New Perspectives on the Use of GPS and GIS to Support a Highway Performance Study

In recent decades, rapid growth of travel volume has resulted in a significant increase in traffic congestion, accidents, environmental pollution and energy consumption. Accurate traffic data are drastically needed for effective evaluation of traffic systems in order to alleviate the impacts of increasing travel volume of the quality of life and economic development of urban areas. This article provides a discussion on a data acquisition methodology for highway traffic pattern recognition and congestion analysis by integrating data from the global positioning system (GPS) with a geographic information system (GIS). The GPS technology is a powerful tool in capturing continuous positioning and timing information, whereas the GIS is capable of storing, managing, manipulating, analyzing and displaying the acquired spatial information. Compared to previous studies, the effective integration of the two technologies allows for traffic analysis to be conducted at a finer resolution. The proposed method is illustrated with a case study on multiple major highway segments in Columbus, Ohio.     

Succession of microphytobenthos in a restored coastal wetland

Sediment microphytobenthos, such as diatoms and photosynthetic bacteria, are functionally important components of food webs and are key mediators of nutrient dynamics in marine wetlands. The medium to long-term recovery of benthic microproducers in restored habitats designed to improve degraded coastal wetland sites is largely unknown. Using taxon-specific photopigments, we describe the composition of microphytobenthic communities in a large restoration site in southern California and differences in the temporal recovery of biomass (chlorophylla), composition, and taxonomic diversity between vegetatedSpartina foliosa salt marsh and unvegetated mudflat. Visually distinct, spatially discreet, microphytobenthic patches appeared after no more than 7 mo within the restoration site and were distinguished by significant differences in biomass, taxonomic diversity, and the relative abundance of cyanobacteria versus diatoms. Sediment chlorophylla concentrations within the restored site were similar to concentrations in nearby natural habitat 0.2–2.2 yr following marsh creation, suggesting rapid colonization by microproducers. RestoredSpartina marsh very rapidly (between 0.2 and 1.2 yr) acquired microphytobenthic communities of similar composition and diversity to those in naturalSpartina habitat, but restored mudflats took at least 1.6 to 2.2 yr to resemble natural mudflats. These results suggest relatively rapid recovery of microphytobenthic communities at the level of major taxonomic groups. Sediment features, such as pore water salinity andSpartina density, explained little variation in microphytobenthic taxonomic composition. The data imply that provision of structural heterogeneity in wetland construction (such as pools and vascular plants) might speed development of microproducer communities, but no direct seeding of sediment microfloras may be necessary.     

Is lower crustal layering related to extension?

Summary. The Western Approaches Margin (WAM) profile was shot to test the hypothesis that the reflectivity observed in the lower crust is related to extensional processes. The preliminary results of the experiment show that the reflectivity in the lower crust appears to become weaker on the continental shelf near the slope break. Detailed examination of the data however, show a significant increase in noise in the region where the layering appears to fade. The noise may be of sufficient amplitude to obscure any coherent lower crustal events present. Therefore, the only conclusion that can presently be drawn from the dataset is that the layering does not become more pronounced in the region of maximum extension.     

Hydrogeology of desert springs in the Panamint Range,California, USA: Identifying the sources and amount of recharge that support spring flow

Despite its location in the rain shadow of the southern Sierra Nevada, the Panamint Range hosts a complex mountain groundwater system supporting numerous springs which have cultural, historical, and ecological importance. The sources of recharge that support these quintessential desert springs remain poorly quantified since very little hydrogeological research has been completed in the Panamint Range. Here we address the following questions: (i) what is the primary source of recharge that supports springs in the Panamint Range (snowmelt or rainfall), (ii) where is the recharge occurring (mountain-block, mountain-front, or mountain-system) and (iii) how much recharge occurs in the Panamint Range? We answer questions (i) and (ii) using stable isotopes measured in spring waters and precipitation, and question (iii) using a chloride mass-balance approach which is compared to a derivation of the Maxey–Eakin equation. Our dataset of the stable isotopic composition (δ¹⁸O and δ²H) of precipitation is short (1.5 years), but analyses on spring water samples indicate that high-elevation snowmelt is the dominant source of recharge for these springs, accounting for 57 (±9) to 79 (±12) percent of recharge. Recharge from rainfall is small but not insignificant. Mountain-block recharge is the dominant recharge mechanism. However, two basin springs emerging along the western mountain-front of the Panamint Range in Panamint Valley appear to be supported by mountain-front and mountain-system recharge, while Tule Spring (a basin spring emerging at the terminus of the bajada on the eastern side of the Panamint Range) appears to be supported by mountain-front recharge. Calculated recharge rates range from 19 mm year⁻¹ (elevations < 1000 mrsl) to 388 mm year⁻¹ (elevations > 1000 mrsl). The average annual recharge is approximately 91 mm year⁻¹ (equivalent to 19.4 percent of total annual precipitation). We infer that the springs in the Panamint Range (and their associated ecosystems) are extremely vulnerable to changes in snow cover associated with climate change. They are heavily dependent on snowmelt recharge from a relatively thin annual snowpack. These findings have important implications for the vulnerability of desert springs worldwide.     

A systems approach to assess climate change mitigation options in landscapes of the United States forest sector

Background

United States forests can contribute to national strategies for greenhouse gas reductions. The objective of this work was to evaluate forest sector climate change mitigation scenarios from 2018 to 2050 by applying a systems-based approach that accounts for net emissions across four interdependent components: (1) forest ecosystem, (2) land-use change, (3) harvested wood products, and (4) substitution benefits from using wood products and bioenergy. We assessed a range of land management and harvested wood product scenarios for two case studies in the U.S: coastal South Carolina and Northern Wisconsin. We integrated forest inventory and remotely-sensed disturbance data within a modelling framework consisting of a growth-and-yield driven ecosystem carbon model; a harvested wood products model that estimates emissions from commodity production, use and post-consumer treatment; and displacement factors to estimate avoided fossil fuel emissions. We estimated biophysical mitigation potential by comparing net emissions from land management and harvested wood products scenarios with a baseline (‘business as usual’) scenario.

Results

Baseline scenario results showed that the strength of the ecosystem carbon sink has been decreasing in the two sites due to age-related productivity declines and deforestation. Mitigation activities have the potential to lessen or delay the further reduction in the carbon sink. Results of the mitigation analysis indicated that scenarios reducing net forest area loss were most effective in South Carolina, while extending harvest rotations and increasing longer-lived wood products were most effective in Wisconsin. Scenarios aimed at increasing bioenergy use either increased or reduced net emissions within the 32-year analysis timeframe.

Conclusions

It is critical to apply a systems approach to comprehensively assess net emissions from forest sector climate change mitigation scenarios. Although some scenarios produced a benefit by displacing emissions from fossil fuel energy or by substituting wood products for other materials, these benefits can be outweighed by increased carbon emissions in the forest or product systems. Maintaining forests as forests, extending rotations, and shifting commodities to longer-lived products had the strongest mitigation benefits over several decades. Carbon cycle impacts of bioenergy depend on timeframe, feedstocks, and alternative uses of biomass, and cannot be assumed carbon neutral.

     

High‐resolution seismic reflection profiling of neotectonic faults in Lake Timiskaming,Timiskaming Graben,Ontario‐Quebec,Canada

The Timiskaming Graben is a 400 km long, 50 km wide north‐west trending morphotectonic depression within the Canadian Shield of eastern North America and experiences frequent intraplate earthquakes. The graben extends along the border of Ontario and Quebec, connecting southward with the Nipissing and Ottawa‐Bonnechere grabens and the St. Lawrence Rift System which includes a similar structure underlying the Hudson Valley of the eastern USA. Together they form a complex failed rift system related to regional extension of North American crust during the breakup of Rodinia and, later, Pangea. The Timiskaming Graben lies within a belt of heightened seismic activity (Western Quebec Seismic Zone) with frequent moderate magnitude (greater than magnitude 5) earthquakes including a magnitude 6.2 in 1935. These events threaten aging urban infrastructure built on soft glacial sediments; post‐glacial landslides along the Ottawa Valley suggest earthquakes as large as magnitude 7. The inner part of the Timiskaming Graben is filled by Lake Timiskaming, a large 110 km long post‐glacial successor to glacial Lake Barlow that was ponded by the Laurentide Ice Sheet 9500 years ago. The effects of frequent ground shaking on lake floor sediments was assessed by collecting more than 1000 line kilometres of high‐resolution ‘chirp’ seismic profiles. Late glacial Lake Barlow glaciolacustrine and overlying post‐glacial sediments are extensively deformed by extensional faults that define prominent horsts and grabens; multibeam bathymetry data suggest that faults influence the morphology of the modern lake floor, despite high sedimentation rates, and indicate recent neotectonic deformation. The Lake Timiskaming area provides evidence of post‐glacial intracratonic faulting related to recurring earthquake activity along a weak spot within the North American plate.     

US public opinion on climate change issues: implications for consensus-building and policymaking

While the Conference of the Parties wrangle at an international scale with climate policy, a quiet set of policies and measures is being implemented at a local scale by municipalities across the globe. This study examines the motivation municipalities have for undertaking policies to reduce their greenhouse gas emissions, when the theory of free-ridingwould predict that local administrations should find it difficult to unilaterally reduce their emissions for the benefit of the global climate. Through interviews with officials and/or staff in 23 municipalities in the United States enacting climate policy, data are gathered that suggest local government abatement policies are primarily a top—down decision based on what officials or staff members believe to be “good business” or rational policy choices. They are primarily driven by the potential for realised or perceived cost savings and co-benefits rather than by public pressure. Economic data from some dozen municipal projects are analyzed, finding, while municipalities lack sophisticated accounting techniques, some justification for the often-disputed claim that at least initial reductions in emissions can be made at cost savings. In the United States, with the lack of national abatement policies, it is municipalities that are leading the way in beginning to implement mitigation strategies, even if only for initial reductions.