Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Stimulation of nitrogen turnover due to nutrients release from aggregates affected by freeze-thaw in wetland soils
No full textThe freeze-thaw phenomenon will occur more frequently in mid-high latitude ecosystems under climate change which has a remarkable effect on biogeochemical processes in wetland soils. Here, we used a wet sieving procedure and a barometric process separation (BaPS) technique to examine the responses of wetland soil aggregates and related carbon and nitrogen turnover affected by the freeze-thaw treatment. Wetland soil samples were divided into a treatment group and a control group. The treatment group was incubated at temperatures fluctuating from 10 degrees C to - 10 degrees C, whereas the control group was incubated at the constant temperature of 10 degrees C. A 24 h process was set as the total freeze-thaw cycle, and the experiment had 20 continuous freeze-thaw cycles. In our results, the freeze-thaw process caused great destruction to the > 2 mm water-stable aggregates (WSA) fraction and increased the 2 mm WSA fraction and the gross nitrification rate can be stimulated at the initial freeze-thaw cycles, nutrients and substrates may play a leading role in the freeze-thaw treatment regardless of the minimal influences on microbial biomass pools. (C) 2016 Elsevier Ltd. All rights reserved
Variation Trend of Dry-Wet Climatic Factors and Correlation with Wetlands in Western Jilin Province, China
No full textThe variation of climate elements and its relationship with wetland landscape in western Jilin Province (WJL) were studied to support decision-making for drought prevention and ecology protection. Mann-Kendall test and linear regression algorithm methods were used to analyze the characteristics of climate change, using a large amount of data of temperature, precipitation, evapotranspiration and dry-wet index, collected from nine monitoring stations during 1960-2014. The results showed that annual temperature and dry-wet index in WJL displayed a ascendant tendency, with the average rate of 0.34 degrees C/10a and 0.14/10a, respectively. The annual precipitation and potential evapotranspiration showed a declining trend; decreasing by about -7.92mm/10a and -3.4mm/10a, respectively. Homogeneous trend was found for temperature and evapotranspiration in the autumn; an increasing trend observed. A sharp declining trend was found in the summer season for precipitation, which was the biggest contributor to the overall decrease of annual precipitation. The spatial distribution of annual and seasonal climate factors indicated that the WJL area is becoming drier, especially in the summer and autumn seasons. The wetland landscape indexes in most regions are significantly correclated with summer precipitation. The significance level for I, II and IV regions located in the west of WJL reached 99%. It is important to plan responding measures of water resource management, to counter the decrease of summer precipitation in western WJL, and reduce the impact of drought and wetlands degradation, which is possibly caused by the global climate change
Altered soil carbon and nitrogen cycles due to the freeze-thaw effect: A meta-analysis
No full textGlobal climate change may result in changes in snow cover, which may enhance freeze-thaw phenomena in mid and high latitude and high elevation ecosystems, especially in the northern hemisphere, in the future. As a common non-biological stress, the freeze-thaw process can substantially alter soil carbon and nitrogen cycles. However, a comprehensive understanding of nutrient pools and dynamics in response to freeze-thaw cycles is not available. Here, we evaluated the effect sizes of the responses of 18 variables related to soil carbon and nitrogen cycles to the freeze-thaw effect from 46 papers. Seventeen studies that reported field observations and 28 studies that reported results from laboratory experiments were included, as well as one paper that used both methods to explore freeze-thaw processes. We used a random-effects model to examine whether soil origins, effect phases (including initial and long-term effects), methods and soil horizons affect the magnitudes of the responses to freeze-thaw events. The soil sources include forest, shrubland, grassland/meadow, cropland, tundra and wetland. We used meta regression to explore possible relationships among effect sizes with freezing temperature, soil pH, soil C/N ratios and other factors. Our results suggest that the freeze-thaw process causes microbial N and the microbial C/N ratio to decrease by 12.2% and 8.5%, respectively. Soil solution dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are enhanced by 27.5% and 373%, respectively. The freeze thaw effect increases the concentrations of NHS4+, NOT and dissolved inorganic nitrogen (DIN) by 84.1%, 29.6% and 35.4%, respectively. N2O emissions are also increased by 95.0% in freeze-thaw treatments. Laboratory measurements resulted in contrasting responses in terms of mineralization, nitrification and respiration. Freeze-thaw events promote turnover of fine roots but have no effect on the long-term aboveground biomass of grassland and heath. The results of this meta-analysis help to achieve a better understanding of the overall effects of freeze-thaw events on soil carbon and nitrogen cycles and their modulation across different environments. (C) 2017 Elsevier Ltd. All rights reserved
Synergetic effect of bio-photocatalytic hybrid system: g-C3N4 and Acinetobacter sp JLS1 for enhanced degradation of C-16 alkane
No full textPetroleum hydrocarbons are ubiquitous in nature and generally lead to contamination. The aim of this study was to establish a bio-photocatalytic system using graphite-like carbon nitride (g-C3N4) and petroleum-degrading bacterium Acinetobacter sp. JLS1 and evaluate its effect on C-16 alkane degradation. The successfully synthesized g-C3N4 produced no obvious lethal effect to strain JLS1 until 1 g/L. C-16 alkane (0.25% v/v) degradation was investigated in the individual (photocatalytic or biocatalytic) and hybrid (bio-photocatalytic) systems. The C16 alkane removal efficiency of the hybrid system under visible light irradiation was 78.2% within 4 h, which was more effective than that of photocatalytic (26.8%) and biocatalytic (38.3%) systems. This positive synergetic effect between g-C3N4 and strain JLS1 was due to the photocatalytic activity of g-C3N4 for C-16 alkane degradation and increased porosity and permeability of bacterial membrane, thus facilitating the entry of targeted compound into bacterial cells. In the hybrid system, hexadecanoic acid, dodecanoic acid and octanoic acid were examined out in bacterial cells, which were biostransformed by strain JLS1 from initial C-16 alkane and its photocatalytic degradation products (alkanes with relative lower C atoms). In addition, alkB gene transcription was strongly upregulated by g-C3N4 under visible-light irradiation, however, growth of strain JLS1 slightly improved compared to that in other tested systems, suggesting that continuous attack of photocatalytic reaction constantly impeded the repair process of bacterial cell. The established effective bio-photocatalytic system not only drew a new sight for further research but also provided a promising remediation approach for dealing with petroleum hydrocarbons. (C) 2017 Elsevier B.V. All rights reserved
