Showing papers by "David L. Strayer published in 2005"

Invasion success of vertebrates in Europe and North America.

Abstract: Species become invasive if they (i) are introduced to a new range, (ii) establish themselves, and (iii) spread. To address the global problems caused by invasive species, several studies investigated steps ii and iii of this invasion process. However, only one previous study looked at step i and examined the proportion of species that have been introduced beyond their native range. We extend this research by investigating all three steps for all freshwater fish, mammals, and birds native to Europe or North America. A higher proportion of European species entered North America than vice versa. However, the introduction rate from Europe to North America peaked in the late 19th century, whereas it is still rising in the other direction. There is no clear difference in invasion success between the two directions, so neither the imperialism dogma (that Eurasian species are exceptionally successful invaders) is supported, nor is the contradictory hypothesis that North America offers more biotic resistance to invaders than Europe because of its less disturbed and richer biota. Our results do not support the tens rule either: that ≈10% of all introduced species establish themselves and that ≈10% of established species spread. We find a success of ≈50% at each step. In comparison, only ≈5% of native vertebrates were introduced in either direction. These figures show that, once a vertebrate is introduced, it has a high potential to become invasive. Thus, it is crucial to minimize the number of species introductions to effectively control invasive vertebrates.

Effective discharge analysis of ecological processes in streams

Abstract: [1] Discharge is a master variable that controls many processes in stream ecosystems. However, there is uncertainty of which discharges are most important for driving particular ecological processes and thus how flow regime may influence entire stream ecosystems. Here the analytical method of effective discharge from fluvial geomorphology is used to analyze the interaction between frequency and magnitude of discharge events that drive organic matter transport, algal growth, nutrient retention, macroinvertebrate disturbance, and habitat availability. We quantify the ecological effective discharge using a synthesis of previously published studies and modeling from a range of study sites. An analytical expression is then developed for a particular case of ecological effective discharge and is used to explore how effective discharge varies within variable hydrologic regimes. Our results suggest that a range of discharges is important for different ecological processes in an individual stream. Discharges are not equally important; instead, effective discharge values exist that correspond to near modal flows and moderate floods for the variable sets examined. We suggest four types of ecological response to discharge variability: discharge as a transport mechanism, regulator of habitat, process modulator, and disturbance. Effective discharge analysis will perform well when there is a unique, essentially instantaneous relationship between discharge and an ecological process and poorly when effects of discharge are delayed or confounded by legacy effects. Despite some limitations the conceptual and analytical utility of the effective discharge analysis allows exploring general questions about how hydrologic variability influences various ecological processes in streams.

Fatal distraction? a comparison of the cell-phone driver and the drunk driver

Abstract: The authors used a high-fidelity driving simulator to compare the performance of cell-phone drivers with drivers who were legally intoxicated from ethanol. When drivers were conversing on either a hand-held or hands-free cell-phone, their reactions were sluggish and they attempted to compensate by driving slower and increasing the following distance from the vehicle immediately in front of them. By contrast, when drivers were legally intoxicated they exhibited a more aggressive driving style, following closer to the vehicle immediately in front of them and applying more force while braking. When controlling for driving difficulty and time on task, cell-phone drivers exhibited greater impairment than intoxicated drivers.

Simulator training improves driver efficiency: transfer from the simulator to the real world

Abstract: Here we report the results of a fuel management simulation study to quantify the improvement in fuel efficiency for CDL truck drivers. Forty drivers were selected from a local commercial trucking company that maintained precise records on drivers’ history, fuel efficiency, type of vehicles driven, and trucking routes. These drivers participated in a two-hour training program that focused on ways to optimize shifting to maximize fuel efficiency (e.g., progressive shifting, double clutching, timing, and appropriate gear selection). Transfer of training was assessed over a six-month interval using measures of fuel consumption obtained by drivers in their own vehicles driving their normal route. Training increased fuel efficiency by an average of 2.8% over the six-month interval. Analyses indicated that the benefits of training persisted throughout the posttraining interval. These training benefits were obtained even for the subset of drivers who changed vehicles after training, indicating that drivers learned a general skill that transferred from one vehicle to another. Additional analyses focused on which drivers benefited the most from training. We sorted the drivers into one of four groups, based on pre-training fuel efficiency. Our analysis indicated that those drivers with the lowest pre-training fuel efficiency benefited most from training (with over 7% improvement in fuel efficiency), while those with the highest pre-training fuel efficiency did not benefit significantly from training. Together, our data validated the transfer of simulator training to realworld driving, as drivers incorporated the methods of optimal shifting into their driving practices. Moreover, the benefits of training appear to be durable and tend to benefit most those drivers whose performance was initially below the median on fuel efficiency

Why do cell phone conversations interfere with driving

Abstract: This paper investigates the impact of cell phone use while driving, on driver performance. It asks and attempts to answer 4 questions: (1) Does cell phone use (while driving) interfere with driving? (2) If cell phone use does interfere with driving, what is the basis for this interference? (3) To the extent that it is the conversation itself that interferes (and not phone dialing), what mechanisms underly this interference? (4) What is the significance to the real world of the interference produced by cell phone use while driving?

Multi-Tasking in the Automobile

Abstract: While often being reminded to pay full attention while driving an automobile, people regularly engage in a wide variety of multi-tasking activities when they are behind the wheel. Indeed, data from the 2000 US census indicates that drivers spend an average of 25.5 minutes each day commuting to work and there is a growing interest in trying to make the time spent on the roadway more productive (Reschovsky, 2004). Unfortunately, due to the inherent limited capacity of human attention (e.g., Kanheman, 1973; Navon & Gopher, 1979, Wickens, 1984), engaging in these multi-tasking activities often comes at a cost of diverting attention away from the primary task of driving. There are a number of more traditional sources of driver distraction. These “old standards” include talking to passengers, eating, drinking, lighting a cigarette, applying make-up, and listening to the radio (cf. Stutts et al., 2003). However, over the last decade many new electronic devices have been developed and are making their way into the vehicle. In many cases, these new technologies are engaging, interactive information delivery systems. For example, drivers can now surf the Internet, send and receive e-mail or fax, communicate via cellular device, and even watch television. There is good reason to believe that some of these new multi-tasking activities may be substantially more distracting than the old standards because they are more cognitively engaging and because they are often performed over more sustained periods of time. This chapter focuses on how driving is impacted by cellular communication because this is one of the most prevalent exemplars of this new class of multi-tasking activity.

Changes in Fish Assemblages in the Tidal Hudson River, New York

Abstract: The main channel of the Hudson River is a tidal estuary from its mouth in New York Harbor to Troy, New York, 247 km upstream. It drains about 35,000 km 2 and is an important navigational, commercial, and recreational system. Since the arrival of European settlers over 400 years ago, it has undergone numerous environmental changes. These changes have included channel maintenance by dredging, wholesale dumping of industrial and domestic wastes, scattered in-basin urbanization and shoreline development, deforestation of the watershed and an increase in agriculture, and water removal for commercial, industrial, and agricultural needs. In addition, the biota of the river has supported commercial and recreational harvesting, exotic species have become established, and habitats have become fragmented, replaced, changed in extent, or isolated. The tidal portion of the Hudson River is among the most-studied water bodies on Earth. We use data from surveys conducted in 1936, the 1970s, the 1980s, and the 1990s to examine changes in fish assemblages and from other sources dating back to 1842. The surveys are synoptic but use a variety of gears and techniques and were conducted by different researchers with different study goals. The scale of our assessment is necessarily coarse. Over 200 species of fish are reported from the drainage, including freshwater and diadromous species, estuarine forms, certain life history stages of primarily marine species, and marine strays. The tidal Hudson River fish assemblages have responded to the environmental changes of the last century in several ways. Several important native species appear to be in decline (e.g., rainbow smelt Osmerus mordax and Atlantic tomcod Microgadus tomcod), others, once in decline, have rebounded (e.g., striped bass Morone saxatilis), and populations of some species seem stable (e.g., spottail shiner Notropis hudsonius). No native species is extirpated from the system, and only one, shortnose sturgeon

2 – atlantic coast rivers of the northeastern united states

Abstract: The Atlantic slope region of the northeastern US stretches from the Penobscot River in northern Maine to the Rappahannock River on the lower Chesapeake Bay. This chapter discusses five large river basins in the Atlantic US–Northeast region: the Penobscot, Connecticut, Hudson, Delaware, and Susquehanna. The chapter gives a brief overview of the physiography, climate, and land use; geomorphology, hydrology, and river chemistry; and river diversity and ecology of the five river basins. The Atlantic drainage of the northeastern US is physiographically and climatically diverse. There are ten terrestrial ecoregions in the Atlantic US–Northeast region. These regions also show great biological diversity. Human impacts and special features of the rivers are also discussed. The rivers played important roles in the European colonization of North America and the establishment of the US. These rivers served as economic, transportation, and communication conduits.

Challenges in Understanding the Functions of Ecological Heterogeneity

Abstract: Ecological systems usually are heterogeneous, and this heterogeneity has important functional consequences. Nevertheless, it is not always necessary for ecologists to explicitly include this heterogeneity in their studies and models of ecological systems. Heterogeneity may be safely ignored if its grain size is much smaller than the spatial extent over which measurements are integrated or much larger than the spatial extent of the study area. Heterogeneity may be functionally unimportant if the vectors connecting patches are small or slow relative to the time span of the study or if the system is governed by processes with linear dynamics. Further, the heterogeneity expressed by some ecological systems may be amenable to analysis using simplified models. Finally, it may not be efficient to include heterogeneity in study designs or models, even if including heterogeneity would improve the study performance. Despite these considerations, ecologists will need to address heterogeneity explicitly in many cases to achieve a satisfactory understanding of ecosystem functioning, particularly for regional to global scales. Several other general issues concerning the functional consequences of heterogeneity arose at the Tenth Cary Conference. Human-caused heterogeneity probably has different characteristics and functional consequences than heterogeneity arising from other sources and therefore needs special attention. Models of heterogeneity developed in other disciplines that deal with heterogeneous, reactive systems (e.g., economics) may have application in ecology. At least some heterogeneous ecological systems appear to evolve in predictable ways because the functional consequences of heterogeneity feed back onto the structure of the system; these feedbacks need further study. 20 Challenges in Understanding the Functions of Ecological Heterogeneity

On the Fast Lane to Road Rage

Abstract: Aggressive driving and road rage are increasing. The factors that trigger road rage are not well understood. The first goal of this study was to identify conditions likely to lead to aggressive driving/road rage. The second goal was to develop a paradigm that allows for the controlled study of road rage in the laboratory setting. A total of forty-five drivers participated in the study. Twenty-three drivers received non-contingent instructions that emphasized safely driving to a rest stop. The remaining drivers received contingent instructions that added a $10 monetary incentive if they arrived at the rest stop in the top 50% of all drivers. Participants drove in two scenarios (regular / irregular flow) in a high fidelity driving simulator. We recorded cardiovascular reactivity while driving, and measured driving-related anger after completing each scenario. Overall, the driving task evoked minimal changes in blood pressure. However, an incentive by gender interaction for systolic blood pressure (SBP) reactivity indicated that males in the contingent incentive condition displayed greater SBP responses than males in the non- contingent incentive condition or females in the contingent incentive condition. Contingent versus non-contingent incentives had no effect on females' SBP response. We found no effect of incentive or traffic flow on anger, though analysis on an individual level indicated that some subjects were affected by the manipulation of driving condition. The present findings provide psychophysiological evidence that driving under time pressure and in irregular traffic flow may contribute to the genesis of road rage. Language: en

Integrative acoustic mapping reveals Hudson River sediment processes and habitats

Abstract: Rivers and estuaries around the world are the focus of human settlements and activities. Needs for clean water, ecosystem preservation, commercial navigation, industrial development, and recreational access compete for the use of estuaries, and management of these resources requires a detailed understanding of estuarine morphology and sediment dynamics. This article presents an overview of the first estuary-wide study of a heavily used estuary the Hudson River, based on high-resolution acoustic mapping of the river bottom. The integration of three high-resolution acoustic methods with extensive sampling reveals an unexpected complexity of bottom features and allows detailed classification of the benthic environment in terms of riverbed morphology, sediment type, and sedimentary processes.

Human Factors Meets Anesthesia: Advanced Training to Improve Airway Management:

Abstract: Enhanced training techniques have been successfully employed to improve performance in domains that require efficient multi-tasking skills. Some of these techniques include part task training (PTT) and variable priority training (VPT). PTT focuses on dividing complex tasks into small components followed by intensive concentrated training on each individual component. VPT focuses on optimal distribution of attention when performing multiple tasks simultaneously. The present study used VPT and PTT to train a group of first year anesthesia residents on airway management and compared performance of this group with a group of first year residents who participated in the standard curriculum. Preliminary results indicate that the group that received PTT and VPT is more successful in managing airway problems.