Steppe Soils Research Articles

СОВРЕМЕННЫЕ ПРОБЛЕМЫ ДЕГРАДАЦИИ СУХОСТЕПНЫХ ПОЧВ ДОЛИНЫ МАНЫЧ

На базе Научно-экспедиционного стационара «Маныч» ЮНЦ РАН в 2009–2018 гг. проведены исследования по проблеме деградации почв сухой степи в долине Маныч на территории Орловского района Ростовской области (охранная и заповедная зоны Государственного природного заповедника «Ростовский»). Выявлено, что усиление аридизации климата и антропогенной нагрузки в сухой степи приводят к засолению, опустыниванию, пастбищной дигрессии. Для почвенного покрова характерна комплексность, обусловленная микрорельефом, высоким уровнем минерализации грунтовых вод (2-6 г/л) и их близким залеганием к поверхности, составом засоленных почвообразующих пород, а также антропогенном воздействием – распашкой целинных почв, высокой пастбищной нагрузкой, развитием эрозионных процессов в результате уничтожения естественного растительного покрова степи. Почвенные комплексы с высокой долей участия солонцеватых и солончаковатых почв (до 20–50%) составляют 25% исследуемой территории. Выпас в первую очередь влияет на показатели почвы, характеризующие плодородие. При возрастании пастбищной нагрузки почвы подвергаются интенсивному иссушению в связи с изреженностью растительного покрова, а также уплотнением верхних горизонтов (1,37 г/см3) и изменениями в структуре на агрегатном уровне. В почвы пастбищ с сильной нагрузкой низки содержание гумуса (не более 1,5 %) и его запасы (53-68 т/га). На исследованной территории площадь средне деградированных почв составляет 40 %, сильно и очень сильно деградированных – 32 %, слабо деградированных – 18 %, целинных (ненарушенных) – 10 %. Необходимы срочные меры по рационализации использования почв и повышению их плодородия, предотвращению развития деградационных процессов в них, а также по строгому контролю за соблюдением условий оптимальной пастбищной нагрузки.

Spatial Modeling of the Effects of Deflation Destruction of the Steppe Soils of Ukraine

Spatial Modeling of the Effects of Deflation Destruction of the Steppe Soils of Ukraine

СОДЕРЖАНИЕ ХИМИЧЕСКИХ ЭЛЕМЕНТОВ В ПОЧВАХ И ПОВЕРХНОСТНЫХ ВОДАХ ПЛОСКОГОРЬЯ УКОК (ЮГО-ВОСТОЧНЫЙ АЛТАЙ)

Актуальность исследования обусловлена слабой изученностью химического состава почв и поверхностных вод плоскогорья Укок, являющегося объектом всемирного наследия ЮНЕСКО. Цель: изучить уровни содержания химических элементов в почвах и поверхностных водах центральной, южной и юго-восточной части плоскогорья Укок и дать эколого-биогеохимическую оценку этой малоизученной территории. Объекты: основные типы почв (криоаридные и горные лугово-степные, горные луговые, горные тундровые) и поверхностные воды (реки Жумалы, Калгуты, Аргамжи, Ак-Алаха, Тархата и озеро Укок) плоскогорья Укок (Республика Алтай, Российская Федерация). Методы. Содержание металлов в почвах определено методом эмиссионного спектрального анализа в Институте геологии и минералогии СО РАН, общее содержание микроэлементов в природных водах – в химико-аналитическом центре ИВЭП СО РАН спектрометрическим методом с использованием электротермической атомизации. Результаты. Представлен химический состав различных типов почв и поверхностных вод высокогорного плоскогорья Укок. Уровни содержания химических элементов в почвах плоскогорья не превышают их кларков в почвенном покрове и соответствуют их концентрациям в горно-тундровых почвах Алтая. Исключением являются почвы и почвообразующие породы над Калгутинским W-Mo-V-Cu месторождением, где отмечается аномально высокое содержание вольфрама – до 30–60 мг/кг. С ореолами рассеяния и воздействием отвалов штольни и хвостохранилища обогатительной фабрики этого месторождения мы связываем повышенное содержание Cu в водах реки Калгуты – 16 мкг/дм3 и в почвах бассейна. Почвы плоскогорья отличаются невысоким валовым содержанием P и Са, но обогащены калием – его содержание превышает 2 % в большинстве образцов. Концентрация фосфора в почвах плоскогорья Укок возрастает с запада на восток, от выровненной (центральной) части к горным окаймлениям, что обусловлено фосфоритоносностью коренных пород Алтае-Саянской горной страны. Низкие значения элювиально-аккумулятивных коэффициентов большинства металлов в изученных почвах плоскогорья могут служить показателем отсутствия на данный момент здесь выраженного антропогенного загрязнения. Содержание большинства элементов в почвах увеличивается c глубиной. В горно-тундровых торфянистых почвах под ерником обнаружена биогенная аккумуляция Mn. Для степных почв отмечено некоторое накопление в поверхностных горизонтах Zn, Cr, V и Ni. Наиболее равномерным распределением отличается Pb и Zn. Исходная неоднородность моренных и озерно-ледниковых отложений определяет разнообразие внутрипрофильного распределения металлов в почвах, на них сформированных. Не выявлено четкой зависимости содержания большинства макро- и микроэлементов в поверхностных водах от уровня их концентраций в почвах. Тем не менее отмечено повышение интенсивность водной миграции железа в заболоченных ландшафтах Бертекской части бассейна реки Ак-Алаха, в водах которой обнаружено его наиболее высокое содержание.

Ecological and Functional Properties of Steppe Soils under Moderate Anthropogenic Impact

Steppe soils of a small industrialized city with moderate anthropogenic impact for example Krasny Kut, Saratov region were analysed to ascertain their ecological and functional state. In the course of this work, the concentration of heavy metals (Zn, Cu, Pb, Ni, Cr and Cd) was determined in the soil samples, including the hazard coefficient (Kо) and the total contamination coefficient (Zc). Magnetic susceptibility, magnetic coefficient (Kmag), thermomagnetic effect (dk) of the soil samples were analysed together with the activity of soil enzymes (dehydrogenases, catalases, peroxidases and invertases). Using ecological and geochemical analytical methods, a widespread excess of maximum permissible concentration (MPC) of mobile forms Ni, Pb, Cu and Zn was recorded in the soil samples of Krasny Kut, and a single excess of MPC was observed for Cr and Cd. According to Zc indicator values, 4 samples were classified as soils with moderately dangerous levels of contamination and 2 samples with dangerous levels of contamination. Using petromagnetic analysis, a few samples were observed to contain a moderate amount of introduced technogenic magnetic particles and one sample with a hazardous amount of introduced technogenic magnetic particles. Medium, high and very high levels of dehydrogenase, catalase, peroxidase and invertase activities were recorded in the soil samples, indicating the absence of ecotoxicants inhibiting the enzymes. The observed peculiarities in the ecological and functional state of soils, representative of the steppe zone of the Eastern part of the European territory of Russia will be required for monitoring, reducing and forecasting the anthropogenic burden on soil ecosystems.

Timing and Causes of the Origin of the Solonetz Process in the Desert–Steppe Soils of the Southeastern Russian Plain

The article discusses the time frame and the role of the anthropogenic factor in the solonetz process in soils of the desert–steppe zone of the southeastern Russian Plain. Based on the study of soils of different ages buried under the mounds of the Bronze and Middle Ages (6200–700 years ago) within the Salsko–Manych ridge, it was established that the soils of the region did not bear signs of the solonetz process at the macro level before the beginning of the 3rd millennium BC. The first solonetzes in the region began to form 4800–4700 years ago. Their appearance chronologically coincided with the beginning of increased climate aridization. During this period, desert steppes began to be actively inhabited by ancient cattle breeders specializing in breeding small cattle, which resulted in a sharp increase in the load on the soils and ecosystems of the steppe. The article considers the possible cause-effect relationships in the system “climate–economic model–solonetz process.”

AM fungal diversity and its impact across three types of mid-temperate steppe in Inner Mongolia, China.

Arbuscular mycorrhizal (AM) fungal diversity was measured in three different natural mid-temperate steppe types: the meadow steppe, typical steppe, and desert steppe. In these steppe soils, 24 AM fungal species from eight genera were identified, in which Glomus had the highest relative abundance. Funneliformis geosporus, Glomus microaggregatum, and Septoglomus constrictum had high relative abundance and were found widely across varying soil depth and steppe type. Meadow steppes had significantly higher AM fungal species richness compared to typical steppes and desert steppes, but there was no significant difference between typical steppes and desert steppes. AM fungal spore density, two Bradford-reactive soil protein (BRSP) fractions, and extraradical hyphal length densities (HLDs) were significantly different among the three steppe types. Alkaline phosphatase and acid phosphatase activity, urease activity, and soil bacterial and actinomycotic quantity were significantly related to the AM fungal spore density and species richness in these arid and semi-arid steppes. Therefore, steppe types could influence the distribution pattern of AM fungal diversity and the content of glomalin-related soil protein (GRSP).

Organic carbon stabilized by iron during slump deformation on the Qinghai-Tibetan Plateau

Soil organic carbon (SOC) associated with iron (Fe-OC) can be recognized as an important component of the stabilized carbon pool. In permafrost regions, slump deformation can expose soil organic carbon and alter moisture conditions, which change the Fe-OC distribution. We measured the top 30 cm of soils in five slump deformation landscapes under three vegetation types on the middle and eastern Qinghai-Tibetan Plateau. Three stages of slump deformation were defined according to their microtopography. In the slump deformation areas, the SOC and total nitrogen (TN) contents in the surface 30 cm of soils were all lower than the soils without slump deformation in wet meadow (22% and 26%), meadow (16% and 29%), and steppe (14% and 20%) areas. The contents of Fe-OC in wet meadow were 4.1% and 12.5% in the soils without and with slump deformation, respectively, whereas these contents in the meadow and steppe soils were 25.6% and 17.2%, respectively. Slump deformation greatly changed the physiochemical soil variables and affected the Fe-OC% based on different vegetation types. Fe-OC was correlated with factors such as soil moisture, pH and C/Fe ratio. The study shows that slump deformation greatly affected the SOC and TN distribution and SOC stabilization processes in areas with slump deformation features.

Opposite patterns of soil organic and inorganic carbon along a climate gradient in the alpine steppe of northern Tibetan Plateau

Both soil organic carbon (SOC) and inorganic carbon (SIC) are important components of soil carbon storage. However, few studies have attempted to estimate the magnitude and patterns of SIC in arid areas. We measured the concentrations of SOC and SIC in alpine steppe grasslands along a climate gradient in the Tibetan Plateau. At all sites, an opposing trend was found in the distribution of SOC compared with SIC. SOC increased with increasing precipitation, while SIC decreased. Within sites, SOC decreased with soil depth, while SIC increased. Among the variables considered, soil total nitrogen (TN) and soil water content explained the most variability in SOC (r2 = 0.95 for TN, r2 = 0.93 for soil water content), and soil pH had the highest correlation with SIC (r2 = 0.90). This finding indicates that SOC is closely related to biological processes, such as biomass input and litter accumulation, while SIC is determined by abiotic factors such as chemical and physical processes of soil formation. SOC and SIC densities showed that the SOC pool comprised 91% of total carbon (TC) storage in these alpine steppe soils. A decrease in SOC density occurred with depth, but this pattern was the opposite for SIC density in all soil profiles. These findings help to characterize the C cycle in the alpine steppe of the Tibetan Plateau.

Glycomyces buryatensis sp. nov., an actinobacterium isolated from steppe soil.

A novel actinobacterial strain, designated 18T, was isolated from a steppe soil sample collected in Buryatia, Russia and subjected to polyphasic taxonomic characterization. The strain was aerobic and Gram-stain-positive. The 16S rRNA gene sequence of strain 18T exhibited highest similarity to Glycomyces paridis CPCC 204357T (97.2 %). Results of phylogenetic analysis showed that strain 18T formed a distinct branch clearly affiliated to the genus Glycomyces. Whole-cell hydrolysates of the isolate contained meso-diaminopimelic acid as the cell-wall diamino acid. The whole-cell sugar profile was found to contain galactose, glucose, ribose and xylose. MK-10(H4) and MK-11(H4) were the predominant menaquinones. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, five unidentified phospholipids and four unidentified polar lipids. The major fatty acids identified were anteiso-C15 : 0 and iso-C15 : 0. The G+C content of the genomic DNA of strain 18T was 68.0 mol% (draft genome sequence). Based on its phylogenetic, phenotypic and chemotaxonomic features, strain 18T was considered to represent a novel species of the genus Glycomyces, for which the name Glycomyces buryatensis sp. nov. is proposed. The type strain of Glycomyces buryatensis is 18T (=JCM 33362T=CGMCC 4.7610T).

Grazing offsets the stimulating effects of nitrogen addition on soil CH4 emissions in a meadow steppe in Northeast China.

Grazing is the most common land use type for grasslands, and grazing may alter the impacts of the predicted enhancement of nitrogen deposition on soil CH4 flux. To understand the effects of nitrogen addition, grazing, and their interactions on soil CH4 flux, we conducted a field study on CH4 flux in a meadow steppe in Northeast China from 2017 to 2018. We measured the soil CH4 flux and soil physiochemical and vegetation parameters. The studied meadow steppe soil acted as a CH4 source due to the legacy effects of an extreme rainfall event. During the experimental period, the average CH4 fluxes were 7.8 ± 1.0, 5.8 ± 0.5, 9.3 ± 0.9 and 7.6 ± 0.6 μg m-2 h-1 for the CK (control), G (grazing), N (nitrogen addition) and NG (grazing and nitrogen addition) treatments, respectively. The cumulative CH4 fluxes were 24.9 ± 2.6, 11.5 ± 4.9, 28.8 ± 4.2 and 17.8 ± 3.5 μg m-2 yr-1 for the CK, G, N and NG treatments, respectively. The N addition increased the average CH4 flux by 19%, and the grazing treatment reduced it by 25%. The soil CH4 flux was positively correlated with the 0–10 cm soil water filled pore space (P < 0.01), soil NH4+-N (P < 0.01) and soil NO3--N (P < 0.01), but negatively correlated with the 0–10 cm soil temperature (P < 0.01), except for the sampling dates that were strongly influenced by the extreme rainfall event. The average CH4 flux was significantly (P < 0.05) affected by the grazing and N addition treatments with the N addition treatment significantly (P < 0.05) increased the CH4 flux, whereas grazing significantly (P < 0.05) decreased the CH4 flux. Grazing offset the stimulating effects of N addition on CH4 flux, and there was no difference (P = 0.79) in the CH4 flux between the CK and NG plots. In summary, moderate grazing has the potential to reduce the negative impacts of N addition on CH4 flux and can increase the capacity of the soil CH4 sink in the studied meadow steppe.

The Impact of Fires on the Properties of Steppe Soils in the Trans-Ural Region

The impact of fires that happened in different times (1 week, 1.5 and 2 months, 1 and 2 years ago) on the properties of southern (textural-carbonate) chernozems was studied in the Trans-Ural steppe (Bashkortostan Republic and Chelyabinsk oblast, Russia). The topsoil horizons (0–5, 5–10, and 10–20 cm) were sampled in summer 2018. After the fires, the carbon content in the layer 0–5 cm increased by 8.7–12.0% relative to the initial content, and the contents of major nutrients (nitrogen, phosphorus, and potassium) sharply increased and remained at this level for two years. The pH values in the humus horizon after the fire increased by 1.5 pH units. The contents of exchangeable calcium, potassium, and sodium correlated with pH (r = 0.57, 0.58, and 0.65, respectively, at p < 0.001). The content of exchangeable sodium increased from 0.17 ± 0.01 to 0.23 ± 0.01 cmol(+)/kg of soil. The TDS of water extracts from the soil of background plots averaged 0.11 ± 0.01% increasing to 0.17 ± 0.02% in the soils after fires; on some plots, the soils became slightly or moderately saline with the TDS of up to 0.56%; the composition of major anions remained stable and was characterized by a predominance of sulfates and bicarbonates. The activities of dehydrogenase, urease, and protease in a week after the fire decreased by 8–11%; the activity of invertase decreased by 18%. However, in 1.5 months after the fire, the activities of dehydrogenase, invertase, and protease were even higher than those in the background soil. The urease activity was restored to the background level in a year after the fire. The soil acidity approached the background level after two years. Fires are an important factor of pedogenesis in steppe ecosystems that have positive and negative consequences.

Features of the Composition of Humus Horizons of Arid Soils in the Barguzin Depression

Various types of arid soils that formed under the environmental conditions of the ultracontinental climate at the northern boundary of the steppe distribution in central Asia have been studied. The survey results for the surface horizons of the steppe soils and the soils of the contact forest–steppe zone according to the color characteristics and the humus properties are reported. The dominant cryo-humus accumulation in the soils of the steppe ecosystem and the light-humus soils of the contact zone are determined according to the Munsell scale and the CIE-L*a*b* color system. The ratio of labile and bioinert fractions of the humus compounds may serve as diagnostic parameters. Cluster analysis is performed based on 25 parameters of the soil humus horizons. The first cluster unites the steppe soils with the cryo-humus accumulation, while the second cluster involves soils with light-humus accumulation. Soils with the AK–BCA–Cca profile are classified at the current survey stage as cryo-humus soils. The obtained data can be used to correct the status of cryo-arid soils in the soil classification system.

Soil CO2 Emission, Microbial Biomass, and Basal Respiration of Chernozems under Different Land Uses

The relationships between the soil CO2 emission and microbial properties have been studied in Haplic Chernozem of steppe, forest (oak), bare fallow of the reserve area and in Urbic Technosols of Kursk city. The CO2 emission was monthly measured (May–October) from the soil surface (EMsurf) and two subsoil layers at the depths of 10 and 20 cm (EM10, EM20), and the soil temperature and water content were simultaneously recorded. Overall, 360 soil samples have been taken from the layers 0–10, 10–20, and 20–30 cm for determining the microbial properties (microbial biomass carbon, Cmic; basal respiration, BR). Soil chemical properties (the organic C content, total C, N, P, K, and Ca; and pH) have been measured in the samples taken in July. The EMsurf of steppe averaged 24 g СО2/(m2 day), which was 1.6, 1.5 and 6 times higher than that of forest, urban, and fallow soils, respectively. In the forest, EM10 and EM20 were two times higher than reference EMsurf; they were similar in the fallow and urban soils; and they were by 34% lower in the steppe soil. The soil CO2 emission of studied ecosystems depended weakly on soil temperature and water content during the growing season. The Cmic and BR (0–10 cm) of undisturbed ecosystems (steppe, forest) were higher by, on average, 3–5 and 2–4 times, respectively, than those of disturbed (fallow, urban) ecosystems. The positive correlations between EMsurf and Cmic, BR (0–10 cm) were found (r = 0.56 and 0.74, respectively). The seasonal average EMsurf for different land uses was controlled mainly (78%) by soil BR (linear regression). Therefore, the EMsurf from Chernozems of different land uses during the growing season might be predicted on the basis of BR measurements (0–10 cm).

Unexpectedly high diversity of arbuscular mycorrhizal fungi in fertile Chernozem croplands in Central Europe

Highly fertile soils are considered to harbor low diversity of arbuscular mycorrhizal fungi (AMF), since plants might not depend on the mycorrhizal symbiosis to efficiently assimilate soil nutrients. ‘Black steppe soils’ classified as Chernozems are counted among the soil types with highest natural fertility and productivity. However, information on AMF diversity from highly productive Chernozems used as croplands are extremely rare to non-existent. Our objective was to study the impact of soil tillage and fertilization intensity on AMF communities in a long-term field trial established on a silty-loamy Calcic Chernozem in the Magdeburger Börde (Central Europe). Samples were taken at harvest of maize that grew in a rotation with winter wheat, winter barley, winter oil seed rape and again winter wheat. AMF species were characterized by spore morphology. Astonishingly high spore densities (up to 41 spores g−1 soil) and species richness (19–33 species) of AMF were found in this highly productive Chernozem cropland, even under high-input conditions, which were, however, higher in reduced tillage than in regularly ploughed plots. AMF diversity decreased with increasing fertilizer input concerning N and P. These findings might re-stimulate the discussion about the significance of AM fungi in highly productive croplands, which was so far thought to be low. Several indicator AMF species were identified for reduced tillage (e.g. Ambispora fennica and Dominikia bernensis) or reduced fertilizer inputs (e.g. Dominikia aurea) or both (e.g. Diversispora celata and Scutellospora calospora), but only a few for tillage (e.g. Funneliformis fragilistratus and Pacispora dominikii). AMF indicators have to be, however, identified for each soil type and climatic condition separately, as they should be completely different from those species for instance in nutrient-poor or in acidic soils, in warmer or colder as well as in more humid or arid climates.

Grazing Effect on Soil Properties in Dry Subtropic Steppes of Azerbaijan

The article presents changes in the morphological and diagnostic parameters of gray-brown soils of dry steppes under the effect of grazing on a reserve and with regulated and free grazing. It has been revealed that, in comparison with the reserve regime, long-term intensive free grazing on gray-brown soils of dry steppes resulted in a 50–55% decrease in the projective vegetation cover, a poorer (loose) soil structure, compaction, and a 9.45% decrease in humus content and a 6.07% decrease in organic carbon content in the top horizon. The thickness of the humus horizon decreased by about 50%. There was a twofold decrease in the nitrogen content, while the drop in available phosphorus and potassium compounds was relatively smaller. The physical and mechanical soil properties also worsened: soil compactness in the 0–10-cm layer dropped by 0.13%, valuable clay particles were washed from the topsoil, the soil structure became more powdery, and the content of valuable water-stable aggregates and their water resistance decreased. The goal of the study is to develop more efficient pasture use for grazing in dry steppes.

Soils of Alpine, Subalpine Meadows and Meadow Steppes of Azerbaijan and the Peculiarities of Their Assimilation Potential in Relation to Organic Pollutants

Azerbaijan is a country with a huge range of different soil types, which is due to its geographical location. The country is located in two climatic thermal zones, subboreal and subtropical, characterized by a peculiar hydrothermal regime, diverse vegetation and soil fauna. For proper zoning of the soil cover of bioclimatic landscape zones and the development of effective organization of management systems, assessment of assimilation potential is of great importance, i.e. self-cleaning potential. The purpose of our research was to assess the actual assimilation capacity and self-cleaning ability of alpine and subalpine meadow soils and meadow steppes in case of their contamination with organic pollutants based on a comprehensive system analysis of biogenic and abiogenic factors. The collected material was comprehensively analyzed from the standpoint of the biogenicity and self-purification capacity of soils of various bioclimatic landscape zones from the standpoint of the danger of soil contamination with organic matter, based on the natural features of the soil and biogenic and abiogenic factors, and appropriately grouped according to the landscape feature. The analysis of the obtained data allows us to position the soils of the Alpine and subalpine meadows and meadow steppes on the growth of the assimilation potential in relation to organic pollutants in the following sequence:Mountain-meadow chernozem-like&gt; Mountain-forest meadow&gt; Mountain-meadow steppe&gt; Mountain-meadow sod

Vegetation biomass and soil moisture coregulate bacterial community succession under altered precipitation regimes in a desert steppe in northwestern China

Given that soil water availability is the major limitation on plant growth in desert steppes, uncovering the connections between belowground and aboveground communities under altered precipitation regimes will improve our knowledge of the potential impacts of global climate change on this fragile ecosystem and the services it provides. To investigate the relationships and the underlying drivers of soil bacterial community structure, we established a three-year field experiment in a desert steppe in northwestern China with manipulative precipitation treatments consisting of natural precipitation, 30% reduction, and 30% and 50% increases in precipitation. Results showed that bacterial community composition varied significantly with altered precipitation regimes, but community richness and evenness did not. The bacterial community structure showed much more sensitivity to the increase in precipitation than it did to decrease in precipitation. The effects of altered precipitation regimes on bacterial community composition depended upon the relationship between precipitation, vegetation, and soil properties. Soil microbial biomass C was the best predictor of bacterial community succession when precipitation was experimentally altered. Our results indicated that bacterial communities in desert steppe soils responded to changes in precipitation primarily through plant–soil–microbe interactions, as opposed to responding directly to changes in soil moisture.

SOILS OF THE EASTERN PRIOL’KHONYE ON THE COAST OF THE LAKE BAIKAL: CURRENT STATE AND USE

In summer periods of 2015–2017 within the framework of complex expeditions in the eastern Priol’khonye soil geochemical researches were performed. More than 120 soil samples were collected for subsequent physical and chemical analyses. Ecological, chemical and physical properties of meadow and steppe soils of Ol’khon district were studied and the results are presented in the article. The research was conducted on the east coast of the Lake Baikal in its central basin, which is most visited by tourists. Several soil types can be found along the coast line and on gently sloped surface nearby, they are: castanozems, umbrisols, cambisols, gray soils, histic fluvisols gleyic, humic fluvisols gleyic, chernozems, umbric fluvisols, cambic fluvisols and other. Owing to a specific environmental conditions some original soil types (for example “chestnut soils”, “castanozems”) can be found nowhere else in the Irkutsk region but only here. The explored soil profiles are mainly thick and stony to various extent (from high to medium),these soils are sandy or sandy loams, rich in humus, predominantly with neutral and weakly alkaline reaction (pH), low content of nitrogen in relation to carbon content (C : N), that creates favorable conditions for preservation of the vegetable remains in meadow landscapes. The conducted research results revealed that soils near touristic tracks and also on the territory of the ancient settlement are polluted by heavy metals, and their content exceeds sanitary and hygienic standards. The ecological condition of soils at the present stage can be characterized as average degree of disturbance resulting from recreational activity. Geochemical barriers are represented by organic and alkaline ones. However, due to the sandy and sandy-loamy soil texture waters of the lake coastal zone can be polluted by heavy metals as well. Soils of meadow-boggy landscapes of the coastal area are not polluted by heavy metals as far as it is a hard-to-reach region for tourists using automobile transport.

Differences in main processes to transform phosphorus influenced by ammonium nitrogen in flooded intensive agricultural and steppe soils

Exogenous ammonium nitrogen (AN) fertilization/deposition and the subsequently induced soil acidification, might exacerbate soil phosphorus (P) transformation and mobility, whereas poor understanding in abiotic and biotic processes still existed between intensively cultivated soil with high proportion of legacy inorganic P (Pi) in comparison to natural steppe soil with high proportion of organic P (Po). Column batch flooded experiment using vegetable (VEG) and steppe (STE) soils was conducted to investigate the P transformation and mobility influenced by 60-day intermittent elution with an (1500 mg N kg−1) solution or an acid sulfate (107 mmol H+ kg−1) solution. The results showed that AN elution significantly decreased the contents of all Pi fractions and strengthened Pi leaching, whereas acid elution increased the contents of Al-Pi, Fe-Pi, and reductant-soluble Pi and reduced P leaching in VEG soil. In contrast, AN elution increased the contents of soluble-Po and Al-(Pi + Po) and decreased Ca-P and Fe-Pi, no effects on P leaching, whereas acid elution increased the contents of soluble-(Pi + Po), Al-(Pi + Po), Fe-(Pi + Po) and reduced P leaching in STE soil. Variances analysis showed that pH and microbial biomass carbon were the most important factors to predict the P composition of the VEG and the STE soil, respectively. This indicated that AN elution released the soil mineral-bound phosphate with ammonia oxidation coupled with Fe(III) reduction, besides the same chemical influences on Fe/Al oxides as acid elution in VEG soil; while predominantly affected biochemical/biological processes of soil P by changing microbial biomass and enzyme activities in STE soil.

Quantification of the Parameters of Zones and Facies of Chestnut Soils in Russia on the Basis of the Climatic-Soil-Textural Index

This study is an attempt to quantify parameters taken into account in separation of the dry steppe soil zone. A detailed analysis of the maps of zoning, vegetation, land use, and soils has made it possible to suggest quantitative criteria of the dry steppe soil zone in Russia and to gain a better correlation between the calculated boundaries of this zone and the maps of vegetation, land use, and soils. Except for the East European Plain, boundaries of the dry steppe zone with chestnut soils do not coincide on different maps of zoning. Climatic parameters—the sum of active temperatures, the humidity factor, and the continentality coefficient—are the main factors specifying the spatial pattern of soil zones and facies on the maps of zoning. Soil characteristics—texture and water-physical properties—play a subdominant role. It is argued that data on the texture, water-physical properties, and solonetzic properties of soils should be taken into account in separation of the dry steppe zone as the factors controlling the depth of soil moistening and the reserves of productive moisture. Together with the accumulated sum of active temperatures, they specify the development of dry steppe vegetation and, hence, the boundaries of the dry steppe soil zone. A new indicator—the sum of monthly excesses of precipitation over evapotranspiration—should be calculated with due correction for the soil texture, solonetzic properties, and the content of carbonates. In combination with the accumulated sum of active temperatures, this indicator makes it possible to perform a detailed zoning of the area of chestnut soils on a quantitative basis and to separate cryoarid areas (cold semideserts) and semideserts with chestnut soils. Soil zones and facies determined with the use of this indicator are in good agreement with geobotanical maps and maps of land use.