https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47549 Wed 28 Feb 2024 15:20:35 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:24908 Wed 11 Apr 2018 13:53:21 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33596 Thu 22 Nov 2018 13:48:22 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:24869 13C-labeled Pinus massoniana leaf litter. An orthogonal experiment with three levels of N (0, 81, and 270 mg N kg^-1 soil) and S (0, 121, and 405 mg S kg^-1 soil) was conducted. We traced the incorporation of ¹³C-litter into carbon dioxide (CO₂), dissolved organic C (DOC), and microbial phospholipids. Over the 420-day incubation, litter decomposition did not respond to low N and S additions but increased under high levels and combined amendments (NS). However, litter-derived CO₂ emissions were enhanced during the first 56 days, with a positive interaction of N x S. N additions promoted fungal growth, while S stimulated growth of Gram-positive bacteria, fungi, and actinobacteria. Increased decomposition was related to higher litter-derived DOC and fungi/bacteria ratio. Inversely, N and/or S amendments inhibited decomposition (N > NS > S) from day 57 afterwards, possibly due to C limitation and decreased abundances of Gram-negative bacteria and actinobacteria. These results suggested that N deposition interacted with S to affect litter decomposition, and this effect depended on N and S deposition levels and litter decomposition stage.]]> Sat 24 Mar 2018 07:11:21 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:24709 −1 soil to arable soils following a 20-year application of compost (CM), inorganic NPK fertilizer (NPK) and a no-fertilizer Control. It was incubated for 30 days to evaluate how the labile substrate affected the microbial abundance and native SOC decomposition. Phospholipid fatty acids (PLFAs) were used as biomarkers for bacteria (Gram-positive bacteria, Gram-negative bacteria and actinobacteria) and fungi. ¹³C-glucose application resulted in a significant increase in microbial abundance and positive priming effect for all treatments. The primed CO₂ flux derived from native SOC peaked on day 11, then increased gradually again from day 15 onwards in all treatments. The increase of abundance peaked on days 7 and 15 for Gram-negative (G⁻) bacteria and Gram-positive (G⁺) bacteria, however, fungal and actinobacterial PLFAs increased steadily from day 3 onwards under all three fertilization regimes. The results suggest that G⁺ and G⁻ bacteria make a greater contribution to priming effects during the first 15 days of incubation, while fungi and actinobacteria are more important at the latter stages. The difference between glucose-derived ¹³C remaining in soils and primed CO₂ from native SOC was 480, 381 and 263 mg C kg⁻¹ in CM, NPK and Control treatments, respectively. Our study demonstrates that the exogenous labile organic substrate addition can more effectively promote C sequestration in organic C-rich soil (CM) than in organic C-poor soil (NPK or Control).]]> Sat 24 Mar 2018 07:11:04 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:32293 Pinus massoniana needles were incubated in a subtropical plantation forest soil exposed to: no amendment (Control), N amendments of 81 (N1) and 270 (N2) mg kg⁻¹, S amendments of 121 (S1) and 405 (S2) mg kg⁻¹ and combined N and S amendments. Litter decomposition was measured as litter-derived carbon dioxide (CO₂) emissions and the litter C pools were partitioned using a two-pool model. Relationships between litter residue chemistry (assessed by ¹³C nuclear magnetic resonance spectroscopy analysis) and microbial community composition (probed by phospholipid fatty acid analysis, PLFA) and activity (the metabolic quotient, qCO₂) were investigated. Over the 420 days incubation period, N and S additions (except N and S addition alone at low rate) significantly increased litter decomposition by 7.2–18.9% compared to the Control. Decomposition was stimulated by 10.2–61.9% during the initial 56 days (stage 1) and in contrast, 8.3–42.1% inhibition was measured during 57–420 days (stage 2) across the addition treatments. Stimulation on litter-derived CO₂ emissions under the N and S additions was largely dependent on the loss of O-alkyl C, a dominant component of the litter active C pool. During the initial 7 days, N and S additions increased the ratio of fungal to bacterial PLFAs compared to the Control, which was accompanied by the increases in methoxyl C. The activity of microbes, particularly gram-negative bacteria, was also increased by N and S additions at stage 1, which was related to di-O-alkyl C. In contrast, fungal activity decreased under N and S additions at stage 2, accompanied by lowered C availability and increased methoxyl C. Alkyl C and aromatic C in the litter had positive relationships with the half-life of the slow C pool. Accordingly, the residue recalcitrance was increased under N and S additions compared with Control at stage 2, and was largely responsible for the inhibition of litter decomposition. Thus, N and S deposition is likely to increase the persistence of litter-derived recalcitrant C in subtropical forest soils in the long term.]]> Mon 21 May 2018 15:09:58 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:34857 Mon 20 May 2019 10:19:39 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37363 2000 μm) from 7.8% in the control to 30.6% while it reduced effective diffusion coefficient of oxygen (DC₀) from 12.58 × 10⁻⁶ m² s⁻¹ in the control to 2.81 × 10⁻⁶ m² s⁻¹. Application of pig manure increased prokaryotic diversity and altered prokaryotic community structure, while crop residues did not. Soil pH was the predominant factor influencing prokaryotic community structure. Bacillales and Clostridiales accounted for 47.5% and 21.4%, respectively of the indicator species in the IPM and the relative abundances of them were increased, compared with the other treatments. Furthermore, the relative abundances of Bacillales and Clostridiales were correlated with SOC, TN, AP and DOC, and negatively with DC₀ in the soil. Overall, our results suggest that application of NPK fertilizer plus pig manure rather than crop residues enhanced soil pH, improved SOC content and aggregation, increased prokaryotic diversity and altered community structure of prokaryote after 27-year fertilization.]]> Mon 19 Oct 2020 10:43:20 AEDT ]]>