华北平原地下水资源承载力模糊综合评价

华北平原地下水资源承载力评价对保障水资源-生态环境-社会经济协调可持续发展具有极其重要的意义。采用模糊综合评价方法对华北平原市级地下水资源承载力进行分析,并结合灰色关联理论进一步探讨地下水资源承载力的影响因素。结果表明,华北平原地区各城市地下水资源承载力平均得分为0.38,其中尚具一定开发潜力的仅占19.0%,已接近开发潜力和地下水资源已严重超采且已出现地质环境问题的分别占38.1%和42.9%,总体承载力很小。经计算,地下水资源开采量与人口、第一产业产值、第三产业产值、GDP、工业产值的灰色关联度依次为:0.71,0.63,0.59,0.58和0.56,故影响华北平原地下水承载力最主要的因素为人口的剧增,农业灌溉用水的增加以及社会经济高速发展等社会因素。     

基于SPEI_KC的华北平原小麦玉米周年干旱特征分析

华北平原是中国重要的冬小麦和夏玉米（麦玉）生产基地，同时也是水资源紧缺的区域，农业生产极易受到干旱的影响。该研究在标准化降水蒸散指数（Standardized Precipitation Evapotranspiration Index，SPEI）的基础上，引进作物系数（Kc）改进SPEI指数，并基于改进后的SPEI_KC指数从作物生长季尺度、关键生育期尺度以及麦玉周年尺度分析1961-2017年华北平原冬小麦-夏玉米周年干旱的时空分布和变化特征。结果表明：1）SPEI_Kc指数在华北平原麦玉周年干旱评估中的适用性优于SPEI_TW指数（采用Thornthwaite公式计算的SPEI指数）和SPEI_PM指数（采用Penma-Monteith公式计算的SPEI指数）：在（实际）有旱（指数）评估为有旱情况下，SPEI_Kc指数在代表气象站点的平均准确率为76.13%，较SPEI_TW指数、SPEI_PM指数均有提高；在无旱评估为无旱情况下，SPEI_KC指数准确率为85.67%，较SPEI_TW指数、SPEI_PM指数分别均有提高。2）小麦关键生育期和小麦生长季的空间分布均呈轻旱在河北北部较高，重旱在研究区中部较高分布，玉米关键生育期和玉米生长季干旱频率的空间分布均呈中旱在河北北部较高，重旱在山东西部较高分布。总体来说，研究区的东南部干旱频率小于西北部，山东半岛地区和河北中部旱情较轻，河南省干旱严重。3）年代际干旱程度总体呈略微减小的趋势，具体表现为大部分研究尺度的轻旱发生频率增加，所有研究尺度的中旱和重旱发生频率减小；小麦关键生育期、小麦生长季以及玉米生长季的干旱频率减小，玉米关键生育期和麦玉周年尺度干旱频率增加。研究结果能够为正确认识气候变化背景下该地区干旱分布和变化，进而采取合理措施应对气候变化提供理论依据。     

基于小波消噪的三江平原低湿地月降水时间序列分析

近年来，由于水田面积迅速增加，导致三江平原低湿地井灌水稻区地下水位普遍下降，“吊泵”、局部超采现象时有发生，因此，三江平原地下水资源动态平衡急需恢复。为解决上述问题，以853农场为例，对实测逐月降水资料进行消噪、差分和标准化处理，建立了逐月降水量季节性时序预测模型，精度检验结果表明，模型有效性和可靠性较高。该模型揭示了区域逐月降水量的时间变化规律，为853农场乃至整个三江平原充分利用天然降水、合理制定水稻灌溉制度以及地下水资源的恢复和可持续利用提供了科学依据。     

华北平原灌溉农田的土壤水量平衡和水分利用效率

华北平原农业面临的主要问题是水资源短缺,地下水位持续下降。通过一维土壤水量平衡模型模拟了华北平原不同灌溉方式下农田耗水量和土壤水分深层渗漏的变化,并分析了作物的产量和水分利用效率。结果显示在正常的灌溉条件下,冬小麦季地下水的采补差额超过了200mm,某生育期一定程度的水分亏缺(返青期、拔节期或灌浆期)能明显减少冬小麦的耗水量,但没有明显减少作物的产量。因此,在一定程度上减少灌溉是可行的,但仍不能达到地下水资源的采补平衡。从长远来看,华北平原维持可持续的地下水灌溉开采,应减少冬小麦的种植面积、增加低耗水经济作物的比例。     

河南粮食核心区建设规划地下水环境影响评价

研究了实施河南粮食核心区规划对地下水环境的影响问题,提出了科学合理利用地下水资源的对策。河南粮食核心区北部区域已出现地下水超采情况,南部区域地下水开采潜力较大。超采区应采用井灌、渠灌联合运行方式,以及雨洪补源、引黄补源、地表水与地下水联合调蓄利用、节水灌溉等措施,控制地下水水位的下降。严格控制氮肥施用强度等措施可减轻地下水硝酸盐污染负荷。在规划实施中深入研究、跟踪评价农业面源对地下水的影响程度和范围,及时采取控制措施,保护地下水水质。     

普那菊苣引种栽培试验

针对石羊河下游民勤绿洲地下水资源严重超采,地下水位持续快速下降的现状,以及所引起的生态环境效应,提出了恢复地下水位生态需水量的概念和计算方法,并且预测出2000—2019各年恢复地下水位生态需水量。根据民勤绿洲的具体特点提出了恢复持续下降的地下水位、改善和恢复生态环境的一些可行措施。     

太行山山前平原地下水变化趋势与农业持续发展

水资源短缺是华北平原农业持续发展和经济腾飞的主要限制因素，近年来随着工农业的发展，用水量急剧增加；同时降水量明显减少，造成了华北平原水资源匮乏，地表干枯，连年超采地下水，使地下水位持续下降。形成很多地下水下降漏斗区。针对太行山山前平原水资源特点，以栾城县为例，研究了山前平原地下水变化规律、补给因素、排泄方式，同时对地下水资源进行了平衡分析，据此提出了太行山山前平原农业用水方略。     

内蒙古德岭山地区灌溉农业发展对浅层地下水系统演化的影响

为了了解灌溉农业发展对浅层地下水系统演化的影响,该文以1979年内蒙古德岭山地区浅层地下水系统未遭受人类活动强烈干扰时的状态为初始状态,采用水均衡原理计算2008年地下水的各种补排量,并进行地下水质量评价。通过对比初始状态与现状条件下浅层地下水系统输入(补给项)和输出(排泄项)的变化、水动力场与水化学场的变化,分析该地区浅层地下水系统的演化方向和规模。研究结果表明:灌溉农业的发展已成为影响浅层地下水系统演化的主要因素。灌溉农业对研究区地下水系统动力场演化的影响主要表现为局部区域地下水水位的持续降低和地下水流场的剧烈变化;对地下水系统化学场演化的影响主要表现为地下水化学类型的改变和地下水污染的加重。     

河北平原农田耗水与地下水动态及粮食生产相互关系分析

农田耗水是河北平原地下水资源消耗的主体,农田耗水与地下水动态、粮食生产互制机理研究可为农业节水提供重要依据。基于1981—2010年河北省经济统计年鉴、地下水开采量与地下水位、常规气象等数据,分析了河北平原近30年来农田耗水、粮食产量、降水量、地下水等动态变化特征,揭示了它们之间的相互响应关系。结果表明,近30年来,河北平原农田耗水总量约722.4 km3,生产粮食约5.9×108 t,开采地下水约440 km3(其中约330 km3用于农田灌溉),地下水位共下降约11.5 m;河北平原农田耗水与粮食产量总体呈逐年上升趋势,尽管2000年以来地下水开采量有所减少,但地下水位一直持续下降;农田耗水与地下水开采量、地下水埋深、粮食产量相互之间关系密切,每生产1 t粮食所消耗的水资源约1 224.4 m3(包括地下水597.1 m3),而地下水开采量每增加1 km3,河北平原地下水位实际下沉约0.03 m;农田耗水、地下水埋深均与年降雨量无明显相关性,由于降水入渗、灌溉渗漏不足以弥补开采的地下水,超采是引起河北平原地下水位持续下降的直接原因。因此,进一步发展节水农业、提高灌溉效率是促进河北平原农业可持续发展的必然选择。     

华北平原灌溉用水强度与地下水承载力适应性状况

针对华北平原农灌区地下水严重超采问题,基于近30a以来降水、水资源和农林灌溉状况的变化过程和现状,应用地学模数理念、均衡理论和MapGIS技术,建立了适应性状况评价指标体系与方法,以0.49km2精度识别了华北平原农林灌溉用水强度与当地地下水可采资源量之间适应性状况。研究结果表明,华北平原中部的大部分地区农林灌溉用水强度处于"严重不适应"状态,河北平原大部分地下水超采区农林灌溉用水强处于"极严重不适应"状态,其中小麦等夏粮作物灌溉用水强度占50%以上,蔬菜作物和耗水型果林灌溉用水强度所占比率呈显著增加趋势,应避免非理性持续大幅增加。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

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     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.