Integrated eco-strategies towards sustainable carbon and nitrogen cycling in agriculture.

To meet the ever-growing human demands for food, fuel, and fiber, agricultural activities have dramatically altered the global carbon (C) and nitrogen (N) cycles. These biogeochemical cycles along with water, phosphorus, and sulfur cycles are fundamental features of life on Earth. Human alteration of the global N cycle has had both positive and negative outcomes. To efficiently feed a growing population, crop-livestock production systems have been developed, however, these systems also contribute significantly to environmental pollution and global climate change. Management of agricultural waste (AW) and the application of N fertilizers are central to the issues of greenhouse gas (GHG) emissions and nutrient runoff that contributes to the eutrophication of water bodies. If managed properly, AW can provide nutrients for plants and contribute to the conservation of soil health. In order to achieve the long-term conservation of agricultural production systems, it is important to promote the proper recycling of AW in agroecosystems and to minimize the reliance on chemical N fertilizers. Composting is one of the sustainable and effective approaches for recycling AW in agriculture. However, the conventional composting process is dilatory and produces compost with low N content compared to chemical N fertilizers. For this reason, comprehensive research is required to improve the composting process and the N content of the soil organic amendments. This work aims to explore the beneficial effects of the integrated application of biochar and specific C and N cycling microorganisms to the composting process and the quality of the composted products. In pursuit of replacing chemical N fertilizers with bio/organic fertilizers, we further discussed the power of the combined application of compost, biochar, and N-fixing bacteria in agricultural production systems. The knowledge of smart integration of AW and microorganisms in agriculture could solve the main agricultural and environmental problems associated with human-induced flows of C and N. Building upon the knowledge disseminated in review to further extensive research will pave the way for better management of agricultural production systems and sustainable C and N cycling in agriculture.

Interaction effects of the main drivers of global climate change on spatiotemporal dynamics of high altitude ecosystem behaviors: process-based modeling.

Soil organic carbon and nitrogen (SOC-N) dynamics are indicative of the human-induced disturbances of the terrestrial ecosystems the quantification of which provides insights into interactions among drivers, pressures, states, impacts, and responses in a changing environment. In this study, a process-based model was developed to simulate the eight monthly outputs of net primary productivity (NPP), SOC-N pools, soil C:N ratio, soil respiration, total N emission, and sediment C-N transport effluxes for cropland, grassland, and forest on a hectare basis. The interaction effect of the climate change drivers of aridity, CO2 fertilization, land-use and land-cover change, and best management practices was simulated on high altitude ecosystems from 2018 to 2070. The best management practices were developed into a spatiotemporally composite index based on SOC-N stock saturation, 4/1000 initiative, and RUCLE-C factor. Our model predictions differed from the remotely sensed data in the range of - 64% (underestimation) for the cropland NPP to 142% (overestimation) for the grassland SOC pool as well as from the global mean values in the range of - 97% for the sediment C and N effluxes to 60% for the total N emission from the grassland. The interaction exerted the greatest negative impact on the monthly sediment N efflux, total N emission, and soil respiration from forest by - 90.5, - 82.7, and - 80.3% and the greatest positive impact on the monthly sediment C effluxes from cropland, grassland, and forest by 139.3, 137.1, and 133.3%, respectively, relative to the currently prevailing conditions.

New insights on municipal solid waste (MSW) landfill plastisphere structure and function.

Plastisphere plays crucial role in global carbon and nitrogen cycles and microplastics formation. Global Municipal Solid Waste (MSW) landfills contain 42 % plastic waste, therefore representing one of the most significant plastispheres. MSW landfills are also the third largest anthropogenic methane sources and the important anthropogenic N2O source. Surprisingly, knowledge of microbiota and the associated microbial carbon and nitrogen cycles of landfill plastispheres is very limited. In this study, we characterized and compared the organic chemicals profile, bacterial community structure and metabolic pathway on plastisphere and the surrounding refuse in a large-scale landfill using GC/MS and 16S rRNA genes high-throughput sequencing, respectively. Landfill plastisphere and the surrounding refuse differed in organic chemicals composition. However, abundant phthalate-like chemicals were determined in both environments, implying the plastics additives leaching. Bacterial colonizing on the plastics surface had significantly higher richness than that in the surrounding refuse. Plastic surface and the surrounding refuse had distinct bacterial community composition. Genera of Sporosarcina, Oceanobacillus and Pelagibacterium were detected on the plastic surface with high abundance, while Ignatzschineria, Paenalcaligenes and Oblitimonas were rich in the surrounding refuse. Typical plastics biodegradation genus Bacillus, Pseudomonas and Paenibacillus were detected in both environments. However, Pseudomonas was dominant in plastic surface (up to 88.73 %), whereas Bacillus was rich in the surrounding refuse (up to 45.19 %). For the carbon and nitrogen cycle, plastisphere was predicted to had significant (P < 0.05) higher functional genes involved in carbon metabolism and nitrification, indicating more activated carbon and nitrogen microbial activity on the plastics surface. Additionally, pH was the main driver in shaping the bacterial community composition on plastic surface. These results indicate that landfill plastispheres serve as unique niches for microbial community habitation and function on microbial carbon and nitrogen cycles. These observations invite further study of the landfill plastispheres ecological effect.

[Application of stable isotope techniques in soil food web research]. / ç¨³å®šåŒä½ç´ æŠ€æœ¯åœ¨åœŸå£¤é£Ÿç‰©ç½‘ç ”ç©¶ä¸­çš„åº”ç”¨.

Stable isotope technique is important for understanding the structure and function of soil food web, which is considered as a belowground black box. We reviewed typical application cases of stable isotope techniques in the research of soil food webs, including to determine food sources and feeding preferences of soil fauna by using isotopes, and to analyze the trophic structure of soil food webs through isotope fractionation effects during the process of feeding and nutrient sequestration by soil fauna. Additionally, stable isotope techniques could reveal the role of soil biota at different trophic levels within soil food web in ecosystem matter and energy flow, which favored to carry out accurate and efficient research on the contribution of soil food webs to soil carbon and nitrogen cycling process and the corresponding influence mechanism. We further put forward the limitations of current stable isotope techniques and the future development directions.

Nutrient pollution enhances productivity and framework dissolution in algae- but not in coral-dominated reef communities.

Ecosystem services provided by coral reefs may be susceptible to the combined effects of benthic species shifts and anthropogenic nutrient pollution, but related field studies are scarce. We thus investigated in situ how dissolved inorganic nutrient enrichment, maintained for two months, affected community-wide biogeochemical functions of intact coral- and degraded algae-dominated reef patches in the central Red Sea. Results from benthic chamber incubations revealed 87% increased gross productivity and a shift from net calcification to dissolution in algae-dominated communities after nutrient enrichment, but the same processes were unaffected by nutrients in neighboring coral communities. Both community types changed from net dissolved organic nitrogen sinks to sources, but the increase in net release was 56% higher in algae-dominated communities. Nutrient pollution may, thus, amplify the effects of community shifts on key ecosystem services of coral reefs, possibly leading to a loss of structurally complex habitats with carbonate dissolution and altered nutrient recycling.