Related Environmental Variables Research Articles

DISTRIBUTION OF FORAMINIFERA IN THE SETIU ESTUARY AND LAGOON, TERENGGANU, MALAYSIA

The Setiu wetland of peninsular Malaysia is threatened by expansion of aquaculture. Water quality of the estuary-lagoon complex is becoming affected by nutrients introduced into the system at floating fish cages and by the clear-cutting of large areas of fringing mangrove forest for the creation of land-based fish and shrimp pens. We report here on the distribution of benthic foraminifera in the estuary-lagoon and related environmental variables. These data will form the baseline against which future environmental monitoring will be compared. Four thanatofacies are recognized by cluster analysis of the dead foraminiferal abundance data; their distribution is closely related to variations in salinity and other parameters related to the hydrodynamics of the region. This relation is confirmed by DCA and DCCA analyses. A low salinity estuarine thanatofacies (D1) has a low diversity assemblage dominated by the agglutinated taxa Ammotium directum , Trochammina amnicola , Miliammina fusca and Ammobaculites exiguus. A medium salinity lagoon thanatofacies (D2) has low diversity and is strongly dominated by the agglutinated Ammobaculites exiguus. Ammobaculites exiguus and Ammonia aff. A. aoteana dominate a high diversity, high salinity thanatofacies (D3) in both the estuary and the lagoon. A normal marine salinity thanatofacies (D4), found at an inlet and in the immediately adjacent lagoon, has a high diversity assemblage dominated by the calcareous taxa Amphistegina lessonii and Ammonia aff. A. aoteana . Five biofacies recognized by cluster analysis of live foraminiferal data exhibit similar salinity-related distribution patterns as the thanatofacies.

Road effects on vegetation composition in a saline environment

Aims Road effects from maintenance and traffic have the potential to alter plant communities, but the exact relationships between these effects and changes in plant community composition have not often been studied in diverse environments. To determine the direction and level of community composition changes in saline environment due to road effects, we conducted a study along roads of different ages and in nearby non-road (i.e. natural) areas in the Yellow River Delta, China. Additionally, to potentially elucidate the mechanisms underlying the changes in the richness and composition of plant communities along roads, we evaluated physiochemical changes in soil of roadside and non-road areas. Methods Floristic and environmental data were collected along roadside of different ages and nearby non-road areas. To evaluate plant communities at each site, six 2 m 3 2 m quadrats were placed at 3-m intervals along roads and six quadrats were arranged randomly in non-road areas. To determine the difference in plant community composition between roadside and non-road areas, we measured species richness and the abundance of each species, examined species turnover and floristic dissimilarity between the two areas and positioned plant species and sites in an abstract multivariate space. Plant community (species richness, percentage of halophytes) and soil physicochemical properties (pH, salinity, moisture content, bulk density, nitrate and ammonium nitrogen concentration) were compared between roadside and non-road areas (young roadside vs. corresponding non-road areas, old roadside vs. corresponding non-road areas) by using t-tests. Classification and ordination techniques were used to examine the relationship between vegetation and related environmental variables in both roadside and non-road areas. Important Findings For both the young and old roadside areas, species richness in roadside areas was significantly higher than in non-road areas and high floristic dissimilarity values indicated that roadside and non-road areas differed greatly in community composition. In both the young and old roadside areas, the plant communities in roadside areas had lower percentages of halophytes than non-road communities. Correspondence analysis and two-way indicator species analysis showed that halophytes dominated in the non-road areas, while a number of typical non-salt-tolerant species dominated in the roadside areas. Compared to non-road areas, activities associated with roads significantly decreased soil moisture, bulk density and salinity and increased soil pH and nitrate content. Forward selection for the environmental variables in canonical correspondence analysis showed that soil salinity was the most important factor related to the variation of species composition between roadside and non-road areas. Our study demonstrates that road effects have a significant impact on the associated vegetation and soil, and these changes are consistent across roads of different ages in our system.

Ecological and morphological features of Amyloodinium ocellatum occurrences in cultivated gilthead seabream Sparus aurata L.; A case study

Understanding the patterns of occurrence of the ectoparasite Amyloodinium ocellatum and the conditions that result in its maintenance at non-dangerous levels for gilthead seabream Sparus aurata could be very useful, since outbreaks of heavy infestation by this parasitic dinoflagellate can cause severe mortality in temperate aquaculture. We have evaluated the interactions between A. ocellatum and related environmental variables for the first time. Biotic and abiotic parameters of water quality in production ponds from a temperate aquaculture (Sado Estuary, Portugal) were monitored and subsequently analysed. Dissolved oxygen, water temperature, pH, phytoplankton biomass and salinity were closely related to A. ocellatum occurrences; dissolved oxygen, water temperature, pH and phytoplankton biomass had significant negative relationships with A. ocellatum trophonts, while salinity had a significant positive relationship with A. ocellatum trophonts in fish gills. Phytoplankton biomass was significantly correlated with increases of dissolved oxygen in production ponds. An increase of rate of water renewal increased salinity, due to persistence of low water levels in production ponds during the water renewal procedure. Salinity negatively affected phytoplankton biomass and consequently the level of dissolved oxygen, raising the probability of A. ocellatum occurrences. Fish biomass in production ponds was correlated with the average and the maximum number of trophonts found in fish gills, highlighting the importance of defining stocking levels and production values in ponds. The present results help to improve understanding of the interactions between biotic and abiotic variables, fish farm management practices and parasite incidence in temperate terrestrial pond aquaculture. A morphological feature of the A. ocellatum tomonts cells in division phase, collected from the most infected fish gills, is discussed. We also give a description and illustration of the phases of the A. ocellatum life cycle.

Influence of nutrients, submerged macrophytes and zooplankton grazing on phytoplankton biomass and diversity along a latitudinal gradient in Europe

In order to evaluate latitudinal differences in the relationship of phytoplankton biomass and diversity with environmental conditions in shallow lakes, we sampled 98 shallow lakes from three European regions: Denmark (DK), Belgium/The Netherlands (BNL) and southern Spain (SP). Phytoplankton biomass increased with total phosphorus (TP) concentrations and decreased with submerged macrophyte cover across the three regions. Generic richness was significantly negatively related to submerged macrophyte cover and related environmental variables. Zooplankton:phytoplankton biomass ratios were positively related to submerged macrophyte cover and negatively to phytoplankton generic richness in DK and BNL, suggesting that the low generic richness in lakes with submerged macrophytes was due to a higher zooplankton grazing pressure in these regions. In SP, phytoplankton generic richness was not influenced by zooplankton grazing pressure but related to conductivity. We observed no relationship between phytoplankton generic richness and TP concentration in any of the three regions. The three regions differed significantly with respect to mean local and regional generic richness, with BNL being more diverse than the other two regions. Our observations suggest that phytoplankton diversity in European shallow lakes is influenced by submerged macrophyte cover indirectly by modulating zooplankton grazing. This influence of submerged macrophytes and zooplankton grazing on phytoplankton diversity decreases from north to south.

교통이력 데이터의 품질 개선과 What-If 분석을 위한 자료처리 기법의 구현

현재 우리나라에서는 매일 막대한 양의 교통 데이터가 측정장치들로부터 수집되고 있으나 오류 데이터와 누락된 데이터들이 상당히 많은 실정이다. 더구나 이러한 데이터는 중요한 분석의 대상이 될 수 있음에도 불구하고 일정 시간이 지나면 삭제되고 있다. 그리하여 본 논문에서는 이러한 교통 데이터를 지속적으로 누적하여 다차원 모델로 저장하면서 데이터의 품질을 결정하는 유효성과 완전성을 높이면서 what-if 분석 기능을 지원하는 일련의 자료처리 과정을 제공하는 통합 교통이력 데이터베이스 시스템의 구현을 설명한다. 구현된 시스템에서는 다양한 오류 및 누락 데이터 패턴들을 보정하는 기법들을 제공하며, what-if 분석 기능은 다양한 데이터 정제 및 가공 과정들에 관련된 환경변수와 일련의 처리 과정들의 조합을 융통성 있게 정의하도록 함으로써 다양한 상황들을 가정하고 실험하여 결과를 분석할 수 있게 해준다. 이러한 what-if 분석 기능은 교통 데이터의 활용도를 획기적으로 높여주며 외국의 교통데이터 시스템들에서도 제공하지 못하고 있다. 교통이력데이터를 정제한 실험결과 매우 우수한 유효성 및 완전성을 가진 교통 데이터를 생성함을 확인하였다. A vast amount of traffic data is produced every day from detection devices but this data includes a considerable amount of errors and missing values. Moreover, this information is periodically deleted before it could be used as important analysis information. Therefore, this paper discusses the implementation of an integrated traffic history database system that continuously stores the traffic data as a multidimensional model and increases the validity and completeness of the data via a flow of processing steps, and provides a what-if analysis function. The implemented system provides various techniques to correct errors and missing data patterns, and a what-if analysis function that enables the analysis of results under various conditions by allowing the flexible definition of various process related environment variables and combinations of the processing flows. Such what-if analysis functions dramatically increase the usability of traffic data but are not provided by other traffic data systems. Experimantal results for cleaning the traffic history data showed that it provides superior performance in terms of validity and completeness.

Variation in ostracod (Crustacea, Ostracoda) communities in the alluvial valley of the upper Paraná River (Brazil) in relation to substrate

Large river floodplains are convenient model systems to test for variation in animal and plant community structure, as they have a variety of habitats and substrates and are generally dynamic systems through the occurrence of flood pulses with varying intensity. South American floodplain systems furthermore have unique types of substrates, in the form of root systems of floating macrophytes. Here, we investigate the variation in ostracod (small, bivalved crustaceans) communities in relation to substrates and related environmental variables. Sampling was effected in 2004 in the alluvial valley of the upper Parana River, Brazil, in the wet and dry seasons. Five different substrates, including littoral sediment and four macrophyte species root and leaf systems, in four hydrological systems and a variety of habitat types, were sampled. Fifty-four species of Ostracoda were found. Variation partitioning analysis (RDA) showed that ostracod communities significantly differed between different substrates, mainly between the littoral and plants with small root systems (Eichhornia azurea) on the one hand, and plants with large and complex root systems on the other hand (Eichhornia crassipes and Pistia stratiotes). RDA analyses indicated that the pleuston (biotic communities associated with root systems of floating plants) of E. crassipes comprised more non-swimming species than the pleuston of the smaller roots of P. stratiotes, but species-level Kruskal–Wallis analyses could not detect significant differences between both macrophyte species. Also habitat type and hydrological systems contributed to variation amongst ostracod communities, but less so than the factor substrate. Abiotic factors also contributed to variation, but the ranges of all measured water chemistry variables were narrow. This uniformity in abiotic factors, which might be owing to the occurrence of large flooding events, unites all water bodies, even those that are generally separated.

Factors influencing self‐directed career management: an integrative investigation

PurposeThis paper aims to investigate the relationship between the protean career and other variables, including organizational learning climate, individual calling work orientation, and demographic variables.Design/methodology/approachThe research data were obtained from a sample consisting of 292 employees of two South Korean manufacturing companies in the private sector. To collect the research data, this study employed the web survey method.FindingsThe study results showed that two organizational learning climates – embedded system and system connection – and calling orientation had significant positive relationship with the protean career. Demographic variables did not relate significantly to the protean career.Research limitations/implicationsThis paper provides an empirical approach to related environmental and psychological variables influencing the protean career based on the literature review.Practical implicationsThe results have implications for both researchers and practitioners in that the study examines the protean career as it relates to the organizational learning climate and provides suggestions for establishing strategies that foster employees' self‐directed career management attitudes.Originality/valueThis paper offers new and useful insight into the predictors of self‐directed career management by exploring variables related to the protean career.

Three scales of temporal resolution from automated soil respiration measurements

Soil respiration ( R s) is a combination of autotrophic and heterotrophic respiration, but it is often modeled as a single efflux process, influenced by environmental variables similarly across all time scales. Continued progress in understanding sources of variation in soil CO 2 efflux will require development of R s models that incorporate environmental influences at multiple time scales. Coherence analysis, which requires high temporal frequency data on R s and related environmental variables, permits examination of covariation between R s and the factors that influence it at varying temporal frequencies, thus isolating the factors important at each time scale. Automated R s measurements, along with air, soil temperature and moisture were collected at half hour intervals at a temperate forest at Harvard Forest, MA in 2003 and a boreal transition forest at the Howland Forest, ME in 2005. As in other temperate and boreal forests, seasonal variation in R s was strongly correlated with soil temperature. The organic and mineral layer water contents were significantly related to R s at synoptic time scales of 2–3 days to weeks, representing the wetting and drying of the soils as weather patterns move across the region. Post-wetting pulses of R s were correlated with the amount of precipitation and the magnitude of the change from pre-wet-up moisture content to peak moisture content of the organic horizon during the precipitation events. Although soil temperature at 8–10 cm depth and R s showed strong coherence at a 24-h interval, calculated diel Q 10 values for R s were unreasonably high (6–74) during all months for the evergreen forest and during the growing season for the deciduous forest, suggesting that other factors that covary with soil temperature, such as canopy assimilatory processes, may also influence the diel amplitude of R s. Lower diel Q 10 values were obtained based on soil temperature measured at shallower depths or with air temperature, but the fit was poorer and a lag was needed to improve the fit (peak R s followed peak air temperature by several hours), suggesting a role for delayed substrate supply from aboveground processes to affect diel patterns of R s. High frequency automated R s datasets afford the opportunity to disentangle the temporal scales at which environmental factors, such as seasonal temperature and phenology, synoptic weather events and soil moisture, and diel variation in temperature and photosynthesis, affect soil respiration processes.

Characterizing habitat preference of Eurasian river otter (Lutra lutra) in streams using a self-organizing map

We studied the habitat preferences of Eurasian river otters (Lutra lutra) using the distribution patterns of the numbers of spraints and sprainting spots of otters, as well as related environmental variables (habitat zone, river management, bank type, vegetation coverage, width, depth, etc.) in two streams. The numbers of otter spraints and sprainting spots were sampled monthly in two streams on Geoje Island, Republic of Korea, from January to December 2004. Additional environmental variables were measured at the sampling sites. A self-organizing map (SOM), which is an unsupervised artificial neural network, was used to characterize the habitat preferences of otters. In our results, the SOM classified three different groups of study sites based on their habitat conditions, and the habitat differences were effectively visualized on the trained SOM map. Otters showed spatial and temporal dynamics in the numbers of spraints and sprainting spots, and revealed habitat preferences for shallow, narrow areas of streams and edges of water that were not far from reservoirs but covered with trees and shrubs. Additionally, otters preferred an environment in which weirs reduced the drift of water and gathered fishes and had a natural type of stream bank; these findings are relevant for river management. Otters adapted to places close to roads, residential areas, and agricultural areas with some tolerance of human interference.

Exploration of relationships between phytoplankton biomass and related environmental variables using multivariate statistic analysis in a eutrophic shallow lake: A 5-year study

Abstract Understanding the process of the changing phytoplankton patterns can be particularly useful in water quality improvement and management decisions. However, it is generally not easy to illustrate the interactions between phytoplankton biomass and related environmental variables given their high spatial and temporal heterogeneity. To elucidate relationships between them, in a eutrophic shallow lake, Taihu Lake, relative long-term data set of biotic and abiotic parameters of water quality in the lake were conducted using multivariate statistical analysis within seasonal periodicity. The results indicate that water temperature and total phosphorus (TP) played governing roles in phytoplankton dynamics in most seasons (i.e. temperature in winter, spring and summer; TP in spring, summer and autumn); COD (chemical oxygen demand) and BOD (biological oxygen demand) presented significant positive relationships with phytoplankton biomass in spring, summer and autumn. However, a complex interplay was found between phytoplankton biomass and nitrogen considering significant positive relationships occurring between them in spring and autumn, and conversely negative ones in summer. As the predatory factor, zooplankton presented significant grazing-pressure on phytoplankton biomass during summer in view of negative relationship between them in the season. Significant feedback effects of phytoplankton development were identified in summer and autumn in view that significant relationships were observed between phytoplankton biomass and pH, Trans (transparency of water) and DO. The results indicate that interactions between phytoplankton biomass and related environmental variables are highly sensitive to seasonal periodicity, which improves understanding of different roles of biotic and abiotic variables upon phytoplankton variability, and hence, advances management methods for eutrophic lakes.

Multivariate Analysis of Interactions Between Phytoplankton Biomass and Environmental Variables in Taihu Lake, China

Phytoplankton variation in large shallow eutrophic lakes is characterized by high spatial and temporal heterogenity. Understanding the pattern of phytoplankton variation and the relationships between it and environmental variables can contribute to eutrophic lakes management. In this study Taihu Lake, one of the largest eutrophic fresh water lake in China, was taken as study area. The water body of Taihu Lake was divided into five regions viz. Wuli bay (WB), Meilian Bay (MB), West Taihu Lake (WTL), Main Body of Taihu Lake (MBTL) and East Taihu Lake (ETL). Concentrations of chlorophyll-a and the related environmental variables were determined in each region in the period 2000-2003. Factor analysis and multivariate analysis were applied to evaluate the interactions between phytoplankton variation and environmental variables. Results showed that the highest average concentrations of TN, TP and Chl-a were observed in WB, followed in a descending order by MB and WTL, and the lowest concentrations of TN, TP and Chl-a were observed in MBTL and ETL. Chl-a and TP concentrations in most regions (except ETL) declined during the study period. It suggested that to some extent the lake was recovering from eutrophication. However, persistent ascending of TN and NH(4)-N in all five regions indicated the deteriorating of water quality in the study period. Results of multivariate showed that the relationships between phytoplankton biomass and environmental variables varied among regions. TP illustrated itself a controlling role on phytoplankton in WB, MB, WTL and MBTL according to the significant positive relations to phytoplankton biomass in these regions. Nitrogen could be identified as a limiting factor to phytoplankton biomass in ETL in view of the positive correlations between TN and phytoplankton and between NH(4)-N and phytoplankton. Spatial variation of interactions between phytoplankton and environmental parameters suggested proper eutrophication control measures were needed to restore ecological system in each region of Taihu Lake.

Alpine pond biodiversity: what are the related environmental variables?

1. The aim of this study was to identify the environmental variables correlated with biodiversity in alpine ponds. 2. Twenty alpine ponds in Switzerland were chosen to examine the relationship between the species (or family) richness of five biological groups and a selection of eight environmental variables. 3. Altitude, pH,. conductivity, macrophyte presence, fish presence and trophic state, showed significant relationships with the diversity of at least one biological group. On the other hand, pond area and depth demonstrated no significant correlations with biodiversity. 4. Most highlighted relationships between biodiversity and environmental variables were different from those seen in lowland ponds, reflecting the distinctive nature of alpine water bodies. The results of the study suggest that there is a need to establish specific biodiversity evaluation tools for alpine ponds, which differ from those already used for lowland ponds.

Depressive Symptoms in Adolescents Living in Rural America

The purposes of this pilot study were to examine prevalence of depressive symptoms among rural adolescents and identify related social and environmental variables. A convenience sample of 299 14- to 18-year-old agriculture class students at 5 rural high schools in Kentucky and Iowa completed a survey that included demographic information, family farm history, experience with suicide, perception of school environment, and indicators of farm injuries and risky behaviors. Participants also completed the Center for Epidemiologic Studies Depression Scale (CES-D) as well as scales to assess the number of major life events in the last year, active coping use, and family closeness. The prevalence of a high level of depressive symptoms (CES-D > or = 16) in this sample was 34%. Nine percent had seriously considered suicide in the last year. Unlike previous reports, boys reported as many depressive symptoms as girls. Although the literature reports that engaging in risky behavior is associated with depressive symptoms, the only risky behavior linked with depressive symptoms in this sample was operating a 4-wheel all-terrain vehicle. Other predictors of depressive symptoms included poor family relationships and poor active coping. Interventions to identify and prevent depressive symptoms in rural adolescents are needed. Boosting active coping and improving family function may also prevent the development of clinical depression in rural adolescents.

Shoot morphometry and production dynamics of eelgrass in the northern Baltic Sea

Zostera marina L. related parameters and environmental variables (hydrography and sediment porewater nutrients) were measured from May to October, 1998 at two sites in the northern Baltic Sea (61°N and 20°E). Density (70–400 shoots m −2), biomass and production were low. Biomass peaked in August (20 g dry weight (dw) m −2, range: 4–33 g dw m −2). Production displayed seasonal and vertical patterns, occasionally correlating with temperature, but differing between the sites. At site 1, production was similar at shallow and intermediate depths (average: 75 and 85 mg dw m −2 per day, respectively) and constantly higher at the lower (4.2 m) boundary (average: 130 mg dw m −2 per day). At site 2, the highest production (average: 370 mg dw m −2 per day) was recorded at the upper (1.4 m) distribution limit, while production at the lower boundary (3.9 m) was constantly lower (250–80 mg dw m −2 per day). In a global comparison, these values are the lowest recorded for Z. marina, most likely because of light limitation (deep stations only) and low nutrient concentrations in both the water column and in the sediment. The results suggest, that Z. marina, occurring only at exposed, organically poor, sandy sediments in the northern Baltic Sea, may temporarily overcome nutrient limitation by utilising elevated nutrient levels from land run-off, decaying algal masses and/or upwelling events. These mechanisms most likely explain the observed differences between the sites studied.

Shoot morphometry and production dynamics of eelgrass in the northern Baltic Sea

Zostera marina L. related parameters and environmental variables (hydrography and sediment porewater nutrients) were measured from May to October, 1998 at two sites in the northern Baltic Sea (61°N and 20°E). Density (70–400 shoots m −2 ), biomass and production were low. Biomass peaked in August (20 g dry weight (dw) m −2 , range: 4–33 g dw m −2 ). Production displayed seasonal and vertical patterns, occasionally correlating with temperature, but differing between the sites. At site 1, production was similar at shallow and intermediate depths (average: 75 and 85 mg dw m −2 per day, respectively) and constantly higher at the lower (4.2 m) boundary (average: 130 mg dw m −2 per day). At site 2, the highest production (average: 370 mg dw m −2 per day) was recorded at the upper (1.4 m) distribution limit, while production at the lower boundary (3.9 m) was constantly lower (250–80 mg dw m −2 per day). In a global comparison, these values are the lowest recorded for Z. marina , most likely because of light limitation (deep stations only) and low nutrient concentrations in both the water column and in the sediment. The results suggest, that Z. marina , occurring only at exposed, organically poor, sandy sediments in the northern Baltic Sea, may temporarily overcome nutrient limitation by utilising elevated nutrient levels from land run-off, decaying algal masses and/or upwelling events. These mechanisms most likely explain the observed differences between the sites studied.

Spatial distribution of chromium and lead in the benthic environment of coastal areas of the Río De La Plata estuary (Montevideo, Uruguay).

Twenty-four sediment samples were collected seasonally during one year from the partially closed Montevideo Bay and the adjacent coastal zone, in Uruguay, in order to determine the impact of chromium and lead in the sediments. Analysis of related environmental variables included bottom water temperature, salinity, pH, dissolved oxygen, and several sedimentological variables such as redox potential and total organic matter. Concentrations and range of variation of these two metals were similar to those found in urbanized and industrialized estuarine environments. Metal enrichment is higher in the bay than in the adjacent coastal zone, however an important increase especially in Pb content was detected in an area previously considered as a pristine one. Considering both metal content and benthic environment characteristics, the study area can be clearly divided in at least two well-defined regions. One is the inner region of the bay near the streams, and the outermost stations of the bay and the adjacent coastal zone form the other. The first one can be considered highly polluted and the other moderately polluted. The values of the metals studied indicated that adverse biological effects are probably occurring, specially in the innermost region of Montevideo Bay.

Diatom-based conductivity and water-level inference models from eastern Tibetan (Qinghai-Xizang) Plateau lakes

Climate in central Asia is dominated by the Asian monsoon. The varying impact of the summer monsoon across the Tibetan (Qinghai-Xizang) Plateau provides a strong gradient in precipitation, resulting in lakes of different salinity. Diatoms have been shown to indicate changes in salinity. Thus, transfer functions for diatoms and salinity or related environmental variables represent an excellent tool for paleoclimatic reconstructions in the Tibetan Plateau. Forty freshwater to hypersaline lakes (salinity: 0.1 to 91.7 g l−1) were investigated in the eastern Tibetan Plateau. The relationship between 120 diatom taxa and conductivity, maximum water depth and major ions were analyzed using an indicator value approach, ordination and taxon response models. Canonical correspondence analysis indicated that conductivity was the most important variable, accounting for 10.8% of the variance in the diatom assemblages. In addition water depth and weathering were influential. Weighted Averaging (WA) and Weighted Averaging Partial Least Square (WA-PLS) regression and calibration models were used to establish diatom-conductivity and water depth transfer functions. An optimal two-component WA-PLS model provided a high jack-knifed coefficient of prediction for conductivity (r2jack = 0.92), with a moderate root mean squared error of prediction (RMSEPjack = 0.22), a very low mean bias (0.0003), and a moderate maximum bias (0.26). A WA model with tolerance downweighting resulted in a slightly lower r2jack (0.89) for water depth, with RMSEPjack= 0.26, mean bias = −0.0103 and maximum bias = 0.26.

AEGIS/WIN: A Computer Program for the Application of Crop Simulation Models Across Geographic Areas

AbstractComputer‐based biological simulation models have been used to calculate the effects of different management practices and land‐use systems on agricultural production and to assess the impact of these practices on the environment. Using spatial visualization techniques to display simulation results can significantly improve the presentation and interpretation of these analyses. The objective of this study was to develop a computer program for the spatial application of crop models as well as the analysis and visualization of modeled results. The Agricultural and Environmental Geographic Information System for Windows (AEGIS/WIN) links the simulation system Decision Support System for Agrotechnology Transfer (DSSAT) v3 with the geographic mapping tool ArcView 2. The interface between the two systems was programmed using Avenue, an object‐oriented macro programming language. This interface handles automatic data and command transfers between the simulation system and the mapping tool and does not require any modifications of DSSAT v3. The main spatial input for AEGIS/WIN is a coverage in the form of a digital map of a farm, a region, or any other area. DSSAT is used to create model input files and to execute the various crop management scenarios for the selected coverage. The crop model outputs can be imported and joined with the original selected land‐use map in ArcView. The simulation results can be analyzed with AEGIS/WIN using simple statistics and bar charts. AEGIS/WIN's most important feature is the display of thematic maps of simulated crop yield, yield components, and other related agronomic and environmental variables. The system was applied to study the spatial yield variability of peanut (Arachis hypogaea L.) for a research farm in Georgia. AEGIS/WIN was shown to be an effective tool for the spatial application of crop simulation models and for the analysis and visualization of simulated outputs.

Community structure of rotifers in two environments of the upper River Paran� floodplain (MS) - Brazil

We evaluate the influence of abiotic and biotic factors on the community structure of rotifers across a regional hydrological cycle in lotic and lentic environments of the upper River Parana. Depth, transparency, temperature, pH, electrical conductivity, dissolved oxygen, chlorophyll a and densities of rotifers were measured at two stations in Lake Guarana (littoral and open water regions) and at one station in the River Baia (open water region). Highest densities of rotifers were found at the lake littoral. Canonical correlation analysis related environmental variables with the densities of the most abundant rotifers. The strongest relationship was with chlorophyll a, dissolved oxygen, hydrological level and water temperature. Diversity of rotifers at each station was mainly explained by fluctuations in hydrological level. Results of grouping analysis suggested the formation of groups according to phases of the hydrological cycle.

Sequential Data in Biological Experiments: An Introduction for Research Workers.

A simple factorial grazing experiment measured on 27 occasions a 3x3 factorial with quantitive levels definable with-individual comparisons covariance pre-treatment observations in the design of experiments weighted regression, goodness-of-fit and related topics environmental variables correlation between series of random variables response (reaction) times.