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31421. 题目: Evaluating the response of conventional and water harvesting farms to environmental variables using remote sensing
文章编号: N18062556
期刊: Agriculture, Ecosystems & Environment
作者: Brent J. Lloyd, Philip E. Dennison
更新时间: 2018-06-25
摘要: The majority of people in Sub-Saharan Africa (SSA) live in rural communities and practice subsistence farming. Variations in climate and other environmental factors affect the stability of local food production. This instability makes the adoption of efficient farming techniques critical in helping farmers achieve food, income, and livelihood security. Agricultural water conservation techniques called water harvesting are being implemented to increase crop yields in SSA. These techniques have been shown to increase water productivity, nutrients, and organic matter in the soil. This paper uses high-resolution imagery to identify and differentiate between farms using conventional and water-harvesting farm methods. An ordinary least-squares regression model was used to correlate seasonal maximum normalized difference vegetation index (NDVI) values with environmental factors for the different farming methods. The results suggest that water harvesting farm techniques have higher crop yields and are less dependent on precipitation than conventional farming methods. The methodology presented in this paper can be used to map use of water harvesting over large areas and monitor associated differences in productivity.

31422. 题目: Organic management and cover crop species steer soil microbial community structure and functionality along with soil organic matter properties
文章编号: N18062555
期刊: Agriculture, Ecosystems & Environment
作者: Laura B. Martínez-García, Gerard Korthals, Lijbert Brussaard, Helene Bracht J?rgensen, Gerlinde B. De Deyn
更新时间: 2018-06-25
摘要: It is well recognized that organic soil management stimulates bacterial biomass and activity and that including cover crops in the rotation increases soil organic matter (SOM). Yet, to date the relative impact of different cover crop species and organic vs. non-organic soil management on soil bacteria and fungi and on SOM quantity and quality remains to be tested. We used a long-term (10 years) full-factorial field experiment to test the combined effects of organic vs. conventional soil management with different cover crop species (oat or rye) and the legacy effects of seven soil health treatments (SHTs: treatments with compost, chitin, marigold, grass–clover, biofumigation or anaerobic soil disinfestation (ASD), and fallow as control) on microbial community biomass, structure and catabolic activity and on SOM quantity and quality (dissolved organic carbon (DOC), aromaticity and water repellency). Microbial community traits were assessed using PLFA/NLFA analyses and multi-substrate induced respiration. We found that organic soil management enhanced total microbial biomass by increasing bacterial, saprotrophic and arbuscular mycorrhizal fungal biomass; and increased total microbial catabolic activity, associated with maintaining high microbial efficiency (low qCO2). Effects of organic management were amplified by oat as cover crop, which enhanced the abundance of saprotrophic fungi resulting in a higher fungal:bacterial ratio. Total SOM concentration was similar among treatments, however the most easily accessible fraction, i.e. DOC, was higher in organic compared to conventional soils. Also, the aromaticity of the DOC was lower in organic than in conventional systems, which was associated with lower water repellency. There was a legacy effect of SHTs on fungal:bacterial ratio in that chitin and marigold showed higher fungal:bacterial ratio compared to compost, biofumigation and ASD even 6 years after the last application. We conclude that organic soil management enhances the abundance of all microbial groups and their total catabolic activity, associated with a higher concentration and lower aromaticity of dissolved organic matter. These effects can be enlarged by the growth of specific cover crops and the application of certain soil health treatments.

31423. 题目: Why does mineral fertilization increase soil carbon stocks in temperate grasslands?
文章编号: N18062554
期刊: Agriculture, Ecosystems & Environment
作者: Christopher Poeplau, Dorit Zopf, B?rbel Greiner, Rob Geerts, Hein Korvaar, Ulrich Thumm, Axel Don, Arne Heidkamp, Heinz Flessa
更新时间: 2018-06-25
摘要: Globally, grasslands are a major land cover type and store significant amounts of soil organic carbon (SOC). Fertilization with the major plant nutrients nitrogen (N), phosphorus (P), and potassium (K) may affect SOC stocks, e.g., by altering aboveground and belowground plant productivity, species composition, litter composition and decomposition, and microbial metabolism. However, belowground responses to fertilization in grasslands are not fully understood, hampering accurate predictions of SOC dynamics. In this study, seven different long-term grassland fertilization experiments (16–58 years) in Germany and the Netherlands were sampled to determine the effects of mineral fertilization (i.e., N, P, K, PK, and NPK) compared with unfertilized plots (Control) on SOC stocks and root C stocks. Soils were sampled to a depth of 100 cm or to the maximum depth possible. Potential litter decomposition was assessed using Lipton Rooibos and Lipton Green teas as standardized and well-characterized litter materials. In the topsoil (0–30 cm depth), PK, NPK, and NPK+ (increased NPK) fertilization had significant positive effects on SOC stocks, with annual sequestration rates of 0.28, 0.13, and 0.37 Mg ha 1 yr 1, respectively, within an average time span of 34 (PK, NPK) or 20 (NPK+) years. For NPK fertilization, 1.15 kg of N was needed to sequester 1 kg SOC. Increased SOC stocks could not be explained by altered belowground C inputs or decomposition rates, since root C stocks were not affected by fertilization and potential litter decomposition was unchanged. The highly significant increases in dry matter yield with PK and NPK fertilization and resulting higher aboveground C inputs were also unlikely to explain the observed SOC stock changes, since increases were only observed at soil depths >10 cm. However, significantly narrower root C:N ratios were observed for the N (26.9), PK (36.5), NPK (36.8), and NPK+ (33.2) treatments than for the Control (41.8), which may have caused increased microbial C use efficiency, positively affecting SOC storage. The narrower C:N ratios in PK treatments were explained by significantly increased abundance of legumes. We concluded that the carbon footprint of fertilization-induced SOC sequestration needs to be considered when the latter should be accounted for as a climate mitigation measure. Thereby, PK fertilization has much lower CO2 costs than NPK fertilization due to N input via legumes.

31424. 题目: Cell membrane characteristics and microbial population distribution of MBBR and IFAS with different dissolved oxygen concentration
文章编号: N18062553
期刊: Bioresource Technology
作者: Si-jia Ma, Li-li Ding, Hai-dong Hu, Hai-jun Ma, Ke Xu, Hui Huang, Jin-ju Geng, Hong-qiang Ren
更新时间: 2018-06-25
摘要: This paper investigated the influences of different dissolved oxygen (DO) concentration (0.71–1.32, 2.13–3.02 and 4.31–5.16 mg/L) on cell membrane characteristics and microbial population distribution of moving biofilm reactors. Two representative reactors, i.e., moving bed biofilm reactors and integrated fixed-film activated sludge were operated. Results indicated that both DO concentration of 0.71–1.32 mg/L and 4.31–5.16 mg/L could increase membrane lipid mobile fraction (49.4%-67.4%) of the microbes, however, through prompting the synthesis of branched fatty acids and unsaturated fatty acids, respectively. For the biofilms, the abundance of Bacteroidetes decreased and Actinobacteria increased with the increase of DO levels. The lowest EfOM content and the highest microbial diversities (1.14–1.52) was observed at DO of 2.13–3.02 mg/L. Redundancy analysis showed that changes of DO levels could alter cell membrane properties and bacterial community structures, and subsequently significantly influenced effluent organic matter composition of moving biofilm reactors.

31425. 题目: Effect of CaO2 addition on anaerobic digestion of waste activated sludge at different temperatures and the promotion of valuable carbon source production under ambient condition
文章编号: N18062552
期刊: Bioresource Technology
作者: Qian Ping, Xiao Lu, Ming Zheng, Yongmei Li
更新时间: 2018-06-25
摘要: The effect of calcium peroxide (CaO2) addition on anaerobic digestion (AD) of waste activated sludge (WAS) at different temperatures (20 °C, 35 °C, and 55 °C) were investigated. The results show that CaO2 addition had significant positive effect on short-chain fatty acids (SCFAs) production under ambient and mesophilic conditions. Polysaccharides and proteins embedded in extracellular polymeric substances (EPS) were effectively released from inner fraction to outer fraction, and non-biodegradable humic-like substances were decreased while easily biodegradable tryptophan-like proteins increased. These effects were most remarkable under ambient conditions. However, CaO2 addition was unfavorable to thermophilic AD because of high free ammonia concentrations and the accumulation of humic-like substances. Temperature showed a stronger effect than CaO2 on microbial community structure, but CaO2 addition was more effective than temperature in enhancing hydrolytic and acidifying microorganisms. Predictive functional profiling indicated that microbial hydrolysis, metabolism and acidification were promoted by CaO2 under ambient conditions.

31426. 题目: Highly efficient of nitrogen removal from mature landfill leachate using a combined DN-PN-Anammox process with a dual recycling system
文章编号: N18062551
期刊: Bioresource Technology
作者: Xiang Li, Yan Yuan, Fan Wang, Yong Huang, Qing-tan Qiu, Yuan Yi, Zhen Bi
更新时间: 2018-06-25
摘要: An efficient and stable combined denitrification-partial nitrification-Anammox process with a dual recycling system was used to remove nitrogen from mature landfill leachate. After 155 d of operation, the NO3 as the PN-Anammox byproduct was almost treated with biodegradable organic carbon in raw wastewater in a pre-denitrification reactor by external recycling system. When raw landfill leachate with NH4 +-N concentration of 1900 mg/L was treated, an integrated reactor with airlift recycling was combined with the PN and Anammox reactions to efficiently remove NH4 + from the inflow. The total nitrogen concentration of effluent stabilized at 20 mg/L and total nitrogen removal efficiency was 99%. The maximum NO2 production rate in the aerobic zone was 2.2 kg/(m3·d) and the maximum nitrogen removal rate in the anaerobic zone was 21.4 kg/(m3·d). The most common phyla among the nitrification and the Anammox functional bacteria were Nitrosomonas, Candidatus Kuenenia, and Candidatus Brocadia after landfill leachate treatment.

31427. 题目: Strategies and relative mechanisms to attenuate the bioaccumulation and biotoxicity of ceria nanoparticles in wastewater biofilms
文章编号: N18062550
期刊: Bioresource Technology
作者: Yi Xu, Chao Wang, Jun Hou, Peifang Wang, Lingzhan Miao, Guoxiang You
更新时间: 2018-06-25
摘要: Inhibitory effects of ceria nanoparticles (CeO2 NPs) on biofilm were investigated individually and in combination with phosphate (P), ethylene diamine tetraacetic acid (EDTA), humic acid (HA) and citrate (CA) to further explore the toxicity alleviating solutions. Exposure to 20 mg/L CeO2 NPs significantly decreased the performance of biofilm in nutrients removal. Distribution experiments suggested >98% of the CeO2 NPs retained in microbial aggregates, leading to 51.26 μg/L Ce ions dissolution. The dissolved CeIV and its further being reduced to CeIII stimulated the formation of O2 and OH, which increased lipid peroxidation level to 130.93% in biofilms. However, P/EDTA/CA captured or precipitated Ce ions, whereas EDTA/HA/CA shielded NPs-bacteria direct contacts, both disturbing the NPs adsorption, intercepting the redox transition between CeIV and CeIII, reducing the generation of O2 and OH, thus mitigating the toxicity of CeO2 NPs. These results illustrate the main drivers of CeO2 NPs biotoxicity and provide safer-by-design strategies.

31428. 题目: The characteristic evolution of soluble microbial product and its effects on membrane fouling during the development of sponge membrane bioreactor coupled with fiber bundle anoxic bio-filter for treating saline wastewater
文章编号: N18062549
期刊: Bioresource Technology
作者: Zhipeng Li, Weilong Song, Feng Liu, Yi Ding, Hong You, Hengjun Liu, Peishi Qi, Chao Jin
更新时间: 2018-06-25
摘要: Membrane fouling mitigation was observed during the development of novel sponge membrane bioreactor coupled with fiber bundle anoxic bio-filter (AF-MBMBR). Soluble microbial product (SMP) was found to be positively correlated with membrane fouling. To further clarify the mechanism of fouling mitigation, the effects of bio-carriers (sponge and fiber bundles) on characteristics and fouling potential of SMP were investigated. Characterization of SMP implied that as a consequence of employing bio-carriers, tyrosine and tryptophan in SMP significantly decreased, instead relative proportions of humic and fulvic acids increased. Meanwhile, batch filtration tests demonstrated that fouling potential of SMP was significantly alleviated, flux decline caused by filtrating SMP decreased from 84.5% to 60.1%. Further analysis on foulants and filtrate revealed that proteins performed high adhesion propensity on membrane while humic and fulvic acids mainly can pass through the membrane; this finding could well explain the mitigation of SMP fouling potential induced by bio-carriers.

31429. 题目: Effects of different management approaches on soil carbon dynamics in Moso bamboo forest ecosystems
文章编号: N18062548
期刊: CATENA
作者: Chong Li, Yongjun Shi, Guomo Zhou, Yufeng Zhou, Lin Xu, Liang Tong, Xiang Liu
更新时间: 2018-06-25
摘要: Moso bamboo (Phyllostachys pubescens) is a very important forest resource in subtropical China, and it has excellent carbon sequestration potential, and can play an important role in mitigating climate change. The international community has gradually recognized the benefits of Reducing Emissions from Deforestation and Forest Degradation (REDD+) forest carbon sequestration mechanisms, and the areas available for the development of forest carbon sinks have greatly expanded. Therefore, in this study, we use a two-factor randomized complete block design in which fertilization rate and harvesting intensity were selected to investigate the changes in soil organic carbon (SOC) concentration and carbon (C) storage from 2010 to 2016. With 3k orthogonal method, a factorial analysis with 3 levels of fertilization (high (1800), medium (900) and low (0 kg ha 1 year 1)) and 3 levels of harvesting intensity (high (100%), medium (50%) and low (0%) cutting of the bamboo of 4–5 years old) has been taken. Our results show that fertilization, harvesting, and the fertilization × harvesting interaction had significant effects on SOC concentration changes, but not on C storage after six years of management. Only the interaction between high fertilization and high intensity harvesting, which we called the intensive management model, caused a decrease of 4.48 Mg C ha 1 in the 0–50 cm soil layer C storage. The interaction between no fertilization and low intensity harvesting, which we called the traditional management model, increased soil carbon C by 7.90 Mg C ha 1. The optimized management model of high fertilization and medium intensity harvesting increased soil C the most; by 59.94 Mg C ha 1, which is 2.36 times larger than that of the intensive management model, and 1.86 times larger than that of the traditional management model. The results clearly reveal that the soil carbon pools in Moso bamboo forest have a great carbon sequestration potential under the optimized management model.

31430. 题目: Effects of snowfall depth on soil physical–chemical properties and soil microbial biomass in moss–dominated crusts in the Gurbantunggut Desert, Northern China
文章编号: N18062547
期刊: CATENA
作者: Ruiming Zhao, Rong Hui, Lichao Liu, Min Xie, Lizhe An
更新时间: 2018-06-25
摘要: Winter snowfall is an important source of moisture that may influence the growth and development of biological soil crusts (BSCs) in temperate desert regions of China. Yet there is still limited empirical knowledge about the effect of snowfall on BSCs. In this study, moss crusts from the Gurbantunggut Desert were exposed to five snow depths to evaluate how snowfall affected the physical–chemical properties (pH; electric conductivity, EC; soil organic carbon, SOC; total nitrogen, TN; available nitrogen, AN; available phosphorus, AP; available potassium, AK) and microbial biomass (soil microbial biomass carbon, SMBC; soil microbial biomass nitrogen, SMBN; soil microbial biomass phosphorus, SMBP) of soil in the BSCs, before (in October 2016: representing three consecutive years of snow manipulation) and after winter (in April 2017). Results showed that the soil water content increased significantly as snowfall depth increased (p < 0.05) in October 2016 and April 2017. Most of the soil physical–chemical features (EC, SOC, TN, AN, AP, and AK) and microbial biomass (SMBC and SMBN) showed an increase with an increase of snowfall depth after three consecutive years of snow manipulation. Moreover, for most experimental treatments, after a winter of melting snow (in April 2017) most of the soil properties were significantly higher (p < 0.05) than found in October 2016. Together, these results showed that the dynamics of soil nutrients and microbial biomass in moss BSCs were affected by snowfall depth in Gurbantunggut Desert. Different snowfall depths can have different effects on the dynamics of soil nutrients and microbial biomass of moss crusts, an impact that may alter the future growth and development of BSCs. Thus, we suggest that the potential influence of snowfall depth on soil nutrients and microbial biomass dynamics in BSCs require consideration when discussing the effects of moisture on ecological functions of BSCs in arid and semi–arid regions.

31431. 题目: Geochemical fingerprint of insoluble material in soil on different limestone formations
文章编号: N18062546
期刊: CATENA
作者: Nina Zupan?i?, Rok Turni?ki, Milo? Miler, Helena Gr?man
更新时间: 2018-06-25
摘要: In the Karst region near Diva a, Slovenia, soils are developed on the limestone of three geological formations: Se ana, Lipica, and Liburnian. In each formation, six soil profiles were dug, limestone insoluble residua was obtained, and in Liburnian Formation interbedded material and material filling fractures and cavities was sampled. All soils have silty clay and silty-clayey loam texture, pH levels in the range 4.5–7.0, high organic matter content and saturation with basic cations over 50%. However, soils on the Se ana Formation are deeper and more evolved, and besides as Rendzic Phaeozem classify also as Eutric Cambisol. Their insoluble residuum is richest in mineral part. The profiles on the Lipica Formation are a Rendzic Phaeozem, and the shallowest soils on the Liburnian Formation are either a Rendzic Phaeozem or a Rendzic Leptosol. Additionally, the soils formed over the Lipica Formation are characterised by a greater portion of the small rock fragments (<200 g), due to its paleo-karstification. The insoluble residuum of all three formations is rich in organic matter and fine grained. The general soil chemistry is in accordance with highly weathered upper crustal material and, compared to insoluble residua indicates the contribution of material from an additional source. The analysis of variance demonstrated differences in redox-sensitive elements (Cr, Mo, Ni, U, V, and Y) between formations, which are inherited by the insoluble residua. The insoluble residua contributed material and left a specific geochemical fingerprint in the observed soils, but regarding texture and general geochemistry, non-carbonate material must have been added. The material that fills karst forms inside the limestone profile is similar to the soils, but not identical. Other interbedded and probably also eolian material contributed to the final mass.

31432. 题目: Greenhouse gas inventories: Deriving soil organic carbon change factors and assessing soil depth relevance in Argentinean Semiarid Chaco
文章编号: N18062545
期刊: CATENA
作者: Sebastián Horacio Villarino, Guillermo Alberto Studdert, Pedro Laterra
更新时间: 2018-06-25
摘要: Soil organic carbon (SOC) is the main terrestrial carbon (C) reservoir. Land use change has depleted SOC stocks and released large amounts of C dioxide (CO2). Thus, the development of reliable tools for SOC stock monitoring at large scale is fundamental to face climate change. Argentinean Semiarid Chaco (ASC) is a deforestation hotspot, but CO2 emissions from soil has been barely assessed. Deforested area was converted into cropland or grassland. We used empirical data to model SOC stocks under native forest (SOCref) and the RothC model to estimate SOC stock change factors under cropland (Fc) and grasslands (Fg) in the ASC. These SOCref's and stock change factors were applied in a Tier 2 (T2) C inventory, following the Intergovernmental Panel on Climate Change (IPCC) proposal. We used SOC vertical distribution models to estimate SOC stock at 0–100 cm soil depth from estimated SOC stocks at 0–30 cm, the default soil depth of IPCC C inventory method. The T2 was run for 1976 through 2012 and under three hypothetical land use change scenarios for 2012 through 2032. The scenarios were: i) land use change ceases, ii) land use change rate is the half of 1996–2012 land use change rate, and iii) land use change rate remains as in 1996–2012. Estimated average SOCref stock at 0–30 cm soil depth was 40 Mg C ha 1 and varied between 35 and 51 Mg C ha 1. Cropland was the main fate of deforested area and the land use with lower SOC stocks. Stock change factors and SOC stocks estimated with T2 were within the range of the empirical data reported in the ASC. However, research about SOC dynamics and land use change is incipient in the ASC and more empirical information is needed to validate T2 estimations. Deforestation in the ASC leads to high CO2 emissions from soil and the only scenario in which those emissions would be reduced is with deforestation cessation. Soil depth considered in greenhouse gas inventories is 0–30 cm, and this strongly underestimates CO2 emissions. We demonstrated that this limitation could be overcome by using SOC vertical distribution models to estimate deep SOC stock (up to 1 m) from estimated surface SOC stock. Hence, these models could be used to improve CO2 estimations from SOC inventories.

31433. 题目: Influence of wind erosion on dry aggregate size distribution and nutrients in three steppe soils in northern China
文章编号: N18062544
期刊: CATENA
作者: Yuchun Yan, Xu Wang, Zhenjie Guo, Jinqaing Chen, Xiaoping Xin, Dawei Xu, Ruirui Yan, Baorui Chen, Lijun Xu
更新时间: 2018-06-25
摘要: Wind erosion is a key process that causes soil degradation in the semiarid steppe regions of northern China. However, few studies have quantitatively measured the changes in dry aggregate distribution and nutrients in steppe soils under continuously varying wind erosion intensity. The objectives of this study were as follows: (1) to explore the different responses of three steppe soils to natural windblown treatments and (2) to quantify the changes in soil dry aggregate distribution, particle size distribution and soil nutrient contents under various wind erosion intensities for three steppe soils. We obtained samples of the following soils subjected to varying wind intensity via a natural windblown treatment: meadow steppe (MS), typical steppe (TS) and desert steppe (DS). Then, the physical and chemical properties of all soil samples were measured. The results showed that dry aggregate fractions <0.2 mm were selectively depleted by wind erosion and exhibited an exponential decrease in the residual soils with increasing wind erosion intensity. The organic carbon (OC), total nitrogen and available nitrogen in the three soils and the total phosphorous and available potassium in the TS and DS soils showed exponential decreases with increasing wind erosion intensity. The higher amounts of OC and nutrients were associated with fine dry aggregates (<0.2 mm), and fine dry aggregates were preferentially depleted by wind erosion, providing a mechanism for nutrient depletion caused by wind erosion. Finally, we established a comprehensive conceptual model of fine soil aggregate/particle depletion by wind erosion and subsequent nutrient depletion due to anthropogenic disturbances in temperate steppe areas.

31434. 题目: Integrating multi-source data to improve water erosion mapping in Tibet, China
文章编号: N18062543
期刊: CATENA
作者: Yuanyuan Yang, Ruiying Zhao, Zhou Shi, Raphael A. Viscarra Rossel, Dan Wan, Zongzheng Liang
更新时间: 2018-06-25
摘要: Quantitative estimation for soil erosion is necessary for protection of the environment, and to improve agricultural productivity. However, due to the large area, sparse and limited data in Tibet, soil erosion there is still poorly quantified. Here, we improved the factors of the Revised Universal Soil Loss Equation (RUSLE) and calculated water erosion in Tibet. Rainfall erosivity (R) was calculated with the 0.25°CPC Morphing technique (CMORPH) data and subsequently downscaled to 1-km spatial resolution using artificial neural network (ANN) based on environmental covariates; slope length and steepness (LS) was estimated using the 3 arc sec Shuttle Rader Topography Mission (SRTM) digital elevation model (DEM); cover management (C) and control practice (P) were assigned based on land cover and protection measurements; and soil erodibility (K) was calculated using the Environmental Policy Integrated Climate model (EPIC) with inputs of the contents of sand, silt, clay and organic carbon in soil samples from Tibet. We used the data-mining algorithm to model the K factor and the spatially referenced variables to generate a K factor map. The obtained factors were then used to calculate soil loss in Tibet at1-km resolution. Our study estimated the annual water erosion at5.43 t ha 1 y 1in Tibet, about5.44 × 108 t of soil lost yearly. The erosion rate increased from northwest to southeast, with most serious erosion occurring in the humid rain forest area in the southeast of Tibet. Our estimates of erosion area were generally consistent with previous national estimates. The largest differences were in the humid zone, Hengduan Mountain, and Yarlung Zangbo River basin, which are characterized by complex terrain and climate. Because of the applications of the best available data, we supply better, quantitative, finer spatial resolution estimates than previous studies. Our study is valuable for assessment of soil erosion in other data-scarce area suffering from soil loss by water erosion.

31435. 题目: Pedology of archaeological soils in tells of the Judean foothills, Israel
文章编号: N18062542
期刊: CATENA
作者: Danny Itkin, Onn Crouvi, H. Curtis Monger, Uri Shaanan, Haim Goldfus
更新时间: 2018-06-25
摘要: Tells (archaeological mounds) predominantly consist of poorly consolidated to unconsolidated sediments, and soils that are highly anthropogenic. This study examines pedogenic processes related to carbonate mobilization in tells in comparison with their peripheral soils (reference soil profiles). The key objective of this study is to test the hypothesis that tell deposits evolve through concurrent processes of sedimentation and pedogenesis (synlithogenic pedogenesis), and further explain it. Case studies are presented from three tells in semi-arid and Mediterranean climatic zones of the Levant. The methods applied included field survey, analyses of particle size distribution, pH, %CaCO3 and organic carbon content, and soil micromorphology. Soils of the tells contain miscellaneous cultural materials that derive mainly from degraded mud bricks, pottery and burnt wood. Chemical data show basic pH values, high CaCO3 content, and minor amounts of organic carbon. Field observations and lab analyses both indicate high similarity amongst the tells and their reference soil profiles. Buried tell soils show same characteristics as near-surface soils. However, the reference soil profiles show incipient horizonation, slightly darker colours, and more developed structure. Micromorphology of both the tells and the reference profiles show cohesively welded peds in a vughy microstructure, groundmass with an open porphyric c/f-related distribution, and discontinuous carbonate recrystallization. Relative rates of soil formation in the tells can be estimated when archaeological records are established. Contrary to the tells, the reference soil profiles show lower porosity and only minor remnants related to earth construction materials. We classify the soils of the studied tells as archaeological Calcareous Anthraltic Xerorthents. The correlative WRB classification would be Calcic Urbic Technosols (Archaic). The anthropogenic materials are as calcareous as the natural soils, but due to human action, carbonates in the tells are distributed differently. Based on these observations, ancient human actions and the dry climate have led to very little mobilization and accumulation of carbonates. The information provided in this study adds to the pedological understanding of archaeological environments. Specifically, it can be useful for the study of site formation processes of tells.

31436. 题目: The effectiveness of two contrasting mulch application rates to reduce post-fire erosion in a Portuguese eucalypt plantation
文章编号: N18062541
期刊: CATENA
作者: J.J. Keizer, F.C. Silva, D.C.S. Vieira, O. González-Pelayo, I. Campos, A.M.D. Vieira, S. Valente, S.A. Prats
更新时间: 2018-06-25
摘要: Wildfires are well-known to increase runoff and erosion during the initial stages of the window-of-disturbance, and mulching has been widely documented to effectively minimize this impact. However, the relationship between the rate of mulch application and erosion reduction is poorly studied, in spite of its potential importance for optimizing mulching costs and efforts per ha. Therefore, a field experiment was carried out in a recently burnt eucalypt plantation in Central Portugal that had been burnt by a moderate severity fire during August 2015, comparing sediment as well as organic matter losses from three untreated 2 m × 8 m erosion plots with losses from six plots mulched with eucalypt logging residues at two contrasting rates of either 2.6 or 8.0 Mg ha–1. The two mulching treatments resulted in the targeted litter covers of 50 and 79%, and these covers hardly changed over the ensuing year. Over this first post-fire year, the mulched plots produced significantly less mineral soil as well as organic matter losses than the untreated plots. At the same time, the plots with the high mulching rate lost consistently less sediments and organic matter than the plots with the low mulching rate but the differences were not statistically significant over all measurement periods. Total sediment losses over the first post-fire year were, on average, 86 and 96% lower following mulching at 2.6 and 8.0 Mg ha–1, respectively, than without mulching. In absolute values, total losses dropped from 8.0 to 1.1 and 0.3 Mg ha–1 y–1, respectively, or, in other words, similar to and well-below the widely-accepted threshold of tolerable soil loss of 1 Mg ha–1 y– 1. If this threshold value is acceptable to land managers, they could treat a three times larger area with the same amount of mulch.

31437. 题目: Water table drawdown reshapes soil physicochemical characteristics in Zoige peatlands
文章编号: N18062540
期刊: CATENA
作者: Liangfeng Liu, Huai Chen, Lin Jiang, Ji Hu, Wei Zhan, Yixin He, Dan Zhu, Qiuping Zhong, Gang Yang
更新时间: 2018-06-25
摘要: Warming and human activities have caused peatland degradation and water table drawdown, which greatly influence the physicochemical characteristics of soil at different depths. How water table drawdown affects soil physicochemical characteristics is not well understood for the Tibetan Plateau, especially the Zoige peatlands. This study measured variations in C/N ratio, ash content, δ13C, and humification index (HI) as a function of water table drawdown and depth by sampling 100-cm soil columns from three sites with different water tables in the Zoige peatlands. C/N ratio decreased while ash content and HI increased with water table drawdown, suggesting greater decomposition of soil organic matter at sites with a lower water table. The response of soil physicochemical characteristics to water table drawdown varied with depth: in the layer above the water table, C/N ratio did not vary, ash content decreased and HI increased; in the layer below the water table, C/N ratio and HI decreased, while ash content increased. The physicochemical characteristics above the water table were influenced mainly by new carbon input, while the characteristics below the water table were influenced mainly by decomposition. The depth profile of C/N ratio, ash content and HI aligned well with peat formation and decomposition and may be indicators of peat degradation. δ13C did not vary with water table drawdown, depth, or decomposition process. These insights into the variation of soil physicochemical characteristics with depths and water table may help elucidate the processes behind peatland degradation.

31438. 题目: Contrasting effects of organic and mineral nitrogen challenge the N-Mining Hypothesis for soil organic matter priming
文章编号: N18062539
期刊: Soil Biology and Biochemistry
作者: Kyle Mason-Jones, Niklas Schmücker, Yakov Kuzyakov
更新时间: 2018-06-25
摘要: Addition of easily available organic substances to soil often increases the CO2 efflux from pre-existing soil carbon (C). This phenomenon is often explained in terms of the Nitrogen (N)-Mining Hypothesis. According to this proposed – but never conclusively proven – mechanism, increased C availability induces N limitation in microbes, which then access N by degrading soil organic matter (SOM) – a priming effect. This is supported by some experiments demonstrating reduced CO2 efflux after mineral N addition. However, amino acids cause priming, despite their very low C:N ratios and rapid deamination to mineral N. To explore this contradiction, we applied 14C- and 15N-labelled C and N sources (glucose, alanine and ammonium sulfate) to rigorously test two key predictions of the N-Mining Hypothesis: (i) an amino acid should stimulate much less priming than glucose, and (ii) priming should be similarly suppressed for an amino acid or a stoichiometrically equivalent addition of glucose plus mineral N. Both of these key predictions of the N-Mining Hypothesis failed. Efflux of CO2 from native C was essentially determined by the type and amount of C added, with alanine stimulating more priming than glucose (16–50% cumulative increase relative to control, versus 0–25%, respectively). Higher C additions caused more priming than low additions. Mineral N reduced native-C-derived CO2 efflux when added alone or with organic substrates, but this effect was independent of the organic C additions and did not influence C-induced priming. These results were inconsistent with the hypothesized role of N mining in priming. We conclude that the N-Mining Hypothesis, at least in its current form, is not a universal explanation for observed priming phenomena. Instead, we observed a strong correlation between the rates of priming and the mineralization of the added substrates, especially during the first 8 days. This indicated that priming was best explained by energy-induced synthesis of SOM-degrading exoenzymes, possibly in combination with apparent priming from accelerated turnover of microbial biomass.

31439. 题目: Conversion of Tibetan grasslands to croplands decreases accumulation of microbially synthesized compounds in soil
文章编号: N18062538
期刊: Soil Biology and Biochemistry
作者: Zhen-Huan Guan, Xiao Gang Li, Lin Wang, Xiao Ming Mou, Yakov Kuzyakov
更新时间: 2018-06-25
摘要: Conversion of grassland to cropland affects microbial transformation of plant derived organic substances and the accumulation of microbially synthesized products in soil. We investigated long-term effects of agricultural use [more than 50 years' rotation with barley (Hordeum vulgare) and rapeseed (Brassica rapa)] after conversion from grasslands (grazed in the winter season) on the contents and composition of non-cellulose sugars and amino sugars in a broad range of soils on the Tibetan Plateau. Soils from two types of croplands (barley or rapeseed) were compared to a reference grassland soil by detailed analysis of plant vs. microbial and bacterial vs. fungal biomarkers. Long-term cultivation decreased total soil organic matter (SOM), light SOM and total non-cellulose sugar contents in the 0–20 cm soil by 27%, 47–72% and 57%, respectively, reflecting decreased root biomass compared to grassland. The ratios of (galactose + mannose)/(arabinose + xylose) and (rhamnose + fucose)/(arabinose + xylose) were both 26% smaller in cropland than in grassland soils, while the ratios of hemicelluloses in shoots or roots were similar between native and cultivated plants. Consequently, net transformation of plant substances to microbially synthesized polysaccharides decreased in cultivated soils. The total amino sugars (muramic acid, glucosamine, mannosamine, galactosamine) in cropland soils decreased by 42% as did their contribution to the SOM pool by 22%, compared to grassland soils, but the ratio of glucosamine/muramic acid in cropland soils doubled when compared to the grassland soil. This shows a strong decrease in microbial residue under cultivation, with the magnitude of the decrease greater in the bacterial than in the fungal components. All the above results from the intensively sampled site were confirmed in seven other sites featuring lower sampling intensity. We concluded that the conversion of grassland to cropland strongly decreases microbial transformation of plant residues and accumulation of the resulting microbial compounds – necromass – in soil (i.e., reduction of microbial input to stable SOM). The conversion also leads to a shift in the composition of microbial compounds towards a decreasing contribution of bacterial compared to fungal necromass.

31440. 题目: Depth-dependent response of soil aggregates and soil organic carbon content to long-term elevated CO2 in a temperate grassland soil
文章编号: N18062537
期刊: Soil Biology and Biochemistry
作者: L. Keidel, K. Lenhart, G. Moser, C. Müller
更新时间: 2018-06-25
摘要: Facing rising atmospheric CO2 concentrations, subsoils may play an important role in the global carbon (C) cycle due to the presence of unsaturated mineral surfaces. Further, macroaggregation is considered a crucial process influencing C sequestration. However, analyses on subsoil aggregation and C retention processes under long-term elevated CO2 (eCO2) are lacking. In this study we investigated the long-term effect of +20% above ambient CO2 concentration (corresponds to conditions reached 2035–2045) in a temperate grassland ecosystem at the Giessen Free Air CO2 Enrichment (Gi-FACE), Germany. A depth-dependent response of macroaggregation to eCO2 was observed: While in subsoil (15–45 cm depth) macroaggregation increased under eCO2, no CO2 induced change in macroaggregation was detected in topsoil (0–15 cm). Increased macroaggregation in subsoil coincided with higher SOC content of large macroaggregates (LM). Mean residence time (MRT) of SOC in aggregate-size classes were not different among each other under eCO2. However, macroaggregates and bulk soil differed in their MRT between soil depths. Despite increased macroaggregation and an estimated high SOC sequestration potential in subsoil we could not observe an increase in SOC content of bulk soil.