含不可忽略缺失数据非线性再生散度模型参数的Bayes估计

给出协变量带有不可忽略缺失数据的非线性再生散度模型的Bayes方法,缺失数据机制由Logistic回归模型来确定.Gibbs抽样技术和Metropolis-Hastings算法(简称MH算法)用来得到模型参数、缺失数据机制中回归系数的联合Bayes估计,并用实例加以说明.     

Total economic value of wetland conservation in Sri Lanka identifying use and non-use values

In tropical regions, mangroves, clean (unpolluted) water-bodies and fish are important aspects of wetland areas, which are considered as the basic requirement for livelihood improvement in local communities. Particularly, their conservation is very important to both inland as well as inshore fisheries. However, conservation of such areas is dependent on the perceptions of key stakeholders in the area. A novel approach of a one and one-half bound based contingent valuation method (CVM) was implemented to measure the stakeholder willingness to pay (WTP) towards the conservation of fish, mangroves and water in a Sri Lankan wetland area. Estimated median WTP is Rs. 264.26, which is thought reliable when considering average income in the community. The analytic hierarchy process (AHP) was used to separate use and non-use values from the total value. Results show that non-use values are a significant component in the elicited WTP value, of between 45-55%. In the past such commodities have been assigned zero or low values due to difficulties involved in assigning economic values.     

Comparison of cytotoxic activities betweenin vitro and field grown plants ofTyphonium flagelliforme (Lodd.) blume

Anin vitro cytotoxicity screening of theTyphonium flagelliforme extracts indicated high cytotoxicity effect on human lung carcinoma NCl-H23 cells and human mammary gland carcinoma T-47D cells, but the extracts were not active on human liver carcinoma HepG2 cells. NCl-H23 cells were more susceptible toT. flagelliforme extracts than T-47D cells. EDP₅₀ values of the hexane fractions of the mature plant and thein vitro plantlet ofT. flagelliforme on NCl-H23 cells were less than 2 μg/mL Extract from the mature plant was relatively more cytotoxic than the one fromin vitro plantlet except for the hexane fraction. The chloroform and butanol fraction of the mature plant had higher cytotoxicity effect than the fraction fromin vitro plantlet on NCl-H23 cells. All the 3 fractions (hexane, chloroform, and butanol) of the mature plant exhibited higher cytotoxicity effects on human mammary gland carcinoma T-47D cells than the 3 fractions ofin vitro plantlet. However, the human liver carcinoma cells were resistant toT. flagelliforme extracts except for higher concentration of hexane fractions of both the mature and thein vitro plants and the chloroform fraction of the mature plant. Micropropagated plantlets ofT. flagelliforme could hence be used as herbal materials for the treatment of human lung and breast cancers.     

Estimating plant responses to climate by direct gradient analysis and geographic distribution analysis

We characterised the climatic behaviour of 53 woody species in terms of the climatic factors that play the main role in controlling species distribution in the study area. Floristic and climatic data were obtained from 150 stands in sites under climatic control (i.e. eu-climatopes). The sampling strategy used allowed a reliable match between floristic and climatic observations. Different methods of frequency analysis and goodness-of-fit tests were used to identify associations between species occurrence and climatic characteristics. The species' responses were summarised by statistics describing ecological preferences and amplitudes, and species were grouped accordingly. A Gaussian response model was fitted to the abundance data along the main climatic gradients for selected species and response surfaces were derived by spatial analysis for a set of indicator species. Frequency analysis methods detected 42 indicator taxa for the Baudiere's Qe drought index, and lower numbers, 34 and 22, respectively, for the mean minimum coldest-month temperature and the daily temperature range in the coldest month. Goodness-of-fit tests revealed a lower number of ecological profiles with statistically significant deviations from equidistribution. We discuss the relative performance of the different methods and suggest that the combined use of statistical tests and frequency analyses may improve estimation of the environmental requirements of species. We also recommend using the species' responses to key environmental factors as reliable criteria in the definition of plant functional types. This revised version was published online in August 2006 with corrections to the Cover Date.     

What do the biodiversity experiments tell us about consequences of plant species loss in the real world?

Experiments where the diversity of species assemblage is manipulated are sometimes used to predict the consequences of species loss from real communities. However, their design corresponds to a random selection of the lost species. There are three main factors that limit species richness: harshness of the environment, competitive exclusion, and species pool limitation. Species loss is usually caused by increasing effects of these factors. In the first two cases, the species that are excluded are highly non-random subsets of the potential species set, and consequently, the predictions based on random selection of the lost species might be misleading. The data show that the least productive species are those being recently excluded from temperate grasslands and consequently, species loss is not connected with decline of productivity. The concurrent species loss in many communities, however, means also a reduction of the available diaspore pool on a landscape scale, and could result in increased species pool limitation in other communities.     

武汉和天津园林植物叶片热值比较研究

对天津和武汉两地一些园林植物叶片的春季干重热值、灰分含量和去灰分热值进行了比较 ,结果发现 ,无论在武汉还是天津 ,所测园林植物的干重热值均表现为乔木 >灌木 >草本的递减趋势 ,灰分含量则呈现相反的趋势即草本 >灌木 >乔木 ,去灰分热值在武汉与干重热值的趋势一致 ,但在天津却是乔木 >草本 >灌木。同一类型的植物干重热值都是低纬度的武汉高于高纬度的天津 ,灰分含量相反 :天津高于武汉 ;乔木和灌木的去灰分热值也是武汉高于天津 ,草本植物例外。两地共有的 7种植物平均值相比 ,干重热值和去灰分热值都是武汉 >天津 ,同一植物种相比 ,7种植物中 ,有 5种植物的干重热值和去灰分热值的地区差异与平均值一致 ,即武汉 >天津 ,只有刺槐和白三叶例外。     

一种快速鉴定转基因植物纯合体的新方法

植物转化中鉴定转基因植物的整合性是一个很重要的步骤,常规方法是对独立分离的转基因T1代植株产生的T2代进行转基因分离比率研究,以检测T1代的转基因整合状态,不仅费时费力,而且浪费了T1代资源。本介绍一种应用双重定量实时PCR技术鉴定转基因植物纯合子的新方法：以T1代植物DNA为模板,根据转基因后代的Ct表型值鉴定其转基因整合状态,Ct值接近2的为转基因纯合型,Ct值接近1的为转基因杂合型。用这种方法,可以同时对数十个T1代转基因幼苗的整合状态进行快速鉴定,准确率为100％。     

黄腹角雉血液生理生化指标的测定

用常规方法对不同年龄及性别的黄腹角雉血液 2 1项生理生化指标进行了测定 ,结果表明 :黄腹角雉 6～ 2 0月龄组MCH指标显著低于 2年龄以上组 (P <0 0 5 ) ,不同年龄间其它指标及不同性别间所有指标均差异不显著 (P >0 0 5 )。     

Landscape patterns of indicator plants for soil acidity in the Bavarian Alps

Aim Electronic distribution atlases and lists of ecological indicator values are becoming important tools in plant geography. In this contribution, we combine a geographical and an ecological data bank, and map out patterns of indicator value spectra (instead of single or average values) across a physiographically complex landscape. For our study, we select indicators of soil pH and carbonate content as key environmental factors that strongly affect overall plant diversity patterns in the temperate zone. Our goal is to relate the distribution and diversity of plant groups that are indicators of soil pH and carbonate content to environmental controls at the landscape‐scale, and thus contribute to a causal understanding of species pools. Location We studied the Bavarian Alps, which represent the German portion of the Northern Alps. Methods Based on the existing floristic survey, we calculated relative frequencies of nine classes of indicator plants for soil pH and carbonate content in grid cells. The resulting attribute matrix (cells by indicator class frequencies) was subjected to principal components analysis and to k‐means clustering. Results were compared and mapped out in the grid array of the whole region, resulting in continuous and discrete representations of species pool structure. We used a geographical information system to derive physiographical landscape properties from a geological map and a digital elevation model, and analysed their statistical relationship with the shapes of indicator spectra. Results and Main conclusions Averages of indicator values for soil pH and carbonate content follow the geological structure quite closely. Surprisingly, the diversity of indicator plant groups does not appear to be a function of geological or topographic heterogeneity. Rather, it seems to be related to areas of high elevation with uniform geology. The effect is a matter of additional acidophytes in high mountain areas and, in the high calcareous Alps, extreme calciphytes, while species with intermediate requirements are rarer than usual. For explanation, we suggest two facts: (1) a frequent lack of mature soils at high elevations and (2) particularities in soil genetic processes occurring under the harsh climatic conditions of high mountains.