Decomposing crop residues contribute to soil organic matter (SOM) accrual; however, the factors driving the fate of carbon (C) and nitrogen (N) in soil fractions are still largely unknown, especially the influence of soil mineralogy and autochthonous organic matter concentration. The objectives of this work were (1) to evaluate the retention of C and N from crop residue in the form of occluded and mineral-associated SOM in topsoil (0–20 cm) and subsoil (30–70 cm) previously incubated for 51 days with ¹³C-¹⁵N-labelled corn residues, and (2) to explore if specific minerals preferentially control the retention of residue-derived C and N in topsoil and subsoil. We used topsoil and subsoil having similar texture and mineralogy as proxies for soils being rich (i.e., topsoil) and poor (i.e., subsoil) in autochthonous organic matter. We performed a sequential density fractionation procedure and measured residue-derived C and N in occluded and mineral-associated SOM fractions, and used X-ray diffraction analysis of soil density fractions to investigate their mineralogy. In accordance with our hypothesis, the retention of C and N from crop residue through organo-mineral interactions was greater in subsoil than topsoil. The same minerals were involved in the retention of residue-derived organic matter in topsoil and subsoil, but the residue-derived organic matter was associated with a denser fraction in the subsoil (i.e., 2.5–2.6 g cm⁻³) than in the topsoil (i.e., 2.3–2.5 g cm⁻³). In soils and soil horizons with high clay content and reactive minerals, we find that a low SOM concentration leads to the rapid stabilization of C and N from newly added crop residues.

Mesh deformation schemes play an important role in numerical aerodynamic optimization. As the aerodynamic shape changes, the computational mesh must adapt to conform to the deformed geometry. This work presents an extension to an existing fast and robust radial basis function mesh movement scheme. Using a reduced set of surface points to define the mesh deformation increases the efficiency of the radial basis function method; however, it does so at the cost of introducing errors into the parameterization by not recovering the exact displacement of all surface points. A secondary mesh movement is implemented, within an adjoint-based optimization framework, to eliminate these errors. The mesh sensitivity is based on a combination of both the primary and secondary mesh movement schemes. The proposed scheme is demonstrated through three cases within a three-dimensional Euler flow: 1) the reduction of pressure drag at constant lift on the Onera M6 wing; 2) an inverse pressure design on the Onera M6; and 3) a drag minimization of the Boeing 747 wing-body aircraft.

Forest management activities are increasingly analyzed through a lens that quantifies their effects on soil carbon (C) and nitrogen (N) storage because forest soils are an important C sink. Data on the longer-term impacts of repeated interventions are often lacking. At the Petawawa Research Forest, Ontario, Canada, treatments to evaluate the effect of repeated thinnings on wood quality of red pine (Pinus resinosa Aiton) and white pine (Pinus strobus L.) were initiated in 1918 with the first experimental plots in Canada: permanent sample plots 1 (thinned) and 2 (control). In 2005, 16 years after the last thinning in 1989, we observed that repeated thinnings reduced soil C and N stocks in the surface L, F, and Ah horizons. Contrary to our hypotheses, concentrations and stocks of C and N increased in the Bm1 horizon, indicating that these elements could be accumulated in deeper horizons after surface disturbance and potentially increased decomposition associated with thinning. However, total C and N accumulation in the profile to 30 cm contributed to reduced storage (–35% for C and –30% for N). Many forest sites in the Great Lakes Forest Region that are selectively cut repeatedly over decades could experience this level of soil C and N decline.