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- Liu, Linan, et al.
(författare)
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Silicon Effects on Biomass Carbon and Phytolith-Occluded Carbon in Grasslands Under High-Salinity Conditions
- 2020
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Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 11, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Changes in climate and land use are causing grasslands to suffer increasingly fromabiotic stresses, including soil salinization. Silicon (Si) amendment has been frequentlyproposed to improve plant resistance to multiple biotic and abiotic stresses and increaseecosystem productivity while controlling the biogeochemical carbon (C) cycle. However,the effects of Si on plant C distribution and accumulation in salt-suffering grasslandsare still unclear. In this study, we investigated how salt ions affected major elementalcomposition in plants and whether Si enhanced biomass C accumulation in grasslandspecies in situ. In samples from the margins of salt lakes, our results showed that thediffering distance away from the shore resulted in distinctive phytocoenosis, includinghalophytes and moderately salt-tolerant grasses, which are closely related to changingsoil properties. Different salinity (NaC/KC, ranging from 0.02 to 11.8) in plants causednegative effects on plant C content that decreased from 53.9 to 29.2% with theincrease in salinity. Plant Si storage [0.02–2.29 g Si m?2 dry weight (dw)] and plantSi content (0.53 to 2.58%) were positively correlated with bioavailable Si in soils(ranging from 94.4 to 192 mg kg?1). Although C contents in plants and phytoliths werenegatively correlated with plant Si content, biomass C accumulation (1.90–83.5 g Cm?2 dw) increased due to the increase of Si storage in plants. Plant phytolith-occludedcarbon (PhytOC) increased from 0.07 to 0.28h of dry mass with the increase of Sicontent in moderately salt-tolerant grasses. This study demonstrates the potential ofSi in mediating plant salinity and C assimilation, providing a reference for potentialmanipulation of long-term C sequestration via PhytOC production and biomass Caccumulation in Si-accumulator dominated grasslands.
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| 3. |
- Wang, Tao, et al.
(författare)
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Determination of carbonate-C in biochars
- 2014
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Ingår i: Soil Research. - 1838-675X. ; 52:5, s. 495-504
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Tidskriftsartikel (refereegranskat)abstract
- Although carbonate-carbon (C), an integral part of biochar-C, contributes to the liming properties of that material, it also interferes with the estimation of the stable organic C fraction in biochars. In this study, four methods were compared in order to quantify the carbonate-C in biochars: two direct (a titrimetric procedure and thermogravimetric analysis, TGA), and two indirect (acid treatment with separation by filtration and acid fumigation). The titrimetric method showed a high recovery of added carbonate-C (average 98.8%, range 1.5-38 mg), and the standard deviations of carbonate-C for all biochars tested were <0.1% when 1 g of sample was used. The acid treatment with a filtration step overestimated the carbonate-C content (on average by a 4-fold increment) due to the loss of dissolved or fine particulate organic C during filtration. The acid fumigation method was suitable for biochars containing high amount of carbonate-C (>0.3% wt) and when the isotopic signature of organic C in biochars is to be determined. The TGA method (either in N-2 or a dry air atmosphere) was reliable when calcite was the main carbonate form in biochars, but was inadequate for samples containing a considerable amount of whewellite and certain carbonate-bearing minerals (e. g. magnesite) that decompose at <600 degrees C. Because more than half of the biochar samples investigated in the literature and in this study (58% of the 117 samples) contained <0.4% carbonate-C (and 38% of these contained no detectable carbonate-C), low-cost screening methods were developed to identify the biochars needed for carbonate-C analysis. For this purpose, two methods were proposed: (i) a manometric test; and (ii) a ratio between predicted fixed C : total C (FC/TC) and measured FC/TC, where predicted FC/TC was estimated using the following relationship: (FC/TC) = -0.1081(H/C)(2) - 0.1794(H/C) + 1.0097, as derived from values obtained in the literature. A decision tree, including two steps (a screening step and a titrimetric procedure) could be used to determine accurately the carbonate-C in biochars.
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| 4. |
- Xia, Shaopan, et al.
(författare)
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Distribution, sources, and decomposition of soil organic matter along a salinity gradient in estuarine wetlands characterized by C:N ratio, δ13C-δ15N, and lignin biomarker
- 2021
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 27:2, s. 417-434
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Tidskriftsartikel (refereegranskat)abstract
- Despite increasing recognition of the critical role of coastal wetlands in mitigating climate change, sea‐level rise, and salinity increase, soil organic carbon (SOC) sequestration mechanisms in estuarine wetlands remain poorly understood. Here, we present new results on the source, decomposition, and storage of SOC in estuarine wetlands with four vegetation types, including single Phragmites australis (P, habitat I), a mixture of P. australis and Suaeda salsa (P + S, habitat II), single S. salsa (S, habitat III), and tidal flat (TF, habitat IV) across a salinity gradient. Values of δ13C increased with depth in aerobic soil layers (0–40 cm) but slightly decreased in anaerobic soil layers (40–100 cm). The δ15N was significantly enriched in soil organic matter at all depths than in the living plant tissues, indicating a preferential decomposition of 14N‐enriched organic components. Thus, the kinetic isotope fractionation during microbial degradation and the preferential substrate utilization are the dominant mechanisms in regulating isotopic compositions in aerobic and anaerobic conditions, respectively. Stable isotopic (δ13C and δ15N), elemental (C and N), and lignin composition (inherited (Ad/Al)s and C/V) were not completely consistent in reflecting the differences in SOC decomposition or accumulation among four vegetation types, possibly due to differences in litter inputs, root distributions, substrate quality, water‐table level, salinity, and microbial community composition/activity. Organic C contents and storage decreased from upstream to downstream, likely due to primarily changes in autochthonous sources (e.g., decreased onsite plant biomass input) and allochthonous materials (e.g., decreased fluvially transported upland river inputs, and increased tidally induced marine algae and phytoplankton). Our results revealed that multiple indicators are essential to unravel the degree of SOC decomposition and accumulation, and a combination of C:N ratios, δ13C, δ15N, and lignin biomarker provides a robust approach to decipher the decomposition and source of sedimentary organic matter along the river‐estuary‐ocean continuum.
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