Regional Climatic Fluctuations Research Articles

Relative prevalence of top-down versus bottom-up control in planktonic ecosystem under eutrophication and climate change: A comparative study of typical bay and estuary

Eutrophication and climate change may affect the top-down versus bottom-up controls in aquatic ecosystems. However, the relative prevalence of the two controls in planktonic ecosystems along the eutrophication and climate gradients has rarely been addressed. Here, using the field surveys of 17 years in a typical bay and estuary, we test two opposite patterns of trophic control dominance and their response to regional temporal eutrophication and climate fluctuations. It was found that trophic control of planktonic ecosystems fluctuated between the dominance of top-down and bottom-up controls on time scales in both the bay and estuary studied. The relative prevalence of these two controls in both ecosystems was significantly driven directly by regional dissolved inorganic nitrogen but, for the estuary, also by the nonlinear effects of regional sea surface temperature. In terms of indirect pathways, community relationships (synchrony and grazing pressure) in the bay are driven by both regional dissolved inorganic nitrogen - soluble reactive phosphorus ratio and sea surface temperature, but this drive did not continue to be transmitted to the trophic control. Conversely, trophic control in estuary was directly related to grazing pressure and indirectly related to synchrony. These findings support the view that eutrophication and climate drive the relative prevalence of top-down versus bottom-up controls at ecosystem and temporal scales in planktonic ecosystems, which has important implications for predicting the potential impacts of anthropogenic and environmental perturbations on the structure and function of marine ecosystems.

Determination of the main agricultural crops for the Metropolitan Puebla-Tlaxcala area using the Papadakis Methodology

agricultural crops in the Puebla-Tlaxcala Metropolitan Area (ZMPT). Design/methodology/approach: From April to June 2022, the classification process for identifying the main crops in the ZMPT was conducted. This process utilized monthly climatic data from the Mexican Institute of Water Technology (IMTA), analyzed through the Papadakis methodology (1970). Subsequently, the results were mapped using the Weighted Overlay (WO) tool in ArcGIS v.10.2. Results: The Papadakis methodology identified 10 seasonal crop types, particularly for summer and winter. The WO tool categorized potential areas into five classes: optimal, highly suitable, acceptable, and unacceptable for the establishment of several crops. Limitations on study/implications: This study has limitations due to incomplete and scarce databases and the complexity and cost associated with the software used. However, the implications for agriculture include the potential to enhance and diversify agricultural production by identifying optimal areas for establishment, especially in urban-peri-urban agricultural areas (UPAs). Findings/conclusions: This study successfully identified the main crops cultivated in the ZMPT and highlighted potential areas for their establishment. The generated cartographic information enables the strategic distribution of productive agricultural systems, particularly in UPAs, to adapt to regional climate fluctuations in the short, medium, and long term. Besides, an adequate distribution in the implementation of productive agricultural systems, particularly in UPAs, depending on fluctuations in the climatic conditions of the region.

Geochemical record of Lake Sabakty: Electrical conductivity and reconstruction of the Lateglacial and Holocene environments in the Southern Urals (Russia) steppe

Research subject. The Lake Sabakty sediments core, as a source of data on the Holocene and Lateglacial environments in the Southern Urals.Aim. To obtain a multiple regression model for quantitative reconstructions of the electrical conductivity of water based on the geochemistry of lake sediments and to reconstruct the Late Glacial and Holocene environments based on the study of the Lake Sabakty geochemical record.Materials and methods. After determination of correlations between the content of chemical elements in lake sediments and hydrochemical parameters of 107 Ural lakes, multiple regression models were obtained. Reconstructions were performed based on the results obtained by accelerator mass spectrometry (AMS 14C), 210Pb activity determination, and an analysis of chemical elements and organic matter contents in the sediment core.Results. Three multiple regression models using the concentrations of Na, Ca, Li, and Sr were obtained for electrical conductivity of water reconstruction. In the cold and dry Lateglacial (>12.0 ka cal BP), Lake Sabakty was a slightly brackish reservoir. During the transition from the Lateglacial to the Holocene (12–11.6 ka cal BP), the Lake Sabakty became more productive. In the Early (11.6–8.2 ka cal BP) and Middle (8.2–4.2 ka cal BP) Holocene, the electrical conductivity of water varied under the action of fluctuations in effective moisture. In the Late Holocene (4.2 ka cal BP – present), the Lake Sabakty became less saline due to an increase in effective moisture.Conclusions. The proposed multiple regression models enable rapid quantitative reconstructions of the electrical conductivity of water, which are particularly relevant for Lateglacial–Early Holocene sediments with a low number of microfossils. The Lake Sabakty geochemical record reflects global and regional climatic fluctuations, being more informative compared to the geochemical records of forest lakes in the Southern Urals. The decrease in the electrical conductivity of water of Lake Sabakty of approximately 7.9 and 4.2 ka cal BP coincides with similar data for several other lakes in the Urals.

Late Holocene vegetation and climate change in the northern Tibetan Plateau region based on a palynological analysis from Lake Ayakum

In this paper, we undertake a high-resolution palynological analysis of a sediment core covering the last 1500 years obtained from Lake Ayakum in the northern Tibetan Plateau, to improve the understanding of regional climate fluctuations and their driving mechanisms. The pollen spectra are dominated by herbaceous species such as Artemisia, Chenopodiaceae, Cyperaceae and Poaceae, which grew in various alpine desert settings. Four pollen assemblage zones are identified using stratigraphically constrained cluster analysis, representing climate history at different stages. The Artemisia/Chenopodiaceae (A/C) ratio and axis score of the first principal component are used to infer regional moisture conditions and reveal a temporal pattern that is consistent with various records from central Asia. The source of Cyperaceae pollen is mainly from marsh wetlands distributed around the lake, which responded sensitively to the lake level fluctuations. In contrast, arboreal pollen is mainly a long-distance transported component, reflecting changes in regional vegetation. Our findings show that the northern Tibetan Plateau experienced relatively wet conditions during the Dark Age Cold Period and the Little Ice Age, while relatively dry conditions occurred during the Medieval Warm Period and the last two centuries. Fluctuations in moisture levels are broadly consistent with moisture records elsewhere in western China, and show a good correlation with phase changes of the North Atlantic Oscillation. The climate changes in the northern Tibetan Plateau are supposed to be primarily triggered by the NAO phases through south-north migrations of the mid-latitude westerlies during the late Holocene.

Geomorphology of the Central Kurdistan Region of Iraq: landscapes of the Erbil Plain between the Great Zab and Little Zab Rivers

ABSTRACT We present the result of the geomorphological mapping of the central sector of the Kurdistan Region of Iraq. Therein, landscape evolution was mostly overseen by the regional geodynamic, related to the Arabia-Eurasia convergence, and in the Quaternary, regional climate fluctuations contributed to shaping landforms. The combination of such processes affected the distribution, types, and evolution of landforms (related to structural, hillslope, fluvial, and karst processes), with a noteworthy influence on the development of the local drainage network, which belongs to Tigris River catchment. The Great Zab and Little Zab Rivers – the main left tributaries of Tigris River – progressively cut anticline ridges growing in the area. Our analyses suggest that the structural deformation of the Zagros also controlled the evolution of the low-order channels of the hydrographic network. Since the Holocene, landforms dynamic was altered by intense human exploitation of the landscape and increased fluctuations between arid and humid conditions.

Late Pleistocene-Holocene fluvial records of the Wadi Dishshah: hydro-climatic and archaeological implications (Southern piedmont of the Hajar Mountains, Oman)

In Oman, quaternary climatic fluctuations alternated between humid and arid periods. Humid periods are a key component in landscape evolution and the history of early human-environment interactions, as they allowed for less-restrictive arid conditions by triggering increasing rainfall and fluvio-lacustrine activity. Fluvial archives are of great interest for understanding hydrosystems’ local responses to quaternary regional climatic fluctuations. For the end of the Pleistocene and the Holocene, little data are available in Northern Oman to examine this topic and to compare it with archaeological site distribution and subsistence strategies, in particular with regard to water resources. Here, we will present fluvial records from a small wadi called Wadi Dishshah, located in the southern part of the Hajar Mountains’ piedmont, near the Salakh Arch area. The study of the Wadi Dishshah relies on topographic surveys (aerial survey with drone), geomorphological mapping, morphostratigraphic analyses of natural and excavated sections, malacological analyses and age-dating using OSL and radiocarbon methods. Three phases of aggradation have been identified: the first one between 26,500 cal. BP and 11,300 cal. BP, a second between 6,200 cal. BP and 5,500 cal. BP and a late one around 2,800 cal. BP. The fluvial records from the Wadi Dishshah and its hydro-climatic significance are compared to the distribution of archaeological sites from the Salakh Arch area to discuss the relations between settlement strategies and surface flows. This work is the first case study of late Pleistocene – Holocene alluvial formations in this region of Oman.

Climatic fingerprint of spring discharge depletion in the southern Italian Apennines from 1601 to 2020 CE

Annual mean spring discharge (ASD) is an important water supply source, essential for ecological systems and societies dependent on groundwater resources. Influenced by both regional and local climate fluctuations, the inter-annual variability of ASD represents a climate memory signal, significantly affected when the drought pattern manifests itself in changing climatic regimes. Gaining a better historical perspective on ASD changes requires extended time-series of discharge data and relevant climate drivers. Here, using a parsimonious model, we present a continuous (modelled) time-series of annual ASD for the karst spring of Caposele, in the Cervialto Massif of southern Italy, which is hitherto the longest (1601–2020 CE) such time-series for the entire Mediterranean region. The model was designed to capture the importance of large-scale seasonal (spring, autumn and winter) precipitation (hydro-meteorological factor), and flood and drought indices (climatological factor), and to be consistent with a sample (1920–2020 CE) of actual data. We show a limited overall sensitivity of ASD to climate variability, with a mean of 4.21 m3 s−1 and a drop from ∼1759 CE. With a mean value of ∼3.60 m3 s−1 after ∼1987 CE, ASD has revealed a substantial descending trend—possibly a fingerprint of recent warming—with a depletion of regional water reservoirs. These results highlight the need to strengthen the capacity of groundwater resources in the face of changing, and possibly enhanced, drought patterns in the Mediterranean region.

Research advances in shrub dendroecology

The ecological value of shrub-ring data has received more and more attention. The tree-ring data of shrub species have been increasingly used to reveal growth dynamics of regional shrub vegetation and its sensitivity to climate change. Up to now, nearly 70 species of shrubs have been used in the studies of shrub dendrochronology, which considerably broadened the traditional tree-ring research network, enriched the research scope and object of dendrochronology, and certainly with great significance in revealing the characteristics of regional climate fluctuation and annual dynamics of structure, function and service for shrubland ecosystems. In this study, we systematically collected dendrochronological studies based on shrub species during the 1996-2021, and reviewed research progress in four main subfields (physiology, climatology, ecology and hydrology) in dendrochronology for shrub species. The characteristics of shrub growth and xylem anatomy under different environmental stresses were expounded. The main limiting factors for shrub growth in different climatic conditions and the history of regional climate fluctuations based on shrub-ring data were revealed. The individual growth and population dynamics of shrub species driven by climate and the changes in ecosystems caused by non-climatic factors were assessed, and the reconstructions of regional hydrological histories were compiled using tree-ring data of shrub species. Under the context of global warming, dendrochronological studies of shrub species in China should pay more attention to the responses of shrub species radial growth to drought stress under different moisture conditions in the semi-arid and arid regions and the transforming feature of distribution pattern and climate response sensitivity for shrub species under the background of climate change.

The redistribution of anthropogenic excess heat is a key driver of warming in the North Atlantic

Understanding ocean excess heat uptake is crucial for assessing climate warming, yet uncertainties remain about its history and redistribution. Here, we reconstruct ocean heat content change along the 25°N Atlantic hydrographic section and assess its spatiotemporal origin and fate. We show that the delayed response of the ocean below 700 m to sea surface temperature change contribute to 62% of full depth warming at this latitude for 1850–2018, falling to 35% for 1975–2018 when anthropogenic warming in the upper ocean accelerated. The regional climate fluctuations shape ocean heat content variability at 25°N with contributions from the Labrador Sea producing most of the decadal variability and the Nordic Seas bound to become the main contributor to deep ocean warming in the coming decades. Chiefly, the net excess heat transport across 25°N has increased recently, warming the domain north of 25°N at a rate of 0.89 ± 0.19 W m−2 during 2012–2018, revealing that excess heat redistribution is a key driver of North Atlantic heat gain.

Instant sedimentation in a deep Alpine lake (Iseo, Italy) controlled by climate, human and geodynamic forcing

AbstractThe sedimentary processes in the deep basin of large peri‐Alpine lakes have not been studied much on long timescales due to high coring complexity of such lake systems. In 2018, a 15.5 m long sediment section was retrieved from the deep basin of Lake Iseo (Italy) at 251 m water depth. A seismic survey associated with a multi‐proxy approach using sedimentological and geochemical analyses, reveals that event deposits correspond to 61.4% of the total sedimentation during the last 2000 years. The great heterogeneity of textures, colours and grain‐size distribution between the different types of event layers can be explained by the high number of potential sources of sediment in this large lake system. By combining a proxy of sediment sources with proxies of transport processes, flood events were distinguished from destabilizations of the slopes and the main delta. The three thickest mass wasting deposits correspond to major regional earthquakes events of 1222 ce, 1117 ce and around 700 ce. From a thorough comparison with regional climatic fluctuations and human activities in the watershed, it appears that periods of high sediment remobilization can be linked to a preceding increase in erosion in the watershed mainly under human forcing. Hence, even in large catchments, human activities play a key role on erosion processes and on sediment availability, disrupting the recording of extreme events in lacustrine archive.

Geomorphological and sedimentological evidences of palaeo-outburst flood events from TanglangLa-Gya catchment of River Indus, Ladakh, India

ABSTRACT Gya river, one of the main tributary of Indus, hosts several scattered palaeoflood deposits. The chronology, genesis and spatiotemporal relationships of these scattered deposits can throw light to the regional and global climatic fluctuations and their implications for the evolution of the valley. The valley structure of the Gya river consists of a broad middle reach alternating with narrow valleys and gorges in the upper and lower reaches which can be blocked by the slightest of sediment discharge damming the entire valley. The geomorphological, sedimentological and chronological study in this valley reveals multiple short-lived lake phases at 21–19.9 ka, 13 ka and 4.5 ka in the broader reach of the river during the transition periods when climate rapidly fluctuates between cold-dry and warm-wet. The damming in the valley is the result of the glacial lake outbursts in the head waters of the Gya catchment blocking the narrow lower reaches of the main channel by massive sediment. These lakes that are formed by valley damming contains ~108 m3 of water which subsequently breach out causing significant geomorphic changes on reach scale along the Gya river channel.

Altitudinal variations of hydraulic traits in Faxon fir (Abies fargesii var. faxoniana): Mechanistic controls and environmental adaptability

Global climate change has been seen to result in marked impacts on forest ecosystems such as accelerated tree mortality worldwide due to incidental hydraulic failure caused by intensified and more frequent occurrence of extreme drought and heat-waves. However, it is well understood how the tree hydrological strategies would adjust to environmental variability brough about by climate changes. Here we investigated the hydraulic adjustment as a mechanism of acclimation to different climate conditions along an altitudinal gradient in Faxon fir ( Abies fargesii var. faxoniana ) ― a tree species that plays a key role in conservation of wildlife and maintenance of ecosystem services in subalpine forests. The hydraulic traits and selective morphological and physiological variables were measured seasonally along an altitudinal gradient from 2,800 to 3,600 ​m a.s.l. We found that the native percentage loss of conductivity (PLC) increased with altitude across the seasonal measurements . Both the native sapwood-specific hydraulic conductivity ( K s ) and native leaf-specific hydraulic conductivity ( K l ) significantly decreased with altitude for measurements in July and October, coinciding with the timing for peak growth and pre-dormancy, respectively. The morphological traits varied toward more conservative tree hydrological strategies with increases in altitude, exhibiting trade-offs with hydraulic traits. The total non-structural carbohydrates in both needle (NSC Needle ) and branch (NSC Branch ) as well as photosynthetic capacity of current-year leaves played variable roles in maintaining the integrity of the hydraulic functioning and shaping the hydraulic adjustment under prevailing environmental conditions. Our findings indicate that Faxon fir possesses some degree of hydraulic adaptability to water limitation imposed by climate fluctuations in subalpine region through morphological and physiological modifications.

Can Forest Trees Cope with Climate Change?—Effects of DNA Methylation on Gene Expression and Adaptation to Environmental Change

Epigenetic modifications, including chromatin modifications and DNA methylation, play key roles in regulating gene expression in both plants and animals. Transmission of epigenetic markers is important for some genes to maintain specific expression patterns and preserve the status quo of the cell. This article provides a review of existing research and the current state of knowledge about DNA methylation in trees in the context of global climate change, along with references to the potential of epigenome editing tools and the possibility of their use for forest tree research. Epigenetic modifications, including DNA methylation, are involved in evolutionary processes, developmental processes, and environmental interactions. Thus, the implications of epigenetics are important for adaptation and phenotypic plasticity because they provide the potential for tree conservation in forest ecosystems exposed to adverse conditions resulting from global warming and regional climate fluctuations.

Exploring the Regional Dynamics of U.S. Irrigated Agriculture from 2002 to 2017

The United States has a geographically mature and stable land use and land cover system including land used as irrigated cropland; however, changes in irrigation land use frequently occur related to various drivers. We applied a consistent methodology at a 250 m spatial resolution across the lower 48 states to map and estimate irrigation dynamics for four map eras (2002, 2007, 2012, and 2017) and over four 5-year mapping intervals. The resulting geospatial maps (called the Moderate Resolution Imaging Spectroradiometer (MODIS) Irrigated Agriculture Dataset or MIrAD-US) involved inputs from county-level irrigated statistics from the U.S. Department of Agriculture, National Agricultural Statistics Service, agricultural land cover from the U.S. Geological Survey National Land Cover Database, and an annual peak vegetation index derived from expedited MODIS satellite imagery. This study investigated regional and periodic patterns in the amount of change in irrigated agriculture and linked gains and losses to proximal causes and consequences. While there was a 7% overall increase in irrigated area from 2002 to 2017, we found surprising variability by region and by 5-year map interval. Irrigation land use dynamics affect the environment, water use, and crop yields. Regionally, we found that the watersheds with the largest irrigation gains (based on percent of area) included the Missouri, Upper Mississippi, and Lower Mississippi watersheds. Conversely, the California and the Texas–Gulf watersheds experienced fairly consistent irrigation losses during these mapping intervals. Various drivers for irrigation dynamics included regional climate fluctuations and drought events, demand for certain crops, government land or water policies, and economic incentives like crop pricing and land values. The MIrAD-US (Version 4) was assessed for accuracy using a variety of existing regionally based reference data. Accuracy ranged between 70% and 95%, depending on the region.

Mass Balance of Austre Grønfjordbreen, Svalbard, 2006–2020, Estimated by Glaciological, Geodetic and Modeling Aproaches

Glacier mass balance measurements, reconstructions and modeling are the precondition for assessing glacier sensitivity to regional climatic fluctuations. This paper presents new glaciological and geodetic mass balance data of Austre Grønfjordbreen located in the western part of Nordenskiöld Land in Central Spitsbergen. The average annual mass balance from 2014 to 2019 was −1.59 m w.e. The geodetic mass balance from 2008 to 2017 was −1.34 m w.e. The mass balance was also reconstructed by the temperature-index model from 2006 to 2020 and by spatially-distributed energy-balance models for 2011–2015 and 2019. We found a cumulative mass balance of −21.62 m w.e. over 2006–2020. The calculated mass-balance sensitivity to temperature was −1.04 m w.e. °C−1, which corresponds to the highest glacier mass balance sensitivity among Svalbard glaciers. Sensitivity to precipitation change was 0.10 m w.e. for a 10% increase in precipitation throughout the balance year. Comparing the results of the current study with other glacier mass balance assessments in Svalbard, we found that Austre Grønfjordbreen loses mass most rapidly due to its location, which is mostly influenced by the warm West Spitsbergen Current, small area and low elevation range.

Morphotectonics of the northern Bogd fault and implications for Middle Pleistocene to modern uplift rates in southern Mongolia

Assessing the activity of strike-slip faults is often facilitated by cumulative offsets of morphological features. The December 4th 1957 Mongolia earthquake, generally referred to as the “Gobi Altai” or “Bogd” earthquake, had MW 8.1 and created long and complex surface ruptures of c. 350 km length along the Bogd fault that cuts across the foothills of the Gurvan Bogd mountains. Several left-laterally and vertically displaced Quaternary alluvial fans and morphogenic markers show cumulative offsets, allowing for an assessment of the effect of repeated earthquakes and active tectonics on landscape evolution. We propose to expand the active tectonic record along this fault up to a Middle Pleistocene time scale that spans regional climatic fluctuations, i.e. repeated glacial-interglacial cycles, and hence varying erosional and depositional rates.Five main drainage areas crosscutting the North Ikh Bogd segment of the Bogd fault were analysed and compared in terms of hypsometry, drainage steepness and alluvial fan slope inclination. Along the mountain front, deposits from all drainages form multiple alluvial fan levels that reflect recurring deposition-incision cycles. Previously published ages, as well as the spatial distribution of these fan levels, suggest that their incision and abandonment is induced by regionally dominant climate fluctuations. However, the increase of fan slope angles over time and the increased intensity of sub-surface folding observed in ground-penetrating radar profiles, suggests that cumulative tectonic uplift also has a strong impact on alluvial fan morphology. Estimates of the increase of fan slope angles as a result of cumulative tectonic uplift imply that Middle Pleistocene to modern vertical slip rates along the North Ikh Bogd segment of the Bogd fault are in the order of 0.9–1 mm/yr. However, much slower vertical slip rates along individual fault segments, ranging between 0.06 ± 0.01 mm/yr and 0.28 ± 0.07 mm/yr, indicate that uplift of the Ikh Bogd plateau occurs as a result of distributed deformation across multiple parallel fault strands within bedrock as well as alluvial fans. Our results emphasise the importance of regional studies along active faults that take into account the complexity of surface ruptures as well as the occurrence of related structures that can accommodate deformation.

Influence of late Quaternary climate on the biogeography of Neotropical aquatic species as reflected by non-marine ostracodes

Abstract. We evaluated how ranges of four endemic and non-endemic aquatic ostracode species changed in response to long-term (glacial–interglacial cycles) and abrupt climate fluctuations during the last 155 kyr in the northern Neotropical region. We employed two complementary approaches, fossil records and species distribution models (SDMs). Fossil assemblages were obtained from sediment cores PI-1, PI-2, PI-6 and Petén-Itzá 22-VIII-99 from the Petén Itzá Scientific Drilling Project, Lake Petén Itzá, Guatemala. To obtain a spatially resolved pattern of (past) species distribution, a downscaling cascade is employed. SDMs were reconstructed for the last interglacial (∼120 ka), the last glacial maximum (∼22 ka) and the middle Holocene (∼6 ka). During glacial and interglacial cycles and marine isotope stages (MISs), modelled paleo-distributions and paleo-records show the nearly continuous presence of endemic and non-endemic species in the region, suggesting negligible effects of long-term climate variations on aquatic niche stability. During periods of abrupt ecological disruption such as Heinrich Stadial 1 (HS1), endemic species were resilient, remaining within their current areas of distribution. Non-endemic species, however, proved to be more sensitive. Modelled paleo-distributions suggest that the geographic range of non-endemic species changed, moving southward into Central America. Due to the uncertainties involved in the downscaling from the global numerical to the highly resolved regional geospatial statistical modelling, results can be seen as a benchmark for future studies using similar approaches. Given relatively moderate temperature decreases in Lake Petén Itzá waters (∼5 ∘C) and the persistence of some aquatic ecosystems even during periods of severe drying in HS1, our data suggest (1) the existence of micro-refugia and/or (2) continuous interaction between central metapopulations and surrounding populations, enabling aquatic taxa to survive climate fluctuations in the northern Neotropical region.

Isotope features (δ13С, δ18О) of continental carbonates from Permian and Triassic boundary deposits Northeast of Russian plate: paleoclimatic and biotic causes, chemostratigraphy

The carbon and oxygen isotopic composition were determined in pedogenic, sedimentary and organogenic carbonates of continental deposits of the Upper Permian (Vyatkian stage) and lower Triassic (Induan stage) of the northeastern part of the Moscow Syneclise. It is assumed that variations in 18О (18.0 29.1 SMOW) and 13С (-8.8 0.7 PDB) values in them could be associated with both regional climate fluctuations and perturbation of the global carbon cycle at the Permian and Triassic boundary. The decrease in 18О values in the pedogenic carbonates of the roof sequence of the Vyatkian stage, apparently, was due to the cooling in the northeast of the Pangea supercontinent. The negative excursion of 13С values at this stratigraphic level is correlated with a similar excursion found in the Paleo-and Neotetis marine carbonates and corresponds to the Late Permian biotic event.

Зрошення — головний елемент сучасних агротехнологій в умовах Південного Степу України

The purpose. To justify scientifically directions of application of irrigation in modern crop production technologies in rainless conditions of South Steppe of Ukraine. Methods. Analysis, synthesis, generalization. Results. In conditions of climate fluctuation it is necessary to use in irrigation farming of Ukraine the intensive crop production technologies based on use of innovative methods with optimization of different methods of showering and regimes of irrigation, fertilizer systems, treatment and protection of plants. Structure of sown area and crop rotations on irrigated lands of Ukraine for intelligent use of irrigated lands and avoidance of negative impact of external factors of natural and anthropogenic character is offered. Methodological and methodical approaches are developed on the basis of integral criterion of irrigated lands for their intelligent use, avoidance of degradation processes, protection and reproduction of fertility. Resources saving techniques are improved of cultivation of different crops on biological properties with observance of project normative expenditures worked out by scientists of Institute of irrigation farming and other scientific institutes of NAAS. Scientific approaches on state-private partnership in guidance system of water resources are developed, and instruments of state support and regulation of entrepreneurial business in the field of irrigation farming are specified. Conclusions. The major on immediate prospects will be problems of decreasing all sorts of resource losses by irrigation and other elements of agrotechnologies in conditions of regional climate fluctuations. For this purpose it is necessary to develop new scientific approaches on application of innovative techniques of artificial irrigation on the basis of minimization of discharge of water, energy, work and means, setting of irrigation water, fertilizers, pesticides and biological preparations, taking into account location of root system of crops for determination of optimum doses of watering, use of solar energy for alternative power supplies and so forth.

Isotope Characteristics (δ13C, δ18O) of Continental Carbonates from Permian‒Triassic Rocks in the Northeastern Russian Plate: Paleoclimatic and Biotic Reasons and Chemostratigraphy

Carbon and oxygen isotope compositions were determined in the pedogenic, sedimentary, and organogenic carbonates from Upper Permian (Vyatkian Stage) and Lower Triassic (Induan Stage) continental rocks in the northeastern Moscow Syneclise. Variations of δ18O (18.0 to 29.1‰ SMOW) and δ13C (‒8.8 to 0.7‰ PDB) in them could be provoked both by regional climatic fluctuations and by perturbation of the global carbon cycle at the Permian‒Triassic boundary. Decrease of δ18O in pedogenic carbonates at the top of the Vyatkian Stage was likely caused by cooling on the northeastern side of Pangea. The negative excursion of δ13C values at this stratigraphic level correlates with the analogous excursion recorded in marine carbonates of the Paleo- and Neotethys and corresponds to the end-Permian biotic event.