Does forest tree species composition impact modelled soil recovery from acidic deposition?

Acidic deposition depleted soil base cation pools throughout central Ontario, particularly during the second half of the twentieth century. While sulphur (S) and nitrogen (N) deposition have declined in recent decades, forest harvesting may continue to remove base cations from soils, highlighting the need for reliable soil chemistry forecasts. This study investigated whether differences in soil chemistry among forest stands dominated by different tree species affected predictions using a dynamic biogeochemical model (VSD). Soil base saturation was modelled from 1850–2100 in stands dominated by balsam fir (<i>Abies balsamea</i> (L.) Mill.), eastern hemlock (<i>Tsuga canadensis</i> (L.) Carr.), white pine (<i>Pinus strobus</i> L.), sugar maple (<i>Acer saccharum</i> Marsh.), or yellow birch (<i>Betula alleghaniensis</i> Britt.). Three scenarios that manipulated future atmospheric S and N deposition and forest harvesting (2020–2100) were applied. When future atmospheric S and N deposition remained at 2020 levels and harvesting continued, base saturation increased marginally (2.0–4.5%) in all plots. Further increases in base saturation were minor (~1%) by 2100 when deposition reductions were implemented. When future forest harvesting was excluded, soil base saturation increased 3.4–8.5% from 2020–2100. These results suggest that tree species composition has minimal influence on modelled soil chemistry forecasts in response to changes in acidic deposition, and such models can be broadly applied for regional predictions.

Effect of fertilization and liming on the content of secondary metabolites in Hydrocotyle umbellata L. var. bonariensis (Lam.) Mr. Spreng

The nature and the amount of secondary compounds produced by plant species depends on environmental factors, which can act directly on the synthesis of the secondary metabolites. Hydrocotyle umbellata L. var. bonariensis (Lam.) Mr. Spreng has been traditionally used for medicinal purposes, including for antinociceptive, anti-inflammatory and anxiolytic-like effects, and phytochemical studies revealed its bioactive compounds. This work aimed to evaluate the effects of chemical and organic fertilization, and the soil base saturation correction in the H. umbellata crop in dystrophic yellow latosol soil in the production of the secondary metabolites (total phenolic, total flavonoid and hibalactone). The plant was cultivated in the soil of a rural property in the municipality of Anápolis (Goiás state). The experimental design was completely randomized in a controlled environment. The experiment with fertilization had five treatments (control; cattle manure; poultry manure; chemical fertilization; chemical and organic fertilization) and the experiment with liming included the correction of soil base saturation to 20%, 40%, 60% and 80%. The results in most of the two experiments were not statistically significant in the content of the metabolites studied. In the fertilization experiment, the control and manure treatments were statistically better in the content of total phenols in aerial mass analysis. Regarding the saturation correction experiment, the treatment without liming afforded higher levels of hibalactone content (considering the whole plant) and total phenolic content (considering the air mass). The treatment with correction of saturation to 40% afforded higher levels of total phenolic (considering the whole plant).

Calculation of large-span glulam structures as a soil base-foundation-above-ground structure system

The object of research. Long-span glulam arches are widely used as coatings for public and sports buildings. The studies carried out concern double-hinged segmental arches with spans of 60 m and more. Description of the problem. The study of the peculiarities of the work of arches as a system "soil base - foundation - above-ground structure" is associated with the significant influence of uneven deformations of supports on the stress-strain state of the above-ground structure. A change in the stress-strain state in the structure itself, associated with uneven deformations of the foundations, can lead to a significant decrease up to the complete exhaustion of the bearing capacity Main scientific results. This article provides an analysis of the change in the stress-strain state of glulam arches when calculating the system "soil base-foundation-above-ground structure". It is noted that non-uniform deformations of supports have the greatest influence on the stress in the support zones of the structure. The range of critical non-uniform subsidence has been determined, which should be limited when calculating and designing the foundations of large-span arches. It has been confirmed that double-hinged glulam arches work well in conditions of uneven subsidence due to the peculiarities of the design scheme. The results of the studies carried out and the recommendations provided will significantly improve the reliability of large-span structures and require mandatory inclusion in the current practice of calculation and design. In addition, additional requirements for the distance between mine workings for large-span structures should be introduced when performing engineering and geological surveys. This distance should be reduced for a clearer account of the deformability of the foundations for columnar foundations, and the number of workings should be increased. The area of practical use of the research results. The cross-section of the glulam arches is selected taking into account additional deformations of the supports, making it possible to avoid unpredictable damage to the structure during operation. Innovative technological product. Glulam arches, the cross-section of which is determined taking into account additional deformations from uneven subsidence of the supports Scope of application. Glulam arches calculated in this way can be used as covering for public and sports buildings for various purposes.

Performance Based Analysis of Shear Wall with Flexible Soil Base

Shear wall is usually modeled with different types of elements with fixed base to tolerate lateral load. Membrane, plate and shell elements are chosen to model shear wall without reinforcement. In the present study an attempt is made on a 3D, 10 storey building with flexible soil base. The building is analyzed with and without shear wall. The shear wall is provided at all four corners throughout the height of the building. The building is resting on flexible soil base and analyzed for nonlinear analysis. The shear wall is modeled with different elements and different number of layer section (i.e., concrete and steel layers). Shear wall is modeled separately with membrane, plate and shell elements. In addition to this combination of elements is also tried to model shear wall. The combination to model shear wall chosen is plate and membrane element with variation in number of concrete and steel layers. This study is helpful to predict response of shear wall provided with various elements. It gives us idea as to model shear wall with elements separately or in combination. The behavior of shear wall modeled with variation in concrete and steel layers is also predicted.

Analysis of the stressed-strained state of the foundation-shell at interaction with the elastic-plastic medium

On the basis of modern numerical implementations of the finite element method the article presents the justification of the adequacy of the method of solving the problems of structures straining in their contact interaction with the elastic-plastic nonlinear soil medium. Compatible calculations of structures and nonlinear bases, which are described by modern mechanical and soil models within one problem is a significant technical problem. The solution of the assigned tasks is possible only within the framework of numerical methods, the most common of which is the finite element method (FEM). The construction of the computational finite element model raises many complex questions that require additional detailed study. In addition, the compliance with the state building norms and regulations is an important factor for further practical use. The use of numerical methods in the calculation of machines and structures, taking into account their interaction with the elastic-plastic medium is largely determined by the complexity or even impossibility of analytical calculation due to the complexity of structural schemes, heterogeneity of material features, uneven soil layers, implementation of step-by-step work execution technologies and so on. The combination of the latest achievements in the field of structural mechanics and soil mechanics is a promising direction for the development of effective approaches to building discrete models of space systems “structure-nonlinear base” for solving applied problems. The use of the developed method allows to significantly specify the structures stress state interacting with the soil base, and to significantly specify the impact on the calculated level of the base bearing capacity. Only the simultaneous consideration of the nonlinear resistance of the soil base together with the plasticity and the structure destruction in the numerical simulation of the foundation-shell load provided good agreement with the natural experiment data as to the type of the boundary state and the bearing capacity level.

Effects of Moderate Nitrate and Low Sulphate Depositions on the Status of Soil Base Cation Pools and Recent Mineral Soil Acidification at Forest Conversion Sites with European Beech (“Green Eyes”) Embedded in Norway Spruce and Scots Pine Stands

High N depositions of past decades brought changes to European forests including impacts on forest soil nutrition status. However, the ecosystem responses to declining atmospheric N inputs or moderate N depositions attracted only less attention so far. Our study investigated macronutrient (N, S, Ca2+, Mg2+, K+) pools and fluxes at forest conversion sites over 80 years old in Central Germany with European beech (so-called “Green Eyes” (GE)). The GE are embedded in large spruce and pine stands (coniferous stands: CS) and all investigated forest stands were exposed to moderate N deposition rates (6.8 ± 0.9 kg ha−1 yr−1) and acidic soil conditions (pHH2O < 4.7). Since the understanding of forest soil chemical and macronutrient status is essential for the evaluation of forest conversion approaches, we linked patterns in water-bound nutrient fluxes (2001–2018) and in predicted macronutrient storage in the herbaceous and tree layer to patterns in litter fall (2016–2017) and in forest floor and mineral soil macronutrient stocks at GE and CS assessed in 2018. Our results exhibited 43% (Nt) and 21% (S) higher annual throughfall fluxes at CS than at GE. Seepage water at 100 cm mineral soil depth (2001–2018) of CS is characterized by up to fivefold higher NO3− (GE: 2 ± 0.7 µmolc L−1; CS: 9 ± 1.4 µmolc L−1) and sevenfold higher SO42− (GE: 492 ± 220 µmolc L−1; CS: 3672 ± 2613 µmolc L−1) concentrations. High base cation (∑ Ca2+, Mg2+, K+) concentrations in CS mineral soil seepage water (100 cm depth: 2224 ± 1297 µmolc L−1) show significant positive correlations with SO42−. Tree uptake of base cations at GE is associated especially with a Ca2+ depletion from deeper mineral soil. Foliar litter fall turns out to be the main pathway for litter base cation return to the topsoil at GE (>59%) and CS (>66%). The litter fall base cation return at GE (59 ± 6 kg ha−1 yr−1) is almost twice as large as the base cation deposition (30 ± 5 kg ha−1 yr−1) via throughfall and stemflow. At CS, base cation inputs to the topsoil via litter fall and depositions are at the same magnitude (24 ± 4 kg ha−1 yr−1). Macronutrient turnover is higher at GE and decomposition processes are hampered at CS maybe through higher N inputs. Due to its little biomass and only small coverage, the herbaceous layer at GE and CS do not exert a strong influence on macronutrient storage. Changes in soil base cation pools are tree species-, depth- and might be time-dependent, with recently growing forest floor stocks. An ongoing mineral soil acidification seems to be related to decreasing mineral soil base cation stocks (through NO3− and especially SO42− leaching as well as through tree uptake).