Papyrus swamp development in the Upemba Basin, Zaïre: studies of population structure in Cyperus papyrus stands

The ecology and distribution of papyrus swamps are briefly reviewed together with the ecology, distribution structure and growth characteristics of Cyperus papyrus.
Three age-classes of culm are recognized and girth and density of each are recorded along transects through mree swamps in the Upemba Basin of Zaïre. A regression of culm-unit biomass on culm girth, developed for Ugandan swamps, is used to convert Upemba measurements into biomasses. It is shown that simple measurements, taken at only a single point in time, yield much information on both the structure and the dynamics of papyrus populations.
It is suggested that the standing-crops of such populations are determined by available light, and by local temperature regimes, and are therefore constant, irrespective of site quality (nutrient status), for any particular climatic zone. Culm-duration (life-time) is not significantly influenced by climate and the ratio culms/rhizomes provides a useful indicator of comparative productivity. Unlike community biomass, productivity can be limited by site quality.     

The demography of Howler Monkeys (Alouatta palliata) on Barro Colorado Island,Panamá

Chronological ages of Alouattaon Barro Colorado Island (BCI) were estimated from longitudinal dental wear. Combining these data with visual censuses, we approximated the study population’s age profile. A stable model was then constructed; from it we derived agespecific mortality rates. Mortality of immature animals is high, with 88% of the males and 65% of the females dying before 5 years. Adult mortality is low until 11 years, when it accelerates. The average adult life span is 16.6 years for males and 15.5 for females. The maximum life span is over 20 years. A pubertal male growth spurt occurs from 3 to 5 years, at which time females are primiparous. Sexual size differences develop primarily during this time. The 1976 age profile had anomalously few animals aged 7 years and males aged 8–9 and 15–16 years. With corroborating evidence, we hypothesize that these deficits resulted from excessive rainfall in 1963 and 1971, which reduced the fall fruit crop and led to a high juvenile mortality. Within half of our study troops, some adult males have nearly identical ages, suggesting an active process of agemate coalition. We hypothesize a form of kin selection, wherein peripheral male cohorts from the same natal troop have greater survival and social success than solitary animals. The stable model suggests an annual growth rate of 1.5% during the 1970s. Estimates of 16.7 and 4% for the previous two decades, following a yellow-fever epidemic, imply that the BCI population is becoming stationary. A very different age structure existed on neighboring Orchid Island in 1976, suggesting general food limitation. By contrast, the lowered, but continuing growth on BCI suggests a less drastic limiting mechanism. We hypothesize that intratroop social competition limits population growth by regulating subadult survival rates during food scarcity cycles.     

Demographic parameters of Brachionus calyciflorus Pallas (Rotifers) exposed to sublethal endosulfan concentrations

The effects of sublethal levels of endosulfan (0, 1, 1.5, 2.5 and 3.3 mg 1^–1) on the demography of the rotifer Brachionus calyciorus were studied. Life expectancy at birth (e _o), net reproductive rate (Ro), generation time (T) and intrinsic rate of natural increase (r) were significant differentes between blank controls and controls with acetone. The effective endosulfan concentration at which a given parameter value was reduced to 50% of the controls (EC50) was calculated for life expectancy.     

Effects of sex,size and substrate on growth and mortality of trees in tropical wet forest

Summary Females and males of three tree species did not differ in growth or mortality over an interval of 9.5 years. Comparing between sexes and across species, there was no consistent pattern of effects of short-term (1 year) growth and fecundity on longer-term gorwth or mortality. Effects of size were significant (but minor) for growth in one species, and were significant for mortality in two species. Soil type affected mortality in one species, but affected growth in all three species. Sex and size are not consistently strong bases for predicting the performance of adult trees.     

Responses to selection on genotypic or phenotypic values in the presence of genes with major effects

Summary Average genotypic responses were compared after selection for genotypic values and for phenotypic values on the basis of single-gene models and multigene models in simulated livestock populations. Single-gene models dealt with single gene control of the genetic differences between animals, while multigene models considered a collection of genes with various magnitudes of effects on a trait. In each case, selection lasted through discrete generations until the fixation of the gene frequencies occurred. Generations to reach fixation were used to compare various models, and the two criteria for selection, for their efficiency in selection. Implications of using these models versus using infinitesimal models for selection in practice are presented.     

Simplified neuron model as a principal component analyzer

A simple linear neuron model with constrained Hebbian-type synaptic modification is analyzed and a new class of unconstrained learning rules is derived. It is shown that the model neuron tends to extract the principal component from a stationary input vector sequence.     

Late pleistocene population dynamics: An alternative view

An attempt is made to argue for a more dynamic view of huntergatherer population behavior in place of the largely static one that has been widely accepted. Following a review of how the concept of carrying capacity has been used in both huntergatherer and ecological studies, attention is drawn to the role of stochastic factors in producing fluctuations over time among populations that are small in size. Some of the implications of this alternative view are briefly discussed.Research supported in part by NIH Grant GM 20467-03.This is a revised version of a paper presented at the symposium, Systems and Their Environments, at the Annual Meeting of the American Anthropological Association, 1973, New Orleans.     

Does directed technological change get greener: Empirical evidence from Shanghai's industrial green development transformation

The degree of technological change biased to the environmental factor is crucial to industrial sustainable development. Using the stochastic frontier analysis method based on the translog production function and the panel data of 32 industrial sub-sectors in Shanghai over 1994–2011, this paper combines the evolution dynamic of the frontier technological structure with the evolution dynamic of technological change direction to estimate the output elasticities of production factors and the growth rate of green total factor productivity. Also, we investigate and compare the degrees of technological change biased to four production factors, i.e., capital, labor, energy, and carbon emissions. The results show that the industrial green total factor productivity in Shanghai presents an overall upward trend and mainly depends on the technical efficiency change. The improvements of labor productivity, R&D intensity, and energy efficiency can effectively enhance the green technical efficiency, while capital deepening has a mitigation effect on the green technical efficiency. The technological change of Shanghai's industrial production biases to energy use and capital saving, causing a high energy demand of industrial development. Under the dual impacts of economic development and energy-saving and emission-reduction policies, the degree of technological change biased to the environmental factor (carbon emissions) displays strong and weak alternations, indicating that the green bias of industrial technological change in Shanghai is not stable and that the green transformation of industrial development model needs to be further advanced.     

Hill coefficient-based stochastic switch-like signal directly governs damage-recovery dynamics in freshwater fish in response to pulse copper

Growing evidence demonstrates that fluctuating metal stressors can have profound impact on the ecophysiological responses in aquatic species. However, how environmental stochasticity affects the complex damage-recovery dynamics in organisms remains difficult to predict. The objective of this paper was to investigate the stochastic behavior in the damage-recovery dynamics in tilapia in response to pulse waterborne copper (Cu). We developed a mathematical framework that allows discrimination between damage and recovery processes in tilapia exposed to designed pulse Cu scenarios. We built deterministic nonlinear models for the damage-recovery dynamics that produce response surfaces describing killing/recovery rate–Cu-pulse interval interactions. Here we showed that the stochastic switching behavior arose from competition among killing, recovery rates, and Cu pulse frequency. This competition resulted in an ultrasensitivity appeared in whole body, gills, muscle, liver, and kidney with Hill coefficients of ≥7, 4, 7, 5, and 5, respectively, at Cu 3 mg L⁻¹, dilution rate 0.05 h⁻¹, and pulse interval 72 h, indicating that a stochastic switch-like response was generated. We argue that the role of gill-associated Hill coefficient as a direct signal of the stochastic switch-like response in the damage-recovery dynamics in response to pulse metal stressor can serve as a sensitive indicator for risk detection in fluctuating environments. Our approach constitutes a general method to identify the stochastic switch-like response for aquatic species exposed to fluctuating metal stressors, which may help to predict and, eventually, expand our understanding of the damage-recovery dynamics. Finally, we implicate that Hill coefficient-based switch-like signal and its damage with hazard response can be linked in an information theoretic framework to handle environmental stochasticity.