https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37752 Thu 14 Mar 2024 08:41:00 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:9864 Sat 24 Mar 2018 08:14:32 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:20176 Sat 24 Mar 2018 07:51:44 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:18801 137Cs at two neighbouring field sites sharing the same land management history but comprising clay soils with different cracking characteristics (cracking black Vertisol and a red Luvisol). A finite element model (FEM) simulation of the vertical transport of SOC and ¹³⁷Cs was developed for each site which accommodates the differing spatial and temporal trends of input and decay of the two species. From these models the diffusion and convection coefficients which best describe the movement of ¹³⁷Cs at each site were determined. Both convection and diffusion coefficients were found to be substantially higher in cracking Vertisol soils (D_Cs = 721 mm2/yr, V_Cs = − 0.84 mm/yr) than in the neighbouring Luvisol soils (D_Cs = 94 mm2/yr, V_Cs = 0 mm/yr). Finally the ¹³⁷Cs transport coefficients determined for each site were used in modelling the SOC profile. The excellent match between predicted and observed SOC profiles suggests that transport of the SOC and ¹³⁷Cs down the soil column at the Luvisol site follows the same pathways. While the match between predicted and observed SOC profiles at the Vertisol site was weaker this was concluded to be more likely due to the impact of extensive soil cracking which is not explicitly accounted for in the SOC FEM rather than the result of the use of ¹³⁷Cs transport coefficients.]]> Sat 24 Mar 2018 07:51:04 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30741 13CO₂ pulse labelling of ryegrass was used to monitor belowground C allocation, SOC priming, and stabilization of root-derived C for a 15-month period—commencing 8.2 years after biochar (Eucalyptus saligna, 550 °C) was amended into a subtropical ferralsol. We found that field-aged biochar enhanced the belowground recovery of new root-derived C (¹³C) by 20%, and facilitated negative rhizosphere priming (it slowed SOC mineralization by 5.5%, that is, 46 g CO₂-C m⁻² yr⁻¹). Retention of root-derived ¹³C in the stable organo-mineral fraction (<53 μm) was also increased (6%, P < 0.05). Through synchrotron-based spectroscopic analysis of bulk soil, field-aged biochar and microaggregates (<250 μm), we demonstrate that biochar accelerates the formation of microaggregates via organo-mineral interactions, resulting in the stabilization and accumulation of SOC in a rhodic ferralsol.]]> Sat 24 Mar 2018 07:39:28 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27735 137Cs and ²¹⁰Pb were assessed with the aim of better understanding the transport processes which produce the observed vertical distribution of SOC. While no consistent relationship was found between SOC and soil physical properties significant relationships were found between the distribution of SOC and the environmental tracers, ¹³⁷Cs and ²¹⁰Pb. Finite element simulations based on a diffusion/convection/decay model showed that the transport of ¹³⁷Cs and ²¹⁰Pb down the soil profile is likely to be driven by the same (primarily diffusive) processes. The same model used in conjunction with plant input and decay data generated from the RothC-26.3 soil carbon model revealed that transport of SOC down the soil profile, while also a diffusion process, was significantly slower indicating that different processes and/or pathways are involved in SOC transport at this site.]]> Sat 24 Mar 2018 07:27:46 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38226 75 μm), was 13.4% higher under CT, but mesoporosity (30–75 μm) was 9.6% higher under NT. The vertical distributions of root biomass and root architecture measurements (i.e. root length density) in undisturbed soil cores were 9.6% higher under the NT and 8.7% higher under the CT system respectively. These results suggest that low soil disturbance under the continuous NT system may have encouraged accumulation of more root biomass in the top 100 mm depth, thus developing better soil structure. Overall, µXCT image analyses of soil cores indicated that this tillage shift affected the soil total carbon, due to the significantly higher soil-pore (i.e. pore surface area, porosity and average pore size area) and root architecture (i.e. root length density, root surface density and root biomass) measurements under the CT system.]]> Mon 16 Aug 2021 15:47:54 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38539 -1 yr^-1) compare well with independently determined erosion rates using ¹³⁷Cs (2.1 to 3.4 t ha^-1 yr^-1). We also investigate field measured and modelled soil organic carbon movement using the LEM in relation to predicted erosion and deposition patterns and find that erosion and deposition patterns are related to the spatial patterns of SOC. This is the first time that a DEM based LEM has been shown to provide reliable prediction of not just soil erosion but also SOC. The results demonstrate that the majority of SOC is being transported in the near surface soil layer (top 2 cm) and that turnover at greater depths is slower and does not correspond with any modelled patterns. The modelled erosion and deposition suggests that on average 0.06 t ha^-1 yr^-1 of SOC is exported by erosion from the hillslope assuming a good vegetation cover. However if the hillslope is subjected to disturbance (i.e. tillage, overgrazing) then the site will export 0.46 t ha^-1 yr^-1of SOC. Laboratory results using flume suggest that there was no enrichment of SOC in the eroded sediment. The methods outlined here provide a new approach to quantify the dynamic movement of sediment and SOC at both the hillslope and catchment scale.]]> Fri 29 Oct 2021 14:14:00 AEDT ]]>