Experimental verification of ecological niche modeling in a heterogeneous environment

The current range of ecological habitats occupied by a species reflects a combination of the ecological tolerance of the species, dispersal limitation, and competition. Whether the current distribution of a species accurately reflects its niche has important consequences for the role of ecological niche modeling in predicting changes in species ranges as the result of biological invasions and climate change. We employed a detailed data set of species occurrence and spatial variation in biotic and abiotic attributes to model the niche of a native California annual plant, Collinsia sparsiflora. We tested the robustness of our model for both the realized and fundamental niche by planting seeds collected from four populations, representing two ecotypes, into plots that fully represented the five-dimensional niche space described by our model. The model successfully predicted which habitats allowed for C. sparsiflora persistence, but only for one of the two source ecotypes. Our results show that substantial niche divergence has occurred in our sample of four study populations, illustrating the importance of adequately sampling and describing within-species variation in niche modeling.     

Idle emissions from heavy-duty diesel vehicles: review and recent data

Heavy-duty diesel vehicle idling consumes fuel and reduces atmospheric quality, but its restriction cannot simply be proscribed, because cab heat or air-conditioning provides essential driver comfort. A comprehensive tailpipe emissions database to describe idling impacts is not yet available. This paper presents a substantial data set that incorporates results from the West Virginia University transient engine test cell, the E-55/59 Study and the Gasoline/Diesel PM Split Study. It covered 75 heavy-duty diesel engines and trucks, which were divided into two groups: vehicles with mechanical fuel injection (MFI) and vehicles with electronic fuel injection (EFI). Idle emissions of CO, hydrocarbon (HC), oxides of nitrogen (NOx), particulate matter (PM), and carbon dioxide (CO2) have been reported. Idle CO2 emissions allowed the projection of fuel consumption during idling. Test-to-test variations were observed for repeat idle tests on the same vehicle because of measurement variation, accessory loads, and ambient conditions. Vehicles fitted with EFI, on average, emitted approximately 20 g/hr of CO, 6 g/hr of HC, 86 g/hr of NOx, 1 g/hr of PM, and 4636 g/hr of CO2 during idle. MFI equipped vehicles emitted approximately 35 g/hr of CO, 23 g/hr of HC, 48 g/hr of NOx, 4 g/hr of PM, and 4484 g/hr of CO2, on average, during idle. Vehicles with EFI emitted less idle CO, HC, and PM, which could be attributed to the efficient combustion and superior fuel atomization in EFI systems. Idle NOx, however, increased with EFI, which corresponds with the advancing of timing to improve idle combustion. Fuel injection management did not have any effect on CO2 and, hence, fuel consumption. Use of air conditioning without increasing engine speed increased idle CO2, NOx, PM, HC, and fuel consumption by 25% on average. When the engine speed was elevated from 600 to 1100 revolutions per minute, CO2 and NOx emissions and fuel consumption increased by >150%, whereas PM and HC emissions increased by approximately 100% and 70%, respectively. Six Detroit Diesel Corp. (DDC) Series 60 engines in engine test cell were found to emit less CO, NOx, and PM emissions and consumed fuel at only 75% of the level found in the chassis dynamometer data. This is because fan and compressor loads were absent in the engine test cell.     

CLIMATE CHANGE IMPACTS UNCERTAINTY FOR WATER RESOURCES IN THE SAN JOAQUIN RIVER BASIN,CALIFORNIA1

ABSTRACT: A climate change impacts assessment for water resources in the San Joaquin River region of California is presented. Regional climate projections are based on a 1 percent per year CO₂ increase relative to late 20th Century CO₂ conditions. Two global projections of this CO₂ increase scenario are considered (HadCM2 and PCM) during two future periods (2010 to 2039 and 2050 to 2079). HadCM2 projects faster warming than PCM. HadCM2 and PCM project wetter and drier conditions, respectively, relative to present climate. In the HadCM2 case, there would be increased reservoir inflows, increased storage limited by existing capacity, and increased releases for deliveries and river flows. In the PCM case, there would be decreased reservoir inflows, decreased storage and releases, and decreased deliveries. Impacts under either projection case cannot be regarded as more likely than the other. Most of the impacts uncertainty is attributable to the divergence in the precipitation projections. The range of assessed impacts is too broad to guide selection of mitigation projects. Regional planning agencies can respond by developing contingency strategies for these cases and applying the methodology herein to evaluate a broader set of CO₂ scenarios, land use projections, and operational assumptions. Improved agency access to climate projection information is necessary to support this effort.     

Multi-element geochemical analysis of snow samples: Use of discriminant analysis in interpreting the results

This paper records the concentrations of major and trace elements determined from snow samples collected during a comprehensive survey undertaken in the Scottish Highlands during the winter and spring period of 1987. The configuration of calculated back-trajectories allowed the samples to be categorized into one of five geographical sectors. Discriminant analysis was used to check the validity of these calculations, to isolate potentially deviant samples, and to predict the possible source of one sample whose back-trajectory could not be computed with confidence. Limitations of the statistical method are discussed, but we conclude that the technique justifies more use by environmental scientists involved in the evaluation of data.     

Future methane emissions from the heavy-duty natural gas transportation sector for stasis,high, medium,and low scenarios in 2035

Today’s heavy-duty natural gas–fueled fleet is estimated to represent less than 2% of the total fleet. However, over the next couple of decades, predictions are that the percentage could grow to represent as much as 50%. Although fueling switching to natural gas could provide a climate benefit relative to diesel fuel, the potential for emissions of methane (a potent greenhouse gas) from natural gas–fueled vehicles has been identified as a concern. Since today’s heavy-duty natural gas–fueled fleet penetration is low, today’s total fleet-wide emissions will be also be low regardless of per vehicle emissions. However, predicted growth could result in a significant quantity of methane emissions. To evaluate this potential and identify effective options for minimizing emissions, future growth scenarios of heavy-duty natural gas–fueled vehicles, and compressed natural gas and liquefied natural gas fueling stations that serve them, have been developed for 2035, when the populations could be significant. The scenarios rely on the most recent measurement campaign of the latest manufactured technology, equipment, and vehicles reported in a companion paper as well as projections of technology and practice advances. These “pump-to-wheels”(PTW) projections do not include methane emissions outside of the bounds of the vehicles and fuel stations themselves and should not be confused with a complete wells-to-wheels analysis. Stasis, high, medium, and low scenario PTW emissions projections for 2035 were 1.32%, 0.67%, 0.33%, and 0.15% of the fuel used. The scenarios highlight that a large emissions reductions could be realized with closed crankcase operation, improved best practices, and implementation of vent mitigation technologies. Recognition of the potential pathways for emissions reductions could further enhance the heavy-duty transportation sectors ability to reduce carbon emissions.

Implications: Newly collected pump-to-wheels methane emissions data for current natural gas technologies were combined with future market growth scenarios, estimated technology advancements, and best practices to examine the climate benefit of future fuel switching. The analysis indicates the necessary targets of efficiency, methane emissions, market penetration, and best practices necessary to enable a pathway for natural gas to reduce the carbon intensity of the heavy-duty transportation sector.     

Sustainable construction: composite use of tyres and ash in concrete

An investigation was carried out to establish the physical, mechanical and chemical characteristics of a non-standard (unprocessed) pulverised fuel ash (PFA) and waste tyres from a former landfill site at the Power Station Hill near Church Village, South Wales, United Kingdom. Investigations are on-going to establish the suitability of the fly ash and/or tyres in road construction (embankment and pavement) and also in concrete to be used in the construction of the proposed highway. This paper reports on concrete-based construction where concrete blends (using various levels of PFA as partial replacement for Portland cement (PC), and shredded waste tyres (chips 15-20mm) as aggregate replacement) were subjected to unconfined compressive strength tests to establish performance, hence, optimising mix designs. Strength development up to 180 days for the concrete made with PC-PFA blends as binders (PC-PFA concrete), with and without aggregate replacement with tyre chips, is reported. The binary PC-PFA concrete does not have good early strength but tends to improve at longer curing periods. The low early strength observed means that PC-PFA concrete cannot be used for structures, hence, only as low to medium strength applications such as blinding, low-strength foundations, crash barriers, noise reduction barriers, cycle paths, footpaths and material for pipe bedding.     

Reproduction and survival of tawny owls in relation to persistent organic pollutants

The potential effects of organochlorines (OCs) and brominated flame retardants on reproduction and survival were studied in tawny owls (Strix aluco) in Central Norway over a period of 19 years (1986-2004). Concentrations of 14 OCs and five polybrominated diphenyl ethers (PBDEs) were measured in eggs (n=104), and Principal Component Analysis was used to produce composite measurements of pollutants; i.e. PC1 and PC2, which accounted for 85% of the variation in contaminant concentrations. There was no evidence for adverse associations between pollutants (PC scores) and life-history traits such as clutch size, probability of producing fledglings and survival, when controlling for potentially confounding variables. Moreover, there was no evidence for interactions between pollutants and vole abundance suggesting no synergistic effects of food stress and pollutants on these life-history traits. There was, however, some evidence for a non-linear negative association between p,p'-DDE (1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene) and eggshell thickness. This suggests that the concentrations of pollutants in this ecosystem were too low to affect reproduction and survival in an owl predominantly consuming prey at low trophic levels, but may be sufficient to cause eggshell thinning at the highest concentrations.     

Influence of Mowing <Emphasis Type="Italic">Artemisia tridentata</Emphasis> ssp. <Emphasis Type="Italic">wyomingensis</Emphasis> on Winter Habitat for Wildlife

Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh (Wyoming big sagebrush) plant communities to improve wildlife habitat, increase forage production for livestock, and create fuel breaks for fire suppression. However, information detailing the influence of mowing on winter habitat for wildlife is lacking. This information is crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter habitat and consume significant quantities of Artemisia during this time. Furthermore, information is generally limited describing the recovery of A. tridentata spp. wyomingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured in midwinter on 0-, 2-, 4-, and 6-year-old fall-applied mechanical (mowed at 20 cm height) treatments and compared to adjacent untreated (control) areas. Mowing compared to the control decreased Artemisia cover, density, canopy volume, canopy elliptical area, and height (P < 0.05), but all characteristics were recovering (P < 0.05). Mowing A. tridentata spp. wyomingensis plant communities slightly increases the nutritional quality of Artemisia leaves (P < 0.05), but it simultaneously results in up to 20 years of decrease in Artemisia structural characteristics. Because of the large reduction in A. tridentata spp. wyomingensis for potentially 20 years following mowing, mowing should not be applied in Artemisia facultative and obligate wildlife winter habitat. Considering the decline in A. tridentata spp. wyomingensis-dominated landscapes, we caution against mowing these communities.     

Assessing anthropogenic impact on Mediterranean sand dunes from aerial digital photography

The Mediterranean region plays host to ca. 33% of the world’s tourism industry. This population of visitors (ca. 147 million in 1990) inevitably exerts an enormous impact on the natural resources of this coastal zone. In May 1997, a new generation Aerial Digital Photographic System [ADPS] configured with a Kodak Digital Science 460 CIR digital camera was used to acquire colour infrared digital photographs of the sand dune systems along the Mediterranean coast of France, from Le Barcares to St-Cyprien-Plage. These have been used to assess the condition of the dunes along this coast. A series of simple analytical techniques to identify and measure features indicative of public pressure using image processing software has been devised. The dune manager with basic computer skills can analyse such indicators as path length, vegetation cover (and conversely the extent of bare sand) to enable monitoring of the performance of their dune systems under particular management regimes. These photographs have been compared with similar digital photographs of dune sites in SW France to allow a comparison of dune degradation in a region with a different population pressure and climate regime. Dune systems sampled from the Mediterranean coastal zone showed more evidence of anthropogenically induced change than those sampled in SW France.