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Examines the effects of land conversion and cultivation on belowground biomass and organic carbon. Measurement of belowground biomass and soil organic carbon (SOC) content; Estimation of SOC loss; Relationship between root growth and SOC dynamics. more...

The low-molecular-weight organic acids (LMWOAs) secreted by plant roots modify the mobility of Cd through formation of soluble complexes in the soil rhizosphere; the kinetics of Cd release as influenced by organic acids and its impact on Cd bioaccumulation remains to be established. The influence of LMWOAs (10{sup}-3{end} and 10{sup}-2{end} M), viz., acetic, citric, oxalic, fumaric, and succinic acids, which are present in the soil rhizosphere, on the kinetics of Cd release from selected soils (Luseland, Waitville, and Jedbergh) of Saskatchewan,Canada, was investigated at 25 deg.C and at an ionic strength of 0.1M NaNO{sub}3{end}. It was observed that the Cd release from the soils increased initially up to a reaction period of about 2 h and then slowly decreased with time. With time, the LMWOAs were apparently microbially degraded and the soil solution Cd{sup}2+{end} , which was transformed from the CD-LMWOA complexes by microbial degradation, was adsorbed onto the negatively charged soil particles. Increasing amountsof Cd were released from the soils to the soil solution with the renewal of LMWOAs after every 2 h. The short-term (reaction period of 0.25 to 1 h) kinetics of Cd release from the soils was described by a parabolic diffusion kinetic model. The overall diffusion coefficient of the Cd release from the soil and the Cd released by the renewal of LMWOAs followed the same trend as the Cd availability index of the soils: Luseland greater than greater than Waitville greater than Jedbergh. Thus, the results presented in this investigation indicate the importance of the kinetics of the Cd release from the soils by the LMWOAs excreted by root exudates in understanding the availability of soil Cd. [ABSTRACT FROM AUTHOR] more...

α-Phenylthioaldehydes are readily prepared using a simple multi-step procedure and herein are introduced as a new precursor for the NHC-catalysed generation of acyl azolium and azolium enolate intermediates that are of widespread synthetic interest and utility. Treatment of α-phenylthioaldehydes with an NHC precatalyst and base produces an efficient redox rearrangement via a Breslow intermediate, elimination of thiophenolate, and subsequent rebound addition to the generated acyl azolium to give the corresponding thiol ester. In the presence of an external alcohol, competition between redox rearrangement and redox esterification can be controlled through judicious choice of the N -aryl substituent within the NHC precatalyst and the base used in the reaction. With NEt 3 as base, NHCs bearing electron-withdrawing ( N -C 6 F 5 or N -C 6 H 2 Cl 3 ) substituents favour redox rearrangement, while triazolium precatalysts with electron-rich N -aryl substituents ( N -Ph, N -Mes) result in preferential redox esterification. Using DBU, redox esterification is preferred due to transesterification of the initially formed thiol ester product. Additionally, α-phenylthioaldehyde-derived azolium enolates have been used in enantioselective formal [4 + 2]-cycloaddition reactions to access dihydropyridinone heterocycles with high enantioselectivity (up to >95 : 5 dr, 98 : 2 er)., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.) more...

The uranyl complex U VI O 2 Cl( L Mes ) of the redox-active, acyclic dipyrrin-diimine anion L Mes - [H L Mes = 1,9-di- tert -butyl-imine-5-(mesityl)dipyrrin] is reported, and its redox property is explored and compared with that of the previously reported U VI O 2 Cl( L F ) [H L F = 1,9-di- tert -butyl-imine-5-(pentafluorophenyl)dipyrrin] to understand the influence of the meso substituent. Cyclic voltammetry, electron paramagnetic resonance spectroscopy, and density functional theory studies show that the alteration from an electron-withdrawing meso substituent to an electron-donating meso substituent on the dipyrrin ligand significantly modifies the stability of the products formed after reduction. For U VI O 2 Cl( L Mes ), the formation of a diamond-shaped, oxo-bridged uranyl(V) dimer, [U V O 2 ( L Mes )] 2 is seen, whereas in contrast, for U VI O 2 Cl( L F ), only ligand reduction occurs. Computational modeling of these reactions shows that while ligand reduction followed by chloride dissociation occurs in both cases, ligand-to-metal electron transfer is favorable for U VI O 2 Cl( L Mes ) only, which subsequently facilitates uranyl(V) dimerization. more...

There is interest in utilizing wood ash as an amendment in forestry operations as a mechanism to return nutrients to soils that are removed during harvesting, with the added benefit of diverting this bioenergy waste material from landfill sites. Existing studies have not arrived at a consensus on what the effects of wood ash amendments are on soil biota. We collected forest soil samples from studies in managed forests across Canada that were amended with wood ash to evaluate the effects on arthropod, bacterial and fungal communities using metabarcoding of F230, 16S, 18S and ITS2 sequences as well as enzyme analyses to assess its effects on soil biotic function. Ash amendment did not result in consistent effects across sites, and those effects that were detected were small. Overall, this study suggests that ash amendment applied to managed forest systems in amounts (up to 20 Mg ha -1 ) applied across the 8 study sties had little to no detectable effects on soil biotic community structure or function. When effects were detected, they were small, and site-specific. These non-results support the application of wood ash to harvested forest sites to replace macronutrients (e.g., calcium) removed by logging operations, thereby diverting it from landfill sites, and potentially increasing stand productivity., (© 2022. The Author(s).) more...

The uranyl complexes UO 2 (OAc)( L ) and UO 2 Cl( L ) of the redox-active, acyclic diamido-dipyrrin anion L - </superscript> are reported and their redox properties explored. Because of the inert nature of the complexes toward hydrolysis and oxidation, synthesis of both the ligands and complexes was conducted under ambient conditions. Voltammetric, electron paramagnetic resonance spectroscopy, and density functional theory studies show that one-electron chemical reduction by the reagent CoCp 2 leads to the formation of a dipyrrin radical for both complexes [Cp 2 Co][UO 2 (OAc)( L • )] and [Cp 2 Co][UO 2 Cl( L • )]. more...

There is a significant knowledge gap in the area of management of the vast shelterbelt network currently existing on agricultural lands in Canada and across the world. Throughout eight decades of shelterbelt planting in Saskatchewan, Canada, there are no available records of shelterbelt management practices used by land managers, such as herbicides (H), fertilizers (F), irrigation (I), or tillage (T) applications, collectively referred to as HFIT management. The main objective of this large-scale study was to quantify the effects of HFIT management on shelterbelt carbon sequestration for six common tree and shrub species. Field data from 303 randomly selected shelterbelts across millions of hectares of agricultural land in three soil zones were combined with existing shelterbelt carbon stock curves for Saskatchewan, produced by a shelterbelt carbon management support tool, Belt-CaT, to estimate site-specific total ecosystem carbon (TEC) stocks. Estimated TEC stocks and annual rates for HFIT sites were compared to the no management sites used as a reference. HFIT management increased carbon stocks for the majority of species, four of six, resulting in higher TEC at any tree spacing, mostly at higher suitability sites. However, HFIT management effects were not consistent across individual species, land suitability, or planting designs. The top three HFIT management combinations for hybrid poplar were IT, HIT, and HI, for white spruce they were FT, IT, and FIT, and only FT benefited caragana shelterbelts. The lack of management practices makes unmanaged shelterbelts more unpredictable and unreliable, in terms of tree growth and carbon stocks sequestration potential., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.) more...

A new constrained-cavity [1 + 1] Schiff-base dipyrrin macrocycle comprising an N4 donor-pocket has been synthesised by spontaneous oxidation and in situ crystallisation. Access to Fe(ii) and Zn(ii) complexes is achieved by salt elimination reactions of the lithium salt. All compounds have been characterised by NMR and UV-vis spectroscopy, X-ray crystallography, and DFT analysis. more...