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Explained Variance (explained + variance)
Selected AbstractsA latitudinal gradient of beta diversity for exotic vascular plant species in North AmericaDIVERSITY AND DISTRIBUTIONS, Issue 3 2008Hong Qian ABSTRACT Determining relationships between the ranges of introduced species and geographical and environmental factors is an important step in understanding the mechanisms and processes of the spread of introduced species. In this study, I examined the beta diversity and latitude relationship for all naturalized exotic species of vascular plants in North America at a continental scale. Beta diversity was calculated as the absolute value of the slope of the relationship between the natural logarithm of the Simpson index of similarity (lnS) and spatial distance between pairs of state-level exotic floras within four latitudinal zones examined. Relative contributions of spatial distance and environmental difference to species turnover between exotic floras were examined. I found that beta diversity decreased monotonically from low to high latitudes: beta diversity for the southernmost zone was shallower than that for the northernmost zone by a factor of 2.6. Regression models of lnS in relation to spatial distance and environmental (climatic and topographical) difference for each latitudinal zone demonstrated that the explanatory power of these variables diminishes monotonically with latitude: the explained variance in lnS is 70.4%, 62.1%, 53.9%, and 33.9%, respectively, for the four latitudinal zones from south to north. For the southernmost zone, 58.3% of the variance in lnS is explained by climate variables and topography, and spatial distance explains only 2.3% of the variance. In contrast, for the northernmost zone, more than half the amount (22.5%) of the explained variance in lnS is attributable to spatial distance, and the remaining (18.9%) of the explained variance is attributable to climate variables and topography. [source] A latitudinal gradient in large-scale beta diversity for vascular plants in North AmericaECOLOGY LETTERS, Issue 8 2007Hong Qian Abstract Species turnover, or beta diversity, has been predicted to decrease with increasing latitude, but few studies have tested this relationship. Here, we examined the beta diversity,latitude relationship for vascular plants at a continental scale, based on complete species lists of native vascular plants for entire states or provinces in North America (north of Mexico). We calculated beta diversity as the slope of the relationship between the natural logarithm of the Jaccard index (lnJ,) for families, genera or species, and both geographic distance and climate difference within five latitude zones. We found that beta diversity decreased from south to north; within latitude zones, it decreased from species to genera and families. Geographic and climatic distance explained about the same proportion of the variance in lnJ in zones south of c. 50°N. North of this latitude, nearly all the explained variance in lnJ was attributable to geographic distance. Therefore, decreasing beta diversity from south to north reflects decreasing climate differentiation within more northerly latitude zones, and primarily post-glacial dispersal limitation north of 50°N. [source] Catchment urbanisation and increased benthic algal biomass in streams: linking mechanisms to managementFRESHWATER BIOLOGY, Issue 6 2004Sally L. Taylor Summary 1. Urbanisation is an important cause of eutrophication in waters draining urban areas. We determined whether benthic algal biomass in small streams draining urban areas was explained primarily by small-scale factors (benthic light, substratum type and nutrient concentrations) within a stream, or by catchment-scale variables that incorporate the interacting multiple impacts of urbanisation (i.e. variables that describe urban density and the intensity of drainage or septic tank systems). 2. Benthic algal biomass was assessed as chlorophyll a density (chl a) in 16 streams spanning a rural,urban gradient, with both a wide range of urban density and of piped stormwater infrastructure intensity on the eastern fringe of metropolitan Melbourne, Australia. The gradient of urban density among streams was broadly correlated with catchment imperviousness, drainage connection (proportion of impervious areas connected to streams by stormwater pipes), altitude, longitude and median phosphorus concentration. Catchment area, septic tank density, median nitrogen concentration, benthic light (photosynthetically active radiation) and substratum type were not strongly correlated with the urban gradient. 3. Variation in benthic light and substratum type within streams explained a relatively small amount of variation in log chl a (3,11 and 1,13%, respectively) compared with between-site variation (39,54%). 4. Median chl a was positively correlated with catchment urbanisation, with a large proportion of variance explained jointly (as determined by hierarchical partitioning) by those variables correlated with urban density. Independent of this correlation, the contributions of drainage connection and altitude to the explained variance in chl a were significant. 5. The direct connection of impervious surfaces to streams by stormwater pipes is hypothesised as the main determinant of algal biomass in these streams through its effect on the supply of phosphorus, possibly in interaction with stormwater-related impacts on grazing fauna. Management of benthic algal biomass in streams of urbanised catchments is likely to be most effective through the application of stormwater management approaches that reduce drainage connection. [source] Relative influence of variables at multiple spatial scales on stream macroinvertebrates in the Northern Lakes and Forest ecoregion, U.S.A.FRESHWATER BIOLOGY, Issue 8 2003Brian M. Weigel Summary 1We used 94 sites within the Northern Lakes and Forests ecoregion spanning Minnesota, Wisconsin and Michigan to identify environmental variables at the catchment, reach and riparian scales that influence stream macroinvertebrates. Redundancy analyses (RDA) found significantly influential variables within each scale and compared their relative importance in structuring macroinvertebrate assemblages. 2Environmental variables included landcover, geology and groundwater delivery estimates at the catchment scale, water chemistry, channel morphology and stream habitat at the reach scale, and landcover influences at three distances perpendicular to the stream at the riparian scale. Macroinvertebrate responses were characterised with 22 assemblage attributes, and the relative abundance and presence/absence of 66 taxa. 3Each scale defined macroinvertebrates along an erosional to depositional gradient. Wisconsin's macroinvertebrate index of biotic integrity, Ephemeroptera,Plecoptera,Trichoptera taxa and erosional taxa corresponded with forest streams, whereas organic pollution tolerant, Chironomidae and depositional taxa corresponded with wetland streams. Reach scale analyses defined the gradient similarly as dissolved oxygen and wide, shallow channels (erosional) opposed instream macrophytes and pool habitats (depositional). Riparian forests within 30 m of the stream coincided with an erosional assemblage and biotic integrity. 4Next, we combined all significant environmental variables across scales to compare the relative influence of each spatial scale on macroinvertebrates. Partial RDA procedures described how much of the explained variance was attributable to each spatial scale and each interrelated scale combination. 5Our results appeared consistent with the concept of hierarchical functioning of scale in which large-scale variables restrict the potential for macroinvertebrate traits or taxa at smaller spatial scales. Catchment and reach variables were equally influential in defining assemblage attributes, whereas the reach scale was more influential in determining relative abundance and presence/absence. 6Ultimately, comprehending the relative influence of catchment and reach scale properties in structuring stream biota will assist prioritising the scale at which to rehabilitate, manage and derive policies for stream ecosystem integrity. [source] The relationship between local and regional diatom richness is mediated by the local and regional environmentGLOBAL ECOLOGY, Issue 3 2009Sophia I. Passy ABSTRACT Aim, In this continental study, species richness at local (LSR) and regional (RSR) scales was correlated and examined as a function of stream (local) and watershed (regional) environment in an effort to elucidate what factors control diatom biodiversity across scales. Location, Conterminous United States. Methods, Data on diatom richness, stream conditions and watershed properties were generated by the US Geological Survey. In the present investigation, RSR was estimated as the total diatom richness in a hydrologic study unit and, together with stream and watershed characteristics, was included in stepwise multiple regressions of LSR. The unique and shared contributions of RSR, stream and watershed environment to the explained variance in LSR were determined by variance partitioning. RSR was regressed against stream and basin features averaged per study unit. Results, LSR responded most strongly to variability in stream manganese concentration and RSR. Other predictors included stream discharge and iron concentration, soil organic matter content and fertilization, and proportions of open water, barren land and forest in the watershed. Variance partitioning revealed that RSR had the lowest independent contribution to explained variance in LSR. Multiple regressions identified average stream iron concentration as the most important predictor of RSR. Main conclusions, Local micronutrient concentration was the major predictor of LSR, followed by RSR. Since average micronutrient supply in the region was the chief determinant of RSR, it is proposed that micronutrients had both a direct effect on LSR and an indirect effect through RSR. The same argument is extended to watershed features with an impact on stream trophic status, because of their substantial contributions to the explained variance in both LSR and RSR. Considering that the major proportion of LSR variance explained by RSR originated from the covariance of RSR with stream and watershed properties, it is concluded that the LSR,RSR relationship was mediated by the local and regional environment. [source] Measuring consumer perception of product creativity: Impact on satisfaction and purchasabilityHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 3 2009Diana Horn In the current value-based economy, product creativity is a potential resource for organizations to compete, thus emphasizing the need for product creativity measurement. Two studies were performed to refine and validate a previously tested model and measurement of consumer perception of product creativity: one with web-based evaluations (N = 208) of chairs and lamps and one with paper-based evaluations (N = 105) of individually selected products. Results of exploratory factor analyses indicated three main product creativity factors: Affect, Importance, and Novelty, which explained 72% of the common variance. Results of stepwise regressions indicated that the Affect factor significantly predicts (65% of the explained variance) willingness to purchase creative consumer products. One major contribution of this research is the finding that affect is as equally (R2 = .28) important as novelty (R2 = .25) in consumer perception of product creativity. Theoretical and practical implications are discussed for the Affect, Importance, and Novelty product creativity factors, and general creativity guidelines are provided for consumer product design. © 2009 Wiley Periodicals, Inc. [source] Pressure gradient force, atmospheric circulation and climate in western Europe (1899,2002)INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2007Pierre P. Kastendeuch Abstract One mission of synoptic climatology is to quantify the link between atmospheric circulation and surface environment. The pressure gradient force (PGF) is used as a multiple index to summarize the monthly atmospheric circulation for a site in western Europe (5°E and 50°N). The study of the temporal evolution of the PGF components (direction, magnitude, X and Y components) was carried out for the period 1899,2002. The results reflect the variability in atmospheric circulation and reveal some trends. The magnitude of the PGF is particularly affected by several successive periods where the strength of the atmospheric flow was lower (negative trend) or higher (positive trend) than normal. During the last decades of the twentieth century the atmospheric flow appears stronger than before (positive trend), except in summer. As the direction of the PGF can be related to the trajectory of the flow via the Buys,Ballot law, its anomalies are directly related to anomalies in the advection of air masses. No definite trend can be detected for this variable. However, it seems that the northerly flow becomes rare in winter. The relevance of the PGF is also examined with regard to the evolution of monthly temperatures and precipitations via some series of multiple regressions. The best results are obtained for the precipitations, with an explained variance lying between 47 and 73% (respectively in May and February). For temperatures, the explained variance oscillates between 34 and 73% (in September and January). The fact that the meridional and zonal components of the PGF, and the absolute pressure at the site are explicitly taken into account, ensures a good quantification of the atmospheric circulation ,anomalies', that are largely responsible for the annual, seasonal or monthly singularities of temperature and precipitation over western Europe. Copyright © 2007 Royal Meteorological Society [source] Psychometric Correlates of FIRO-B Scores: Locating the FIRO-B scores in personality factor spaceINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 1 2008Adrian Furnham This paper investigated the relationship between the six Fundamental Interpersonal Relations Orientation (FIRO)-B scales, the Big Five Personality traits assessed by the NEO PI-R, the Hogan Development Survey (HDS) and two measures of cognitive ability (Watson Glaser; Graduate and Managerial Assessment). It examined the concurrent and construct validity of the measure in various adult groups attending assessment centres in order to locate the FIRO-B dimensions in established personality factor space. The FIRO-B was consistently correlated with Extraversion, though analysis at the primary factor (facet) level showed many traits from all five factors were strongly correlated with the six FIRO-B scores. Regressing the six FIRO-B facets onto each of the Big Five in turn showed all were significant particularly for Expressed Inclusion and Wanted Control. The second study also showed considerable and logical overlap between the six FIRO-B scales and the 11 dysfunctional personality strategies as measured by the HDS. There were also strong correlational patterns for the Cautious, Reserved, Colourful and Dutiful type disorders. The third study showed the FIRO-B was statistically associated with both cognitive ability tests though it only accounted for small percentages of the explained variance. Expressed Control was the most consistently correlated of the intelligence test scores. Despite the fact that many explicable associations were found between the FIRO-B and other measure the effect sizes were not large. Thus only 4% of the trait facet scores and 4.5% of the HDS showed medium effect sizes. Results are discussed in terms of the usefulness and possible discriminant validity of the instrument for use in selection and assessment. [source] Effects of Trainee Characteristics on Training EffectivenessINTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 2 2007Aharon Tziner Six employee characteristics (conscientiousness, self-efficacy, motivation to learn, learning goal orientation, performance goal orientation, instrumentality) and one work environment characteristic (transfer of training climate) were captured for 130 trainees in a large industrial company in an attempt to predict training effectiveness (training grade, supervisor evaluation of the application of training). The results strongly support the predicted links, although not all the predictor variables contributed a statistically significant share of the explained variance of the training outcomes. Motivation to learn and learning goal orientation were found to contribute most to predicting training outcomes. The implications of the results are discussed and the limitations of the study are noted, along with suggested avenues for future research. [source] Northern Atlantic Oscillation effects on the temporal and spatial dynamics of green spruce aphid populations in the UKJOURNAL OF ANIMAL ECOLOGY, Issue 4 2007SILVERIO SALDAÑA Summary 1The role of climate variability in determining the spatial and temporal patterns of numerical fluctuations is a central problem in ecology. The influence of the North Atlantic Oscillation (NAO) index on the population dynamics and spatial synchrony of the green spruce aphid Elatobium abietinum across the UK was shown. 2Fifteen overlapping time series within the UK were analysed; we used nonparametric models for determining the feedback nonlinear structure and the climatic effects. The spatial synchrony of these populations and the relationship between synchrony and NAO was estimated. 3From the 15 time series across the UK, 11 showed positive and significant NAO effects. In most of the cases the NAO effects were nonlinear showing strong negative effects of low values. The NAO variation improve the explained variance of the first-order feedback models in 14·5%; ranging from 0% to 48%. All data showed strong-nonlinear (concave) feedback structure. In most of the localities the explained variance by the first-order feedback was about 50,60%. 4The spatial synchrony of the per capita growth rates and residuals is high across long distances for those populations affected by NAO. The correlation function predicts a spatial scale of synchrony of about 350,400 km for NAO influenced populations. 5We think that simple population theoretical models describing the link between NAO fluctuations and green spruce aphid dynamics may be fundamental for predicting and simulating the consequences of different climatic scenarios of the future. [source] Quitting Smoking: Applying an Extended Version of the Theory of PlannedBehavior to Predict Intention and Behavior,JOURNAL OF APPLIED BIOBEHAVIORAL RESEARCH, Issue 1 2005Inger Synnøve MOAN This study examined the ability of the theory of planned behavior (TPB)to predict students' intentions to quit smoking and the subsequent behavior6 months later. In addition, the impact of past behavior, moral norms, self-identity, group identity, and positive/negative anticipated affect was examined. The intention-behavior relationship was examined by dividing the sample in four subgroups: inclined actors/abstainers and disinclined actors/abstainers. Analyses were based on data from a prospective sample of 698 smokers. Attitude, subjective norms, and perceived behavioral control accounted for 36% (adjusted R2) of the variance in intentions. Moral norms, positive anticipated affect, group identity, and past behavior added 9% (adjusted R2) to the explained variance in intention, beyond the effect accounted for by the TPB components. Subsequent behavior was predicted by intentions (adjusted R2= .12). Past behavior, moral norms, self-identity, and the Past Behavior x Intention and Moral Norm x Negative Affect interactions explained an additional 9% (adjusted R2) of the variance in behavior. Inclined abstainers constituted the main source of the discrepancy between intention and behavior. [source] Organizational socialization of volunteers: the effect on their intention to remain,JOURNAL OF COMMUNITY PSYCHOLOGY, Issue 5 2009M. Carmen Hidalgo Identifying the factors affecting the retention of volunteers in their activities is one of the main objectives for researchers and volunteer managers. There have been many studies with this aim and many factors affecting sustained volunteerism have been identified. However, one of the limits of these models is the low percentage of explained variance, which indicates that there are other additional factors, yet unidentified, which may have an important influence in the prediction of durability as a volunteer. In our study, we intend to analyze the effect that some factors of organizational socialization of volunteers have on their intention to remain volunteers. In particular, we will focus on the level of integration in the organization, evaluated from five variables: social networks, training, understanding, social support inside the organization, and characteristics of the job they perform. The statistical analysis shows that social networks, organizational support, positive task, and formation are highly significant predictors of the intention to remain a volunteer. These four variables explain 29% of the variability of the dependent variable, while the variables understanding and social support of the volunteers were excluded from the regression equation. © 2009 Wiley Periodicals, Inc. [source] Study on the relations between temperament, aggression, and anger in childrenAGGRESSIVE BEHAVIOR, Issue 3 2006Miguel Ángel Carrasco Ortiz Abstract The present work analyzes the relationships between the dimensions of temperament and the exteriorized emotions of aggression and anger. Temperament was assessed by mothers using the Dimensions of Temperament Survey-Revised, while aggression and anger were self-reported by the children using the Scale of physical and Verbal Aggression and the State,Trait Anger Expression Inventory for Children. The sample studied was made up of 293 children (49.83% boys; 50.17% girls) with a mean age of 11.13 years. The results showed that temperamental difficulties give rise to exteriorized emotions, especially anger. Predictive values of temperament on aggression and anger ranged from 1% to 7% of explained variance. Aggr. Behav. 32:207,215, 2006. © 2006 Wiley-Liss, Inc. [source] PRELIMINARY EVALUATION OF THE APPLICATION OF THE FTIR SPECTROSCOPY TO CONTROL THE GEOGRAPHIC ORIGIN AND QUALITY OF VIRGIN OLIVE OILSJOURNAL OF FOOD QUALITY, Issue 4 2007ALESSANDRA BENDINI ABSTRACT A rapid Fourier transform infrared (FTIR) attenuated total reflectance spectroscopic method was applied to determine qualitative parameters such as free fatty acid (FFA) content and the peroxide value (POV) in virgin olive oils. Calibration models were constructed using partial least squares regression on a large number of virgin olive oil samples. The best results (R2 = 0.955, root mean square error in cross validation [RMSECV] = 0.15) to evaluate FFA content expressed in oleic acid % (w/w) were obtained considering a calibration range from 0.2 to 9.2% of FFA relative to 190 samples. For POV determination, the result obtained, built on 80 olive oil samples with a calibration range from 11.1 to 49.7 meq O2/kg of oil, was not satisfactory (R2 = 0.855, RMSECV = 3.96). We also investigated the capability of FTIR spectroscopy, in combination with multivariate analysis, to distinguish virgin olive oils based on geographic origin. The spectra of 84 monovarietal virgin olive oil samples from eight Italian regions were collected and elaborated by principal component analysis (PCA), considering the fingerprint region. The results were satisfactory and could successfully discriminate the majority of samples coming from the Emilia Romagna, Sardinian and Sicilian regions. Moreover, the explained variance from this PCA was higher than 96%. PRACTICAL APPLICATIONS The verification of the declared origin or the determination of the origin of an unidentified virgin olive oil is a challenging problem. In this work, we have studied the applicability of Fourier transform infrared coupled with multivariate statistical analysis to discriminate the geographic origin of virgin olive oil samples from different Italian regions. [source] Attachment, decay, and social networkJOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 6 2001Ronald S. Burt To study decay in attachment to an organization, I analyse data on women who obtained an MBA from the University of Chicago's Graduate School of Business (GSB). I measure attachment in terms of network embedding: an alumna is attached to the GSB to the extent that people close to her graduated from the GSB. Behavioral data corroborate the network data in that alumnae measured to be more attached are more likely to have joined an alumni club and made a financial contribution to the school. The hypothesis is that alumnae attachment will decay over time, more slowly when the school is deeply embedded in an alumna's network, more quickly when disruptive events compete for the alumna's time and energy. As expected, attachment declines across the years after graduation (linearly for the first 20 years to about half its initial level), and decay is inhibited when connections with GSB graduates are embedded in stable relations of family, work, or long-term friendship. Decay is remarkably robust to events after graduation (which account for only 2 per cent of explained variance in attachment). In other words, an alumna's attachment today was largely determined while she was in school. The results should be of practical value to people who design programmes to build personal attachment to organizations, and of theoretical interest to scholars who study such connections. Copyright © 2001 John Wiley & Sons, Ltd. [source] Validity of Ellenberg indicator values judged from physico-chemical field measurementsJOURNAL OF VEGETATION SCIENCE, Issue 2 2002G.W.W. Wamelink Abstract. The relationship between mean Ellenberg indicator values (IV) per vegetation relevé and environmental parameters measured in the field usually shows a large variation. We tested the hypothesis that this variation is caused by bias dependent on the phytosociological class. For this purpose we collected data containing vegetation relevés and measured soil pH (3631 records) or mean spring groundwater level (MSL, 1600 records). The relevés were assigned to vegetation types by an automated procedure. Regression of the mean indicator values for acidity on soil pH and the mean indicator values for moisture on MSL gave percentages explained variance similar to values that were reported earlier in literature. When the phytosociological class was added as an explanatory factor the explained variance increased considerably. Regression lines per vegetation type were estimated, many of which were significantly different from each other. In most cases the intercepts were different, but in some cases their slopes differed as well. The results show that Ellenberg indicator values for acidity and moisture appear to be biased towards the values that experts expect for the various phytosociological classes. On the basis of the results, we advise to use Ellenberg IVs only for comparison within the same vegetation type. [source] The impact of case specificity and generalisable skills on clinical performance: a correlated traits,correlated methods approachMEDICAL EDUCATION, Issue 6 2008Paul F Wimmers Context, The finding of case or content specificity in medical problem solving moved the focus of research away from generalisable skills towards the importance of content knowledge. However, controversy about the content dependency of clinical performance and the generalisability of skills remains. Objectives, This study aimed to explore the relative impact of both perspectives (case specificity and generalisable skills) on different components (history taking, physical examination, communication) of clinical performance within and across cases. Methods, Data from a clinical performance examination (CPX) taken by 350 Year 3 students were used in a correlated traits,correlated methods (CTCM) approach using confirmatory factor analysis, whereby ,traits' refers to generalisable skills and ,methods' to individual cases. The baseline CTCM model was analysed and compared with four nested models using structural equation modelling techniques. The CPX consisted of three skills components and five cases. Results, Comparison of the four different models with the least-restricted baseline CTCM model revealed that a model with uncorrelated generalisable skills factors and correlated case-specific knowledge factors represented the data best. The generalisable processes found in history taking, physical examination and communication were responsible for half the explained variance, in comparison with the variance related to case specificity. Conclusions, Pure knowledge-based and pure skill-based perspectives on clinical performance both seem too one-dimensional and new evidence supports the idea that a substantial amount of variance contributes to both aspects of performance. It could be concluded that generalisable skills and specialised knowledge go hand in hand: both are essential aspects of clinical performance. [source] Environmental regulation and modelling of cassava canopy conductance under drying root-zone soil waterMETEOROLOGICAL APPLICATIONS, Issue 3 2007Philip G. Oguntunde Abstract Sap flow was measured, with Granier-type sensors, in a crop of field-grown water-stressed cassava (Manihot esculenta Crantz) in Ghana, West Africa. The main objective of this study was to examine the environmental control of canopy conductance (gc) with a view to modelling the stomatal control of water transport under water-stressed condition. Weather variables measured concurrently with sap flow were: air temperature (Ta), relative humidity (RH), wind speed (u) and solar radiation (Rs). Relationship between canopy conductance (gc) and vapour pressure deficit (D,) was curvilinear while no specific pattern was observed with Rs. Average diurnal gc decreased from 3.0 ± 0.6 to 0.7 ± 0.4 mm s,1 between 0730 and 2000 h local time ( = GMT) each day. A Jarvis-type model, based on a set of environmental control functions, was parameterized for the cassava crop in this study. Model results demonstrated that gc was estimated with a high degree of accuracy based on Rs, Ta, and D, (r2 = 0.92;F = 809.2;P < 0.0001). D, explained about 90% (F = 2129.7;P < 0.0001) of the variations observed in gc, whereas both Rs and Ta contributed about 2% of the explained variance in gc. The aerodynamic conductance (ga) was very high compared to gc, leading to a daily average ratio ga/gc > 100 and a decoupling factor < 0.1. Cross-validation analysis revealed a consistent good performance (r2 > 0.85) of the gc model with D, as the only independent environmental variable. Copyright © 2007 Royal Meteorological Society [source] The impact of climate variability on soybean yields in Argentina.METEOROLOGICAL APPLICATIONS, Issue 1 2007Multivariate regression Abstract Climate variability is examined and discussed in this work, emphasizing its influence over the fluctuation of soybean yield in the Pampas (central-eastern Argentina). Monthly data of rainfall, maximum and minimum temperatures, thermal range and seasonal rainfall were analysed jointly with the soybean yield in the period 1973-2000. Low-frequency variability was significant only in the minimum temperature during November in almost all the stations. This situation is favourable to the crop since during this month, seed germination, a growth stage sensitive to low temperatures, takes place. In the crop's core production region, 72% of the series of soybean yield presented a positive trend. Except in years with extreme rainfall situations, interannual variability of the soybean yield is in phase with the seasonal rainfall interannual variability. During these years, losses in the soybean crop occurred, with yield negative anomalies greater than one standard deviation. Soybean yield showed spatial coherence at the local scale, except in the crop's core zone. The association between each climate variable and yield did not show a defined regional pattern. Summer high temperature and rainfall excesses during the period of maturity and harvest have the greatest negative impact on the crop, whilst higher minimum temperatures during the growing season favour high yields. The joint effect of climate variables over yield was studied with multivariate statistical models, assuming that the effect of other factors (such as soil, technology, pests) is contained in the residuals. The regression models represent the estimates of the yield satisfactorily (high percentage of explained variance) and can be used to assess expected anomalies of mean soybean yield for a particular year. However, the predictor variables of the yield depend on the region. Copyright © 2007 Royal Meteorological Society [source] Predictability of plant species composition from environmental conditions is constrained by dispersal limitationOIKOS, Issue 3 2005Wim A. Ozinga Despite recent modelling approaches integrating the effects of niche-based processes and dispersal-based processes on local plant species composition, their relative importance is still not clear. We test whether the predictability of local species composition from environmental conditions is influenced by dispersal traits. We analyzed a large database with co-occurrence data, using ordination techniques (DCA and CCA) to identify the major environmental determinants of species composition. The percentage of explained variance in occurrence was quantified for individual species with CCA. Effects of life-history traits on the predictability of occurrence patterns were tested by means of regression analysis, using a generalized linear models approach. The results reveal close correlations between species composition and environmental conditions, implying that the predictability of the set of species that might occur in a given environmental setting ("habitat species pool") is high. The habitat species pool, however, reflects the potential species composition, and not the actual local situation. At the level of individual species, a large proportion (>90%) of the variation in occurrence remained unexplained. Predictability of species occurrence patterns was increased by a greater capacity for long-distance dispersal, greater adult longevity and the capacity to build a persistent seed bank. The results indicate that the predictability of species composition from environmental conditions is reduced by a few orders of magnitude by dispersal limitation and that poor dispersers are underrepresented. [source] Case Management Relationships and a Recovery Orientation: A Consumer Survey of Class Members in the Arnold CaseAMERICAN JOURNAL OF ORTHOPSYCHIATRY, Issue 3 2010José B. Ashford The purpose of this study was to examine the relative contributions of the working alliance in predicting a recovery orientation. An additional aim was to determine whether a measure of case management fairness contributed any additional proportion of explained variance in a recovery orientation beyond what is accounted for by the working alliance. The study blended structured interview and clinical judgment measures with survey research methods to obtain data about consumer relationships with their case managers, as well as their recovery attitudes. The sample consisted of (N = 167) priority-class members involved in the Arnold v. Arizona Department of Health Services class-action lawsuit in Maricopa County, Arizona. The results showed that the working alliance and case management fairness variables accounted for more of the explained variance in a recovery orientation, than any of the other known correlates of recovery. The results also provided some preliminary support for the inclusion of case management fairness as a predictor variable of a recovery orientation, in that the study's measure of case management fairness contributed a small proportion of additional variance beyond what was explained by the working alliance in predicting a dimension of a recovery orientation. The implications of the study's findings for practice and future research are discussed. [source] Variability explained by covariates in linear mixed-effect models for longitudinal dataTHE CANADIAN JOURNAL OF STATISTICS, Issue 3 2010Bo Hu Abstract Variability explained by covariates or explained variance is a well-known concept in assessing the importance of covariates for dependent outcomes. In this paper we study R2 statistics of explained variance pertinent to longitudinal data under linear mixed-effect models, where the R2 statistics are computed at two different levels to measure, respectively, within- and between-subject variabilities explained by the covariates. By deriving the limits of R2 statistics, we find that the interpretation of explained variance for the existing R2 statistics is clear only in the case where the covariance matrix of the outcome vector is compound symmetric. Two new R2 statistics are proposed to address the effect of time-dependent covariate means. In the general case where the outcome covariance matrix is not compound symmetric, we introduce the concept of compound symmetry projection and use it to define level-one and level-two R2 statistics. Numerical results are provided to support the theoretical findings and demonstrate the performance of the R2 statistics. The Canadian Journal of Statistics 38: 352,368; 2010 © 2010 Statistical Society of Canada La variation expliquée par les covariables (ou la variance expliquée) est un concept bien connu pour mesurer l'importance de ces covariables sur la variable dépendante. Dans cet article, nous étudions la statistique du R carré pour la variance expliquée pertinente aux données longitudinales pour des modèles linéaires à effets mixtes. La statistique du R carré est calculée à deux niveaux différents pour mesurer la variation expliquée par les covariables à l'intérieur et entre les sujets. En obtenant des limites aux statistiques du R carré, nous trouvons que l'interprétation de la variance expliquée pour les statistiques du R carré existantes est claire seulement dans le cas où la matrice de variance-covariance des observations dépendantes est symétrique composée. Deux nouvelles statistiques du R carré sont proposées afin de prendre en compte les effets des moyennes des covariables pouvant dépendre du temps. Dans le cas général où la matrice de variance-covariance des observations n'est pas symétrique composée, nous introduisons le concept de projection symétrique composée et nous l'utilisons pour définir les statistiques du R carré de niveaux 1 et 2. Des résultats numériques appuient nos résultats théoriques et ils montrent la performance des statistiques du R carré. La revue canadienne de statistique 38: 352,368; 2010 © 2010 Société statistique du Canada [source] Response of pine natural regeneration to small-scale spatial variation in a managed Mediterranean mountain forestAPPLIED VEGETATION SCIENCE, Issue 4 2009Ignacio Barbeito Abstract Questions: What influence do management practices and previous tree and shrub stand structure have on the occurrence and development of natural regeneration of Pinus sylvestris in Mediterranean mountain forests? How are the fine-scale and environmental patterns of resources affected and what impact does this have on the distribution of the regeneration? Location: A Pinus sylvestris Mediterranean mountain forest in central Spain. Methods: Upperstory trees and regeneration (seedlings and saplings) were mapped in four 0.5-ha plots located in two types of stand with different management intensities (even-aged and uneven-aged stands). Environmental variables were recorded at the nodes of a grid within the plots. The relationships between the upperstory and regeneration were evaluated by bivariate point pattern analysis; redundancy analysis ordination and variation partitioning were performed to characterize regeneration niches and the importance of the spatial component. Results: Seedlings and saplings presented a clumped structure under both types of management and their distribution was found to be related to the spatial distribution of favourable microsites. Regeneration was positively related to conditions of partial cover with high soil water content during the summer. More than half of the explained variance was spatially structured in both types of stand. This percentage was particularly high in the even-aged stands where the pattern of regeneration was highly influenced by the gaps created by harvesting. Conclusions: The spatial distribution of the tree and shrub upperstory strongly influences regeneration patterns of P. sylvestris. Current management practices, promoting small gaps, partial canopy cover and moderate shade in even-aged stands, or favouring tree and shrub cover in the case of uneven-aged stands, appears to provide suitable conditions for the natural regeneration of P. sylvestris in a Mediterranean climate. [source] Sense of coherence and social support predict living liver donors' emotional stress prior to living-donor liver transplantationCLINICAL TRANSPLANTATION, Issue 3 2008Yesim Erim Abstract:, The protection of the donors from physical or emotional harm has been a fundamental principle in living-donor liver donation from the beginning. Psychosomatic donor evaluation aims at the selection of eligible donors and the screening and exclusion of psychiatrically vulnerable donors. As clinical interviews may include subjective biases, efforts should be made to establish objective criteria for donor assessment. In recent research, protective factors have been reported to be a significant force behind healthy adjustment to life stresses and can be investigated as possible predictors of donors' eligibility. Being the central construct of Antonovsky's theory of salutogenesis, the sense of coherence is one of the most surveyed protective factors and a good predictor of individuals' stability when experiencing stress. Furthermore, family support has been shown to be a valuable protective resource in coping with stress. This study surveyed whether sense of coherence and social support predict donors' emotional strain prior to transplantation. Seventy-one donor candidates were included in the study during the donor evaluation prior to living-donor liver transplantation. Sense of coherence proved to be a significant predictor for all criterion variables, namely anxiety, depression and mental quality of life. In addition to this, donor candidates who were classified as eligible for donation in the psychosomatic interview had significantly higher values on sense of coherence total scores compared with rejected donors. In a multiple regression analysis, sense of coherence and social support together yielded a prediction of depression with an explained variance of 22% (R2 = 0.22). Sense of coherence and social support can be implemented as self-rating instruments in the psychosomatic selection of donors and would help to further objectify donors' eligibility. [source] SENSORY QUALITY CRITERIA FOR FIVE FISH SPECIES PREDICTED FROM NEAR-INFRARED (NIR) REFLECTANCE MEASUREMENTJOURNAL OF FOOD QUALITY, Issue 5 2001KARIN WARM ABSTRACT Sensory profiling and Near-Infrared (NIR) reflectance analysis were carried out on cod (Gadus morhua), saithe (Pollachius virens), rainbow trout (Salmo gardineri), herring (Clupea harengus) and flounder (Platichthys flessus). A nine-member trained panel performed the profiling on cooked fillet samples and NIR was measured on the same material as whole, raw fish and raw fillet. For each species, samples varied in storage time (1,11 days in ice at OC) and season (spring, autumn and winter). One descriptive vocabulary was developed, containing 46 descriptive words altogether: 7 for appearance, 15, odor, 16, taste and 8 texture words. Multivariate data analysis was used to reduce the 46 words to 18, covering the main systematic variations in appearance, odor, taste and texture in conformance with a previous study. The same 18 sensory attributes were modeled by NIR measurements on whole, new fish and fillet. The predictive results showed explained variances to be higher for appearance and texture rhan for odor, and lowest for taste. The results indicate that NIR spectroscopy of raw fish as a supplement to sensory analysis might be useful as a rapid tool in Quality Monitoring for measuring the sensory parameters of appearance and texture of cooked fish. [source] | |||||||||||||||||||||||||