Age Class Distribution Research Articles

Acute phase reactants and severity of homozygous sickle cell disease

Serum concentrations of seven acute-phase reactants: albumin, transferrin (Tf), alpha-1-antitrypsin (AIAT), caeruloplasmin (Cp), alpha 2-macroglobulin (alpha 2-MG), haptoglobin (hp) and C-reactive protein (CRP) were determined in 73 subjects with varying severities of homozygous sickle cell (HbSS) disease. Fifty healthy subjects of comparable sex, age and socio-economic class distributions as the HbSS subjects served as controls. Albumin and alpha 2-MG were comparable in all the subject groups. Tf and hp levels were significantly reduced in the HbSS groups relative to the control group. Conversely, AIAT, CRP and CP were significantly elevated. However only Tf and CRP manifested significant correlations with any of the indices of disease severity employed. Transferrin and CRP are suggested as plasma proteins worthy of further evaluation as indicators of severity in homozygous sickle cell disease.

Some mathematical programming approaches for optimizing timber age-class distributions to meet multispecies wildlife population objectives

We investigated three approaches for finding optimum allocations of forest age-classes to meet multispecies conservation objectives for a community of terrestrial vertebrate species. We illustrate our approaches using data on relative abundances of 92 species of amphibians, reptiles, birds, and mammals sampled from five habitat types (age-classes) of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) forests in northwestern California. Our three approaches involved maximizing (i) the expected number of viable species; (ii) the minimum probability of viability among all species; and (iii) the joint probability of viability across all species. Each approach was demonstrated using an assumption that viability is linearly related to abundance or that viability is logistically related to abundance. We discuss limitations of our approach focusing on assumptions of data quality, relative conservation priority among taxa, relationships between estimated abundance of a population and its probability of viability, interspecific interactions, and the need for evaluation of spatial distribution of habitats.

Classification of social behaviour patterns in feral domestic cats

Previous accounts of social behaviour of free-ranging domestic cats have grouped behaviour patterns using morphological or subjective similarities. In an initial attempt to devise a scheme based on underlying motivational links, an analysis was made of the components of 978 interactive sequences between cats in two neutered feral colonies. From the probabilities that each participant would perform any pair of patterns within a sequence, all frequently occurring patterns were grouped by average linkage cluster analysis. Despite differences between the colonies in the number of cats and their age or sex class distribution, a considerable degree of similarity in the groupings of behaviour patterns was evident. Clusters could be labelled as defensive ( 1 ), aggressive (2), avoidance (3,4), approach/ sit/allogroom ( 5 ), affiliative (6), and play ( 9 ). Two other clusters ( 7 and 8 ) appeared to be derived from the idiosyncratic behaviour of single individuals. Within each sequence, further structure could be determined from first-order Markov chain analysis of the patterns in the order in which they were performed by either partner. For example, within the affiliative patterns, the behaviour Rub Head was usually preceded by an approach with the tail raised; if both partners raised their tails, headrubbing (or forehead-rubbing) was mutual and simultaneous, and was also likely to be followed by mutual flank-rubbing. Friendliness in cats: implications for cats and catowners Sandra McCune Sub-Department of Animal Behaviour, University of Cambridge, Madingley, Cambridge CB3 8AA, UK

Root mechanical properties related to disturbed and stressed habitats in the Arctic.

Various mechanical and architectural properties of roots were measured on plants characteristic of different levels of soil disturbance associated with frost-heave cycles on sorted polygons in Swedish Lapland: one of these measures, resilience, has not, apparently, been recorded previously in literature. Some roots were sampled from species which occurred on both disturbed and stable soils. Root length, root angle, numbers of roots and root diameter varied greatly between species but the degree of branching of roots was generally low. Among all species, and particularly forbs and graminoids which are the most common life forms on polygons, there was a clear trend of decreasing root diameter with increasing soil disturbance, while the species growing on both disturbed and stable ground showed no clear trend associated with soil disturbance. The small root diameter of species growing on the polygons could result from the different species and life forms found there together with a younger age class distribution of plants, younger plants having smaller roots. Only one third of the species growing on the most disturbed soils had rhizomes, whereas twice as many species possessed rhizomes in areas of lower disturbance. The tensile strength, breaking strain (a measure of how much a root is deformed by stretching), breaking stress (a measure of root strength corrected for the cross-sectional area) and the resilience (a measure of the elastic-recovery of stretched roots) of the roots varied highly significantly among the species. The tensile strength varied 6.5-fold, the breaking strain varied by up to almost 8-fold and the breaking stress 13-fold. The modulus of resilience varied least, by a factor of only two. There was no clear trend in the way mechanical properties of the roots of the three species occurring on both stable and frost-heaved soils varied between the two regimes. However, among all species, those from the frost-heaved soils tended to have the weakest roots, because of their small diameter, but the strongest roots per cross-sectional area (i.e. they had the greatest breaking stress). Among life-forms, graminoids toler̀Gated a significantly greater strain than forbs and dwarf shrubs and much higher stress before they broke. Dwarf shrubs and forbs had significantly higher resilience than graminoids and the highest tensile strengths. Forbs showed the lowest values for all of the measured variables except for resilience, which fell between the values for graminoids and dwarf shrubs. There were no significant differences in any of the mechanical measures of root resistance among species of different frost-heaving regimes, indicating that there are few architectural or mechanical properties which enable roots to survive in the most disturbed soil. Indeed, the absence of a complete plant canopy and an increase in abundance of young plants on the polygon area compared with the stable areas suggest that if there are any adaptations to strong disturbance, they are less than adequate and the hypothesis that arctic plants avoid, rather than adapt, to severe environment is supported.

Age and Sex Composition of Live-Captured and Hunter-Killed Samples of Black Bears

We compared age-class distribution and sex ratios of captured and hunter-killed samples of black bears ( Ursus americanus ) to examine the relative agreement between methods used to monitor regional populations of this species. Mean ages of captured bears were greater than hunter-killed bears, and females were less abundant in the captured sample. Temporal differences between sampling methods (live capture = diurnal + nocturnal versus hunters = diurnal) may explain age-class differences. Variation in mobility (live capture = mainly stationary versus hunters = stationary + mobile) may explain sex ratio differences. Although we could not determine which sample was more representative of the population, our results suggest that biologists apply several indices as a more reliable approach to monitor the response of a population of bears to environmental change.

The temporal and spatial analysis of tree age distributions

The temporal and spatial patterns of tree establishment and stand disturbance history are often based on the interpretation of age-class frequency distributions. In particular, the presence of even-aged groups of trees is often used as compelling evidence of past disturbance. However, even-aged groups of trees may be indistinguishable in an age distribution if several different-aged patches occur, especially if their ages overlap. For two different types of forest we used spatial autocorrelation analysis to statistically test for the presence of even-aged patches in tree age data. Ordination and cluster analysis were subsequently applied to a matrix of association measures that reflected both spatial proximity and age similarity to identify even-aged groups of trees. Although the method worked well for our forests, which contained light-demanding tree species, it is likely to be less applicable to forests dominated by shade-tolerant species, because trees may be of many different ages if they were present as suppressed individuals prior to disturbance. However, in these instances the method could be usefully applied in other types of analysis, such as the distribution of growth release dates, tree-fall or fire-scar dates, and growth rates.

Winter Distribution of Age and Sex Classes in an Irruptive Migrant, the Evening Grosbeak (Coccothraustes vespertinus)

I used bird--banding data (1955-1988) and logistic regression analyses to test the prediction that male Evening Grosbeaks (Coccothraustes v. vespertinus) winter farther north than females, and to investigate whether age groups (first-winter vs. older) differ in their winter distribution. Males wintered farther north than females in 28 of 31 winters in eastern North America (<85°W), and in 12 of 31 winters in central regions. Males typically comprised 53-65% of individuals wintering at the northern edge of the winter range, and 18-27% in the south. No differences in distribution between age classes were observed. Differential migration of the sexes in this species is most likely related to social dominance behavior or to the ability of the larger-bodied males to tolerate harsh winter conditions in northern regions.

Trees in gardens: some notes

The great storms of 1953 in Scotland, 1962 in Yorkshire, and 1987 and 1990 in the south of England demonstrated the vulnerability of trees in gardens, and it is opportune to think carefully about the purposes for which the trees are there; the issues of shelter from wind, frost, and sun; the distribution of age classes, and the perpetuation of the range of species.

Effects of seasonally varying diet quality on collared peccary population dynamics — a simulation study

A model representing the effects of varying dietary crude protein (CP) levels on growth, survival, and reproductive success of collared peccaries is described, validated, and used to simulate population responses to selected environmental conditions. Behavior of the model on both individual and population levels is compared to available field data. At the individual level, predictions of body weight dynamics for juveniles and adults on varying CP diets compare favorably with similar data collected from captive animals. However, simulated individuals lose weight too rapidly when dietary CP remains at extremely low levels for extended periods of time. At the population level, predictions of herd size, herd structure (age-class distribution, sex ratio), seasonality of reproduction, and probability of survival exhibit trends generally similar to those observed among wild peccaries. Simulation of selected environmental conditions typical of south Texas, including a 12-month drought, and an 18-month wet period, suggests that changes in dietary CP can have a significant effect on population dynamics. Changes in juvenile survival rates are the most important factor influencing population responses to fluctuating nutritional conditions. The model relates variability in population recruitment to fluctuations in environmental conditions through the effect of diet quality on survival and reproductive performance of individuals. This approach to population modelling does not place the arbitrary density-dependent constraints on population dynamics that characterize many traditional population models. Rather, density-dependent population responses emerge as the result of ecological constraints on individuals.

Monitoring of sex and age ratios in ungulate populations of the Kruger National Park by ground survey

Objectives, techniques and problems of monitoring ungulate population structure and trends using standardised ground surveys as an adjunct to aerial counts are described and discussed in the light of experience gained over the past seven years. Because of ambiguities inherent in the interpretation of juvenile survival rates from data on age class distributions and until the accuracy and repeatability of the aerial counts in Kruger National Park have been assessed, a complementary approach to population monitoring using ground and aerial surveys is advocated.

Demography of agile gibbons (Hylobates agilis)

Demographic processes and the structure of a population of agile gibbons (Hylobates agilis) were investigated over 6 years in the Gunung Palung Reserve, Indonesia. Estimates of population size, density, and biomass revealed a population whose groups were stable in size and composition. Demographic processes place gibbons at risk, however, to short-term changes in their environment. Patterns of survival, fecundity, mortality, and dispersal combined to produce negative rates of growth. In addition, a top-heavy age-class distribution, with adults forming a large fraction of animals, makes it unlikely that this population could recover rapidly from a decline in numbers. Two behavioral factors, territoriality and monogamy, account for the size and stability of gibbon groups. Monogamy imposes limits on group size, while mating patterns and territoriality decrease the impact of sources of high mortality common in other primate species. These relationships underscore the fundamental importance of behavioral influence on demographic processes and social structure.

Age and Sex Differences in Winter Distribution of American Goldfinches in Eastern North America

Banding data for 1975-1985 were used to determine the latitudinal distribution of sex and age (males only) classes of the American Goldfinch Carduelis tristis during winter in eastern North America. Males wintered north of females, and among males, immatures wintered farther north than adults. Analysis of recovery data suggested that age and sex differences in winter distribution resulted from differences in distance migrated from the breeding grounds. The results are discussed in light of existing hypotheses proposed to explain differential migration. Geographic differences in the winter distribution of the sexes are qualitatively consistent with predictions of both the body size and social dominance hypotheses, but neither these, nor the arrival time hypothesis, can explain why male goldfinches make longer migrations from the breeding grounds as adults. We propose that young goldfinches may be physiologically or behaviorally incapable of making long migrations during

Forest mapping using satellite imagery. The Regensburg map sheet 1:200 000 as example

In research on forest mapping with data from the Landsat Thematic Mapper special attention has been given to work aimed at covering large sections of Bavaria on a scale of 1:200 000. The first 1:200 000 sheet processed was the Regensburg sheet. The classification was based on signature analysis of training areas. With that information, the stands were studied according to tree species, age class and mixture distribution. Multitemporal methods were applied to separate forest from nonforest areas. In addition to the main classes of deciduous, coniferous and mixed deciduous/coniferous, the separation of spruce and pine was included.

A comparison of the WAIS and WAIS‐R in matched UK samples

A matched samples design was employed to compare WAIS and WAIS-R IQ in UK subjects. The WAIS yielded significantly higher mean Full Scale, Verbal and Performance IQs. The mean differences were 7.5, 6.4 and 7.9 IQ points respectively. The WAIS and WAIS-R samples were broadly representative of the UK adult population in terms of age, sex and social class distribution, and therefore provide tentative estimates of population mean scores for both Wechsler scales. Mean WAIS IQ was 108.6, suggesting that the WAIS yields inflated IQ scores in the contemporary UK population. Encouragingly, mean WAIS-R Full Scale IQ was 101.1, suggesting that it neither markedly underestimates nor overestimates IQ in the UK.

A revision of coregonine fish distribution and abundance in eastern James-Hudson Bay

Recent sampling programs conducted in the estuaries of the Eastmain and La Grande rivers (James Bay) and the Great Whale, Little Whale, Innuksuac and Povungnituk rivers (Hudson Bay) revealed patterns of coregonine fish distribution that differ from previous observations. The relative abundance of cisco, Coregonus artedii, and lake whitefish, C. clupeaformis, varied among rivers but did not reveal a latitudinal cline. Previous sampling programs underestimated the abundance of cisco in the Little Whale River. In addition, cisco was the third most abundant species captured in the Povungnituk River, situated 200 km to the north of the previously proposed northern limit at Innuksuac River. As such, the low abundances of cisco in the Great Whale and Innuksuac rivers cannot be attributed to a physiological inability to cope with a reduced growing season. Immature cisco were almost totally absent from the estuaries of the Hudson Bay rivers following spring breakup whereas immature lake whitefish made up 100% of the catch in the Innuksuac River at the same time of year. Species-specific migration patterns in Hudson Bay that differ from those observed in James Bay and the existence of unique juvenile overwintering rivers are 2 hypotheses proposed to explain the discontinuous age-class distribution of cisco and lake whitefish observed in Hudson Bay.

Timber Availability in Northcentral Pennsylvania—The Next Hundred Years

Abstract Timber availability was forecast over a 100-year period for Pennsylvania's most valuable hardwood region using the USDA Forest Service FORPLAN model. The eight-county region was found to have a sawtimber production capability that could more than triple during the next 60 years. Age class distributions would also become more balanced, thereby tempering cyclical harvest patterns. North. J. Appl. For. 6:133-137, September 1989.

Temperature-Dependent Model for Predicting Emergence of Adult Southwestern Corn Borer (Lepidoptera: Pyralidae) in Texas

A temperature-dependent model designed to predict emergence of first-generation adult southwestern corn borer, Diatraea grandiosella Dyar, was developed and validated. Thermal unit requirements were determined for larval, prepupal, and pupal development for nondiapausing southwestern corn borer at three constant temperatures. Data input to the model were average daily mean maximum and minimum temperatures and the age class (instar) distribution of field-collected larvae. Model predictions agreed closely with observed adult emergence during 4 yr of field validation. Fifty to 69% of the predicted dates were within ±2 d of the observed emergence date for 5, 25, and 50% adult emergence. Application of the developmental model to an integrated pest management program for corn is discussed.

Equity, consistency, efficiency and new rules for discounting

The trade-offs required by long-term projects pose problems in maintaining intertemporal equity and efficiency. Neither historical trends nor consumption changes during individual life-cycles can make the discount factors of modified discounting consistent. Mortality should be reflected in age-class distributions, not discount rates, while pure time preference is irrelevant to normative discounting. Modified discounting offers a politically soft option, requiring present generations to make relatively little sacrifice to enhance future consumption. Equity effects of introducing modified or zero discounting may be positive or negative. A fixed year zero for modified discounting is inequitable, and a floating one gives inconsistent decisions.

Effect of scale and spatial heterogeneity on fire-interval distributions

The distribution of forest-fire intervals has been characterized by fitting statistical distributions, such as that of Weibull. The parameters of fitted distributions can then be used to compare fire regimes. Fire-interval distributions for the 187-year presettlement fire history record in the Boundary Waters Canoe Area, Minnesota, were analyzed using reconstructed "fire-year" maps. Distributions were determined for sampling units at five spatial scales, from about 25 000 to 400 000 ha. Fire-interval distributions varied from positively to negatively skewed, but for most units the Weibull distribution fit significantly. The distributions varied spatially, and cluster analysis suggested that three fire regions, each containing a relatively homogeneous fire regime, could be identified. The sources of this spatial variation are unknown. There was less variation between scales within a fire region than between fire regions. This contrasts with a previous finding, using the same fire-history data, that scale substantially affects observed landscape age-class distribution. This disparity arises because landscape age-class distributions may fluctuate even if fire-interval distributions do not fluctuate. Reconstruction of fire-interval distributions requires historical data; landscape age-class distributions at an instant in time are insufficient.

Microcanonical ensembles with non-equiprobable states. Part 2: Applications to empirical and theoretical distributions

Ensembles with non-equiprobable states—which have been studied in a previous work (Auger 1984)—are applied to various empirical and theoretical distributions. The equilibrium distributions are calculated by the Lagrange method. Firstly, we determine the state probabilities necessary to obtain empirical distributions, such as Pareto's iaw. Secondly, we calculate equilibrium distributions for an ethotogical example concerning activity frequencies of animals. We also study an ecological example in population dynamics concerning the age-class distribution of animals belonging to a given population. This method can be used either to explain empirical equilibrium distributions or to calculate theoretical equilibrium distributions from chosen graphs of transition states.