Soil carbon inventories and carbon-13 on a latitude transect in Siberia

We present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 samples collected in areas of minimally disturbed mature vegetation on freely drained soils (excluding peatlands) on a 1000 km transect along the Yennisey River, central Siberia. Carbon inventories over 0-30 cm depth range widely from 1.71 to 7.05 kg m(-2). While an effect of changing climate or vegetation along the transect cannot be ruled out, the observed differences in SOC inventories are largely the result of variations in mineral soil texture, with inventories in fine-textured soils being approximately double those in coarse-textured soils. The delta(13)C values of SOC in the 0-5 cm interval ranged from - 26.3 to -28.0parts per thousand, with delta(13)C values for the 5-30 cm interval being 0.9 +/- 0.8parts per thousand (1sigma) enriched in C-13 relative to the 0-5 cm samples. The average delta(13)C value for the 0-5 cm interval for all samples was - 27.1 +/- 0.6parts per thousand (1sigma) and for the full 0-30 cm interval the average was -26.5 +/- 0.5parts per thousand (1sigma). In general, delta(13)C values were higher in coarse- textured soils and lower in fine-textured soils. The results of detailed sampling of soils in Pinus sylvestris forest growing on sand near the Zotino flux tower suggest an SOC inventory in these soils of 2.22 +/- 0.35 kg m(-2) over 30 cm and an average delta(13)C value of -26.3 +/- 0.2parts per thousand over the 0- 5 cm depth interval and -25.9 +/- 0.3parts per thousand over 0- 30 cm. Recent burning had no effect on SOC inventories, but clearing has led to an average 25% decrease on SOC inventories from 0-30 cm over 12 yr. Neither burning nor clearing had a discernible effect on the delta(13)C value of SOC

Soil carbon inventories of carbon-13 on a latitude transect in Siberia

We present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 samples collected in areas of minimally disturbed mature vegetation on freely drained soils (excluding peatlands) on a 1000 km transect along the Yennisey River, central Siberia. Carbon inventories over 0-30 cm depth range widely from 1.71 to 7.05 kg m-2. While an effect of changing climate or vegetation along the transect cannot be ruled out, the observed differences in SOC inventories are largely the result of variations in mineral soil texture, with inventories in fine-textured soils being approximately double those in coarse-textured soils. The δ13C values of SOC in the 0-5 cm interval ranged from -26.3 to -28.0‰, with δ13C values for the 5-30 cm interval being 0.9 ± 0.8‰ (1σ) enriched in13C relative to the 0-5 cm samples. The average δ13C value for the 0-5 cm interval for all samples was -27.1 ± 0.6‰ (1σ) and for the full 0-30 cm interval the average was -26.5 ± 0.5‰ (1σ). In general, δ13C values were higher in coarse-textured soils and lower in fine-textured soils. The results of detailed sampling of soils in Pinus sylvestris forest growing on sand near the Zotino flux tower suggest an SOC inventory in these soils of 2.22 ± 0.35 kg m-2 over 30 cm and an average δ13C value of -26.3 ± 0.2‰ over the 0-5 cm depth interval and -25.9 ± 0.3‰ over 0-30 cm. Recent burning had no effect on SOC inventories, but clearing has led to an average 25% decrease on SOC inventories from 0-30 cm over 12 yr. Neither burning nor clearing had a discernible effect on the δ13C value of SOC

Reproductive Characteristics of Thawed Stallion Sperm

The main goal of our study was to determine a set of thawed stallion sperm characteristics that have predictive value for the pregnancy rate (PR) of mares after artificial insemination (AI). DNA fragmentation and survival of sperm during hypothermic storage were studied in addition to routinely determined semen characteristics such as concentration, percentage of motile spermatozoa, and morphology. To estimate DNA fragmentation, a modified hallo assay was applied. Sperm survival was determined within hours as the ability of spermatozoa to maintain progressive motility (PM) during the storage of ejaculate diluted with lactose-chelate-citrate-yolk (LCCY) medium at +4 °C. Strong positive correlation between PR and thawed sperm motility (r = 0.90, p < 0.05) as well as between PR and sperm survival (r = 084, p < 0.05) was revealed. There was also a strong negative correlation between PR and DNA damages in spermatozoa (r = −0.94, p < 0.05). We found no dependence of PR on normal morphology spermatozoa percentage in thawed semen. We concluded that the sperm activity, survival, and DNA fragmentation should be considered as the sufficient reproductive characteristics of semen to evaluate the quality of frozen/thawed sperm and prediction of PR

Microbial characteristics of soils on a latitudinal transect in Siberia

Soil microbial properties were studied from localities on a transect along the Yenisei River, Central Siberia. The 1000 km-long transect, from 56degreesN to 68degreesN, passed through tundra, taiga and pine forest characteristic of Northern Russia. Soil microbial properties were characterized by dehydrogenase activity, microbial biomass, composition of microbial community (PLFAs), respiration rates, denitrification and N mineralization rates. Relationships between vegetation, latitude, soil quality (pH, texture), soil organic carbon (SOC) and the microbial properties were examined using multivariate analysis. In addition, the temperature responses of microbial growth (net growth rate) and activity (soil respiration rate) were tested by laboratory experiments. The major conclusions of the study are as follows:1. Multivariate analysis of the data revealed significant differences in microbial activity. SOC clay content was positively related to clay content. Soil texture and SOC exhibited the dominant effect on soil microbial parameters, while the vegetation and climatic effects (expressed as a function of latitude) were weaker but still significant. The effect of vegetation cover is linked to SOC quality, which can control soil microbial activity.2. When compared to fine-textured soils, coarse-textured soils have (i) proportionally more SOC bound in microbial biomass, which might result in higher susceptibility of SOC transformation to fluctuation of environmental factors, and (ii) low mineralization potential, but with a substantial part of the consumed C being transformed to microbial products.3. The soil microbial community from the northernmost study region located within the permafrost zone appears to be adapted to cold conditions. As a result, microbial net growth rate became negative when temperature rose above 5 degreesC and C mineralization then exceeded C accumulation.</p