https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33595 Thu 22 Nov 2018 13:41:25 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:32600 Mon 23 Sep 2019 11:24:44 AEST ]]> 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 ]]>