Adolescent Binge Drinking Is Associated With Accelerated Decline of Gray Matter Volume

The age- and time-dependent effects of binge drinking on adolescent brain development have not been well characterized even though binge drinking is a health crisis among adolescents. The impact of binge drinking on gray matter volume (GMV) development was examined using 5 waves of longitudinal data from the National Consortium on Alcohol and NeuroDevelopment in Adolescence study. Binge drinkers (n = 166) were compared with non-binge drinkers (n = 82 after matching on potential confounders). Number of binge drinking episodes in the past year was linked to decreased GMVs in bilateral Desikan-Killiany cortical parcellations (26 of 34 with P < 0.05/34) with the strongest effects observed in frontal regions. Interactions of binge drinking episodes and baseline age demonstrated stronger effects in younger participants. Statistical models sensitive to number of binge episodes and their temporal proximity to brain volumes provided the best fits. Consistent with prior research, results of this study highlight the negative effects of binge drinking on the developing brain. Our results present novel findings that cortical GMV decreases were greater in closer proximity to binge drinking episodes in a dose-response manner. This relation suggests a causal effect and raises the possibility that normal growth trajectories may be reinstated with alcohol abstinence.

Substance use patterns in 9-10 year olds: Baseline findings from the adolescent brain cognitive development (ABCD) study

BACKGROUND

The Adolescent Brain Cognitive Development ™ Study (ABCD Study®) is an open-science, multi-site, prospective, longitudinal study following over 11,800 9- and 10-year-old youth into early adulthood. The ABCD Study aims to prospectively examine the impact of substance use (SU) on neurocognitive and health outcomes. Although SU initiation typically occurs during teen years, relatively little is known about patterns of SU in children younger than 12.

METHODS

This study aims to report the detailed ABCD Study® SU patterns at baseline (n = 11,875) in order to inform the greater scientific community about cohort's early SU. Along with a detailed description of SU, we ran mixed effects regression models to examine the association between early caffeine and alcohol sipping with demographic factors, externalizing symptoms and parental history of alcohol and substance use disorders (AUD/SUD).

PRIMARY RESULTS

At baseline, the majority of youth had used caffeine (67.6 %) and 22.5 % reported sipping alcohol (22.5 %). There was little to no reported use of other drug categories (0.2 % full alcohol drink, 0.7 % used nicotine, <0.1 % used any other drug of abuse). Analyses revealed that total caffeine use and early alcohol sipping were associated with demographic variables (p's<.05), externalizing symptoms (caffeine p = 0002; sipping p = .0003), and parental history of AUD (sipping p = .03).

CONCLUSIONS

ABCD Study participants aged 9-10 years old reported caffeine use and alcohol sipping experimentation, but very rare other SU. Variables linked with early childhood alcohol sipping and caffeine use should be examined as contributing factors in future longitudinal analyses examining escalating trajectories of SU in the ABCD Study cohort.

Physical structure and biological composition of canopies in tropical secondary and old-growth forests

The area of tropical secondary forests is increasing rapidly, but data on the physical and biological structure of the canopies of these forests are limited. To obtain such data and to measure the ontogeny of canopy structure during tropical rainforest succession, we studied patch-scale (5 m2) canopy structure in three areas of 18-36 year-old secondary forest in Costa Rica, and compared the results to data from old-growth forest at the same site. All stands were sampled with a stratified random design with complete harvest from ground level to the top of the canopy from a modular portable tower. All canopies were organized into distinct high- and low-leaf-density layers (strata), and multiple strata developed quickly with increasing patch height. The relation of total Leaf Area Index (LAI, leaf area per area of ground) to patch canopy height, the existence of distinct high and low leaf- density layers (strata and free air spaces), the depth and LAI of the canopy strata and free air spaces, and the relation of the number of strata to patch canopy height were remarkably constant across the entire successional gradient. Trees were the most important contributor to LAI at all stages, while contribution of palm LAI increased through succession. We hypothesize that canopy physical structure at the patch scale is driven by light competition and discuss how this hypothesis could be tested. That canopy physical structure was relatively independent of the identity of the species present suggests that canopy physical structure may be conserved even as canopy floristics shift due to changing climate.

Baseline brain function in the preadolescents of the ABCD Study

The Adolescent Brain Cognitive Development (ABCD) Study® is a 10-year longitudinal study of children recruited at ages 9 and 10. A battery of neuroimaging tasks are administered biennially to track neurodevelopment and identify individual differences in brain function. This study reports activation patterns from functional MRI (fMRI) tasks completed at baseline, which were designed to measure cognitive impulse control with a stop signal task (SST; N = 5,547), reward anticipation and receipt with a monetary incentive delay (MID) task (N = 6,657) and working memory and emotion reactivity with an emotional N-back (EN-back) task (N = 6,009). Further, we report the spatial reproducibility of activation patterns by assessing between-group vertex/voxelwise correlations of blood oxygen level-dependent (BOLD) activation. Analyses reveal robust brain activations that are consistent with the published literature, vary across fMRI tasks/contrasts and slightly correlate with individual behavioral performance on the tasks. These results establish the preadolescent brain function baseline, guide interpretation of cross-sectional analyses and will enable the investigation of longitudinal changes during adolescent development.

Tropical tree size-frequency distributions from airborne lidar

In tropical rainforests, tree size and number density are influenced by disturbance history, soil, topography, climate, and biological factors that are difficult to predict without detailed and widespread forest inventory data. Here, we quantify tree size-frequency distributions over an old-growth wet tropical forest at the La Selva Biological Station in Costa Rica by using an individual tree crown (ITC) algorithm on airborne lidar measurements. The ITC provided tree height, crown area, the number of trees >10 m height and, predicted tree diameter, and aboveground biomass from field allometry. The number density showed strong agreement with field observations at the plot- (97.4%; 3% bias) and tree-height-classes level (97.4%; 3% bias). The lidar trees size spectra of tree diameter and height closely follow the distributions measured on the ground but showed less agreement with crown area observations. The model to convert lidar-derived tree height and crown area to tree diameter produced unbiased (0.8%) estimates of plot-level basal area and with low uncertainty (6%). Predictions on basal area for tree height classes were also unbiased (1.3%) but with larger uncertainties (22%). The biomass estimates had no significant bias at the plot- and tree-height-classes level (-5.2% and 2.1%). Our ITC method provides a powerful tool for tree- to landscape-level tropical forest inventory and biomass estimation by overcoming the limitations of lidar area-based approaches that require local calibration using a large number of inventory plots.

0068 Circadian Alignment Predicts Neural Response to Monetary Reward in Late Adolescent Drinkers

Introduction

Abundant evidence from animal models implicates the circadian system in modulating the brain’s reward circuitry, but evidence in humans has been more limited. In particular, published evidence has relied on self-report and/or behavioral proxies of circadian misalignment and cross-sectional designs. Here, we employed objective measures and a prospective design to assess whether circadian alignment predicts the neural response to reward in a sample of late adolescent drinkers.

Methods

Participants included 23 late adolescents (18–22 y/o; 14 females) reporting weekly alcohol use. Participants completed pre-weekend (Thursday) circadian phase assessments via the dim light melatonin onset (DLMO). Sleep-wake timing was assessed via wrist actigraphy (midpoint of sleep on Tuesday and Wednesday prior to DLMO assessment). Circadian alignment was operationalized as the DLMO-midsleep interval. Neural response to reward was assessed via a card-guessing monetary reward fMRI task; analyzed on reward anticipation and reward win relative to neutral conditions. Mean BOLD signal was extracted from two regions-of-interest (striatum and medial prefrontal cortex, mPFC) for analyses in regression models, accounting for sex and scan order (participants also completed scans on Monday in counterbalanced order, not reported here).

Results

Shorter DLMO-midsleep intervals (i.e., greater misalignment) predicted lower striatal response to anticipated reward (beta=0.48,p=0.02) and showed a trend towards predicting lower mPFC response to anticipated reward (beta=0.39,p=0.06). No statistically-significant effects were found for reward win. Notably, a lower striatal response to anticipated reward correlated with more binge-drinking episodes in the past 30 days, but was not associated with alcohol use in the weekend immediately following the scan.

Conclusion

Our findings provide preliminary evidence of proximal associations between objectively-determined circadian alignment and the neural response to anticipated monetary reward. Ongoing work in a larger sample of adolescents aims to replicate this finding and more definitively determine its relevance to adolescent drinking.

Support

This work was supported by the National Institute on Alcohol Abuse and Alcoholism (R21 AA023209; R01 AA025626).

Addressing the opioid crisis: social and behavioral research contributions at the National Institutes of Health

This commentary highlights current NIH efforts aimed at addressing the opioid crisis, specifically activities related to behavioral and social science research. Implications for this commentary will inform researchers, practitioners, and policymakers on current endeavors and future funding opportunities.

Three decades of annual growth, mortality, physical condition, and microsite for ten tropical rainforest tree species

In lowland tropical rainforest, hundreds of tree species typically occur within mesoscale landscapes (50-500 ha). There is no consensus ecological theory that accounts for the coexistence of so many species with similar morphologies and the same fundamental requirements of light, nutrients, water, and physical space. In part this is due to the limited understanding of post-establishment ecology for the vast majority of tropical tree species. Of even more concern is the lack of understanding of how these trees are responding to on-going atmospheric and climatic changes. Here we present long-term data on the post-establishment ecology of ten species of tropical rainforest trees that span a broad life-history spectrum. The study site was upland (non-swamp) old-growth tropical wet forest at the La Selva Biological Station (N.E. Costa Rica). Focal individuals from established seedlings to mature trees were assessed annually, with an emphasis on accuracy and long-term consistency of the observations. The annual time-step, rare for longterm studies in tropical rainforest, captures the typically abrupt changes in forest structure and light environments, the frequent instances of major physical damage, and the trees' responses to these events and to interannual and long-term climatic variation. With the completion of the study in 2016, the data for survivorship, growth, and microsite conditions span 4,499 individuals and 34 yr. The first ten years of these data were published as an Ecology/Ecological Archives data paper in 2000 (Clark and Clark 2000), with two subsequent update publications (Clark and Clark 2006, 2012). This final update adds the final six years of observations, digitized field comments, and histories of points of measurement on the trees. The metadata now include the scanned original field data-sheets for the entire study and a narrative detailing the annual qa/qc of the data. The data set is unique for its scope (years of continuous annual measurements, number of monitored individuals), the in-depth documentation, and the unrestricted data access. The data have been used to study life history patterns, tree ecology through ontogeny, and effects on tree performance from interannual and long-term climatic and atmospheric change. They have also contributed to numerous remote-sensing studies. No copyright or proprietary restrictions are associated with the use of this data set other than citation of the paper; the authors believe scientific data should be freely available for scientific use. The authors would appreciate notification of when and how data are used, but this is discretionary on the part of the data users and is in no sense mandatory.

Impact of mild to severe hemophilia on engagement in recreational activities by US men, women, and children with hemophilia B: The Bridging Hemophilia B Experiences, Results and Opportunities into Solutions (B-HERO-S) study

The psychosocial impact of hemophilia on activities was recently investigated in the Hemophilia Experiences, Results and Opportunities (HERO) study (675 people with hemophilia and 561 caregivers of children with hemophilia in 10 countries). The impact of hemophilia B may not be accurately reflected in the HERO results, as ~75% of respondents described issues affecting males with hemophilia A. To address the needs of this population, the Bridging Hemophilia B Experiences, Results and Opportunities Into Solutions (B-HERO-S) was developed as a pilot study in the United States in collaboration with the hemophilia community. The analysis reported here assessed engagement in recreational activities and changes to treatment regimens around activities as reported by 299 adults with hemophilia B and 150 caregivers of children with hemophilia B. Nearly all adults with hemophilia B (98%) experienced a negative impact on their participation in recreational activities due to hemophilia-related issues, and most caregivers (90%) reported that hemophilia B had a negative impact on their child's engagement in recreational activities. One of the main reasons identified for discontinuing past activities was the risk of bruising or bleeding (adults/children with hemophilia B, 49%/41%). In particular, adults with hemophilia B reported a history of activity-related bleeding, and most adults decreased their participation in high-risk activities as they aged. Substantial percentages of adults and children with hemophilia B (including mild/moderate severity) altered their treatment regimens to accommodate planned activities. These findings may help inform guidelines for individualizing treatment regimens around participation in recreational activities based on hemophilia severity, baseline factor level, and activity risk and intensity.

Charting a Course for Implementation Research in Oral Health

Knowledge Transfer Statement: This article provides an overview of implementation science and outlines NIDCR's interest and commitment to research that decreases time from development through implementation of evidence-based oral health interventions.

Mental Health Issues and Special Care Patients

Mental illness is a major health issue in the world today, yet often remains misunderstood, unrecognized, and undertreated. Patients suffering from severe psychiatric disorders generally display poor oral health, often as a consequence of both lifestyle and avoidant-type behaviors that become exacerbated by their illness. Individuals with severe mental illness display a greater incidence of oral disease compared with a similar demographic not dealing with these particular disorders. Efforts to enhance the oral health of these vulnerable patients will play a significant role in the overall rebuilding of their self-esteem and contribute positively to their journey toward stability and recovery.

Design and interpretation of clinical research studies in oral medicine: a brief review

The objective of this short review is to help researchers improve the designs of their clinical studies. Also included is a discussion of the level of evidence provided by the various clinical research study designs.

Disruptive behavior disorders and indicators of disinhibition in adolescents: The BRIEF-SR, anti-saccade task, and D-KEFS color-word interference test

Disinhibition contributes to the development of disruptive behavior disorders (DBD) in adolescents. Self-reports and behavioral tasks are commonly used to assess disinhibition, each with their unique strengths and limitations. Accordingly, it is important to identify which measure, or combination thereof, is the most effective in predicting DBD symptoms. This study assessed the relationship between DBD (symptoms of ADHD/ODD/CD) and two behavioral disinhibition tasks: the anti-saccade task and the D-KEFS color-word interference test, as well as a self-report measure (the BRIEF-SR). The results indicated that the BRIEF-Inhibit scale accounted for the majority of the variance in the DBD sum score. The anti-saccade task and color-word interference test were also significantly associated with an increase in the number of DBD symptoms endorsed. These behavioral tasks accounted for 9% additional variance than the self-report alone. Therefore, combining self-report measures with behavioral disinhibition tasks may provide the most thorough assessment of adolescent DBD.

Tropical rain forest structure, tree growth and dynamics along a 2700-m elevational transect in Costa Rica

Rapid biological changes are expected to occur on tropical elevational gradients as species migrate upslope or go extinct in the face of global warming. We established a series of 9 1-ha plots in old-growth tropical rainforest in Costa Rica along a 2700 m relief elevational gradient to carry out long-term monitoring of tropical rain forest structure, dynamics and tree growth. Within each plot we mapped, identified, and annually measured diameter for all woody individuals with stem diameters >10 cm for periods of 3-10 years. Wood species diversity peaked at 400-600 m and decreased substantially at higher elevations. Basal area and stem number varied by less than two-fold, with the exception of the 2800 m cloud forest summit, where basal area and stem number were approximately double that of lower sites. Canopy gaps extending to the forest floor accounted for <3% of microsites at all elevations. Height of highest crowns and the coefficient of variation of crown height both decreased with increasing elevation. Rates of turnover of individuals and of stand basal area decreased with elevation, but rates of diameter growth and stand basal area showed no simple relation to elevation. We discuss issues encountered in the design and implementation of this network of plots, including biased sampling, missing key meteorological and biomass data, and strategies for improving species-level research. Taking full advantage of the major research potential of tropical forest elevational transects will require sustaining and extending ground based studies, incorporation of new remotely-sensed data and data-acquisition platforms, and new funding models to support decadal research on these rapidly-changing systems.

Response of an old-growth tropical rainforest to transient high temperature and drought

Tropical rainforests have experienced episodes of severe heat and drought in recent decades, and climate models project a warmer and potentially drier tropical climate over this century. However, likely responses of tropical rainforests are poorly understood due to a lack of frequent long-term measurements of forest structure and dynamics. We analyzed a 12-year record (1999-2010) of 47 817 annual measurements of canopy height to characterize the response of an old-growth Neotropical rainforest to the severe heat and drought associated with the 1997-1998 El Niño. Well-drained soils on slopes and plateaus experienced a threefold increase in the fraction of the landscape in gaps (≤2 m) and a reduction in the fraction in high canopy (>15 m) causing distributions of canopy height to depart from equilibrium for a period of 2-3 years. In contrast, forests on low-lying alluvial terraces remained in equilibrium and were nearly half as likely to experience upper canopy (>15 m) disturbance over the 12 years of observation. Variation in forest response across topographic positions suggests that tropical rainforests are more sensitive to moisture deficits than high temperature and that topography likely structures landscape-level variation in the severity of drought impacts.

Compositional shifts in Costa Rican forests due to climate-driven species migrations

Species are predicted to shift their distributions upslope or poleward in response to global warming. This prediction is supported by a growing number of studies documenting species migrations in temperate systems but remains poorly tested for tropical species, and especially for tropical plant species. We analyzed changes in tree species composition in a network of 10 annually censused 1-ha plots spanning an altitudinal gradient of 70-2800 m elevation in Costa Rica. Specifically, we combined plot data with herbarium records (accessed through GBIF) to test if the plots' community temperature scores (CTS, average thermal mean of constituent species weighted by basal area) have increased over the past decade as is predicted by climate-driven species migrations. In addition, we quantified the contributions of stem growth, recruitment, and mortality to the observed patterns. Supporting our a priori hypothesis of upward species migrations, we found that there have been consistent directional shifts in the composition of the plots, such that the relative abundance of lowland species, and hence CTS, increased in 90% of plots. The rate of the observed compositional shifts corresponds to a mean thermal migration rate (TMR) of 0.0065 °C yr(-1) (95% CI = 0.0005-0.0132 °C yr(-1) ). While the overall TMR is slower than predicted based on concurrent regional warming of 0.0167 °C yr(-1) , migrations were on pace with warming in 4 of the 10 plots. The observed shifts in composition were driven primarily by mortality events (i.e., the disproportionate death of highland vs. lowland species), suggesting that individuals of many tropical tree species will not be able to tolerate future warming and thus their persistence in the face of climate change will depend on successful migrations. Unfortunately, in Costa Rica and elsewhere, land area inevitably decreases at higher elevations; hence, even species that are able to migrate successfully will face heightened risks of extinction.

Neuroimaging methods for adolescent substance use disorder prevention science

Magnetic resonance imaging (MRI) methods safely provide in vivo indicators of cerebral macrostructure, microstructure, and activation that can be examined in relation to substance use disorder (SUD) risks and effects. This article will provide an overview of MRI approaches, including volumetric measures, diffusion tensor imaging, and functional MRI, that have been applied to studies of adolescent neuromaturation in relationship to risk phenotypes and adolescent SUD. To illustrate these applications, examples of research findings will be presented. MRI indicators have demonstrated that neurobiological maturation continues throughout adolescence. MRI research has suggested that variations in neurobiological maturation may contribute to SUD risk, and that substance use adversely influences adolescent brain development. Directly measured neurobiological variables may be viable preventive intervention targets and outcome indicators. Further research is needed to provide definitive findings on neurodevelopmental immaturity as an SUD risk and to determine the directions such observations suggest for advancing prevention science.

Local technicians in long-term research projects: evaluation of 25 years experience in an active tropical research station

Most field ecology is conceived and financed by scientists from urban areas but is actually carried out in rural areas. Field staff can either be imported from urban areas or recruited from local residents. We evaluated the advantages and disadvantages of involving rural residents as local technicians over a 25- year period at active field research site in Costa Rica. We defined "local technicians" as local residents with no university education who acquired significant experience in field data collection, data management and/or laboratory work. We analyzed the experiences of incorporating these technicians into field research in developing countries from the points of view of scientist and of the local technicians themselves. Primary data were written responses from to a standardized survey of 19 senior scientists and Ph.D. students,and results from standardized personal interviews with 22 local technicians. Researchers highlighted the advantages of highly-skilled technicians with minimal staff turnover, as well as the technicians' knowledge of local ecological conditions. Local technicians considered the primary advantages of their jobs to be opportunities for continuing education training in science as well as cultural enrichment through interactions with people of different cultures. The main challenges identified by researchers were the lack of long-term funding for projects and extended training required for local technicians. Local technicians can be of great benefit to research projects by providing high-quality data collection at reasonable costs with low staff turnover. Over the last 25 years the research model at the field station we studied has evolved to the point that most long-term projects now depend heavily on local technicians. This model of involving local technicians in long-term research has multiple benefits for the researchers, the technicians and the local community, and could be adapted to a variety of settings in rural areas of developing countries.

A novel statistical method for classifying habitat generalists and specialists

We develop a novel statistical approach for classifying generalists and specialists in two distinct habitats. Using a multinomial model based on estimated species relative abundance in two habitats, our method minimizes bias due to differences in sampling intensities between two habitat types as well as bias due to insufficient sampling within each habitat. The method permits a robust statistical classification of habitat specialists and generalists, without excluding rare species a priori. Based on a user-defined specialization threshold, the model classifies species into one of four groups: (1) generalist; (2) habitat A specialist; (3) habitat B specialist; and (4) too rare to classify with confidence. We illustrate our multinomial classification method using two contrasting data sets: (1) bird abundance in woodland and heath habitats in southeastern Australia and (2) tree abundance in second-growth (SG) and old-growth (OG) rain forests in the Caribbean lowlands of northeastern Costa Rica. We evaluate the multinomial model in detail for the tree data set. Our results for birds were highly concordant with a previous nonstatistical classification, but our method classified a higher fraction (57.7%) of bird species with statistical confidence. Based on a conservative specialization threshold and adjustment for multiple comparisons, 64.4% of tree species in the full sample were too rare to classify with confidence. Among the species classified, OG specialists constituted the largest class (40.6%), followed by generalist tree species (36.7%) and SG specialists (22.7%). The multinomial model was more sensitive than indicator value analysis or abundance-based phi coefficient indices in detecting habitat specialists and also detects generalists statistically. Classification of specialists and generalists based on rarefied subsamples was highly consistent with classification based on the full sample, even for sampling percentages as low as 20%. Major advantages of the new method are (1) its ability to distinguish habitat generalists (species with no significant habitat affinity) from species that are simply too rare to classify and (2) applicability to a single representative sample or a single pooled set of representative samples from each of two habitat types. The method as currently developed can be applied to no more than two habitats at a time.

Height is more important than light in determining leaf morphology in a tropical forest

Both within and between species, leaf physiological parameters are strongly related to leaf dry mass per area (LMA, g/m2), which has been found to increase from forest floor to canopy top in every forest where it has been measured. Although vertical LMA gradients in forests have historically been attributed to a direct phenotypic response to light, an increasing number of recent studies have provided evidence that water limitation in the upper canopy can constrain foliar morphological adaptations to higher light levels. We measured height, light, and LMA of all species encountered along 45 vertical canopy transects across a Costa Rican tropical rain forest. LMA was correlated with light levels in the lower canopy until approximately 18 m sample height and 22% diffuse transmittance. Height showed a remarkably linear relationship with LMA throughout the entire vertical canopy profile for all species pooled and for each functional group individually (except epiphytes), possibly through the influence of gravity on leaf water potential and turgor pressure. Models of forest function may be greatly simplified by estimating LMA-correlated leaf physiological parameters solely from foliage height profiles, which in turn can be assessed with satellite- and aircraft-based remote sensing.

A comparison of the key-peck and treadle-press operants in the pigeon: differential-reinforcement-of-low-rate schedule of reinforcement

Key pecking and treadle pressing in pigeons were compared under concurrent (key-treadle) and single-operant differential-reinforcement-of-low-rate schedules of food reinforcement ranging from 5 to 60 sec (concurrent procedure) or 5 to 120 sec (single-operant procedure). Under both procedures, the two operants followed the same general law: decreasing response rate and reinforcement rate and increasing number of responses per reinforcement as a function of increasing schedule interval. High correlations were found between key pecking and treadle pressing for the measures of response rate, reinforcement rate, and responses per reinforcement. Regression equations allowed the prediction of treadle pressing from key pecking. More bursting occurred in responding to the key, and key pecking showed a more precise temporal discrimination than treadle pressing. A test for sequential dependencies between key and treadle responses showed significant dependencies not only under the concurrent procedure but also in data created artificially by merging key and treadle sequences from different pigeons under the concurrent procedure and from the same pigeon under the single-operant procedure. It seems likely that the sequential dependencies found were due to the independent action of the schedule on each operant and that behavioral dependencies did not occur with the concurrent training procedure. The key-peck operant does not appear to have any special qualities that preclude its use in discovering general laws of behavior, at least under the differential-reinforcement-of-low-rate schedule. The usefulness of the key peck in other situations requires direct experimental study.

Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

Decisions about recreational beach closures would be enhanced if better estimates of surfzone contaminant transport and dilution were available. In situ methods for measuring fluorescent Rhodamine WT dye tracer in the surfzone are presented, increasing the temporal and spatial resolution over previous surfzone techniques. Bubbles and sand suspended by breaking waves in the surfzone interfere with in situ optical fluorometer dye measurements, increasing the lower bound for dye detection ( approximately 1 ppb) and reducing (quenching) measured dye concentrations. Simultaneous turbidity measurements are used to estimate the level of bubble and sand interference and correct dye estimates. After correction, root-mean-square dye concentration errors are estimated to be < 5% of dye concentration magnitude, thus demonstrating the viability of in situ surfzone fluorescent dye measurements. The surfzone techniques developed here may be applicable to other environments with high bubble and sand concentrations (e.g., cascading rivers and streams).

Pervasive canopy dynamics produce short-term stability in a tropical rain forest landscape

A fundamental property of all forest landscapes is the size frequency distribution of canopy gap disturbances. But characterizing forest structure and changes at large spatial scales has been challenging and most of our understanding is from permanent inventory plots. Here we report the first application of light detection and ranging remote sensing to measurements of canopy disturbance and regeneration in an old-growth tropical rain forest landscape. Pervasive local height changes figure prominently in the dynamics of this forest. Although most canopy gaps recruited to higher positions during 8.5 years, size frequency distributions were similar at two points in time and well-predicted by power-laws. At larger spatial scales (hundreds of ha), height increases and decreases occurred with similar frequency and changes to canopy height that were analysed using a height transition matrix suggest that the distribution of canopy height at the beginning of the study was close to the projected steady-state equilibrium under the recent disturbance regime. Taken together, these findings show how widespread local height changes can produce short-term stability in a tropical rain forest landscape.

Characteristics of DUI offenders convicted in wet, dry, and moist counties

Although several studies have examined the effectiveness of local alcohol sales policies on reducing the incidence of driving under the influence (DUI), less is known about whether characteristics of DUI offenders convicted in alcohol-restricted areas differ from those convicted in areas where alcohol is more readily available. A total of 21,647 DUI assessment records were divided into four groups based on the alcohol sales policy of the county of conviction and were compared. DUI offenders convicted in counties that limit or ban the sale of alcohol were more likely to be male, have more drug problems, meet DSM-IV-TR substance abuse or dependence criteria, and have multiple DUI convictions. Implications for practitioners and policy makers are discussed.

Explaining variation in tropical plant community composition: influence of environmental and spatial data quality

The degree to which variation in plant community composition (beta-diversity) is predictable from environmental variation, relative to other spatial processes, is of considerable current interest. We addressed this question in Costa Rican rain forest pteridophytes (1,045 plots, 127 species). We also tested the effect of data quality on the results, which has largely been overlooked in earlier studies. To do so, we compared two alternative spatial models [polynomial vs. principal coordinates of neighbour matrices (PCNM)] and ten alternative environmental models (all available environmental variables vs. four subsets, and including their polynomials vs. not). Of the environmental data types, soil chemistry contributed most to explaining pteridophyte community variation, followed in decreasing order of contribution by topography, soil type and forest structure. Environmentally explained variation increased moderately when polynomials of the environmental variables were included. Spatially explained variation increased substantially when the multi-scale PCNM spatial model was used instead of the traditional, broad-scale polynomial spatial model. The best model combination (PCNM spatial model and full environmental model including polynomials) explained 32% of pteridophyte community variation, after correcting for the number of sampling sites and explanatory variables. Overall evidence for environmental control of beta-diversity was strong, and the main floristic gradients detected were correlated with environmental variation at all scales encompassed by the study (c. 100-2,000 m). Depending on model choice, however, total explained variation differed more than fourfold, and the apparent relative importance of space and environment could be reversed. Therefore, we advocate a broader recognition of the impacts that data quality has on analysis results. A general understanding of the relative contributions of spatial and environmental processes to species distributions and beta-diversity requires that methodological artefacts are separated from real ecological differences.

First direct landscape-scale measurement of tropical rain forest Leaf Area Index, a key driver of global primary productivity

Leaf Area Index (leaf area per unit ground area, LAI) is a key driver of forest productivity but has never previously been measured directly at the landscape scale in tropical rain forest (TRF). We used a modular tower and stratified random sampling to harvest all foliage from forest floor to canopy top in 55 vertical transects (4.6 m(2)) across 500 ha of old growth in Costa Rica. Landscape LAI was 6.00 +/- 0.32 SEM. Trees, palms and lianas accounted for 89% of the total, and trees and lianas were 95% of the upper canopy. All vertical transects were organized into quantitatively defined strata, partially resolving the long-standing controversy over canopy stratification in TRF. Total LAI was strongly correlated with forest height up to 21 m, while the number of canopy strata increased with forest height across the full height range. These data are a benchmark for understanding the structure and functional composition of TRF canopies at landscape scales, and also provide insights for improving ecosystem models and remote sensing validation.

First direct landscape-scale measurement of tropical rain forest Leaf Area Index, a key driver of global primary productivity

Leaf Area Index (leaf area per unit ground area, LAI) is a key driver of forest productivity but has never previously been measured directly at the landscape scale in tropical rain forest (TRF). We used a modular tower and stratified random sampling to harvest all foliage from forest floor to canopy top in 55 vertical transects (4.6 m(2)) across 500 ha of old growth in Costa Rica. Landscape LAI was 6.00 +/- 0.32 SEM. Trees, palms and lianas accounted for 89% of the total, and trees and lianas were 95% of the upper canopy. All vertical transects were organized into quantitatively defined strata, partially resolving the long-standing controversy over canopy stratification in TRF. Total LAI was strongly correlated with forest height up to 21 m, while the number of canopy strata increased with forest height across the full height range. These data are a benchmark for understanding the structure and functional composition of TRF canopies at landscape scales, and also provide insights for improving ecosystem models and remote sensing validation.