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Impact of litter burning on alpine <i>Festuca varia</i> grasslands of the Northwestern Caucasus

Fires play an important role in structure and function of terrestrial ecosystems, but their long-term impact on the composition and structure of plant communities in humid high mountain regions remains almost not studied. At the most dry alpine grasslands, dominated by a dense-tussock grass Festuca varia, with substantial accumulation of non-decomposed litter, the 23-years long experiment with regular (every two years) litter burning was established. The composition of plant community changed significantly. The mortmass (mass of litter), aboveground vascular plant biomass and relative abundance of dominants decreased substantially. In aboveground biomass the proportion of grasses decreased and that of forbs increased. The shoot numbers of Anthemis cretica, Campanula collina, Deschampsia flexuosa, Festuca ovina, Nardus stricta, and Veronica gentianoides increased after burning. Two-fold increase of alpha-diversity of vascular plants was observed on plots with burning treatment, it was twice as high as initial value, and was significantly higher than the values in the control plots. Long-term burning did not substantially change mean P, Ca and Mg content in the biomass of the most of studied species, only K content decreased in some species, while Mg content increased in Festuca varia and Nardus stricta. The increase of P and Mg content in the mortmass was observed. During long-term burning, weak soil acidification and the decrease of Ca content, as well as strong decrease of nitrogen content and the intensity of nitrogen transformation processes were observed. Generally, the observed patterns were similar to those in other studied herb communities, however, the decrease of K content during the regular burning was not reported earlier.

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Integral effect of a non-centralized biosystem parts interaction with the example of major hydroplasma flow formation in the shoots of colonial hydroid <i>Dynamena pumila</i> (L., 1758)

The emergence of the main hydroplasmic flows (HFs) in the shoot of colonial hydroids (Hydrozoa), flowing from it into the stolon and capable of transporting food particles along stolons to the opposite end of the non-centralized organism, is described. We developed a simple method for minute-by-minute visual registration of the direction of particles movement in hydroplasm in each shoot shaft module for 1.5 hours. The HFs entering the shoot are shown to be rhythmic (15.1 ± 5.0 min), but if the outgoing HFs are usually filled with food particles, the returning HFs, as a rule, contain few particles. There is more chaos in the pulsations of hydrants on the shoot than in the stem of the shoot, i.e. the period of receipt of HF from hydrants to the stem of the shoot varies significantly. Previously, it has been assumed that outgoing HFs are formed only under the influence of incoming ones, as a response to coenosarc stretching when hydroplasma enters the shoot (under the pressure of other pulsators in the colonial organism). However, it turned out that from the appearance of the incoming to the beginning of the outgoing HF, 5 minutes elapsed as an average. During this time, hydroplasma fills not only the stem of the shoot, but also the hydrants, which contract in response, although not simultaneously. The hydrants squeeze out the hydroplasma during compression into the stem of the shoot, after which the coenosarc of the shoot begins to shrink. It turned out that when taking into account the pulsations of hydrants for 3 minutes, a clear periodicity is registered, coinciding with the periodicity of HF emanating from the shoot, resulting from compression of the coenosarc of the stem. At the same time, hydroplasma cannot enter the hydrants until the end of the long phase of their compression. Otherwise, the movements of the hydroplasma would be limited only by the escape space. Thus, in a non-centralized system such as colonial hydroids organism, the coordination of pulsations of hydrants and coenosarc occurs with significant backlash. In the coenosarc, as a whole, the pulsations are rhythmic with minor fluctuations, while the hydrants are sources of many little rhythmic pulsations (with large variations in the period).Therefore, the contribution of hydrants to the formation of the main HF does not appear at once, but for several minutes in the interval between the incoming and outgoing flows.

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Ecological-parasitological method in studies of population biology of beaked redfish <i>Sebastes mentella</i> (Scorpaeniformes: Sebastidae) in the Irminger Sea

The results of the analysis of the data set obtained in course of long-term studies of the population biology of beaked redfish Sebastes mentella are used as an interdisciplinary approach in the study of its geographical, biotopic, ontogenetic and phylogenetic features, population structure in the pelagic zone of the Irminger Sea and the adjacent bathyal zone of Greenland and Iceland. The approach is based on the ecological-parasitological method, which involves the use of data on the composition of parasite communities and the occurrence of their individual species as biomarkers for understanding the features of the hydrobionts ecology. The results obtained, which include information on the spatial distribution, functional subdivision of the area, ontogenetic migrations, maturation and growth rate, underwater marking, phenetic, genetic and other features of beaked redfish, made it possible to identify the conditions for divergent formation and significant isolation of its pelagic and benthic groupings, constituting the North Atlantic population. The colonization by this species of great depths of the oceanic pelagial and the near-bottom layer of the bathyal, accompanied with an increase in the rate of sexual maturation and migratory activity in the pelagial, characterizes the direction of the current stage of its phylogenesis. The unity of the pelagic grouping of beaked redfish in the vast water area and throughout the depth of its distribution in the Irminger and Labrador seas is substantiated. It is shown that significant differences in infestation rate between males and females of beaked redfish, stable in time and space, with the only species-specific parasite (the copepod Sphyrion lumpi), serve as a phene of the pelagic grouping of the North Atlantic population of the host.

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Size-morphological structure and ecological strategies of prokaryotoplankton in a large mountain lake Sevan (Armenia)

The dynamics of the size-morphological groups of heterotrophic prokaryotoplankton of the largest freshwater reservoir in the Caucasus, Lake Sevan (Armenia) has been studied, which makes it possible to explain its spatio-temporal organization and succession. The lake is characterized by an alternation of stable and unstable periods of existence of hydrobionts due to abrupt changes in environmental conditions, mainly caused by anthropogenic impacts. In the community of planktonic prokaryotes of the lake, the following size-morphological groups were distinguished: small cocci and coccobacilli, small rods and vibrios, medium-sized cocci and coccobacilli, large rods and vibrios, filaments, as well as cells associated with detrital particles. The main contribution (on average 55.5%) to the formation of the prokaryotoplankton biomass of the lake was made by small rods and vibrios. The biomass of each of the groups fluctuated in time and space within relatively narrow limits, and the development of the groups occurred in close relationship with each other. Apparently, different size-morphological groups of prokaryotes are adapted to exist within similar ecological and phylogenetic niches, and jointly and consistently perform common functions in the mineralization of organic matter and trophic interactions in the lake. At the same time, these groups implement various ecological strategies that can be successful at different periods of the ecosystem’s existence.

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The pattern of natural variability of palynomorphological features with the example of some <i>Nierembergia</i> and <i>Bouchetia</i> species (Solanaceae) and natural system of bio-variety

On the example of pollen morphological features of 8 species of Nierembergia and 2 species of Bouchetia (family Solanaceae), the properties of individual variability are described. Most of the studied characters (structure of apertures, ultrastructure of the sporoderm, surface sculpture, dimensions) do not have significant differences at the individual and intraspecific levels; taxonomically significant variability of morphological features of pollen is manifested at the level of the genus and suprageneric groups. The genera differ significantly in the sculpture of the pollen grain surface – striate in Nierembergia and tuberculate in Bouchetia. Pollen contained in one bud, anther or tetrad (fully completed gametophytic generation, where there is no death – all descendants of one ancestor without exception), is considered as an extreme model (maximum completeness with minimum complexity) to study the properties of natural morphological variability and the causes of its occurrence. It was found that pollen characters (sculpture, number and location of apertures) have the same pattern of variability (continuous and transitively ordered series), which embodied at different taxonomic levels in different characters. The natural variability of pollen morphological features is ordered not into a genealogical clade, but into a cline – continuous, geometrically ordered and transitive series (taxon-nonspecific and rank-independent). In this system of parallelisms, homological series are inseparable from non-homological ones, and typical forms, from deviations. The origin of typical and deviant forms cannot be explained separately (typical – genealogically, and deviant – as parallelism, convergence, chance or regularity). The individual variability of pollen forms is geometrically ordered and is not the result of random disturbances, failures of the hereditary program, or pathology. The typical form turns out to be a harmonious part of a geometrically ordered series of pure forms, free from functional and historical connotations. The similarity of pollen forms in these series is determined by their geometry and does not depend on affinity, homology, functionality (improvement, exercise, adaptation). The natural system of pollen forms is formed not by the structure of supposed affinity of supposed taxa (universalia, general concepts, the result of speculation that requires confirmation and admits refutation), but the structure of the observed parallelisms of the variability of individual living bodies. Evolutionary novelty (the current state, the observed variability) arises initially ordered in a pre-established form.

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Seasonal dynamics of shoots growth in <i>Forsythia ovata</i> Nakai plants: Rhythmicity of apical and radial growth

The aim of the study was to establish the type (linear or non-linear) and shape (presence of extremes and trends) of the time dependences of apical and radial growth rates for shoots of two types (branching and formation) in woody plants. The object of the study was an introduced in the Middle Urals ornamental early-flowering shrub species Forsythia ovata Nakai. Seasonal dynamics of morphometric parameters of two types of shoots, which differ in intensity of growth and origin (developing from the apical or dormant buds of the skeletal branch respectively), was examined. Also, there was made an assessment of their relationship with air temperature and precipitation values. Apical and radial growth are accompanied by oscillations of increments. The duration of individual phases of oscillations is about 7 or more days, which makes it possible to attribute this phenomenon to infradian growth rhythms. The weak relationship between the characteristics of the observed oscillations and weather conditions indicates the predominantly endogenous nature of the observed morphogenetic processes. The growth of formation shoots begins 4 weeks later than branching shoots. This delay is apparently related to the time necessary for activation of dormant bud growth. Seasonal dynamics curves of rates and accelerations of the apical and radial shoot’s growth have the shape of previously unobserved oscillations with phases fading in amplitude and changing in duration. The growth ends 1–2 months before the environmental conditions become unfavorable. The oscillations of the growth rate of shoots are apparently associated with the action of two or more differently directed factors, which determine the increase in volume of different segments of the shoot. These factors include the different contribution of cell division and elongation to the change in the geometric dimensions of the apical meristem domains. The main differences in the seasonal dynamics of the apical and radial increments for both types of shoots are: the duration of growth (6–8 and 4 weeks, respectively), the number of extremes, the amplitude and the duration of individual phases of oscillations. Higher amplitudes of the growth rate oscillations in shoots formation compared with branching shoots, cause bigger values of the formation shoots total increments. The dynamic curves of the apical growth rates have two maxima, while those of the radial growth have only one. Each type of growth, despite the delay in the onset of the formation shoots, has the same total duration. The shapes of curves of seasonal changes in speeds and accelerations of shoot growth values are also similar for different types of shoots. These similarities indicate that shoots have the same “programs” of growth regulation, ultimately determined by the genotype. The rhythmic growth of both types of shoots during the season suggests the existence of the relationship in time between the rates of division and growth of cells located in functionally different groups of cells in the apical meristem zone.

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