Similar Environmental Variables Research Articles

Evaluating Electricity Distributors Efficiency Using Self-Organizing Map and Data Envelopment Analysis

This paper presents an alternative approach to the one developed by the Brazilian National Agency of Electric Energy (ANEEL) for analysis of efficient operating costs of electricity distributors. The approach adopted by the agency clusters distributors by the magnitude of the market, applying an input-oriented Data Envelopment Analysis (DEA) model in two stages in which the second phase is used to adjust the efficiency considering environmental variables of each concession area. The aim of this paper is to use Self-Organizing Map (SOM) for grouping the distributors with similar environmental variables of the concession areas and later, to assess the distributors efficiency, through the same first stage DEA model performed by ANEEL. This approach eliminates the DEA second stage procedure, presenting a new way of analyzing distributors efficiencies.

Widespread native and alien plant species occupy different habitats

Theories to explain the success of alien species often assume that they are inherently different from native species. Although there is an increasing body of evidence showing that alien plants tend to dominate in highly human‐modified environments, the underlying reasons why widespread natives might differ in their habitat distribution have rarely been addressed. We used species distribution models to quantify the dominant environmental axes shaping the habitat of 95 widespread native and alien herbaceous species in a highly modified grassland‐dominated landscape in New Zealand. For each species, support vector machines were used to determine 1) the environmental variables that most strongly determined a species’ distribution; 2) the affinity towards a particular position along environmental axes; and 3) tolerance to environmental variation. These three measures were compared among native perennials (n = 31), alien perennials (30) and alien annuals (34). Independent of their origin, species’ distributions were defined by similar environmental variables. Nevertheless, native and alien species occupied different regions of the dominant environmental axes. Perennial natives occupied regions associated with lower human disturbance, while perennial aliens were associated with habitats that had been modified by vegetation clearance, pasture development and livestock grazing. Annual aliens differed from perennials and were associated with both semi‐natural and more intensively managed vegetation. No evidence was found that aliens had broader environmental tolerances than natives that might facilitate invasion into a wider range of environments. Thus, widespread native and alien species differ in the degree to which environmental factors shape their distribution as a result of anthropogenic perturbations to which they respond differently as well as the introduction of functional groups that are capable of exploiting novel environments.

Differences in benthic diatom assemblages between streams and lakes in Sweden and implications for ecological assessment

Benthic diatom assemblages from 179 streams and 98 lakes in Sweden were compared to identify differences in taxonomic composition, growth form, cell size, diversity and richness, and ultimately, to assess the effects of differences between streams and lakes on assessments. Streams and lakes with similar environmental background variables were chosen to avoid an overriding effect of factors, such as nutrients and pH, on taxonomic composition. Generic and species composition differed significantly between streams and lakes. Richness was significantly higher in lakes than in streams, and the average diatom cell was significantly longer in streams than in lakes. No other measures analyzed differed significantly. Diatom assemblages in both habitats were related to pH and nutrients, and the diatom indices studied responded similarly to the main environmental gradients in both habitats. Thus, despite differences in taxonomic composition between streams and lakes, the resulting diatom assemblages are similar, enabling use of the same diatom indices in both habitats.

Autoecological Approaches to Resolve Subjective Taxonomic Divisions within Arcellacea

Arcellacea (testate lobose amoebae) are important lacustrine environmental indicators that have been used in paleoclimatic reconstructions, assessing the effectiveness of mine tailings pond reclamation projects and for studying the effects of land use change in rural, industrial and urban settings. Recognition of ecophenotypically significant infra-specific 'strains' within arcellacean assemblages has the potential to enhance the utility of the group in characterizing contemporary and paleoenvironments. We present a novel approach which employs statistical tools to investigate the environmental and taxonomic significance of proposed strains. We test this approach on two identified strains: Difflugia protaeiformis Lamarck strain 'acuminata' (DPA), characterized by fine grained agglutination, and Difflugia protaeiformis Lamarck strain 'claviformis' (DPC), characterized by coarse grained agglutination. Redundancy analysis indicated that both organisms are associated with similar environmental variables. No relationship was observed between substrate particle size and abundance of DPC, indicating that DPC has a size preference for xenosomes during test construction. Thus DPC should not be designated as a distinct strain but rather form a species complex with DPA. This study elucidates the need to justify the designation of strains based on their autecology in addition to morphological stability.

Genotype by environment interaction for post-weaning weight gain, scrotal circumference, and muscling score of composite beef cattle in different regions of Brazil.

The objectives of this study were to characterize and define homogenous production environments of composite beef cattle in Brazil in terms of climatic and geographic variables by using multivariate exploratory techniques; to evaluate the presence of genotype by environment interaction (GxE) for post-weaning weight gain (PWG), yearling scrotal circumference (SC), and yearling muscling (MUS). Hierarchical and nonhierarchical cluster analysis was used to group farms located in regions with similar environmental variables into clusters. Six clusters of farms were formed. The effect of sire-cluster interaction was tested by single-trait analysis. Genetic parameters were estimated by multi-trait analysis considering the same trait to be different in each cluster. The effect of sire-cluster interaction was significant (P <0.01) for PWG and MUS. Estimates of genetic correlations among clusters ranged from 0.31 to 0.93 for PWG, 0.64 to 0.89 for SC, and 0.18 to 0.80 for MUS. These results indicate the need for a genetic analysis on a regional basis or inclusion of the GxE effect in the statistical model to permit appropriate evaluation of the animals.

Exotic Plants of Halimun Salak Corridor: Micro-Environment, Detection and Risk Analysis of Invasive Plants

The research of exotic plant species detection and invasive plant risk analysis conducted in Halimun Salak corridor area. This study aims to do inventory of exotic plant species in this area and perform invasive plant risk analysis to the exotic plants found. The invasion risk assessment of detected exotic plants analyzed using Weed Risk Assessment (WRA) method. Moreover, analysis of multi-dimensional scaling (MDS) based on inequality performed on relative humidity, light intensity, and soil pH. There are eleven exotic plant species which consist of three tree species and eight species of herbs / shrubs. Lantana camara and Camellia sinensis are the exotic species with biggest and smallest WRA score respectively. MDS analysis shows that exotic tree species have similar environmental variables. Moreover, environmental variables of Clidemia hirta are relatively different from other exotic species found in the Halimun Salak corridor.Recommendations for the management of invasive exotic plant species in the area are: immediate management implementation, priority of eradication to exotics that have not been abundant but have a high risk score, two management options (gradual eradication or containment) should be considered for exotics with very high WRA score such as Ageratina riparina, Chromolaena odorata and Lantana camara.

An inter-catchment comparison of groundwater biota in the cotton-growing region of north-western New South Wales

Groundwater is essential to crop production in many parts of the world, and the provision of clean groundwater is dependent on healthy groundwater ecosystems. To understand better the functioning of groundwater ecosystems, it is necessary to understand how the biota responds to environmental factors, and so distinguish natural variation from human induced changes. This study compares the groundwater biota of the adjacent Gwydir and Namoi River alluvial aquifers, both in the heartland of Australia’s cotton industry, and investigates the relative importance of environmental, anthropogenic, geological, and evolutionary processes on biotic distribution. Distinct differences in biotic assemblages were recorded between catchments at a community level. However, at a functional level (e.g. microbial activity, stygofauna abundances and richness) both ecosystems were similar. The distribution of biota in both catchments was influenced by similar environmental variables (e.g. geology, carbon availability, season, and land use). Broad trends in biotic distribution were evident: stygofauna responded most strongly to geological variables (reflecting habitat) and microbes to water quality and flow. Agricultural activities influenced biota in both catchments. Although possessing different taxa, the groundwater ecosystems of the two aquifers were functionally similar and responded to similar environmental conditions.

Is coarse taxonomy sufficient for detecting macroinvertebrate patterns in floodplain lakes?

Taxonomic sufficiency (TS) — defined as the minimum taxonomic detail required to discern some ecological pattern of interest — has been used extensively in bioassessment and biodiversity studies as a way of avoiding a portion of the time and monetary costs associated with species diagnoses. The taxonomic sufficiency for detecting species-level patterns among floodplain-lake benthic-invertebrate assemblages remains unexplored. We examined cross-taxonomic-level congruence in assemblage-environment relationships among 23 Chinese floodplain lakes. Our objectives were: (1) to compare the correlation between species richness and density and those at coarser taxonomic resolution; (2) to identify whether assemblage-environment relationships depend on taxonomic scale; and (3) to test whether the proportion of between-lake variability accounted for by environmental variables was independent of taxonomic scale. When taxonomic structure was described using sequentially coarser taxonomic aggregations, species-level patterns of richness and abundance were sequentially obscured (i.e., genus-level taxonomy best preserved patterns in species composition, order- and class-level taxonomy poorly represented species composition). Similar environmental variables were important for distinguishing lake species assemblages and genus assemblages; however, different environmental variables were important for describing family-, order-, and class-level assemblage patters. Moreover, environmental variables accounted for a similar amount of biological variability, regardless of taxonomic scale. Our results suggest genus taxonomy as sufficient for rapid assessments of lake diversity. Numerical dominance of the species- and genus-rich Chironomidae, Tubificidae, and Naididae, may account for the marked loss of information that occurs when lake invertebrates are assigned only to their families. In summary, we describe taxonomic sufficiency to detecting patterns of richness and abundance among subtropical lake macroinvertebrate faunas. This study will interest Chinese benthologists concerned with conservation and bioassessment.

Using functional approaches to study phytoplankton communities in a temperate region exposed to tropical species dispersal

Functional characteristics play an important role in shaping phytoplankton distributions. This approach can help to explain the success of tropical taxa in temperate ecosystems. We used functional groups (FG) and functional traits (FT) to assess the phytoplankton distribution in five temperate lakes exposed to tropical taxa dispersal. We ran redundancy analyses to assess the relationship between each functional classification and the environment. Both approaches showed similar variance of the phytoplankton biomass and responded to similar environmental variables. The FG approach separated lakes by trophic status (total phosphorus: TP), while the FT approach reflected the lakes’ hydromorphology (conductivity, depth, mixing regime). The traits of motility and mixotrophy coincided with low mixing and high light. Tropical taxa were dominant in two lakes, rare in one and absent in two lakes. When dominant, tropical taxa exerted an overwhelming effect on phytoplankton biomass and community composition, and contributed to foam occurrences. The success of tropical taxa in only two lakes seems related to the interplay of their traits (accessory pigments, morphology) and the prevailing environmental filters (low light, deep mixing, and intermediate TP). Their rarity or absence in the other lakes evidences how traits can increase fitness in one environment but not in other.

Genotype by environment interaction for birth and weaning weights of composite beef cattle in different regions of Brazil

The objectives of the present study were to characterize and define homogenous production environments of composite beef cattle in Brazil in terms of climatic and geographic variables using multivariate exploratory techniques and to use them to assess the presence of G×E for birth weight (BW) and weaning weight (WW). Data from animals born between 1995 and 2008 on 36 farms located in 27 municipalities of the Brazilian states were used. Fifteen years of climate observations (mean minimum and maximum annual temperature and mean annual rainfall) and geographic (latitude, longitude and altitude) data were obtained for each municipality where the farms were located for characterization of the production environments. Hierarchical and nonhierarchical cluster analysis was used to group farms located in regions with similar environmental variables into clusters. Six clusters of farms were formed. The effect of sire–cluster interaction was tested by single-trait analysis using deviance information criterion (DIC). Genetic parameters were estimated by multi-trait analysis considering the same trait to be different in each cluster. According to the values of DIC, the inclusion of sire–cluster effect did not improve the fit of the genetic evaluation model for BW and WW. Estimates of genetic correlations among clusters ranged from −0.02 to 0.92. The low genetic correlation among the most studied regions permits us to suggest that a separate genetic evaluation for some regions should be undertaken.

Hierarchical Bayesian Spatial Models for Multispecies Conservation Planning and Monitoring

Biologists who develop and apply habitat models are often familiar with the statistical challenges posed by their data's spatial structure but are unsure of whether the use of complex spatial models will increase the utility of model results in planning. We compared the relative performance of nonspatial and hierarchical Bayesian spatial models for three vertebrate and invertebrate taxa of conservation concern (Church's sideband snails [Monadenia churchi], red tree voles [Arborimus longicaudus], and Pacific fishers [Martes pennanti pacifica]) that provide examples of a range of distributional extents and dispersal abilities. We used presence-absence data derived from regional monitoring programs to develop models with both landscape and site-level environmental covariates. We used Markov chain Monte Carlo algorithms and a conditional autoregressive or intrinsic conditional autoregressive model framework to fit spatial models. The fit of Bayesian spatial models was between 35 and 55% better than the fit of nonspatial analogue models. Bayesian spatial models outperformed analogous models developed with maximum entropy (Maxent) methods. Although the best spatial and nonspatial models included similar environmental variables, spatial models provided estimates of residual spatial effects that suggested how ecological processes might structure distribution patterns. Spatial models built from presence-absence data improved fit most for localized endemic species with ranges constrained by poorly known biogeographic factors and for widely distributed species suspected to be strongly affected by unmeasured environmental variables or population processes. By treating spatial effects as a variable of interest rather than a nuisance, hierarchical Bayesian spatial models, especially when they are based on a common broad-scale spatial lattice (here the national Forest Inventory and Analysis grid of 24 km(2) hexagons), can increase the relevance of habitat models to multispecies conservation planning.

Ecological validity and risk assessment: the importance of assessing context for intellectually disabled sexual offenders

In psychological testing, the term ‘ecological validity’ (EV) refers to the degree to which a test assesses (or estimates) via a proxy task a person's ability to do a ‘real‐life’ task. While EV has been a critical evaluative component of some areas of psychological testing, it has not featured to date as important in the area of risk assessment. If the goal of risk assessment is to enhance risk management, then this is a critical oversight. It would appear that all forms of risk assessment measures are lacking EV. EV is important because risk management occurs in the community. The ARMIDILO is mentioned as an instrument that has attempted to include environmental variables to enhance EV and thus facilitate the risk manageability of ID sex offenders. It is proposed that the EV of other risk measures could be enhanced by the inclusion of similar environmental variables.

Statistical analysis and modeling of precipitation data

The objective of the present paper is to perform statistical analysis and modeling of actual precipitation data collected in 20 stations in Greece. Although our analysis and statistical modeling procedure utilizes precipitation data from Greece, the same methodology can be applied to similar data or other environmental variables. We identify the probability density function (PDF) that best characterizes the behavior of the data, that being the Frechet PDF, a member of the family of the Generalized Extreme Value (GEV) family of distributions. In addition to obtaining useful information, such as the expected rainfall along with its variance and confidence limits, we are able to cluster the stations into 7 groups that have similar response. Furthermore, we introduce time dependence into the Frechet probability distribution by characterizing the location and scale parameters to be functions of time and other well known, but more complex covariates such as the North Atlantic Oscillation index. This approach enables a more flexible and realistic model to quantify the uncertainty inherent into the system, and allows for more complex dependence patterns.

Predicting the decline in daily maximum transpiration rate of two pine stands during drought based on constant minimum leaf water potential and plant hydraulic conductance

The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative decline in daily maximum transpiration rate with decreasing soil water content is relatively straightforward. We constructed a soil-plant water flow model assuming constant plant conductance and daily minimum leaf water potential, but variable conductance from soil to root. We tested this model against independent data from two sites: automatic shoot chamber data and sap flow measurements from a boreal Scots pine (Pinus sylvestris L.) stand; and sap flow measurements from a maritime pine (Pinus pinaster Ait.) stand. To focus on soil limitations to water uptake, we expressed daily maximum transpiration rate relative to the rate that would be obtained in wet soil with similar environmental variables. The comparison was successful, although the maritime pine stand showed carry-over effects of the drought that we could not explain. For the boreal Scots pine stand, daily maximum transpiration was best predicted by water content of soil deeper than 5 cm. A sensitivity analysis revealed that model predictions were relatively insensitive to the minimum leaf water potential, which can be accounted for by the importance of soil resistance of drying soil. We conclude that a model with constant plant conductance and minimum leaf water potential can accurately predict the decline in daily maximum transpiration rate during drought for these two pine stands, and that including further detail about plant compartments would add little predictive power, except in predicting recovery from severe drought.

Environmental correlates of species and genetic richness in lungless salamanders (family plethodontidae)

Abstract Biological diversity is distributed across the planet in non-random, organised ways. At the species level, numerous environmental variables have been proposed to explain this non-random distribution with available energy and habitat heterogeneity receiving the most empirical support. With regard to genetic organisation, environmental stress and habitat heterogeneity have been widely supported. However, few studies have addressed if these two scales of biological organisation are structured via similar processes. Here, we tested whether or not the distributional organisation of genetic and species richness were driven by similar environmental variables for salamanders of the family Plethodontidae across North America. In general, we found that those environmental variables related to energy, particularly energy made accessible to salamanders via the actions of available moisture, were the primary determinants of both genetic and species richness. This finding is consistent with both the “more individuals hypothesis” of species richness and neutral-theory expectations for genetic richness. Additionally, greater habitat heterogeneity, as measured by increased topographic variance, was of secondary importance in positively influencing species richness, although its effects on genetic richness were far more variable. In total, our results suggest that both of these scales of biological organisation are influenced by similar environmental variables, even though increased genetic richness at the population-level does not always translate into greater species richness.

Using Partial Least Squares Regression, Factorial Regression, and AMMI Models for Interpreting Genotype × Environment Interaction

Partial least squares (PLS) and factorial regression (FR) are statistical models that incorporate external environmental and/or cultivar variables for studying and interpreting genotype × environment interaction (GEl). The Additive Main effect and Multiplicative Interaction (AMMI) model uses only the phenotypic response variable of interest; however, if information on external environmental (or genotypic) variables is available, this can be regressed on the environmental (or genotypic) scores estimated from AMMI and superimposed on the AMMI biplot. The objectives of this study with two wheat [Triticum turgidum (L.) var. durum] field trials were (i) to compare the results of PLS, FR, and AMMI on the basis of external environmental (and cultivar) variables, (ii) to examine whether procedures based PLS, FR, and AMMI identify the same or a different subset of cultivar and/or environmental covariables that influence GEI for grain yield, and (iii) to find multiple FR models that include environmental and cultivar covariables and their cross products that explain a large proportion of GEI with relatively few degrees of freedom. Results for the first trial showed that AMMI, PLS, and FR identified similar cultivar and environmental variables that explained a large proportion of the cultivar × year interaction. Results for the second wheat trial showed good correspondence between PLS and FR for 23 environmental covariables. For both trials, PLS and FR complement each other and the AMMI and PLS biplots offered similar interpretations of the GEl. The FR analysis can be used to confirm these results and to obtain even more parsimonious descriptions of the GEL

Fiber-Optic-Based Sensing of Banded Luminescence in Corals

Ultraviolet irradiation of a sectional slice of the aragonitic skeleton cut along the growth axis of coral colonies reveals a series of alternating luminescent bands, the intensity of which appears to be related to environmental conditions at the former growth surface of the colony. Studies of the patterns of annual density banding in coral skeletons, as revealed by X-ray radiography, have been used in much the same way that growth rings in trees are used to provide indications of past environmental conditions. A second class of studies on coral skeletons attempts to quantify chemical and isotopic markers which are included within the calcium carbonate matrix to similar known climatic or environmental variables. The luminescence signal is generally believed to arise from the skeletal inclusion of varying amounts of naturally fluorescent dissolved organic matter (DOM) chromophores present in seawater. In particular, it has been argued that the fluorescent banding observed in corals found growing adjacent to coastal regions impacted by periodic discharge of terrestrially derived fluorescent humic and fulvic acids may thus be used as a proxy for past river discharge and, hence, past rainfall. It may be noted, however, that other components of calcium carbonate matrices, e.g., impurity Mn2+ may contribute to some of the total observed luminescence signal.

Population structure and growth-stress relationship ofPinus taedain rock outcrop habitats

Abstract. On the granite outcrops of the southeastern United States, soil accumulates in shallow depressions on the rock surface. A specific sequence of vascular plants characterizes the temporal development of these systems. The edaphic end point of the succession is apparently attained with a herb-shrub-tree stage with Pinus taeda as the dominant tree. We studied the characteristics of this stage and the population structure of P. taeda on outcrop islands in order to specify the successional status of the species in this habitat. We compared the radial growth pattern of outcrop and Piedmont populations of P. taeda, and of two outcrop sub-populations. We checked whether trees on outcrops experience more limiting conditions than trees on the Piedmont, and studied the recent change in the relationship between growth and stress (e.g. drought and atmospheric deposition) reported for loblolly pine in the southeastern United States. We also attempted to identify the climatic variables most critical for tree growth on outcrops. On outcrop soil islands, P. taeda maintains populations that are of irregular age distribution, possibly in response to irregular recruitment and survival. There are no signs of loblolly pine replacement by hardwood species on any of the islands studied, although an understory of shrubby oak appears to characterize larger and deeper-soil islands. Although trees on the Piedmont were growing at a higher rate than those on the outcrop in the first part of the 1950–1988 period, their growth declined at a higher rate than that of trees on the outcrop. As a result, at the end of the period considered (1950–1988), the differences in radial growth between outcrop and Piedmont populations were relatively small. On the outcrop, trees < 22 yr old in 1989 were growing at a rate somewhat lower than that of trees of similar age, 40 yr ago. Differences were apparent in the initial growth patterns between the two outcrop subpopulations (1989 and 1949 stems), and these could have resulted from differences in competition regime, stress or climatic conditions, or a combination thereof. However, a repeated-measures ANOVA failed to reveal a significant recent decrease in the radial growth of loblolly pine in the system studied. The identification of numerous signature years (years with ≥ 80 % of the trees with similar increasing or decreasing trend in their radial growth) suggests that similar environmental variables control the growth of loblolly pine in both outcrop and Piedmont habitats. High temperature and low precipitation in the first part of the summer (June-July) seem to limit radial growth. Those pines growing on outcrop soil islands, however, appear more sensitive to climatic fluctuations.

Behavioral correlates of non-random mortality among free-ranging female vervet monkeys

Over a 3.5 year period, illness and predation operated in a non-random manner on free-ranging vervet monkeys in Amboseli National Park. As a result, there was no correlation among adult females between dominance rank and reproductive success. Deaths due to illness were concentrated among low-ranking individuals, and appeared to occur as a result of restricted access to food and water during the dry season. In contrast, deaths due to predation were concentrated among high-ranking individuals. The precise cause of such increased vulnerability could not be determined. High-ranking females alarm-called at higher frequencies than low-ranking females, and were also more aggressive than low-ranking females during intergroup encounters. In contrast, low-ranking females were more likely to initiate friendly interactions with the members of other groups. The non-random distribution of causes of mortality suggests that individuals living in the same social group may confront different selective pressures. Perhaps as a result, individuals appear to respond differently to similar social and environmental variables.