Articles

For the purposes of ecological monitoring, the features of living ground cover and forest floor in spruce stands within Moscow urban territory were studied. Using ecological scales by Nitsenko, Ramensky, Ellenberg and Landolt, let to consider, that ruderalization of living overground cover is a result of recreation. Independently of spruce forest type, the absence of undergrowth results in increasing light penetrating and increasing species quantity. Variety of ecological spaces is a result of moderate trampling, which is mostly expressed in between-crown spaces. Hight trophy index by L.G. Ramensky is a result of increased weediness of overground cover. It is shown, that living overground cover characterizes the variety of tree layer and the level of anthropogenic impact on phytocenosis.

The forest floor in urban spruce stands is sensitive to changes in functioning conditions and can be used for ecological monitoring. Availability of forest floor studying and simplicity of parameter estimation allows getting information about organic matter accumulation in express-regime under various degrees of anthropogenic impact on urban ecosystems.

Within the system of trunk, crown and open space, the simplification of litter structure and decreasing organic matter total deposit are observed — this can be considered an invariant process.

Maximal uniformity of coverless spaces litter, composed by needles and branches, results from absence of living overground cover, in combination with low recreation in these spaces. This fact let to conclude, that coverless spaces are able to be used as most important objects for comparing spruce ecosystems with different overground cover. Two groups of indexes, characterizing structure-functional litter organization, are proposed. Indexes, characterizing structural litter organization, include the total deposit of litter and L horizon deposit. Indexes, characterizing functional litter features, include deposit and proportion of detritus as well as the same for easy-decomposed components, ratio of thickness (deposit) of L horizon and F horizon. The peculiarities of long-term spatial functioning are characterized by litter typology in the system trunk-crown-open space.

Spatial and temporal variability of the vegetation index were investigated in the vicinity of the anthropogenic source of heavy metals. The analysis of the special points of the theoretical equation of the dependence of the concentration of photosynthetically active biomass on the resulting concentration of pollutants in the soil revealed the maximum permissible concentration of heavy metals in the soil. The results of its determination in the northern forest-steppe under the current level of anthropogenic pressure, according to MODIS materials, amounted to 12,3, according to Sentinel-2 — 12,5 mg/kg, respectively. A method for generalizing the macrokinetic patterns of the response of the living organisms to anthropogenic impact is proposed. The results of the environmental risk assessment showed that the probability of exceeding the threshold concentration is 74%.

Based on the five-level quality scale and the indicator of soil state, the quality of soils and vegetation cover was ranked. The areas of the same resistance of soils and vegetation to the action of pollutants in the plant impact zone were mapped. Territories near the plant mostly correspond to the I and II categories of soil quality. The natural protection zone of the enterprise is allocated, and background territories are defined.

We studied the soils and vegetation cover of tombolo – bridges between the mainland and small islands on the coasts of the White and Baltic Seas. Tombolo are characterized by complex dynamics of sedimentation that determines a high level of heterogeneity of soils and associated vegetation cover. At the Kolezhma plot on the White Sea coast, ground- and surface-gley marsh soils are formed. Vegetation corresponds to marsh meadows of the lower and middle levels, and varies depending on salinity, acidity level and soil texture. At the Gakkovo plot on the Baltic Sea coast, soils are characterized by greater uniformity; in general, they have a sandy texture. The influence of the Baltic Sea on the soil and vegetation cover is significantly lower than that of the White Sea due to the weakly pronounced tidal dynamics of the Baltic Sea.

The article discusses the processes of transition to the aqueous phase and uptake from it by plants of stable (Cd) and radioactive (¹⁰⁹Cd) isotopes. Regularities of the distribution of Cd/¹⁰⁹Cd between different forms of their chemical compounds in the soil were revealed by means of sequental extraction procedure (SEP) according to the Tessier-Förstner method. It was shown that content of labile and conditionally labile forms of compounds (fraction F1-F3) of stable Cd was 1,2–1,8 times less than that of radioactive ¹⁰⁹Cd and, conversely, 2,4–5,3 times more fixed conservative forms of metal compounds (fraction F4-F6). The Cd concentration, ¹⁰⁹Cd activity concentration, distribution and concentration coefficients of natural Cd and ¹⁰⁹Cd radionuclide, accumulation and removal of metal by plants were evaluated. Values of enrichment coefficients of natural (stable) Cd contained in sequentially extracted chemical fractions by ¹⁰⁹Cd radioisotope were determined, the value of stock of labile cadmium compounds in studied soil was calculated. Based on the results of solid-state ¹³C NMR spectrometry, the qualitative composition of high-molecular organic compounds of the soil solution was determined and their ability to specifically sorb heavy metal cations was assessed.

An analysis of the isotopic composition of vegetation and organic matter of permafrost burozems in the south of the Vitim Plateau was carried out. The soil profile is characterized by a pronounced uneven distribution of carbon. The main part of carbon reserves is concentrated in the humus-accumulative horizon, down the profile — much lower.

Vegetation on burozems belongs to the C-3 type of photosynthesis. In legumes, forbs, and semi-shrubs, the aboveground parts are somewhat depleted in the ¹³C isotope compared to the underground ones. In trees, the content of 13C in branches, needles, and leaves differs slightly.

The isotope composition of carbon in the upper horizons of soils depends on the type of phytocenosis and has close values to δ¹³C in dominant plants. With depth, carbon isotope fractionation shows a clear vertical differentiation along the soil profile.

The carbon of humic acids in soils from the humus-accumulative horizon and from cryogenic fissures slightly differs in isotope composition. The composition of stable carbon isotopes of humic acids in the soil profile remains approximately at the same level. These data indicate the similarity of the processes of humic acids formation in the upper soil layers and in humus pockets.

Natural ¹³C abundance of different organic matter (OM) pools of Haplic Chernozem (Streleskaya steppe plot of the Central Chernozemic State Biospheric Reserve) isolated by granulo-densitometric fractionation was studied. Natural variations of the ¹³C/¹²C ratio (δ¹³C) allowed to confirm the sequence of OM decomposition in soils, which follows a continuum from fresh and partially decomposed organic materials in the discrete OM (Free and Occluded) to significantly/completely processed in the mineral-associated OM (Clay and Res). This is reflected in the increase of the δ¹³C value during passing from discrete to mineral–associated OM. All studied OM pools are subjected to microbial processing, but in different extent. Free OM, despite the fact that it consists of well-recognized plant material, is not always the most fresht and most undecomposed organic material. The «lighter» isotope signature of occluded OM as compared to free OM, despite its obvious higher degree of microbial processing, may be a consequence of its physical protection in microaggregates (unstable under the sonication) within the soil structural units. The most microbial processed mineral-associated organic material (Clay and Residue fractions) is characterized by the «heaviest» isotopic signature. The isotopic composition of carbon in the whole soil is mainly determined by the Residue fraction due to its quantitatively domination in the bulk soil.

The conceptual scheme allows to quantify the carbon (C) fluxes of in the OM pool / soil system. It was revealed that the main C fluxes in the OM pools go from the Free OM to the Residue fraction through unstable under the sonication microaggregates. The most probable C flows into the whole soil — unstable under the sonication microaggregates, as well as the Residue fraction, which are characterized by the lowest Δ¹³C values (difference between Δ¹³C of «sourse» and «product»).