Cadaver decomposition in terrestrial ecosystems

A dead mammal (i.e. cadaver) is a high quality resource (narrow carbon:nitrogen ratio, high water content) that releases an intense, localised pulse of carbon and nutrients into the soil upon decomposition. Despite the fact that as much as 5,000 kg of cadaver can be introduced to a square kilometre of terrestrial ecosystem each year, cadaver decomposition remains a neglected microsere. Here we review the processes associated with the introduction of cadaver-derived carbon and nutrients into soil from forensic and ecological settings to show that cadaver decomposition can have a greater, albeit localised, effect on belowground ecology than plant and faecal resources. Cadaveric materials are rapidly introduced to belowground floral and faunal communities, which results in the formation of a highly concentrated island of fertility, or cadaver decomposition island (CDI). CDIs are associated with increased soil microbial biomass, microbial activity (C mineralisation) and nematode abundance. Each CDI is an ephemeral natural disturbance that, in addition to releasing energy and nutrients to the wider ecosystem, acts as a hub by receiving these materials in the form of dead insects, exuvia and puparia, faecal matter (from scavengers, grazers and predators) and feathers (from avian scavengers and predators). As such, CDIs contribute to landscape heterogeneity. Furthermore, CDIs are a specialised habitat for a number of flies, beetles and pioneer vegetation, which enhances biodiversity in terrestrial ecosystems.     

Soil physi-chemical properties,biomass and nutrient contents of forest litter in mixed plantations of Eucalyptus grandis and three tree species北大核心CSCD

In the present study, we compared the soil physical and chemical properties, biomass of forest litter and nutrient contents in three-and-half-year plantations of E. grandis mixed with Toona ciliate, Alnus formosana, Sassafras tzumu. The results indicated that mixing T. ciliate and A. formosana with E. grandis mitigated soil acidification. In E. grandis × S. tzumu plantations, the soil bulk density decreased, but the moisture capacity and porosity increased. The mixed plantations of E. grandis × S. tzumu significantly increased the soil total C, N, P and K content, by 64.7%, 41.9%, 28.6% and 7.7%, respectively. The mixed plantations of E. grandis × A. formosana also significantly increased the soil total C, N and P content, by 15.2%, 27.9% and 47.6%, respectively. Compared with the pure plantations, the mixed plantations had significantly lower soil hydrolysis N and higher available P content. Only the E. grandis × A. formosana plantations had higher soil available K content. Compared with that in pure plantations, the biomass of branch litter and leaf litter was significantly higher in E. grandis × A. formosana plantations but significantly lower in E. grandis × A. formosana and E. grandis × A. formosana plantations; the biomass of leaf litter and total biomass of litter of E. grandis × S. tzumu were 9.8% and 9.3% respectively lower. The litter C content in three kinds of mixed forest was significantly lower and the litter N content was significantly higher than that in the pure plantations. Only the mixed plantations of E. grandis × A. formosana plantations would increase the content of litter P. The mixed plantations of E. grandis × S. tzumu would increase the content of litter K. In general, S. tzumu is the optimal tree species to mix with E. grandis, followed by A. formosana, but T. ciliate is unsuitble for mixed plantation with E. grandis.     

Development of database of real-world diesel vehicle emission factors for China

A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China,NO_x emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT (Computer Programmer to calculate Emissions from Road Transport) and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5 (Highway Vehicle Particulate Emission Modeling Software) models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent, which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-basedmodels will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.     

Microalgae cultivation and culture medium recycling by a two-stage cultivation system

Nutrients and water play an important role in microalgae cultivation. Using wastewater as a culture medium is a promising alternative to recycle nutrients and water, and for further developing microalgae-based products. In the present study, two species of microalgae, Chlorella sp. (high ammonia nitrogen tolerance) and Spirulina platensis (S. platensis, high growth rate), were cultured by using poultry wastewater through a two-stage cultivation system for algal biomass production. Ultrafiltration (UF) or centrifuge was used to harvest Chlorella sp. from the first cultivation stage and to recycle culture medium for S. platensis growth in the second cultivation stage. Results showed the two-stage cultivation system produced high microalgae biomass including 0.39 g·L^–1Chlorella sp. and 3.45 g·L^–1S. platensis in the first-stage and second-stage, respectively. In addition, the removal efficiencies of NH₄⁺ reached 19% and almost 100% in the first and the second stage, respectively. Total phosphorus (TP) removal reached 17% and 83%, and total organic carbon (TOC) removal reached 55% and 72% in the first and the second stage, respectively. UF and centrifuge can recycle 96.8% and 100% water, respectively. This study provides a new method for the combined of pure microalgae cultivation and wastewater treatment with culture medium recycling.

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Modification of uncertainty analysis in adapted material flow analysis: Case study of nitrogen flows in the Day-Nhue River Basin,Vietnam

Nitrogen flows impacted by human activities in the Day-Nhue River Basin in northern Vietnam have been modeled using adapted material flow analysis (MFA). This study introduces a modified uncertainty analysis procedure and its importance in MFA. We generated a probability distribution using a Monte Carlo simulation, calculated the nitrogen budget for each process and then evaluated the plausibility under three different criterion sets. The third criterion, with one standard deviation of the budget value as the confidence interval and 68% as the confidence level, could be applied to effectively identify hidden uncertainties in the MFA system. Sensitivity analysis was conducted for revising parameters, followed by the reassessment of the model structure by revising equations or flow regime, if necessary. The number of processes that passed the plausibility test increased from five to nine after reassessment of model uncertainty with a greater model quality. The application of the uncertainty analysis approach to this case study revealed that the reassessment of equations in the aquaculture process largely changed the results for nitrogen flows to environments. The significant differences were identified as increased nitrogen load to the atmosphere and to soil/groundwater (17% and 41%, respectively), and a 58% decrease in nitrogen load to surface water. Thus, modified uncertainty analysis was considered to be an important screening system for ensuring quality of MFA modeling.