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Purpose: The chemistry of soil organic matter (SOM) is fundamental for sustainable and climate-smart agroecosystems. However, the differences in SOM chemistry between the upland and paddy soils developing under the same climatic and edaphic conditions are unclear. Materials and methods: Py-GC/MS was applied to characterize the biochemical features of SOM in three physical size fractions: coarse particulate (> 0.25 mm, cPOM), fine particulate (0.053–0.25 mm, fPOM), and mineral-associated OM (< 0.053 mm, MAOM) of upland and paddy fields under long-term (> 30 years) mineral and manure fertilizations. Results and discussion: Paddy fields had higher contents of soil organic carbon (SOC) and total nitrogen (TN) mainly accumulated in MAOM fraction than uplands. These two soils had different molecular compositions of SOM: N-containing compounds including amino-N and heterocyclic-N compounds enriched in the uplands, whereas paddy had higher proportions of lipids and phenolics. The SOM composition was also dependent on particle size, especially in the uplands, where POM fractions had high contents of lignin and MAOM accumulated N-containing components. In contrast, POM in paddy accumulated polysaccharides, whereas MAOM was enriched with lipids. Particle size controlled the C oxidation state (Cox), and paddy soils had higher Cox than that of uplands, mainly in the MAOM fraction. Conclusions: The molecular composition SOM was primarily regulated by land-use type, following by fraction size and fertilization regime, while the Cox was controlled by fraction size. The Cox needs more attention to understand the direction of formation of SOM fractions. [ABSTRACT FROM AUTHOR]

Copper (Cu) is a bio-essential element and a potentially toxic pollutant in the plant–soil systems. Analysis of stable Cu isotopes can be a powerful tool for tracing the biogeochemical cycling of Cu in plant–soil systems. In this review, we examined the analysis method of stable Cu isotope ratios in plants and soils, and discussed the biogeochemical processes, including redox reactions, mineral dissolution, abiotic and biotic sorption, which fractionate Cu isotopes in plant–soil systems. We also reviewed the variability of the isotopic signature in different plants and plant tissues, as well as different soil types and profiles to discuss the relationship between the biogeochemical transformation of Cu and its isotope fractionation in plant–soil systems. The collected data show that δ65Cu values range from − 2.59 to + 1.73‰ in plant–soil systems, and ∆65Cu values range from − 1.00 to − 0.11‰ between the plant and soil. The variation in the ∆65Cu value between the plant and soil is mainly in response to the different uptake strategies during the acquisition of Cu from soils. Cu isotope analyses are proved to be a suitable technique during the biogeochemical transformation of Cu in plant–soil systems, especially during redox reactions. Ultimately, research challenges and future directions for Cu isotope techniques as a proxy for Cu biogeochemical cycles are also proposed. This review is beneficial for soil safety, food safety, and the sustainable development of agriculture and human health. [ABSTRACT FROM AUTHOR]

Aims: Previous studies have shown that silicon (Si) can affect plant growth and yield by regulating the availability of other nutrients. However, the mechanisms by which Si affects plant biomass accumulation in coastal wetlands are not well explored.We conducted a sampling campaign across the whole growing season of Phragmites australis under waterlogging and drought conditions in coastal wetland, and quantified the effects of Si availability on biomass accumulation.Compared with drought condition, the waterlogged condition improved the utilization efficiency of nitrogen (N) and phosphorus (P) of P. australis regulated by higher Si contents. Meanwhile, the increased Si contents promoted the utilization of N and P in leaf, suggesting that the increase in Si contents optimizes the photosynthetic process. Lignin contents in P. australis decreased with the increasing Si contents, which confirmed that Si can replace structural carbon components. In addition, principal component analysis (PCA) showed aboveground biomass accumulation of P. australis was synchronized with Si accumulation, indicating that Si was a beneficial element to promote biomass accumulation.Our study implies that increasing Si availability is conducive to biomass accumulation of P. australis in waterlogged wetlands, which will provide important scientific references for the management of coastal wetland ecosystem and the increase of global ‘blue carbon’ sequestration.Methods: Previous studies have shown that silicon (Si) can affect plant growth and yield by regulating the availability of other nutrients. However, the mechanisms by which Si affects plant biomass accumulation in coastal wetlands are not well explored.We conducted a sampling campaign across the whole growing season of Phragmites australis under waterlogging and drought conditions in coastal wetland, and quantified the effects of Si availability on biomass accumulation.Compared with drought condition, the waterlogged condition improved the utilization efficiency of nitrogen (N) and phosphorus (P) of P. australis regulated by higher Si contents. Meanwhile, the increased Si contents promoted the utilization of N and P in leaf, suggesting that the increase in Si contents optimizes the photosynthetic process. Lignin contents in P. australis decreased with the increasing Si contents, which confirmed that Si can replace structural carbon components. In addition, principal component analysis (PCA) showed aboveground biomass accumulation of P. australis was synchronized with Si accumulation, indicating that Si was a beneficial element to promote biomass accumulation.Our study implies that increasing Si availability is conducive to biomass accumulation of P. australis in waterlogged wetlands, which will provide important scientific references for the management of coastal wetland ecosystem and the increase of global ‘blue carbon’ sequestration.Results: Previous studies have shown that silicon (Si) can affect plant growth and yield by regulating the availability of other nutrients. However, the mechanisms by which Si affects plant biomass accumulation in coastal wetlands are not well explored.We conducted a sampling campaign across the whole growing season of Phragmites australis under waterlogging and drought conditions in coastal wetland, and quantified the effects of Si availability on biomass accumulation.Compared with drought condition, the waterlogged condition improved the utilization efficiency of nitrogen (N) and phosphorus (P) of P. australis regulated by higher Si contents. Meanwhile, the increased Si contents promoted the utilization of N and P in leaf, suggesting that the increase in Si contents optimizes the photosynthetic process. Lignin contents in P. australis decreased with the increasing Si contents, which confirmed that Si can replace structural carbon components. In addition, principal component analysis (PCA) showed aboveground biomass accumulation of P. australis was synchronized with Si accumulation, indicating that Si was a beneficial element to promote biomass accumulation.Our study implies that increasing Si availability is conducive to biomass accumulation of P. australis in waterlogged wetlands, which will provide important scientific references for the management of coastal wetland ecosystem and the increase of global ‘blue carbon’ sequestration.Conclusions: Previous studies have shown that silicon (Si) can affect plant growth and yield by regulating the availability of other nutrients. However, the mechanisms by which Si affects plant biomass accumulation in coastal wetlands are not well explored.We conducted a sampling campaign across the whole growing season of Phragmites australis under waterlogging and drought conditions in coastal wetland, and quantified the effects of Si availability on biomass accumulation.Compared with drought condition, the waterlogged condition improved the utilization efficiency of nitrogen (N) and phosphorus (P) of P. australis regulated by higher Si contents. Meanwhile, the increased Si contents promoted the utilization of N and P in leaf, suggesting that the increase in Si contents optimizes the photosynthetic process. Lignin contents in P. australis decreased with the increasing Si contents, which confirmed that Si can replace structural carbon components. In addition, principal component analysis (PCA) showed aboveground biomass accumulation of P. australis was synchronized with Si accumulation, indicating that Si was a beneficial element to promote biomass accumulation.Our study implies that increasing Si availability is conducive to biomass accumulation of P. australis in waterlogged wetlands, which will provide important scientific references for the management of coastal wetland ecosystem and the increase of global ‘blue carbon’ sequestration. [ABSTRACT FROM AUTHOR]