Microbial immobilisation and turnover of N labelled substrates in two arable soils under field and laboratory conditions

Microbial biomass N dynamics were studied under field and laboratory conditions in soils of high yield (HY) and low yield (LY) areas in an agricultural field. The objective of the study was to determine the size and activity of soil microbial biomass in the soils of the different yield areas and to compare these data obtained under field and laboratory conditions. Soils were amended with ¹⁵N labelled mustard (Sinapis alba) residues (both experiments) and labelled nitrate (laboratory only) at 30 μg N g⁻¹ dry soil. Soil microbial biomass (SMB) N, mineral N (N_min) and total N content was monitored both in the field and in the laboratory. N₂O efflux was additionally measured in laboratory treatments. Isotope ratios were determined for SMB in both experiments, for all other parameters only in the laboratory treatments. In the laboratory less amounts of added substrate N were immobilised by the SMB in HY soils compared to LY soils, whereas in the field immobilisation of added N by SMB was higher in HY soils initially and slightly lower after 40 days of incubation. Calculated turnover times in the laboratory nitrate, laboratory mustard and field mustard amendments were 0.18, 0.27 and 0.74 years (HY) and 0.22, 0.61 and 1.01 years (LY), respectively. The turnover times of added substrate N always showed the trend to be faster in HY soils compared to LY soils. A faster turnover of nutrients in the HY soils may involve a better nutrient supply of the plants, which coincides with the higher agricultural yield observed in these areas.     

Impacts of anthropogenic N additions on nitrogen mineralization from plant litter in exotic annual grasslands

Urban regions of southern California receive up to 45 kg N ha^-1 y^-1 from nitrogen (N) deposition. A field decomposition study was done using ¹⁵N-labelled litter of the widespread exotic annual grass Bromus diandrus to determine whether elevated soil N is strictly from N deposition or whether N mineralization rates from litter are also increased under N deposition. Tissue N and lignin concentrations, which are inversely related in field sites with high and low N deposition, determine the rate at which N moves from plant litter to soil and becomes available to plants. The effect of soil N on N movement from litter to soil was tested by placing litter on high and low N soil in a factorial experiment with two levels of litter N and two levels of soil N. The litter quality changes associated with N deposition resulted in faster rates of N cycling from litter to soil. Concentrations of litter-derived N in total N, NH₄⁺, NO₃⁻, microbial N and organic N were all higher from high N/low lignin litter than from low N/high lignin litter. Litter contributed more N to soil NH₄⁺ and microbial N in high N than low N soil. At the end of the study, N mineralized from high N litter on high N soil accounted for 46% of soil NH₄⁺ and 11% of soil NO₃⁻, compared to 35% of soil NH₄⁺ and 6% of soil NO₃⁻ from low N litter on low N soil. The study showed that in high N deposition areas, elevated inorganic soil N concentrations at the end of the summer N deposition season are a result of N mineralized from plant litter as well as from N deposition.     

稻米中同位素与多元素特征及其产地溯源PCA-LDA判别

通过探究谷物中同位素与多元素的地域特色及其产地溯源的可能性,本研究采用稳定同位素质谱和等离子发射光谱质谱法测定稻米中同位素比率和多元素含量,并结合化学计量学中主成分分析(PCA)和线性判别分析(LDA)法建立模型,对不同省份的稻米进行产地溯源判定。结果表明,各地产的稻米中稳定同位素δ15N、δ13C、δD、δ18O数值范围不同,而且Li、Be和Na等其他矿物元素的含量变化较大,Pb、Sr同位素比率也各不相同,具有一定的地域特征。PCA法能够初步辨别各稻米地产,本研究进一步采用PCA-LDA法能够对大区域(黑龙江省、江苏省和辽宁省)的稻米进行产地判别,通过对23个样本进行判别验证,正确率为91%。对于黑龙江省4个地产的稻米样品,由于地理差异性比较小,同时样本数比较少,故只对其中2个产地稻米进行判别。通过同位素比率和多元素的含量的测定再结合化学计量学分析,一定程度上能够区分不同产地的稻米,为稻米产地溯源的可行性提供了方法依据。     

Subsoil retention of organic and inorganic nitrogen in a Brazilian savanna Oxisol

Abstract. Nitrogen (N) loss by leaching poses great challenges for N availability to crops as well as nitrate pollution of groundwater. Few studies address this issue with respect to the role of the subsoil in the deep and highly weathered savanna soils of the tropics, which exhibit different adsorption and drainage patterns to soils in temperate environments. In an Anionic Acrustox of the Brazilian savanna, the Cerrado, dynamics and budgets of applied N were studied in organic and inorganic soil pools of two maize (Zea mays L.) – soybean (Glycine max (L.) Merr.) rotations using ¹⁵N tracing. Labelled ammonium sulphate was applied at 10 kg N ha^?1 (with 10 atom%¹⁵N excess) to both maize and soybean at the beginning of the cropping season. Amounts and isotopic composition of N were determined in above‐ground biomass, soil, adsorbed mineral N, and in soil solution at 0.15, 0.3, 0.8, 1.2 and 2 m depths using suction lysimeters throughout one cropping season. The applied ammonium was rapidly nitrified or immobilized in soil organic matter, and recovery of applied ammonium in soil 2 weeks after application was negligible. Large amounts of nitrate were adsorbed in the subsoil (150–300 kg NO₃^?‐N ha^?1 per 2 m) matching total N uptake by the crops (130–400 kg N ha^?1). Throughout one cropping season, more applied N (49–77%; determined by ¹⁵N tracers) was immobilized in soil organic matter than was present as adsorbed nitrate (2–3%). Most of the applied N (71–96% of ¹⁵N recovery) was found in the subsoil at 0.15–2 m depth. This coincided with an increase with depth of dissolved organic N as a proportion of total dissolved N (39–63%). Hydrophilic organic N was the dominant fraction of dissolved organic N and was, together with nitrate, the most important carrier for applied N. Most of this N (>80%) was leached from the topsoil (0–0.15 m) during the first 30 days after application. Subsoil N retention as both adsorbed inorganic N, and especially soil organic N, was found to be of great importance in determining N losses, soil N depletion and the potential of nitrate contamination of groundwater.     

稳定同位素技术鉴别库尔勒香梨产地可行性研究

为开展碳、氮、氢、氧(C、H、O、N)稳定同位素鉴别库尔勒香梨产地的可行性研究,明确新疆库尔勒香梨δ¹³C、δ¹⁵N、δ²H、δ¹⁸O值,本研究以甘肃香梨和陕西红香酥梨作为对照,采用稳定同位素比值质谱仪(IRMS)分析新疆库尔勒香梨与对照样品的δ¹³C、δ¹⁵N、δ²H、δ¹⁸O值,并采用正交校正的偏最小二乘判别分析(OPLS-DA) 鉴别新疆库尔勒香梨产地真实性。结果表明,新疆、甘肃两个产区香梨与陕西产区红香酥梨的δ¹³C、δ¹⁵N、δ²H、δ¹⁸O值存在显著差异(P<0.05)。新疆产区的66份库尔勒香梨判别准确率为95.45%;甘肃产区的20份香梨样品判别准确率为60%;陕西产区的23份红香酥梨样品判别准确率为95.65%。C、N、H、O 4种稳定同位素可有效鉴别新疆库尔勒香梨和陕西红香酥梨,但在新疆库尔勒香梨与甘肃香梨鉴别方面,误判率较高,如果能结合其他鉴别技术,则有可能出现较好的鉴别效果。本研究为库尔勒香梨产地真实性鉴别提供了科学依据。     

久效磷在环境中的行为与归趋

运用同位素示踪技术研究了久效磷在农业生态环境中的行为。结果表明,久效磷进入生态环境后将降解为可溶态和结合态残留物;土壤微生物能显著地加速久效磷的降解与消失;在水灌农作物及水生生态系中,久效磷在水中消失较快,易被系统内动植物吸收;久效磷用于水稻,一次喷药0.45kg/hm~2,间隔31天,糙米中的残留浓度低于最大残留限量,若二次、三次用药,则安全间隔期为52天和67天。久效磷在所论各系统中的可溶态降解物主要为磷酸三酯。     

Colour Dilution Alopecia in Doberman Pinschers with Blue or Fawn Coat Colours: A Study on the Incidence and Histopathology of this Disorder

Abstract— A population of 57 blue or fawn Doberman Pinschers was studied to determine the incidence of colour dilution alopecia in this breed. Forty two dogs had hair loss, typical of colour dilution alopecia. The diagnosis was confirmed in 11 dogs by skin biopsy and in 6 dogs by light microscopic examination of plucked hairs. Key diagnostic features included large macromelanosomes in the hair shafts, free clumps of melanin in the lumens of hair follicles, and numerous perifollicular melanophages. An hypothesis on the pathogenesis of colour dilution alopecia is proposed. Résumé— Une population de 57 Pinschers à robe bleue ou feu a étéétudiée pour déterminer la fréquence de l'alopécie par dilution de couleur dans cette race. 42 chiens ont présenté une perte de poils caractéristique de l'alopécie par dilution de couleur. Le diagnostic a été confirmé chez 11 chiens par biopsie cutanée et chez 6 chiens par l'examen au microscope optique des poils épilés. Les caractéristiques diagnostiques comprennent la présence de grands macromélanosomes dans les racines des poils, de manchons libres de mélanine dans la lumière des follicules pileux et de nombreux mélanophages périfolliculaires. Une hyhpothèse sur la pathogénie de l'alopécie par dilution de couleur est proposée. Zusammenfassung— Untersucht wurden 57 blaue und rehfarbene Dobermänner, um das Vorkommen der Farbmutanten-Alopezie bei dieser Rasse feststellen zu können. 42 dieser Hunde zeigten den für diese Erkrankung typischen Haarausfall. Bei 11 Patienten wurde die Diagnose durch Hautbiopsie und bei 6 durch lichtmikroskopische Untersuchung von ausgezupften Haaren gesichert. Die charakteristichen Bilder waren Makromelanosome in den Haarschäften, freies zusammengeballtes Melanin im Lumen der Haarfollikel und zahlreiche perifollikuläre Melanophagen. Eine Hypothese für die Pathogenese dieser Erkrankung wird aufgestellt. Resumen Se estudió una población de 57 perros de raza Doberman y color gris o azul para determinar la incidencia de la alopecia por dilución de color en esta raza. 42 perros presentaban pérdidas de pelo típicas de la alopecia por dilución de color. En 11 perros el diagnóstico se confirmó mediante biopsia y en 6 mediante examen microscópico del pelo. Las características diagnósticas de este proceso consistían en la presencia de macromelanosomas en las vainas de los pelos, y en la presencia de acúmulos de melanina libre en el interior de los folículos pilosos y de melanófagos perifoliculares. Se propone una hipótesis sobre la patogenia de esta enfermedad.     

南海北部冬季和夏季浮游哲水蚤类群落

在2015年夏季和冬季开展了南海北部海域不同粒级浮游动物碳稳定同位素特征的研究。按照浮游动物粒径大小将其分成3个类群：小型(180~380 μm)、中型(380~500 μm)和大型(>500 μm)。研究结果表明,浮游动物δ¹³C值空间分布差异明显,夏季浮游动物δ¹³C值变化范围为–24.19~ –19.57,小型和中型浮游动物δ¹³C值的高值均分布在研究海域南部;冬季浮游动物δ¹³C值变化范围为–23.89~ –19.69,空间分布特征与夏季相反。浮游动物δ¹³C值未表现出显著的季节和粒径结构差异。各粒级浮游动物δ¹³C值与叶绿素a平均浓度的对数值均呈显著的正相关,而与浮游动物生物量相关性不明显。     

气候变化下的塔里木盆地西南部内陆河流域径流组分特征分析

气候变化对中亚高山区水循环影响显著,加剧了区域水资源供需矛盾.认识区域内陆河径流组分特征对于水资源管理具有重要意义.基于塔里木盆地西南部提孜那甫河流域过去60a(1957-2016年)的气象、径流数据,分析了区域气候变化特征及径流组分的响应.结果 表明:(1)过去60 a来,流域气温及山区降水呈现出明显的上升趋势,自2...