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Biochar amendment has been shown to reduce nitrous oxide (N 2 O) emissions from acidic soils in tea plantations. Given that both soil bacterial and fungal denitrifications can produce N 2 O, their relative contributions to the decrease in N 2 O emissions following biochar amendment remain unclear. Here, we examined soils sampled from a subtropical tea plantation that had received 2 years of biochar amendment. Measurements of the relative contributions of fungi and bacteria to N 2 O production were taken by the substrate-induced respiration method implemented with the addition of selective inhibitors. The abundances of total fungi, bacteria, and key N 2 O-related bacterial genes were quantified by q-PCR, and the composition of the fungal community was analyzed by 18S rRNA amplicon sequencing. The results showed that the contribution of fungi to N 2 O production (52%) was greater than that of bacteria (18%) for the N-applied acidic soils. Biochar amendment significantly decreased the fungal abundances and the fungal contribution to N 2 O production (by 28%). In contrast, biochar amendment significantly increased the abundances of N 2 O-related bacteria (e.g., ammonia-oxidizing bacteria (AOB), nirS , nosZ). Structural equation models (SEMs) revealed that biochar decreased the fungal contribution to N 2 O production through enhancing the soil pH and shifting the fungal community composition. Our results highlight that the decreased N 2 O emissions could be ascribed to the stimulated N 2 O consumption process (driven by N 2 O-consuming bacteria encoded by the nosZ gene) and suppressed fungal dominance in acidic soils from tea plantations. This study presents relatively comprehensive insights into the regulatory roles of biochar on soil microbe-mediated N 2 O production processes. • Fungi played a more important role than bacteria in N 2 O production from acidic soils. • Biochar shifted the fungal community on genus level from acidic soils. • Biochar decreased the fungal contribution to N 2 O production. [ABSTRACT FROM AUTHOR]

Tailoring agricultural practices to enhance the soil carbon (C) stock is seen as a promising mitigation tactic to offset greenhouse gas (GHG) emissions in croplands. Tea plantations are not only the important part of economic industry but also one of the crucial agricultural sources of non-carbon dioxide emissions. Although many studies have measured GHG emissions from tea plantations, it remains unknown about the effect of knowledge-based mitigation options on the entire C budget from Chinese rapidly expanding tea plantations. Thus, we carried out a 2-year field trial to provide an insight into the influence of organic fertilizer substitution for synthetic fertilizer and biochar amendment on net ecosystem carbon budget (NECB), net greenhouse gas budget (NGB), and yield-scaled greenhouse gas intensity (GHGI) from a subtropical tea plantation. Results showed that when averaged a 2-year experimental period, both full organic substitution and biochar amendment contributed significantly to the increment in NECB, mainly due to the enhanced soil organic C content in the tea field. Compared with the conventional farm practice, the application of full organic substitution can induce a 52% decrease in both NGB and GHGI. Regardless of fertilizer type, both NGB and GHGI were negative and 2.4 times lower in the treatments with biochar amendment relative to the control. In addition to their roles in maintaining soil health and alleviating soil acidification, our results suggest that organic fertilizer substitution and biochar addition may achieve low carbon development for tea plantations. Our findings will inform efforts to implement and evaluate these tailored mitigation options in tea plantations at a national scale. • The net greenhouse gas budget was assessed in a tea plantation over two years. • Organic substitution and biochar amendment decreased net greenhouse gas budget. • Organic substitution and biochar contributed to lowering yield-scaled emission. [ABSTRACT FROM AUTHOR]

The mangrove restoration wetland project in Jinjiang Estuary, Fujian Province, was started in April 2014, and the wetland was restored using vegetation restoration technology. Prior to restoration, the area was a mix of Spartina alterniflora beaches, muddy beaches, and abandoned quarries, which were not environmentally robust. Six species of mangrove plants were used in the wetland, including Kandelia obovata , Aegiceras corniculatum , Avicennia marina , Acanthus ilicifolius , Bruguiera gymnorhiza , and Rhizophora stylosa. The plants were planted according to three mixed patterns and three planting densities. Finally, the whole wetland was divided into 27 plots, and three plant-free control areas were set up in the area close to the vegetation area. In this study, 30 topsoil samples were collected (April 2019), fraction concentrations of heavy metals (Cu, Cr, Zn, and Pb), and their bioavailability and spatial distributions were determined, and the relationships between their fractions and planting patterns were analyzed. The results showed that among the nine planting patterns, the pattern " A-K-C , 0.5×0.5 m" was the most different from the other models, and the fraction of most heavy metals obtained the lowest value of soil metal content in this model. The secondary-phase fraction (SPF) of heavy metals, including acid-soluble, reducible, and oxidizable fractions, is considered to be a direct and potentially hazardous fraction to organisms. In this study, Cu, Zn, and Pb had the greatest SPFs among all the metals (35.29, 33.45, and 51.58%, respectively). Compared with the relevant results before restoration, it was found in after five years of mangrove restoration, the SPF of Cu, Cr, Zn and Pb decreased by 41.31, 22.89, 27.06, and 22.13%, respectively, indicating that the direct and potential toxicity of these four elements to the environment decreased. The risk of heavy metal release decreased from medium and high pollution levels to low pollution levels or even no pollution levels. For most metals, the fraction distributions were controlled by clay, silt, pH, and soil organic matter. The research methods and results can provide a theoretical and scientific basis for further study of wetland vegetation, and in addition, aid in selecting feasible restoration methods for further wetland restoration. [ABSTRACT FROM AUTHOR]

The response of stable and labile C pools to global warming is uncertain, especially in paddy soils with very low oxygen availability and the dominance of electron acceptors with low efficiency. To clarify the response of organic matter decomposition to warming, flooded paddy soil was incubated at four temperatures (5, 15, 25, and 35 °C) for 75 days. The 13C-labelled Na-acetate was used as an analogue for root exudates and as a methane (CH 4) source. Soil with acetate had higher C availability to microorganisms leading to 2–2.7 times and 2–153 times higher emission of carbon dioxide (CO 2) and CH 4 on day 75 than from soil without acetate, respectively. Incubation temperature explained >40% of the variance of CO 2 and CH 4 effluxes. Acetate stimulated microbial activities and turnover and so, increased soil organic matter (SOM) mineralisation in the first week, especially at low temperatures (<15 °C) with slow acetate consumption and longer oxygen (O 2) availability. The priming effects measured as CH 4 emissions were especially sensitive to temperatures from 5 to 15 °C. The high Q 10 value of primed CH 4 (Q 10 > 10) at low temperature indicates that flooded paddy fields will contribute greatly to the greenhouse effect in warm winters, which have become common from 1970s. Caution is necessary for interpretations of previous estimates of the temperature sensitivity of SOM decomposition because the priming effect was ignored, especially that of CH 4 under the condition of limited O 2 availability in paddy and other wetland soils. [ABSTRACT FROM AUTHOR]

Boron-containing mesoporous bioactive glass (B-MBG) scaffolds could be capable of promoting osteogenesis by activating Wnt/β-catenin signaling pathway during the process of bone defect repair. Despite this, more involving molecular controls are still largely unclear. In the present study, we identified that the downstream of Wnt/β-catenin signaling pathway named transcription factor 7-like 2 (TCF7L2) served as a key effector to promote boron-induced bone regeneration and osteogenesis through lipocalin 2 (LCN2). TCF7L2 was highly expressed in osteoblasts when treated with B-MBG scaffold extraction than MBG. LCN2, as a secreted bone factor, positively affected osteogenic differentiation of MC3T3-E1 and osteogenesis in vivo , which could be induced by TCF7L2. In addition, interference of TCF7L2 decreased the osteogenic differentiation of osteoblasts. Finally, we identified that rLCN2 could rescue the poor ability of osteogenic differentiation of MC3T3-E1 whose Tcf7l2 gene was knocked down by lentiviral transfection of shRNA. Our findings provide some new insights into the molecular controls of boron-associated bone regeneration and potential therapeutic targets for the treatment of bone defects. Unlabelled Image • TCF7L2, the downstream of β-catenin in Wnt/β-catenin pathway, could promote boron-induced osteogenesis for B-MBG scaffolds. • TCF7L2 had positive effects on osteogenesis during the process of normal bone development. • The positive role of TCF7L2 for boron-induced and normal osteogenesis related to the increasing of LCN2 in osteoblasts. • LCN2 played a positive role in osteogenic differentiation in osteoblasts as the downstream of TCF7L2. • Recombinant LCN2 could rescue the poor ability of osteogenic differentiation in MC3T3-E1 lacking tcf7l2 gene. [ABSTRACT FROM AUTHOR]