Policy-relevant nonconvexities in the production of multiple forest benefits

This paper challenges common assumptions about convexity in forest rotation models which optimize timber plus nontimber benefits. If a local optimum occurs earlier than the globally optimal age, policy based on marginal incentives may achieve suboptimal results. Policy-relevant nonconvexities are more likely if (i) nontimber benefits dominate for young stands while the optimal age depends primarily on timber benefits, or (ii) nontimber benefits dominate for mature stands and also determine the optimal age. Nonconvexities may create either temporary or persistent difficulties. Policymakers may improve efficiency by exploiting the relationship between the timber-only optimum and the global optimum.     

Sperm swimming speed and energetics vary with sperm competition risk in bluegill (<Emphasis Type="Italic">Lepomis macrochirus</Emphasis>)

Under sperm competition, a males fertilization success depends largely on the ejaculate characteristics of competing males. Theoretical models predict that, in external fertilizers, increased risk of sperm competition should result in selection for increased sperm swimming speed. To test this prediction, we studied the behavior of sperm from parental and sneaker male bluegill (Lepomis macrochirus), a fish species characterized by high levels of cuckoldry due to alternative reproductive tactics of males (parentals and cuckolders). Because cuckolders (sneakers and satellites) always spawn in the presence of a parental male, but the reverse is not true, cuckolders experience the greater risk of sperm competition. We show here that the spermatozoa of sneakers have faster initial swimming speeds but shorter periods of motility than the sperm of parental males. Moreover, we show that sperm swimming speeds shortly after activation (when most fertilization occurs) are correlated with starting ATP levels in spermatozoa, suggesting that sperm competition has selected for higher energetic capacity in the sperm of sneakers. Thus, the higher energetic capacity and initial swimming speed of sneaker sperm may explain why, despite having fewer sperm per ejaculate than parentals, sneakers fertilize more eggs than parental males when they compete to fertilize a clutch of eggs.Communicated by L.W. Simmons     

Modeling joint production of wildlife and timber

Production of marketed commodities and protection of natural systems often conflict. A focus on only one goal can result in large losses in other goals and may result in inefficient and unsustainable outcomes. In this paper, we develop a method that combines economic and ecological models in a dynamic and spatial analysis to evaluate land use decisions and find cost-effective alternatives for which it is not possible to do better on one objective without harming another objective. The method is demonstrated using timber production and species conservation on a forested landscape over a 100-year planning horizon. Current land use strategies are simulated and compared with cost-effective alternatives. The approach is compared to a static reserve approach, similar to previous studies, and found to produce substantially more efficient management strategies for the case study landscape.     

Copper, Lead and Zinc Mobility and Bioavailability in a River Sediment Contaminated with Paint Stripping Residue

A river embankment sediment beneath a road bridge in South Australia had been surveyed on a previous occasion to a depth of 10 cm and found to contain high levels of copper, lead and zinc deposited during previous lead and zinc-based primer paint stripping operations prior to repainting the bridge. Since the river embankment is geologically different from the surrounding non-embankment soils, and a sufficient distance from the bridge along the river embankment could not be traversed, the geological background Cu, Pb and Zn fraction was established initially using a solid phase sequential extraction (SPSE) procedure. Assessment of the degree of contamination and extent of vertical mobility was then established. Copper was a minor contaminant and present predominantly as the geological background species. Lead was partitioned evenly between the oxalate soluble fraction and residual fraction to a depth of 30 cm with a decrease in total Pb concentration from 497 to 141 mg Pb kg^–1 while Zn was predominantly in the oxalate soluble fraction to a depth of 15cm with a decrease in concentration from 1013 to 150 mg Zn kg^–1. The reduced rate of nitrification and the lower total concentration of NO₃ ^–-N together with the higher respiratory quotient, combined with the lower microbial quotient, are indicative of microbial stress due to heavy metal toxicity. In the case of Pb and Zn paint stripping residues, these changes in indicators of microbial health are possibly the result of the greater abundance and hence possible bioavailabilty of organo- and chloro-Pb compared to organo- and chloro-Zn complexes.     

Family structure influences mate choice in white-fronted bee-eaters

White-fronted bee-eaters live in patrilocal, extended family groups in which several pairs may breed simultaneously and in which helping behavior by nonbreeders is common. The composition of a male's family, and his social position within it, are major predictors of his expected reproductive success. For females, the dispersing sex, a decision to pair necessitates forfeiting any potential fitness benefits available through helping in her family, in favor of the potential benefits of breeding in the male's family. Using a set of equations that incorporate the social and non-social predictors of nesting success, we develop a payoff matrix for the expected fitness (current and future) of pairing with different categories of males. Predictions generated from this payoff matrix were supported by data: (1) Females that could help close kin (and thus garner large indirect benefits) tended to remain unpaired. (2) Males with social characteristics associated with low expected reproductive success were more often rejected as potential mates by females. (3) High-quality males, those with potential helpers of their own, were nearly always paired. Simulation analyses were used to investigate female pairing decisions in more detail, and to test various hypotheses about possible decision rules. We demonstrate that pairing females incorporate an assessment of the family structure of potential partners into their mate choice decisions. Such social characters represent an aspect of female choice that has been underappreciated. We suggest that social characters will prove to be important components of mate choice decisions in many species where kinship and dominance considerations influence the likelihood, or success, of breeding.     

Attraction of field-flying aphid males to synthetic sex pheromone

Summary Transparent plastic water traps, baited with the synthetic aphid sex pheromone components (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol or control lures, were placed in four semi-sheltered field sites at a height of 1.1 m. Although males of twenty-one aphid species were collected from the water traps, onlySitobion fragariae (Walker) was abundant. In total, 8 pheromone traps produced 102 males compared with only 10 males in 8 control traps. The sex pheromone released by sexual femaleS. fragariae was identified as the nepetalactone used in the lures. Aphid sex pheromones may be more species-specific than previously thought and the presence of a host plant is not essential for males to locate sexual females.     

Role of esters in egg removal behaviour in honeybee (Apis mellifera) colonies

In queen-right honeybee colonies workers detect and eat the vast majority of worker-laid eggs, a behaviour known as worker policing. However, if a colony becomes permanently queen-less then up to 25% of the worker population develops their ovaries and lay eggs, which are normally reared into a final batch of males. Ovary development in workers is accompanied by changes in the chemical secretion of the Dufour's gland with the production of queen-like esters. We show that ester production increases with the period that the colony is queen-less. The increased ester production also corresponds to an increase in persistence of worker-laid eggs in queen-right colonies, since the esters somehow mask the eggs true identity. However, in a rare queen-less colony phenotype, workers always eat eggs indiscriminately. We found that the egg-laying workers in these colonies were unusual in that they were unable to produce esters. This apparently maladaptive egg eating behaviour is also seen in queen-less colonies prior to the appearance of egg-laying workers, a period when esters are also absent. However, the indiscriminate egg eating behaviour stops with the appearance of ester-producing egg-laying workers. These observations suggest that esters are providing some contextual information, which affects the egg eating behaviour of the workers.     

Long-term tillage effects on soil metolachlor sorption and desorption behavior

Sorption and desorption are two important processes that influence the amount of pesticides retained by soils. However, the detailed sorption mechanisms as influenced by soil tillage management are unclear. This study examined the sorption and desorption characteristics of metolachlor [2-chloro-N-(2-ethyl-6-methyphenyl)-N-(2-methoxy-1-methylethyl)-acetamide] using the soil samples collected from the long-term conservation tillage (CnT) and conventional tillage (CT) research plots established in 1979 in Darlinton, SC. Humic acid (HA) and humin were extracted from the soils and used in the sorption experiments along with the whole soil samples. The sorption experiments were conducted using a batch-equilibration method. Three sequential desorption rinses were carried out following the sorption experiments. By comparing metolachlor sorption and desorption results we observed hysteresis for all soil samples and their organic matter fractions. Sorption nonlinearity (N) and hysteresis were dependent on the structure and composition of soil organic matter (SOM), e.g., Freundlich isotherm exponents (N) of HA and humin from CnT were higher than those of CT treatment, which may be related to high aromaticity of SOM fractions in CT treatment. Sorption capacity (K'f) was positively correlated with soil organic carbon (SOC) content. These results show that long-term tillage management can greatly affect metolachlor sorption and desorption behavior probably by qualitative differences in the structural characteristics of the humic substances.     

Effects of changes in climate on landscape and regional processes, and feedbacks to the climate system

Biological and physical processes in the Arctic system operate at various temporal and spatial scales to impact large-scale feedbacks and interactions with the earth system. There are four main potential feedback mechanisms between the impacts of climate change on the Arctic and the global climate system: albedo, greenhouse gas emissions or uptake by ecosystems, greenhouse gas emissions from methane hydrates, and increased freshwater fluxes that could affect the thermohaline circulation. All these feedbacks are controlled to some extent by changes in ecosystem distribution and character and particularly by large-scale movement of vegetation zones. Indications from a few, full annual measurements of CO2 fluxes are that currently the source areas exceed sink areas in geographical distribution. The little available information on CH4 sources indicates that emissions at the landscape level are of great importance for the total greenhouse balance of the circumpolar North. Energy and water balances of Arctic landscapes are also important feedback mechanisms in a changing climate. Increasing density and spatial expansion of vegetation will cause a lowering of the albedo and more energy to be absorbed on the ground. This effect is likely to exceed the negative feedback of increased C sequestration in greater primary productivity resulting from the displacements of areas of polar desert by tundra, and areas of tundra by forest. The degradation of permafrost has complex consequences for trace gas dynamics. In areas of discontinuous permafrost, warming, will lead to a complete loss of the permafrost. Depending on local hydrological conditions this may in turn lead to a wetting or drying of the environment with subsequent implications for greenhouse gas fluxes. Overall, the complex interactions between processes contributing to feedbacks, variability over time and space in these processes, and insufficient data have generated considerable uncertainties in estimating the net effects of climate change on terrestrial feedbacks to the climate system. This uncertainty applies to magnitude, and even direction of some of the feedbacks.     

Early prenatal sonographic appearance of rare thoraco-abdominal eventration

Fetal ventral wall malformations may be diagnosed prenatally with ultrasound. These include omphalocele, gastroschisis, or even thoracic defects with or without ectopia cordis. It is important whenever such a defect is found to carefully define the full extent of the lesion prior to parental counselling. Described and illustrated here is the prenatal diagnosis with real-time ultrasound at 17 weeks gestation of a rare thoraco-abdominal ventral wall defect including omphalocele, bifid sternum, diaphragmatic aplasia, and pericardial aplasia with incomplete ectopia cordis. The technique is described and the importance of the complete, accurate delineation of anatomic malformations is emphasized.