I. N. Kurganova

Annual and seasonal CO2 fluxes from Russian southern taiga soils

Annual and seasonal characteristics of CO2 emission from five different ecosystems were studied in situ (Russia, Moscow Region) from November 1997 through October 2000. The annual behaviour of the soil respiration rate is influenced by weather conditions during a particular year. Annual CO2 fluxes from the soils depend on land use of the soils and averaged 684 and 906 g C m−2 from sandy Albeluvisols (sod-podzolic soils) under forest and grassland, respectively. Annual emission from clay Phaeozems (grey forest soils) was lower and ranged from 422 to 660 g C m−2; the order of precedence was arable < grassland < forest. The coefficients of variation for annual CO2 fluxes caused by weather conditions ranged from 18% (forest ecosystem on Phaeozems) to 31% (agroecosystem). The contribution from the cold period (with snow, November—April) to the annual CO2 flux was substantial and averaged 21% and 14% for natural and agricultural ecosystems, respectively. The CO2 fluxes comprised approximately 48–51% in summer, 23–24% in autumn, 18–20% in spring and 7–10% in winter of the total annual carbon dioxide flux.

Updated estimate of carbon balance on Russian territory

The land use system in Russia changed considerably after 1990: 30.2 million ha of croplands were abandoned. Based on the own field investigations that were carried out in abandoned lands of different age (Luvic Phaeozems, deciduous forest zone; Moscow region, 54.50N, 37.37E), it has been shown that after 4.5 yr of abandonment, the former croplands acted as a stable sink of CO2. The net ecosystem production (NEP) in the post-agrogenic ecosystems averaged 245 ) 73g C m-2 yr-1 for the first 15 yr after land use change that corresponds to an estimated 74 ) 22 Tg C yr-1 for the total area of abandoned lands in Russian Federation. Currently, the Russian territory acts as an absolute sink of atmospheric CO2 at a rate about 0.90 Pg C yr-1. Using three different approaches, it was demonstrated that after 1990, the carbon sequestration in Russian soils (0.20 cm layer) has averaged 34 ) 2.2 Tg C yr-1. This soil C forms net biome production (NBP) where carbon lifetime is much longer than in eKyoto forestsf. Thus, the post-agrogenic ecosystems in Russia provide with the additional CO2 sink in NEP and NBP that could annually compensate about 25% of the current fossil fuel emissions in the Russian Federation.

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.

Land-use change and management effects on carbon sequestration in soils of Russia’s South Taiga zone

The impact of land use change and management on soil C sequestration was investigated during the 1980s–1990s on gray forest soils in Pushchino, and on the soddy-podzolic soil in Prioksko-Terrasny Biosphere Reserve, Moscow Region, Russia (54°50ʹN, 37°35ʹE). Mean annual rates of C sequestration after establishment of perennials (layer 0–60 cm) were 63–182 g C m−2 and 22–43 g C m−2 for gray forest and soddy-podzolic soils, respectively. Grassing resulted in higher soil C accumulation than afforestation. Cutting and application of NPK fertilisers increased soil C accumulation, but newly formed soil organic matter was less resistant to decomposition than in unfertilised soil. Preliminary calculations of C sequestration due to abandonment of arable land in Russia since the early 1990s suggest that total C accumulation in soil and the plant biomass could represent about one tenth of industrial CO2 emissions.

Influence of freeze-thaw events on carbon dioxide emission from soils at different moisture and land use

BackgroundThe repeated freeze-thaw events during cold season, freezing of soils in autumn and thawing in spring are typical for the tundra, boreal, and temperate soils. The thawing of soils during winter-summer transitions induces the release of decomposable organic carbon and acceleration of soil respiration. The winter-spring fluxes of CO2 from permanently and seasonally frozen soils are essential part of annual carbon budget varying from 5 to 50%. The mechanisms of the freeze-thaw activation are not absolutely clear and need clarifying. We investigated the effect of repeated freezing-thawing events on CO2 emission from intact arable and forest soils (Luvisols, loamy silt; Central Germany) at different moisture (65% and 100% of WHC).ResultsDue to the measurement of the CO2 flux in two hours intervals, the dynamics of CO2 emission during freezing-thawing events was described in a detailed way. At +10°C (initial level) in soils investigated, carbon dioxide emission varied between 7.4 to 43.8 mg C m-2h-1 depending on land use and moisture. CO2 flux from the totally frozen soil never reached zero and amounted to 5 to 20% of the initial level, indicating that microbial community was still active at -5°C. Significant burst of CO2 emission (1.2–1.7-fold increase depending on moisture and land use) was observed during thawing. There was close linear correlation between CO2 emission and soil temperature (R2 = 0.86–0.97, P < 0.001).ConclusionOur investigations showed that soil moisture and land use governed the initial rate of soil respiration, duration of freezing and thawing of soil, pattern of CO2 dynamics and extra CO2 fluxes. As a rule, the emissions of CO2 induced by freezing-thawing were more significant in dry soils and during the first freezing-thawing cycle (FTC). The acceleration of CO2 emission was caused by different processes: the liberation of nutrients upon the soil freezing, biological activity occurring in unfrozen water films, and respiration of cold-adapted microflora.

Effect of the temperature and moisture on the N2O emission from some arable soils

The effect of the temperature and moisture on the emission of N2O from arable soils was studied in model experiments with arable soils at three contrasting levels of wetting and in a wide temperature range (from −5 to +25°C), including freeze-thaw cycles. It was shown that the losses of fertilizer nitrogen from the soils with water contents corresponding to 60 and 75% of the total water capacity (TWC) did not exceed 0.01–0.09% in the entire temperature range. In the soils with an elevated water content (90% of the TWC) at 25°C, the loss of fertilizer nitrogen in the form of N2O reached 2.35% because of the active denitrification. The extra N2O flux initiated by the freeze-thaw processes made up 88–98% of the total nitrous oxide flux during the entire experiment.

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 Corg 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.

Changes in the organic carbon pool of abandoned soils in Russia (1990–2004)

The assessment of the changes in the organic carbon pool in the soils of the Russian Federation that occurred in 1990–2004 was carried out using approximation, soil-geoinformation, and simulation approaches. As a result of the changes in the system of land use, after 1990, the organic carbon storages in the 0- to 20-cm-thick soil layer could be 196–319 Mt depending on the methodology of the calculation applied and taking into account the abandoned area of 14.8 million ha. As compared to the beginning of the 1990s, the organic matter stock in the former plow layer increased by 1.6–5.8%. The great scatter of the data is mainly related to the incertainty of the estimates of the area of arable soils not used any more in agriculture.

Evaluation of the Rates of Soil Organic Matter Mineralization in Forest Ecosystems of Temperate Continental, Mediterranean, and Tropical Monsoon Climates

The processes of the organic matter (OM) mineralization in forest soils developed under temperate continental (Moscow oblast, Russia), Mediterranean (the central and western parts of Spain), and tropical monsoon (southern Vietnam) climates were studied under laboratory conditions. The potential and specific rates of the OM mineralization (PRmin and PRmin/Corg, respectively), the ecophysiological parameters of the microbial communities status (Cmic, qCO2, and Cmic/Corg), and the sensitivity of the rate of the OM mineralization to the rise in temperature were evaluated by the temperature coefficients (Q10) determined in the humus horizons (0–10 cm, without forest litter). The average values of PRmin for the climatic zones decreased in the following order: Mediterranean (57.1 ± 10.6 mg C/kg per day) > temperate continental (23.8 ± 7.1 mg C/kg per day) > tropical monsoon (10.4 ± 1.6 mg C/kg per day). The lowest resistance of the soil OM to mineralization as evaluated by the PRmin/Corg values was found in the Albeluvisol and Phaeozem of the temperate continental climate and in the Acrisol of the Mediterranean climate. The highest Q10 coefficients were attributed to the OM mineralization in the forest soils of the temperate continental climate. This allowed us to conclude that the observed and expected climate changes with an increase in the mean annual air temperature should lead to the maximum intensification of the OM mineralization processes in the forest soils of northern regions.

Daily and seasonal dynamics of CO2 fluxes from soils under different stands of monsoon tropical forest

The analysis of daily, seasonal, and annual dynamics of CO2 emission from soils under different stands of monsoon tropical tall-tree forest was performed on the basis of field observations conducted at the Russian-Vietnamese Tropical Research and Technology Center of the Russian Academy of Sciences. Under a tropical climate, the main factors responsible for the rate of carbon dioxide emission from the soils are shown to be the soil type and the topographic position of the area studied along with the type of vegetation. Depending on these factors, the rate of CO2 emission from the soils was 65–178 mg C/(m2 h) during the dry season and 123–259 mg C/(m2 h) during the wet season. The daily dynamics of CO2 emissions from the soils of the tropical zone was weakly pronounced in both the wet and the dry season owing to the insignificant diurnal fluctuations of soil temperature. The investigations carried out allowed making an expert evaluation of the annual CO2 fluxes from the soils under different stands of monsoon tropical tall-tree forest in southern Vietnam. They amounted to 900–2000 g C/(m2 yr) depending on the forest type.