Energetics,reproductive suppression and obligate communal breeding in carnivores

Summary Leptogenys processionalis Jerdon forages on termites and other arthropods by raiding in branched trails. Growth and topology of these search trails were studied using Horton's (1945) technique orginally developed to analyze the branching pattern of river systems. Branching was always a bifurcating process and branches emerged symmetrically on either side of the main trail. Branching coefficients (R _b ) were similar to those of a few biological branching systems, such as lungs, that are considered to be non-random in their branching pattern. The R _b values indicated that the rate of branching and growth of trails remained constant within each foraging bout. The length of trails became shorter as they grew out and branched. The branching process was a function of the spatial separation of food patches in the terminal search field. Ants in the terminal search field send signals on encountering prey. The recruits cannot discriminate between these signals if they arise from two food patches situated <40 cm from each other, and hence converge on them in a single trail. However, discrimination is possible when food patches are >40 cm apart and hence recruits congregate on them separately in two trails, resulting in branching. Thus, the branching process is a result of independent decision by the ants conforming to certain simple rules and not a collective decision of the whole colony. We argue that mass recruiting ants selected to forage by branching pattern of trails because of its efficiency over other topologies (Stevens 1973) in minimizing the cost of travel, both from the nest to the food patches and between food patches. Further, the branch angles appear to be a trade-off to minimize travel cost and the resistance to the flow of ants comprising the column.Offprint requests to: T. Veena     

Restoration of riparian forest using irrigation,artificial disturbance,and natural seedfall

In interior western North America, many riparian forests dominated by cottonwood and willow are failing to reproduce downstream of dams. We tested the hypothesis that establishment is now prevented by absence of the bare, moist substrate formerly provided by floods and channel movement. Along Boulder Creek, a dammed stream in the Colorado plains, we tested the effects of disturbance (sod removal), irrigation, and addition of seed on the establishment of seedings of plains cottonwood (Populus deltoides subsp.monilifera) and peachleaf willow (Salix amygdaloides). In unirrigated, undisturbed plots, mean cottonwood density was 0.03 seedlings/m². Irrigation or disturbance alone produced mean cottonwood densities of 0.39 and 0.75 seedlings/m². Plots that were both irrigated and disturbed produced a mean cottonwood density of 10.3 seedlings/m². The effects of irrigation and disturbance on cottonwood establishment were significant (P<0.005); added seed had no significant effect (P=0.78). The few cottonwood seedlings in unirrigated plots were in low positions susceptible to scour by future moderate flows. We conclude that cottonwood establishment along Boulder Creek is limited by the scarcity of bare, moist sites safe from future scour. Establishment of peachleaf willow was significantly affected only by disturbance; daily sprinkler irrigation did not provide sufficient moisture to increase survival of this species. Our results demonstrate the feasibility of restoring plains cottonwood forests using natural seedfall, even where only widely scattered adult trees are present. Because use of natural seedfall conserves the genetic makeup of the local population, this method may be preferable to the use of imported cuttings.     

Determination and implementation of optimal air quality standards

This paper utilizes two least-cost emission control strategies and develops rules for structuring and implementing optimal air quality standards. A strategy typical of those currently enforced, based on the State Implementation Plans (SIP's ), is compared to two least-cost strategies: (i) ambient least cost (ALC ), which achieves required air quality at least cost; and (ii) emissions least cost (ELC ), which achieves required emissions reduction at least cost. A demonstration is given of the theoretically derived result that the ALC strategy should be utilized in cost-benefit analyses to determine air quality standards and to generate emissions taxes. Preliminary analysis of the St. Louis area indicated tentative justification for a particulate ambient standard at least as strict as the current Federal primary standard. The efficiency, equity, and administrative costs for implementation of strategies based on the least-cost concept are also examined.     

ROAD DE-ICING SALTS IN AN URBAN STREAM AND FLOOD CONTROL RESERVOIR1

ABSTRACT: High concentrations of chloride and sodium were found in the bottom layers of a new flood control reservoir at the beginning of winter thaw periods. The reservoir had a number of significant downstream impacts. After short thaw periods, discharge from the bottom of the reservoir tended to cause higher salt concentrations downstream in comparison with upstream sites. During long thaw periods or when large quantities of rain fell, downstream salt concentrations were considerably less than upstream values. Average chloride and sodium content of soil at the bottom of the reservoir more than doubled as a result of impounding runoff waters for one winter.     

The effects of acid precipitation-long term ecological measurements in loch vale watershed,Rocky Mountain National Park

Contribution from Fourth World Wilderness Congress-Acid Rain Symposium, Denver (Estes Park), Colorado, September 11–18, 1987.     

Designing Impact Assessments for Evaluating Ecological Effects of Agricultural Conservation Practices on Streams1

Abstract: Conservation practices are regularly implemented within agricultural watersheds throughout the United States without evaluating their ecological impacts. Impact assessments documenting how habitat and aquatic biota within streams respond to these practices are needed for evaluating the effects of conservation practices. Numerous sampling protocols have been developed for monitoring streams. However, protocols designed for monitoring studies are not appropriate for impact assessments. We developed guiding principles for designing impact assessments of ecological responses to conservation practices. The guiding principles are as follows: (1) develop the hypothesis first, (2) use replicated experimental designs having controls and treatments, (3) assess the habitat and biological characteristics with quantitative and repeatable sampling methods, (4) use multiple sampling techniques for collecting aquatic organisms, and (5) standardize sampling efforts for aquatic organisms. The guiding principles were applied in designing a study intended to evaluate the influence of herbaceous riparian buffers on channelized headwater streams in central Ohio. Our example highlights that the application of our recommendations will result in impact assessments that are hypothesis‐driven and incorporate quantitative methods for the measurement of abiotic and biotic attributes.     

Vested Interest theory and disaster preparedness

Three studies were designed to extend a combination of vested interest theory (VI) and the extended parallel process model of fear appeals (EPPM) to provide formative research for creating more effective disaster preparedness social action campaigns. The aim was to develop an effective VI scale for assessing individual awareness and ‘vestedness’ relevant to disaster preparedness. Typical preparedness behaviours are discussed with emphasis on earthquakes and tornados in particular. Brief overviews of VI and the EPPM are offered, and findings are presented from three studies (one dealing with earthquakes, and two with tornados) conducted to determine the factor structure of the key VI components involved, and to develop and test subscales derived from the two theories. The paper finishes with a discussion of future research needs and suggestions on how the new subscales may be applied in the design and execution of more effective disaster preparedness campaigns.     

Is there a Dutch disease in Botswana?

The Dutch disease is regularly evoked in the resource curse literature and remains a frequent explanation for the poor economic performance found in many resource-rich countries. Given Botswana's high rate of per capita GDP growth, it might seem superfluous at first glance to ask whether or not there is a Dutch disease in Botswana. Yet, Botswana merits study here both as a significant potential exception to any posited inevitability of the Dutch disease and also because the debate on whether or not Botswana has avoided the Dutch disease is far less settled than is indicated by its economic growth record. Botswana currently suffers from many of the symptoms of the Dutch disease but not for the causal reasons posited in the Dutch disease model. Indeed, many of the explanations for the lack of diversification found in Botswana's mineral-dependent economy have nothing to do with either diamond revenues or the Dutch disease. Botswana has done about as well managing its resource wealth as could realistically be expected but it is unlikely to succeed in diversifying its economy away from diamonds anytime soon.     

Land clearance not dieback continues to drive tree loss in a Tasmanian rural landscape

Tree cover has declined markedly since European settlement in the agricultural areas of Australia due to land clearing and natural and stress-induced senescence of remnant trees combined with widespread regeneration failure. These decreases in tree cover have seldom been quantified on a landscape scale, but are important in understanding losses in carbon storage and biodiversity across large areas of the continent. We used historical aerial photography and satellite imagery to study changes in tree canopy cover in the southern Tasmanian Midlands, one of the oldest agricultural regions in Australia. Tree cover at 1,000 random sites was assessed from imagery captured on four occasions between 1947 and 2010. Tree cover was stable between 1947 and the 1970s, but decreased from 33 % in the 1970s to 21 % in 2010. The decrease appeared driven by transition from some cover to no cover, rather than from more cover to less cover, because sites with tree cover in 2010 showed little net change during the study period. Statistical modelling showed soils derived from igneous rocks lost more cover than did the less fertile sedimentary soils, and contrary to the expectations, if drought was the cause of cover loss, sun-exposed north-facing sites did not lose more cover than south-facing ones. We argue that these temporal and spatial patterns of tree cover change are consistent with tree clearing rather than loss of remnant isolated trees due to drought-induced dieback.