The emission of carbon dioxide from soils of the Pasvik nature reserve in the Kola Subarctic

The emission of carbon dioxide (CO₂) from podzols (Albic Podzols (Arenic)) and the factors controlling its spatiotemporal variability in the forest ecosystems of the Pasvik Reserve in the Kola Subarctic are characterized. Relatively favorable climatic conditions beyond the polar circle in summer are responsible for intensive soil respiration. The type of forest affects the emission of CO₂ from the soil surface. The lowest rate of the CO₂ emission is typical of the soils under lichen pine forest (105–220 mg C/(m² h) or 180 g C/m² during the summertime). Higher rates are observed for the soils under green moss pine (170–385 mg C/(m² h) or 360 g C/m² during the summertime) and birch (190–410 mg C/(m² h) or 470 g C/m² during the summertime) forests. This may related to a higher contribution of root respiration (44, 88, and 67%, respectively). Soil respiration and the contribution of root respiration to it increase with an increase in the canopy density; mass of small roots; microbial biomass; depth of the stony layer; soil moistening; and the contents of available carbon, nitrogen, phosphorus, and potassium compounds. At the same time, they decrease with an increase in the portion of lichens in the ground cover. The seasonal dynamics are characterized by the CO₂ emission maximums in the summer and fall and minimum in the spring. The daily dynamics are smoothed under conditions of the polar day.     

Carbon dioxide emission from the soil surface in a bilberry-sphagnum pine forest of the Middle Taiga

The dynamics of the carbon dioxide emissions from the surface of a gleyic iron-illuvial sandy peat podzolic soil under a mature bilberry-sphagnum pine forest were studied during the growing seasons of 2008–2010. The maximum rates of the CO₂ emission were observed in late July-early August, and the minimum rates were in October. In the hot summer of 2010, an additional maximum was observed in June. A close positive correlation existed between the intensity of the CO₂ emission and the soil temperature (r = 0.71, α = 0.05), whereas no significant correlation was found between the CO₂ emission and the soil water content. The coefficient of multiple correlation between the rate of the CO₂ emission and the hydrothermic soil characteristics reached 0.57 (at α = 0.05). The total CO₂ emission from the soil surface during the growing season was estimated at 68–100 g of C m^?2.     

Effects of grazing on CO2 balance in a semiarid steppe: field observations and modeling

Purpose

Carbon (C) dynamics in grassland ecosystem contributes to regional and global fluxes in carbon dioxide (CO₂) concentrations. Grazing is one of the main structuring factors in grassland, but the impact of grazing on the C budget is still under debate. In this study, in situ net ecosystem CO₂ exchange (NEE) observations by the eddy covariance technique were integrated with a modified process-oriented biogeochemistry model (denitrification–decomposition) to investigate the impacts of grazing on the long-term C budget of semiarid grasslands.

Materials and methods

NEE measurements were conducted in two adjacent grassland sites, non-grazing (NG) and moderate grazing (MG), during 2006–2007. We then used daily weather data for 1978–2007 in conjunction with soil properties and grazing scenarios as model inputs to simulate grassland productivity and C dynamics. The observed and simulated CO₂ fluxes under moderate grazing intensity were compared with those without grazing.

Results and discussion

NEE data from 2-year observations showed that moderate grazing significantly decreased grassland ecosystem CO₂ release and shifted the ecosystem from a negative CO₂ balance (releasing 34.00 g C?m^?2) at the NG site to a positive CO₂ balance (absorbing ?43.02 g C?m^?2) at the MG site. Supporting our experimental findings, the 30-year simulation also showed that moderate grazing significantly enhances the CO₂ uptake potential of the targeted grassland, shifting the ecosystem from a negative CO₂ balance (57.08?±?16.45 g C?m^?2?year^?1) without grazing to a positive CO₂ balance (?28.58?±?14.60 g C?m^?2?year^?1) under moderate grazing. The positive effects of grazing on CO₂ balance could primarily be attributed to an increase in productivity combined with a significant decrease of soil heterotrophic respiration and total ecosystem respiration.

Conclusions

We conclude that moderate grazing prevails over no-management practices in maintaining CO₂ balance in semiarid grasslands, moderating and mitigating the negative effects of global climate change on the CO₂ balance in grassland ecosystems.     

Evaluation of organic carbon stocks and СО<Subscript>2</Subscript> fluxes in grasslands of Western Transbaikalia

The stocks of organic carbon and mean rates of the CO₂ emission during the growing season (May–September) and the entire year were estimated in a sequence of grass ecosystems along the transect encompassing chestnut and meadow-chestnut steppe soils, marsh and meadow alluvial soils, and a haloxerophytic community on a typical solonchak. The total stocks of organic carbon comprised 6.17–9.70 kg С/m² in steppe, 7.41–10.04 kg С/m² in floodplain, and 4.74 kg С/m² in haloxerophytic ecosystems. The portion of humus carbon in the upper 50-cm-thick soil layer comprised 79–92% of the total carbon stock. The mean daily CO₂ emission (С–CO₂/(m² day)) from alluvial soils was moderate (3.3–4.9) or low (1.5–2.5). The dependence of the CO₂ emission on the moistening of steppe soils, temperature of alluvial soils, and temperature and moistening of solonchak was revealed. In comparison with the CO₂ emission from the zonal chestnut soil, its mean values during the growing season and the entire year were 1.2 times higher for the meadowchestnut soil, 3.3 times higher for the marsh alluvial soil, 2.3 times higher for the meadow alluvial soil, and 1.7 times higher for the solonchak. The portion of the CO₂ emission beyond the growing season in the mean annual emission averaged 19.8–24.2% and depended on the type of grass ecosystem and on weather conditions of particular years. The sink of carbon in the grass ecosystems exceeded carbon emission, especially in the steppe ecosystems.     

Emission of CO2 from the surface of oligotrophic bogs with due account for their microrelief in the southern taiga of European Russia

The results of studying the carbon dioxide fluxes from the soil’s surface during three years taking into account the microrelief are summarized. More precise estimates were obtained for the annual CO₂ emission from the oligotrophic peat bogs differing in vegetation and waterlogging in the southern taiga of European Russia. The maximum differences in the rates of the CO₂ emission related to the microrelief elements are characteristic of the treeless ridge-pool complex, where the hollows (without vegetation) emitted CO₂ twice less than the flat areas and thrice less than the hummocks. In the forest bogs, the differences related to the microrelief were significantly lower. In the areas with the ridge-pool microrelief, the weighted average (for 3 years) CO₂ emission was 436 g C/m² per year; in the better drained natural dwarf shrub-cotton grass-sphagnum pine forest, 930; and in the drained pine forest, 1292 g C/m² per year. The share of the CO₂ amount emitted in the cold period (November–April) amounted to 10% of its annual flux from the peat soils of the ridge-pool complex and 17 and 24%, respectively, in the natural and drained pine forests.     

库布齐沙漠植被恢复对风沙土壤碳通量与碳储量的影响

为阐明库布齐沙漠植被恢复过程中土壤碳通量的时空动态特征及主控因子，明确土壤有机碳含量和储量的变化趋势，本研究以流动沙地、半固定沙地、藻结皮固定沙地和地衣苔藓混合结皮固定沙地为研究对象，运用静态暗箱–气相色谱法对风沙土壤碳通量及水热因子进行观测，并对土壤有机碳含量和密度进行测定和计算。结果表明，生长季内风沙土壤碳通量变异较大，季节动态与土壤温度基本一致，且随植被恢复碳通量呈递增趋势：混合结皮固定沙地(210.28 mg/(m~2·h))>藻结皮固定沙地(177.45 mg/(m~2·h))>半固定沙地(117.34 mg/(m~2·h))>流动沙地(65.61mg/(m~2·h))；土壤碳通量与各层土壤温度均显著正相关，除流动沙地土壤碳通量与深层土壤含水量显著负相关外，其余样地碳通量均与表层土壤含水量显著负相关；风沙土壤有机碳含量和密度随植被恢复而递增：混合结皮固定沙地(1.32 g/kg,0.94 kg/m~2)>藻结皮固定沙地(1.03 g/kg,0.74 kg/m~2)>半固定沙地(0.45 g/kg,0.36 kg/m~2)>流动沙地(0.27...     

太行山前平原农田生态系统土壤呼吸速率的研究

研究结果表明，华北太行山前平原农田土壤呼吸速率呈明显的季节节律变化，土壤温度是影响土壤呼吸速率的主要环境因子。农艺措施对土壤呼吸速率有明显影响，深耕十深松处理条件下土壤呼吸速率大于少耕+深松和深耕+不深松处理。秸秆还田量大的处理土壤呼吸速率高。该区年土壤呼吸总量深耕+深松为1788g/m²，少耕+深松为1667g/m²，深耕+不深松为1629g/m²。     

Effects of temperature,glucose and inorganic nitrogen inputs on carbon mineralization in a Tibetan alpine meadow soil

High levels of available nitrogen (N) and carbon (C) have the potential to increase soil N and C mineralization. We hypothesized that with an external labile C or N supply alpine meadow soil will have a significantly higher C mineralization potential, and that temperature sensitivity of C mineralization will increase. To test the hypotheses an incubation experiment was conducted with two doses of N or C supply at temperature of 5, 15 and 25 °C. Results showed external N supply had no significant effect on CO₂ emission. However, external C supply increased CO₂ emission. Temperature coefficient (Q₁₀) ranged from 1.13 to 1.29. Significantly higher values were measured with C than with N addition and control treatment. Temperature dependence of C mineralization was well-represented by exponential functions. Under the control, CO₂ efflux rate was 425 g CO₂–C m^?2 year^?1, comparable to the in situ measurement of 422 g CO₂–C m^?2 year^?1. We demonstrated if N is disregarded, microbial decomposition is primarily limited by lack of labile C. It is predicted that labile C supply would further increase CO₂ efflux from the alpine meadow soil.     

Seasonal Dynamics of Soil CO<Subscript>2</Subscript> Concentration and CO<Subscript>2</Subscript> Fluxes from the Soil of the Former Lake Texcoco,Mexico

Seasonal changes of the soil CO₂ concentration and the rate of CO₂ fluxes emission from the soil formed on the sediments of the former Lake Texcoco, which occupied a significant part of the Mexico Valley until the mid-17th century, were studied. The soils (Fluvic Endogleyic Phaeozems) were characterized by a low CO₂ fluxes rate, which is related to their high alkalinity. The mean values of soil respiration were 6.0–14.1 mg C/(m² h) depending on vegetation type, which corresponds to 60–157 g C/(m² yr). The contribution of plants to the CO₂ fluxes insignificantly varied by seasons and depended on the species composition of vegetation. The soil CO₂ concentration and soil respiration in eucalypt (Eucalyptus globulus Labill.) plantation were two times higher than those in the grass–subshrub area, the ground cover of which consisted of Distichlis spicata (L.) Greene and Suaeda nigra (Raf.) J.F. Macbr. species. This can be related to the significant volumes of gas production during the respiration of eucalypt roots and associated rhizosphere community. The contribution of the root systems of grass cover to the soil CO₂ fluxes in eucalypt plantation slightly varied within the year and was equal to 24% on the average. In the grass–subshrub area, its value varied from 41% in the cold season to 60% in the warm season. The spatial variability of soil CO₂ concentration and its flux rate to the atmosphere was due to the differences in plant species composition and hydrothermal conditions, and their temporal trend was closely related to the seasonal accumulation of plant biomass and soil temperature.     

淡水湿地不同围垦土壤非耕季节呼吸速率差异

选择何种湿地利用方式,使得土壤固碳能力及CO₂气体排放受到的影响最小,是合理利用湿地、减少温室气体排放的关键所在,湿地土壤呼吸不仅受环境条件的影响,还受土壤本身性状的影响。以皖江地区为研究区域,利用定位试验对天然湿地及不同围垦利用方式下土壤在非耕季节CO₂排放通量、大气温度及表层土壤温度进行测定,并对其土壤TOC含量进行分析。结果表明,CO₂排放通量:水稻田[700.70 mg/(m²·h)]> 旱地[433.80 mg/(m²·h)]> 天然湿地[302.66 mg/(m²·h)],天然湿地土壤TOC含量明显高于围垦旱地及水稻田(0-30 cm),说明天然湿地较围垦旱地和水稻田对大气中CO₂浓度贡献最小,能存储更多的碳。探讨了CO₂排放通量与温度的相关性,得出3种土壤类型CO₂排放通量与大气温度和表层土壤温度均呈正相关关系。     

Carbon and nitrogen mineralization after maize harvest between and within maize rows: a microcosm study using 13C natural abundance

The sequestration of carbon in soil is not completely understood, and quantitative information about the rates of soil organic carbon (SOC) turnover could improve understanding. We analyzed the effects of the uneven distribution of crop residues after harvest of silage maize on C and N losses (CO₂‐C, dissolved organic carbon (DOC) and nitrogen (DON), and NO₃^–) from a Haplic Phaeozem and on the occurrence of priming effects induced by the decomposition of accumulated maize residues. Soil columns were taken from a continuous maize (since 1961) field after harvest i) between maize stalk rows (M_bare), ii) within the maize rows including a standing maize stalk (M_stalk), and iii) from a continuous rye (since 1878) field after tillage (rye stalk and roots were mixed into the Ap horizon). The soil columns were incubated for 230 days at 8 °C with an irrigation rate of 2 mm 10^–2 M CaCl₂ per day. Natural ¹³C abundance was used to distinguish between maize‐derived C (in SOC and maize residues) and older C originating from former C₃ vegetation. The uneven distribution of maize residues resulted in a considerably increased heterotrophic activity within the maize rows as compared with soil between seed rows. Cumulative CO₂ production was 53.1 g CO₂‐C m^–2 for M_stalk and 23.3 g CO₂‐C m^–2 for M_bare. The contribution of maize‐derived C to the total CO₂ emission was 83 % (M_stalk) and 67 % (M_bare). Calculated as difference between CO₂‐C release from M_stalk and M_bare, 19 % of the maize residues (roots and stalk) in M_stalk were mineralized during the incubation period. There was no or only a marginal effect of the accumulation of maize residues in M_stalk on leaching of DOC, DON, and NO₃^–. Total DOC and DON leaching amounted to 2.5 g C m^–2 and 0.16 g N m^–2 for M_stalk and to 2.1 g C m^–2 and 0.12 g N m^–2 for M_bare. The contribution of maize‐derived C to DOC leaching was about 25 % for M_stalk and M_bare. Nitrate leaching amounted to 3.9 g NO₃^–‐N m^–2 for M_stalk and to 3.5 g NO₃^–‐N m^–2 for M_bare. There was no priming effect induced by the decomposition of fresh maize residues with respect to CO₂ or DOC production from indigenous soil organic carbon derived from C₃ vegetation.     

Soil respiration in a tropical grassland

Soil respiration throughout an annual cycle was measured at three different stands in a tropical grassland situated at Kurukshetra at 29°58' N lat. and 76°51' E long. Rates of CO₂ evolution were measured by alkali absorption using 13 cm dia × 23 cm aluminium cylinders inserted 10 cm into the ground. Both movable and permanently-fixed cylinders were used. The CO₂ evolution rates for the three stands were: Stand I (dominated by Sesbania bispinosa) 49–358 mg CO₂ m^?2 h^?1; Stand II (mixed grasses) 55–378 mg CO₂m^?2 h^?1; and Stand III (dominated by Desmostachya bipinnata) 55–448 mg CO₂ m^?2 h^?1. A positive significant relation existed between rate of CO₂ evolution and soil water content (r = 0.59?0.740), and between soil respiration and temperature (r = 0.58?0.69). A statistical model developed on the basis of the relationship between CO₂ evolution rates and certain abiotic environmental factors showed 69% comparability between the calculated and observed values of soil respiration. The contribution of root and root-associated microorganisms to total soil respiration was estimated at 42% using the relationship between root biomass and CO₂ output from movable cylinders.     

Seasonal and Daily Dynamics of the CO<Subscript>2</Subscript> Emission from Soils of <Emphasis Type="Italic">Pinus koraiensis</Emphasis> Forests in the South of the Sikhote-Alin Range

The presented study shows the results of measuring soil respiration in typical burozems (Dystric Cambisols) under mixed Korean pine–broadleaved forests in the southern part of the Primorskii (Far East) region of Russia growing under conditions of monsoon climate. The measurements were performed in 2014–2016 by the chamber method with the use of a portable infrared gas analyzer. Relative and total values of the CO₂ efflux from the soil surface on four model plots were determined. The intensity of summer emission varied from 2.25 to 10.97 μmol/(m² s), and the total CO₂ efflux from the soils of four plots varied from 18.84 to 25.56 mol/m². It is shown that a larger part of seasonal variability in the soil respiration is controlled by the soil temperature (R² = 0.5–0.7); the soil water content also has a significant influence on the CO₂ emission determining about 10% of its temporal variability. The daily dynamics of soil respiration under the old-age (200 yrs) forest have a significant relationship with the soil temperature (R² = 0.51). The pyrogenic transformation of Pinus koraiensis forests into low-value oak forests is accompanied by an increase in the СО₂ efflux from the soil.     

Application of wood ash accelerates soil respiration and tree growth on drained peatland

Forested peatlands contain large pools of terrestrial carbon. As well as drainage, forest management such as fertilizer application can affect these pools. We studied the effect of wood ash (application rates 0, 5 and 15 t ha^?1) on the heterotrophic soil respiration (CO₂ efflux), cellulose decomposition, soil nutrients, biomass production and amount of C accumulated in a tree stand on a pine‐dominated drained mire in central Finland. The ash was spread 13 years before the respiration measurements. The annual CO₂ efflux was statistically modelled using soil temperature as the driving variable. Wood ash application increased the amounts of mineral nutrients of peat substantially and increased soil pH in the uppermost 10 cm layer by 1.5–2 pH units. In the surface peat, the decomposition rate of cellulose in the ash plots was roughly double that in control plots. Annual CO₂ efflux was least on the unfertilized site, 238 g CO₂‐C m^?2 year^?1. The use of wood ash nearly doubled CO₂ efflux to 420–475 g CO₂‐Cm^?2 year^?1 on plots fertilized with 5–15 t ha^?1 of ash, respectively. Furthermore, ash treatments resulted also in increased stand growth, and during the measurement year, the growing stand on ash plots accumulated carbon 11–12 times faster than the control plot. The difference between peat C emission and amount of C sequestered by trees on the ash plots was 43–58 g C m^?2, while on the control plot it was 204 g C m^?2. Our conclusion is that adding wood ash as a fertilizer increases more C sequestration in the tree stand than C efflux from the peat.     

Mineralization of nitrogen compounds in a soil under an oxalis birch forest

The total mineralization of nitrogen in the AO-A1 (0–6 cm), A1 (6–11 cm), and A2 (11–21 cm) horizons of a soddy pale-podzolic soil under an oxalis birch forest in Yaroslavl oblast was measured from May to November in 2009 and 2010 and comprised 6.7 ± 0.9, 3.0 ± 0.4, and 5.5 ± 0.6 g of N/m² in 2009 and 5.6 ± 0.5, 2.5 ± 0.2, and 2.1 ± 0.5 g of N/m² in 2010, respectively. The total nitrification reached 0.4 ± 0.1, 1.1 ± 0.2, and 1.4 ±0.1 g of N/m² in 2009 and 1.0, 0.6, and 0.7 g of N/m² in 2010. Overall, the amount of mineralized nitrogen in the 21-cm-deep soil layer in 2009 and 2010 constituted 15.2 ± 1.1 and 10.2 ± 0.7 g of N/m², respectively. The contribution of nitrification to the nitrogen mineralization amounted to 20%. The seasonal variations in the soil temperature and moistening affected the concentrations of ammonium in the upper horizons and the accumulation of ammonium in the AO-A1 and A1 horizons. The combined effect of the temperature and moisture controlled the ammonification in the AO-A1 horizon (R = 0.83 at p = 0.16 in 2010), the nitrification in all the studied horizons (R = 0.86 at p= 0.13 in 2009), and the ammonia emission from the soil surface (R = 0.92 at p = 0.06 in 2010). A correlation between the seasonal dynamics of the ammonification and the CO₂ emission was found for the AO-A1 horizon (r = 0.64 at p = 0.16 in 2010) and was absent in the deeper layers of the soil profile. The nitrogen losses from the soil surface due to the ammonia emission in the investigated periods reached 95 ± 31 g of N/ha (2009) and 33 ± 30 g of N/ha (2010).     

SE—Structures and Environment: Diurnal Variation in Ammonia,Carbon Dioxide and Water Vapour Emission from an Uninsulated,Deep Litter Building for Growing/Finishing Pigs

In an uninsulated livestock building with natural ventilation, the air temperature and airflow show a large variation according to the daily variations in weather and season. The objective of this investigation was to determine the diurnal variation in the emission of NH₃, CO₂ and moisture from an uninsulated building with a deep litter system for growing/finishing pigs and to investigate the influence of air temperature and airflow rate on the NH₃ emission. The investigations were carried out in an uninsulated experimental building with 125 growing/finishing pigs in deep litter pens. The building was 12 m wide and 20 m long (240 m²), naturally ventilated but also equipped with exhaust fans. The NH₃ concentration, the CO₂ concentration, the outside and inside air temperature, the outside and inside relative humidity and the animal activity were measured continuously during 6 days at a constant airflow rate of 146 m³ m⁻² h⁻¹. During six nights the effect of airflow rate on the NH₃ emission was investigated by changing the airflow rate in steps from 26 to 165 m³ m⁻² h⁻¹. The measurements were carried out between day 16 and day 46 from the beginning of the growing period. The NH₃ emission from an uninsulated, deep litter building for growing/finishing pigs showed a clear diurnal variation. During the 6 days with constant airflow rate the emission varied from 6 to 247% of the mean, with the minimum around 6.00 a.m. and the maximum around 5.00 p.m. The daily mean of NH₃ emission increased from 0·23 to 0·65 gh⁻ per pig (day 16–day 43). The diurnal variation of NH₃ emission was correlated to the inside air temperature (correlation coefficient r_s=0·86–0·91) and the animal activity (r_s=0·69–0·83). The increase of NH₃ emission with the air temperature followed an exponential pattern. The relative NH₃ emission flux increased from 0·2 to 2·0 between the air temperatures −2 to 14°C inside the building. An increase in airflow rate through the building from 26 to 165 m³ m⁻²h⁻¹ increased the relative NH₃ emission flux from 0·4 to 1·4. The CO₂ emission during the 6 days at constant airflow rate had a daily mean between 81 and 120 gh⁻¹ per pig with a diurnal variation from 61 to 249% of the mean. The CO₂ emission was correlated to the inside air temperature (r_s=0·42–0·83) and animal activity (r_s=0·67–0·85). The daily mean of water vapour emission increased during the same days between 146 and 408 gh⁻¹ per pig and varied from 18 to 269% of the mean. The water vapour emission was correlated to the inside air temperature (r_s=0·53–0·97), animal activity (r_s=0·57–0·85) and the water absorption capacity of the inlet air (r_s=0·27–0·94). The diurnal variations in NH₃, CO₂ and water vapour emission were correlated to each other.     

Spatial Variability of Carbon Dioxide Emission by Soils in the Main Types of Forest Ecosystems at the Zvenigorod Biological Station of Moscow State University

Carbon dioxide (CO₂) emission from the soil surface in forest biogeocenoses of the Zvenigorod Biological Station of Moscow State University in summer varies on average from 120 to 350 mg C–CO₂/(m² h) and depends on the hydrothermal conditions (soil moisture and temperature) and the type of phytocenosis. The intensity of CO₂ emission in the biogeocenosis does not depend on its parcel structure and varies with respect to plant microgroups: it is maximum in oxalis pine–spruce and maple–lime forests and bracken spruce–birch forests and minimum in areas of forest fall without vegetation. The upper (from 0 to 20 cm thick) soil layer provides up to 50% of the total soil CO₂ emission. The role of microbial respiration in the total CO₂ emission from soils is determined by weather conditions and varies from 9–33% in a dry summer to 55–75% in a summer with favorable temperature and moisture.     

Microbiological transformation of carbon and nitrogen compounds in forest soils of Central Evenkia

It has been found that the total productivity of bacteria and micromycetes in the 0- to 50-cm layer of homogeneous cryozems (Cryosols) on slopes of northern and southern exposures varies from 1.2 to 1.4 t/ha, respectively, and the calculated content of microbial carbon varies in the range 0.7–0.9 t/ha. The respiratory activity of the upper soil layer is 2.5–2.6 μg C–CO₂/(g h); the potential methane formation capacity reaches 0.13 nmol CH₄/(m² day) for soils on slopes of northern exposure and 0.16 nmol CH₄/(m² day) for slopes of southern exposure. Accumulation of sorbed ammonium is recorded in the range 15–17 mg NH₄/100 g soil in summer. The increase of temperature in the upper horizons of soils on slopes of southern exposure by 5°C compared to the northern slopes results in only an insignificant increase in the emission of CO₂ and CH₄. The accumulation of sorbed ammonium and nitrate nitrogen in homogeneous cryozems during the vegetation period is comparable to that in gray forest soils of the southern taiga subzone of the Middle Siberia.     

Emission of CO2 by soils in the impact zone of the Severonikel smelter in the Kola subarctic region

The intensity of the in situ soil respiration in the background northern taiga spruce forests of the Kola subarctic region reaches 120–290 mg C-CO₂/m² per h. In the impact zone of the Severonikel smelter, it decreases to 90–140, 30, and 15–30 mg C-CO₂/m² per h at the stages of spruce defoliation, spruce-birch woodland, and technogenic barrens of the technogenic succession, respectively. For the first time, the impact of the industrial pollution on root respiration has been assessed, and the dependences of the CO₂ emission, the contribution of mineral soil horizons to this process, the microbial biomass, and root respiration on the concentrations of available nickel and copper compounds have been determined. The efficiency of two remediation technologies applied to technogenic barrens near the smelter has been evaluated on the basis of four parameters of the soil biological activity. The results indicate that remediation with the creation of a new filled soil layer is more efficient than chemical and phytoremediation methods.     

Mulching Affects Soil Properties and Greenhouse Gas Emissions Under Long‐Term No‐Till and Plough‐Till Systems in Alfisol of Central Ohio

Agricultural activities emit greenhouse gases (GHGs) and contribute to global warming. Intensive plough tillage (PT), use of agricultural chemicals and the burning of crop residues are major farm activities emitting GHGs. Intensive PT also degrades soil properties by reducing soil organic carbon (SOC) pool. In this scenario, adoption of no‐till (NT) systems offers a pragmatic option to improve soil properties and reduce GHG emission. We evaluated the impacts of tillage systems (NT and PT) and wheat residue mulch on soil properties and GHG emission. This experiment was started in 1989 on a Crosby silt loam soil at Waterman Farm, The Ohio State University, Columbus, Ohio, USA. Mulching reduced soil bulk density and improved total soil porosity. More total carbon (16.16 g kg⁻¹), SOC (8.36 mg L⁻¹) and soil microbial biomass carbon (152 µg g⁻¹) were recorded in soil under NT than PT. Mulch application also decreased soil temperature (0–5 cm) and penetration resistance (0–60 cm). Adoption of long‐term NT reduced the GHG emission. Average fluxes of GHGs under NT were 1.84 g CO₂‐C m⁻² day⁻¹ for carbon dioxide, 0.07 mg CH₄‐C m⁻² day⁻¹ for methane and 0.73 mg N₂O‐N m⁻² day⁻¹ for nitrous oxide compared with 2.05 g CO₂‐C m⁻² day⁻¹, 0.74 mg CH₄‐C m⁻² day⁻¹ and 1.41 mg N₂O‐N m⁻² day⁻¹, respectively, for PT. Emission of nitrous oxide was substantially increased by mulch application. In conclusion, long‐term NT reduced the GHG emission by improving the soil properties. Copyright © 2016 John Wiley & Sons, Ltd.