On the integrated interpretation of indirect site ordinations: a case study using semi-arid vegetation in southeastern Spain

The need for rigorous methods of interpreting indirect site ordinations is discussed and the problem of oblique habitat and phytosociological trends is emphasized. A sequential approach, termed integrated interpretation, is introduced to overcome this problem. It first involves a technique termed rotational correlation a linear form of trend surface analysis, which locates the best fit between a habitat variable and the coordinates of a pluridimensional ordination. The coordinates at positions of best fit are then used to produce two-way site-species tables (seriation arrays) which summarize floristic variation in relation to each major habitat trend. The seriation arrays can also be used to identify groups of differential species. Integrated interpretation is demonstrated using semi-arid vegetation from Murcia Province, SE Spain. A two-axis site ordination of vegetation data by non-metric multidimensional scaling is shown to have two oblique trends related to aspect-induced topoclimates and types of past anthropogenic disturbance. Rotation of the configuration to maximum linear correlation achieves very high levels of explanation for each factor. Rotated ordination coordinates from the correlation analysis are used to obtain two seriation arrays and floristic noda which relate directly to the two underlying habitat trends. A floristic discontinuity is revealed on the topoclimate continuum and it is hypothesized that temperature conditions are a major determinant of floristic composition, but that moisture partly determines vegetational cover and phytomass. Several patterns of past cultivation are detected and associated with five main kinds of geomorphological unit, together with some evidence that the rate of succession is partly determined by topoclimate. The integrated approach to interpretation is compared with visual methods and other multivariate techniques. A case is made for increased interpretational rigour in site coordinate studies, especially the discontinuation of trend-seeking using individual unrotated ordination axes.Nomenclature of vascular plants follows Tutin et al. (1964–1980) Flora Europaea 5 Vols. Cambridge University Press, Cambridge. Nomenclature of syntaxa follows Rivas-Goday & Rivas-Martinez (1967).I am indebted to J. A. Michel, Dr M. A. Abdelrahman and Monica M. Dargie for field assistance. Field discussion with Dr R. L. Wright, Dr M. P. Austin and Professor F. Esteve Chueca was most helpful; the latter assisted with confirmation of vascular plant voucher specimens. Non-vascular taxonomy was determined by Dr C. Humphries (mosses and one alga) and Dr O. L. Gilbert (lichens). An anonymous referee suggested an approximation of the analytical solution to rotational correlation, and Dr N. R. J. Fieller assisted with its confirmation. The project was assisted by a grant from the University of Sheffield Research Fund.     

Direct and correlated responses to selection for weaning weight,post-weaning weight gain and six-week weight in mice

Summary Four lines of mice were formed from a common base population and selected for 37 generations for either increased 3-week weight (weaning weight), 6-week weight, 3–6 week gain, or maintained as a randomly bred control line. Realised heritability estimates for short-term (long-term) responses were 0.33±0.20 (0.07±0.10), 0.46±0.14 (0.26±0.09), 0.36±0.14 (0.24±0.11) for 3-week weight, 6-week weight and 3–6 week gain, respectively. Realised genetic correlations estimated from short-term (long-term) responses were 0.23±0.08 (0.35±0.10) between 3-week weight and 3–6 week gain; 0.82±0.04 (0.58±0.08) between 3-week weight and 6-week weight; and 0.81±0.04 (0.97±0.04) between 3–6 week gain and 6-week weight. The genetic correlation between 3-week weight and 6-week weight was asymmetric with a greater correlated response for 3-week weight when selecting for 6-week weight (1.06) than vice versa (0.63).     

Characterisation of phosphatidylcholine/phosphatidylinositol sonicated vesicles. Effects of phospholipid composition on vesicle size

Phosphatidylinositol (PI), dipalmitoylphosphatidylcholine (DPPC) and mixed lipid (DPPC plus PI) sonicated vesicles have been prepared covering a range of composition. The vesicles were characterised by gel filtration, electron microscopy and photon correlation spectroscopy. The dimensions of the vesicles as measured by electron microscopy were in good accord with those obtained from photon correlation spectroscopy measurements. The number average diameters of the vesicles increase on increasing the PI content and range from approx. 30–80 nm as the weight % of PI is increased from 0 to 100. Gel filtration on Sepharose 4B columns gave anomalous results indicating that PI-containing vesicles were retarded on the gel possibly due to an interaction between the inositol headgroup and the gel matrix. Electrophoretic measurements on multilamellar vesicles show that the surface charge density increases with the PI content of the vesicles upto 50 weight % PI and remains constant thereafter. The radii of sonicated vesicles also increase with PI content which reflects a decreasing liposome curvature with increasing surface charge density.     

On the absence of correlation between cyanide-resistant respiration and cytochrome d content in bacteria

The regularity of appearance of cyanide-resistant respiration and cytochrome d in various bacteria as well as the relationship between the degree of resistance of respiration to cyanide and cytochrome d content was studied. Bacteria able to synthesize cyanide-resistant respiration were shown to appear during transition of culture to the stationary phase of growth caused by the exhaustion of carbon source. No regulatory of appearance of cytochrome d was observed. There is no correlation between the degree of resistance to cyanide and cytochrome d content. It was concluded that the cyanide-resistant respiration of bacteria and eukaryotic microorganisms may be associated with the functioning of a non-cytochrome nature oxidase.     

Correlation of cotylenol with the aglycone of fusicoccin

The stereostructure of cotylenol, the aglycone of the cotylenins, has been confirmed by chemical correlation with the aglycone of fusicoccin A.     

Quasi-elastic light scattering of Artemia ribosomes sedimented in a CsCl density gradient

It is impossible to measure the diffusion coefficient of macromolecules directly and accurately by quasi—elastic light scattering, when aggregates cannot be eliminated from the solutions to be investigated. Nevertheless, a simple method can be applied to overcome this problem in many cases. Aggregates are separated from the monomeric macromolecules by rate-zonal sedimentation in a CsCl density gradient in a transparent centrifugation tube; the monomers are then located by laser light scattering intensity measurements; photon correlation spectroscopy of the scattered light finally yields their diffusion coefficient. The viscosity of aqueous CsCl solutions at different temperatures and concentrations allows a good separation by centrifugation and a low uncertainty in the reduction of the measured diffusion coefficient to standard conditions.The application of the method to eukaryotic large ribosomal subunits is described as an example.     

Alcaloides du Strychnos tchibangensis

The structure of a new bisindole alkaloid has been elucidated by chemical correlation and analysis of ¹³C NMR spectra.     

通风结构林带背风面湍流相关特征初步分析

本文根据湍流统计理论和野外观测数据,详细分析了林带背风面湍流自相关、空间相关和湍流积分尺度特征。在林带背风面的林缘附近,由于湍流尺度较小,使湍流相关系数不紧密。这时的时间尺度在2—3s(1.5m)和3—8s(5m),而空间尺度为10—20m左右。在远离林带以后,林带的作用减弱,随着湍流尺度增大,导致湍流相关系数增大。这时的时间尺度在15—20s,空间尺度在70—80m范围内,且湍流自相关系数服从2/3的指数定律。