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The frozen earth: Fundamentals of geocryology

Sensitivity of labile carbon fractions to tillage and organic matter management and their potential as comprehensive soil quality indicators across pedoclimatic conditions in Europe

Soils contain a tangle of minerals, water, nutrients, gases, plant roots, decaying organic matter, and microorganisms which work together to cycle nutrients and support terrestrial plant growth. Most soil microorganisms live in periodically interconnected communities closely associated with soil aggregates, i.e., small (

https://aem.asm.org/content/aem/early/2019/05/08/AEM.00324-19.full.pdf

Soil Aggregate Microbial Communities: Towards Understanding Microbiome Interactions at Biologically Relevant Scales

Adoption of improved silvopastoral practices in degraded pasture areas is thought to provide valuable local and global environmental benefits, including biodiversity conservation, However, these practices are insufficiently attractive to individual land users for them to adopt them spontaneously, particularly due to their high initial costs. This paper describes the contract mechanism developed for the Regional Integrated Silvopastoral Ecosystem Management Project, which is being implemented with financing from the Global Environment Facility (GEF). The project is testing the use of the payment-for-service mechanism to encourage the adoption of silvopastoral practices in three countries of Central and South America: Colombia, Costa Rica, and Nicaragua. The project has created a mechanism that pays land users for the global environmental services they are generating, so that the additional income stream makes the proposed practices privately profitable. Designing the mechanism required addressing issues such as (1) measuring the actual amount of environmental services being provided, so that appropriate payments can be made; (2) providing payments in a way that resulted in the desired change in land use; and (3) avoiding the creation of perverse incentives (for example, for land users to cut down existing trees so as to qualify for additional payments for tree planting). Two variants of the proposed payment mechanism are being tested, with participating land users assigned randomly to one or the other. The project also includes extensive monitoring of the effectiveness of each mechanism in stimulating adoption of the proposed measures and of the resulting impact on environmental services and on household welfare. These features, together with the three-country approach, will provide in the coming years a very rich dataset for testing the use of contract mechanisms for biodiversity conservation.

Paying for Biodiversity Conservation Services in Agricultural Landscapes

Microbial communities inhabiting soil aggregates dynamically adjust their activity and composition in response to variations in hydration and other external conditions. These rapid dynamics shape signatures of biogeochemical activity and gas fluxes emitted from soil profiles. Recent mechanistic models of microbial processes in unsaturated aggregate-like pore networks revealed a highly dynamic interplay between oxic and anoxic microsites jointly shaped by hydration conditions and by aerobic and anaerobic microbial community abundance and self-organization. The spatial extent of anoxic niches (hotspots) flicker in time (hot moments) and support substantial anaerobic microbial activity even in aerated soil profiles. We employed an individual-based model for microbial community life in soil aggregate assemblies represented by 3D angular pore networks. Model aggregates of different sizes were subjected to variable water, carbon and oxygen contents that varied with soil depth as boundary conditions. The study integrates microbial activity within aggregates of different sizes and soil depth to obtain estimates of biogeochemical fluxes from the soil profile. The results quantify impacts of dynamic shifts in microbial community composition on CO2 and N2 O production rates in soil profiles in good agreement with experimental data. Aggregate size distribution and the shape of resource profiles in a soil determine how hydration dynamics shape denitrification and carbon utilization rates. Results from the mechanistic model for microbial activity in aggregates of different sizes were used to derive parameters for analytical representation of soil biogeochemical processes across large scales of practical interest for hydrological and climate models.

Microbial community dynamics in soil aggregates shape biogeochemical gas fluxes from soil profiles – upscaling an aggregate biophysical model

This paper deals with the development of a generalized model for version control systems application as a support in a range of project-based learning methods. The model is given as UML sequence diagram and described in detail. The proposed model encompasses a wide range of different project-based learning approaches by assigning a supervisory role either to instructor or students in different project stages. Different strategies for supervisor role assignment are given. Project duration, project milestones, as well as a number of team members are discussed in respect to project-based learning method that the proposed model supports. Possible implementations of different project-based learning approaches on the proposed model are demonstrated by setting the model parameters. Version control server security issues are discussed in the manner of implementation aspects of the proposed model. One of possible model implementations is evaluated in respect of cooperation on the test group of 21 students. Implementation details are presented and compared with other approaches. Mentoring and monitoring students efforts during the development by implementing proposed model with specific model settings introduces controlled cooperation with high clarity in evaluation of individual students work. Using open source version control software on Linux platform, with web interface package, we implemented a low-cost support for project-based learning.

Version control in project-based learning

Soil structure is an important physical property of soil and has a great impact on the environment and agriculture. Dry aggregate size distribution and related soil structure indices are essential parameters in understanding the structural state of the soil. This study was conducted to determine the effects of different soil types and land uses on structure parameters and to relate them to selected soil properties. The investigation was performed on five soil types (Arenosols, Fluvisols, Chernozems, Gleysols and Solonetz), each from three different locations and under three different land uses (cropland, meadow and forest), so that a total of 135 undisturbed soil samples were collected. Dry sieving analysis was performed to obtain eight aggregate size classes (ASCs) (>10, 10-5, 5-3, 3-2, 2-1, 1-0.5, 0.5-0.25 and 10, 5-3 and 3-2 mm ASCs. Chernozems and Gleysols have more favorable structure than Arenosols, Fluvisols and Solonetz. Long term cultivation leads to the deterioration of soil structure and the formation of clods. Forest soils have a significantly better structure than soils under meadows and croplands. The application of principal component analysis and regression models identifies water retention at -33 kPa, bulk density and pH value as for the most important factors in predicting dMWD and dGMD.

/pdf/soil-dry-aggregate-size-distribution-effects-of-soil-type-2gfj13zy71.pdf

Soil dry aggregate size distribution: effects of soil type and land use.

Soil organic carbon (SOC) has a high impact on the sustainability of ecosystems, global environmental processes, soil quality and agriculture. Long-term tillage usually leads to SOC depletion. The purpose of this study was to determine the impact of different land uses on water extractable organic carbon (WEOC) fractions and to evaluate the interaction between the WEOC fractions and other soil properties. Using an extraction procedure at 20°C and 80°C, two fractions were obtained: a cold water extractable organic carbon (CWEOC) and a hot water extractable organic carbon (HWEOC). The results suggest that there is a significant impact from different land uses on WEOC. A lower relative contribution of WEOC in SOC and a lower concentration of labile WEOC fractions are contained in arable soil compared to forestlands. Chernozem soil was characterized by a lower relative contribution of WEOC to the SOC and thus higher SOC stability in contrast to Solonetz and Vertisol soils. Both CWEOC and HWEOC are hig...

The sensitivity of water extractable soil organic carbon fractions to land use in three soil types

The less productive soils present one of the major problems in wheat production. Because of unfavorable conditions, halomorphic soils could be intensively utilized using ameliorative measures and by selecting suitable stress tolerant wheat genotypes. This study examined the responses of ten winter wheat cultivars on stressful conditions of halomorphic soil, solonetz type in Banat, Serbia. The wheat genotypes were grown in field trails of control and treatments with two soil amelioration levels using phosphor gypsum, in amounts of 25 and 50 tha-1. Across two vegetation seasons, phenotypic variability and genotype by environment interaction (GEI) for yield traits of wheat were studied. The additive main effects and multiplicative interaction (AMMI) models were used to study the GEI. AMMI analyses revealed significant genotype and environmental effects, as well as GEI effect. Analysis of GEI using the IPCA (Interaction Principal Components) analysis showed a statistical significance of the first two main components, IPCA1 and IPCA2 for yield, which jointly explained 70% of GEI variation. First source of variation IPCA1 explained 41.15% of the GEI for the grain weight per plant and 78.54% for the harvest index. The results revealed that wheat genotypes responded differently to stressful conditions and ameliorative measures.

/pdf/multivariate-interaction-analysis-of-winter-wheat-grown-in-429fw7rio1.pdf

Multivariate Interaction Analysis of Winter Wheat Grown in Environment of Limited Soil Conditions.

This paper shows the impact of long-term reclamation practices on the content and qualitative composition of exchangeable base cations of the solonetz soil. Based on the results of field visits and laboratory analyses, chemical and agrotechnical reclamation practices (phosphogypsum application 25 t ha -1 or 50 t ha -1 , drainage pipes distance 20 m, trenching 50 cm, fertilization, soil tillage and cropping) have been applied to the solonetz soil. Analyses of cation exchange capacity (CEC) have shown that calcium (Ca +2 ) and sodium (Na + ) cations prevailed over magnesium (Mg +2 ) and potassium (K + ) cations in the soil exchange complex in all variants and all depths. Comparisons among variants and soil layers have shown that the contents of individual exchangeable base cations varied significantly (P � 0.05). The highest changes in exchangeable calcium content were achieved to the depth of 30 cm, in both treated variants, and these changes were still higher in the variant with 50 t ha -1 of phosphogypsum. The content of exchangeable Na + decreased by 43 % to 71% in variant I and by 23% to 64% in variant II in comparison with the control variant. The application of the reclamation practices caused changes in the composition and proportions of cations in the layers of the solonetz soil to the depth of 50 cm. When compared with CEC in the control variant, the exchangeable sodium percentage (ESP) in the treated variants decreased by 6% to 15% after fifteen years.

/pdf/impact-of-reclamation-practices-on-the-content-and-gjzcy87rnf.pdf

Vladimir Ćirić

Papers

Version control in project-based learning

Soil dry aggregate size distribution: effects of soil type and land use.

The sensitivity of water extractable soil organic carbon fractions to land use in three soil types

Multivariate Interaction Analysis of Winter Wheat Grown in Environment of Limited Soil Conditions.

Impact of reclamation practices on the content and qualitative composition of exchangeable base cations of the solonetz soil