薄层农田黑土全量碳及氮磷钾含量的空间异质性

利用地统计学对黑龙江省双城市薄层农田黑土的全碳、全氮、全磷、全钾的空间异质性进行了分析.结果表明,4种养分含量分布均具有较大的空间异质性.土壤全碳含量的空间分布主要受黑土层厚度的影响,与全磷含量的空间分布吻合度高;土壤全钾的空间异质性最差,只是中部沿西南方向区域略低外,其余变化较小.土壤全碳与全氮、全磷,全氮与全磷都存在极显著正相关,而土壤全钾与全碳、全氮、全磷为负相关,但不显著.全量碳、氮、钾主要受结构性因子的影响,分别占86.8%,85.4%,81.8%,全磷受结构性因子和随机因子的影响各占1/2.     

海伦黑土有机碳和速效养分空间异质性分析

应用地统计学的方法结合GIS空间分析技术,对海伦市黑土农田区域采集的65个耕层(0~20cm)土壤样本进行了数据处理,并对其全碳、碱解氮、速效磷和速效钾含量的空间分异特征进行了研究和探讨。结果表明,海伦黑土全碳、碱解氮和速效钾半变量函数曲线的理论模型符合高斯模型,速效磷的理论最佳模型为球状模型。全碳、碱解氮和速效磷表现为中度空间相关,其空间变异受结构性因子和随机因子的影响各占一半。速效钾属于高度空间相关,其变化主要受结构性因子的影响。土壤全碳与碱解氮具有显著的正相关,二者在空间分布上吻合度较高。全碳和碱解氮都与速效钾呈显著负相关。地统计学分析土壤养分的空间变异特征和1978年海伦县自然资源综合考察对黑土农田土壤肥力调查的结果具有相同的异质性。利用地统计学分析的方法,对区域农业生产合理布局、综合治理水土流失都具有重要的意义。     

喀斯特地区烟田土壤养分的空间变异特征

以我国典型的喀斯特地区—贵州省毕节地区为研究区域,利用地统计学和地理信息系统(GIS)相结合的方法对烟田土壤养分的空间变异特征进行研究,皆在为喀斯特地区烟草种植的平衡施肥及生态环境保护提供依据。描述性统计结果表明,研究区烟田土壤各养分指标均属中等程度变异。半方差函数分析表明,研究区烟田土壤全氮、全钾、速效磷变异函数的最适模型是球状模型,全磷和速效钾的最适模型是线性模型,碱解氮、pH和有机质的最适模型为指数模型;速效磷表现为强烈的空间自相关性,主要受结构性因素影响,而全氮、全磷、全钾、碱解氮、速效钾、pH和有机质表现为中等空间相关性,受结构性因素和随机性因素共同影响。普通克里格插值的土壤养分空间分布图表明,研究区域内烟田土壤全氮、全钾、速效磷和速效钾含量分布呈现空间连续分布的特点,而全磷、碱解氮和pH、有机质含量没有明显的分布规律,这主要与喀斯特地区复杂的立地因子和人为影响有关。     

小尺度土壤养分的空间变异及其影响因素探讨—以江苏省无锡市典型城乡交错区为例

以江苏省无锡市城乡交错区为例,在8km2范围内,采集102个土壤表层样,利用地统计学和G IS相结合的方法,研究了土壤全量和速效氮、磷、钾的空间变异特征,并对其影响因素进行了探讨。结果表明土壤养分空间变异程度从大到小依次为:土壤全氮>土壤全磷>土壤速效磷>土壤速效氮>土壤速效钾>土壤全钾。土壤全氮空间变异受到土壤类型的影响,土壤全磷的空间变异与居民点分布有关,土壤全钾空间变异与土壤粘粒关系最密切。土壤全量养分和相应的速效养分具有显著相关关系,在空间分布上,也分别存在不同程度的相似性。同时土壤全磷和土壤速效养分受土地利用影响也较大。研究还表明,城乡交错区土壤氮、磷流失风险增加,需要实施有效措施控制氮、磷肥料的过度施用。     

典型喀斯特峰丛洼地坡面土壤养分空间变异性研究

采用线形取样,利用地统计学方法研究了典型喀斯特峰丛洼地坡面土壤养分的空间变异特征.结果表明:有机碳、全氮、碱解氮和速效钾具有相似的空间变异结构,其变程变化在212～251 m之间,与坡面不同土地利用方式的空间范围相当.全磷和全钾的变异尺度较小,为141.2 m和120.6m.受部分耕地施用磷肥影响,速效磷的变异尺度最小,仅为85.1 m.除pH值外,土壤各养分均表现为强烈的空间相关性.有机碳、全氮、碱解氮等养分的空间分布表现出随着海拔高度增加而增大的特征,人类的耕作管理和峰丛洼地特殊的水文地质过程是影响土壤养分空间变异的主要因素.     

亚热带红壤丘陵区典型景观单元土壤养分的空间变异

基于区域化变量理论和地理信息系统的空间分析功能,应用地统计学的半变异函数定量分析了亚热带红壤丘陵区典型景观单元土壤养分的空间异质性特征。结果表明,土壤有机碳和全磷的理论模型为球状模型、全氮为高斯模型、土壤pH为指数模型。在60m步长间隔尺度下,土壤有机碳、全氮和pH有强烈的空间相关性,土壤全磷空间相关性为中等程度。4种土壤养分的空间自相关范围具有明显的差异,有机碳的有效变程最大(为261m),全氮(208m)和pH(156m)次之,全磷的有效变程最小(133m)。其空间自相关范围的差异由本身的养分、土地利用格局、地形和人为管理措施等因素所决定。在GIS支持下,采用Kriging插值方法,分析景观单元内土壤养分的空间分布格局看出,土壤有机碳和全氮含量呈现出明显的条带状和斑块状的梯度变化,并表现出极为相似的空间分布格局;土壤全磷的空间分布随机性强,斑块变得更加琐碎并呈现镶嵌的星空状分布;土壤pH的空间分布格局处于其三者之间,没有表现出明显的条带状分布。总体上说,基于整个景观尺度的4种土壤养分的半方差拟合效果优于不同土地利用类型的拟合效果。     

梁子湖湿地土壤养分的空间异质性

2003年10月利用地统计学方法对梁子湖湿地保护区内一块63.9km2区域的土壤养分的空间变异进行了研究。以400m400m的网格采集了101个表层(015cm)土壤样品。分析结果表明,土壤养分有较大的空间变异,土壤有机质、全氮、全磷、速效氮变异系数分别是36.0%、30.6%1、3.7%和29.3%;速效磷的变异系数最高为50.4%。土壤有机质、全氮、全磷、速效氮和速效磷的理论模型均为球状模型。土壤有机质、全氮、全磷、速效氮具有中等空间自相关性,随机变异分别是68.5%、68.3%、75%和71.5%;速效磷的自空间相关性较弱,变异为82.4%。5种养分的空间自相关距离比较接近,变程在2853m～963m之间。通过克里格插值进行土壤养分空间插值制图显示,土壤养分表现出空间分布的相似性。     

湘中南土地整理后烟田土壤肥力指标评价及空间变异特征

掌握土地整理区土壤养分特征已成为烟田快速培肥和提升土壤质量的首要问题。采用GIS与地统计学相结合的方法,评价了土地整理后烟田土壤养分等肥力指标的适宜性等级状况及其空间变异特征。结果表明:研究区土壤偏酸,有机质、碱解氮含量普遍缺乏,存在较大面积的缺钾现象;各肥力指标均属于中等变异,变异系数大小顺序依次为有效磷速效钾碱解氮有机质全氮全磷全钾pH值。有机质和速效钾的变异函数比较符合指数模型,全钾、碱解氮用高斯模型拟合效果好,而pH值、全磷、全氮和有效磷则以球状模型拟合效果最佳。肥力指标的块金系数[C0/(C0+C)]中,土壤有机质、全钾、碱解氮分别为0.903,0.998,0.823,空间相关性较弱;而pH值、全氮、全磷和有效磷的块金系数[C0/(C0+C)]变化范围为0.501~0.724,具有中等空间相关性;各肥力指标空间变程为99~1 003m,最大和最小值分别为全钾和碱解氮;各肥力指标表现出不同的空间分布特征,其中,pH值呈斑块状,碱解氮及全钾呈条带状,全磷整体上呈从北至南含量增加的梯度分布格局。     

漫岗丘陵区黑土村级农田土壤养分空间变异研究

基于地理信息系统(GIS)和地统计学方法,对黑龙江省漫岗丘陵区的拜泉县富业村农田黑土耕层采集的180个样本的有机质、碱解氮、速效磷和速效钾四种养分要素的空间变异规律进行了分析和探讨。研究表明,有机质变异函数曲线的理论模型符合高斯模型,碱解氮、速效磷和速效钾的理论模型表现为指数模型。碱解氮、速效磷和速效钾属于中度空间相关,受结构性因子和随机因子的影响,但程度有所差异。有机质属于高度空间相关,其变化主要受结构性因子的影响。碱解氮的相关距离最大为4405 m,有机质的相关距离最小为234 m,速效磷和速效钾的相关距离分别为543 m和1128 m。施肥是导致该村土壤养分空间变异性的主要原因。基于土壤养分状况和空间分布特征,目前需要考虑对该村土壤氮、磷、钾进行分区管理。利用地统计学分析的方法,对合理利用土地、综合治理水土流失的以及指导当地合理施肥等都有重要的意义。     

三江平原环型湿地土壤养分的空间分布规律

以三江平原环型湿地作为研究对象，对其环带状植被区湿地土壤的有机碳、全氮、全磷和全钾的空间分布规律进行了初步研究。结果表明，环型湿地土壤有机碳、全氮、全磷和全钾具有明显的空间水平分异规律，有机质、全氮、全磷的含量由环型湿地中心向边缘逐渐减少，全钾的含量和碳氮比逐渐增加。土壤有机碳、全氮、全磷和全钾在垂直方向上具有明显的分层和富聚现象，自上而下，有机质的含量逐渐降低；全氮含量除漂筏苔草群落外，其他各群落土壤全氮含量呈先增加后减少的分布；大部分植物群落全磷含量呈先减后增的“V”型分布；全钾含量呈表层和底层较高、中间层较低的“中空”状分布。通过相关分析表明，环型湿地土壤有机碳与全氮具有相似的空间分布规律，全钾与有机碳、全氮具有相异的空间分布规律，而全磷具有自己独特的空间分布规律。环型湿地土壤的有机碳、全氮、全磷和全钾的空间分布主要受植物体元素含量、生物过程和水文地貌过程影响，它通过过程影响湿地的功能。研究环型湿地的有机碳、全氮、全磷和全钾的空间分布规律不仅有助于完善湿地土壤形成和发育的理论，探明湿地的生态过程和功能，而且为合理利用和保护湿地提供科学依据。     

“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.