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31461. 题目: Distinct bioenergetic signatures in particulate versus mineral-associated soil organic matter
文章编号: N18062516
期刊: Geoderma
作者: Elizabeth K. Williams, Marilyn L. Fogel, Asmeret Asefaw Berhe, Alain F. Plante
更新时间: 2018-06-25
摘要: Physical and chemical stabilization, environmental conditions, and organic matter composition all play vital roles in determining the persistence of soil organic matter (SOM). Fundamentally, SOM stability depends on the balance of microbial bioenergetics between the input of energy needed to decompose it (i.e., activation energy; Ea) and the net energy gained (i.e., energy density; ED) from its decomposition. This relationship is complicated in soils by chemical and physical protection mechanisms, which require additional energies to overcome for decomposition to occur. In this study, we analyze the bioenergetics of soil density fractions, which vary in their degrees of organic matter-mineral association, and show that the relationship of ED and Ea has the ability to provide information about relative differences in SOM chemical composition and stability. Our results demonstrate distinct bioenergetic signatures between particulate, light (free and occluded) fractions versus mineral-associated, heavy fractions isolated from soil samples collected at two depths from a climosequence along an elevation gradient in the Sierra Nevada, California. While there were no significant differences in ED and Ea within each fraction across climates, the light fractions (LF) were characterized by larger ED and Ea values, whereas the heavy fractions (HF) were characterized by smaller ED and Ea values. Combined with CHN analyses, we conclude that SOM in HF pools is likely comprised of relatively simple organic compounds that have long turnover rates because of chemical association with soil minerals, whereas the LF pools are comprised of more chemically complex molecules with low chemical reactivity and high Ea.

31462. 题目: Elevated [CO2] changes soil organic matter composition and substrate diversity in an arid ecosystem
文章编号: N18062515
期刊: Geoderma
作者: Malak M. Tfaily, Nancy J. Hess, Akihiro Koyama, R.D. Evans
更新时间: 2018-06-25
摘要: Little is known about how elevated atmospheric [CO2] will impact the dynamics of soil organic matter (SOM) in arid ecosystems. Evans et al. (2014) reported greater ecosystem carbon (C) and nitrogen (N) concentrations following 10 years exposure to elevated atmospheric [CO2] at the Nevada Desert Free-Air Carbon dioxide Enrichment (FACE) Facility (NDFF). In this study, we investigated potential mechanisms of SOC and total N accumulation and potential SOM stabilization using high resolution mass spectrometry. Samples were collected from soil profiles to 1 m in depth with 0.2 m increment under the dominant evergreen shrub Larrea tridentate and were air dried at room temperature. SOM was extracted sequentially with solvents with different polarity. The differences in the molecular composition and diversity of SOM in the different extracts were more evident in surface soils and declined with depth, and were consistent with higher SOC and total N concentrations under elevated than ambient [CO2]. Our results support the hypothesis that increased root exudation and/or microbial necromass from stabilization of labile C and N can contribute to SOM and N pools. We found that plant-derived compounds were primary substrates for microbial activity under elevated [CO2] and microbial necromass were the main constituents of stabilized SOM. Our results suggest that arid ecosystems are a potential large C sink under elevated [CO2], given arid ecosystems constitute 47% of the terrestrial land surface, and that labile compounds are transformed to stable SOM via microbial processes. Arid systems are limited by water, and thus may have a different C storage potential under changing climates than other ecosystems that are limited by nitrogen or phosphorus.

31463. 题目: Impact of drainage and soil hydrology on sources and degradation of organic matter in tropical coastal podzols
文章编号: N18062514
期刊: Geoderma
作者: Josiane Millani Lopes-Mazzetto, Judith Schellekens, Pablo Vidal-Torrado, Peter Buurman
更新时间: 2018-06-25
摘要: In podzols important environmental issues converge, including dissolved organic matter (DOM) transport, DOM-metal binding, and carbon storage in the subsoil. Therefore, it is important to understand the formation and degradation of podzols in relation to (changes in) environmental conditions. For this purpose a Holocene barrier island with coastal sand dunes (Ilha Comprida, SE Brazil) was chosen as study area. The island is build-up of five geomorphic units that have different age (from >5000 to 325 y BP), vegetation (restinga ecosystems), soil hydrology (flat units or units with ridges and swales) and drainage (poorly drained, well-drained, and improved drainage). Representative profiles were studied for each geomorphic unit, resulting in 100 samples from A, E, B, and C horizons, from which soil organic matter (SOM) was isolated by alkaline extraction. To better understand carbon sources and dynamics, we additionally sampled litter from different vegetation types and DOM from various sources. The molecular composition of SOM, DOM and litter was analyzed with pyrolysis gas chromatography mass spectrometry (pyrolysis-GC/MS). Comparing the pyrolysates of all samples (DOM, SOM and litter) factor analysis demonstrated that the major difference in molecular composition (factor 1) was related to the contribution from DOM (phenol, acetic acid, benzofurans, pyridine, benzene and naphthalene) or in-situ root material (straight chain aliphatics and methoxyphenols from the biomacromolecules suberan and lignin, respectively). The contribution from DOM or roots was characteristic for a profile i.e. without much change with depth. Factor 2 reflected decomposition processes, and showed that the predominantly DOM-derived B horizons were relatively enriched in aromatics compared to DOM, indicating selective decay and/or selective precipitation. In geomorphic units with swales and ridges that received DOM via groundwater flow from the catchment area, the B horizon was predominantly DOM-derived; these profiles showed large differences in the contribution from black carbon (BC; (poly)aromatics), with the younger profiles showing a larger contribution from BC in precipitated DOM. B horizons with a relatively large contribution from in-situ root materials were found in well-drained soils and in some of the poorly drained soils without lateral groundwater flow from the catchment area, i.e., the flat geomorphic unit without ridges and swales. Microbial material (N-containing compounds and sugars) was associated with relatively recent SOM and with well-drained conditions at present. i.e., well-drained profiles, and profiles with improved drainage.

31464. 题目: Irrigation with sediment-laden river water affects the soil texture and composition of organic matter fractions in arid and semi-arid areas of Northwest China
文章编号: N18062513
期刊: Geoderma
作者: Linlin Dong, Haidong Zhang, Lingqing Wang, Dongsheng Yu, Feixia Yang, Xuezheng Shi, Hafsa Saleem, M. Saleem Akhtar
更新时间: 2018-06-25
摘要: Soil organic carbon (SOC) is the largest reservoir of organic carbon in the terrestrial ecosystem, and is an effective mean of enhancing crop production in the irrigated area of the arid and semi-arid regions. Understanding long-term changes in composition of SOM under irrigation from sediment-laden Yellow River water is essential to manage sustainability issues in the agro-ecosystem. A total of 45 soils, including 39 of irrigated fields differing in irrigation history and 6 of non-cultivated and non-irrigated natural fields as the control, were sampled at 0–20 cm depth. The soil was analyzed for total SOC content, partitioning of light (LFOM) and heavy (HFOM) fraction organic matter based on NaI solution density of 1.7 g m3 and for particle size distribution. Compared to the non-irrigated and non-cultivated control soil, the LFOM and HFOM in irrigated soils increased with the duration of irrigation though SOM existed dominantly as the heavy fraction. The soils irrigated for <50 years have overall lesser LFOM and HFOM and more sand compared to those with >50 years irrigation. Further, a positive relationship existed between the fine particle and the SOM or its fractions (negative relation with coarse particle) suggesting either SOM accumulated as fine particles or the fine mineral particles better preserved SOM. In addition, field soil moisture at the time of sampling during October 2009 correlated with HFOM (p < 0.001) and LFOM (p < 0.01). The study suggested that the long-term irrigation with water diverted from Yellow River increased fine particle, SOC and the light and heavy fraction in the Ningxia Irrigation Zone.

31465. 题目: Modelling of sand/dust emission in Northern China from 2001 to 2014
文章编号: N18062512
期刊: Geoderma
作者: Heqiang Du, Tao Wang, Xian Xue, Sen Li
更新时间: 2018-06-25
摘要: Wind erosion is a major contributing factor to soil degradation and environmental pollution. As a hot spot of wind erosion, Northern China suffers from severe wind erosion hazards. Besides, there is an ongoing controversy regarding the magnitudes of sand/dust emissions of anthropogenic sources. To understand the mechanism of soil degradation and environmental pollution caused by wind erosion, and to resolve the controversy whether sand/dust emissions is from natural or anthropogenic sources in Northern China, accurate spatio-temporal distributions of sand/dust emission should be obtained. Herein, a wind erosion model with a high spatio-temporal resolution was developed and employed to identify the sand and dust emissions of areas with different land cover types. The sand and dust emission hot spots from 2001 to 2014 were mainly distributed in the Gashun Gobi and Kumutage Deserts, those are all natural areas. In these regions, the average sand and dust emissions exceeded 10,000 kg/m/y (year) and 240 g/m2/y, respectively. The intensities of sand and dust emissions demonstrated significant decreasing trends during this time. According to Moderate Resolution Imaging Spectroradiometer (MODIS) land cover data, the average sand/dust emission rates in natural sources were much higher than that in anthropogenic areas, e.g. from 2001 to 2014, the average annual dust emission of Northern China was about 130 Tg/y, and only approximately 3.7% of dust emissions originated from anthropogenic areas. Dust deflation correspondingly caused the entrainment of soil nutrients into atmosphere and result in soil degradation. Our results also show that the Soil Organic Carbon (SOC) loss due to wind erosion in Northern China was about 0.9 Tg/y and that 32.5% and 7.5% of the SOC loss originated from grasslands (including woody savannas, savannas, and grasslands) and farmlands (including croplands and cropland/natural vegetation mosaics), respectively. With regard to such severe sand and dust emissions, we believe that the results of this study could provide valuable information for the creation of strategies to cope with wind erosion hazards and measures to control the extent of wind-blown sand. In addition, the proposed model could be of interest to ecological and environmental researchers.

31466. 题目: Moderate thinning increases soil organic carbon in Larix principis-rupprechtii (Pinaceae) plantations
文章编号: N18062511
期刊: Geoderma
作者: Junyong Ma, Fengfeng Kang, Xiaoqin Cheng, Hairong Han
更新时间: 2018-06-25
摘要: Forest thinning management practices such as thinning play a major role in the process of soil organic carbon (SOC) sequestration, however, the mechanism for SOC variations is still unclear. The objectives of this study were to estimate SOC stock and its active chemical components following a short term density adjustment of stand woods. Three treatments, low intensity thinning (removal of 15% of the trees, three 25 25 m repeated plots), moderate thinning (30% removal), and heavy intensive thinning (50% removal) were compared to control plots with no thinning three years before sampling of soil carbon composition. A number of carbon components (i.e. SOC; soil total nitrogen, TN; permanganate oxidizable C, POXC; dissolved organic carbon, DOC; microbial biomass carbon, MBC) were measured in five soil layers within the Larix principis-rupprechtii plantation throughout the growing seasons of 2015 and 2016. Results indicated both SOC content and its active component, POXC content, were maximized under the moderate density adjustment (p < 0.01). Density adjustment significantly affected POXC/SOC ratio (p < 0.001), with maximum POXC content per unit SOC content also under moderate density adjustment. However, density adjustment hardly had any impact on DOC or MBC, both of which showed more obvious seasonal dynamics than SOC, TN and POXC. Summer affected SOC storage by altering the POXC, TN and MBC. Our results suggest that effects of density adjustment on POXC drive variation in SOC.

31467. 题目: No-tillage with continuous maize cropping enhances soil aggregation and organic carbon storage in Northeast China
文章编号: N18062510
期刊: Geoderma
作者: Yan Zhang, Xiujun Li, Edward G. Gregorich, Neil B. McLaughlin, Xiaoping Zhang, Yafei Guo, Aizhen Liang, Ruqin Fan, Bingjie Sun
更新时间: 2018-06-25
摘要: In Northeast China, conventional tillage practices involve removal of crop residue after harvest and prior to moldboard plowing; this has been shown to cause a decline of soil organic carbon (SOC) and degradation of soil structure. No-tillage has been suggested to be an effective way to increase SOC storage but its effectiveness in some soils and climates has been questioned. Different cropping systems also influence SOC storage. Hence, we established an experiment to evaluate how a combination of different tillage and cropping systems could improve soil aggregation and organic carbon storage. We included five treatments: a) NTMS: no tillage with maize (Zea mays L.)-soybean (Glycine max Merr.) (MS) rotation; b) MPMS: moldboard plowing with maize-soybean rotation; c) NTMM: no tillage with continuous maize (MM); d) MPMM: moldboard plowing with continuous maize; e) CTMM: conventional tillage with continuous maize (the conventional farming practice in Northeast China). All crop residues were returned to the soil except in the CTMM treatment. Returning residue to the soil significantly increased SOC storage in all tillage/cropping systems with NTMM having the highest increase in rate of SOC storage at 0.80 Mg C ha 1 yr 1 relative to the start of the experiment. The CTMM depleted SOC storage at rate of 0.52 Mg C ha 1 yr 1 relative to the start of the experiment. Soil under NTMS exhibited a significant SOC decline deep in the soil (5–30 cm) but overall SOC storage in 0–30 cm profile was equal to that under MPMS. The NTMM had the highest SOC storage and the highest proportion and associated organic carbon (OC) in occluded micro-aggregates (53–250 μm, inside of 250 μm aggregates) across all experimental treatments. The OC in occluded micro-aggregates was much higher than that associated with unprotected micro-aggregates (53–250 μm, outside of 250 μm aggregates). The effects of tillage on aggregate size and OC concentration occurred mainly in the surface layer (0–5 cm) whereas the effect of cropping system on aggregate size and OC concentration occurred at deeper depths. The MS cropping system increased the proportion of silt-clay (<53 μm, outside of 250 μm aggregates) over MM while occluded silt-clay (<53 μm, inside of 250 μm aggregates) in MM was greater than in MS in all layers. The NTMM treatments improved SOC storage and aggregation over the other treatments.

31468. 题目: Physicochemical surface properties of different biogenic silicon structures: Results from spectroscopic and microscopic analyses of protistic and phytogenic silica
文章编号: N18062509
期刊: Geoderma
作者: Daniel Puppe, Martin Leue
更新时间: 2018-06-25
摘要: The significance of biogenic silicon (BSi) for Si cycling in terrestrial biogeosystems has been acknowledged since decades. Its importance originates from the fact that BSi generally is more soluble than silicate minerals and thus i) controls Si fluxes from terrestrial to aquatic ecosystems and ii) plays an important role as source of readily- or plant-available Si (i.e., H4SiO4) in soils. In this context, physicochemical surface properties of BSi structures determine their dissolution kinetics. We applied transmission Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) microscopy, and confocal laser scanning microscopy (CLSM) to investigate physicochemical surface properties of different biogenic silica structures. Using these techniques we were able to detect differences on a molecular level (FTIR, DRIFT) and in surface roughness parameters (CLSM) between BSi synthesized by protists (testate amoebae, diatoms) and BSi synthesized by plants (phytoliths) as well as between fresh (extracted from plants) and aged (extracted from soils) phytoliths. While fresh phytoliths showed organic impurities that can be assigned to occluded organic matter, aged phytoliths showed additional impurities of mineral origin. This is due to the fact that the used non-destructive gravimetric extraction of phytoliths is unsuitable for a distinct differentiation between biogenic silica (phytoliths) and non-biogenic (minerogenic or microcrystalline) Si forms in general. We recommend DRIFT microscopy for analyses of phytoliths extracted from soils because this technique allows measurements of selected, single siliceous phytoliths (as well as other BSi structures). Surface roughness parameters of aged phytoliths decreased compared to the ones of fresh phytoliths indicating a decrease of specific surface areas available for dissolution processes. Physicochemical surface properties will help us to better understand the BSi status (BSi quality and quantity) of soils with implications for Si availability in soils and thus Si cycling in terrestrial biogeosystems.

31469. 题目: Sensitivity of peatland litter decomposition to changes in temperature and rainfall
文章编号: N18062508
期刊: Geoderma
作者: Michael C. Bell, Jonathan P. Ritson, Anne Verhoef, Richard E. Brazier, Michael R. Templeton, Nigel J.D. Graham, Chris Freeman, Joanna M. Clark
更新时间: 2018-06-25
摘要: Changes to climate are projected over the next 50 years for many peatland areas. As decomposition of peat-forming vegetation is likely to be intrinsically linked to these changes in climate, a clear understanding of climate-peat dynamics is required. There is concern that increased temperature and decreased precipitation could increase the rate of decomposition and put the carbon sink status of many peatlands at risk, yet few studies have examined the impact of both climatic factors together. To better understand the sensitivity of peatland decomposition to changes in both temperature and precipitation and their interaction, we conducted a short-term laboratory experiment in which plant litters and peat soil were incubated, in isolation, in a factorial design. Treatments simulated baseline and projected climate averages derived from the latest UK climate change projections (UKCP09) for Exmoor, a climatically marginal peatland in SW England. Regular carbon dioxide flux measurements were made throughout the simulation, as well as total mass loss and total dissolved organic carbon (DOC) leached. The largest effect on carbon loss in this multifactor experiment was from substrate, with Sphagnum/peat releasing significantly less C in total during the experiment than dwarf shrubs/graminoids. Climate effects were substrate specific, with the drier rainfall treatment increasing the DOC leaching from Calluna, but decreasing it from Sphagnum. Partitioning between CO2 and DOC was also affected by climate, but only for the peat and Sphagnum samples, where the future climate scenarios (warmer and drier) resulted in a greater proportion of C lost in gaseous form. These results suggest that indirect effects of climate through changes in species composition in peatlands could ultimately turn out to be more important for litter decomposition than direct effects of climate change from increased temperatures and decreased rainfall.

31470. 题目: Small-scale spatial patterns of soil organic carbon and nitrogen stocks in permafrost-affected soils of northern Siberia
文章编号: N18062507
期刊: Geoderma
作者: Alevtina Evgrafova, Tilman René de la Haye, Ina Haase, Olga Shibistova, Georg Guggenberger, Nikita Tananaev, Leopold Sauheitl, Sandra Spielvogel
更新时间: 2018-06-25
摘要: The vulnerability of soil organic matter (SOM) sequestered in permafrost-affected soils to climate change plays one of the key roles in the global carbon (C) cycle. However, it still remains unclear how changing soil and site-specific factors, associated with the changing depth of the permafrost table due to thawing, influence the spatial distribution and variability of soil organic carbon (SOC) and total nitrogen (N) stocks in high-latitude mineral soils. The relationships between the spatial variation of SOC and N stocks (0–30 cm) and active layer (AL) thickness, thickness of the organic layer (OL), soil acidity, Al and Fe hydroxides as well as plant- and microbial-derived C inputs were studied using ordinary statistics and geostatistics within six landscape patches (16 m2) in the Siberian forest-tundra ecotone underlain by warm and discontinuous permafrost. At deeper permafrost table, SOC and N stocks (0–30 cm) were lower and, according to the semivariogram analysis, an overall homogenization of SOC and N distribution at the analyzed scale occurred. Total N and SOC stocks were spatially independent from root-derived organic matter distribution (i.e. the concentration of suberin-derived monomers) at shallow AL patches, whereas there was a significant positive spatial correlation within deep AL and non-permafrost soils. Hence, the development of root systems and an increase in rooting depth, leading to “hot spots” of SOM accumulation at intensively rooted soil patches, was observed as a result of deeper AL. Total N and SOC stocks within deeper AL and non-permafrost subsoils were also positively spatially correlated with the concentration of Fe and Al hydroxides, demonstrating the importance of organo-mineral associations for SOM stabilization in soils with lower permafrost table. This study confirmed that deepening of the AL in boreal forest ecosystems may lead to an overall homogenization of SOM distribution and simultaneous development of distinct mechanisms of SOM accumulation and stabilization.

31471. 题目: Soil organic carbon prediction based on scale-specific relationships with environmental factors by discrete wavelet transform
文章编号: N18062506
期刊: Geoderma
作者: Hongfen Zhu, Wei Hu, Yaodong Jing, Yi Cao, Rutian Bi, Wude Yang
更新时间: 2018-06-25
摘要: The spatial distribution of soil organic carbon (SOC) is vital to agricultural and environmental management, and its variation is influenced by environmental factors operating at different scales and intensities. The objective of this study was to explore the scale-dependent effects of environmental factors on SOC distribution and to predict SOC based on their scale-specific relationships using wavelet transform. The spatial data of SOC, slope, soil water content (SWC), soil bulk density (SBD), sand, silt, and Landsat 8 remote sensing reflectance (Rrs) were extracted at 330 m interval along three transects in the arable land of Taiyuan basin, China. The spatial series of SOC and environmental variables along each of three transects were separated into six detail components and one approximation representing different scales using wavelet decomposition. The specific scale of each detail component was identified by Hilbert transform. The SOC variances over the entire basin were mainly explained (54%–86%) by scales of 12.70 and 21.12 km. Compared with the relationships between SOC and environmental factors at sampling scale, their multiscale correlations were better at larger scales. The SOC estimation using wavelet reconstruction based on predicted SOC at all scale components outperformed its prediction using stepwise multiple linear regression (SMLR) based on the original sampling data. The major contributing scale to SOC prediction was 12.70 km over the entire basin. In the prediction of overall SOC, Rrs was the major predictor in the upstream and downstream portions, whereas soil texture was the major contributor in the midstream portion. In this study, the SOC prediction using wavelet transform based on scale-dependent relationships with environmental variables generated new insights in soil properties estimation, and wavelet transform has potential for determining the multiscale relationships of soil properties with influencing factors.

31472. 题目: Spatial point pattern analysis of piping erosion in loess-derived soils in Golestan Province, Iran
文章编号: N18062505
期刊: Geoderma
作者: Mohsen Hosseinalizadeh, Narges Kariminejad, Giandiego Campetella, Alireza Jalalifard, Mohammad Alinejad
更新时间: 2018-06-25
摘要: Point pattern analysis of collapsed pipes as a subsurface erosion in natural and manmade conditions plays an important role to understand their landforms/features, predisposing factors, and for prevention and forecasting purposes. Thus, the present study aimed to evaluate the spatial pattern and the associated land factors of piping erosion in loess-derived soils in a semiarid climate in Golestan Province, Iran by applying numerical summary statistics. To this end, a 105 ha area with homogeneous environmental conditions (gentle slope and loess-derived soil) was selected and the maps related to 101 collapsed pipes and their features were obtained by the aerial photos provided by an unmanned aerial vehicle (UAV) with a 50 cm resolution and field survey. The mean of spatial distances between pipe locations was 309 m, and the frequency of pipes per hectare was 0.97. Moreover, soil samples of the pipe locations were collected and physical-chemical soil properties were measured in laboratory. Approximately 95% simulation envelopes were selected using the 5th-lowest and 5th-highest values of 199 Monte Carlo simulations of the null model of homogeneous complete spatial randomness. Based on the results of univariate pair correlation function, the significant aggregation of 101 collapsed pipes was observed at a scale of 0–50 m in both rangeland and agricultural land use types. The bivariate pair correlation function, which is considered to be the most informative second-order summary characteristic, was used for analyzing the statistical correlations between collapsed pipes and linear phenomena including distance from drainage networks, ridges, and roads. Based on bivariate summary statistics, collapsed pipes had positively been affected by both the distribution of drainage networks and ridges. However, the negative statistical correlations occurred between pipes and roads at the scales of 1–50 m. Also, the correlations of soil characteristics (silt content, exchangeable sodium percentage (ESP), the weight of soil in a given volume (bulk density), soil electrical conductivity (EC), and organic matter (O.M.)) of neighboring collapsed pipes were evaluated by mark correlation function. Based on mark correlation function k mm (r), a significantly positive correlation was found between the pipes density and silt content, ESP, and bulk density, when they are more than overall average. In addition, less values of EC and O.M. were positively related to the aggregation of collapsed pipes. Similar to the results of summary statistics, the maps confirmed all statistical correlations. Consequently, the outcome of this study highlights the spatial pattern of collapsed pipes and their associations in the study area.

31473. 题目: Sugarcane yield and soil carbon response to straw removal in south-central Brazil
文章编号: N18062504
期刊: Geoderma
作者: Ricardo de Oliveira Bordonal, Lauren Maine Santos Menandro, Leandro Carneiro Barbosa, Rattan Lal, Débora Marcondes Bastos Pereira Milori, Oriel Tiago Kolln, Henrique Coutinho Junqueira Franco, Jo?o Luís Nunes Carvalho
更新时间: 2018-06-25
摘要: Understanding the impacts of straw removal on quantity and quality of soil organic carbon (SOC) is crucial for sustaining or improving soil functions and producing economically viable sugarcane yields. Field experiments were carried out on commercial farms to quantify effects of straw removal on sugarcane yields, SOC stocks and the degree of soil organic matter (SOM) humification under three diverse edaphoclimatic conditions (Quirinópolis-GO, Chapad o do Céu-GO and Quatá-SP) in Brazil, while considering the effects of cover crop on sugarcane yields during two harvest seasons. Three straw removal rates (0, 50, and 100%) were arranged in a randomized block design with four replications within two paired areas, one seeded with Crotalaria spectabilis (cover crop–CC) and the other kept under bare fallow (BF) during the sugarcane-replanting period. Sugarcane yields were measured annually using an instrumented truck equipped with load cells, and soil samples were collected to a depth of 40-cm two years after establishing the trials. Straw removal for two years did not significantly influence cane yields in Quatá-SP, but in Chapad o do Céu-GO and Quirinópolis-GO, complete straw removal resulted in cumulative yield losses of up to 28 and 62 Mg ha 1 respectively. The inclusion of Crotalaria spectabilis within sugarcane cropping cycle increased two-year cumulative yields by 25 and 27 Mg ha 1 in Chapad o do Céu-GO and Quirinópolis-GO respectively. SOC response to straw removal was highly site-specific after two years. In fine-textured soils, straw removal rates did not significantly affect SOC stocks in Chapad o do Céu-GO, but in Quirinópolis-GO complete straw removal favored the depletion of SOC stock relative to partial or no straw removal in both soil layers (0–10 and 0–40 cm) of the BF area, while within the CC area SOC depletion was observed in the 0–40 cm layer. For sandy soil (Quatá-SP), complete straw removal decreased SOC stock only in the top 10 cm of the CC area. Laser-Induced Fluorescence Spectroscopy showed high degree of SOM humification in soils with depleted SOC stock, indicating that excessive straw removal was degrading soil quality by reducing the amount of labile C in the SOM. Conclusions drawn from this study indicate that, even on a short-term basis, complete straw removal already began to modify the quantity and quality of SOC, while both moderate or complete removals adversely affected sugarcane yields.

31474. 题目: Riverine particulate C and N generated at the permafrost thaw front: case study of western Siberian rivers across a 1700...
文章编号: N18062503
期刊: Biogeosciences
作者: Ivan V. Krickov, Artem G. Lim, Rinat M. Manasypov, Sergey V. Loiko, Liudmila S. Shirokova, Sergey N. Kirpotin, Jan Karlsson, and Oleg S. Pokrovsky
更新时间: 2018-06-25
摘要: In contrast to numerous studies on the dynamics of dissolved (<0.45 m) elements in permafrost-affected high latitude rivers, very little is known of the behavior of river suspended (>0.45 m) matter (RSM) in these regions. In order to test the effect of climate, permafrost and physio-geographical landscape parameters (bogs, forest and lake coverage of the watershed) on RSM and particulate C, N and P concentration in river water, we sampled 33 small and medium size rivers (10–100000km2 watershed) along a 1700km N–S transect including both permafrost-affected and permafrost-free zones of Western Siberian Lowland (WSL). The concentration of C and N in RSM decreased with the increase in river watershed size, illustrating (i) the importance of organic debris in small rivers which drain peatlands and (ii) the role of mineral matter from bank abrasion in larger rivers. The presence of lakes in the watershed increased C and N but decreased P concentrations in RSM. The C:N ratio in the RSM reflected the source from deep rather than surface soil horizon, similar to that of other Arctic rivers. This suggests the export of peat and mineral particles through suprapermafrost flow occurring at the base of the active layer. There was a maximum of particulate C and N concentration at the beginning of permafrost appearance (a sporadic and discontinuous zone, 62–64°N). This presumably reflected the organic matter mobilization from newly thawed organic horizons in soils at the active latitudinal thawing front. The results suggest that a northward shift of permafrost boundaries and an increase in active layer thickness may increase particulate C and N export by WSL rivers to the Arctic Ocean by a factor of 2, while P export may remain unchanged. In contrast, within a long-term climate warming scenario, the disappearance of permafrost in the north, the drainage of lakes and transformation of bogs to forest may decrease C and N concentration in RSM by 2 to 3 times.

31475. 题目: Quantification of lignin oxidation products as vegetation biomarkers in speleothems and cave drip water
文章编号: N18062502
期刊: Biogeosciences
作者: Inken Heidke, Denis Scholz, and Thorsten Hoffmann
更新时间: 2018-06-25
摘要: Here we present a sensitive method to analyse lignin oxidation products (LOPs) in speleothems and cave drip water to provide a new tool for paleo vegetation reconstruction. Speleothems are valuable climate archives. However, compared to other terrestrial climate archives, such as lake sediments, speleothems contain very little organic matter. Therefore, very few studies on organic biomarkers in speleothems are available. Our new sensitive method allows to use LOPs as vegetation biomarkers in speleothems. Our method consists of acid digestion of the speleothem sample followed by solid phase extraction (SPE) of the organic matter. The extracted polymeric lignin is degraded in a microwave assisted alkaline CuO oxidation step to yield monomeric LOPs. The LOPs are extracted via SPE and finally analysed via ultrahigh-performance liquid chromatography (UHPLC) coupled to electrospray ionisation (ESI) and high-resolution orbitrap mass spectrometry (HRMS). The method was applied to stalagmite samples with a sample size of 3–5g and cave drip water samples with a sample size of 100–200mL from the Herbstlabyrinth-Advent-Cave in Germany. In addition, fresh plant samples, soil water and powdered lignin samples were analysed for comparison. The concentration of the sum of eight LOPs (Σ8) was in the range of 20–84ngg 1 for the stalagmite samples and 230–440ngL 1 for the cave drip water samples. The limits of quantification for the individual LOPs ranged from 0.3–8.2ng per sample. Our method represents a new and powerful analytical tool for paleo vegetation studies and has great potential to identify the pathways of lignin incorporation into speleothems.

31476. 题目: Fodder radish seed cake biochar for soil amendment
文章编号: N18062501
期刊: Environmental Science and Pollution Research
作者: Wendel Paulo Silvestre, Paula Lúcia Galafassi, Suelem Daiane Ferreira, Marcelo Godinho, Gabriel Fernandes Pauletti, Camila Baldasso
更新时间: 2018-06-25
摘要: In this work, fodder radish seed cake (FRSC) was pyrolyzed in a rotary kiln reactor at 0, 3, and 6 rpm, at final temperature of 500 °C. Maximum biochar yield was observed at 0 rpm (≈ 26 wt.%). Increase of the rotary speed decreased the volatile matter content and increased the ash content of the biochars. Biochars exhibited alkaline pH (≈ 9.0), low electrical conductivity (< 105.6 dS m 1), and high cation exchange capacity (69 to 78 cmolc kg 1), as well as high nitrogen contents (≈ 80 g kg 1). FTIR analysis presented biochars with similar spectra, with carboxyl and carbonyl groups within the structure, along with aromatic rings and nitrogen containing functions (amides). Biochar incubation experiments in an acrisol at different biochar doses (5 g L 1 soil to 40 g L 1 soil) were performed in order to evaluate changes in soil fertility parameters caused by FRSC biochar application. Results indicated that most of macro (N, P, K, Ca, Mg) and micronutrients (S, Cu, Zn, Mn, B, Na) increased with increase of the dosage, along with the decrease in Al and H+ Al contents. An increase in pH (from 4.25 to 5.33) was also observed, in electric conductivity (from 30.0 to 45.7 dS m 1), and a decrease in soil real density (from 3.67 to 2.99 kg L 1) at the dosage of 40 g char L 1 soil.

31477. 题目: Influence of aggregation on nanoscale titanium dioxide (nTiO2) deposition to quartz sand
文章编号: N18062405
期刊: Chemosphere
作者: Zhong Tang, Tao Cheng, Leanne M. Fisher-Power
更新时间: 2018-06-24
摘要: Although extensive research has been conducted to investigate nTiO2 aggregation and deposition, effects of aggregation on concurrent/subsequent deposition of nTiO2, which has important implications to the fate and transport of nTiO2 in groundwater, has received only limited attention. The objective of this study was to investigate how pH, dissolved organic matter (DOM), and valence of background solution cation influence aggregation and concurrent/subsequent deposition of nTiO2. Experiments were performed to examine nTiO2 aggregation and deposition onto quartz sand with co-present illite, kaolinite, and montmorillonite colloids under various geochemical conditions. Results showed that nTiO2 formed hetero-aggregates (i.e., nTiO2-clay aggregates) at low pH when nTiO2 and clay colloids carried opposite charges, and the hetero-aggregates may either deposit or remain suspended depending on their interactions with quartz sand and Fe/Al oxyhydroxide coatings. Deposition of nTiO2 and/or nTiO2-clay aggregates occurred as a result of electrostatic attraction, secondary minimum, and potentially Mg2+ bridging. Humic acid prevented nTiO2 aggregation and deposition under most conditions. In MgCl2 solutions, however, it facilitated deposition by adsorbing to nTiO2 and Fe/Al oxyhydroxides, thereby enabling Mg2+ bridging. This study demonstrated the important and complex roles of pH, DOM, cation valence, and clay colloids in controlling aggregation and subsequent deposition of nTiO2.

31478. 题目: Identifying localized and scale-specific multivariate controls of soil organic matter variations using multiple wavelet coherence
文章编号: N18062404
期刊: Science of The Total Environment
作者: Ruiying Zhao, Asim Biswas, Yin Zhou, Yue Zhou, Zhou Shi, Hongyi Li
更新时间: 2018-06-24
摘要: Environmental factors have shown localized and scale-dependent controls over soil organic matter (SOM) distribution in the landscape. Previous studies have explored the relationships between SOM and individual controlling factors; however, few studies have indicated the combined control from multiple environmental factors. In this study, we compared the localized and scale-dependent univariate and multivariate controls of SOM along two long transects (northeast, NE transect and north, N transect) from China. Bivariate wavelet coherence (BWC) between SOM and individual factors and multiple wavelet coherence (MWC) between SOM and factor combinations were calculated. Average wavelet coherence (AWC) and percent area of significant coherence (PASC) were used to assess the relative dominance of individual and a combination of factors to explain SOM variations at different scales and locations. The results showed that (in BWC analysis) mean annual temperature (MAT) with the largest AWC (0.39) and PASC (16.23%) was the dominant factor in explaining SOM variations along the NE transect. The topographic wetness index (TWI) was the dominant factor (AWC = 0.39 and PASC = 20.80%) along the N transect. MWC identified the combination of Slope, net primary production (NPP) and mean annual precipitation (MAP) as the most important combination in explaining SOM variations along the NE transect with a significant increase in AWC and PASC at different scales and locations (e.g. AWC = 0.91 and PASC = 58.03% at all scales). The combination of TWI, NPP and normalized difference vegetation index (NDVI) was the most influential along the N transect (AWC = 0.83 and PASC = 32.68% at all scales). The results indicated that the combined controls of environmental factors on SOM variations at different scales and locations in a large area can be identified by MWC. This is promising for a better understanding of the multivariate controls in SOM variations at larger spatial scales and may improve the capability of digital soil mapping.
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31479. 题目: Identifying the reducing capacity of biomass derived hydrochar with different post-treatment methods
文章编号: N18062403
期刊: Science of The Total Environment
作者: Yan Yan, Xianlong Ma, Weimin Cao, Xiaolei Zhang, Jizhi Zhou, Qiang Liu, Guangren Qian
更新时间: 2018-06-24
摘要: In this study, hydrochar was prepared from wheat straw (WS) and Spartina alterniflora (SA) biomass by hydrothermal carbonization, and further treated with HCl and NaOH washing, HNO3 oxidization and low temperature thermal heating. The reducing capacity (RC) of sample was quantified by I2 titration to explore how these modification methods affected the redox properties of hydrochar. The results indicated HNO3 and thermal oxidization increased the RC of hydrochar by 2–5 folds while NaOH washing had the negative effect on samples' RC. By analyzing the excitation-emission matrix (EEM) fluorescence of alkaline extraction solution of sample, humic acid like substances generated from various methods were identified as one of the major sources for electron donating. HNO3 oxidization could significantly increase the RC in hydrochar, which was likely resulting from the generation of alkali-soluble small molecule organic compounds. However, excessive oxidation by nitric acid with prolonged duration led to the gradual decrease in hydrochar's RC. Heating treatment caused a significant increase in the content of redox-active oxygen-containing functional groups and persistent free radicals (PFRs) in hydrochar. Even though both could donate electrons in the redox reaction with I2, the former was considered a greater contributor for the RC of hydrochar. From this study, the origin of RC of hydrochar can be identified as: oxygen-containing functionality, humic-like matter and PFRs. By employing different modification methods, the RC of hydrochar could be tuned by regulating the above sources. This study provided fundamental knowledges and simple routes to manipulate the redox properties of hydrochar for different environmental applications.
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31480. 题目: Responses of microbial carbon metabolism and function diversity induced by complex fungal enzymes in lignocellulosic waste composting
文章编号: N18062402
期刊: Science of The Total Environment
作者: Zhuotong Zeng, Xueying Guo, Piao Xu, Rong Xiao, Danlian Huang, Xiaomin Gong, Min Cheng, Huan Yi, Tao Li, Guangming Zeng
更新时间: 2018-06-24
摘要: Composting is an economic and effective technology for solid waste treatment, which is an essential method to promote the biogeochemical cycle of contaminants. However, the application of this technology was limited by the bio-degradative recalcitrance of lignin and other kind of phytotoxic substances release. The combination with microorganisms and enzymes is a popular and efficient way to enhanced composting. This study, referring to metabolic mechanisms, fungal molecular and biogeochemical cycles, was performed to investigate the effects of lignin degradation, carbon metabolic diversity, as well as the related changes induced by these two kinds of complex enzymes in composting. The biological diversity is important indicator in ecosystem, which concerns the environmental applicability of one technology. The carbon metabolism diversity reflected the biogeochemical cycles of organic matter, which was also an essential input to analyze the effects of composting. The changes on the diversity characteristics of carbon are essential to comprehensively understand the deep mechanisms of this process, and extended the application of complex enzymes in the field of enhanced composting. The analysis of Biolog revealed that the utilization of pyruvic acid methyl ester, α-Cyclodextrin, d-Mannitol, d-Galacturonic, Itaconic acid and l-asparagine were deeply promoted, and that of d, l-α-Glycerol-phosphate, l-Threonine, Glycyl-l-Glutamic acid and putrescine were depressed by adding the complex enzyme in composting. Moreover, according to the data, the addition of complex enzymes improved the degradation efficiency and the metabolic capacity of carbon in composting. These findings undoubtedly contribute to the development of enzyme-based technologies and the applications of complex enzymes in composting, which is of great benefit to eliminate the limitation and extend the application of composting.
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