No abstract

Annual and seasonal characteristics of CO 2 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 CO 2 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 CO 2 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 CO 2 flux was substantial and averaged 21% and 14% for natural and agricultural ecosystems, respectively. The CO 2 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.

No abstract

No abstract

No abstract

The genesis of hard carbonate nodules in the lowermost horizons (180–200 cm) of arable soils in the southern part of the forest‐steppe region of the Central Russian Upland was associated with a change in soil water regime. The conversion of forest to arable lands was studied in three agro‐chronosequences located on flat interfluves and consisted of undisturbed soils under deciduous forests and arable soils with different durations of agricultural use. Due to arable agricultural activity, the upper soil horizons become drier in the summer during the growing season, whereas the lowermost parts get wetter in the spring and autumn after harvests. As a result, two types of hard carbonate nodules, which differed in morphology, origin and age, formed in the arable soils. The first type of hard nodules had a dense cryptocrystalline fabric in thin sections and colloform morphology viewed under an electron microscope, consisting of calcite with Si, Al and Fe peaks in EDS spectra, and had a 14C‐age from 16,410 ± 200 to 13,570 ± 150 years BP. Their formation occurred due to an ascending of “old” carbonate matter in colloidal suspensions through capillary pores from parent rocks in the periods of strong heating of the soil surface; these nodules had an evaporative origin. The second type of hard nodules consisted of crystalline pure calcite and had a 14C‐age of < 4,500 years BP. They had a hydromorphic genesis and developed in periods of water stagnation in the deep horizons and can be considered to be markers of a seasonal hydromorphism of arable soils in the studied area. Highlights The conversion of forest to arable lands resulted in a change of soil water regime followed by the formation of two types of hard nodules The uplifting of calcite colloidal solutions/suspensions from parent material enriched newly formed hard nodules with “old” 14C The seasonal stagnant water in the lowermost soil horizons caused hard nodule recrystallization and rejuvenation by “young” 14C from organic acids and atmospheric CO2.

No abstract

No abstract