Factors influencing detection of nesting crested caracaras

Management of crested caracaras (Caracara cheriway), focuses on nests identified during surveys. If no nests are found, management can be suspended. Thus, false negatives can have substantial consequences. We surveyed 49 breeding territories to assess factors with the potential to cause false negatives in detecting nests of crested caracaras and in observing adult birds. The probability that a nest would be detected on any given visit increased by about 0.5% for each hour of observer experience up to about 70 hours (our maximum). Experience did not affect the probability of observing an adult. The probability of detecting a caracara nest or observing an adult caracara decreased by 2.0–3.5% each hour after sunrise that a visit began. If visibility during any portion of a visit was obscured by fog or rain, the probability of detecting a nest decreased by as much as 60%, and the probability of observing an adult caracara decreased by about 50%. We provide a tool managers can use to calculate the likelihood of successful surveys. We recommend that managers disregard negative results from surveys conducted under conditions that are unlikely to yield positive results, and repeat those surveys under better conditions. © 2011 The Wildlife Society.     

Stomatal response to plant water deficits

A steady state model of stomatal response to plant water deficit was developed. It simulates typical stomatal resistance-leaf water potential functions; that is, stomatal resistance remains relatively constant until leaf water potential decreases to a threshold value, at which point stomatal resistance increases abruptly. The model shows that differences in the elastic properties of guard cells and surrounding epidermal cells determine the shape of the stomatal resistance-leaf water potential function. The model also simulates the effects of seasonal osmoregulation. This relatively slow accumulation of osmotically active solutes within plant cells reduces the threshold leaf water potential value. By contrast, the relatively rapid diurnal accumulation of osmotically active photosynthates in non-guard cells raises the threshold leaf water potential. This effect can occur if guard cells have a mechanism such as a sugar-starch conversion which prevents osmotically-active photosynthates from accumulating in their vacuoles.     

Neighbourhood effects influence drought‐induced mortality of savanna trees in Australia

Questions: The following hypotheses of neighbourhood effects on drought‐induced mortality are evaluated: (A) drought‐induced stem death is randomly distributed in space, (B) stems are predisposed to drought‐induced death through negative density‐dependent effects and (C) stems are predisposed to drought‐induced death due to local deficits in plant available resources. Location: Central Queensland, Australia. Methods: Recent mass mortality of woody stems was surveyed and mapped in three 1.21‐ha quadrats within Eucalyptus melanophloia‐dominated savanna. A multi‐faceted analytical approach was adopted including spatial pattern analyses, two logistic regressions of neighbourhood density effects on survival and spatial autocorrelation analyses of model residuals. Results: Mortality was concentrated in stems ≤15‐cm diameter at breast height (DBH). Survival was aggregated or random in quadrats 1 and 3 and random o regular in quadrat 2. Small neighbour density had a negative effect on survival in all quadrats. In addition, the second model identified a positive relationship between survival and living neighbour density in quadrat 3 (indicating a resource patch effect), but a negative relationship in quadrat 2 (density effect). Analysis of model residuals showed that neighbour density explained mortality equally well across quadrat 2, but not across quadrats 1 and 3. Conclusions: There was evidence in support of hypotheses B (neighbour density) and C (resource heterogeneity). We found strong support for an interaction between microsite quality and neighbourhood stem densities, and suggest that this interaction is driven by plant available water.     

Stigma and Self-Stigma in Addiction

Addictions are commonly accompanied by a sense of shame or self-stigmatization. Self-stigmatization results from public stigmatization in a process leading to the internalization of the social opprobrium attaching to the negative stereotypes associated with addiction. We offer an account of how this process works in terms of a range of looping effects, and this leads to our main claim that for a significant range of cases public stigma figures in the social construction of addiction. This rests on a social constructivist account in which those affected by public stigmatization internalize its norms. Stigma figures as part-constituent of the dynamic process in which addiction is formed. Our thesis is partly theoretical, partly empirical, as we source our claims about the process of internalization from interviews with people in treatment for substance use problems.     

Binding of multivalent ligands to mobile receptors in membranes

We present a model to describe the equilibrium binding properties for the attachment of multivalent ligands to mobile receptors in membranes. The interaction is assumed to be governed by two inherently different association constants. The first of these controls the initial attachment of a ligand to its first receptor, by adsorption from bulk solution, while the second governs subsequent receptor attachments to this initially bound ligand by rearrangement of membrane-bound species. Simple statistical mechanical expressions are used to estimate contributions to these association constants that are attributable to losses of translational and rotational degrees of freedom occurring upon binding. Suitable combinatorial expressions are combined with these association constants to derive the concentrations of bound species and the binding isotherms. Examination of these expressions leads to the conclusion that once initially bound, most multivalent ligands will be completely saturated by receptors and that partially bound species will be essentially nonexistent. This behavior is attributable to the generally high overall affinities of these ligands and to the mobility of the membrane-bound species. Some specific comments are made, in light of this theory, about the binding of cholera toxin to its membrane receptor, the ganglioside G_M1.     

Responses to a Drought in the Interior Lowlands of Papua New Guinea: A Comparison of Bedamuni and Kubo-Konai

The ways that people experience, respond to and pattern recovery from major climatic aberrations must be understood within the context of existing socioeconomic arrangements and the ethos that informs these. This paper describes immediate and longer term impacts of a major drought on two populations—Bedamuni and Kubo-Konai—in the interior lowlands of Papua New Guinea. Though they occupy similar environments, are culturally related and reliant on similar technology and resources, these two populations differ in density, intensity of land use, and social complexity. The drought of 1997 affected one of the populations much more severely than the other. A comparison of effects on subsistence regimes, mobility and social life in the two areas suggests that these were mediated by understandings people held of relationships with both the environment and other people. Bedamuni pattern their lives around an expectation of favorable returns on effort, emphasising security of tenure to protect those returns. Kubo-Konai, in contrast, pattern their lives around an expectation that availability of resources will be often in flux, and emphasise means of ensuring security of supply. These understandings are reflected, respectively, in risk-prone and risk-averse strategies of subsistence and sociality which directly influence vulnerability and responses to disruptive events.