Search

As one of the leading causes of death within both the developed and developing world, stroke is a worldwide problem. Risk factors can be identified and controlled at the level of lifestyle changes; however, genetic components of stroke have yet to be identified. The identification of such genetic components is critical in the understanding, diagnosis, and treatment of stroke in the future. This review focuses on the genetic determinants of stroke in both human and experimental systems. Mendelian disorders, candidate genes, and twin studies provide evidence for a strong genetic component of stroke. Genome-wide scanning in both human and animal models has led to the identification of regions of the genome that contain genes for stroke susceptibility and sensitivity. Animal models of stroke allow for environmental control and genetic homogeneity, not possible within a human population, and therefore are essential for the dissection of this complex, multifactorial disorder. Future genetic and genomic strategies and their role in ultimate causative gene identification are discussed.

Ecologists have long postulated that density-dependent mortality maintains high tree diversity in the tropics1,2,3,4,5,6. If species experience greater mortality when abundant, then more rare species can persist1,2,7,8,9. Agents of density-dependent mortality (such as host-specific predators, and pathogens) may be more prevalent or have stronger effects in tropical forests, because they are not limited by climatic factors1,2,3,4,5. If so, decreasing density-dependent mortality with increasing latitude could partially explain the observed latitudinal gradient in tree diversity4,5,6. This hypothesis has never been tested with latitudinal data. Here we show that several temperate tree species experience density-dependent mortality between seed dispersal and seedling establishment. The proportion of species affected is equivalent to that in tropical forests6,10,11,12,13,14,15,16, failing to support the hypothesis that this mechanism is more prevalent at tropical latitudes. We further show that density-dependent mortality is misinterpreted in previous studies. Our results and evidence from other studies suggest that density-dependent mortality is important in many forests. Thus, unless the strength of density-dependent mortality varies with latitude, this mechanism is not likely to explain the high diversity of tropical forests.

We tested hypotheses concerning the response of forest succession to elevated CO2 in the FACTS-1 site at the Duke Forest. We quantified growth and survival of naturally recruited seedlings, tree saplings, vines, and shrubs under ambient and elevated CO2. We planted seeds and seedlings to augment sample sites. We augmented CO2 treatments with estimates of shade tolerance and nutrient limitation while controlling for soil and light effects to place CO2 treatments within the context of natural variability at the site. Results are now being analyzed and used to parameterize forest models of CO2 response.

Planning and decision-making can be improved by access to reliable forecasts of ecosystem state, ecosystem services, and natural capital. Availability of new data sets, together with progress in computation and statistics, will increase our ability to forecast ecosystem change. An agenda that would lead toward a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services requires a process that engages scientists and decision-makers. Interdisciplinary linkages are necessary because of the climate and societal controls on ecosystems, the feedbacks involving social change, and the decision-making relevance of forecasts.

A quantitative trait locus on chromosome 5 in the rat is linked to sensitivity to brain ischemia in the stroke-prone spontaneously hypertensive rat (SHRSP). The genes encoding atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) that map to this location have been excluded as candidate genes. We examined dishevelled-1 (DVL-1) as a further candidate gene. DVL-1 had not yet been identified in the rat, but Anp, Bnp, and DVL-1 map to the homologous regions of the rat chromosome 5 quantitative trait locus in both mice and man. Furthermore, DVL-1 is involved in the Notch signalling system, which plays a role in the disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, the symptoms of, which include ischaemic stroke. We show with radiation hybrid mapping that rat DVL-1 indeed maps to chromosome 5, where it is positioned immediately next to microsatellite marker D5Rat49. We sequenced the complete coding sequence and a large part of the intronic genomic sequence for the SHRSP strain and its reference Wistar-Kyoto strain. The DVL-1 sequence in the two strains was identical. Our results essentially exclude the DVL-1 gene as the cause for sensitivity to cerebral ischaemic insult in this rat model of stroke.

We have previously demonstrated that the SHRSP Y chromosome contains a locus that contributes to hypertension in SHRSP/WKY F2 hybrids and that SHRSP exhibit an increased vulnerability to focal cerebral ischemia after permanent middle cerebral artery occlusion (MCAO). This increased vulnerability is inherited as a codominant trait, and a putative role for the Y chromosome has been suggested in F1 hybrids. The objective of this study was to investigate further the role of Y chromosome in blood pressure (BP) regulation and in the vulnerability to cerebral ischemia. We have constructed consomic strains by selectively replacing the Y chromosome from WKY rats with that of SHRSP, and vice versa, by using a marker-assisted breeding strategy. Permanent MCAO was carried out by electrocoagulation, with infarct volume expressed as a percentage of the ipsilateral hemisphere. Systolic blood pressure was measured by radiotelemetry during a baseline period of 5 weeks followed by a 3-week period of salt loading. We observed that the transfer of the Y chromosome from WKY onto SHRSP background significantly reduced systolic BP in consomic strains, SP.WKYGlaY w (n=6) versus SHRSP (n=6) (209.2±10.4 mm Hg versus 241.7±7.7 mm Hg, F=5.88, P =0.038) during the salt-loading period. In the reciprocal consomic strain, WKY.SPGlaY s (n=5), systolic BP was increased compared with WKY parental strain (n=6) (147.6±2.4 mm Hg versus 132.6±5.1 mm Hg, F=6.11, P =0.035) during baseline. Infarct volumes in consomic strains were not significantly different from their respective parental strain: WKY.SPGlaY s (n=7) versus WKY (n=7), 22.8±3.7% versus 22.2±8.0%, 95% CI=−12.7, 4.2, P =0.3; SP.WKYGlaY w (n=7) versus SHRSP (n=6), 37.7±4.4% versus 33.6±7.6%, 95% CI=−20.3, 12.1, P =0.5. We conclude that the SHRSP Y chromosome harbors a locus contributing to systolic BP, whereas no contribution to vulnerability to cerebral ischemia can be detected.

The hypertensive transgenic rat model TGR(mRen2)27 has been used to investigate the development of cardiac and vascular hypertrophy in response to two different drug regimes. Cardiac hypertrophy was shown to be related to age and gender with the copy number of mouse renin transgenes having an additive effect. A similar observation was noted for hypertrophy in the vasculature, which was assessed using flow cytometry cell cycle DNA analysis of aortic vascular smooth muscle cells. Chronic treatment from weaning with equihypotensive doses of perindopril (2 mg/kg/day) or hydralazine and hydrochlorothiazide (4 mg/day of each) prevented the development of cardiac hypertrophy. Perindopril treatment also effectively prevented the development of vascular hypertrophy; however, treatment with hydralazine and hydrochlorothiazide was not as effective despite equivalent blood pressure reduction. These studies have demonstrated the presence of marked vascular and cardiac hypertrophy in the hypertensive transgenic TGR(mRen2)27 model of hypertension. Furthermore, these results provide new evidence to support the role of a locally activated renin angiotensin system in the blood vessel wall, which is involved in the pathogenesis of vascular hypertrophy in this transgenic rat model.

Plants constantly monitor their light environment in order to grow and develop optimally, in part through use of the phytochromes, which sense red/far-red light. A phytochrome binding protein, PKS1 (phytochrome kinase substrate 1), was identified that is a substrate for light-regulated phytochrome kinase activity in vitro. In vivo experiments suggest that PKS1 is phosphorylated in a phytochrome-dependent manner and negatively regulates phytochrome signaling. The data suggest that phytochromes signal by serine-threonine phosphorylation.

An Introduction to Sediment Records of Biomass Burning.- I -The Issues Addressed by Sediment Combustion Records.- Proposed Bio-Geological and Chemical Based Terminology for Fire-Altered Plant Matter.- Background and Local Charcoal in Sediments: Scales of Fire Evidence in the Paleorecord.- Reconstruction of Paleo-Fire Through Climate and Eco-System Models.- The Culture of Fire: An Introduction to Anthropogenic Fire History.- II - Characterizing Combustion Products in Sediments.- Characterization of Particulate Products of Biomass Combustion.- Polycyclic Aromatic Hydrocarbons in Sedimentary Records of Biomass Burning.- III - Particulate Emissions and Transport to Sediments.- Biomass Consumption and Behavior of Wildland Fires in Boreal, Temperate, and Tropical Ecosystems: Parameters Necessary to Interpret Historic Fire Regimes and Future Fire Scenarios.- Biomass Burning Emissions and the Atmosphere.- Atmospheric Transports of Particulate and Gaseous Products by Fires.- IV - Stratigraphic Records.- Pre-Quaternary Records of Wildfire.- Marine Sediments: A Reservoir for Black Carbon and Their Use as Spatial and Temporal Records of Combustion.- Reconstructing Environmental Impacts of Fire from the Holocene Sedimentary Record.- The Sedimentary Record of Fire in Montane Meadows, Sierra Nevada, California, USA: a Preliminary Assessment.- Late Quaternary Climate, Fire, and Vegetation Dynamics.- Holocene Records of Fire from the Boreal and Temperate Zones of Europe.- Controls on Charcoal Distribution in Lake Sediments: Case Studies from Yellowstone National Park and Northwestern Minnesota.- Reconstruction of Fire Disturbance and Forest Succession from Fossil Pollen in Lake Sediments: Potential and Limitations.- The Contribution of Humans to Past Biomass Burning in the Tropics.- Lake Sediment Records of Fossil Fuel-Derived Carbonaceous Aerosols from Combustion.- V - Future Directions.- Report of the Working Discussion Groups.- Cooperation of the Paleofire Science Community with Interdisciplinary Fire Research Programs.

Biomass burning, one of the most important global sources of particulate matter, produces both airborne particles that may influence global and regional climate, and particles incorporated into sediments that provide records of past local, regional, and global impacts of biomass burning. Determining the mass concentrations, chemical compositions, and physical properties of these particles is a prerequisite for assessing the environmental effects of biomass burning. In this Chapter we describe methods for chemical and physical characterization of airborne and sedimentary particles used in biomass burning studies, with particular emphasis on the carbonaceous material. For each method we review the principles, problems and uncertainties and, when possible, discuss analytical features presently or potentially applicable to characterizing both airborne and sediment particles.

Stratigraphic charcoal data are used to interpret combustion at a range of spatial and temporal scales. Interpretation is based on assumptions regarding how charred particles are transported to and deposited in sedimentary basins and how the variance structure of stratigraphie profiles is affected by transport. Here we examine evidence for “background” and “local” signals in stratigraphie data based on total abundances of particles and on distributions of particle sizes. Distributions of particle sizes in sediments and in the atmosphere show remarkable consistency, with a ~ 2% decrease in frequency for a 1% increase in particle diameter. Relatively large differences in source distance are required to produce differences in particle size distributions. Thus, stratigraphie samples with disproportionate representation of large particles are likely to represent a nearby source. Simple transport models suggest particles 100 to 101 μm have substantially longer atmospheric residence times than do particles > 102 μm. Several factors can produce a “dichotomy” (background vs local) in total abundances of charred particles. Transport during a single experimental burn shows abrupt decline in accumulation at a burn edge and relatively constant values out to 102 m. Saltation and redistribution of particles in surface runoff following fire are expected to focus accumulation within a catchment (local scale). The amount of transport that occurs by these modes is unstudied. The stratigraphie record appears to support a distinction between local, catchment sources vs. fires burning at greater distance. Charcoal profiles often show distinct peaks when fires burn within a lake catchment but are unaffected by fires that occur at greater distance. Broad subcontinental scale patterns in particle accumulation indicate shifts in regional importance of fire. The low frequency variance can be extracted from charcoal profiles and used to differentiate local from background changes in burning. Although the empirical data are still far too few to permit good characterization of particle transport, the evidence suggests utility in the concepts of background and local signals in profiles.

Biomass burning has become recognized as a key element of global change. Best estimates of current and past emissions suggest fire now profoundly affects atmospheric chemistry, the carbon cycle, and climate and may have done so for millions of years. Literature values place carbon sequestration during biomass burning in excess of 20% of the total anthropogenic C releases to the atmosphere, which, failing oxidative losses, would tie up the globe’s surface C in less than 106 yr (Goldberg 1985). And the relative importance of biomass burning may have been greater in the past, before large increases in fossil fuel combustion (Clark et al. 1996). The potential importance of these burning rates for biodiversity, C and O cycles, air quality, and climate have impressed a diverse community of ecologists and atmospheric chemists and served as a theme for a recent Dahlem workshop some of us organized on biomass burning (Crutzen and Goldammer 1993). That workshop together with subsequent discussions identified key challenges that require multidisciplinary efforts i) to better characterize combustion products that occur in sediments, including char, soot/fly ash, and polycyclic aromatic hydrocarbons (PAH’s), ii) to calibrate these constituents against atmospheric measurements from wildland and prescribed fire emissions, and iii) to estimate the spatial and temporal patterns in combustion emissions at scales of individual burns to the globe.

Background Large-scale forest conservation projects are underway in the Brazilian Amazon but little is known regarding their public health impact. Current literature emphasizes how land clearing increases malaria incidence, leading to the conclusion that forest conservation decreases malaria burden. Yet, there is also evidence that proximity to forest fringes increases malaria incidence, which implies the opposite relationship between forest conservation and malaria. We compare the effect of these environmental factors on malaria and explore its implications. Methods and Findings Using a large malaria dataset (∼1,300,000 positive malaria tests collected over ∼4.5 million km2), satellite imagery, permutation tests, and hierarchical Bayesian regressions, we show that greater forest cover (as a proxy for proximity to forest fringes) tends to be associated with higher malaria incidence, and that forest cover effect was 25 times greater than the land clearing effect, the often cited culprit of malaria in the region. These findings have important implications for land use/land cover (LULC) policies in the region. We find that cities close to protected areas (PA’s) tend to have higher malaria incidence than cities far from PA’s. Using future LULC scenarios, we show that avoiding 10% of deforestation through better governance might result in an average 2-fold increase in malaria incidence by 2050 in urban health posts. Conclusions Our results suggest that cost analysis of reduced carbon emissions from conservation efforts in the region should account for increased malaria morbidity, and that conservation initiatives should consider adopting malaria mitigation strategies. Coordinated actions from disparate science fields, government ministries, and global initiatives (e.g., Reduced Emissions from Deforestation and Degradation; Millenium Development Goals; Roll Back Malaria; and Global Fund to Fight AIDS, Tuberculosis and Malaria), will be required to decrease malaria toll in the region while preserving these important ecosystems.

We present a method for identifying analogs for past fire regimes and use it to assess similarity between late Quaternary fire regimes in northern Wisconsin and central New York and a reference set of charcoal series from just prior to presettlement time. The analog method is based on comparisons of distributions of charcoal accumulation rates from annually laminated sediments using a Kolmogorov-Smirnov two-sample D statistic (D). D is a nonparametric statistic expressing the difference between distributions that does not require assumptions concerning the shape of the distributions (e.g. normality, homoscedasticity) and it summarizes differences in a single index. Our study consists of (i) mapping D values obtained by comparisons between pairs of ‘reference’ charcoal series from the immediate presettlement (calibration) and (ii) identifying possible presettlement analogs from this reference set for Late Quaternary charcoal distributions. Our calibration analysis identified geographic transitions in charcoal transition that were much steeper than apparent from pollen data. Otherwise, geographic patterns in presettlement charcoal and pollen are comparable, including a group of oak/hardwood forest sites in Wisconsin, central Ontario, and New York having similar values, and another group of mostly northern hardwood/hemlock sites in Pennsylvania and Maine. Application to charcoal series dated after 11 000 yr BP at Wisconsin and New York suggests that fire regimes may have been different from those occurring at any of our reference sites. Differences in seasonality of climates and different fuel structures are a possible explanation.

Two qualities distinguish the paleo record of fire in boreal regions. First is its highly fragmentary nature in light of the importance of boreal forests for carbon storage and emissions to the atmosphere. One might expect boreal forests to be a focus of research on impacts of temperature change and biospheric feedbacks due to C release. Fire can have effects on the C balance of individual stands that persist for decades in boreal regions (Van Cleve and Viereck 1981). Combustion-produced elemental (graphitic) C can have several important environmental impacts, influencing climate (Shaw 1982; Rosen et al. 1984; Ch’ylek et al. 1984; Penner et al. 1991), air quality (Sandberg et al. 1979), human health (Laflamme and Hites 1978), and the concentrations of greenhouse gases in the atmosphere (Seiler and Crutzen 1980; Crutzen and Andreae 1990; Crutzen and Goldammer 1993). Stratigraphic records of several important combustion products (e.g. charcoal, fly ash, reduced organic tracers) exist from some regions, but there is a conspicous lack of synthesis needed to establish baseline (i.e. pre-industrial) biomass burning emissions (Malingreau et al. 1993). Such records are particularly scarce in boreal regions (Clark and Robinson 1993).

The neutral model says that the relative abundance of a species is as likely to increase as it is to decrease, because species are ecologically identical1. This hypothesis can be rejected if variance does not increase over time2. We used a more powerful test, based on comparisons among locations, to show that variability stabilizes and, for most species, decreases over thousands of years3. The neutral model also predicts that after a perturbation, relative abundance is as likely to increase as it is to decrease.

Halley and Iwasa and I agree that simple models can be valuable [1xNeutral theory as a predictor of avifaunal extinctions after habitat loss. Halley, J.M. and Iwasa, Y. Proc. Natl. Acad. Sci. U.S.A. 2011; 108: 2316–2321CrossRef | PubMed | Scopus (28)See all References, 2xThe coherence problem with the unified neutral theory of biodiversity. Clark, J.S. Trends Ecol. Evol. 2012; 27: 198–202Abstract | Full Text | Full Text PDF | PubMed | Scopus (28)See all References]. Their fine study shows that a model can ignore factors contributing to extinction (habitat, dispersal, life history, physiology, exotic enemies, human activity) and still describe species losses from islands or patches of different size. Their letter [3xNeutrality without incoherence: a response to Clark. Halley, J.M. and Iwasa, Y. Trends Ecol. Evol. 2012; 27: 363Abstract | Full Text | Full Text PDF | PubMed | Scopus (5)See all References][3] acknowledges our shared agreement on the utility of simple models. We part company on what this has to do with the Unified Neutral Theory of Biodiversity.Given the issues I raised in [2xThe coherence problem with the unified neutral theory of biodiversity. Clark, J.S. Trends Ecol. Evol. 2012; 27: 198–202Abstract | Full Text | Full Text PDF | PubMed | Scopus (28)See all References, 4xBeyond neutral science. Clark, J.S. Trends Ecol. Evol. 2009; 24: 8–15Abstract | Full Text | Full Text PDF | PubMed | Scopus (70)See all References], which they objected to in [1xNeutral theory as a predictor of avifaunal extinctions after habitat loss. Halley, J.M. and Iwasa, Y. Proc. Natl. Acad. Sci. U.S.A. 2011; 108: 2316–2321CrossRef | PubMed | Scopus (28)See all References][1], in the Cell Press Discussion on neutral theory (http://news.cell.com/discussions/trends-in-ecology-and-evolution/ecological-neutral-theory-useful-model-or-statement-of-ignorance) and again in their letter, I would expect clarification on how their study supports the Unified Neutral Theory of Biodiversity. In both [2xThe coherence problem with the unified neutral theory of biodiversity. Clark, J.S. Trends Ecol. Evol. 2012; 27: 198–202Abstract | Full Text | Full Text PDF | PubMed | Scopus (28)See all References][2] and [4xBeyond neutral science. Clark, J.S. Trends Ecol. Evol. 2009; 24: 8–15Abstract | Full Text | Full Text PDF | PubMed | Scopus (70)See all References][4] I addressed the many definitions, including that species are functionally equivalent, that all have the same fitness or that all have the same probability of recruitment success. I addressed the belief that the Unified Neutral Theory of Biodiversity is a null model for niche differences or that it represents an alternative to niche or fitness differences. I demonstrated why neutral models do not assume that all individuals obey the same rules of engagement, and why they do not predict that coexistence occurs in the absence of niches. This list of motivations, assumptions, and interpretations may not be exhaustive, but it is close.The statement in the letter by Halley and Iwasa most relevant to Neutral Theory does not respond to the question of how their study supports it:It is not necessary to buy into any interpretation of the niche (or the stronger claims of unification) to apply these mechanisms and get useful results that fit the data well.Halley and Iwasa seem to be saying that it does not matter what niches are. One of the few persistent claims about Neutral Theory has been that it is an alternative to niche theory. Since Neutral Theory does not address niches or lack thereof [5xResolving the biodiversity debate. Clark, J.S. et al. Ecol. Lett. 2007; 10: 647–662CrossRef | PubMed | Scopus (98)See all References][5], proponents now simply avoid saying what a niche is. So how does a study such as [3xNeutrality without incoherence: a response to Clark. Halley, J.M. and Iwasa, Y. Trends Ecol. Evol. 2012; 27: 363Abstract | Full Text | Full Text PDF | PubMed | Scopus (5)See all References][3] support it? What definition of Neutral Theory does it support?My paper that Halley and Iwasa object to in their letter [2xThe coherence problem with the unified neutral theory of biodiversity. Clark, J.S. Trends Ecol. Evol. 2012; 27: 198–202Abstract | Full Text | Full Text PDF | PubMed | Scopus (28)See all References][2] focuses on the need to move beyond claims that the Unified Neutral Theory is being criticized for reliance on simple models. From introductory statistics courses onward we learn to construct simple models and penalize large ones. Nobody wants a complex model when a simple one will suffice. There is no debate about this. The criticism of Neutral Theory concerns vague and shifting definitions and misinterpretation of models.The Unified Neutral Theory finally appears to be no more than a defense of simple models. If proponents now acknowledge that it has nothing to say about niche differences [6xThe case for ecological neutral theory. Rosindell, J. et al. Trends Ecol. Evol. 2012; 27: 203–208Abstract | Full Text | Full Text PDF | PubMed | Scopus (56)See all References][6], the Unified Theory defaults to a statement that simple models can be useful, apparently the point of [3xNeutrality without incoherence: a response to Clark. Halley, J.M. and Iwasa, Y. Trends Ecol. Evol. 2012; 27: 363Abstract | Full Text | Full Text PDF | PubMed | Scopus (5)See all References][3]. All ecologists – including those who do not count themselves as theorists – should be concerned when such basic modeling principles are taken as a unified theory for our discipline.

Background Nut-bearing trees, including oaks (Quercus spp.), are considered to be highly dispersal limited, leading to concerns about their ability to colonize new sites or migrate in response to climate change. However, estimating seed dispersal is challenging in species that are secondarily dispersed by animals, and differences in disperser abundance or behavior could lead to large spatio-temporal variation in dispersal ability. Parentage and dispersal analyses combining genetic and ecological data provide accurate estimates of current dispersal, while spatial genetic structure (SGS) can shed light on past patterns of dispersal and establishment. Methodology and Principal Findings In this study, we estimate seed and pollen dispersal and parentage for two mixed-species red oak populations using a hierarchical Bayesian approach. We compare these results to those of a genetic ML parentage model. We also test whether observed patterns of SGS in three size cohorts are consistent with known site history and current dispersal patterns. We find that, while pollen dispersal is extensive at both sites, the scale of seed dispersal differs substantially. Parentage results differ between models due to additional data included in Bayesian model and differing genotyping error assumptions, but both indicate between-site dispersal differences. Patterns of SGS in large adults, small adults, and seedlings are consistent with known site history (farmed vs. selectively harvested), and with long-term differences in seed dispersal. This difference is consistent with predator/disperser satiation due to higher acorn production at the low-dispersal site. While this site-to-site variation results in substantial differences in asymptotic spread rates, dispersal for both sites is substantially lower than required to track latitudinal temperature shifts. Conclusions Animal-dispersed trees can exhibit considerable spatial variation in seed dispersal, although patterns may be surprisingly constant over time. However, even under favorable conditions, migration in heavy-seeded species is likely to lag contemporary climate change. ISSN:1932-6203

Spatial trends in pre-industrial biomass burning emissions for eastern North America were reconstructed from sediment charcoal data. Petrographic thin sections were prepared from varved lake sediments along a transect of sites extending from NW Minnesota eastward to NE Maine. Results showed an exponential decline in charcoal abundance with distance east from the prairie/forest border. This result quantifies burning along the broad climate/vegetation gradient from xeric woodland to mesic eastern deciduous forest. Post-settlement charcoal accumulation showed no such geographic pattern, varying from site-to-site, likely reflecting local variability in land use and combustion sources. Results suggest the total emissions of large (> 10 μm diameter) charcoal particles decreased by a factor of three during the twentieth century.

BACKGROUND: A common challenge to the study of several infectious diseases consists in combining limited cross-sectional survey data, collected with a more sensitive detection method, with a more extensive (but biased) syndromic sentinel surveillance data, collected with a less sensitive method. Our article describes a novel modeling framework that overcomes this challenge, resulting in enhanced understanding of malaria in the Western Brazilian Amazon. METHODOLOGY/PRINCIPAL FINDINGS: A cohort of 486 individuals was monitored using four cross-sectional surveys, where all participants were sampled regardless of symptoms (aggressive-active case detection), resulting in 1,383 microscopy and 1,400 polymerase chain reaction tests. Data on the same individuals were also obtained from the local surveillance facility (i.e., passive and active case detection), totaling 1,694 microscopy tests. Our model accommodates these multiple pathogen and case detection methods. This model is shown to outperform logistic regression in terms of interpretability of its parameters, ability to recover the true parameter values, and predictive performance. We reveal that the main infection determinant was the extent of forest, particularly during the rainy season and in close proximity to water bodies, and participation on forest activities. We find that time residing in Acrelandia (as a proxy for past malaria exposure) decreases infection risk but surprisingly increases the likelihood of reporting symptoms once infected, possibly because non-naïve settlers are only susceptible to more virulent Plasmodium strains. We suggest that the search for asymptomatic carriers should focus on those at greater risk of being infected but lower risk of reporting symptoms once infected. CONCLUSIONS/SIGNIFICANCE: The modeling framework presented here combines cross-sectional survey data and syndromic sentinel surveillance data to shed light on several aspects of malaria that are critical for public health policy. This framework can be adapted to enhance inference on infectious diseases whenever asymptomatic carriers are important and multiple datasets are available.

Many of the features long viewed as among the most important influences on tree population dynamics have only recently begun to be incorporated in analyzable models. These processes tend to operate at several spatial and temporal scales, and they represent factors that produce and/or depend on heterogeneity. Some of these considerations include: Growth-dependent thinning: Thinning rates at local scales (100 to 102 m2) are determined by growth rates. There is no “carrying capacity” at such scales in the traditional sense, because plants are continually growing and, therefore, thinning. Changing importance of density-dependent and density-independent mortality: The relative importances of different mortality risks change with canopy coverage, and they influence recruitment. Thinning caused by crowding has different demographic consequences than do juvenile death and senescence. Episodic recruitment: Seedling establishment is locally episodic, being associated with “disturbance”, i.e. specific types of mortality.

A quantitative description of patchiness and the assessment of its effects on ecological and evolutionary processes represents a major research focus as well as a challenge for ecologists and evolutionary biologists (e.g., Pickett and White 1985, Shorrocks and Swingland 1990, Kolasa and Pickett 1991). Patchiness is neither unique in origin nor characteristic of particular temporal or spatial scales; rather, patchiness emerges from the interactions between physical and biotic processes (Levin 1976, 1978) and is apparent at any scale of resolution. The scale dependency of patchiness and the complexity it generates calls attention to the need for new modeling approaches where spatial and temporal heterogeneity is explicitly incorporated (e.g., Hassell et al. 1991, Deutschman et al., this volume) and for new methodological tools to deal with problems of scale (e.g., Milne 1992, Garcia-Moliner et al., this volume).

DNA aneuploidy and p53 or c-erbB-2 expression were simultaneously measured in 29 breast tumours by two-colour flow cytometry. (i) The majority of tumours had some cells expressing either p53 (5–68%) or c-erbB-2 (1–56%). (ii) Expression of p53 and c-erbB-2 was observed mainly in the aneuploid population of mixed aneuploid and diploid tumours but there was no significant correlation with a specific DNA index. Aneuploid tumours contained higher percentages of c-erbB-2 positive cells (average 25%) than purely diploid tumours (average 15%) but this just failed to reach significance (P = 0.074). No relevant trends were noted for p53 expression. (iii) Significantly increased c-erbB-2 expression was observed in stage 2 tumours (26%) compared to stage 1 tumours (12%) (P = 0.001) with no trend evident for p53 expression. (iv) The metastatic tumour in the axillary node contained similar or slightly higher percentages of positive cells than the matched primary tumour.

A U.S. National Science Foundation workshop brought together more than 40 researchers from different disciplines to discuss applications of data assimilation techniques in ecology, define major scientific questions to be addressed, and identify future research challenges. The field of ecology has become a data-rich enterprise, due largely to rapid development of measurement sensors and long-term accumulation of data from research networks. With the implementation of the National Ecological Observatory Network (NEON), a network with different kinds of sensors at many locations over the nation, large volumes of ecological data will be generated every day. There will be an unprecedented demand to convert the massive raw data into ecologically meaningful products using data assimilation techniques.

Path analysis was used to determine the importance of long-term disturbance regime and the relative importances of correlations among vegetation patterns, disturbance history, and nitrogen (N) mineralization in old-growth forests of northwestern Minnesota. Leaf biomass (estimated by allometric equations), fire history (from fire scars on Pinus resinosa trees), and N mineralization rates (estimated from incubationsin situ) were determined from sample plots dominated by

This, the July issue of TREE, is the second of two issues commissioned to celebrate the 20th birthday of the journal. The people shown on the cover of the issue are a sample of those who will shape our science in the future. They are a non-random sample: we posted a call on two widely distributed e-circulation lists for pictures of graduate students and young post-docs working in ecology and evolution today. Several established figures accused us of ageism and others tried to slip themselves in (including a C. Darwin, who submitted the only painted portrait). In the end, we received ∼375 pictures of people who looked like they had the chronological potential to be driving our field in 20 years. Not all could appear, so we left the final cut to the graphic designer. We hope the cover will at least generate some mirth in 20 years time.But what will ecologists and evolutionary biologists be doing 20 years from now? Predicting science is for the foolhardy, but current opportunities are easier to spot. There is clearly much scope for new work in all areas of current activity: it is hard to identify an area active now that might be solved and abandoned in two decades. To the openings discussed in many of the birthday articles, we add the following more general observations.Destruction, degradation and disasters all provide scientific opportunities. Two decades ago, ecologists actively debated the relative merits of observations versus small-scale experiments, and the need for simple models. The various approaches are still with us, but these are already being enriched by new attention to natural and unintended human-caused ‘experiments’ that provide insights at relevant scales. Invasive species enable us to observe species interactions in the context of climate and soil variation and in situ food webs. Changes in atmospheric CO2 concentrations have provided canopy-scale context for insights gleaned from small chambers, revealing why simplistic interpretations might not apply to productivity on a rapidly changing Earth. Climate change will soon be revealing how fast species can migrate. Chernobyl makes it possible to look at the importance of genetic perturbations in real ecosystems (and whether human occupancy of an area is worse for wildlife than is radiation). Vaccination enables an analysis of the selective removal of part of a biota. And, sadly, habitat loss is already enriching our understanding of demography and genetics at low population densities.People calling themselves systems biologists are emerging in all branches of biology, excited about the prospect of iterative dialogue between mathematical models and huge amounts of molecular and physiological data. Ecologists and evolutionary biologists have been systems biologists for at least 40 years, albeit with different data. Established systems biologists have tremendous opportunities for contributing to the study of suborganismal systems, not least because they understand that mastering complexity is not simply a matter of more data or bigger computers. Inevitably, the new systems biologists will also manage to merge new models and vast data streams in novel ways that analysts of ecological systems will surely be able to exploit. And, ultimately, suborganismal mechanistic function is of interest because of what it does at an organismal or even ecosystem level. Yet the analysis of genotype × environment interactions, something that many TREE readers specialise in, is experimentally demanding, and beyond the experience (and even current interest) of most molecular and cell biologists.Biologists working at suborganismal scales continue to reveal a swathe of natural history that receives far less attention from evolutionary biologists and ecologists than is deserved. For instance, the natural history of mammalian immunology continues to be understood in ever more intricate detail. Yet there is no quantitative understanding of the population biology of interacting cell types and no predictive explanation for why the immune system is designed as it is. Much human misery is caused by immunopathology [1xEvolutionary causes and consequences of immunopathology. Graham, A.L. et al. Annu. Rev. Ecol. Evol. Syst. 2005; 36: 337–397Crossref | Scopus (154)See all References[1], yet we have no understanding of why our immune genes often harm us and, indeed, whether immune self-harm occurs in anything other than us and laboratory mice. Analogous questions apply to most areas of suborganismal physiology and cell biology.Indeed, it is striking that the attention that ecological and evolutionary biologists pay to something seems to be inversely related to the amount of mechanistic detail known about it. Is this because we have been slow to wade into the jargon-laden arena of biomedicine? Or is it because our theories do not work well when there are lots of facts? Becoming involved in biomedicine requires a detailed understanding of the experimental techniques and the jargon involved, a genuine respect for biological reality, and an ability to sort signal from noise. For ecologists and evolutionary biologists who can do this, enormous potential exists.A tension in some areas of organismal biology, which is reflected in several of the birthday articles, concerns the use of model organisms. Model organisms that are well understood by mechanistic biologists (the odd bacterial, yeast, fly, worm, rodent or weed species) have, in some cases, been used with great success to address issues in ecology and evolution, and there is undoubtedly considerably more mileage to be gained that way. However, model organisms are not typically studied in their ecological context (indeed, most have essentially no known ecology outside a laboratory container). By contrast, little mechanistic detail is known about organisms that are well studied in the wild. With technological advances, it will be increasingly possible to carry out detailed mechanistic and genetic work on non-model organisms in nature, ultimately weakening the case for studying ecology and evolution in jars. For instance, it should be soon feasible to study bacterial evolution in great detail in contexts where they cause disease. And interesting genetic polymorphisms identified in mouse and human studies could be subjected to detailed ecological genetic analyses in field populations of wild animals with known genealogies. A detailed understanding of selection on such polymorphisms has to move out of the lab or away from the constraints of a human study. However, one could argue that some areas of our work could make less use of wild, non-model organisms, and work more on laboratory models. It would be good to resolve quantitatively the evolution of sex for at least one organism.Need-driven research offers huge opportunities, not least because ecologists and particularly evolutionary biologists have been slow to fully address real world problems. For instance, had SARs persisted in the human population, would it have evolved to be more or less virulent for humans? We have no quantitatively successful explanations of virulence change for any disease. Over one million people die each year of diseases transmitted by insects but most TREE-reading entomologists do not work on these species. And, with a few notable exceptions, we have almost entirely left the evolution of drug resistance (one of the basic challenges of 21st-century medicine, and one of the prime examples of evolution in real time) in the hands of people who have no formal training in either evolution or population biology.Finally, there are enormous opportunities for communicating beyond our community. Perhaps more than ever, there is a need to get our science across in an accessible, jargon-free way that society can use. Climate change and evolution are now household words, no longer viewed as hypothetical possibilities, irrelevant to ordinary lives. Society often has strong views on our science, or wants to know about it, or has no views about things that it ought to. More than ever in the history of our subject, there are important opportunities in teaching, popularising and policy.Our subject is now so large that this monthly review journal flourishes. But a danger with large disciplines is that those in them keep busy talking only with each other. We hope that a substantial proportion of the cohort represented on the cover of this issue will consider looking outward as their careers develop. For those prepared to get out a bit, there are very real opportunities to make a difference to our discipline, to other sciences, and to society as a whole.

54 Background Localisation of QTL using a genome wide scan strategy is the first step towards gene identification. This is followed by the construction of congenics by which the existence of the QTL can be verified. Congenic strains for chromosome 2 using the Dahl S as the recipient and WKY and MNS as donors, showed variable blood pressure (BP) depending on the donor alleles 1 . Methods We used a speed congenic approach to produce several congenic strains of chromosome 2 using the SHRSP Gla and the WKY Gla as recipients to test the effect of the genetic background of a given congenic on BP. In some strains, the region introgressed was identical to avoid confounding effects of additional QTLs. Two reciprocal control congenic strains were also produced to determine the presence of any passenger loci. Baseline systolic BP was measured by radiotelemetry. Results Four congenic and 2 parental strains were phenotyped (n=3-6). Transfer of the region of rat chromosome 2 from the WKY into a SHRSP background significantly lowered both day and night-time systolic BP by approximately 16 and 20 mm Hg respectively in male congenic rats compared to the SHRSP parental strains (pet al . Hypertension 1997;30:199-202

The abundance and recruitment of oak in northeastern US forests have long been topics of speculation. While physiology and life history suggest that oak recruitment benefits from disturbance, records of disturbance that predate European influences are largely absent. Tree ring records in upland stands do not extend beyond the early 17th century, when disease and warfare depopulated much of the eastern forests (White 1991; Clark 1995). Traditional sediment analyses rarely permit reliable identification of individual burns (Patterson et al. 1987; Clark 1988a; Clark & Patterson 1997). The paucity of evidence admits lively debate on past fire importance (Hawes 1923; Raup 1937; Day 1953; Russell 1983; Myers & Peroni 1983; Patterson & Sassaman 1988). Thin section methods have recently been developed that allow reconstruction of annual fire records (Clark 1988b, 1990) and this motivated us to reconsider pre-European fire at Devil's Bathtub, NY. These methods produce consistent estimates (i) in different cores from the same lake (Clark et al. 1989), (ii) among lakes within the same landscape which can then be matched with independent fire records (Clark 1990), and (iii) within and among regions, where variations are consistent with differences in climate and vegetation (fuel load) (Clark & Royall 1995a; Clark et al. 1996a,c). Archaeological evidence agrees with increased sediment charcoal during the rise and decline of Iroquois agriculture (Clark & Royall 1995b). During the period when spruce-pine dominated at Devil's Bathtub, charcoal peaks, which occur at 80-200-year intervals, are of the same magnitude as those observed at other sites during fire years. Charcoal peaks cease abruptly with early Holocene spruce-pine declines and the expansion of hardwoods at Devil's Bathtub; no peaks occur thereafter. This lack of any fire over millennia ran counter to our expectations, and we discussed caveats and the need for more studies (Clark & Royall 1996; Clark et al. 1996b). Abrams & Seischab (1997) feel we challenged 'the fire and oak hypothesis' (Abrams 1992) and list (i) how we overlooked palaeoevidence showing fire to be important in oak forests, (ii) reasons why our lake gives biased charcoal records, (iii) reasons why the site must be unrepresentative of the kinds of oak forests Abrams (1992) meant, and (iv) why the methods are flawed and how we misinterpreted our data. I address each of these four points in turn followed by a different perspective on data evaluation.

1 Presettlement fire regimes in north-eastern North America and their dependence on climate, fuels, and cultural patterns are poorly understood due to lack of relevant historic or palaeoecological data. Annual records of sediment charcoal accumulation were compiled from seven sites spanning the last 2000 years and representing important climate, vegetation, and cultural settings. Results were compared across sites and across changes in Indian cultures to determine whether fire patterns might be explained by one or more of these variables. 2 Clearly interpretable fires were restricted to the western (most xeric) portion of our study region in Pine Hardwoods of Minnesota, a single fire in Northern Hardwoods of northern Wisconsin, and cultural burning near an Iroquois village in southern Ontario. Other sites in Northern Hardwoods and Hardwood-Hemlock forests did not show clear evidence of fire. Spectral analysis suggested instances in which local fire regimes departed from regional ones. 3 Our interpretation suggests substantially longer intervals between fires than reported in previous sediment charcoal studies. We did not find evidence for fire in mixed oak forests, where it has been speculated that fire might be necessary for oak recruitment, suggesting need for further analysis. 4 A single site in northern Wisconsin was the only Algonquin site showing a clear increase in charcoal suggesting local fire. Algonquin use of fire for hunting may not have affected our sites. A single site in Sioux territory experienced such frequent fire that cultural effects were not evident, even when Sioux were replaced by Chippewa (Algonquin) in the 18th century. One of two Iroquois sites showed clear increases in charcoal during occupation. The second site may not have had settlements nearby.

Objective To quantify vascular smooth muscle polyploidy and growth kinetics in aortic cells from stroke-prone spontaneously hypertensive rats (SHRSP) and from normotensive Wistar-Kyoto (WKY) rats, and to examine the effects of treatment with the angiotensin converting enzyme (ACE) inhibitor perindopril on these parameters. Design The following experimental groups were used: young (age 20 weeks) untreated WKY rats and untreated SHRSP; SHRSP treated with perindopril, and age- and sex-matched control SHRSP; and SHRSP treated with hydralazine and hydrochlorothiazide and age- and sex-matched control SHRSP. The effects of treatment of the SHRSP with perindopril for 30 days on vascular smooth muscle polyploidy and growth kinetics were measured and compared with the effects of equivalent antihypertensive doses of hydralazine and hydrochlorothiazide. Methods Vascular smooth muscle polyploidy was measured using flow-cytometry DNA analysis of freshly harvested cells. Growth curves were performed on cultured aortic cells. Plasma renin activity was measured by an antibody-trapping method, plasma angiotensin II (Ang II) by radioimmunoassay and plasma ACE activity by a colorimetric method. Cardiac hypertrophy was evaluated by measuring the heart weight:body weight and left ventricle + septum weight:body weight ratios. Results The SHRSP had markedly and significantly elevated G2 + M phase of the cell cycle. Treatment with perindopril resulted in a significant reduction in polyploidy in the SHRSP, whereas treatment with hydralazine and hydrochlorothiazide had no effect on the percentage of cells in the G2 + M phase of the cell cycle. The regression of polyploidy after treatment with perindopril was associated with a significant reduction in the concentration of Ang II and ACE activity, and with a significant regression of cardiac hypertrophy. Increased mitogenesis of cultured vascular smooth muscle cells from the SHRSP was not altered by treatment with perindopril. Conclusions ACE inhibition reduces vascular smooth muscle polyploidy in large conduit arteries. This type of vascular protection is mediated by the reduced Ang II and possibly by increased kinins level, rather than by the hypotensive effect alone.

This paper explores the implications for populations and ecosystems of individual plant growth. The approach focuses on dynamics within a generation, but the treatment is theoretical rather than empirical or simulation-based. Rather than attempt to elucidate size structure within the entire population, it seeks generalizations that result from population structure, without recourse to intractable models that monitor each individual

A stratigraphic study was undertaken to determine the historic role of watershed and sea—level changes on the development of Fresh Pond Marsh on Long Island's north shore. Pollen analytic, radiometric, and macrofossil techniques were aimed at differentiating among marsh, watershed, and regional changes over the last 1000 yr. A study of surface pollen distribution was conducted to determine pollen source and tidal influences on pollen deposition and to evaluate comparability of fossil pollen records from various intertidal environments. Regional and local inputs along a transect that included several tidal regimes were identified. Pollen counts from these different environments were comparable and proved useful for marsh reconstructions. Pollen analyses from the coastal marsh and a nearby lake distinguished changes in upland vegetation and cultural patterns within the watershed from those occurring regionally. Records of local pollen, foraminifera, macrofossils, rhizomes, and lithology indicated that the history of Fresh Pond Marsh has included periods of both tidal and freshwater conditions. Close dating control provided by 210Pb measurements and historically documented changes in indicator pollen taxa identified marsh responses to external influences, including dynamics of a baymouth bar, land clearing, agriculture, mosquito ditching, and sea—level fluctuations. Results showed that (1) tidal marsh sections can provide sensitive records of both upland and marsh vegetation histories, (2) pollen and macrofossil records can be closely linked to tide—gauge records and are responsive to short—term changes in sea level with a high degree of temporal resolution, and (3) upland influences can play an important role in determining the course of plant succession in the intertidal environment. Pollen provides the most sensitive record of marsh and upland development, as long as pollen source is accounted for.

Pollen data were used to reconstruct the past 340 yr of vegetational changes at Great South Beach, a system of barrier beaches east of Fire Island Inlet, Long Island, New York. The data came from cores taken along 16 transects, 6 of which are described in detail. Dates and stratigraphy from individual cores provided local environmental histories that were combined to reconstruct temporal and spatial patterns of vegetation on local and regional scales. Changes in inlet status and local disturbances accounted for much of the dynamism in vegetation. Salt marshes fringed back-barrier lagoons only when many inlets were open and saline conditions prevailed (1760 to 1835; 1931 to the present). Cyperaceae dominated marshes throughout the re- mainder of postsettlement time. Inlets affected vegetation by altering tidal range and salinity in back- barrier lagoons and provided new substrates for marsh establishment when flood-tide deltas were abandoned by inlet channels. At least once every 100 yr along the six transects, sufficient sand was deposited to destroy all vegetation. The composition of invading assemblages on primary substrates was regulated mainly by physical factors. Annual herbs, shrubs, or high-marsh plants each were "pioneers" at different localities and times. Putative "pioneer" annuals were not limited to the early stages of succession. Fluctuating water tables played an important role in determining composition of freshwater wetlands. Biotically controlled trends in plant composition could not be positively identified. The reconstructions on Great South Beach indicate tight environmental control of plant distribution but emphasize that vegetation does not achieve an equilibrium with the physical environment. Present distributions are largely the product of historical events acting together with existing conditions.

Principles from particle-motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data: (1) fires within catchments of lakes often produce no record in fossil-charcoal curves and (2) periods characterized by no local fire (e.g., 20th-century fire suppression) often display as much charcoal as times when local fire was frequent. Quantitative theory on source area, transport, deposition, and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis (pollen slides for particles 5–80 μm in diameter, petrographic thin sections for particles 50–10,000 μm diameter) and charcoal diagrams. The relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods. Charcoal recorded on pollen slides is of a size that is difficult to lift, but once entrained it remains in suspension. Thin-section charcoal is lifted at relatively low wind velocities, but it is not suspended at normal surface wind speeds. Thermal buoyancy during fire lofts charcoal above the forest canopy, depending on particle size and wind speed. Pollen-slide charcoal sizes are underrepresented near the fire, because they remain in suspension and are preferentially exported from the burn area. Thin-section charcoal is convected to lower heights on average and is deposited nearby. Following fire, thin-section charcoal is redistributed locally by wind and thus may enter lakes. Because of cohesive forces and aerodynamics, more pollen-slide charcoal remains on the ground, and less enters lakes. Source areas for pollen-slide charcoal are subcontinental to global, and diagrams of pollen-slide charcoal are biased toward nonlocal charcoal. They can be used to interpret importance of fire for broad spatial and temporal scales. Thin-section charcoal represents, the catchment fire regime. Simulation models that generate charcoal during fire, mix sediments, and then sample at specified intervals indicate that (1) in the absence of sediment mixing the pollen-slide method should consistently resolve individual fires that occur with an expectation of >30–50 yr, (2) unless samples are continuous, neither method will produce useful estimates of fire frequency, and (3) even a modest amount of sediment mixing will obscure the signal.

The temporal and spatial dynamics of tree populations in coastal forests of southeastern Long Island, New York, were reconstructed from analyses of (1) historical accounts, maps, and aerial photos, (2) field evidence of forest history, (3) age and height class distributions along the moisture gradient, and (4) fossil-pollen content of bordering salt-marsh deposits. Tide-gauge records of sea level provided independent evidence for long-term change in the physical environment (rise in sea level) that caused populations to migrate up the continental shelf. Field evidence for fire and historically documented land-use change demonstrated the important role of disturbance in the dynamics of tree populations. Spatial and temporal patterns in forests were determined by information on disturbance frequency, dispersal, generation times, and rates of change in the physical environment. Mature cohorts occupied lower elevations than did their progeny because, during the period from germination to seed production, suitable soil-moisture conditions shifted upslope in response to sea-level rise. Establish- ment of new regeneration depended on disturbances that opened the forest canopy and/or prepared seed beds. Frequent fire, land clearance and abandonment, and tree blowdowns insured opportunities for seedling establishment at higher elevations as conditions became unsuitable for regeneration on low-elevation sites. The resultant pattern of range shifts was stepwise, with waves of regeneration following disturbances and subsequent reduced seedling establishment as soil moisture continued to increase. The vegetation dynamics could be explained solely on the basis of life histories of plant species and environmental change; "emergent properties" and "successional stages" in a deterministic sense were not apparent. An understanding of successional change required information on both the spatial and temporal dimensions of vegetation pattern because composition change over time resulted from range shifts in response to environmental transition.

Clark, J.S., Overpeck, J.T., Webb III, T. and Patterson III, W.A., 1986. Pollen stratigraphic correlation and dating of barrier-beach peat sections. Rev. Palaeobot. Palynol., 47: 145--168. Coastal researchers use data from core sections to reconstruct past sedimentary environments and barrier-beach dynamics over the last 350 years. Disjunct organic and silt strata separated by sand deposits represent former salt marshes and lagoons that were buried in the normal course of barrier migration processes. Interpretations are invariably limited by a lack of close time control needed to correlate sections and to tie stratigraphic evidence to documented changes in sea level, storms, inlet activity, overwash, and human disturbances. Regional pollen spectra from organic and silt strata in a large number of barrier-beach cores have been matched with spectra from a 21°Pb and pollen-dated reference profile from the centre of the study area on Great South Beach, Long Island, New York, U.S.A. The dramatic vegetation changes following European settlement allowed for a high degree of vertical (and thus, temporal) resolution in profiles of regional pollen. For visual matching of pollen samples, percentages of agricultural-indicator types, the percentages of all regional types, stratigraphic relationships, and sediment concentrations of industrially-derived opaque spherules were considered. Chord-distance comparisons that measure the degree of dissimilarity between pairs of pollen spectra, produced the same correlations as visual estimates for 80--87% of the comparisons between spectra of post-settlement age (i.e. spectra containing agricultural indicators). These correlations were used to establish isochrones through a transect of cores across the barrier beach. 2~°Pb provided an absolute chronology for a reconstruction of geomorphic events that included inlet changes overwash, and salt-marsh formation. The advantages of the present methods for both absolute dating and chronostratigraphic correlation were evident when the age estimates derived from pollen data were compared to 29 14C dates.

Results of stratigraphic charcoal analysis from thin sections of varved lake sediments have been compared with fire scars on red pine trees in northwestern Minnesota to determine if charcoal data accurately reflect fire regimes. Pollen and opaque-spherule analyses were completed from a short core to confirm that laminations were annual over the last 350 yr. A good correspondence was found between fossil-charcoal and fire-scar data. Individual fires could be identified as specific peaks in the charcoal curves, and times of reduced fire frequency were reflected in the charcoal data. Charcoal was absent during the fire-suppression era from 1920 A.D. to the present. Distinct charcoal maxima from 1864 to 1920 occurred at times of fire within the lake catchment. Fire was less frequent during the 19th century, and charcoal was substantially less abundant. Fire was frequent from 1760 to 1815, and charcoal was abundant continuously. Fire scars and fossil charcoal indicate that fires did not occur during 1730–1750 and 1670–1700. Several fires occurred from 1640 to 1670 and 1700 to 1730. Charcoal counted from pollen preparations in the area generally do not show this changing fire regime. Simulated “sampling” of the thin-section data in a fashion comparable to pollen-slide methods suggests that sampling alone is not sufficient to account for differences between the two methods. Integrating annual charcoal values in this fashion still produced much higher resolution than the pollen-slide method, and the postfire suppression decline of charcoal characteristic of my method (but not of pollen slides) is still evident. Consideration of the differences in size of fragments counted by the two methods is necessary to explain charcoal representation in lake sediments.