寒旱灌区冻融期冬小麦不同覆盖条件土壤温度变化

为揭示冻融期冬小麦不同覆盖条件土壤温度变化规律,基于河套灌区冬小麦地膜覆盖、秸秆覆盖和无覆盖3个试验区的实测土壤温度数据,分析了不同覆盖条件对土壤温度的影响及不同土层的土壤温度变化过程。结果表明:地膜覆盖对冻融期的土壤温度具有较好的增温效果,秸秆覆盖效果稍差;地膜覆盖和秸秆覆盖对土壤表土层增温效果较好,随着深度的增加,增温效果逐渐降低;地膜覆盖和秸秆覆盖在冻结期对土壤的增温效果最好,融解期的增温效果稍差,冻结稳定期增温效果很小;土壤温度变化过程在冻结期和融解期呈现不同特点,冻结期土壤温度随着土壤深度的增加而升高,融解期随着土壤深度的增加而降低,同时土壤融解速度远大于冻结速度。该研究结果可为寒旱灌区冻融期土壤水热运移提供参考,对冬小麦种植管理具有现实意义。     

秸秆隔层与地覆膜盖有效抑制潜水蒸发和土壤返盐

为了揭示秸秆隔层与地膜覆盖的蓄水控盐机理,通过室内土柱模拟试验,研究了浅层地下水埋深条件下秸秆隔层对土壤水分入渗过程以及结合地膜覆盖对蒸发过程和水盐运移的影响。入渗试验设置了均质土（对照）和秸秆隔层处理,蒸发试验在均质土和秸秆隔层处理的土表分别增设覆膜和不覆膜处理。研究结果表明：1）秸秆隔层不但降低了土壤水分入渗速率和湿润锋推进深度,还引起了湿润锋的不稳定性,即优先流现象的出现;2）秸秆隔层能抑制潜水蒸发,对累积蒸发量的抑制率可达75.07%～95.42%;3）秸秆隔层改变了土壤水盐时空分布特征,在入渗过程中可增加土壤含水率,降低土壤含盐量;蒸发过程中可将盐分控制在底土层中,抑制了土壤返盐;4）地膜覆盖可减少土壤水分散失和减弱盐分表聚,而秸秆隔层结合地膜覆盖对潜水蒸发和土壤返盐的抑制效应更强,淡化耕层作用更为明显。该研究结果可为河套灌区农田抑盐、保水和合理的耕作措施的制定提供依据和参考。     

不同地表覆盖下冻融土壤入渗能力及入渗参数（英）

为了研究不同地表覆盖下冻融土壤入渗能力的差异和入渗参数的变化规律,进行了一系列裸地、地膜覆盖地和秸秆覆盖地土壤田间入渗试验。研究表明,冻土的入渗能力主要受冻层的控制,冻层是入渗水分的控制界面,土壤冻融特征差异是影响不同地表覆盖下土壤入渗能力大小的主导因素。冻融土壤的水分入渗过程可用三参数考斯加科夫土壤入渗经验模型描述。水分入渗开始 1 min内的累积入渗量大小随着冻层厚度和密实度的增加而减小,随着土壤冻融循环次数增加而增大;入渗能力的衰减率随着冻层厚度和密实度的增加而减小;稳定入渗率大小主要取决于土壤冻结状态和入渗锋面处的水力特性。三入渗参数均与土壤含水率和冻结深度有关,不同地表覆盖下的土壤入渗参数随着冻层深度的增加而减小,随着土壤的消融解冻而增大。该研究成果对农业生产实际和水土保持具有重要的指导意义。     

地表覆盖对河套灌区土壤水热和番茄生长的影响

在河套灌区以不覆盖为对照,测定了地膜覆盖、秸秆覆盖、地膜+秸秆覆盖对土壤水热和番茄生长的影响。结果表明,地膜覆盖提高了土壤温度,而秸秆覆盖、地膜+秸秆覆盖降低了土壤温度,其中秸秆覆盖降低的幅度较大。在番茄生育前期不同覆盖可提高0—50cm土层的土壤水分含量,其中地膜覆盖效果最好。地膜覆盖使番茄产量提高了222.61%,地膜+秸秆覆盖使产量提高了17.04%,而秸秆覆盖则使产量降低了3.06%。地膜覆盖使水分利用效率提高了93.83%,地膜+秸秆覆盖使之提高了5.90%,秸秆覆盖则使水分利用效率降低了19.29%。河套灌区番茄播种时以地膜覆盖为宜,不宜采用秸秆覆盖。     

大田土壤冻融条件下入渗特性的试验研究

以冬小麦田冬季跟踪入渗试验为依据，揭示了冻融土壤水分入渗的基本特性，分析讨论了土壤累积入渗量，稳定入渗率在土壤冻结的解冻过程中的变化规律，并将薄层霜状冻层对土壤入渗特性的影响进行了讨论，其研究结果对于土壤水分入渗的研究和冬春灌溉水效果的研究具有理论意义，对冬春灌溉的用水管理具有实际意义。     

积雪与地表联合覆盖条件下冻融土壤水盐运移规律

为探索石河子灌区冻融季节积雪与地表联合覆盖条件下土壤水盐运移的变化规律,2015—2016年通过田间小区试验,进行了秸秆、地膜、活性炭3种地表覆盖和裸地对照在整个季节性冻融期土壤水盐时空动态变化规律研究。结果表明;地表覆盖比裸地具有更好的保墒、降盐效果。冻结土壤完全融通后,秸秆、活性炭覆盖出现含水量增幅的最大土层范围分别是0—30,0—40cm,反映出这2种覆盖经历冻融过程后更有利于土壤水分的保持和融雪水的高效利用;活性炭、秸秆、地膜覆盖和裸地在0—30cm土层含盐量相比初始值的增幅分别为18.08%,20.30%,30.91%,32.81%,可见活性炭覆盖下抑制盐分向上运移效果最为显著,秸秆覆盖次之;经历冻融过程,土壤水分和盐分变异性随土壤深度的增加而呈现递减趋势。     

秸秆深层覆盖对水分入渗及蒸发的影响

 为探讨秸秆还田对土壤水分入渗和蒸发造成的影响,通过在土表下20 cm处铺设3cm厚秸秆隔层的土柱试验表明:在灌溉水分入渗时,秸秆隔层阻碍了土壤重力水入渗,降低了土壤重力水由土壤上层向下层入渗的速率;在土壤水分蒸发过程中,秸秆层隔断了土壤的毛细管,使秸秆层以下土壤水很难通过土壤毛细管作用而向地表运移并蒸发。秸秆深层覆盖可以使深层土壤水分的蒸散量减少2%～3%,对深层土壤的蓄水保墒有积极的作用。     

秸秆覆盖对冻融期土壤墒情影响试验

为了研究秸秆覆盖对冻融期土壤墒情的影响,该文设置裸地、玉米秸秆覆盖厚度为5、10和15cm的4种地表处理,进行了冻融期的土壤水分迁移试验。结果表明,冻融期秸秆覆盖的保温效应改变了土壤冻结状,使覆盖厚度15cm田块未出现冻层,覆盖厚度5和10cm地块的土壤初冻时间比裸地分别滞后16和25d,且冻层厚度较裸地减小了29和42cm。受冻融作用的影响,裸地在40cm处出现聚墒区,秸秆覆盖田块在地表处和30～50cm处出现聚墒区。冻融期内玉米秸秆覆盖厚度为5、10和15cm田块地表水分波动幅度分别比裸地减小了1.12、6.46和8.7百分点;土壤融化后其地表0-10cm土壤平均含水率分别比裸地高9.45、9.04和8.99百分点。研究成果可为季节性冻土分布区实施秸秆覆盖措施提供参考依据。     

不同覆盖模式下砂壤土水盐运移特征研究

地表蒸发引起土壤水分的散失是造成盐分表聚的重要原因之一,土壤表层进行覆盖可改变地表结构,从而影响土壤水分蒸发和盐分迁移过程。为了揭示不同覆盖模式的蓄水控盐效果,通过室内模拟试验,研究了不同覆盖模式下土壤水分入渗过程和水盐迁移特征。试验设置无覆盖(CK)、覆砂(S)、覆砂+覆膜(SM)、覆秸秆+覆膜(JM)和覆秸秆+覆砂(JS)5种模式。结果表明:土壤表层进行的不同覆盖处理会降低土壤湿润锋推进速率和水分入渗速率,具有一定的阻渗作用;湿润锋推进距离与时间符合幂函数F=a·t~b,累积入渗量与时间符合Kostiakov入渗公式,湿润锋推进距离与累积入渗量符合线性关系I=K·Z_f+c。土壤表层进行的不同覆盖处理可有效抑制土壤水分蒸发,土壤保水效果为SMJSSJMCK;随土层深度的增加,土壤含水率减小的趋势逐渐减缓。土壤表层进行的不同覆盖处理也可减弱土壤盐分表聚,缩小盐分在土壤中迁移的范围;覆盖处理的土壤盐分主要在0—20cm范围内迁移,CK在0—35cm范围内。综合考虑不同覆盖模式对土壤水分入渗、抑制水分蒸发和减弱盐分表聚效果,认为砂石覆盖模式是较适合西北旱区的覆盖模式。     

季节性冻融土壤水盐动态预测BP网络模型研究

冻融土壤水盐运移模拟预测一直是冻土物理学和土壤水科学研究的热点和难点,而冻土水盐运动的特殊规律与分配特性是影响河套灌区土壤盐渍化发生、发展和演变的重要因素。该文基于内蒙古河套灌区5个冻融期（1994～1999）的水分、盐分和温度的田间实测资料,利用人工神经网络对冻融土壤水盐耦合运移进行了联合预测。结果表明：初冻期地下水埋深、初冻期含水率、初冻期含盐量、秋浇水量、11月到翌年4月的月平均地温等10个影响因子可以有效表征冻融土壤水分和盐分之间的强烈耦合关系,神经网络预测模型具有较好的精度。该研究为冻融条件下土壤水盐动态预报和灌区灌溉管理的研究开辟了新的途径。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.