bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of relationship between simulated fish population responses and their life history traits: inadequate models, incorrect analysis, or site-specific factors?
Authors: Rose Kenneth A
Published: May 2005

Relationships between fish population responses to changes in their vital rates and commonly available life history traits would be a powerful screening tool to guide management about species vulnerability, to focus future data collection on species and life stages of concern, and to aid in designing effective habitat enhancements. As an extension of previous analyses by others, I analyzed the responses to changes in fecundity and yearling survival of age-structured matrix and individual-based population models of 17 populations comprising 10 species. Simulations of the matrix models showed that the magnitude of population responses, but not the relative order of species sensitivity, depended on the state (sustainable or undergoing excessive removals) of the population. Matrix and individual-based models predicted population responses that appeared to be unrelated to their species-level life history traits when responses were plotted on a three-end-point life history surface. Density-dependent adult growth was added to the lake trout (Salvelinus namaycush) matrix model, and simulations demonstrated the potential importance to predicted responses of density-dependent processes outside the usual spawnerrecruit relationship. Four reasons for the lack of relationship between population responses and life history traits related to inadequate population models, incorrect analysis, inappropriate life history model, and important site-specific factors are discussed.
Life history trade-offs and community dynamics of small fishes in a seasonally pulsed wetland
Authors: DeAngelis Donald L , Trexler Joel C , Loftus William F
Published: May 2005

We used a one-dimensional, spatially explicit model to simulate the community of small fishes in the freshwater wetlands of southern Florida, USA. The seasonality of rainfall in these wetlands causes annual fluctuations in the amount of flooded area. We modeled fish populations that differed from each other only in efficiency of resource utilization and dispersal ability. The simulations showed that these trade-offs, along with the spatial and temporal variability of the environment, allow coexistence of several species competing exploitatively for a common resource type. This mechanism, while sharing some characteristics with other mechanisms proposed for coexistence of competing species, is novel in detail. Simulated fish densities resembled patterns observed in Everglades empirical data. Cells with hydroperiods less than 6 months accumulated negligible fish biomass. One unique model result was that, when multiple species coexisted, it was possible for one of the coexisting species to have both lower local resource utilization efficiency and lower dispersal ability than one of the other species. This counterintuitive result is a consequence of stronger effects of other competitors on the superior species.
A comparison of methods for estimating activity costs of wild fish populations: more active fish observed to grow slower
Authors: Rennie Michael D , Collins Nicholas C , Shuter Brian J , Rajotte James W , Couture Patrice
Published: May 2005

Activity costs can account for a major proportion of fish energy budgets and may trade off against observed growth rates in wild fish populations. Recent approaches to estimating activity costs in situ have used a contaminantbioenergetic mass balance modelling approach, allowing for a broader examination of activity costs among populations compared with time-consuming alternative approaches. We report the results of this contaminantbioenergetic modelling approach to estimating in situ activity costs compared with two alternative independent methods of assessing in situ activity costs. Comparisons were made between a fast- and slow-growing yellow perch (Perca flavescens) population. Contaminantbioenergetic estimates of activity costs in the fast-growing population were 39% lower than those in the slow-growing population. Activity estimated from recorded swimming behaviours was 37% lower in the fast-growing population and 22%29% lower in the fast-growing population based on published relationships between activity costs and axial white muscle glycolytic enzyme capacities. Consumption rates were actually 32% lower in the fast-growing population, implying that lower activity costs more than compensated for lower food intake. The agreement among the three independent measures of activity costs strongly support the idea that activity costs, rather than food intake, are a major determinant of growth differences in these two wild fish populations.
Assessing changes in age and size at maturation in collapsing populations of Atlantic cod (Gadus morhua)
Authors: Olsen Esben Moland , Lilly George R , Heino Mikko , Morgan M Joanne , Brattey John , Dieckmann Ulf
Published: May 2005

By estimating probabilistic reaction norms for age and size at maturation, we show that maturation schedules of Atlantic cod (Gadus morhua) off Labrador and Newfoundland shifted toward earlier ages and smaller sizes during the late 1980s and early 1990s, when these populations underwent a severe collapse in biomass and subsequently were closed for directed commercial fishing. We also demonstrate that this trend towards maturation at younger ages and smaller sizes is halted and even shows signs of reversal during the closure of the fisheries. In addition, our analysis reveals that males tend to mature earlier and at a smaller size than females and that maturation age and size decrease with increasing latitude. Importantly, the maturation reaction norms presented here are robust to variation in survival and growth (through phenotypic plasticity) and are thus strongly indicative of rapid evolutionary changes in cod maturation as well as of spatial and sex-specific genetic variation. We therefore suggest that maturation reaction norms can provide helpful reference points for managing harvested populations with evolving life histories.
Life history and ecological correlates of extinction risk in European freshwater fishes
Authors: Reynolds John D , Webb Thomas J , Hawkins Lorraine A
Published: May 2005

We used phylogenetically based comparative analyses to test for associations between extinction risk in European freshwater fishes and a variety of life history, ecological, and biogeographical traits. Based on the World Conservation Union classification scheme, a total of 47% of Europe's 287 native species are classified as threatened with extinction. Threatened species are significantly smaller than less-threatened species in the same genera when analyses are restricted to fully freshwater species. This trend is reversed when anadromous genera are included. These comprise many large-bodied species in which fishing has often played a greater role in declines than in other taxa. Threatened species did not differ significantly in their habitats, although they tended to occupy a narrower variety of habitats biased toward streams and rivers. Threatened species occupy much narrower latitudinal ranges than close relatives that are less threatened, and they also have more southerly distributions where pressures on habitats are intense. This study suggests that links between life histories and threat status of freshwater fishes are not as clearcut as for marine species. For fish restricted entirely to freshwater, small-bodied species are most at risk owing to their naturally small ranges, which may put them in a more precarious position when their habitats are impacted by humans.
Introducing the symposium "Building on Beverton's legacy: life history variation and fisheries management"
Authors: Shuter Brian J , Abrams Peter A
Published: May 2005

Throughout his career, Ray Beverton displayed an interest in the life history diversity in marine and freshwater fish. The papers collected here describe recent research directed at documenting this diversity and understanding both its consequences and the processes that generate it. There are three themes: factors that direct life history dynamics; fishing as a force that redirects life history dynamics; and roles for life history statics in conservation management. The "dynamics" papers show that fish life histories can evolve in response to both natural and harvest-induced selective pressures. Evolution in response to harvesting can be rapid, with potentially dramatic effects on population dynamics and sustainable exploitation. The "statics" articles demonstrate how maturity traits combine with shifts in habitat use to shape the sensitivity of a population to habitat loss. Life history shifts can dramatically alter the safety of harvesting policies that were prudent in the past; shifts of the predators or prey of a harvested species can be as important as shifts in the harvested species itself. Further work on the ecological circumstances that favour different degrees of plastic or genetic life history responses to human impacts are needed to prevent inadvertent induction of long-lasing evolutionary changes in fish life histories.
Optimal life histories and food web position: linkages among somatic growth, reproductive investment, and mortality
Authors: Shuter B J , Lester N P , LaRose J , Purchase C F , Vascotto K , Morgan G , Collins N C , Abrams P A
Published: May 2005

Life history variation among 60 Ontario populations of lake trout (Salvelinus namaycush), walleye (Sander vitreus), cisco (Coregonus artedii), and yellow perch (Perca flavescens) is presented and interpreted using a biphasic model of individual growth that specifically accounts for the significant shift in energy allocation that accompanies sexual maturity. We show that the constraints imposed on life history variation by the character of the biphasic growth model are such that optimal life histories will exhibit associations among growth parameters, reproductive investment, and mortality that are largely consistent with associations evident in both our data set and earlier empirical studies; the von Bertalanffy growth parameter k varies with reproductive investment, and both k and investment vary with adult mortality. Our analysis suggests that within a food web, life history parameters will shift in a predictable fashion with the decreases in mortality expected as one moves from primary consumers up toward top predators. This expectation is supported by the differences in life history parameters that we observe between the two top predators in our data set (lake trout and walleye) and the two mid-trophic level consumers (cisco and yellow perch).
Can commercial fishing cause evolution? Answers from guppies (Poecilia reticulata)
Authors: Reznick David N , Ghalambor Cameron K
Published: May 2005

Life history theory predicts that high adult mortality rates select for earlier maturity and increased reproduction. If such evolution occurs in response to the commercial exploitation of natural fish populations, then the correlated reduction in body size would reduce the yield of the fishery. Earlier maturity and reduced body size are seen in commercially exploited populations. Here, we compare the life histories of natural populations of guppies (Poecilia reticulata) from Trinidad that live in either high- or low-predation environments, which serve as surrogates for the presence or absence of commercial fishing. We can quantify mortality rate and life history variables, including age and size at maturity, in the laboratory and in nature. We have manipulated mortality rates in nature and measured the rate of evolution. High mortality selects for earlier maturity at a smaller size, as observed in commercial fisheries and as predicted by theory. Furthermore, the nature and magnitude of predator-induced mortality are comparable to those caused by commercial fishing. The rate of evolution in guppies predicts similar evolution in commercial fisheries on a time scale of decades. These attributes support arguments that humans, like predators, have acted as an agent of selection when exploiting populations of fish.
Effective fire suppression in boreal forests
Authors: Cumming S G
Published: May 2005

Fire suppression is (functionally) effective insofar as it reduces area burned. In North American boreal forests, fire regimes and historical records are such that this effect cannot be detected or estimated directly. I present an indirect approach, proceeding from the practice of initial attack (IA), which is intended to limit the proportion of "large" fires. I analysed IA's (operational) effectiveness by a controlled retrospective study of fire-history data for an approximately 86 000 km2 region of boreal forest in northeastern Alberta, Canada, from 1968 to 1998 (31 years). Over this interval, various improvements to IA practice, including a 1983 change in management strategy, created a natural experiment. I tested the results with multiple logistic regression models of the annual probabilities of a fire becoming larger than 3 and 200 ha. Annual fire counts (Nt) were a surrogate for fire weather and peak daily counts within years (arrival load). Measured by odds ratios, mean IA effectiveness against 3- and 200-ha fires increased in 1983 by factors of 2.02 (95% CI = 1.702.40) and 2.41 (95% CI = 1.693.45), respectively. Prior to 1983, the functional response to Nt was consistent with saturation of IA capacity at high arrival loads. From 19831998, effectiveness was independent of Nt. I introduce the proportional reduction in area burned (impact) as a measure of functional effectiveness and state conditions under which it can be estimated from the regression models. Over 19831998, if suppressed and actual fires were comparable, relative IA impact ([Formula: see text]) was 0.58 (95% CI = 0.340.74) and area burned was reduced by 457 500 ha. If fires larger than 1 × 105, 1 × 104, or 1 × 103 ha are assumed to be unpreventable, [Formula: see text] declines to 0.46, 025, or 0.08, respectively, but there is no evidence this is the case.
Prescribed fire effects on the herbaceous layer of mixed-oak forests
Authors: Hutchinson Todd F , Boerner Ralph EJ , Sutherland Steve , Sutherland Elaine Kennedy , Ortt Marilyn , Iverson Louis R
Published: May 2005

In 1994, a multidisciplinary project was established to study the effects of prescribed fire on oak forests in southern Ohio. Here we describe the herbaceous layer response to fires over a 5-year period. In four study sites, treatments imposed were unburned, periodic (1996 and 1999), and annual (19961999) fires. Sample plots (n = 108) were stratified by an integrated moisture index. Species' frequencies were recorded annually, and a total of 452 species (97% native) were documented. Though species composition was significantly affected by fire, the effects were shown by ordination to be small in magnitude relative to overall compositional variation. Burned areas developed greater small-scale species richness as grasses, summer forbs, and seed-banking species increased in frequency; however, these changes were also not large in magnitude. Though a few species increased substantially via germination after fire, most common species exhibited frequency increases or decreases of <10% on burned units. Fire effects on vegetation were largely similar between annual and periodic burns and also among integrated moisture index classes. Direct fire effects on vegetation were limited by the dormant-season timing of burns and the resprouting of woody plants. Indirect effects were limited, as fires caused relatively minor changes in forest structure and resource availability in these long-unburned forests.
Assessing surface area of coarse woody debris with line intersect and perpendicular distance sampling
Authors: Williams M S , Ducey M J , Gove J H
Published: May 2005

Coarse woody debris (CWD) plays an important role in many terrestrial and aquatic ecosystem processes. In recent years, a number of new methods have been proposed to sample CWD. Of these methods, perpendicular distance sampling (PDS) is one of the most efficient methods for estimating CWD volume in terms of both estimator variance and field effort. This study extends the results for PDS to the estimation of the surface area of CWD. The PDS estimator is also compared to two line intersect sampling (LIS) estimators, where one of the LIS estimators requires the measurement of surface area on each log and the other estimates surface area using a single measurement of log circumference at the point of intersection between the log and the line. The first estimator approximates the true surface area by assuming either a conic or parabolic stem form and requires measurements of the end diameters of each log, which is more time consuming than a single measurement. The performance of the three estimators was compared using a computer simulation. The results of the simulation indicate that, given the same number of pieces of CWD sampled at each point, equal variances can be achieved with PDS using sample sizes that range from about 10% to in excess of 100% the size of a comparable LIS estimator. When the LIS estimators were compared, the estimator that required the measurement of surface area was only about 3%6% more efficient than the alternative estimator, but the bias associated with assuming a conic or parabolic stem form ranged from roughly 5% to 15%. We conclude that PDS will generally outperform either of the LIS estimators. Another important conclusion is that the LIS estimator based on a measured surface area is likely to have a higher mean squared error than an LIS estimator that employs a single measurement of circumference. Thus, LIS sampling strategies that require the least amount of field work will often have the smallest mean square error.
Linking surface-fire behavior, stem heating, and tissue necrosis
Authors: Bova A S , Dickinson M B
Published: May 2005

Data from 69 experimental, small-plot fires are used to describe relationships among fire intensity, bark-surface heat flux, and depth of necrosis in stem tissue for red maple (Acer rubrum L.) and chestnut oak (Quercus prinus L.). A tetrazolium staining technique was used to determine the depth of necrosis in tree boles subjected to fires with intensities of 20 to 2000 kW/m. Over a range of bark moistures (28%83%) and bole diameters (320 cm), depth of necrosis appears to be primarily a function of fire intensity, flame residence time at the stem, and the corresponding time-integrated heat flux at the bark surface. Our results, along with known relations between bole diameter and bark thickness, and improved models of fire behavior and heat transfer, may be useful for estimating tree mortality resulting from prescribed fires.
Conifer growth, Armillaria ostoyae root disease, and plant diversity responses to broadleaf competition reduction in mixed forests of southern interior British Columbia
Authors: Simard Suzanne W , Hagerman Shannon M , Sachs Donald L , Heineman Jean L , Mather W Jean
Published: May 2005

Broadleaf trees are routinely removed from conifer plantations during vegetation management treatments, but whether the removal increases tree productivity or affects root disease and plant diversity is unknown. The effects of manual and chemical reduction of paper birch (Betula papyrifera Marsh.) and trembling aspen (Populus tremuloides Michx.) on conifer survival, growth, root disease incidence, and plant community diversity were investigated for 5 years in Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) plantations in southern interior British Columbia. Broadleaves were reduced by manual, girdling, and cut-stump glyphosate treatments for 5 years but most severely following cut-stump glyphosate and with a delay due to slow death following girdling. Conifer survival was reduced for 35 years following manual cutting or girdling of birch because of a 1.5- to 4-fold increase in mortality due to Armillaria ostoyae (Romagn.) Herink, but this did not occur following cut-stump glyphosate treatment of birch or manual cutting of aspen. Conifer diameter increased with treatment intensity and productivity of the vegetation complex. Competition thresholds were identified for diameter but not survival, although Armillaria-caused mortality tended to increase near the minimum growth threshold. Structural diversity increased following manual cutting and cut-stump glyphosate because birch dominants were removed and understory layers increased, but species richness and diversity were unaffected. Forest managers can expect increased conifer growth with birch removal but also small increases in mortality due to Armillaria ostoyae root disease following manual treatments and loss of large birch trees in all treatments.
Soil retention, tree uptake, and tree resorption of15NH4NO3and NH415NO3applied to trembling and hybrid aspens at planting
Authors: Choi Woo-Jung , Chang Scott X , Hao Xiying
Published: May 2005

Many experiments conducted under controlled environmental conditions suggest that deciduous tree species are adapted to NO3rather than NH4+uptake. To test this under field conditions, we studied soil retention, tree uptake, and tree resorption of15N derived from either15NH4NO3or NH415NO3applied to trembling aspen (Populus tremuloides Michx.) and hybrid aspen (Populus tremula L. × P. tremuloides) at planting. Overall, the hybrid had greater dry-matter yield and took up more total N than the trembling aspen over two growing seasons after fertilization. The recovery of15N per tree was also higher for the hybrid aspen than for the trembling aspen. Trembling aspen showed higher resorption efficiency of foliage N before abscission than hybrid aspen; however, the total amount of N retranslocated before leaf senescence was the reverse because of higher foliar dry-matter yield of hybrid aspen. The higher recovery of15NH4+than15NO3by trees seemed to be governed by higher N retention potential of NH4+than NO3in the soil. These results suggest that fertilization strategies need to be made based on both N acquisition capability of species and site-related factors, such as soil pH and immobilizationmineralization potential.
Predicting the mortality of Pinus sylvestris attacked by Gremmeniella abietina and occurrence of Tomicus piniperda colonization
Authors: Sikström Ulf , Jansson Gunnar , Weslien Jan
Published: May 2005

The fungus Gremmeniella abietina (Lagerb.) Morelet is widely distributed in the northern hemisphere and causes scleroderris canker in several coniferous species. In Sweden, large areas, mainly with 30- to 40-year-old Scots pine (Pinus sylvestris L.) forests, were attacked by the fungus in 2000. The main aim of this study was to investigate the relationship between tree crown transparency (CT) induced by G. abietina and P. sylvestris tree mortality. Furthermore, regenerationcolonization by Tomicus piniperda (L.) was monitored in the investigated stands. Thirty-five permanent sample plots were established in five P. sylvestris stands (3846 years old) infected by G. abietina and located in the central part of Sweden. During the 2 years following the attack, the total tree mortality accounted for 380 trees·ha1 and 6.2 m2·ha1 on average in the five stands, corresponding to 35% of the trees and 27% of the basal area at the time of the attack. Galleries with broods of T. piniperda occurred in trees with a CT value higher than 97%. A model was derived for predicting the probability of P. sylvestris tree mortality. The mortality of individual trees was found to be related to CT, position of needle loss within the crown (CTPOS), and tree diameter at breast height. Furthermore, there was an interaction between CT and CTPOS and a tendency for CT and site to interact. For a P. sylvestris tree with a 0.16-m diameter at breast height and a CT value of 90% spread throughout the crown, the model indicated a mortality probability of 0.03. Above this CT value, the probability of mortality increased substantially. For coniferous species, irrespective of the cause of damage, a CT value of 90%95% appears to be a critical range; any values greater than this indicate a high probability of mortality.
Solving the adjacency problem with stand-centred constraints
Authors: Gunn Eldon A , Richards Evelyn W
Published: May 2005

We present a new linear integer programming formulation of adjacency constraints for the area restriction model. These constraints are small in number and are a strong model for the adjacency problem. We describe constraint development, including strengthening and lifting, to improve the basic formulation. The model does not prohibit all adjacency violations, but computations show they are few in number. Using example forests ranging from 750 to more than 6000 polygons, optimization problems were solved and good solutions obtained in very short computational time.
Fine-scale selection by marten during winter in a young deciduous forest
Authors: Porter Aswea Dawn , St Clair Colleen Cassady , Vries Andrew de
Published: May 2005

American marten (Martes americana (Turton, 1806)) are often associated with old-growth forests, but have been detected living in a young deciduous forest in northern British Columbia, where a previous coarse-scale analysis failed to detect significant habitat selection. To address this paradox, we examined fine-scale habitat selection for specific activities. We used radiotelemetry and snowtracking to identify sites that appeared to have been used for resting, foraging, scent marking, and traveling during the winters of 19981999 and 19992000. Then we conducted vegetation surveys at these activity sites and at nearby random locations and used logistic regression to measure selection. Based on the number of significant variables and model fit, we detected more selectivity by marten for resting than for foraging and scent-marking sites, and no selectivity for traveling. Marten exhibited selection for several habitat structures that are characteristic of older forests (e.g., rootballs and wide-diameter snags), but that can be retained in some manipulated forests. With the exception of wide-diameter snags (selected at both resting sites and scent marks), marten selected different habitat structures for each type of activity. These results may help to explain why marten are able to survive in this and other sites that provide seemingly unsuitable habitat.
Heterogeneity in soil nitrogen within first-order forested catchments at the Turkey Lakes Watershed
Authors: Foster Neil , Spoelstra John , Hazlett Paul , Schiff Sherry , Beall Frederick , Creed Irena , David Clive
Published: May 2005

Topographic positional regulation of nitrogen (N) dynamics in soil within Canadian Shield headwaters, located in calibrated catchments containing mature, tolerant hardwood forest, was examined to determine how N pools, mineralization, nitrification, and leaching in soil relate to N export in drainage waters. A uniformly high net N mineralization and nitrification potential for surficial soil layers rich in organic N was demonstrated for ridge, upper-middle slope, and lower slope  footslope topographic positions. Results from plot-scale studies revealed that NO3 concentrations in soil water from well-drained soils were very highly variable throughout the catchments, ranging from 25 to 175 µmol·L1, with a median of 80 µmol·L1. The isotopic effects of denitrification were not detected in soil water collected from lower slope  footslopes, and in situ rates of N2O production from soils on lower slope  footslopes and valley bottoms were very low and highly variable. Higher N exports from soils than from streams were not explained by differences in soil water N with topographic position or denitrification in lower landscape topographic positions. Using an average soil water N value, based on the replicated plots within catchments, did not reduce the calculated substantial differences in N export between soils and streams.
The benefits of seed banking for red maple (Acer rubrum): maximizing seedling recruitment
Authors: Lambers Janneke Hille Ris , Clark James S
Published: May 2005

Seed banking is assumed to be unimportant for temperate trees, because their seeds are short-lived in soils. However, even short-term seed banking could increase recruitment and affect population dynamics of seed-banking trees. To investigate this possibility, we examined early life-history stages of red maple (Acer rubrum L.), an abundant seed-banking tree in eastern forests. We found that seed banking benefits red maple by increasing germination when seedling survival is likely. Most red maple seeds germinate soon after spring dispersal, when seedling survival is high, or postpone germination to the following growing season, once seedling survival becomes less likely late in the summer. This occurs because seed dormancy increases during the growing season, matching a concurrent decrease in seedling survival. Our results and those of other studies suggest seed dormancy is increased by the same environmental factors (low light and low moisture) that also decrease seedling survival. We speculate that early life-history traits, including seed banking, may have contributed to this species' increased abundance in eastern deciduous forests in the last century.
Early rooting of dormant hardwood cuttings ofPopulus: analysis of quantitative genetics and genotype × environment interactions
Authors: Zalesny, Jr. Ronald S , Riemenschneider Don E , Hall Richard B
Published: May 2005

Rooting of hardwood cuttings is under strong genetic control, although genotype × environment interactions affect selection of promising genotypes. Our objectives were (1) to assess the variation in rooting ability among 21 Populus clones and (2) to examine genotype × environment interactions to refine clonal recommendations. The clones belonged to five genomic groups ((Populus trichocarpa Torr. & Gray × Populus deltoides Bartr. ex Marsh.) × P. deltoides 'BC'; P. deltoides 'D'; P. deltoides × Populus maximowiczii A. Henry 'DM'; P. deltoides × Populus nigra L. 'DN'; and P. nigra × P. maximowiczii 'NM'). Cuttings, 20 cm long, were planted in Iowa and Minnesota in randomized complete blocks at 1.2 m × 2.4 m spacing, across three planting dates during 2001 and 2002. We measured nine belowground and aboveground traits from harvested cuttings after 14 days of growth. Percent rooting ranged from 22% to 86%. Broad-sense heritability for root and top dry mass ranged from 0.09 to 0.11 and 0.31 to 0.38, respectively. There were genotype × environment interactions for most traits, with belowground growing degree-days accounting for >54% of environmental variation. Clonal rooting was stable, except at Westport, Minnesota, during 2002, when root growth was relatively poor.
Dendroecological reconstructions of forest disturbance history using time-series analysis with intervention detection
Authors: Druckenbrod Daniel L
Published: May 2005

The detection of release events in the annual growth increments of trees has become a central and widely applied method for reconstructing the disturbance history of forests. While numerous approaches have been developed for identifying release events, the preponderance of these methods relies on running means that compare the percent change in growth rates. These methods do not explicitly account for the autocorrelation present within tree-ring width measurements and may introduce spurious events. This paper utilizes autoregressive integrated moving-average (ARIMA) processes to model tree-ring time series and incorporates intervention detection to identify pulse and step outliers as well as changes in trends indicative of a deterministic exogenous influence on past growth. This approach is evaluated by applying it to three chronologies from the Forest Responses to Anthropogenic Stress (FORAST) project that were impacted by prior disturbance events. The examples include a hemlock (Tsuga canadensis (L.) Carrière) chronology from New Hampshire, a white pine (Pinus strobus L.) chronology from Pennsylvania, and an American beech (Fagus grandifolia Ehrh.) chronology from Virginia. All three chronologies exhibit a clustering of step, pulse, and trend interventions subsequent to a known or likely disturbance event. Time-series analysis offers an alternative approach for identifying prior forest disturbances via tree rings based on statistical methods applicable across species and disturbance regimes.
Spatial and population characteristics of dwarf mistletoe infected trees in an old-growth Douglas-fir  western hemlock forest
Authors: Shaw David C , Chen Jiquan , Freeman Elizabeth A , Braun David M
Published: May 2005

We investigated the distribution and severity of trees infected with western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones subsp. tsugense) in an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)  western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest. With the use of Hawksworth six-class dwarf mistletoe rating system, infection status was assessed for 3516 hemlock and true firs ≥5 cm diameter on a 12-ha stem-mapped plot located in the Cascade Mountains of southwest Washington State. Within the plot, 33% of the area had some level of infection and 25% (719) of western hemlocks, 2.2% (12) of Pacific silver fir (Abies amabilis (Dougl.) Forbes), and 29% (2) of noble fir (Abies procera Rehd.) trees were infected. Infected trees are larger than uninfected trees, on average, and within the infected tree population, the severely infected trees averaged larger than lightly infected trees. Abundant dwarf mistletoe in larger trees definitely positions the dwarf mistletoe population for future spread. Ripley's K analysis indicates a negative association between infected and uninfected hemlock trees, confirming that the infected trees form distinct dwarf mistletoe infection centers. The infection centers are actively spreading at their margins, which was confirmed by nearest neighbor analysis. Heavily infected trees had a negative association with uninfected trees, while lightly infected trees had a positive association with uninfected trees.
Additional results for perpendicular distance sampling
Authors: Williams M S , Valentine H T , Gove J H , Ducey M J
Published: May 2005

Over the last decade a number of new methods have been proposed to sample coarse woody debris. Of the new methods, both field trials and computer simulations suggest that perpendicular distance sampling is often the most efficient method for estimating the volume and surface area of coarse woody debris. As with any new sampling technique, further research and field testing are required to address some of the practical problems associated with the implementation of perpendicular distance sampling. This paper provides further results associated with the sampling of curved and multistemmed logs and field techniques for both slope correction and the measurement of elevated logs.
Seedling recruitment in a northern temperate forest: the relative importance of supply and establishment limitation
Authors: Caspersen John P , Saprunoff Megan
Published: May 2005

We quantified supply and establishment limitation as components of seedling recruitment for five species common to the temperate forests of central Ontario. Establishment limitation was the primary cause of recruitment failure for the three most common species: Acer saccharum Marsh., Betula alleghaniensis Britt., and Tsuga canadensis (L.) Carrière. The main barrier to establishment (including germination and seedling emergence) was a lack of suitable substrates, rather than a lack of light. Supply limitation, on the other hand, was the primary cause of recruitment failure for two less common species, Abies balsamea (L.) Mill. and Fagus grandifolia Ehrh. The cause of supply limitation was a lack of parent trees, in the case of A. balsamea, and low fecundity, in the case of F. grandifolia. Our results suggest that niche differences (i.e., germination requirements) are more important than dispersal in structuring temperate forest communities. Our results also suggest that availability of suitable substrates is the primary factor limiting seedling recruitment following logging.
Effects of conifer basal area on understory herb presence, abundance, and flowering in a second-growth Douglas-fir forest
Authors: Lindh Briana C
Published: May 2005

Although overstory trees exert competitive effects on understory plants, it is not clear how this competition affects the distribution and performance of herb species. This study seeks to clarify the relationship between understory herb performance and overstory basal area in second-growth Pseudotsuga menziesii (Mirb.) Franco stands. Data on 11 understory herb species were collected in a 100-ha watershed. Statistical models were constructed to control for the effects of slope, aspect, soil type, and distance from the central stream or peripheral ridge lines. Presence of old-growth associated and forest generalist herbs was positively associated with conifer basal area, as well as with north-facing aspects and proximity to the stream channel. Presence of release herbs, subordinate forest species that respond positively to canopy disturbance, was largely independent of measured variables. Abundance of individual species showed weak and inconsistent relationships with conifer basal area. In contrast, flowering of almost all species was negatively related to conifer basal area. Regression tree models suggested that conifer basal area may have stronger negative effects farther from the moist environments along stream channels. I conclude that patterns of presence of slow-growing forest species may be determined primarily by past events, while flowering better reflects current stand conditions.
Assessment of genetic diversity inTectona grandisusing amplified fragment length polymorphism markers
Authors: Shrestha Madan K , Volkaert Hugo , Straeten Dominique Van Der
Published: May 2005

There is much concern over teak (Tectona grandis L. f.) genetic resources because of uncontrolled logging during the past centuries. We investigated patterns of genetic variation within and among nine populations of T. grandis from diverse geographical regions in India, Thailand, and Indonesia using amplified fragment length polymorphism (AFLP). An analysis of molecular variance (AMOVA) showed that 57% of total genetic variance occurred within populations, the remaining 43% occurred between populations. Cluster analysis and principal coordinate analysis indicated that Indian populations are clearly separated from those in Thailand and Indonesia. However, the Berbera population from Orissa near the Indian northeastern coast is an exception, as it seems to have associations with both the Indian and the ThaiIndonesian populations. The Thai and Indian populations cannot mutually be separated in this investigation. The comparisons between Indian populations suggest that the northwestern Allapally plains population (Maharastra) is distinct from the two southern Indian populations that were analyzed.
Oral administration of sodium tungstate improves cardiac performance in streptozotocin-induced diabetic rats
Authors: Nagareddy Prabhakara Reddy , Vasudevan Harish , McNeill John H
Published: May 2005

Normalization of hyperglycemia and hyperlipidemia is an important objective in preventing diabetes-induced cardiac dysfunction. Our study investigated the effects of sodium tungstate on cardiac performance in streptozotocin-induced (STZ) diabetic rats based on its potential antidiabetic and antioxidant activity. Male Wistar rats were made STZ-diabetic and then treated with tungstate in their drinking water for 9 weeks. Body mass, food and fluid intake, plasma glucose, insulin, triglyceride, and free fatty acids levels were measured. At the termination of the study period, an oral glucose tolerance test (OGTT) was performed, and cardiac performance was evaluated using an isolated working heart apparatus. Tungstate-treated STZ-diabetic rats showed a significant reduction in fluid and food intake, plasma glucose, triglycerides, and free fatty acid levels, and improved tolerance to glucose in OGTT, owing to tungstate-mediated enhancement of insulin activity rather than increased insulin levels. Left ventricular pressure development, the rate of contraction (+dP/dT), and the rate of relaxation (-dP/dT) were significantly improved in tungstate-treated diabetic rats. Apart from a decreased rate of body mass gain, no other signs of toxicity or hypoglycemic episodes were observed in tungstate-treated rats. This study extends previous observations on the antidiabetic activities of tungstate, and also reports for the first time the salutary effects in preventing diabetic cardiomyopathy.Key words: diabetes, cardiomyopathy, tungstate, isolated working heart, oral glucose tolerance test.
Reduction of oxidative stress and atherosclerosis in hyperlipidemic rabbits byDioscorearhizome
Authors: Chang Weng-Cheng , Yu Ya-Mei , Wu Chieh-Hsi , Tseng Yueh-He , Wu Kuen-Yuh
Published: May 2005

Hyperlipidemia may induce oxidative stress, which is important in the pathogenesis of atherosclerosis. Dioscorea rhizome (DR) is the powdered form of yams, and possesses antioxidant and hypolipidemic function. We therefore investigated the antioxidative and antiatherogenic effects of DR on hyperlipidemic rabbits. The control group was fed chow containing 0.5% cholesterol and 10% corn oil. The probucol and DR groups were fed the same diet as the control group but with the addition of 100 mg probucol/kg chow and 200 mg DR/kg chow, respectively. Total cholesterol and triacylglycerol plasma levels, RBC hemolysis T50, lucigenin chemiluminescence, and luminol chemiluminescence increased in the control group compared with the normal group, and decreased in the probucol and DR groups compared with the control group. The activity of antioxidant enzymes superoxide dismutase and catalase was significantly higher in the probucol and DR group than in the control group. The level of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in liver DNA was lower in the probucol and DR group than in the control group. Eighty percent of the intimal surface of the thoracic aorta was covered with atherosclerotic lesions in the control group but only 40% of the surface was covered in the DR group. These results suggest that supplementation with DR reduces oxidative stress and attenuates atherosclerosis in hyperlipidemic rabbits.Key words: Dioscorea rhizome, plasma lipid, RBC hemolysis, chemiluminescence, antioxidant enzymes, 8-OhdG, atherosclerotic lesion.
THE SZNAJD CONSENSUS MODEL WITH CONTINUOUS OPINIONS
Authors: FORTUNATO SANTO
Published: May 2005

In the consensus model of Sznajd, opinions are integers and a randomly chosen pair of neighboring agents with the same opinion forces all their neighbors to share that opinion. We propose a simple extension of the model to continuous opinions, based on the criterion of bounded confidence which is at the basis of other popular consensus models. Here, the opinion s is a real number between 0 and 1, and a parameter ∊ is introduced such that two agents are compatible if their opinions differ from each other by less than ∊. If two neighboring agents are compatible, they take the mean sm of their opinions and try to impose this value to their neighbors. We find that if all neighbors take the average opinion sm, the system reaches complete consensus for any value of the confidence bound ∊. We propose as well a weaker prescription for the dynamics and discuss the corresponding results.
FISHER SCALING IN TWO-DIMENSIONAL ISING MAGNETIC LATTICE-GAS
Authors: FERREIRA A. L. , PRODANESCU E. L.
Published: May 2005

The critical properties of two-dimensional Ising magnetic lattice-gas model are studied by Monte-Carlo simulation in the canonical ensemble. The results are analyzed considering the modified Fisher scaling for systems with zero specific heat exponent, which applies when there are constrained variables such as the density in the canonical ensemble. The estimates of the exponents are obtained and compared to the exponents of the Ising universality class to which the model is expected to belong.
LATTICE BOLTZMANN SIMULATIONS OF DROP–DROP INTERACTIONS IN TWO-PHASE FLOWS
Authors: PREMNATH KANNAN N. , ABRAHAM JOHN
Published: May 2005

In this paper, three-dimensional computations of drop–drop interactions using the lattice Boltzmann method (LBM) are reported. The LBM multiphase flow model employed is evaluated for single drop problems and binary drop interactions. These include the verification of Laplace–Young relation for static drops, drop oscillations, and drop deformation and breakup in simple shear flow. The results are compared with experimental data, analytical solutions and numerical solutions based on other computational methods, as applicable. Satisfactory agreement is shown. Initial studies of drop–drop interactions involving the head-on collisions of drops in quiescent medium and off-center collision of drops in the presence of ambient shear flow are considered. As expected, coalescence outcome is observed for the range of parameters studied.
CALCULATION OF THE CROSSING TIME THROUGH THE FITNESS BARRIER IN A SYMMETRIC MULTIPLICATIVE LANDSCAPE
Authors: KIM DOKYOON , GILL WONPYONG
Published: May 2005

The crossing time through fitness barrier in a symmetric multiplicative landscape is systematically calculated for various mutation rates, fitness parameters, and sequence lengths by using a computer simulation. It is found that the crossing time scales as a power law in the mutation rate and the fitness parameter. It is also found that the crossing time increases exponentially as the sequence length increases. We have obtained the approximate formula, which decribes the asymptotic behavior of the crossing time in the long-crossing-time region, and the improved approximate formula with the correction factor, which nicely fit computer simulation results even below the long-crossing-time region. From the comparison between the approximate formula in the multiplicative landscape and the approximate formula in the sharply-peaked landscape, it is found that both landscapes have the same scaling effect of fitness parameter and mutation rate on the crossing time in the long-crossing-time region.
A PLATFORM FOR DEVELOPING NEW LATTICE BOLTZMANN MODELS
Authors: ZHENG H. W. , SHU C. , CHEW Y. T. , QIU J.
Published: May 2005

This paper presents a platform to develop new lattice Boltzmann models. It gives a general framework for different applications. It also presents basic velocity models and a set of basic conditions to construct new models which can recover Navier–Stokes equations. Besides, the equilibrium function can be easily obtained through a set of equations. By using the platform, we can easily recover the existing models. Some new models are derived from the platform and validated by their application to simulate the two-dimensional driven cavity flow. The obtained numerical results agree very well with available data in the literature.
STRUCTURE AND DYNAMICAL PROPERTIES OF AuN, N = 12–14 CLUSTERS: MOLECULAR DYNAMICS SIMULATION
Authors: YILDIRIM ERDEM K. , ATİŞ MURAT , GÜVENÇ ZİYA B.
Published: May 2005

Using molecular dynamics and thermal quenching methods on the basis of Voter–Chen version of the embedded-atom method, we have studied the melting behavior of Au N (N = 12, 13, 14) clusters. This behavior is described in terms of overall and atom resolved root-mean-square bond-length fluctuations, specific-heat, short- and long-time average coordination numbers of each atom and short-time average temperatures of the clusters. The isomer sampling probabilities are obtained from the thermal quenching of the molten clusters, and their energy-spectrum widths are investigated. Phase change of a cluster takes place with the collective and simultaneous motion of all the atoms.