Effect and Mechanism of Armillaria mellea 07-22 Fermentation on the Degradation of Zearalenone

This study used Armillaria mellea 07-22 as the experimental strain to degrade zearalenone (ZEN) by fungal biological fermentation. The degradation effects of Armillaria mellea on ZEN were studied, including the degradation effects of different concentrations of ZEN by the strain and the effects of different culture time, culture temperature, initial pH value and inoculation amount on the degradation of ZEN by the strain. Then the degradation mechanism was explored, the degradation effects of mycelium, fermentation supernatant and cell contents on ZEN were analyzed, and the effects of different fermentation time, pH values, and metal ions on degradation of ZEN by fermentation supernatant were studied, and the correlation between degradation effect and laccase production activity of the strain was illustrated. The results showed that Armillaria mellea 07-22 had a good degradation effect on ZEN. When the ZEN concentration was 5 μg/mL, the optimal degradation conditions were culture time of 8 days, culture temperature of 27 ℃, initial pH of 7.0, and inoculation amount of 10%. At this time, the degradation rate of ZEN was 78.72%. The degradation rates of ZEN by mycelium, fermentation supernatant and cell contents were 47.42%, 37.05% and 13.08% respectively. The extracellular enzymes secreted by Am-07-22 were the main way to degrade ZEN, and the mycelium cells also had a certain adsorption effect on ZEN. In addition, the correlation between the degradation rate of ZEN by fermentation supernatant and laccase activity was 0.973, and Cu2+ had the best promoting effect on the degradation of ZEN by fermentation supernatant

Distribution and mineralization of organic carbon and nitrogen in forest soils of the southern Tibetan Plateau

The forests of the Tibetan Plateau store large amounts of soil organic carbon (OC) but are among the most vulnerable and sensitive ecosystems to environmental change. The lack of knowledge regarding the distribution and turnover of OC and nitrogen (N) in Tibetan Plateau forest soils limits the ability to predict how this ecosystem will respond to climate change. In this study, we collected mineral soils from coniferous and broadleaf forests on the southern Tibetan Plateau and measured' OC and N contents in both bulk soils and water-stable aggregates. We also determined the mineralization of OC and N in bulk soils and examined the effects of N addition on OC mineralization. Our objectives were to investigate the distribution and mineralization of soil OC and N in various forest types and to determine the stability of OC following N addition. Our results showed that OC and N in macroaggregates contributed 76% of the OC and N in bulk soils. Forest type did not affect the OC or N contents of either bulk soils or aggregates. Similarly, OC and N mineralization and their relationships with soil OC or N contents were similar between broadleaf and coniferous forests, indicating that soil OC and N distribution and turnover were insensitive to forest type. Nitrogen mineralization was dominated by ammonification in these forest soils. Nitrogen addition did not affect OC mineralization or its relationship with soil OC or N contents. These results indicate that the OC contents of forest soils of the southern Tibetan Plateau are relatively insensitive to N addition

Landslides on the Loess Plateau of China: a latest statistics together with a close look

Landslide plays an important role in landscape evolution, delivers huge amounts of sediment to rivers and seriously affects the structure and function of ecosystems and society. Here, a statistical analysis together with a field investigation was carried out on the Loess Plateau of China to address the challenges. The study tracks landslide-related deaths and collects knowledge about this natural hazard. Since the 1980s, 53 fatal landslides have occurred, causing 717 deaths. As the most important trigger, rainfall induced 40% of the catastrophic landslides, while other factors, i.e., human activities, freeze-thaw and earthquake, accounted for 36, 23 and 1%, respectively. Furthermore, landslide frequency and death toll related to human activities were increasing as time went on. Landslide also plays an important role in sediment delivery, especially in areas with steep terrain. Sediment discharge from landslides accounts for a considerable proportion of the total soil loss in the upper and middle reaches of the Yellow River. In some catchments of the Loess Plateau, landslides contributed over 50% of the total sediment discharge. The result shows that landslide is a widespread geologic hazard in the rural area of the Loess Plateau, China

Climate-driven increase of natural wetland methane emissions offset by human-induced wetland reduction in China over the past three decades

Both anthropogenic activities and climate change can affect the biogeochemical processes of natural wetland methanogenesis. Quantifying possible impacts of changing climate and wetland area on wetland methane (CH4) emissions in China is important for improving our knowledge on CH4 budgets locally and globally. However, their respective and combined effects are uncertain. We incorporated changes in wetland area derived from remote sensing into a dynamic CH4 model to quantify the human and climate change induced contributions to natural wetland CH4 emissions in China over the past three decades. Here we found that human-induced wetland loss contributed 34.3% to the CH4 emissions reduction (0.92 TgCH(4)), and climate change contributed 20.4% to the CH4 emissions increase (0.31 TgCH(4)), suggesting that decreasing CH4 emissions due to human-induced wetland reductions has offset the increasing climate-driven CH4 emissions. With climate change only, temperature was a dominant controlling factor for wetland CH4 emissions in the northeast (high latitude) and Qinghai-Tibet Plateau (high altitude) regions, whereas precipitation had a considerable influence in relative arid north China. The inevitable uncertainties caused by the asynchronous for different regions or periods due to interannual or seasonal variations among remote sensing images should be considered in the wetland CH4 emissions estimation

Interannual variation in methane emissions from tropical wetlands triggered by repeated El Nino Southern Oscillation

Methane (CH4) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Nino-Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Nino events are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the ENSO on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Nino periods and with positive anomalies occurring during La Nina periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Nino events contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global warming