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Many invasive and some native tree species in North America exhibit strong allelopathic effects that may contribute to their local dominance. Pyrogenic carbon (PyC; including soot, charcoal, and black carbon) is produced by the incomplete combustion of organic matter and is widespread in forest soils. Many forms of PyC have sorptive properties that can reduce the bioavailability of allelochemicals. We investigated the potential for PyC produced by controlled pyrolysis of biomass ("biochar" [BC]) to reduce the allelopathic effects of black walnut (Juglans nigra) and Norway maple (Acer platanoides), a common native tree species and a widespread invasive species in North America, respectively. Seedling growth of two native tree species (Acer saccharinum [silver maple] and Betula papyrifera [paper birch]) in response to leaf‐litter‐incubated soils was examined; litter incubation treatments included leaves of black walnut, Norway maple, and a nonallelopathic species (Tilia americana [American basswood]) in a factorial design with varying dosages; responses to the known primary allelochemical of black walnut (juglone) were also examined. Juglone and leaf litter of both allelopathic species strongly suppressed seedling growth. BC treatments substantially mitigated these effects, consistent with the sorption of allelochemicals; in contrast no positive effects of BC were observed in leaf litter treatments involving controls or additions of nonallelopathic leaf litter. Treatments of leaf litter and juglone with BC increased the total biomass of silver maple by ~35% and in some cases more than doubled the biomass of paper birch. We conclude that BCs have the capacity to largely counteract allelopathic effects in temperate forest systems, suggesting the effects of natural PyC in determining forest community structure, and also the applied use of BC as a soil amendment to mitigate allelopathic effects of invasive tree species. [ABSTRACT FROM AUTHOR]

Downstream escapement of fishes from reservoirs via release structures can represent a loss to populations that is comparable to natural and harvest mortality. Consequently, quantifying and managing fish escapement constitute a critical component of sustainable reservoir fish management. We reviewed existing literature to assess the state of knowledge of reservoir fish escapement and found 57 unique papers published from 1942 through 2021. Early studies sought to evaluate escapement by directly capturing fish below release structures. More recently, advances in technology have enabled more detailed studies on factors influencing escapement and the influence it has on regulating reservoir fisheries. Evaluations have occurred throughout North America, assessing escapement of 49 species through a number of different outlet structures. Annual escapement estimates ranged from 0% to 100%, and escapement tended to be higher from spillways and surface release outlets compared to other outlets. Further, smaller‐bodied individuals tended to escape at higher rates than larger fish and escapement was generally positively related to reservoir discharge metrics. Sixteen papers assessed benefits of physical and nonphysical barriers for reducing reservoir fish escapement and determined that the barriers were effective for retaining fish in reservoirs. We conclude by describing management options to address escapement as well as three pressing research needs that will broaden the existing knowledge base regarding fish escapement. In light of predicted changes in precipitation events and subsequent adaptations to reservoir management, quantifying and mitigating fish escapement will be a critical component of sustainable reservoir fish management in the future. [ABSTRACT FROM AUTHOR]

Objective: Anadromous Sea Lamprey Petromyzon marinus, native to the Atlantic coast of the USA, has declined in numbers since European contact due to the construction of barrier dams. Simply addressing the stream barriers, either by removal or the addition of fishways, has not always resulted in the restoration of runs. An experimental approach of transplanting adult lamprey from existing runs into unoccupied upstream habitat was evaluated as a tool for re‐establishing annual spawning runs of the species. Methods: Two coastal watersheds without Sea Lamprey runs but with dams with fishways close to the ocean were selected for testing. Prespawn adult Sea Lamprey captured from another river were released in suitable habitat upstream of the dam in one river but not the other. Counts of adult Sea Lamprey ascending the river via the fishways in subsequent years were made and compared between the two rivers. Data of colonizing adult Sea Lamprey in other rivers were analyzed for further comparison. Result: In subsequent years, adult Sea Lamprey only immigrated into the river that received transplanted adults. When adult Sea Lampreys were finally released into the second river years later, an annual run of adult Sea Lamprey was re‐established in that stream as well. Conclusion: Prespawn adult Sea Lamprey will not emigrate from the ocean into a stream with no resident larval Sea Lamprey. The release of prespawn adults into a vacant habitat resulted in spawning, which produced a resident population of larval Sea Lamprey. Such larvae produce attractant pheromones, which is necessary to attract adults. If a stream has an extant run of Sea Lamprey, removal of a migratory barrier will result in the run expanding upstream into previously vacant habitat. Transplantation of prespawn adult Sea Lamprey can be an important management tool for restoring lost runs of this important anadromous species. Impact statementSea Lamprey is a migratory species native to the east coast of North America, and despite its negative impact to the Great Lakes, where it was accidentally introduced, it is an important part of the riverine and ocean ecosystems. The paper describes a way to help restore lost runs of Sea Lamprey. [ABSTRACT FROM AUTHOR]

Hydropower is a valuable renewable energy source, but its effects on the downstream passage of many riverine fish species are not well understood. Turbines that are designed to function as safe downstream passage routes for fish are being developed with the goal of mitigating the effects of hydropower operations on the environment. In this paper, we present the results of a study conducted with the juvenile life stage of the Alewife Alosa pseudoharengus, a major migratory species on the Atlantic coast of North America. The test was conducted at a small hydropower plant located in Freedom, Maine, with a single Restoration Hydro Turbine (RHT) operating under 7.5 m of gross head. Groups of 140–170 fish were released into the intake of a 55‐cm‐diameter RHT and were recaptured with a specialized trap at the turbine discharge outlet. The combined immediate and 48‐h survival rates (±95% CI) for all treatments, corrected for control mortality, were 98.2 ± 2.0% and 100.0 ± 6.6%, respectively. The passage of Alewives through the runner region of the turbine was also captured with high‐speed video. The results of the study demonstrate that the RHT, which is designed for fish safety, is an effective way to pass juvenile alosines downstream at hydropower facilities. [ABSTRACT FROM AUTHOR]

Walleye Sander vitreus and Yellow Perch Perca flavescens are culturally, economically, and ecologically significant fish species in North America that are affected by drivers of global change. Here, we review and synthesize the published literature documenting the effects of ecosystem changes on Walleye and Yellow Perch. We focus on four drivers: climate (including temperature and precipitation), aquatic invasive species, land use and nutrient loading, and water clarity. We identified 1,232 tests from 370 papers, split evenly between Walleye (n = 613) and Yellow Perch (n = 619). Climate was the most frequently studied driver (n = 572), and growth or condition was the most frequently studied response (n = 297). The most commonly reported relationship was "no effect" (42% of analyses), usually because multiple variables were tested and only a few were found to be significant. Overall responses varied among studies for most species‐response–driver combinations. For example, the influence of invasive species on growth of both Walleye and Yellow Perch was approximately equally likely to be positive, negative, or have no effect. Even when results were variable, important patterns emerged; for example, growth responses of both species to temperature were variable, but very few negative responses were observed. A few relationships were relatively consistent across studies. Invasive species were negatively associated with Walleye recruitment and abundance, and higher water clarity was negatively associated with Walleye abundance, biomass, and production. Some variability in responses may be due to differences in methodology or the range of variables studied; others represent true context dependence, where the effect of a driver depends on the influence of other variables. Using common metrics of impact, publishing negative results, and robust analytical approaches could facilitate comparisons among systems and provide a more comprehensive understanding of the responses of Walleye and Yellow Perch to ecosystem change. [ABSTRACT FROM AUTHOR]

Forest landscapes across western North America (wNA) have experienced extensive changes over the last two centuries, while climatic warming has become a global reality over the last four decades. Resulting interactions between historical increases in forested area and density and recent rapid warming, increasing insect mortality, and wildfire burned areas, are now leading to substantial abrupt landscape alterations. These outcomes are forcing forest planners and managers to identify strategies that can modify future outcomes that are ecologically and/or socially undesirable. Past forest management, including widespread harvest of fire‐ and climate‐tolerant large old trees and old forests, fire exclusion (both Indigenous and lightning ignitions), and highly effective wildfire suppression have contributed to the current state of wNA forests. These practices were successful at meeting short‐term demands, but they match poorly to modern realities. Hagmann et al. review a century of observations and multi‐scale, multi‐proxy, research evidence that details widespread changes in forested landscapes and wildfire regimes since the influx of European colonists. Over the preceding 10 millennia, large areas of wNA were already settled and proactively managed with intentional burning by Indigenous tribes. Prichard et al. then review the research on management practices historically applied by Indigenous tribes and currently applied by some managers to intentionally manage forests for resilient conditions. They address 10 questions surrounding the application and relevance of these management practices. Here, we highlight the main findings of both papers and offer recommendations for management. We discuss progress paralysis that often occurs with strict adherence to the precautionary principle; offer insights for dealing with the common problem of irreducible uncertainty and suggestions for reframing management and policy direction; and identify key knowledge gaps and research needs. [ABSTRACT FROM AUTHOR]

Many secondary deciduous forests of eastern North America are approaching a transition in which mature early‐successional trees are declining, resulting in an uncertain future for this century‐long carbon (C) sink. We initiated the Forest Accelerated Succession Experiment (FASET) at the University of Michigan Biological Station to examine the patterns and mechanisms underlying forest C cycling following the stem girdling‐induced mortality of >6,700 early‐successional Populus spp. (aspen) and Betula papyrifera (paper birch). Meteorological flux tower‐based C cycling observations from the 33‐ha treatment forest have been paired with those from a nearby unmanipulated forest since 2008. Following over a decade of observations, we revisit our core hypothesis: that net ecosystem production (NEP) would increase following the transition to mid‐late‐successional species dominance due to increased canopy structural complexity. Supporting our hypothesis, NEP was stable, briefly declined, and then increased relative to the control in the decade following disturbance; however, increasing NEP was not associated with rising structural complexity but rather with a rapid 1‐yr recovery of total leaf area index as mid‐late‐successional Acer, Quercus, and Pinus assumed canopy dominance. The transition to mid‐late‐successional species dominance improved carbon‐use efficiency (CUE = NEP/gross primary production) as ecosystem respiration declined. Similar soil respiration rates in control and treatment forests, along with species differences in leaf physiology and the rising relative growth rates of mid‐late‐successional species in the treatment forest, suggest changes in aboveground plant respiration and growth were primarily responsible for increases in NEP. We conclude that deciduous forests transitioning from early to middle succession are capable of sustained or increased NEP, even when experiencing extensive tree mortality. This adds to mounting evidence that aging deciduous forests in the region will function as C sinks for decades to come. [ABSTRACT FROM AUTHOR]

Lakes without road or vehicular trail access (i.e., remote lakes) are becoming increasingly scarce in North America. In the Boreal Shield, road construction for forestry operations is probably the prime factor affecting the scarcity of remote lakes. To assess the effects of forestry roads on lake access, this paper develops and tests a model that predicts the occurrence of road or vehicular trail access to lakes in northern Ontario. The results of a probit model support the hypothesis that increased forestry activity near lakes (as measured by road density within 1 km of the lake and the proximity of the lake to two-lane roads) results in increased likelihood of access. We also hypothesized that lake size, the presence of particular fish species, and the proximity of the lake to human communities would increase the likelihood of access. Except for no effect from the presence of trout Salvelinus species, the analyses supported these hypotheses. The predictive validity of the model was tested with holdout data from two other areas of northern Ontario. Strong support for the model was found from analyses of receiver operating characteristic curves for the two holdout data sets. Management scenarios from the model were used to illustrate the potential effects of forestry roads on access development to remote lakes. Our model predicts that in areas where forestry operations occur, development of access to lake shorelines will probably occur, especially on large-sized lakes containing walleyes Sander vitreus. Proactive management involving the closure of forestry roads is probably needed to retain remote lakes in areas with high levels of forestry activity. [ABSTRACT FROM AUTHOR]

Climate is changing across a range of scales, from local to global, but ecological consequences remain difficult to understand and predict. Such projections are complicated by change in the connectivity of resources, particularly water, nutrients, and propagules, that influences the way ecological responses scale from local to regional and from regional to continental. This paper describes ecological responses to expected changes in four key meso-scale drivers that influence the ecosystems of the North American continental interior: drought, warming, snowpack disappearance, and altered fire regimes. Changes in these drivers will affect, for example, atmospheric smoke, dust, and reactive nitrogen concentrations; stream discharge; nitrate concentrations; sediment loads; and the vector-borne spread of invasive species and infectious diseases. A continental network of sensors and simulation models is required to detect changes in the transport vectors - atmospheric, hydrologic, and mechanized - that connect spatial scales. Knowledge of these downwind, downstream, and down-corridor effects will be critical if we are to understand and forecast responses to climate change at regional to continental scales. [ABSTRACT FROM AUTHOR]

Many technical and environmental variables affect radio wave transmission and reception in aquatic environments. We used a controlled experimental design in three large North American rivers (Illinois and Mississippi rivers, Illinois, and Skeena River, British Columbia) to examine the effects of water conductivity, transmitter depth, electromagnetic noise, antenna height, and transmitter type on detection distance. Detection distance was significantly affected by water conductivity, transmitter depth, and electromagnetic noise from a boat motor. Detection distance and maximum depth of signal reception increased with decreasing conductivity except at conductivities from 60 to 90 µS/cm (Skeena River). In contrast to terrestrial radiotelemetry, antenna height did not significantly affect detection distance. We also determined that a transmitter with a 3.5-V battery had an approximately 2.5 times greater detection distance than a transmitter with a 1.5-V battery. We provide quantitative results for several variables influencing radio wave transmission and reception, and we present two regression equations that can be used by researchers to obtain estimated detection distances in rivers of similar conductivity and depth. Furthermore, we compared our detection distances with those calculated from theoretical equations and found that our field results yielded higher detection distances. We strongly believe that there are gaps between results reported in technical papers and those obtained in field method studies; we argue for more collaborative research between aquatic telemetry users and engineers to reduce the current need for trial and error in telemetry study design. [ABSTRACT FROM AUTHOR]

This paper describes the curriculum design and enhancements of dental gross anatomy courses at three universities in North America. The greatest problem for gross anatomy faculty is making the regions of the body below the neck relevant to dental students for their future clinical education as well as the longer term dental practice. The proposed solutions demonstrated in the three courses range from satisfying the student's grade and test requirements, such as passing the anatomical sciences section of the National Board Dental Examination Part I, to making the material relevant to clinical dentistry. Strategies to increase relevance include incorporating clinical faculty into the gross anatomy course and integrating dental clinical material into the course. Lastly, pedagogical innovations include peer teaching, the use of the Internet and intranet for examination preparation, and the animation of dental procedures to illustrate relevant anatomy to dentistry. [ABSTRACT FROM AUTHOR]