Impacts of Landscape Evolution on Heterotrophic Carbon Loss in Intensively Managed Landscapes

Soil respiration that releases CO2 into the atmosphere roughly balances the net primary productivity and varies widely in space and time. However, predicting its spatial variability, particularly in intensively managed landscapes, is challenging due to a lack of understanding of the roles of soil organic carbon (SOC) redistribution resulting from accelerated soil erosion. Here we simulate the heterotrophic carbon loss (HCL)—defined as microbial decomposition of SOC—with soil transport, SOC surface redistribution, and biogeochemical transformation in an agricultural field. The results show that accelerated soil erosion extends the spatial variation of the HCL, and the mechanical-mixing due to tillage further accentuates the contrast. The peak values of HCL occur in areas where soil transport rates are relatively small. Moreover, HCL has a strong correlation with the SOC redistribution rate rather than the soil transport rate. This work characterizes the roles of soil and SOC transport in restructuring the spatial variability of HCL at high spatio-temporal resolution.

Variational analysis of landscape elevation and drainage networks

Landscapes evolve towards surfaces with complex networks of channels and ridges in response to climatic and tectonic forcing. Here, we analyse variational principles giving rise to minimalist models of landscape evolution as a system of partial differential equations that capture the essential dynamics of sediment and water balances. Our results show that in the absence of diffusive soil transport the steady-state surface extremizes the average domain elevation. Depending on the exponent m of the specific drainage area in the erosion term, the critical surfaces are either minima (0 < m < 1) or maxima ( m > 1), with m = 1 corresponding to a saddle point. We establish a connection between landscape evolution models and optimal channel networks and elucidate the role of diffusion in the governing variational principles.

The Effects of Wind Erosion Depending on Cropping System and Tillage Method in a Semi-Arid Region

Wind erosion is a major environmental problem in arid and semi-arid regions, where it has significant impacts on desertification and soil degradation. To understand the effects of cropping systems and tillage methods on the reduction of soil wind erosion, wind tunnel investigations were performed on soil samples from an irrigated field in an experiment conducted in semi-arid northwestern China in 2016–2018. Three cropping systems for annual spring wheat (Triticum aestivum L.)/maize (Zea mays L.) strip intercropping (W/M), a two-year wheat-winter rape-maize rotation (WRM), and a two-year wheat-maize rotation (WM)) were each evaluated with two tillage methods (conventional tillage without wheat straw retention (CT) and no-tillage with 25–30 cm tall wheat straw (NT)). The mean rate of soil erosion by wind with NT was 18.9% to 36.2% less than that with CT. With increasing wind velocity, the rate of soil erosion by wind increased for both CT and NT but was faster with CT than NT. Soil wind erosion occurred with a wind velocity ≥14 m s−1, and NT greatly decreased the rate of soil erosion when wind velocity exceeded 14 m s−1. W/M, WRM, and WM with NT increased non-erodible aggregates by 53.7%, 53.7%, and 54.9% in 2017, and 51.3%, 49.6% and 44.6% in 2018, respectively, than conventional tillage. At a height of 0–20 cm, the rate of soil transport with CT decreased with increasing height. The volume of soil transport at a height of 0–4 cm and soil transport percentage at a height of 0–4 and 0–20 cm (Q0–4/Q0–20) with NT were less than with CT. These findings show that NT with cropping system intensification can be an effective strategy for resisting wind erosion in irrigated semi-arid regions, thereby reducing the negative environmental impacts of crop production.

Criterion assessment of soil transport structure stability

This paper considers features in forming stress -strain state (SSS) and stability of soil transport structures (cut and embankment) on the basis of calculation with the certified finite element method (FEM) GenIDE32. Numerical calculations make it possible to see the whole process of modeling organization of a soil structure: places where “plasticity” zones appear and develop, gradual formation of a landslide body. The analysis of SSS uses graphs of changes of SSS trajectories in the space of invariants of stress tensor σij and relative deformations εij in important nods and finite elements located at the sliding lines. At each step of modeling stability of depression or embankment is evaluated. Many signs indicate the termination of the landslide body formation. Noted in figures and graphs evolution of a landslide prism allows one to understand where the system is from the condition at which the landslide body formed: kstmin=1,00±0,02≈[kst]=1,00.

Evaluation of options for strengthening weak bases of embankments of transport infrastructure facilities

The rise in highway design and construction requires ensuring the reliability of these infrastructure projects. This is especially important for construction on weak soils. The number of design solutions is equally on the rise for reinforcing the grounds of soil transport structures. Examples include the use of various types of piles, and structures made of sand, gravel and other draining soils placed in a shell of geosynthetic material. The article presents the results of the authors' work on the substantiation and implementation of various constructive solutions to strengthen the insufficiently strong bases on railway and highway construction facilities (railway lines Losevo-Kamennogorsk, Moscow-Kazan high-speed railroad, Moscow-Saint Petersburg high-speed highway, etc.).