Thermal Impact of Gas Flares on the Biological Activity of Soils

Global warming can lead to a significant transformation of the structure of terrestrial ecosystems and changes in the mode of functioning of their components. In this connection, studies of soil respiration, particularly of the biological activity of soils under forest exposed to warm impact of flaring flare are of scientific and practical interests. A long-term experimental plot was established in a lichen pine forest on the Albic Podzols (Arenic) (Khanty-Mansi Autonomous Area-Yugra). Sampling and measurements were carried out in the areas at the distances of 70, 90, and 130 m from the flare with the strong, moderate, and weak heating effects, respectively. In the zone of the maximum heating effect, the soil temperature was by 1.3°C higher, and the rate of CO₂ emission from the surface in situ was greater by 18% compared to the zone with weak impact of the flare. Along with increasing CO₂ emissions, organic matter accumulated due to increasing the stable pool. The parameters of the microbial biomass, basal respiration, and the input of labile organic matter pool increased with the distance from the flare.     

Transformation of the organic matter in an agrogray soil and an agrochernozem in the course of the humification of corn biomass

The transformation of the organic matter in the course of corn residues humification in an agrogray soil and an agrochernozem was studied in long-term experiments using the method of solid-phase ¹³C-nuclear magnetic resonance spectroscopy. The humification of the plant residues was found to be accompanied by a decrease in the content of the O-alkyl fragments comprising polysaccharides and polypeptides, an increase in the unsubstituted alkyds content, and by the relative accumulation of aromatic fragments and carboxyl groups. The most strongly transformed pool of the organic matter, as compared to the initial plant residues, was the humic acids with their maximal content of aromatic and carboxyl functional groups and the minimal content of O-alkyls. The chemically stable aromatic fragments were concentrated not only in the pool of humic acids; their content was 64–89% of the pool of the aromatic fragments identified in the soil organic matter. Therefore, to assess the stable pool, the distribution of the functional groups is necessary to be analyzed not only in the humic acids but also in the whole soil organic matter.     

Genetic characteristics of Large White and Yorkshire pigs of various provenance with the use of DNA markers

Comparative characteristics of the gene pool of six groups of Large White pigs being raised at breeding enterprises of Russia and four groups of Austrian, Canadian (two groups), and French Yorkshire pigs with the use of DNA microsatellites (DNA MSs) are given. The high informativeness of DNA MSs for characterizing the genetic diversity of the investigated pig groups is shown. A higher level of heterozygosity, calculated on the basis of DNA MSs, in Large White pigs compared to Yorkshire pigs is reliably established. An analysis of the genealogical relations didn’t reveal the formation of clusters according to the breed principle, which indicates commonality of ancestors in the majority of investigated pig groups.     

Carbon dioxide emissions from agrogray soils under climate changes

The effect of droughts and drying-wetting cycles on the respiration activity of agrogray soils was studied in field and laboratory experiments. The alternation of drought periods and rains during the vegetation season did not increase the annual emission of CO₂ from the soils under a sown meadow and an agrocenosis. In laboratory experiments, the wetting of dried soil released 1–1.5% of C_org with a high decomposition constant n × 10⁻¹ day⁻¹ and a very short renewal time (2.1–2.4 days); therefore, an abrupt change in the wetting conditions did not intensify the loss of soil carbon under field conditions.     

Soil respiration and carbon balance of gray forest soils as affected by land use

 Soil respiration was measured by closed chamber and gradient methods in soils under forest, sown meadow and crops. Annual total soil respiration determined with the closed chamber method ranged from 180 to 642 g CO₂-C m^–2 year^–1 and from 145 to 382 g CO₂-C m^–2 year^–1 determined with the CO₂ profile method. Soil respiration increased in the order: cropland<sown meadow<forest. The C balance calculated as the difference between net primary production (sink) and respiration of heterotrophs (source) suggested an equilibrium between the input and output of C in the cropland, and sequestration of 135 and 387 g CO₂-C m^–2 year^–1 in the forest and meadow, respectively. Received: 1 December 1997     

Distribution of stable carbon isotopes in an agrochernozem during the transition from C3 vegetation to a corn monoculture

The distribution of carbon in an agrochernozem??s profile was studied by the natural ¹³C abundance method during the C₃-C₄ vegetation transition and the analysis of the soil phytolith complex under a continuous corn monoculture. A young pool of soil organic matter (SOM) formed during 43 years of monoculture growing was detected by the isotope analysis in the 0-to 60-cm layer, while the analysis of the phytolith complex identified this pool deeper: corn phytoliths were detected in the 0- to 80-cm layer. The maximum size of the young pool was found in the upper soil horizon; it reached 6.4% of the SOM in the 0- to 20-cm layer. The apparent time of the SOM turnover was 635 and 2225 years in the 0- to 20- and 40- to 60-cm layers, respectively. The high values of the mean residence time were related to the low input of plant residues to the soil at the growing of corn for silage and the high initial content of organic carbon in the chernozem. The changes in the isotope composition after the decalcification of the soil to remove carbonates and the variation of the ??¹³C in the corn biomass during the vegetation period significantly affected the calculated value of the mean residence time.     

Determination of root and microbial contributions to the CO<Subscript>2</Subscript> emission from soil by the substrate-induced respiration method

The contributions of root and microbial respiration to the CO₂ emission from the surface of gray forest and soddy-podzolic soils under meadow and forest vegetation were determined in field and laboratory experiments. In the field, a new modification of the substrate-induced respiration (SIR) method was applied. According to this method, the contribution of root respiration was estimated at 41–50% for meadow cenoses and 33% for forest cenoses; similar values were obtained in the course of separate incubation of roots and soil in laboratory (42–57% and 29–32%, respectively) and with the use of the laboratory version of the SIR method (35–40% and 21–31%, respectively). The analysis of difference between the values of root respiration and microbial respiration obtained by the field and laboratory methods for the same experimental plots and the comparison of advantages and disadvantages of these methods made it possible to outline the ways for the further improvement of the field version of the SIR method.     

Carbon balance in the soils of abandoned lands in Moscow region

A quantitative assessment of the carbon balance was performed in gray forest soils of the former agricultural lands abandoned in different time periods in the southern part of Moscow oblast. It was based on the field measurements of the total and heterotrophic soil respiration and the productivity of biocenoses. Geobotanical investigations demonstrated that the transformation of the species composition of herbs from weeds to predominantly meadow plants occurred in five–ten years after the soil was no more used for farming. The amount of carbon assimilated in the NPP changed from 97 g C/m² year in the recently abandoned field to 1103 g C/m² year in the 10-year-old fallow, and the total annual loss of carbon from the soil in the form of CO₂ varied from 347 to 845 g C/m² year. In five years, the former arable lands were transformed into meadow ecosystems that functioned as a stable sink of carbon in the phytomass and the soil organic matter.