed steppe phytocenoses shows that Calamagrostis epigeios does not develop in mowed areas, because it develops seeds late and is oppressed, trees and shrubs, Urtica dioica, Cirsium cetisum do not develop, because their seedlings are mowed down. The prevailing associations with the abundant representation of Festuca valesiaca in the first stages of development were associated with excessive grazing of cattle on the steppe before its conservation, because. it is known that fescue is a plant that endures grazing better than all other grasses noted in the phytocenoses of the Streletskaya steppe. With the introduction of haying and grazing, conditions were created for the development of rhizomatous and loose shrub grasses, which were previously eaten by animals, were oppressed and depleted. Rhizome and loose shrub grasses are larger and competitively stronger than Festuca valesiaca, which, located in the lower 102 tiers, is deprived of renewal by rhizomes, propagated by seeds, and has a life expectancy of up to 30 years. The wide and significant presence of ryegrass in modern communities is also associated with its biological characteristics and modern methods of hay harvesting. This is a tall loose-grained cereal up to 170 cm tall, well leafy, the seeds ripen before hay is harvested, and modern ways harvesting hay contributes to its distribution, as we mentioned earlier. Preservation of species diversity and species richness in phytocenoses with periodic mowing shows that the removal of grazing after afterlife is less important in community changes than the creation of an absolutely reserved regime, which leads to major changes in the ecological systems of steppe phytocenoses. The direction of succession associated with protection regimes and changes in environmental conditions can be explained by the biological characteristics of dominant plants, dominants and edificators against the background of an increase in moisture observed over the past 20 years, which is noted by A.A. Vlasov (2002).
STRUCTURE OF PHYTOCENOSES
SIGNIFICANCE OF STUDYING THE STRUCTURE OF PHYTOCENOSES
Considering the formation of phytocenoses, we saw that they arise as a result of plant reproduction under conditions of complex interactions between plants and the environment, between individual individuals and between plant species.
Therefore, phytocenosis is by no means a random set of individuals and species, but a natural selection and association into plant communities. In them certain types plants are placed in a certain way and are in certain quantitative ratios. In other words, as a result of these mutual influences, each phytocenosis receives a certain structure (structure), both in its aboveground and underground parts.1
The study of the structure of phytocenosis gives a morphological characteristic of the latter. It has two meanings.
First, the structural features of the phytocenosis are most clearly visible and can be measured. Without an accurate description of the structure of phytocenoses, neither their comparison nor generalizations based on comparison are possible.
Secondly, the structure of a phytocenosis is the design of mutual relations between plants, an ecotope and the environment of a phytocenosis under given conditions of a place and at a given stage of development. And if so, then the study of the structure makes it possible to understand why the observed phytocenosis developed the way we see it, what factors and what interactions between them were the cause of the phytocenosis structure we observed.
This indicative (or indicator) value of the structure of phytocenoses makes its study the first and most important task in geobotanical research. It is by the floristic composition and structure of the phytocenosis that the geobotanist determines the quality of soils, the nature of local climatic and meteorological conditions, and establishes the influence of biotic factors and various forms of human activity.
The structure of phytocenosis is characterized by the following elements:
1) floristic composition of phytocenosis;
2) the total number and mass of the plant population of the phytocenosis and the quantitative relationships between species and groups of species;
3) the state of individuals of each species in a given phytocenosis;
4) the distribution of plant species in the phytocenosis and the division of the phytocenosis into its structural parts based on it.
The distribution of plant species in a phytocenosis can be considered from the side of their distribution in the space occupied by the phytocenosis, and from the side of distribution in time. Distribution in space can be considered from two sides: firstly, as a vertical distribution - a longline (or synusial) structure and, secondly, as a horizontal one, otherwise called addition and manifested in the mosaic of phytocenoses; distribution in time manifests itself as a change of synusia at different times.
FLORAL COMPOSITION OF PHYTOCENOSIS
Floristically simple and complex phytocenoses
According to the number of species that make up the phytocenosis, floristically simple and floristically complex phytocenoses are distinguished:
simple - from one or a few species, complex - from many species. An extremely simple phytocenosis should consist of individuals of one plant species (or even one subspecies, variety, one race, ecotype, etc.). There are no such phytocenoses under natural conditions or they are extremely rare and occur only in some completely exceptional environment.
Only in artificial pure cultures of bacteria, fungi and other plants are their extremely simple groupings obtained. Under natural conditions, there is only relative simplicity or low floristic saturation of some phytocenoses. Such, for example, are natural “pure” thickets of certain herbs (thickets of sharp sedge, canary grass, southern reed, etc.), crops almost free from weeds, dense young growth of forests, etc. We see them as extremely simple only as long as habitually we take into account only the higher plants. But as soon as we remember that in any such thicket there are many species of lower plants - bacteria and other microphytes that are in interaction with each other and with this thicket and with the soil - the relativity of its floristic simplicity becomes obvious. Nevertheless, in a geobotanical study, they can be considered relatively simple, since higher plants in them determine the main and visible features of the structure, and microorganisms are still rarely taken into account in such studies (although taking into account their activity is absolutely necessary for understanding many aspects of the life of a phytocenosis from higher plants ).
Floristically complex phytocenoses are the more complex, the more species they have and the more diverse they are in ecological and biological terms.
(1929) distinguished phytocenoses:
from one type aggregation; from several ecologically homogeneous species - agglomerations; from several aggregations or agglomerations capable of existing separately, - semi-association; from similar aggregations and agglomerations, but capable of existing only together - associations.
Grossheim interpreted these types of phytocenoses as successive "steps" in the development of the vegetation cover, its complication. However, the terms he proposed have not received general acceptance in the sense indicated.
An example of a very large floristic complexity, or saturation with species of higher plants, are tropical phytocenoses. moist forests. In the forests of the tropics West Africa on an area of 100 m2 found from above 100 species of trees, shrubs and herbs, not counting the huge number of epiphytes growing on trunks, branches and even leaves of trees. In the former USSR, the subtropical forests of the humid regions of Transcaucasia and the lower belts of the southern part of the Sikhote-Alin in the Primorsky region are floristically rich and complex, but they still do not reach the complexity of tropical rainforests. Herbaceous communities of the Central Russian meadow steppes are complex, where 100 m2 there are sometimes up to 120 or more species of higher plants. In a complex (with undergrowth) pine forest in the suburbs of Moscow on an area of 0.5 ha 145 species were found (8 species of trees, 13 species of undergrowth shrubs, 106 species of shrubs and herbs, 18 species of mosses). In taiga spruce forests, floristic saturation is less.
Causes of differences in the floristic complexity of phytocenoses
What determines the degree of floristic complexity, or saturation, of phytocenoses? What features of the environment indicate to us the floristic richness or, conversely, the poverty of the phytocenosis? There are several reasons for this or that floristic complexity, namely:
1. General physical-geographical and historical conditions of the area, on which a greater or lesser diversity of the flora of the region depends. And the richer and more ecologically diverse the flora of the area, the greater the number of candidate species for any territory in this area, the greater the number of them, under favorable conditions, can coexist together, in one phytocenosis.
The floristic saturation of the Central Russian meadow steppes is replaced in the more arid southern and southeastern regions by a much lower floristic richness of the feather grass steppe phytocenoses. Central Russian oak forests are floristically more complex than coniferous northern taiga forests. Phytocenoses in the lakes of the Kola Peninsula are floristically poorer than similar phytocenoses in more southern lakes. In the Arctic, where the flora of higher plants is poor, the complexity of individual phytocenoses is also small.
2. Edaphic habitat conditions. If the soil conditions are such that they allow the existence of only one or a few species of local flora that are most adapted to these conditions, then only they form phytocenoses (the latter, therefore, are relatively simple even in areas with very rich flora). Conversely, if the ecotope satisfies the requirements of many plant species, they form more complex phytocenoses.
Almost pure thickets of sharp sedge or reeds, saltwort thickets on salt marshes, or pine forests with a carpet of cladonia on the soil, therefore, consist of very few species, because the waterlogging inherent in these places is too great, or too much poverty or dryness, or salinity of the soil, etc. exclude all other plants. In areas of water meadows that annually receive thick deposits of sand or silt, phytocenoses are distributed from one or a few species that can survive with the annual burial of their renewal buds by a thick alluvium deposit. Such are the undergrowth of the present (Petasitesspurius), awnless bonfire (Bromopsisinermis), ground reed grass (Calamagrostisepigeios) and other plants with long rhizomes capable of quickly growing through the sediment that buries them. On soils very rich in nitrates, single-species thickets of couch grass are sometimes formed. (Elytrigiarepens) or nettle (Urticadioica) and other nitrophils.
Thus, any extreme conditions lead to the formation of phytocenoses of the simplest structure. In the absence of such extremes, more complex phytocenoses are obtained, which we see in the example of most forest, meadow, steppe and other phytocenoses.
3. Sharp variability of the ecological regime. The sharp variability of the water regime increases the floristic saturation and ecological heterogeneity of the phytocenosis flora especially noticeably. Thus, the spring moistening of the feather grass steppe causes an abundance of ephemera and ephemeroids, ending the growing season before the onset of a dry and hot summer. In water meadows, spring moisture ensures the growth of moisture-loving species, summer dryness limits them, but it is favorable here for species that grow moderately demanding on moisture, but endure spring waterlogging. As a result, a large number of ecologically heterogeneous species are observed, together forming a complex phytocenosis. In some floodplain meadows (the Ob river, the middle Volga), moisture-loving (hydrophytes) grow literally side by side, for example, a swamp (Eleocharispalustris), and many mesophytes, and even xerophytes.
The variability of the light regime can have a similar meaning. In oak-broad-leaved forests, annually during the growing season, two periods are replaced, different in lighting: in spring, when the leaves of trees and shrubs that have not yet blossomed do not prevent the penetration of light, many light-loving plants grow and bloom - Siberian blueberry (Scitlasibirica), corydalis (Corydalis) and other spring ephemeroids, the later period - the period of shading by developed foliage - is used by other, shade-tolerant plants.
4. Biotic factors. The most obvious example is the effect of wild and domestic animals on vegetation. Livestock grazing changes the soil and soil conditions and the species composition of plant groups: the soil either becomes compacted or, conversely, loosens, hummocks appear, animal excrement fertilizes the soil - in short, the air-water, thermal, and salt regimes change. This entails a change in vegetation. Grazing also directly affects plants: grazing and mechanical trampling produce a selection of species that endure such an impact.
Grazing in combination with varying degrees of influence of climate, soil, and initial vegetation can contribute either to the complication of initial phytocenoses or their simplification. For example, when grazing on wet soil, hummocks form, and the hummocky microrelief increases the heterogeneity of the environment and the set of species. When grazing animals on moderately moist soil, turfing is often disturbed, and repeated grazing weakens the dominant plants, which contributes to the growth of pasture weeds, i.e., the set of phytocenosis species increases. Conversely, intensive grazing on dense, soddy soil makes it possible for only a few resistant species to thrive. Therefore, many previously floristically complex meadow and steppe phytocenoses, now, with their strong pasture use, have turned into extremely simplified ones, consisting of a few species. Mouse-like rodents inhabiting various phytocenoses and loosening the turf and surface layers of the soil with their moves contribute to the settlement of many plants and thus create and maintain a more complex structure of the vegetation cover.
5. Properties of some components of phytocenosis. For example, on abandoned arable lands with fairly rich soil, almost pure thickets of creeping wheatgrass often grow in 1–2 years. This plant, spreading rapidly by means of long, branched rhizomes, captures the arable land sooner than many other plant species that can grow here as well as wheatgrass, but settle more slowly. The latter are only gradually introduced into the couch grass phytocenosis and complicate it.
Similar and for the same reason, pure thickets of willow-tea and ground reedweed grow in forest fires. Here, as well as on an abandoned arable land, there are all conditions for the growth of many species, i.e., for the formation of complex phytocenoses. But these two species, having great energy and seed and vegetative reproduction, spread faster than others. The penetration of other species into such thickets is usually delayed by the saturation of the soil with rhizomes and roots of the pioneer species, as well as by the density of their herbage. Such thickets, however, quickly thin out, since the species that form them are demanding on the looseness of the soil (aeration), and sometimes on its richness in nitrates; their growth compacts the soil, impoverishes it, which leads to self-thinning.
There are also plants that are capable of creating conditions for a relatively poor flora coexisting with them and supporting them for many tens and hundreds of years. Such is the spruce. In a spruce mossy forest, strong shading, air and soil humidity, soil acidity, an abundance of slowly and poorly decomposing litter, and other features of the air and soil environment caused by the spruce itself allow the settlement under its canopy of a few other species of higher plants adapted to the spruce forest environment. It is worth taking a look at a clearcut in the middle of such a forest, in order to be convinced by the abundance of many species that are absent in the surrounding forest that this ecotope is fully suitable for them. This means that the small floristic saturation of the spruce forest is the result of the influence of its environment.
The environment of a plant community can also complicate its floristic composition. For example, various forest plants appear under the canopy of forest plantations in the steppe over time, and initially simple plantations turn into more complex forest phytocenoses.
Thinking about the reasons for the floristic richness or poverty of phytocenoses, we see that all of them can be reduced to three groups of factors: firstly, to the influence of the primary environment (ecotope), secondly, to the influence of the environment of the phytocenosis itself (biotope) and, in thirdly, to the influence of biotic factors. These reasons operate within the richness or poverty of the flora of the area and its ecological diversity, determined geographically, historically and ecologically.
Finding out the reasons for this or that floristic saturation of each phytocenosis, we thereby find out its indicative value for characterizing ecological conditions and the degree of their use by plants.
The degree of floristic saturation indicates the completeness of the use of the environment by phytocenosis. There are no two species that are completely identical in their relation to the environment, in its use. Therefore, the more species are in the phytocenosis, the more versatile and fuller the environment occupied by it is used. And vice versa, a phytocenosis consisting of one or a few species indicates an incomplete, one-sided use of the environment, often only because there were no other species in the local flora that could grow here. For example, a forest without shrubs uses the energy of solar radiation to a lesser extent than a forest with shrub undergrowth. The undergrowth uses rays that pass through the upper canopy of the forest. If there is also grass or green mosses under the undergrowth, then they in turn use the light passing through the undergrowth. In a forest without undergrowth, grasses and mosses, all the light penetrating through the crowns of trees remains unused.
If we recall that green plants are the only natural agents that convert the energy of solar radiation into organic matter with a huge supply of chemical energy, it becomes clear how important it is that plant communities be of the most complex composition.
The floristic composition of phytocenoses is sometimes increased artificially. This is achieved by oversowing or planting other plant species in phytocenoses, even alien to the local flora, but suitable for given conditions. Sometimes, for the same purpose, they change the ecological and phytocenotic conditions.
In Germany and Switzerland, spruce forests are converted into more profitable mixed forests by planting other tree species (beech) in them. Instead of single-species crops of fodder cereals and the same crops of legumes, they prefer to cultivate mixed cereal-legume crops, not only because they are more appropriate for improving the soil and the quality of hay, but also because their use of field resources and their productivity are greater than pure crops.
Identification of the complete flora of phytocenosis
All plant species that make up the phytocenosis depend on the conditions of existence, and each species contributes its share to the formation of the phytocenosis environment. The more fully known the floristic composition of the phytocenosis, the more data the researcher has for judging environmental factors.
Finding the full composition is not an easy task even for an experienced florist. Some species of higher plants present in the phytocenosis at the time of observation can only be in the form of rhizomes, bulbs or other underground organs, as well as in the form of seeds in the soil, and because of this they often go unnoticed. It is difficult to determine the species affiliation of seedlings, juvenile forms. Recognition of species of mosses, lichens, fungi requires special training and skills, and the determination of the microflora of a phytocenosis requires a special complex technique.
When studying the floristic composition, as well as when studying other signs of the structure of a phytocenosis, it is necessary that the phytocenosis occupies an area sufficient to reveal all its features. Even the completeness of accounting for the floristic composition depends on the size of the recorded area. If there is, for example, a herbaceous phytocenosis of several dozen plant species, then by choosing a site of 0.25 m2 to take into account the floristic composition, we will find several species on it. Having doubled the site, we will find on it, in addition to those already noted, species that were absent on the first one, and the general list of species composition will be replenished. With a further increase in area to 0.75-2 m2, etc., the list of species will increase, although with each increase in area, the profit of the number of species in the general list becomes smaller. By increasing the sites to 4 m2, 5 m2, 10 m2, etc., we notice that on sites larger, for example, 4 m2, new replenishment of the list of species does not occur or almost does not occur. This means that the area of 4 m2 taken by us is the minimum area for revealing the entire species composition of the studied phytocenosis. If we had limited ourselves to a smaller area, it would have been impossible to fully identify the species composition. There are areas of vegetation cover that differ from neighboring ones, but are so small that they do not reach the area of detection of the floristic composition of the phytocenosis to which they belong. These sites are fragments of phytocenoses.
The term "area of detection" is proposed. Foreign authors use the term "minimal area".
The area of identification of the species composition of phytocenoses of various types is not the same. It is not the same for different parts of the same phytocenosis. For example, for a moss cover on the soil in a forest, 0.25–0.50 m2 is often enough to meet all types of mosses present in a given phytocenosis in such a small area. For herbaceous and shrub cover in the same phytocenosis, a large area is required, often at least 16 m2. For a forest stand, if it consists of several species, the detection area is even larger (from 400 m2).
In various meadow phytocenoses, the minimum area of detection of the floristic composition does not exceed or barely exceeds 100 m2. Finnish authors consider an area of 64 m2.
Bearing in mind the identification of not only the floristic composition of a phytocenosis, but also various other structural features, in the practice of Soviet geobotanists, when describing a complex forest phytocenosis, it is customary to take a sample area of at least 400–500 m2, and sometimes up to 1000–2500 m2, and when describing herbaceous phytocenoses - about 100 m2 (if the area of the phytocenosis does not reach such sizes, it is described in its entirety). Moss and lichen phytocenoses often have an area of detection not more than 1 m2.
