Years Of Field Data Research Articles

The Drinking Water Disparities Framework: On the Origins and Persistence of Inequities in Exposure

With this article, we develop the Drinking Water Disparities Framework to explain environmental injustice in the context of drinking water in the United States. The framework builds on the social epidemiology and environmental justice literatures, and is populated with 5 years of field data (2005-2010) from California's San Joaquin Valley. We trace the mechanisms through which natural, built, and sociopolitical factors work through state, county, community, and household actors to constrain access to safe water and to financial resources for communities. These constraints and regulatory failures produce social disparities in exposure to drinking water contaminants. Water system and household coping capacities lead, at best, to partial protection against exposure. This composite burden explains the origins and persistence of social disparities in exposure to drinking water contaminants.

Communal nursing in wild house mice is not a by-product of group living: Females choose

Communal nursing, the provision of milk to non-offspring, has been argued to be a non-adaptive by-product of group living. We used 2 years of field data from a wild house mouse population to investigate this question. Communal nursing never occurred among females that previously lacked overlap in nest box use. Females nursed communally in only 33 % of cases in which there was a communal nursing partner available from the same social group. Solitarily nursing females were not socially isolated in their group; nevertheless, high spatial associations prior to reproduction predict which potential female partner was chosen for communal nursing. An increase in partner availability increased the probability of communal nursing, but population density itself had a negative effect, which may reflect increased female reproductive competition during summer. These results argue that females are selective in their choice of nursing partners and provide further support that communal nursing with the right partner is adaptive.Electronic supplementary materialThe online version of this article (doi:10.1007/s00114-013-1130-6) contains supplementary material, which is available to authorized users.

A native fungal symbiont facilitates the prevalence and development of an invasive pathogen–native vector symbiosis

Invasive pathogen-insect symbioses have been extensively studied in many different ecological niches. Whether the damage of symbioses in different introduced regions might be influenced by other microorganisms has, however, received little attention. Eight years of field data showed that the varied levels of the nematode and beetle populations and infested trees of the invasive Bursaphelenchus xylophilus--Monochamus alternatus symbiosis were correlated with patterns in the isolation frequencies of ophiostomatoid fungi at six sites, while the laboratory experiments showed that the nematode produced greater numbers of offspring with a female-biased sex ratio and developed faster in the presence of one native symbiotic ophiostomatoid fungus, Sporothrix sp. 1. Diacetone alcohol (DAA) from xylem inoculated with Sporothrix sp. 1 induced B. xylophilus to produce greater numbers of offspring. Its presence also significantly increased the growth and survival rate of M. alternatus, and possibly explains the prevalence of the nematode-vector symbiosis when Sporothrix sp. 1 was dominant in the fungal communities. Studying the means by which multispecies interactions contributed to biogeographical dynamics allowed us to better understand the varied levels of damage caused by biological invasion across the invaded range.

CE-QUAL-W2를 이용한 충주호의 부유물질 및 부영양화 모의평가

본 연구의 목적은 충주호 유역을 대상으로 2차원 횡방향 평균 수리 및 수질모형인 CE-QUAL-W2를 이용하여 호소내 수온분포, 부유물질 및 부영양화 과정의 변화특성을 모의하고 모형의 적용성을 평가하는 것이다. 지형 및 단면자료 구축을 위해 충주호를 남한강 본류(branch 1)와 유입 경계부(branch 2~7)로 구분하여 격자를 구성하였다. 호소 수질모델링을 위한 주요 입력 자료로 기상자료, 호소의 수온과 탁도 초기조건, 하천의 유량과 수온, 수질 경계조건 자료를 구축하였다. 이후 실측된 수온, 부유물질(SS), 총질소(TN), 총인(TP), 조류(Chl-a)에 대하여 모형의 보정(2010) 및 검증(2008)을 수행하여 모형의 적용가능성을 평가하였다. 충주호의 수온은 4월부터 표층수온이 증가하여 7월초에 성층현상이 발생되고 12월에는 연직수온분포가 일정하게 유지되었다. 집중호우 발생 후에는 성층구조가 교란되어 수온약층이 약 10 m가량 하강하였다. SS는 수온과 동일한 패턴으로 집중호우 발생 후에 증가하다가 12월에 안정화되었으며, 2008년 7월에 발생된 중층밀도류의 분포 현상을 잘 재현하였다. TN, TP의 경우 농도의 범위를 잘 재현하였지만, 모형 내에서 질소성분의 침강속도 및 인의 흡착-침전과정이 적절히 모의되지 않아 오차가 발생하였다. Chl-a의 경우 2010년과 2008년 여름의 조류의 성장패턴을 잘 반영하였지만, 모형이 횡방향 평균 유속과 농도를 사용함에 따른 모형의 한계점이 나타났다. The purpose of this study is to evaluate the suspended solids and eutrophication processes relationships in Chungju lake using CE-QUAL-W2, two-dimensional (2D) longitudinal/vertical hydrodynamic and water quality model. For water quality modeling, the lake segmentation was configured as 7 branches system according to their shape and tributary distribution. The model was calibrated (2010) and validated (2008) using 2 years of field data of water temperature, suspended solids (SS), total nitrogen (TN), total phosphorus (TP) and algae (Chl-a). The water temperature began to increase in depth from April and the stratification occurred at about 10 m early July heavy rain. The high SS concentration of the interflow density currents entering from the watershed was well simulated especially for July 2008 heavy rainfall event. The simulated concentration range of TN and TP was acceptable, but the errors might occur form the poor reflection for sedimentation velocity of nitrogen component and adsorption-sediment of phosphorus in model. The concentration of Chl-a was simulated well with the algal growth patterns in summer of 2010 and 2008, but the error of under estimation may come from the use of width-averaged velocity and concentration, not considering the actual to one side inclination by wind effect.

Chemocline erosion and its conservation by freshwater introduction to meromictic salt lakes

Salinity stratification has been documented in two meromictic lakes in detail. We present seven years of field data on the salinity stratification of meromictic lakes Wallendorfer See and Rassnitzer See forming in the pits of the former lignite mine Merseburg-Ost in the Central German Mining District. Mainly from groundwater inflows, salinity stratified meromictic residual lakes had formed before freshwater was introduced intentionally over a period of two years to fill the pits more rapidly close to the final water level. From the observations, changes in the salinity stratification were interpreted in terms of deposited potential energy. Freshwater introduction (capping) was quantified in terms of potential energy. Thus the evolution of the salinity profiles was explained and their residual shapes became understandable as a consequence of the flooding procedure. Based on the quantitative estimates of energy deposited in the stratification during deep recirculation in winter, prospective statements could be made about the further evolution of the monimolimnia.

Postcopulatory selection for dissimilar gametes maintains heterozygosity in the endangered North Atlantic right whale

Although small populations are expected to lose genetic diversity through genetic drift and inbreeding, a number of mechanisms exist that could minimize this genetic decline. Examples include mate choice for unrelated mates and fertilization patterns biased toward genetically dissimilar gametes. Both processes have been widely documented, but the long-term implications have received little attention. Here, we combined over 25 years of field data with high-resolution genetic data to assess the long-term impacts of biased fertilization patterns in the endangered North Atlantic right whale. Offspring have higher levels of microsatellite heterozygosity than expected from this gene pool (effect size = 0.326, P < 0.011). This pattern is not due to precopulatory mate choice for genetically dissimilar mates (P < 0.600), but instead results from postcopulatory selection for gametes that are genetically dissimilar (effect size = 0.37, P < 0.003). The long-term implication is that heterozygosity has slowly increased in calves born throughout the study period, as opposed to the slight decline that was expected. Therefore, this mechanism represents a natural means through which small populations can mitigate the loss of genetic diversity over time.

Dynamic species distribution models from categorical survey data

1. Species distribution models are static models for the distribution of a species, based on Hutchinson's niche concept. They make probabilistic predictions about the distribution of a species, but do not have a temporal interpretation. In contrast, density-structured models based on categorical abundance data make it possible to incorporate population dynamics into species distribution modelling. 2. Using dynamic species distribution models, temporal aspects of a species' distribution can be investigated, including the predictability of future abundance categories and the expected persistence times of local populations, and how these may respond to environmental or anthropogenic drivers. 3. We built density-structured models for two intertidal marine invertebrates, the Lusitanian trochid gastropods Phorcus lineatus and Gibbula umbilicalis, based on 9 years of field data from around the United Kingdom. Abundances were recorded on a categorical scale, and stochastic models for year-to-year changes in abundance category were constructed with winter mean sea surface temperature (SST) and wave fetch (a measure of the exposure of a shore) as explanatory variables. 4. Both species were more likely to be present at sites with high SST, but differed in their responses to wave fetch. Phorcus lineatus had more predictable future abundance and longer expected persistence times than G. umbilicalis. This is consistent with the longer lifespan of P. lineatus. 5. Where data from multiple time points are available, dynamic species distribution models of the kind described here have many applications in population and conservation biology. These include allowing for changes over time when combining historical and contemporary data, and predicting how climate change might alter future abundance conditional on current distributions.

Economic analysis of private and public benefits of corn, switchgrass and mixed grass systems in Eastern South Dakota

AbstractThe objective of this research is to develop an economic analysis of different crop mix biofuels programs for meeting ethanol and sustainability demands. Primary data are from South Dakota State University field experiments on farms located in east-central South Dakota. The data include 4 years of field data, three crop systems (mixed grass, switchgrass and corn), two residue treatments (no removal, removal of biomass), and three landscape positions (back slope, crest and foot slope). A representative farm model and five scenarios are developed to conduct a full budget analysis over a 12-year period. Public benefits are evaluated, using the benefit transfer method to value ecosystem services, by allocating a dollar value to three environmental variables; carbon sequestration, reduction of sedimentation and pheasant production. Stochastic simulation results are compared for each of the five scenarios, one with only annualized net private returns, and one including the value of environmental benefits. Results indicate that: (1) the conventional continuous corn scenario has the highest net returns over the 12-year budget, (2) carbon sequestration represents 80% of the environmental benefits, and (3) the added economic value of ecosystem services does not provide enough incentives for farmers to convert from corn production to grass production.

Diminishing Returns from Increased Percent Bt Cotton: The Case of Pink Bollworm

Regional suppression of pests by transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) has been reported in several cropping systems, but little is known about the functional relationship between the ultimate pest population density and the pervasiveness of Bt crops. Here we address this issue by analyzing 16 years of field data on pink bollworm (Pectinophora gossypiella) population density and percentage of Bt cotton in the Yangtze River Valley of China. In this region, the percentage of cotton hectares planted with Bt cotton increased from 9% in 2000 to 94% in 2009 and 2010. We find that as the percent Bt cotton increased over the years, the cross-year growth rate of pink bollworm from the last generation of one year to the first generation of the next year decreased. However, as the percent Bt cotton increased, the within-year growth rate of pink bollworm from the first to last generation of the same year increased, with a slope approximately opposite to that of the cross-year rates. As a result, we did not find a statistically significant decline in the annual growth rate of pink bollworm as the percent Bt cotton increased over time. Consistent with the data, our modeling analyses predict that the regional average density of pink bollworm declines as the percent Bt cotton increases, but the higher the percent Bt cotton, the slower the decline in pest density. Specifically, we find that 95% Bt cotton is predicted to cause only 3% more reduction in larval density than 80% Bt cotton. The results here suggest that density dependence can act against the decline in pest density and diminish the net effects of Bt cotton on suppression of pink bollworm in the study region. The findings call for more studies of the interactions between pest density-dependence and Bt crops.

Modeling population growth and site specific control of the invasive Lantana camara L. (Verbenaceae) under differing fire regimes

AbstractIt is at the population level that an invasion either fails or succeeds. Lantana camara L. (Verbenaceae) is a weed of great significance in Queensland Australia and globally but its whole life‐history ecology is poorly known. Here we used 3 years of field data across four land use types (farm, hoop pine plantation and two open eucalyptus forests, including one with a triennial fire regime) to parameterise the weed's vital rates and develop size‐structured matrix models. Lantanacamara in its re‐colonization phase, as observed in the recently cleared hoop pine plantation, was projected to increase more rapidly (annual growth rate, λ = 3.80) than at the other three sites (λ 1.88–2.71). Elasticity analyses indicated that growth contributed more (64.6 %) to λ than fecundity (18.5 %) or survival (15.5 %), while across size groups, the contribution was of the order: juvenile (19–27 %) ≥ seed (17–28 %) ≥ seedling (16–25 %) &gt; small adult (4–26 %) ≥ medium adult (7–20 %) &gt; large adult (0–20 %). From a control perspective it is difficult to determine a single weak point in the life cycle of lantana that might be exploited to reduce growth below a sustaining rate. The triennial fire regime applied did not alter the population elasticity structure nor resulted in local control of the weed. However, simulations showed that, except for the farm population, periodic burning could work within 4–10 years for control of the weed, but fire frequency should increase to at least once every 2 years. For the farm, site‐specific control may be achieved by 15 years if the biennial fire frequency is tempered with increased burning intensity.

Size Selectivity of Predation by Brown Bears Depends on the Density of Their Sockeye Salmon Prey

Can variation in prey density drive changes in the intensity or direction of selective predation in natural systems? Despite ample evidence of density-dependent selection, the influence of prey density on predatory selection patterns has seldom been investigated empirically. We used 20 years of field data on brown bears (Ursus arctos) foraging on sockeye salmon (Oncorhynchus nerka) in Alaska, to test the hypothesis that salmon density affects the strength of size-selective predation. Measurements from 41,240 individual salmon were used to calculate variance-standardized selection differentials describing the direction and magnitude of selection. Across the time series, the intensity of predatory selection was inversely correlated with salmon density; greater selection for smaller salmon occurred at low salmon densities as bears' tendency to kill larger-than-average salmon was magnified. This novel connection between density dependence and selective predation runs contrary to some aspects of optimal foraging theory and differs from many observations of density-dependent selection because (1) the direction of selection remains constant while its magnitude changes as a function of density and (2) stronger selection is observed at low abundance. These findings indicate that sockeye salmon may be subject to fishery-induced size selection from both direct mechanisms and latent effects of altered predatory selection patterns on the spawning grounds, resulting from reduced salmon abundance.

Impact evaluation of a pisciculture in the Tucuruí reservoir (Pará, Brazil) using a two-dimensional water quality model

► We modeled the Tucuruí reservoir, Brazil, for assess phytoplankton growth. ► Simulations were carried out in low and high rainfall periods, by using CEQUAL-W2. ► We reproduced horizontal and vertical gradients, temporal and spatial variability. ► Model showed chlorophyll a is a key factor to define the system’s trophic status . ► Model can simulate several scenarios, by changes in reservoir management . The Tucuruí reservoir, Pará State, Brazil, has one of the largest flooded areas in Brazil and its viability for aquaculture is being evaluated by local government in pilot projects. In this context, the purpose of this study is to assess the impact of a pisciculture in the water quality of the reservoir, by combining field data with model simulations. Hydrodynamics and water quality was modeled using CE-QUAL-W2. The model was validated using about 5 years of field data of temperature, nitrate, ammonia, phosphorus, total suspended solids (TSSs), dissolved oxygen and chlorophyll a . The model was able to reproduce horizontal and vertical gradients and their temporal variability. After validation, the model was used to simulate the response of water quality to various management scenarios of the pisciculture. Results show that solely based on phosphorus index, an increase of 30% occurs from 2007 to 2011, and at least 10% from 2008 to 2011. Based on this, the system tends to change its trophic state from oligotrophic to mesotrophic. However, if we consider chlorophyll a (Chl a ) as an indicator, no change in the trophic state is observed, since even with a 100% increase of the phosphorus load, the concentration of Chl a remains oligotrophic (<4 μg/L) during the simulated period. Thus, the model results suggest that Chl a should be used as the key indicator to assess the trophic state of the system, since the nutrients may be in excess in the environment without promoting primary production.

Assessing extinction risks under the combined effects of climate change and human disturbance through the analysis of life-history plasticity

Abstract Plastic responses of species to unprecedented conditions and increased variability caused by climate change (CC) and anthropogenic disturbances are expected to play a major role determining populations’ extinction risk. We developed a method for assessing CC effects on population dynamics based on analyzing plastic life history responses to weather conditions within an ensemble forecasting framework. The method is illustrated using two threatened cactus species with contrasting distribution ranges. Demographic models were parameterized using 5 years of field data, from which the relationship between life-history traits and rainfall and temperature was estimated. These functions were used in Integral Projection Models to predict population growth under CC scenarios and different anthropogenic disturbance regimes. Both species were affected by CC and its interaction with disturbance. The most widespread species was less affected by CC, suggesting that past selection on plasticity allows it to survive under variable conditions. Managing disturbance appropriately lessened the impact of CC. Some directives for conservation under CC were identified based on projected elasticity values. Our procedure for modeling population dynamics as a function of climate may be used for designing management plans for conservation or sustainable use aimed at important plant sizes or life-history traits, predicting potential distributions, and identifying viable populations.

The Halo Effect: Suppression of Pink Bollworm on Non-Bt Cotton by Bt Cotton in China

In some previously reported cases, transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) have suppressed insect pests not only in fields planted with such crops, but also regionally on host plants that do not produce Bt toxins. Here we used 16 years of field data to determine if Bt cotton caused this “halo effect” against pink bollworm (Pectinophora gossypiella) in six provinces of the Yangtze River Valley of China. In this region, the percentage of cotton hectares planted with Bt cotton increased from 9% in 2000 to 94% in 2009 and 2010. We found that Bt cotton significantly decreased the population density of pink bollworm on non-Bt cotton, with net decreases of 91% for eggs and 95% for larvae on non-Bt cotton after 11 years of Bt cotton use. Insecticide sprays targeting pink bollworm and cotton bollworm (Helicoverpa armigera) decreased by 69%. Previously reported evidence of the early stages of evolution of pink bollworm resistance to Bt cotton in China has raised concerns that if unchecked, such resistance could eventually diminish or eliminate the benefits of Bt cotton. The results reported here suggest that it might be possible to find a percentage of Bt cotton lower than the current level that causes sufficient regional pest suppression and reduces the risk of resistance.

A Methodology for Estimating and Comparing the Lifecycles of High-Build and Conventional Waterborne Pavement Markings on Primary and Secondary Roads in South Carolina

Highway pavement markings constitute a vital component in roadway transportation systems and provide crucial visual cues for drivers to follow the road. In 2008, the South Carolina Department of Transportation (SCDOT) initiated a study to evaluate pavement markings on noninterstate primary and secondary roads in South Carolina. This article discusses development of a method for estimating and comparing the lifecycles of high-build waterborne and conventional waterborne pavement markings based on retroreflectivity levels. The method was developed using nearly 3 years of field data from 66 sites throughout South Carolina. The article provides an overview of data collection and analysis methods employed in model development. The analysis indicates that high-build markings are predicted to considerably outlast waterborne markings and are also more cost-effective, based on cost per linear foot per year, for two-way Annual Average Daily Traffic (AADT) volume levels up to 2,000 vehicles per day.

A test of the reproductive economy hypothesis in plants: more offspring per capita come from large (not small) parents in Avena barbata

Under crowded conditions, plant populations typically exhibit L-shaped distributions of size. Many plants remain small and suppressed in such populations, and more offspring are propagated into the next generation from the many smaller plants than from the few large plants. The hypothesis of “reproductive economy” advances that this creates natural selection favouring the ability to reproduce while still small over the ability to become large. We develop a simple model using exponential distributions of size within morphs that differ in their growth potential and size threshold for reproduction. Our model shows that selection consistently favours the morph with greater potential to become large, even if that potential comes at the cost of a larger size threshold for reproduction. We also tested the reproductive economy hypothesis using 4 years of field data at two sites in California, USA from an experiment with the annual grass Avena barbata. Despite strongly skewed size distributions, the genotypes giving larger size always increased in frequency between parents and offspring while those of the smallest size class decreased. Directional selection gradients were also always positive and significant, indicating that natural selection indeed favours the few larger plants over their more numerous smaller neighbours. Neither our empirical nor theoretical findings support the reproductive economy hypothesis. Instead, we argue that selection for large size is a manifestation of underlying selection to acquire resources, resolving any perceived paradox of a preponderance of small individuals under selection for large size.

Impact of epistasis and QTL×environmental interaction on the mass filling rate during seed development of soybean

Seed filling rate of soybean has been shown to be a dynamic process in different developmental stages affected by both genotype and environment. The objective of the present study was to determine additive, epistatic and quantitative trait loci (QTLs) × environment interaction (QE) effects of the QTL underlying a seed filling rate of soybean. One hundred and forty-three recombinant inbred lines (RILs) derived from the cross of Charleston and Dongnong 594 were used with 2 years of field data (2004 and 2005). Eleven QTLs with significantly unconditional and conditional additive (a) effect and/or additive × environment interaction (ae) effect at different filling stages were identified. Of them six QTLs showed positive a effects and four QTLs had negative a effects on the seed filling rate during seed development. aa and aae effects of 12 pairs of QTLs were identified by unconditional mapping from the initial stage to the final stage. Thirteen pairs of QTLs underlying the seed filling rate with aa and aae effects were identified by conditional mapping. QTLs with aa and aae (additive × additive × environment) effects appeared to vary at different filling stages. Our results demonstrated that the mass filling rate in soybean seed were under genetic and environmental control.

‘School's Not for Anybody’: Migration as a Sponsor of Literacy in the USA—Mexico Context

In the USA–Mexico context, migration is often considered to be a detrimental influence on young peoples' pursuit of education. When migration is considered to be a positive influence, focus rests on the ways that increased financial resources can create more access to formal education in the migrant's home community. Indeed, physical access to schools tends to be the focus of many initiatives to improve educational experiences in developing nations, or among groups of minority students within the USA. Beyond these considerations of economics and access however, the potentially positive social impacts of migration are rarely considered. Drawing on a year of field data in rural, migrant-sending Mexico and a receiving community in the USA, this article argues that migration actually facilitates, rather than jeopardizes, educational gains in both Mexico and the USA. In particular, social capital garnered through the migration experience and transferred in the form of social remittances, as opposed to purely financial remittances, can have a particularly strong impact on literacy. Furthermore, the ideological impact that these social remittances can have on migrating populations may in some cases have a more powerful effect than does physical access to schools.

Tidal flushing and wind driven circulation of Ahe atoll lagoon (Tuamotu Archipelago, French Polynesia) from in situ observations and numerical modelling

Hydrodynamic functioning and water circulation of the semi-closed deep lagoon of Ahe atoll (Tuamotu Archipelago, French Polynesia) were investigated using 1year of field data and a 3D hydrodynamical model. Tidal amplitude averaged less than 30cm, but tide generated very strong currents (2ms−1) in the pass, creating a jet-like circulation that partitioned the lagoon into three residual circulation cells. The pass entirely flushed excess water brought by waves-induced radiation stress. Circulation patterns were computed for climatological meteorological conditions and summarized with stream function and flushing time. Lagoon hydrodynamics and general overturning circulation was driven by wind. Renewal time was 250days, whereas the e-flushing time yielded a lagoon-wide 80-days average. Tide-driven flush through the pass and wind-driven overturning circulation designate Ahe as a wind-driven, tidally and weakly wave-flushed deep lagoon. The 3D model allows studying pearl oyster larvae dispersal in both realistic and climatological conditions for aquaculture applications.

DRAINMOD: Model Use, Calibration, and Validation

DRAINMOD is a process-based, distributed, field-scale model developed to describe the hydrology of poorly drained and artificially drained soils. The model is based on water balances in the soil profile, on the field surface, and, in some cases, in the drainage system. This article briefly describes the model and the algorithms that are used to quantify the various hydrologic components. Inputs for soil properties, site parameters, weather data, and crop characteristics required in the application of the model are presented and discussed with respect to their role in calibration. Methods for determining field effective values of key inputs to the model, either independently or as a part of the calibration process, are demonstrated in a case study. The case study involved calibrating DRAINMOD with two years of field data for a subsurface drained agricultural field in eastern North Carolina, followed by testing or validation of the model with two additional years of data. Performance statistics indicated that the model with calibrated input data accurately predicted daily water table depths with Nash-Sutcliffe modeling efficiency (EF) values of 0.68 and 0.72, daily drainage rates (EF = 0.73 and 0.49), and monthly drainage volumes (EF = 0.87 and 0.77) for the two-year validation period.