Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Three years of biochar amendment alters soil physiochemical properties and fungal community composition in a black soil of northeast China
No full textAlthough biochar amendment has been extensively evaluated as a promising strategy to improve soil quality, most evaluations have been conducted in the laboratory or under short-term field conditions, which restricted us to understand the long-term effects of biochar as a soil amendment. As the residence time of biochar in soils is expected to be hundreds to thousands of years, this study focused on revealing whether biochar addition influences soil physiochemical properties and fungal community composition in a black soil of northeast China over the long term. Biochar was added to the micro-plots at 0%, 2%, 4%, and 8% of the total mass of the top 20 cm of the soil in the spring of 2012, and soil samples were collected seasonally four times in 2014. The results indicate that soil pH, moisture, total C, total N, total P,NO3--n available K and the C/N ratio significantly increased but soil bulk density and total K content decreased with biochar addition. The soil fungal abundance determined using quantitative real-time PCR showed that the number of fungal ITS gene copies increased with biochar addition. The soil fungal community composition determined using the Illumina MiSeq sequencing method showed that community diversity was not influenced by biochar addition but the community composition was influenced. The impact of biochar on changes in community composition was not reflected at the phylum level, but at the genus and operational taxonomic units (OTU) levels. The relative abundance of Fusarium decreased, but Gue-homyces increased with biochar addition over the first three sampling dates. The relative abundances of several OTUs classified as potential crop pathogens decreased with biochar addition, suggesting that biochar amendment may be beneficial in terms of suppressing the occurrence of crop disease over the long term. In addition, canonical correspondence analysis indicated that fungal community composition was associated with soil parameters such as pH, soil moisture, total C, total N, total K and available K. The changes in these soil characteristics were highly correlated with the amounts of biochar addition, suggesting that the impacts of long-term biochar amendment on the soil fungal community occurred indirectly as a result of the alteration of soil physiochemical properties. (C) 2017 Elsevier Ltd. All rights reserved
Elevated CO2 Increases Nitrogen Fixationat the Reproductive Phase Contributing to Various Yield Responses of Soybean Cultivars
No full textNitrogen deficiency limits crop performance under elevated CO2 (eCO(2)), depending on the ability of plant N uptake. However, the dynamics and redistribution of N-2 fixation, and fertilizer and soil N use in legumes under eCO(2) have been little studied. Such an investigation is essential to improve the adaptability of legumes to climate change. We took advantage of genotype-specific responses of soybean to increased CO2 to test which N-uptake phenotypes are most strongly related to enhanced yield. Eight soybean cultivars were grown in open-top chambers with either 390 ppm (aCO(2)) or 550 ppm CO2 (eCO(2)). The plants were supplied with 100 mg N kg(-1) soil as N-15-labeled calcium nitrate, and harvested at the initial seed-filling (R5) and full-mature (R8) stages. Increased yield in response to eCO(2) correlated highly (r = 0.95) with an increase in symbiotically fixed N during the R5 to R8 stage. In contrast, eCO(2) only led to small increases in the uptake of fertilizer-derived and soil-derived N during R5 to R8, and these increases did not correlate with enhanced yield. Elevated CO2 also decreased the proportion of seed N redistributed from shoot to seeds, and this decrease strongly correlated with increased yield. Moreover, the total N uptake was associated with increases in fixed-N per nodule in response to eCO(2), but not with changes in nodule biomass, nodule density, or root length
Duration of farming is an indicator of natural restoration potential of sedge meadows
No full textSoil seed banks can be important components of ecological restoration, particularly if the species remain viable in the soil for long periods of time. A germination experiment was conducted in the greenhouse to determine seed bank viability based on length of time farmed. Soils from sedge meadows farmed between 0 and 50 years were collected in Sanjiang Plain, China. Most dominant sedges (e.g., Carex schmidtii, C. lasiocarpa) and grasses (e.g. Calamagrostis angustifolia) survived as seeds if farmed for less than 5 years, therefore fields farmed for short periods of time are the best candidates for wetland restoration. Certain important structural components (tussock-forming Carex spp.) are not retained in seed banks when farmed for 6-15 years, but the seed banks still contained viable seeds of other important sedge meadow species, which could contribute to the restoration of wetland communities. However, most sedge meadow species were missing in fields farmed for more than 16 years, which make these fields difficult to restore via natural recolonization. We conclude that the duration of farming can be used as a general indicator of the potential of natural restoration for sedge meadows. This information could be used to determine which wetlands might be targeted for restoration
MoS2 nanosheets encapsulating TiO2 hollow spheres with enhanced photocatalytic activity for nitrophenol reduction
No full textCrumpled MoS2 nanosheet encapsulating TiO2 hollow spheres ([email protected]) core@shell three-dimensional (3D) heterojunction are synthesized successfully by in situ growth MoS2 on the surface of TiO2 through hydrothermal process. The core with a hollow structure enhanced light adsorption by multiple reflections in the available inner void space. The outer crumpled MoS2 can increase surface area of the composite. The photocatalytic reduction of [email protected] towards 4-nitrophenol is 99.35%, which is much higher than that of pure TiO2 and MoS2. The enhanced photocatalytic activity of [email protected] attributes to relative low recombination rate of the photogenerated electron-hole pairs. (C) 2017 Elsevier B.V. All rights reserved