柳杉人工林林分不同变量大小比数研究

采用胸径、生物量、冠幅和树高计测大小比数对崇州林场柳杉林的空间结构进行分析.结果表明,以胸径和生物量为度量变量的大小比数变幅最小,可信度最高,而冠幅和树高大小比数受不同树种树型的干扰而不如前两者可靠.各样地林分的胸径和生物量大小比数平均数值明显大于冠幅和树高大小比数数值,说明林木的胸径及生物量分化程度远大于冠幅与树高的分化.通过胸径的增长实现其生物量的增长,从而增强单木的竞争优势可能是林木分化的主要策略.     

How does forest landscape structure explain tree species richness in a Mediterranean context?

Although the strong relationship between vegetation and climatic factors is widely accepted, other landscape composition and configuration characteristics could be significantly related with vegetation diversity patterns at different scales. Variation partitioning was conducted in order to analyse to what degree forest landscape structure, compared to other spatial and environmental factors, explained forest tree species richness in 278 UTM 10 × 10 km cells in the Mediterranean region of Catalonia (NE Spain). Tree species richness variation was decomposed through linear regression into three groups of explanatory variables: forest landscape (composition and configuration), environmental (topography and climate) and spatial variables. Additionally, the forest landscape characteristics which significantly contributed to explain richness variation were identified through a multiple regression model. About 60% of tree species richness variation was explained by the whole set of variables, while their joint effects explained nearly 28%. Forest landscape variables were those with a greater pure explanatory power for tree species richness (about 15% of total variation), much larger than the pure effect of environmental or spatial variables (about 2% each). Forest canopy cover, forest area and land cover diversity were the most significant composition variables in the regression model. Landscape configuration metrics had a minor effect on forest tree species richness, with the exception of some shape complexity indices, as indicators of land use intensity and edge effects. Our results highlight the importance of considering the forest landscape structure in order to understand the distribution of vegetation diversity in strongly human-modified regions like the Mediterranean.     

Spruce budworm growth,development and food utilization on young and old balsam fir trees

Laboratory rearing of spruce budworm, Choristoneura fumiferana, in conjunction with field rearing, gravimetric analyses, a transfer experiment, and foliage chemical analyses at six dates during the period of budworm feeding activity indicated that the age of balsam fir, Abies balsamea, trees (70-year-old mature trees or 30-year-old juvenile trees) affected tree suitability for the spruce budworm via the chemical profile of the foliage. Insects reared on old trees had greater survival and pupal weight, shorter development times, and caused more defoliation than those reared on young trees. Young trees were more suitable for the development of young larvae (instars 2–5), while old trees were more suitable for the development of older, sixth-instar larvae. These results were confirmed by the laboratory transfer experiment. Young larvae fed foliage from young trees had higher relative growth rates (RGR), digestibility (AD), and efficiency of conversion of ingested foliage (ECI) than those fed foliage from old trees. These differences appeared to be related to the high N:tannins ratio, and the high contents of P present in young trees during the development of the young larvae. Old larvae fed foliage from old trees had higher relative growth rates, relative consumption rates (RCR), and digestibility of the foliage than those fed foliage from young trees. The high digestibility of the foliage of old trees was compensated for by a lower efficiency of conversion of digested food (ECD), which in turn resulted in no significant effect of tree age on the efficiency of conversion of ingested foliage by old larvae. The low relative consumption rate of old larvae fed foliage from young trees appeared to be related to the low N:tannins ratio, and the high contents of bornyl acetate, terpinolene, and °-3-carene present in young trees during the budworm sixth instar. Variations in these compounds in relation to tree age may serve as mechanisms of balsam fir resistance to spruce budworm by reducing the feeding rate of sixth instar larvae.     

Spatiotemporal variability of stone pine (Pinus pinea L.) growth response to climate across the Iberian Peninsula

Climate warming and increasing aridity have impacted diverse ecosystems in the Mediterranean region since at least the 1970s. Pinus pinea L. has significant environmental and socio-economic importance for the Iberian Peninsula, so a detailed understanding of its response to climate change is necessary to predict its status under future climatic conditions. However, variability of climate and uncertainties in dendroclimatological approach complicate the understanding of forest growth dynamics. We use an ensemble approach to analyze growth-climate responses of P. pinea trees from five sites along a latitudinal gradient in Spain over time. The growth responses to April-June precipitation totals were stronger in the north than in the south. Since the 1950s, the sensitivity of growth to April-June precipitation increased in the north and decreased in the south. Meteorological drought usually started in May in the southern sites, but in June-July in the northern sites. The water deficit in the southern sites is thus greater and more limiting for tree growth, and this likely accounts for the lower growth sensitivity during these months. Our results indicate that P. pinea has a high degree of plasticity, suggesting the species will withstand changing climatic conditions. However, growth response to drought regimes varies among P. pinea populations, suggesting that different populations have different capacities for acclimation to warmer and drier climate, and this may influence future vegetation composition.     

抗树鼩CD3ε单克隆抗体的制备及生物学特性鉴定

制备鼠抗树鼩CD3ε单克隆抗体,并对其生物学特性进行鉴定。     

Effects of the winter beechmast crop on bird occurrence in British gardens

Capsule Woodland birds were significantly less likely to occur in gardens in years of high beechmast crop.

Aim To test the hypothesis that woodland species that feed on beechmast will have significantly lower occurrence rates at garden feeders in mast years.

Methods Weekly winter occurrence rates at garden feeders between 1970/71 and 1999/2000 for 40 species were analysed in relation to annual beechmast abundance, classified into low, medium and high years. A repeated-measures logistic regression model was used to assess whether beechmast abundance explained further significant variation additional to underlying seasonal and annual trends.

Results Seven species that commonly feed on beechmast showed significantly lower occurrence in gardens in years of highest beechmast abundance: Great Spotted Woodpecker Dendrocopos major, Woodpigeon Columba palumbus, Great Tit Parus major, Coal Tit Periparus ater, Nuthatch Sitta europaea, Jay Garrulus glandarius and Chaffinch Fringilla coelebs. Blackbird Turdus merula and Siskin Carduelis spinus, which showed similar significant patterns, are likely to take beechmast as elements of their diet. Pied Wagtail Motacilla alba was the only insectivorous species to show significant effects, but occurrence was lowest in years of intermediate beechmast abundance. For the latter species, this may have been due to confounding effects of temperature, but there were no such confounding effects of either temperature, or the number of bird feeders provided in gardens, for the other nine species.

Conclusion Use of artificial food sources by birds in gardens is influenced by resources in the surrounding countryside, suggesting that food provided in gardens may play a significant part in the population dynamics of these species, that population monitoring without consideration of the garden habitat may be deficient, and that volunteer-based garden bird recording may provide data that can be used as an indicator of changes in the wider countryside.     

Habitat structure and disturbance affect small mammal populations in Mediterranean forests

Habitat structure, the physical arrangement of objects in space, affects animal populations, ecological interactions, species diversity, and ecosystem functioning. Conventional forest management practices that reduce habitat structural complexity are thus under reappraisal, and there are increasing efforts to understand how habitat structure affects functionally important species. We investigate here the effect of habitat structures on small mammal dens and their interactions with widespread antagonistic species (wild boars). Among habitat structures we considered tree dimension (diameter), shrub cover, rock cover, dead wood volume, and stump area. Ground cover with rooting signs measured wild boar disturbance. The number of small mammal dens was related positively to rock cover and tree diameter, and negatively to wild boar disturbance. Additionally, a positive interaction between wild boar disturbance and tree diameter emerged, showing that the effect of big trees on small mammal nesting was more evident with higher levels of disturbance. This study suggests that habitat structures that can be affected by forest management provide effective refuges for functionally important species. The effect of habitat structure on species survival and interactions thus needs to be addressed to understand ecosystem management and functioning.     

树鼩原代小胶质细胞的分离培养、纯化与鉴定

本文旨在建立树鼩(Tupaia belangeri)小胶质细胞原代培养及纯化的方法,为利用新型实验动物树鼩进行相关研究工作提供实验材料。将新生树鼩大脑皮质机械分离,皮质组织块用胰蛋白酶消化后制成细胞悬液;培养9～10 d后,分别采用直立手拍法、温和胰酶消化法以及恒温振荡法分离纯化树鼩小胶质细胞,通过差速贴壁进一步纯化。荧光显微镜下,利用小胶质细胞的特异性标记物CD11b抗体进行鉴定。结果显示,小胶质细胞分离培养第3天时呈静息状态,表现为梭形、杆状、分支状等不规则形态。细胞免疫荧光CD11b呈阳性。不同纯化方法细胞免疫荧光并计数显示,直立手拍法所获得的细胞产量明显高于恒温振荡法(P 0.05),细胞阳性率( 96%)明显高于温和胰酶消化法( 90%,P 0.05)。直立手拍法可获得产量及纯度高的树鼩原代小胶质细胞。     

Detecting distant homologs using phylogenetic tree-based HMMs

It is often desired to identify further homologs of a family of biological sequences from the ever-growing sequence databases. Profile hidden Markov models excel at capturing the common statistical features of a group of biological sequences. With these common features, we can search the biological database and find new homologous sequences. Most general profile hidden Markov model methods, however, treat the evolutionary relationships between the sequences in a homologous group in an ad-hoc manner. We hereby introduce a method to incorporate phylogenetic information directly into hidden Markov models, and demonstrate that the resulting model performs better than most of the current multiple sequence-based methods for finding distant homologs.