161. 题目: Altered microbial resource limitation regulates soil organic carbon sequestration based on ecoenzyme stoichiometry under long‐term tillage systems
期刊: Land Degradation & Development
作者: Xiaojun Song, Jingyu Li, Xiaotong Liu, Guopeng Liang, Shengping Li, Mengni Zhang, Fengjun Zheng, Bisheng Wang, Xueping Wu, Huijun Wu
摘要: Soil microbial metabolism is critically important for regulating soil carbon (C) sequestration. However, how soil organic C (SOC) stock responses to the changes in microbial resource limitation and microbial C use efficiency (CUE) under long-term tillage system remains uncertain. Soil samples were randomly collected from a long-term (19 years) tillage experiment growing winter wheat with three treatments (i.e., moldboard plow without straw retention (MPN), no-tillage with straw retention (NTS), and subsoiling with straw retention (SSS)) and an adjacent natural grassland (GRL) in 2018. We analyzed microbial resource limitation and CUE based on ecoenzyme stoichiometry. Results revealed that the reduction of soil bulk density and total dissolved nitrogen (N) resulted in an increased vector angle. Higher total dissolved N and lower vector length jointly led to higher CUE under long-term conservation tillage practices (i.e., NTS and SSS). Notably, the higher CUE and soil available phosphorus as well as the lower N limitation both directly contributed explaining the increase in SOC stock under conservation tillage practices. Overall, long-term conservation tillage practices could alleviate microbial resource limitation by enhancing available nutrients to promote SOC sequestration This study provides new knowledge to enhance the understanding of SOC stock regulated by microbial resource limitations and microbial C use efficiency.
162. 题目: Subsurface organic ameliorant plus polyethylene mulching strengthened soil organic carbon by altering saline soil aggregate structure and regulating fungal community
期刊: Land Degradation & Development
作者: Hongyuan Zhang, Huancheng Pang, Jiashen Song, Fangdi Chang, Jing Wang, Xiquan Wang, Yitao Zhang, Leanne Peixoto, Yuyi Li
摘要: Subsurface organic ameliorant plus polyethylene mulching is a novel strategy for saline soil improvement and utilization in China. However, little is known about how this strategy impacts soil organic carbon (SOC) both directly (carbon input) and indirectly (soil aggregates protection and microbial regulation). Therefore, a field experiment was arranged and sampled after three years, including four treatments, i.e., no ameliorant with and without polyethylene mulching, and subsurface (10–30 cm soil depth) organic ameliorant with and without polyethylene mulching. Subsurface organic ameliorant raised the SOC content in the 0–40 cm by 70% and 90% with and without mulching, respectively. Subsurface organic ameliorant converted the major aggregation size from <0.053 mm to 0.25–2 mm, indicating that both direct carbon (C) input and indirect soil aggregates protection contributed to the increase in SOC content. In contrast, polyethylene mulching reduced the SOC content by 16% and 6% with and without organic ameliorant respectively. This was due to lower fungal diversity by 9–14% and supported by the positive effect from fungal diversity to SOC. Further, the subsurface organic ameliorant plus polyethylene mulching increased SOC by 61% through direct C input, indirect soil aggregates protection and microbial regulation. Meanwhile, the contribution of physical protection (standardized total effect, STE = 0.223–0.294) was higher than microbial regulation (STE = 0.040–0.162) according to a structural equation model. Consequently, subsurface organic ameliorant plus polyethylene mulching represents a feasible agricultural practice to increase the SOC content for saline soil amelioration.
163. 题目: Mechanisms of straw biochar’s improvement of phosphorus bioavailability in soda saline-alkali soil
期刊: Environmental Science and Pollution Research
作者: Yuefen Li, Guanghui Li
摘要: High pH and exchangeable sodium percentage, structural deterioration due to alkalinity, and nutrient deficiencies are typical characteristics of soda saline-alkali soil. In addition, phosphorus is typically the main limiting nutrient. Thus, there have been intense efforts to counter the salinity and improve the phosphorus availability of these soils (which cover large and growing areas). A promising approach is long-term application of straw biochar, which can significantly reduce soil salinity and promote the transformation of soil phosphorus. However, the mechanisms involved remain unclear. Thus, major aims of this review are to systematically address the mechanisms whereby biochar improves phosphorus bioavailability in soda saline-alkali soil through changes in the soil’s physico-chemical properties, aggregate stability, contents of organic acids, enzyme activities, key functional genes, and microbial community structure. Another is to provide theoretical foundations for establishing effective methods for applying straw biochar to improve soda saline-alkali land and optimize phosphorus fertilizer applications.
164. 题目: Straw residue incorporation and potassium fertilization enhances soil aggregate stability by altering soil content of iron oxide and organic carbon in a rice–rape cropping system
期刊: Land Degradation & Development
作者: Bin Xue, Li Huang, Xiaokun Li, Jianwei Lu, Ruili Gao, Muhammad Kamran
摘要: Both iron (Fe) oxide and soil organic carbon (SOC) content, among other factors, drive the development and subsequent stability of soil aggregates. However, the mechanism of these drivers in paddy-upland rotation systems with straw residue incorporation is not well understood. In this multiyear (2011-2017) trial, we sought to study the factors which drive the stability of soil aggregates in such a rice-rape (RR) agronomic system. In order to examine the effect of straw residue incorporation and potassium fertilization on soil aggregation dynamics, we divided our trial into four treatments: inorganic phosphorus (P) and nitrogen (N) fertilizer; inorganic NPK fertilizer; inorganic NP fertilizer plus straw residue; and inorganic NPK fertilizer plus straw residue. Treatments which incorporated straw residue significantly increased both the geometric mean diameter (GMD) and the mean weight diameter (MWD) of soil aggregates. Soil aggregate stability was greater after rape harvest than after rice harvest, while SOC shows the opposite trend. Straw residue incorporation increased the SOC and, specifically, concentrations of aliphatic-C and aromatic-C, particularly in aggregates greater than 0.25 mm. Straw residue addition significantly increased both the amorphous (Feo) and complex iron oxide (Fep) contents of soil. In both bulk soil and in aggregates greater than 5 mm, SOC and Fep were positively correlated with MWD, while in aggregates less than 5 mm, Feo was positively correlated with MWD. Overall, we suggest that the increased concentrations of SOC, alkane-C, Feo, and Fep in soils after incorporation of straw residue were responsible for increasing soil aggregate stability.
165. 题目: Sources, burial flux and mass inventory of black carbon in surface sediments of the Daya Bay, a typical mariculture bay of China
期刊: Marine Pollution Bulletin
作者: Solomon Felix Dan, Dongyang Cui, Bin Yang, Xilong Wang, Zhiming Ning, Dongliang Lu, Zhenjun Kang, Haifang Huang, Jiaodi Zhou, Dandan Cui, Qiuping Zhong
摘要: The contents of chemothermal oxidation (CTO)-derived black carbon (BC) and organic carbon (OC) and their stable isotopes (δ13CBC and δ13COC), including major elemental oxides, and grain sizes were measured to constrain the sources, burial flux, and mass inventory of BC in surface sediments of the Daya Bay. Surface sediments were mainly clayey silt (>90%) and contained 0.28–1.18% OC and 0.05–0.18% BC. Fossil fuel emission and physical erosion contributed to the sedimentary BC sources. High BC/OC ratio (6–30%), burial flux (154.88–922.67 μg cm−2 y−1), and mass inventory (22–34 Gg y−1) of BC in the upper 5 cm of surface sediments indicated that the Daya Bay is a significant sink of BC. The high accumulation of BC in sediments is attributed to a strong affinity to fine-grained sediments due to the enrichment of muddy biodeposits excrements from the cultured species in the bay.
166. 题目: The detection of bacterial exometabolites in marine dissolved organic matter through ultrahigh‐resolution mass spectrometry
期刊: Limnology and Oceanography: Methods
作者: Sarah K. Bercovici, Thorsten Dittmar, Jutta Niggemann
摘要: Bacteria play a key role in sustaining the chemodiversity of marine dissolved organic matter (DOM), yet there is limited direct evidence of a major contribution of bacterial exometabolites to the DOM pool. This study tests whether molecular formulae of intact exometabolites can be detected in natural DOM via untargeted Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). We analyzed a series of quantitative mixtures of solid-phase extracted DOM from the deep ocean, of a natural microbial community and selected model strains of marine bacteria. Under standard instrument settings (200 broadband scans, mass range 92–1000 Da), 77% of molecular formulae were shared between the mesocosm and marine DOM. However, there was < 10% overlap between pure bacterial exometabolome with marine DOM, and in mixing ratios closest to mimicking natural environments (1% bacterial DOM, 99% marine DOM), only 4% of the unique bacterial exometabolites remained detectable. Further experiments with the bacterial exometabolome DOM mixtures using enhanced instrument settings resulted in increased detection of the exometabolites at low concentrations. At 1000 and 10,000 accumulated scans, 23% and 29% of the unique molecular formulae were detectable at low concentrations, respectively. Moreover, windowing a specific mass range encompassing a representative fraction of exometabolites tripled the number of unique detected formulae at low concentrations. Routine FT-ICR-MS settings are thus not always sufficient to distinguish bacterial exometabolome patterns from a seawater DOM background. To observe these patterns at higher sensitivity, we recommend a high scan number coupled with windowing a characteristic region of the molecular fingerprint.
167. 题目: A multiproxy approach to long-term herbivore grazing dynamics in peatlands based on pollen, coprophilous fungi and faecal biomarkers
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: A.L. Davies, L. Harrault, K. Milek, E.L. McClymont, M. Dallimer, A. Hamilton, J. Warburton
摘要: Herbivory plays a significant role in regulating many contemporary terrestrial plant ecosystems, but remains an imperfectly understood component of past ecosystem dynamics because the diagnostic capability of methods is still being tested and refined. To understand the efficacy of a multiproxy approach, we compare the sensitivity of pollen and coprophilous fungal spores (CFS) to changes in grazing intensity over the last 100–150 years in six peat cores from three UK upland areas, and apply faecal lipid biomarkers to two of the cores, using agricultural census data to calculate an independent record of herbivore density. Rising sheep density adversely affected moorland ecology over the last century, which therefore provides a suitable period to test the sensitivity of these proxies. In particular, we assess whether CFS can be used to track variations in large herbivore densities over time, since this has received less attention than their ability to identify high grazing levels. At selected sites, we test whether faecal lipid biomarkers can be used to identify which herbivore species were present. Our results highlight the differential sensitivity of each proxy, demonstrating on peat- and moorlands (i) that peak CFS abundance is a more consistent indicator of ecologically influential (high) herbivore levels than variations in animal density through time; (ii) when recorded with high CFS values, the decline or disappearance of grazing-tolerant pollen taxa is a reliable indicator of high herbivory; and (iii) at low herbivore densities, faecal lipid biomarkers are not an effective indicator of herbivore presence or identity. Quantitative reconstructions of past herbivory and identifying grazer species therefore remain challenging. However, our findings indicate that pollen and CFS provide complementary evidence for high intensity grazing, and emphasise that studies using CFS should aim to define ‘high’ herbivore levels in terms of the grazing sensitivity of the ecosystem, rather than relative animal abundance.
168. 题目: Decoupled abiotic and biotic drivers of aboveground and topsoil organic carbon stocks in temperate forests
期刊: Land Degradation & Development
作者: Maryam Kazempour Larsary, Hassan Pourbabaei, Ali Salehi, Rasoul Yousefpour, Arshad Ali
摘要: Forests are the major components of global carbon (C) cycling, and hence, it is crucial to explore the drivers of forest functions related to C sequestration. Here, using the multiple linear regressions models (MLMs) and structural equation models (SEMs), we evaluated how abiotic (i.e., soil nutrients and topography) and biotic [i.e., functional trait diversity (FTD) and functional trait identity (FTI)] factors regulate aboveground C (AGC) and topsoil (0-30 cm) organic C stocks (SOC) across 104 plots in temperate forests of Northern Iran. The optimal MLMs showed that the community-weighted mean (CWM) of wood density and functional divergence increased but functional evenness decreased AGC stock, where FTI values contributed much (i.e., 74.40%) to the explained variance in AGC stock as compared to FTD indices (12.86%) and abiotic factors (12.74%). On contrary, SOC stock was mainly promoted by soil available phosphorus, where abiotic factors contributed much (92.62%) to the explained variance as compared to FTD indices (6.73%) and FTI values (0.65%). The final best-fitted SEMs showed that AGC stock was strongly controlled (β = 0.64) by FTI values (i.e., a latent variable of CWM of wood density and plant maximum height), whereas SOC stock was strongly controlled (β = 0.74) by abiotic factors (i.e., a latent variable of soil available phosphorus and total nitrogen). We argue that suitable functional strategies in combination with soil nutrients should be taken into priority during the forestland management and policy plans for the improvement of C stocks in above- and below-ground compartments of forest ecosystems.
169. 题目: Organic matter biomarker and 13C NMR characteristics of soil and sediment standard reference materials from China
期刊: Science of The Total Environment
作者: Guodong Sun, Chun Cao, Mengke Wang, Huishan Li, Yinghui Wang, Guisen Deng, Junjian Wang
摘要: Soil and sediment organic matter (OM) in terrestrial environments represent two critical organic carbon pools on Earth and are likely subject to distinct degrees of oxidation and modification. However, few studies have identified critical molecular-level characteristics that differentiate soil and sediment OM from various climate zones. Using biomarkers and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy analyses, we studied the OM characteristics of 11 soil and 7 sediment standard reference materials (SRMs) originating from various geographical locations in China. Results showed significantly higher concentrations of lignin phenols in sediment OM than in soil OM, which may result from protection by higher contents of CaO and less microbial degradation in sediments. Nevertheless, the relative abundances of solvent-extractable lipids (alkanes, alkanols, and alkanoic acids) and ester-bound cutin and suberin biomarkers did not differ significantly between soil and sediment SRMs. The concentrations of lignin biomarkers decreased with increasing weathering degree of the soil, while cutin biomarkers increased with mean annual temperature and precipitation. This phenomenon was not observed in sediment SRMs. This study reveals the distinct OM characteristics between Chinese soil and sediment SRMs and provides fundamental data for future studies to link OM characteristics and functions.
170. 题目: The effects of biochar on antibiotic resistance genes (ARGs) removal during different environmental governance processes: A mini review
期刊: Journal of Hazardous Materials
作者: Binbin Shao, Zhifeng Liu, Lin Tang, Yang Liu, Qinghua Liang, Ting Wu, Yuan Pan, Xiansheng Zhang, Xiaofei Tan, Jiangfang Yu
摘要: Antibiotic resistance genes (ARGs) pollution has been considered as one of the most significant emerging environmental and health challenges in the 21st century, many efforts have been paid to control the proliferation and dissemination of ARGs in the environment. Among them, the biochar performs a positive effect in reducing the abundance of ARGs during different environmental governance processes and has shown great application prospects in controlling the ARGs. Although there are increasing studies on employing biochar to control ARGs, there is still a lack of review paper on this hotspot. In this review, firstly, the applications of biochar to control ARGs in different environmental governance processes were summarized. Secondly, the processes and mechanisms of ARGs removal promoted by biochar were proposed and discussed. Then, the effects of biochar properties on ARGs removal were highlighted. Finally, the future prospects and challenges of using biochar to control ARGs were proposed. It is hoped that this review could provide some new guidance for the further research of this field.
171. 题目: Plant–microbial linkages regulate soil organic carbon dynamics under phosphorus application in a typical temperate grassland in northern China
期刊: Agriculture, Ecosystems & Environment
作者: Jiayu Shi, Jirui Gong, Xiaobing Li, Zihe Zhang, Weiyuan Zhang, Ying Li, Liangyuan Song, Siqi Zhang, Jiaojiao Dong, Taoge-tao Baoyin
摘要: Anthropogenic activities have increased ecosystem phosphorus (P) inputs and have affected terrestrial ecosystem carbon (C) cycles. However, the fate of soil organic C (SOC) under P addition remains elusive, and the potential mechanisms underlying plant-microbial linkages mediated SOC formation and decomposition are poorly understood. Here, we conducted a field P fertilization experiment to explore the effects on SOC dynamics in a typical temperate grassland in northern China. P addition increased soil P availability and pH, thereby stimulating plant nutrient uptake and growth, leading to higher C inputs to soils via plant biomass (shoots, litter and roots). However, P addition exacerbated microbial N limitation, altered microbial community composition (with a lower fungal to bacterial ratio), shifted microbial life-history strategies, which transitioned from the K-strategy (Acidobacteria, Chloroflexi, and Verrucomicrobia dominant) to the r- strategy (Proteobacteria, Bacteroidetes, and Firmicutes dominant), and modulated their functional characteristics. All of these factors regulated microbial substrate preferences and changed the C components that undergo decomposition. These changes ultimately accelerated the utilization of active C, hampered passive C decomposition, and helped to create a longer-term stable C sink in the grassland.
172. 题目: Effects of organic matter characteristics on soil aggregate turnover using rare earth oxides as tracers in a red clay soil
作者: M. Halder, S. Liu, Z.B. Zhang, Z.C. Guo, X.H. Peng
摘要: Organic materials input is remarkably essential for soil aggregates formation and breakdown processes. Which characteristics of organic materials control soil aggregate turnover is still largely unknown. Eleven organic materials were characterized in terms of nutrient stoichiometry, biochemical features and carbon (C) functional groups. The effects of organic matter characteristics on soil aggregate turnover were investigated by using rare earth oxides (REOs) as tracers. REOs concentrations in four aggregate fractions were measured on 0, 14, 28, and 56 d of incubation to calculate the aggregates transformation paths and turnover time. Our results exhibited that aggregate turnover time was reduced considerably with the addition of organic materials in order of easily decomposed residues (ED) < moderately decomposed residues (MD) < slowly decomposed manures (SD) but increased within aggregate fractions in sequence of silt and clay fractions < macroaggregates < microaggregates, such effects attenuated over time (P < 0.05). Nutrient stoichiometry had no impacts on relative changes and turnover time of aggregates. Soluble sugars increased the formation of large macroaggregates at early stage of incubation, but laid no impacts on aggregate turnover time. Lignin reduced soil aggregates formation but increased aggregate turnover time in the first four weeks. C functional groups showed short-term effects on relative changes of aggregates while these characteristics did not explain aggregate turnover time except aromatic carbon. Under ED treatments, the relative formation of 0.053–0.25 mm aggregates increased with the accelerating breakdown of macroaggregates, suggesting the formation of stable microaggregates in the mid-to-late incubation time. With MD and SD application, the relative formation was increased with the decrease of aggregate breakdown over time. We proposed the pathways of soil aggregates turnover, in which the stable microaggregates were released with the breakdown of stable macroaggregates in ED treatments, while such transformation was not observed in MD or SD treatments during the incubation time. Our results demonstrate that aggregate turnover depends on the initial characteristics of incorporated organic matters defined by biochemical features and C functional groups.
173. 题目: Molecular compositions, optical properties, and implications of dissolved brown carbon in snow/ice on the Tibetan Plateau glaciers
期刊: Environment International
作者: Xiaofei Li, Pingqing Fu, Lekhendra Tripathee, Fangping Yan, Zhaofu Hu, Feng Yu, Qian Chen, Jinwen Li, Qingcai Chen, Junji Cao, Shichang Kang
摘要: Brown carbon (BrC)/water-soluble organic carbon (WSOC) plays a crucial role in glacier melting. A quantitative evaluation of the light absorption characteristics of WSOC on glacier melting is urgently needed, as the WSOC release from glaciers potentially affects the hydrological cycle, downstream ecological balance, and the global carbon cycle. In this work, the optical properties and composition of WSOC in surface snow/ice on four Tibetan Plateau (TP) glaciers were investigated using a three-dimensional fluorescence spectrometer and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. The total light-absorption of WSOC in snow/ice at 250−400 nm (ultraviolet region) and 400−600 nm (visible region) accounted for about 60.42% and 27.17% of the light absorption by the total organics, respectively. Two protein-like substances (PRLIS), one humic-like substance (HULIS), and one undefined species of chromophores in snow/ice on the TP glacier surfaces were identified. The lignins and lipids were the main compounds in the TP glaciers and were presented as CHO and CHNO molecules, while CHNOS molecules were only observed in the southeast TP glacier. The light absorption capacity of WSOC in snow/ice was mainly affected by their oxidizing properties. PRLIS and undefined species were closely linked to microbial sources and the local environment of the glaciers (lignins and lipids), while HULIS was significantly affected by anthropogenic emissions (protein/amino sugars). Radiative forcing (RF)-induced by WSOC relative to black carbon were accounted for about 11.62 ± 12.07% and 8.40 ± 10.37% in surface snow and granular ice, respectively. The RF was estimated to be 1.14 and 6.36 W m−2 in surface snow and granular ice, respectively, during the melt season in the central TP glacier. These findings contribute to our understanding of WSOC’s impact on glaciers and could serve as a baseline for WSOC research in cryospheric science.
174. 题目: Quantification of the effect of loess admixture on soil hydrological properties in sandy slope deposits
期刊: Journal of Hydrology
作者: Fei Yang, David G. Rossiter, Yue He, Volker Karius, Gan-Lin Zhang, Daniela Sauer
摘要: The admixture of loess in soils formed in sandy parent materials has considerable impact on pedogenesis and soil ecological functions. This study aimed to evaluate these effects on soil hydrology by quantifying the relationships between loess content and soil hydrological properties in a sandstone landscape covered by Pleistocene periglacial slope deposits in central Europe. Studied properties were saturated soil water capacity, field capacity, permanent wilting point, available water capacity, macro-porosity, matrix porosity and saturated hydraulic conductivity. The effect of loess addition on soil hydrological properties differed between topsoil (pedogenic A horizons) and subsoil (pedogenic B and C horizons). In the subsoil, the studied soil hydrological properties were mainly controlled by loess content. By contrast, in the topsoil the effects of loess content on soil hydrological properties were largely masked by the effects of soil organic matter (reflected by soil organic carbon, SOC). The enhancing effect of SOC on soil hydrological properties was most prominent for saturated soil water capacity and was also significant for all other parameters except permanent wilting point. After the effects of SOC were accounted for, the residual effects of loess on soil hydrological properties were the same in both topsoils and subsoils, with one exception: Saturated hydraulic conductivity decreased with increasing loess content for subsoils, but not for topsoils. This study highlighted the ecohydrological significance of loess admixture in coarse-textured soils, especially for subsoils with low SOC contents. However, for coarse-textured topsoils, SOC content plays the dominant role in affecting soil hydrological properties.
175. 题目: Lithium isotope behaviour during basalt weathering experiments amended with organic acids
期刊: Geochimica et Cosmochimica Acta
作者: Philip A.E. Pogge von Strandmann, Xianyi Liu, Chun-Yao Liu, David J. Wilson, Samantha J. Hammond, Gary Tarbuck, Ludmilla Aristilde, Alexander J. Krause, Wesley T. Fraser
摘要: Lithium (Li) isotopes are a tracer of silicate weathering processes, but how they react to different components of organic and plant-assisted weathering is poorly known. To examine the effect of organic acids compared to a strong mineral acid (HCl) on Li isotope behaviour, basalt-water weathering experiments were amended with different organic acids (glycine, malic acid, cinnamic acid, and humic acid; 0.01M). The presence of the different acids significantly affects the behaviour of dissolved elemental concentrations (such as Mg, Fe, and Al), both by increasing primary rock dissolution and hindering rates of secondary mineral formation. However, the behaviour of Li isotopes appears unaffected, with all experiments following an almost identical trend of δ7Li versus Li/Na. This observation was consistent with a single fractionation factor during the uptake of Li into secondary minerals, yet both calculated saturation states and leaching experiments on the reacted solids indicated that Li was removed into multiple phases, suggesting that the bulk combined fractionation factor barely varied. Of the Li lost from solution in the organic experiments, we estimated that on average 76% went into neoformed clays, 16% into oxides/oxyhydroxides, and 10% into the exchangeable fraction. The fractionations observed for each phase were Δ7Liexch-soln = -12.7 ± 1.7‰, Δ7Liox-soln = -26.7 ± 0.4‰, and Δ7Liclay-soln = -21.6 ± 3.3‰. These fractionations were identical, within error, to those from experiments with organic-free water, implying that the Li isotope behaviour was unaffected by the presence of organic acids in the weathering reaction. This result has interesting consequences for the interpretation of Li isotopes in terms of plant-assisted weathering and the geological record of terrestrialisation. In particular, it appears to imply that seawater Li isotope records can be expected to resolve the integrated effect of plants on weathering fluxes or weathering congruence, rather than being sensitive to specific organic-mediated weathering mechanisms.
176. 题目: Clarifying the fate of dissolved organic carbon in turbid glacier meltwater rivers in Svalbard via a series of incubations
作者: Zhuo-Yi Zhu
摘要: The dissolved organic carbon (DOC) of Svalbard’s glacier meltwater has received limited attention. Due to the northward ocean current, terrestrial DOC output from Svalbard eventually enters the Arctic Ocean, rather than travelling southward into the Atlantic. This makes the role of Svalbard glaciers in the Arctic marine carbon budget significantly different from that of Greenland glaciers. Field work was conducted in Ny-Ålesund, Svalbard in late summer, 2017 to reveal the fate of DOC in turbid glacier meltwaters in Svalbard. Based on mixing incubation over 25 h, bio- and photo-degradation over 10 days, and long-term biodegradation over 13 months, it is believed that glacier meltwater DOC fraction is linearly mixed and diluted with seawater in the turbid plume area due to light limitation. When the light limitation is removed (e.g., in the clear offshore waters), 78% of the DOC undergoes photo-degradation or photo-triggered synergistic degradation within 10 days, rather than solely microbial degradation. Over the long-term, 73% of initial DOC was lost after being kept in the dark for 13 months. This work underlines that 4/5 of the Svalbard glaciers DOC would be degraded in Arctic coast within 10 days after entering the sea, generating a positive feedback to global warming. Photo-degradation, and/or photo-triggered synergistic degradation, is the key mechanism. Approximately one-fifth of the original concentration exhibited resistance and this fraction of DOC would be transported out of the fjord and likely into the Arctic Ocean.
177. 题目: Soil warming and nitrogen addition facilitates lignin and microbial residues accrual in temperate agroecosystems
期刊: Soil Biology and Biochemistry
作者: Lixiao Ma, Zhaoqiang Ju, Yunying Fang, Tony Vancov, Qiqi Gao, Di Wu, Aiping Zhang, Yanan Wang, Chunsheng Hu, Wenliang Wu, Zhangliu Du
摘要: Both warming and nitrogen (N) addition can affect the chemistry and characteristics of soil organic matter (SOM). However, their interactive impacts on molecular compositions and origins (plant- or microbial-derived) in agroecosystems are indeterminate. A nine-year field trial study in Northern China was undertaken to quantify the effects of warming (+2 °C), N addition (315 kg N ha−1 yr−1), and their interaction on SOM content and its composition, using biomarkers (i.e., free lipids, lignin phenols and amino sugars) and 13C NMR. Despite insignificant changes in bulk SOM content, the characteristics (i.e., molecular constituents, lability, and source origin) were significantly influenced by warming and/or N addition in surface soil (0–10 cm), but not in the subsurface soil (10–20 cm). The SOM was composed of approximately 18–27% microbial residues with the bulk derived from fungi (up to 4–fold higher than bacteria). Warming alone reduced total free lipids (mainly short-chain lipids,
178. 题目: Spatial differentiation of sediment organic matter isotopic composition and inferred sources in a temperate forest lake catchment
期刊: Chemical Geology
作者: Peter M.J. Douglas, Emerald Stratigopoulos, Sanga Park, Benjamin Keenan
摘要: Freshwater sediments are important carbon reservoirs, but the extent to which different components of soil or aquatic organic matter (OM) are deposited in these sediments is not well defined. Bulk sediment carbon (δ13C) and nitrogen (δ15N) stable isotope ratios, as well as radiocarbon, are valuable tracers for sediment OM sources, but there are few studies comparing the isotopic composition of soil and sediment OM at the catchment scale. We analyzed spatial variation in δ13C, δ15N, 14C, and C:N ratios in OM from soils, stream and lake sediments, and aquatic plants and algae, in a temperate forest lake catchment in southern Quebec, and used a Bayesian model to estimate source mixtures for sediment OM. Sediments at the stream mouths entering the lake were characterized by high C:N ratios, high fraction modern carbon (Fm), and low δ13C, indicating preferential deposition of plant-derived OM. In contrast, sediments sampled further upstream during a period of low streamflow indicated a larger proportion of microbial OM based on low C:N ratios and high δ15N. In lake sediments we observed zonation of OM isotopic composition by water depth. Shallow sediments (0–1 m water depth) were characterized by high amounts of plant-derived OM, while intermediate-depth sediments (1–3 m) were characterized by high δ13C, indicating an increased input of OM from aquatic plants. Deep lake sediments (> 4 m) were characterized by low δ13C and Fm values, which likely reflect greater input of phytoplankton OM. Stream sediments downstream of the lake exhibited high δ15N and low Fm values, implying a greater input of aged microbial biomass from soils. Our results indicate catchment-scale spatial differentiation in the source of OM in sediments, with zones of preferential deposition of terrestrial plant, aquatic plant, phytoplankton, and soil microbial biomass.
179. 题目: Carbon limitation may override fine-sediment induced alterations of hyporheic nitrogen and phosphorus dynamics
期刊: Science of The Total Environment
作者: Nergui Sunjidmaa, Clara Mendoza-Lera, Sandra Hille, Christian Schmidt, Dietrich Borchardt, Daniel Graeber
摘要: The hyporheic zone underneath stream channels is considered a biogeochemical hotspot reducing nutrient loads being transported downstream due to its high surface-to-volume ratio in combination with the hyporheic exchange. However, the effect of environmental stressors such as high amounts of fine sediment (FS; grain size <0.2 mm) on nutrient cycling in the hyporheic zone are not well understood. Physical clogging caused by fine sediment (FS) decreases the hyporheic exchange, thus, diminishing its potential to reduce nutrient loads despite increasing its surface-to-volume ratio. We determined the effect of physical clogging on nutrient cycling based on net change rates of dissolved inorganic nitrogen (DIN; nitrate-N, ammonium-N), soluble reactive phosphorus (SRP), and dissolved organic carbon (DOC) for a sand and gravel hyporheic zone. We performed three experimental runs in 12 flumes with four-week duration each following a factorial design. First, we determined nutrient cycling in sand and gravel in absence of clogging, and then tested the clogging effect for each sediment type under increasing clogging (0-480 g of FS addition increasing by 60 g per level). Without clogging, gravel acted as a source of nitrate-N; and both sand and gravel released SRP. Regardless of the clogging level and the resulting reduced hyporheic exchange, we found no changes in DOC and nitrate-N dynamics but net-release of ammonium-N and SRP for gravel. In contrast, in sand, physical clogging inhibited DOC release for flumes with the higher FS. We propose that not physical clogging but DOC availability limited the nutrient uptake, as molar ratios of DOC to DIN and SRP ranged 1.2–1.5 and 77–191, respectively, indicating severe C limitation of N-uptake and partial C limitation of P-uptake. Our results suggest an interplay between nutrient molar ratios and physical clogging, which emphasize the interactions between hydrology and the stoichiometry of organic carbon, nitrogen and phosphorus in the hyporheic zone.
180. 题目: Phytomanagement of Pb/Zn/Cu tailings using biosolids-biochar or -humus combinations: Enhancement of bioenergy crop production, substrate functionality, and ecosystem services
期刊: Science of The Total Environment
作者: Mariam K. Al-Lami, Nadège Oustriere, Eva Gonzales, Joel G. Burken
摘要: The extreme characteristics of mine tailings generally prohibit microbial processes and natural plant growth. Consequently, vast and numerous tailings sites remain barren for decades and highly susceptible to windblown dust and water erosion. Amendment-assisted phytostabilization is a cost-effective and ecologically productive approach to mitigate the potential transport of residual metals. Due to the contrasting and complementary characteristics of biosolids (BS) and biochar (BC), co-application might be more efficient than individually applied. Studies considering BS and BC co-application for multi-metal tailings revegetation are scarce. As tailings revegetation is a multidimensional issue, clearly notable demand exists for a study that provides a comprehensive understanding on the co-application impact on interrelated properties of physicochemical, biological, mineral nitrogen availability, metal immobilization, water-soil interactions, and impacts on plant cultivation and biomass production. This 8-month greenhouse study aimed at investigating the efficacy of co-application strategies targeting BS and carbon-rich amendments (BC or humic substances (HS)) to phytomanage a slightly alkaline Pb/Zn/Cu tailings with bioenergy crops (poplar, willow, and miscanthus). A complementary assessment linking revegetation effectiveness to ecosystem services (ES) provision was also included. Owing to their rich nutrient and organic matter contents, BS had the most pronounced influence on most of the measured properties including physicochemical, enzyme activities, NH4+-N and NO3−-N availability, immobilization of Zn, Cu, and Cd, and biomass production. Co-applying with BC exhibited efficient nutrient release and was more effective than BS alone in reducing metal bioavailability and uptake particularly Pb. Poplar and willow exhibited more superior phytostabilization efficiency compared to miscanthus which caused acidification-induced metal mobilization, yet BC and BS co-application was effective in ameliorating this effect. Enhancement of ES and substrate quality index mirrored the positive effect of amendment co-application and plant cultivation. Co-applying HS with BS resulted in improved nutrient cycling while BC enhanced water purification and contamination control services.