发生分类半淋溶土在中国土壤系统分类中的归属特征

利用最新建立的1∶100万中国土壤数据库,研究了我国发生分类半淋溶土在中国土壤系统分类的归属及其在中国土壤系统分类下的空间和数量特征.结果表明,我国发生分类半淋溶土总面积为427 843.1 km²,可参比归属于中国土壤系统分类中的4个土纲,即淋溶土、雏形土、均腐土、人为土,分别占发生分类半淋溶土总面积的51.3%、35.2%、10.7%和2.8%,其中包含了系统分类的22个土类和38个亚类.对发生分类某一类型土壤分属于系统分类不同类型的面积比例及其标准偏差的分析表明,土壤参比归属的单元级别越低,越易于参比和把握.研究结果对于土壤类型的正确参比、中国土壤系统分类的应用具有很好的参考价值.     

大兴安岭北部兴安落叶松种子在土壤中的分布及其种子库的持续性

 种子年后原始老龄林下自然散布的兴安落叶松土壤种子极为丰富,有生活力的土壤种子数量为190～320粒／m2,并且不同林型间有显著差异。70%～80%的种子主要居于土壤表层2～4cm范围内。落叶松老龄林种子年后第一年夏季土壤中丰富的种子即锐减,土壤中大多数种子的生活力保持1年,少数稍长,也不超过2年。显然,落叶松土壤种子库属于间断类型。人工撒播种子试验结果表明,位于土壤浅层(0～10cm)的种子生活力保存只1年,而深层(10～20cm)尽管对种子生活力保持有利,也不能超过2年。土壤病害是种子致死的重要原因。     

Soil microbial activities in Luvisols and Anthrosols during 9 years of region-typical tillage and fertilisation practices in northern Germany

In order to evaluate soil functions of contemporary agricultural management practices, the adjustment of microbial biomass and C and N mineralisation capacities was monitored during 9 years following the implementation of conventional and reduced tillage, and mineral N and pig slurry fertilisation systems. Soil microbial biomass content and microbial activities decreased continuously from initial values. The decrease was slowed by slurry application, compared to either no or mineral N fertilisation, and both slurry and mineral N application stimulated soil microbial activities in the long-term. There were no significant differences in microbiological characteristics between conventional and reduced tillage for the 0 to 30 cm soil depth but microbial biomass and activity were highest from 0 to 15 cm depth under reduced tillage. Changes in several microbial properties became evident when analysing the whole experiment of 9 years and the soil unit is also of importance as shown by higher microbial activity level in Anthrosols in comparison to Luvisols.     

Evaluation of housekeeping genes as references for quantitative real-time PCR analysis of European eel,Anguilla anguilla

Eels are important aquaculture species for which an increasing number of reference genes are being identified and applied. In this study, five housekeeping genes [RPL7 (ribosomal protein L7), 18 S (18 S ribosomal RNA), EF1A (elongation factor 1α), ACTB (β-actin) and GAPDH (glyceraldehyde-3-phosphate dehydrogenase)] were chosen to evaluate their reliability as reference genes for quantitative real-time PCR (qPCR) for the study of Anguilla anguilla. The expression of the selected genes in different eel tissues was determined using qPCR at different growth stages or upon challenge by Anguillid herpesvirus (AngHV), and the expression levels of these genes were then compared and evaluated using the geNorm and NormFinder algorithms. Then, RefFinder was used to comprehensively rank the examined housekeeping genes. Interestingly, the expression of the evaluated housekeeping genes exhibited tissue-dependent and treatment-dependent variations. In different growth periods A. anguilla tissues, the most stable genes were the following: ACTB in mucus; 18 S in skin and kidney; RPL7 in muscle, gill, intestine and brain; EF1A in heart and liver; and GAPDH in spleen. In contrast, in AngHV-challenged A. anguilla tissues, the most stable genes were the following: 18 S in mucus; RPL7 in skin, gill, heart, spleen, kidney and intestine; EF1A in muscle and liver; and ACTB in brain. Further comparison analysis indicated that the expression of RPL7 and EF1A was stable in multiple A. anguilla tissues in different growth periods and in eels challenged by AngHV. Nonetheless, the expression level of GAPDH in eel tissues was lower, and it was unstable in several tissues. These results indicated that the selection of reference genes for qPCR analysis in A. anguilla should be made in accordance with experimental parameters, and both RPL7 and EF1A could be used as reference genes for qPCR study of A. anguilla at different growth stages or upon challenge by AngHV. The reference genes identified in this study could improve the accuracy of qPCR data and facilitate further studies aimed at understanding the biology of eels.     

Further evidence against linkage between christ-siemens-touraine (CST) and XG loci

Summary A Brazilian informative pedigree for the CST:XG linkage relationship is analysed. The present lods, together with those from previously published data, provide evidence for the exclusion of linkage until a value of around 0.34.     

Evaluation of housekeeping genes in Listeria monocytogenes as potential internal control references for normalizing mRNA expression levels in stress adaptation models using real-time PCR

Listeria monocytogenes is an important food-borne pathogen that can tolerate a wide range of stress conditions. However, its stress adaptation processes are still poorly understood. Real-time-based quantitative RT-PCR (qRT-PCR) provides a tool to probe gene expression changes underlying stress adaptation. But, a limitation to study mRNA levels by real-time qRT-PCR is that validated reference genes are required for normalization. Such genes are currently lacking for experimental models that may be applied to evaluate stress-related gene expression changes in L. monocytogenes. Therefore, five housekeeping genes (HKG) were studied as potential reference genes. Their expression stability was evaluated across 16 L. monocytogenes strains. Three experimental models designed to assess gene expression changes induced by cold, acid and high NaCl concentration stress adaptation were applied. The 16S rRNA gene was consistently the most stably expressed HKG across the different L. monocytogenes strains under all the experimental conditions. While the expressions of beta-glucosidase (bglA), Glyceraldehyde-3P-dehydrogenase (gap), RNA polymerase beta subunit (rpoB) and Ribosomal protein L4 (rplD) was stable amongst the different L. monocytogenes strains, they were prone to significant variations under the different stress adaptation models.     

Macrophyte communities in unimpacted European streams: variability in assemblage patterns, abundance and diversity

Macrophytes are an important component of aquatic ecosystems and are used widely within the Water Framework Directive (WFD) to establish ecological quality. In the present paper we investigated macrophyte community structure, i.e., composition, richness and diversity measures in 60 unimpacted stream and river sites throughout Europe. The objectives were to describe assemblage patterns in different types of streams and to assess the variability in various structural and ecological metrics within these types to provide a basis for an evaluation of their suitability in ecological quality assessment. Macrophyte assemblage patterns varied considerably among the main stream types. Moving from small-sized, shallow mountain streams to medium-sized, lowland streams there was a clear transition in species richness, diversity and community structure. There was especially a shift from a predominance of species-poor mosses and communities dominated by liverwort in the small-sized, shallow mountain streams to more species-rich communities dominated by vascular plants in the medium-sized, lowland streams. The macrophyte communities responded to most of the features underlying the typological framework defined in WFD. The present interpretation of the WFD typology may not, however, be adequate for an evaluation of stream quality based on macrophytes. First and most important, by using this typology we may overlook an important community type, which is characteristic of small-sized, relatively steep-gradient streams that are an intermediate type between the small-sized, shallow mountain streams and the medium-sized, lowland streams. Second, the variability in most of the calculated metrics was slightly higher when using the pre-defined typology. The consistency of these results should be investigated by analysing a larger number of sites. Particularly the need of re-defining the typology to improve the ability to detect impacts on streams and rivers from macrophyte assemblage patterns should be investigated. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Correspondences between classifications and between classes of entities in molecular genetics

Certain correspondences appear between the classifications and between the classes of various entities at molecular genetic level: types of fundamental correspondences between classifications and between classes of normal entities, on the one hand, and of mutant entities on the other hand; ranks of correspondences between classifications and between classes of entities. The concept of universality of the genetic code was reformulated on the basis of the above correspondences.     

Cervical smear adequacy: cellularity references were found to increase both interobserver agreement and unsatisfactory rate

Objectives:  To determine the degree of interobserver variation in the assessment of conventional cervical smear adequacy as defined by The Bethesda System (TBS) 2001, and to determine the effect of using reference images of known squamous cellularity when performing squamous adequacy assessments.
Methods:  Experimental pre-test/post-test design utilizing 70 conventionally prepared cervical smears. Sample smears containing scant squamous cellularity were independently rated on two occasions by six cytotechnologists. Time 1 was without the use of reference images, and Time 2 was aided by cellularity reference images. The κ statistic was used to compare rater agreement.
Results:  The level of agreement increased from an average κ of 0.26 (SD 0.10) for Time 1, to an average κ of 0.40 (SD 0.15) for Time 2. The difference in mean κ values at the two assessments was statistically significant ( t  = 3.71; P  = 0.002). Unanimous agreement among the raters was observed for 15 samples (21.42%) at Time 1 (only one of which was classified as unsatisfactory) and 21 samples (30.00%) at Time 2 (12 of which were classified as unsatisfactory).
Conclusion:  Interobserver agreement increased after cellularity reference images were implemented. Using TBS 2001 squamous adequacy criteria and images of known squamous cellularity as references resulted in a decreased number of smears reported as satisfactory.     

Relationship between species relative abundance and plant traits for an infertile habitat

This study tested whether differences in species abundance at an infertile site could be explained by differences in the species' plant traits. Nine traits were chosen for the analysis based on results of previous studies conducted across soil fertility gradients. The traits were measured for each of seven herbaceous species whose abundance ranged from 5% to 100% of locations occupied in a ridgetop habitat. Using linear regression, significant relationships were found between species relative abundance and each of five traits. In these relationships, a trait explained between 69% and 88% of interspecific variation in abundance. Relatively abundant species had a slower growth rate, smaller shoot mass, higher root to shoot ratio, slower loss of leaf tissue to herbivores and higher infection of roots by mycorrhizal fungi than less abundant species. Using three of these five traits (i.e. shoot mass, mycorrhizal infection and loss of leaf tissue to herbivores) as independent variables in a multiple regression equation explained 99% of interspecific variation in abundance. The latter result indicates that species relative abundance can be explained for a single habitat by choosing traits found to be related to species abundance in previous gradient studies. However, not every trait chosen was significantly related to species abundance. Therefore, a large number of traits may have to be chosen initially to ensure that some subset of these traits can explain species relative abundance.     

不同粒级土壤团聚体呼吸特征及其对碳排放的贡献

通过土盆培养试验研究了不同粒级黄棕壤团聚体呼吸特征及其对碳排放的贡献,结果表明:各粒级土壤团聚体及原状土在培养初期土壤呼吸速率较高,之后逐渐降低。在整个培养期间原状土保持了最大的土壤呼吸速率;土壤团聚体类型对土壤呼吸速率影响较大,3种粒级团聚体土壤呼吸速率大小表现为(5 mm)(1 mm)≈(1~5 mm),其中以5 mm团聚体对土壤碳排放的贡献最大。相关性分析表明,指数模型能较好地描述不同粒级团聚体的土壤呼吸对温度变化的响应;Q10值介于2.53~5.11之间且与土壤有机碳、全氮含量的变化规律基本一致,表现为1 mm团聚体有机碳、全氮含量和Q10值较大,5 mm、1~5 mm团聚体有机碳、全氮含量和Q10值相对较低,说明土壤团聚体粒级越小,其呼吸速率对温度越敏感。土壤有机碳、氮含量与土壤结构是影响土壤呼吸温度敏感性的重要因素。