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22921. 题目: Soil texture strongly controls exogenous organic matter mineralization indirectly via moisture upon progressive drying — Evidence from incubation experiments Soil texture is well known to directly affect bioavailability of organic matter to heterotrophs, but it also steers their activity by moderating soil moisture fluctuation. Disentangling these direct and indirect textural controls is, however, not trivial and attempts to do so are very scarce. Most attention has just gone to the stimulation of soil carbon (C) mineralization by soil moisture fluctuation per se. To quantify the indirect moisture-mediation control of soil texture on C mineralization, we monitored maize straw degradation in various soil texture/moisture regime combinations. Moisture levels were firstly kept fixed at 32% WFPS (experiment Fixed32) in a sand, sandy loam and silt loam soil or allowed to fluctuate between 20% and 50% water-filled pore space (WFPS, Dry-wet20-50). Total maize-C (Cmaize) mineralized was highly similar between these three textures and thus the direct textural control was minor. On the contrary with the fluctuating moisture level, around threefold more added Cmaize was mineralized (P < 0.01) in the sand (86%) than in the silt loam (25%) soil. We owe this boost in Cmaize mineralization to the rewetting of larger pores in the sandy soil which should contain most of the ground maize residue. This determining control of texture on distribution of moisture as well as the maize substrate clearly exceeded the direct impact of texture on organic matter stability. In a third and fourth experiment, timing and dose to remoisten a silt loam soil back to 50% (experiment Equal20-50) or 35% WFPS (experiment Equal20-35) when dried out to 20% WFPS were additionally mimicked in the sand and sandy loam soils. These scenarios correspond more closely to a field situation in which nearby differently textured soils all receive the same precipitation input. After several rewetting cycles, the silt loam soil eventually had a 13.9% higher WFPS than the sandy soils. By then moisture stress clearly limited Cmaize mineralization in the sandy soil (0.13 (Equal20-50) and 0.05 (Equal20-35) mg kg−1 h−1) as it proceeded at only half of the rate as in the silt loam soil (0.21 (Equal20-50) and 0.12 (Equal20-35) mg kg−1 h−1). The amount of Cmaize mineralized after 120 days in the silt loam soil was simulated to surpass that in the sandy soil. We conclude that the effect of soil texture on decomposition of a fresh substrate is largely indirect, i.e. through mediation of soil water content and its distribution in the soil matrix. Moreover, our data suggests that in the event of prolonged drought Cmaize mineralization will be less limited in finer textured soil, contradicting the widespread idea that organic matter would degrade more rapidly in coarser textured soils. | |||||
22922. 题目: Protists and collembolans alter microbial community composition, C dynamics and soil aggregation in simplified consumer–prey systems | |||||
22923. 题目: Improved Understanding of Dissolved Organic Matter Processing in Freshwater Using Complementary Experimental and Machine Learning Approaches | |||||
22924. 题目: From pools to flow: The PROMISE framework for new insights on soil carbon cycling in a changing world Soils represent the largest terrestrial reservoir of organic carbon, and the balance between soil organic carbon (SOC) formation and loss will drive powerful carbon‐climate feedbacks over the coming century. To date, efforts to predict SOC dynamics have rested on pool‐based models, which assume classes of SOC with internally homogenous physicochemical properties. However, emerging evidence suggests that soil carbon turnover is not dominantly controlled by the chemistry of carbon inputs, but rather by restrictions on microbial access to organic matter in the spatially heterogeneous soil environment. The dynamic processes that control the physicochemical protection of carbon translate poorly to pool‐based SOC models; as a result, we are challenged to mechanistically predict how environmental change will impact movement of carbon between soils and the atmosphere. Here, we propose a novel conceptual framework to explore controls on belowground carbon cycling: Probabilistic Representation of Organic Matter Interactions within the Soil Environment (PROMISE). In contrast to traditional model frameworks, PROMISE does not attempt to define carbon pools united by common thermodynamic or functional attributes. Rather, the PROMISE concept considers how SOC cycling rates are governed by the stochastic processes that influence the proximity between microbial decomposers and organic matter, with emphasis on their physical location in the soil matrix. We illustrate the applications of this framework with a new biogeochemical simulation model that traces the fate of individual carbon atoms as they interact with their environment, undergoing biochemical transformations and moving through the soil pore space. We also discuss how the PROMISE framework reshapes dialogue around issues related to SOC management in a changing world. We intend the PROMISE framework to spur the development of new hypotheses, analytical tools, and model structures across disciplines that will illuminate mechanistic controls on the flow of carbon between plant, soil, and atmospheric pools. | |||||
22925. 题目: Biochar addition rate determines contrasting shifts in soil nematode trophic groups in outdoor mesocosms: An appraisal of underlying mechanisms The medium-term impact of the application of a pine gasification biochar at low and high rates (5 and 30 tons ha−1) on nematode communities was assessed in outdoor mesocosms cropped to barley during the spring and the fall of the third agronomical year following the application. Impacts were measured as shifts in community taxon and functional composition, and ecological indices were related to soil physicochemical and microbiological properties. Biochar addition did not affect soil properties, total nematode abundance, richness or biomass, but different community shifts were observed in the two biochar addition treatments (5 and 30 tons ha−1) when compared with controls (with no biochar added). Communities shifted both taxonomically and functionally: the low application rate promoted predator and plant-parasitic nematodes, while the high application rate favored bacterivores and fungivores. An appraisal of the plausible main mechanisms behind those shifts was carried out, based on the various mechanisms proposed in the available literature about shifts in nematode communities after organic amendments, as well as the scarce biochar studies published to date. This study suggests that biochar additions show a capacity for regulating plant-parasitic nematodes in agroecosystems, but also that this regulation is dependent on the addition rate. There is a need to validate this work with further studies to identify the mechanisms behind this suppression and determine the necessary rates of biochar addition to mitigate unintended effects. | |||||
22926. 题目: Effects of mercury, organic carbon, and microbial inhibition on methylmercury cycling at the profundal sediment-water interface of a sulfate-rich hypereutrophic reservoir Methylmercury (MeHg) produced by anaerobic bacteria in lakes and reservoirs, poses a threat to ecosystem and human health due to its ability to bioaccumulate in aquatic food webs. This study used 48-hour microcosm incubations of profundal sediment and bottom water from a sulfate-rich, hypereutrophic reservoir to assess seasonal patterns of MeHg cycling under various treatments. Treatments included addition of air, Hg(II), organic carbon, and microbial inhibitors. Both aeration and sodium molybdate, a sulfate-reducing bacteria (SRB) inhibitor, generally decreased MeHg concentration in microcosm water, likely by inhibiting SRB activity. The methanogenic inhibitor bromoethanesulfonate increased MeHg concentration 2- to 4- fold, suggesting that methanogens were potent demethylators. Pyruvate increased MeHg concentration under moderately reduced conditions, likely by stimulating SRB, but decreased it under highly reduced conditions, likely by stimulating methanogens. Acetate increased MeHg concentration, likely due to the stimulation of acetotrophic SRB. Results suggest that iron-reducing bacteria (IRB) were not especially prominent methylators and MeHg production at the sediment-water interface is elevated under moderately reduced conditions corresponding with SRB activity. In contrast, it is suppressed under oxic conditions due to low SRB activity, and under highly reduced conditions (>-100 mV) due to enhanced demethylation by methanogens. | |||||
22927. 题目: Linking microbial community structure with molecular composition of dissolved organic matter during an industrial-scale composting This study explored the interactions between dissolved organic matter (DOM) composition and microbial community structure during an industrial-scale composting by Fourier transform ion cyclotron resonance mass spectrometry and 16S rRNA sequencing analysis. The results revealed that DOM from matured compost contained primarily lignins/carboxylic-rich alicyclic molecules (73.6%), the higher double bond equivalent (5.97) and aromaticity index (0.18), indicating that the molecular composition of DOM had changed substantially. Drastic changes in microbial community structure were also observed along with the DOM transformation process of composting. Network analysis further indicated that Caldicoprobacter, Bacillus, and Dechloromonas were associated with the most DOM subcategories. Caldicoprobacter could degrade carbohydrates, Bacillus accelerated the humification by transforming N-containing compounds, and Dechloromonas could degrade polycyclic aromatic hydrocarbons distributed in low O/C. These findings are helpful for understanding the molecular mechanisms of DOM transformation and humification of sludge composting. | |||||
22928. 题目: The addition of organic carbon and nitrogen accelerates the restoration of soil system of degraded alpine grassland in Qinghai-Tibet Plateau Soil degradation is often accompanied with the decrease of soil organic matter and soil fertility, and the direct addition of organic carbon and nitrogen could be the good method to accelerate the restoration of soil system of degraded grassland. The effects of the addition of biochar and nitrogen on soil properties and microorganisms in the 0-20 cm soil depth of degraded alpine grassland were evaluated. The treatments consisted of three different levels of biochar (1 kg m−2, 2 kg m−2, and 4 kg m−2) and nitrogen (5 g m−2, 10 g m−2, 15 g m−2). The addition of biochar and nitrogen increased soil organic carbon, total nitrogen, available phosphorus, water content (SWC), urease, phosphatase,and microbial biomass. The relative content of arbuscular mycorrhizal fungi, 18:1w9c fungi, actinomycetes, gram-negative and gram-positive bacteria increased, however, 18:2w6,9c fungi, anaerobic bacteria and methanotrophic bacteria decreased. Under the effect of biochar and nitrogen addition, most of soil physicochemical properties showed significant correlation in the 0-20 cm soil layer. The correlation between microbial community and soil properties mainly occurred in the 0–10 cm soil layer. The community of fungi, actinomycetes, gram-negative and Gram-positive bacteria showed significant relationship with soil urease, phosphatase, and available phosphorus (P < 0.01, r > 0.30). Arbuscular mycorrhizal fungi showed strong positive correlation with pH, NH4+, and SWC. These results indicated that the addition of biochar and nitrogen quickly improved soil nutrient and microbial community of degraded alpine grassland and could be used for the remediation of degraded alpine grassland. | |||||
22929. 题目: Mine spoil remediation via biochar addition to immobilise potentially toxic elements and promote plant growth for phytostabilisation There are thousands of disused and abandoned mining sites around the world with substantial accumulations of exposed mine spoil materials that pose a direct threat to their surrounding environment. Management of such sites, and neutralisation of the environmental threats they pose, is therefore extremely important and is an issue of global significance. Low cost management and remediation strategies need to be developed because many abandoned mine sites are in remote and/or economically challenged areas. One promising option is the incorporation of biochar into spoil materials, which has the potential to immobilise leachable toxic constituents and facilitate revegetation and thereby stabilisation of spoil heaps. This study investigated the capacity of readily available biochar materials made from wheat and rice waste products to immobilise and retain key metallic contaminants Pb and Zn from solution, and also investigated the utility of biochar application for remediating mine spoil heaps from different mine types in terms of facilitating establishment of vegetation coverage and minimising porewater element mobility within spoil heaps. The results demonstrated the high sorption capacity of the biochars (typically >97% of Pb or Zn in solution) and their ability to retain the metals despite an active desorption procedure (>93% of sorbed Pb retained and >75% of sorbed Zn). The remediation trial revealed that biochar application increased plant yield and decreased plant assimilation of many potentially toxic elements and also decreased spoil porewater concentrations of Al, Cd, Pb and Zn in most cases. In some spoil types investigated biochar addition also significantly decreased porewater concentrations of As (e.g. from ~30 mg/L to ~5 mg/L), demonstrating its potential utility for low cost environmental remediation across a range of mine spoil types. | |||||
22930. 题目: Incorporating soil aggregate-associated indicators into evaluating ecological responses of degraded estuarine wetlands to freshwater replenishment at different intensity: A case study from the Yellow River Delta, China Management intensity was considered an important factor in evaluating and regulating the anthropogenic restoration measures for a degraded ecosystem. By comparing selected conventional soil physicochemical, microbial and incorporating aggregate-associated indices between wetland plot with high-intensity freshwater replenishment (HI wetlands) and wetland plot with low-intensity freshwater replenishment (LI wetlands), edaphic responses of degraded estuarine wetlands to freshwater replenishment at different intensity were assessed in the present study. The results showed that high-intensity freshwater replenishment exerted better soil salinization and alkalization alleviation effects on degraded estuarine wetlands, which caused lower EC and pH values in HI wetlands than those in LI wetlands. And soil microbial biomass was promoted, with freshwater replenishment intensity increased, as indicated by MBC and total PLFAs. Minor alternation of soil microbial community composition was observed with an elevated abundance of arbuscular mycorrhizal fungi (AMF) in HI wetlands. On the other hand, freshwater replenishment at low intensity was found to contribute to organic matter accumulation, as indicated by both higher SOC concentrations and carbon stocks in LI wetlands than those in HI wetlands. And soil aggregate-associated indicators provided more scientific clues that freshwater replenishment at low intensity favored the formation of large macroaggregates, and thus supported higher soil aggregate stability. Moreover, a transfer of allocations of aggregate-associated carbon and nitrogen stocks from microaggregates to large macroaggregates was induced as the freshwater replenishment intensity decreased, and the principle governing factors were the proportion of large macroaggregates in soils, soil salinity and microbial decomposition rates based on multivariate statistical analysis. The findings of this study could provide basic data regarding soil physicochemical properties, microbial characteristics and soil structure stability in restored wetlands of the Yellow River Delta with freshwater replenishment at different intensity and guiding adaptive management strategies of freshwater replenishment to enhance the ecological functions of estuarine wetlands. | |||||
22931. 题目: Remobilization of dormant carbon from Siberian-Arctic permafrost during three past warming events | |||||
22932. 题目: Intraseasonal variation of phycocyanin concentrations and environmental covariates in two agricultural irrigation ponds in Maryland, USA | |||||
22933. 题目: Lime and/or Phosphate Application Affects the Stability of Soil Organic Carbon: Evidence from Changes in Quantity and Chemistry of the Soil Water-Extractable Organic Matter | |||||
22934. 题目: Changes in soil carbon and nitrogen stocks following degradation of alpine grasslands on the Qinghai‐Tibetan Plateau: A meta‐analysis | |||||
22935. 题目: The influence of long-term Zn and Cu contamination in Spolic Technosols on water-soluble organic matter and soil biological activity Potentially toxic elements (PTE) pollution has a pronounced negative effect on the soil and its components. The characteristics of soil organic matter and the activity of soil enzymes can serve as sensitive indicators of the degree of changes occurring in the soil. This study aims to assess the effect of long-term severe soil contamination with Zn and Cu on water-soluble organic matter (WSOM) and the associated changes in the biochemical activity of microorganisms. The total content of Zn and Cu in the studied soils varies greatly: Zn from 118 to 65,311 mg/kg, Cu from 52 to 437 mg/kg. The content of WSOM was determined using cold and hot extraction. It was revealed that the WSOM, extracted with cold water is a sensitive indicator reflecting the nature of the interaction of Zn and Cu with it. With an increase in the Cu and Zn content, the amount of WSOM extracted with cold water increases due to rise in the complex-bound metal compounds associated with it. The content of complex-bound compounds Zn in Spolic Technosols reaches 50% of the total metal content. It is shown that one of the biogeochemical mechanisms of microorganisms' adaptation to metal contamination is clearly manifested by the increase in the content of WSOM. The precipitation of metal carbonates develops in the soil which reduces the mobility and toxicity of PTE. Due to this mechanism, a decrease in the activity of dehydrogenases and urease was not prominent in all studied soils, despite the very high level of pollution and the transformation of organic matter. The study of the relationship of PTE with the most easily transformed part of WSOM and the activity of soil enzymes is of great importance for an objective assessment of possible environmental risks. | |||||
22936. 题目: Long-term grazing exclusion greatly improve carbon and nitrogen store in an alpine meadow on the northern Qinghai-Tibet Plateau Grazing management is known to be one of the most important strategies for regulating plant community structure and soil carbon and nitrogen content for alpine meadows, but very few studies about the effect of long-term grazing management on soil and plant characteristics. In this study, biomass and soil samples were collected during the grazing and grazing-exclusion periods to determine the biomass and soil properties, two-way ANOVA was used to examine the effects of grazing management on plant and soil properties. Our results show that the aboveground biomass was reduced during the grazing period but increased during the grazing exclusion period. Furthermore, the response of plant functional groups to grazing management was different. Whereas the belowground biomass increased during the grazing period but decreased during the grazing-exclusion period. Interestingly, the 0–10 cm and 30–40 cm soil organic carbon (SOC) increased significantly during grazing and grazing exclusion period, respectively. The 0–30 cm total nitrogen (TN) and 0–40 cm available nitrogen (AN) increased significantly during the grazing-exclusion period but showed no significant change during the grazing period. The 0–40 cm SOC and TN were both significantly affected by the year, with grazing management exerting only a marginal effect on SOC. 0–40 cm AN was significantly affected by grazing management and the interaction between year and grazing management. Our results suggest that long-term grazing exclusions could greatly improve both above vegetation biomass and soil condition such as soil carbon and nitrogen content. | |||||
22937. 题目: Simultaneous harvesting and extracellular polymeric substances extrusion of microalgae using surfactant: Promoting surfactant-assisted flocculation through pH adjustment In this research, the use of four different types of surfactants on biomass harvesting and extracellular polymeric substances (EPS) extrusion of Chlorella sorokiniana sp was investigated The synergy between cationic surfactants and pH was tested to improve flocculation efficiency through the combined mechanism of charge neutralization, bridging and sweeping. Zeta potential and microscopic images were used to gain mechanistic understanding. The harvesting efficacy correlated positively with the biomass zeta potential and the surfactants alkyl-chain length; i.e., CTAB (88%) > DTAB (66%) > triton X-100 (41%) > SDS (11%). When the pH increased from 8 to 12, the harvesting efficiency was improved 12% and 39% for CTAB and DTAB, respectively. More interestingly, pH adjustment dramatically reduced the optimal dosages of CTAB and DTAB from 400 to 50 and 1000 to 300 mg/L, respectively. All selected surfactants could successfully release high value components of EPS such as protein and polysaccharide. | |||||
22938. 题目: Preservation of Organic Carbon in Dolomitized Cambrian Stromatolites and Implications for Microbial Biosignatures in Diagenetically Replaced Carbonate Rock Stromatolites have been a major focus in the search for ancient microbial life, however, the organic carbon biosignatures of dolomitized stromatolites have not yet been fully characterized or correlated with their dolomitizing conditions. Although dolomitization rarely preserves microbial morphology, the presence of organic carbon can provide valuable information for characterization of fossils' biogenicity, syngenicity, and indigeneity to their host rock. The Cambrian Allentown Formation in New Jersey, USA, is an excellent example of dolomitized stromatolites and thrombolites containing diagenetically modified microbial biosignatures. Based on XRD and EPMA data, the dolomite composition is typically stoichiometric, with varying degrees of cationic ordering. The outcrop underwent early dolomitization in a marginal-marine setting and later burial diagenesis resulting in multi-generational dolomite formation: (1) microspar dolomite formed by early diagenetic replacement at or near the surface, (2) zoned dolomite formed penecontemporaneously with the microspar phase as rhombohedral crystals by infilling primary pore spaces within the microspar matrix. The rhombic crystals continued to grow outward in alternating stages of Fe-enriched and -depleted fluids, which were preserved in zoned rims and revealed by cathodoluminescence, and (3) saddle dolomite formed during late stage deep burial with Fe- and Mn-rich fluids, and occurs as a void-filling, high-temperature phase. Organic carbon, characterized using confocal Raman microscopy, has an exclusive distribution within the microspar dolomite, and the D and G bands' characteristics reveal similar thermal alteration to the host rock, indicating that the mapped organic carbon is indigenous and syngenetic with the Cambrian carbonates. The findings presented in this study reveal organic matter found within microspar of various dolomitized facies deriving from different source pools of organic carbon. This study sheds light on biosignatures in secondary dolostones and may aid biosignature detection in older carbonate rocks on Earth and Mars. | |||||
22939. 题目: Origin and fate of dissolved organic matter in four shallow Baltic Sea estuaries | |||||
22940. 题目: Organic carbon export and loss rates in the Red Sea The export and fate of organic carbon in the mesopelagic zone are still poorly understood and quantified due to lack of observations. We exploited data from a BGC‐Argo float that was deployed in the Red Sea to study how a warm and hypoxic environment can affect the fate of the organic carbon in the ocean's interior. We observed that only 10% of the particulate organic carbon (POC) exported survived at depth due to remineralization processes in the upper mesopelagic zone. We also found that POC exported was rapidly degraded in a first stage and slowly in a second one, which may be dependent on the palatability of the organic matter. We observed that AOU‐based loss rates (a proxy of the remineralization of total organic matter) were significantly higher than the POC‐based loss rates, likely because changes in AOU are mainly attributed to changes in dissolved organic carbon. Finally, we showed that POC‐ and AOU‐based loss rates could be expressed as a function of temperature and oxygen concentration. These findings advance our understanding of the biological carbon pump and mesopelagic ecosystem. | |||||
