白皮松交配系统及其种内遗传多样性分量比的研究

应用同工酶淀粉凝胶技术分析了白皮松天然群体的交配系统,结果表明白皮松天然群体的多位点异交率为0 451～0 522,在松属中处于较低水平,这与白皮松天然群体较低的杂合度和很弱的基因流结果吻合,进一步讨论了导致白皮松异交率低的原因。白皮松群体内家系间存在明显的遗传分化,其半同胞家系分化系数为0 322,高于群体间的遗传分化水平。群体/家系/子代个体三者间的遗传多样性分量比为DAP∶DAF∶DIF≈1∶2∶4。

聚类组合研究的新进展

作为目前聚类分析的新兴研究热点,聚类组合方法能将两种或多种聚类方法集成起来以改善其性能。从聚类多样性和共识函数两方面综述了最新研究进展,探讨将神经网络组合的思想用于聚类组合。最后指出了将来可能的研究方向。

Fish community diversity in the middle continental shelf of the East China Sea

The status of fishery stocks in the coastal waters of China is far from ideal, mainly due to climate change and the impacts of human activities （e.g., pollution and overfishing）. Thus, the restoration and protection of fishery resources have become critical and complex. The stability and balanced structure of the fish community is a basic foundation for the protection of fishery resources. Based on data collected from bottom trawls by the R/V Beidou in continental shelf of the East China Sea in November 2006 and February 2007, changes in the composition and diversity of fish species and functional groups were analyzed. The research area was divided into offshore waters and inshore waters by the two-way indicator species analysis （TWIA）. The results showed that the dominant species were different between offshore waters and inshore waters and also varied with the survey time. The most abundant family was Sciaenidae and Teraponidae in November 2006, Sciaenidae, Engraulidae and Triglidae were most abundant in February 2007. The species belonged mainly to mobile piscivores （G6）, benthivores/piscivores （G4）, benthivores （G3） and planktivores （G1）, and the dominant species in November 2006 were commercial species （e.g. Larimichthys polyactis and Trichiurusjaponicus）, but small-sized species were dominant in February 2007 （e.g., Harpadon nehereus, Benthosema pterotum, Champsodon capensis, and Acropoma japonieum）. The species diversity showed a similar trend as the functional group diversity. Stations with higher diversity were mainly distributed in inshore waters in February 2007, whereas higher diversity was found in offshore waters in November 2006. The highest biomass and species number were found in G6 group, followed by the G4, G5 and GI groups. The distribution of the number of individuals of each functional group showed the opposite trend as that of the biomass distribution. In addition, the size spectra were mainly concentrated around 3-29 cm, and the individual number of fish species gradually decreased with the increase in body size, but the relative biomass showed a moderate fluctuation in each size class. These changes showed that species with faster growth rate and earlier maturity age became dominant in continental shelf of the East China Sea. So the variations in biological characteristics of fish should be fully considered in maintaining sustainable utilization of fishery resource.

Plant Communities and Factors Responsible for Vegetation Pattern in an Alpine Area of the Northwestern Himalaya

The study intended to describe the alpine vegetation of a protected area of the northwestern Himalaya and identify the important environmental variables responsible for species distribution.We placed random plots covering different habitats and altitude to record species composition and environmental variables.Vegetation was classified using hierarchical cluster analysis and vegetation-environment relationships were evaluated with Canonical Correspondence Analysis.Four communities,each in alpine shrub and meadows were delineated and well justified in the ordination plots.Indicator species for the different communities were identified.Maximum species richness and diversity were found in community IV among shrub communities and community II among the meadows.Studied environmental variables explained 61.5% variation in shrub vegetation and 59.8% variation in meadows.Soil variables explained higher variability (～35%) than spatial variables (～21%) in both shrubs and meadows.Altitude,among the spatial variables and carbon/nitrogen ratio and nitrogen among the soil variables explained maximum variation.About 40% variations left unexplained.Latitude and species diversity among the other variables had significant correlation with ordination axes.Study showed that altitude and C/N ratio played a significant role in species composition.Extensive sampling efforts and inclusion of other non-studied variables are also suggested for better understanding.

Effects of Maize Residue Quality and Soil Water Content on Soil Labile Organic Carbon Fractions and Microbial Properties

Investigating the effects of residue chemical composition on soil labile organic carbon （LOC） will improve our understanding of soil carbon sequestration. The effects of maize residue chemical composition and soil water content on soil LOC fractions and microbial properties were investigated in a laboratory incubation experiment. Maize shoot and root residues were incorporated into soil at 40% and 70% field capacity. The soils were incubated at 20 ℃ for 150 d and destructive sampling was conducted after 15, 75, and 150 d. Respiration, dissolved organic carbon （DOC）, hot-water extractable organic carbon （HEOC）, and microbial biomass carbon （MBC） were recorded, along with cellulase and β-glucosidase activities and community-level physiological profiles. The results showed that the cumulative respiration was lower in root-amended soils than in shoot-amended soils, indicating that root amendment may be beneficial to C retention in soil. No significant differences in the contents of DOG, HEOC and MBC, enzyme activities, and microbial functional diversity were observed between shoot- and root-amended soils. The high soil water content treatment significantly increased the cumulative respiration, DOC and HEOC contents, and enzyme activities compared to the low soil water content treatment. However, the soil water content treatments had little influence on the MBC content and microbial functional diversity. There were significantly positive correlations between LOC fractions and soil microbial properties. These results indicated that the chemical composition of maize residues had little influence on the DOC, HEOC, and MBC contents, enzyme activities, and microbial functional diversity, while soil water content could significantly influence DOC and HEOC contents and enzyme activities.

Using the inverse Poisson distribution to calculate multiplicity of infection and viral replication by a high-throughput fluorescent imaging system

Dear Editor,For virologists,it is crucial to confidently determine the concentration of infectious particles that are utilized and produced in experiments（Dulbecco,1952;Bushar and Sagripanti,1990;La Barre and Lowy,2001;Gueret et al.,2002;Gao et al.,2009;Kutner et al.,2009;Grigorov et al.,2011.