bluuebunny/crossref_metadata_2025 huggingface dataset:
Aspects of the Ashanti Northern Trade in the Nineteenth Century
Authors: Arhin Kwame
Published: April 2006

Opening Paragraph

I Mean by the Ashanti northern trade Ashanti market exchanges with Hausa, Mande, and Mossi caravan traders at the town of Bonduku (eastern Ivory Coast), Salaga (northern Ghana) before 1874, and at Kintampo (Brong-Ahafo Region of Ghana) 1874-92. The main facts relating to this trade are well known to students of Ashanti. This paper attempts (i) to establish the basis of the Ashanti trading relationship with the northern peoples; (ii) to make distinctions between types of Ashanti traders, the scale and results of their operations, and to describe the production and distribution of kola from Ashanti; and (iii) finally to draw attention to those features of the nineteenth-century trade which contribute towards the understanding of what Tordoff(1965: 187) has called ‘the emergence and phenomenal growth of the cocoa industry’ in the early years of this century.
Poverty, Work and the Financing of Single Women in Kampala
Authors: Mandeville Elizabeth
Published: April 2006

Opening Paragraph

This paper examines the financial position of all-female households in a poor area of Kampala, Uganda. The intention is to indicate the relative standards of living of households of various composition and to decide whether the practice of soliciting money from lovers is better viewed as a preferred alternative to employment or as an essential supplementing of inadequate incomes. If lovers are necessary to the maintenance of single women and their children in African cities, analyses of extra-marital sexual behaviour which rely only on arguments about marriage rules and roles and personal values are rendered inadequate. Securing a paying lover may be indispensable to a woman who wishes to live and bring up children in town, and the practice may tell us more about her wish to educate her children, or her dislike of rural life, than it does about her sexual and marital preferences. Love affairs, in short, may be more appropriately considered under the heading of domestic finance than as an adjunct to a discussion of marriage. The data which I present here do not reduce a lover's importance to a woman to that of a charitable institution or welfare state: women who are prosperous have love affairs, and sexual pleasure is celebrated. They do indicate, however, the difficulties faced by a woman anxious to remain in town if she is not prepared to take lovers and to select them at least in part according to financial considerations. I hope, too, that the method which I use for working out standards of living available to households may prove useful as a means of establishing comparability between living standards in different cities.
Results and Implications of the Preliminary Enquiry
Authors: Southall Aidan
Published: April 2006

Opening paragraph

In choosing small urban centers for study and arguing that they were strategic for development, we did not suggest that small urban centers were at present generally playing a positive role in rural development, nor that it would necessarily be easy to get them to do so without major changes or even radical transformations of society. The argument was, that if effective rural development were achieved, small urban centers would certainly have to play a crucial part in it. They may therefore act as sensitive barometers of the adequacy or inadequacy of rural development efforts. Combing the literature on small urban centers in Africa, and in Asia and Latin America as well, has certainly convinced this writer that the instances in which small urban centers are playing anything like an adequate positive role are distinctly rare, and most situations convey the very strong impression that quite fundamental transformations of society—of political and economic structures—will be necessary if they are to have any serious chance of doing so. To study small urban centers without paying attention to the macroeconomic and political context in which they are set may therefore be futile.
Growth and Development Patterns of Awka and Nsukka, Nigeria
Authors: Dike Azuka A.
Published: April 2006

Opening Paragraph

The growth and development of a town are mainly reciprocals of population growth, location of industries and specialization of the inhabitants. Nsukka and Awka represent two points on our developmental scale. Their growth and development while comparable in some ways are functions of different variables.
Tiv Proverbs as a Means of Social Control
Authors: Bergsma Harold M.
Published: April 2006

Introduction

Of all the verbal art forms employed by the Tiv, such as singing, story-telling, and proverbs, the last are the most consistently used in everyday situations. Elders today often converse by means of proverbs to prevent young listeners from understanding what they are talking about, for many youngsters have not learned the use of proverbs because they have been to school or away from home for extended periods and have thus lost touch with ‘archaic’ usages.

Proverbs are employed in a variety of situations: to control activities without the use of force, as devices for shaming, for getting out of difficult situations without losing face, as a means of praise, in prophetic utterances, and as general explanations for that sphere of Tiv environment which is beyond comprehension, especially illness or ‘acts of God’.
Cosmologie et structuration de l'espace chez les Komo
Authors: de Mahieu Wauthier
Published: April 2006

Comme tout groupe humain, les Komo éprouvent le besoin d'harmoniser leuts expériences ou l'ensemble des phénomènes qu'ils vivent, quel que soit le niveau où ceux-ci se situent ou le domaine dont ils relèvent. Or, ces expériences ont toutes lieu dans un cadre spatial, qui en fait toujours implicitement partie, mais qui, à certains moments, constitue l'objet privilégié de l'expérience. Le besoin d'harmonisation implique done que ce cadre soit structuré en fonction de cet ensemble. Cette harmonisation se fait dans un mouvement dialectique qui comporte autant de pôles qu'il y a de domaines à unifier et respecte la priorité ontologique de chacun de ceux-ci à son propre niveau. Ainsi, le cadre spatial possède sa priorité topologique dont cette recherche d'harmonisation ne pourra pas ne pas tenir compte. Ce sera le décalage entre ces données topologiques premières et leur relecture dans cet effort d'harmonisation qui fera de celle-ci un processus de symbolisation.
Taaken Sàmàarii: a Drum Language of Hausa Youth
Authors: Ames David W. , Gregersen Edgar A. , Neugebauer Thomas
Published: April 2006

Introduction

This collaboration began when Ames and Gregersen met in Zaria, the capital of one of the old Hausa kingdoms in northern Nigeria. Gregersen, an anthropological linguist, was collecting material for a grammar of Hausa language, and Ames was making an anthropological study of the status and role of professional musicians.
Introduction. Understanding African Land-Holding: Power, Wealth, and Meaning
Authors: Shipton Parker , Goheen Mitzi
Published: April 2006

Africa is the region with the sparsest overall population, but to infer that Africa has no problems of rural land shortage would be quite wrong. The continent has the highest and fastest-rising rate of population growth—lately over 3 per cent annually—and the distribution of people across the continent is quite uneven. At least as far as rain-fed lands are concerned, some of its local densities already count among the world's highest. Several of its nations—for instance Kenya, Tanzania, and Nigeria—encompass within their borders a full spectrum from range land or desert with fewer than five per square kilometre to better-watered settlements of over 500 per square kilometre, where domestic groups have space for little more than kitchen gardens.
Economic models and having children: some evidence from Kwahu, Ghana
Authors: Oppong Christine , Bleek Wolf
Published: April 2006

Opening Paragraph

This paper is concerned with aspects of reproduction and fertility among the Kwahu of southern Ghana, an Akan sub-group, and more particularly among the members of a lineage in one rural town characterised by profound socio-economic change and differentiation. Fragments of the field data presented are taken from a larger corpus of materials focusing on family life, sexuality and birth control collected during the early 1970s.

The data discussed here pertain to people's decisions whether or not to practise contraception, to have abortions, to carry pregnancies to full term – in short, whether or not to regulate their fertility by traditional and modern chemical and mechanical methods. We note as we proceed why some individuals will terminate a pregnancy at all costs, even risking life and health to do so, and why others have a fatalistic or casual approach to the results of their activities and the outcome of their pregnancy. These materials are presented within the context of a brief account of some current problems encountered in micro-economic demographic modelling exercises based on rational decision-making premisses, and of recent attempts to build bridges between ethnographers and economists.
Chiefship and the history of Nyavingi possession among the Bashu of eastern Zaire
Authors: Packard Randall M.
Published: April 2006

Opening Paragraph

Nyavingi possession has had a long and varied history among the peoples who occupy the borderlands of northern Rwanda, south-western Uganda and eastern Zaire. Jim Freedman (1974, 1979), Who has studied the cult's early history and diffusion, has suggested that Nyavingi, or Nyabingi, as it is more frequently spelled, initially emerged in association with the rule of the Bashambo clan in the ancient kingdom of Ndorwa, although its role as a religious support for Bashambo rule may only date from the collapse of Ndorwa and the establishment of Bashambo kingdoms to the west of Lake Bunyoni in Kigezi and in the Mutara district of Rwanda at the end of the eighteenth century. While it is perhaps impossible to define the exact role which Nyavingi played in the Bashambo states, Freedman suggests that, at least in the successor states, Nyavingi represented a powerful spirit of a deceased female ancestor of the Bashambo. Hopkins (1969) notes, in addition, that, as a result of its support of Bashambo rule in northern Rwanda, Nyavingi became a focus of local resistance to Tutsi political expansion into the region.
Women's agricultural production and political action in the Cameroon Grassfields
Authors: Diduk Susan
Published: April 2006

Opening Paragraph

On that day if you had seen me, you would not have known me; dirty cap with feathers and a long stick, since doesn't fear send a walking stick forward? I put dirty clothes on and I looked like ‘massa’ [my husband]. I even wore plant leaves around my neck so as to make all men [people] put their minds to this [problem].…Today fombuen doesn't march because there isn't trouble but if cows come again they will join! Women know the sound of the whistle and they will leave their cooking pots on the fire. [A Kedjom Ketinguh woman who participated in the 1958 fombuen march to Bamenda]
Religion and ethnicity in the arts of a Limba Chiefdom
Authors: Ottenberg Simon
Published: April 2006

Opening Paragraph

This article examines the major visual and performing arts of one society and explores what changes have occurred to them over roughly one hundred years as a consequence of external religious and ethnic forces. This is a holistic, processual view of a people's arts in a particular region, providing a model to balance the excellently detailed studies of specific art forms which now exist for Africa. Using a holistic view we will raise certain issues concerning changes in African art. One of the most significant is the interrelationship of ethnicity and religion. Scholars (Bravmann, 1974, 1983; Prussin, 1986) have written extensively on the influence of Islam on African art, but have not seriously raised the question of the ethnic factor associated with Islam, which is equally important. In the case of Islam and its carriers there is a delicate intermixing of religion and ethnicity which is at issue and needs exploration. Further, the holistic approach employed here brings to the fore the reasons behind the wide range of responses to change of the various art forms of a people. Why do some syncretise, some disappear and others remain unchanged? Again, the holistic view allows us to ask to what extent the arts of a people merely reflect forces of change, or do they play roles in leading and directing it? The approach requires considerable background history, which is presented below.
Creating a text: alternative interpretations of Gonja drum history
Authors: Goody Esther , Goody Jack
Published: April 2006

Drum chants in Damongo (northern Ghana) are recited in a ‘deep’ Gonja that few understand. In transcribing them (and thereby creating a text), the potential for variant interpretations is very great, as is shown by comparing a sample of J. A. Braimah's rendering with one prepared with the help of the drummers by Esther Goody in 1964-65. The text J. A. Braimah published supports a particular view of Gonja's past.
Prehistory and Ideology in Zimbabwe
Authors: Garlake P. S.
Published: April 2006

Opening Paragraph

Zimbabwe has adopted the name of the Shona state, centred on the city of Great Zimbabwe, which flourished between five and eight hundred years ago, and whose ruined stone walls are one of the most remarkable monuments in Africa. Great Zimbabwe was a considerable human achievement, evidence of the acquisition and management of a huge and docile labour force, of prolonged political stability and economic prosperity.

When the British South Africa Company occupied the country in 1890 the monument became the subject of considerable settler polemic and controversy. While its origins were still uncertain Cecil Rhodes recognized the considerable propaganda value that evidence of ancient foreign settlement, preferably white and successful and with Biblical origins, would have. It would give a precedent and respectability to the conquest and a promise of similar prosperity to the settlers and investors in the new colony. Rhodes acquired many antiquities from Great Zimbabwe, and initiated excavations at the site and searches of the archives of Rome and Lisbon for documents referring to it. He himself sought parallels to its art in the museums of Cairo. He also commissioned eminent mining engineers to determine the origins and yield of the ‘ancient gold workings’ in the country. Finally, he had Richard Hall, an enthusiastic propagandist of the settler cause in newspapers, lectures and exhibitions, and a fanatical advocate of immensely old Biblical origins for Great Zimbabwe, appointed curator of the Ruins expressly to instruct important visitors in his theories.
Doglientiri: an institutionalised relationship between women among the Bulsa of northern Ghana
Authors: Meier Barbara
Published: April 2006

This article focuses on the institutionalised relationship between a married woman and a younger woman of her lineage. This alliance implies that the older woman incorporates her clan sister into her household and later marries her off to a man of her choice, preferably her own husband or one of his (classificatory) brothers. This specific form of sororal polygyny is firmly based on rituals and the structure of kinship relation among the Bulsa of northern Ghana. Women bear the ritual responsibility for their brothers' offspring and therefore acquire the right to adopt their daughters.
Rationalising culture: youth, elites and masquerade politics
Authors: Rea William R.
Published: April 2006

Studies of associations in West Africa have tended to focus upon the development of new development-related institutional forms. Other, so-called traditional, cultural groupings have tended to be ignored. This article points to transformations and changes in the masquerade society of the north-eastern Yoruba town of Ìkòlé and considers the continuing development of the masquerade society as an association. Changes in the masquerade society are being strongly promoted by younger men as a way to establish masquerade as a resource, promoting Ìkòlé's cultural identity. They are aided and funded by groups of elite citizens who are not necessarily resident in Ìkòlé. The article examines the relations between the various groups involved in masquerade, as well as the relationship between those often elite town members who support masquerades and Pentecostal Christian groups which would happily see their demise.
The Effects of Climate Change on Decomposition Processes in Grassland and Coniferous Forests
Authors: Anderson J. M.
Published: April 2006

Current models of climate change predict a reduction of area covered by northern coniferous forests and tundra, and an increase in grasslands. These scenarios also indicate a northerly shift in agricultural regions, bringing virgin soils under cultivation. The direct effects of man on tundra, boreal forest, and temperate grassland ecosystems are likely to result in less carbon mobilization from soils and vegetation than from tropical forests. However, as a consequence of climate change, carbon mineralization rates from arctic and sub—arctic soils could be very rapid under warmer and drier conditions because of low stabilization of soil organic matter (SOM) and enhanced microbial responses to small changes in soil moisture and temperature. Predicting the response of these systems to climate change is complicated where the edaphic environment regulating SOM dynamics is not a direct function of macroclimatic conditions. Grasslands contain a greater proportion of highly stabilized SOM than coniferous forests, distributed over greater depth in the soil profile, which is less susceptible to changes in mineralization rates. It is concluded that short—term responses of soil processes to climate change are more predictable in well—drained grassland and forest soils than in waterlogged soils of the tundra and boreal region. Over longer periods of time, however, plant species and soil types will alter in response to new temperature and moisture regimes above— and belowground interacting with the effects of carbon enrichment and changes in nutrient availability. The dynamics of these plant—soil interactions and the future status of soils in different life zones as sources or sinks of carbon is poorly understood. More data are also needed on the distribution of waterlogged forest soils in the boreal zone and responses to warming, which include the production of methane as well as CO2. The primary recommendation for future research is for integrated studies on plant and soil processes.
State‐of‐the‐Art of Models of Production‐Decomposition Linkages in Conifer and Grassland Ecosystems
Authors: Agren Goran I. , McMurtrie Ross E. , Parton William J. , Pastor John , Shugart Herman H.
Published: April 2006

We review the state—of—the—art of models of forests and grasslands that could be used to predict the impact of a future climate change arising from increased atmospheric carbon dioxide concentration. Four levels of resolution are recognized: physiologically based models, population models, ecosystem models, and regional or global models. At the physiological level a number of important processes can be described in great detail, but these models often treat inadequately interactions with nutrient cycles, which operate on longer time scales. Population and ecosystem models can, on the other hand, encapsulate relationships between the plants and the soil system, but at the expense of requiring more ad ho formulations of processes. At the regional and global scale we have so far only steady—state models, which cannot be used to predict transients caused by climate change. However, our conclusion is that, in spite of the gaps in knowledge, there are several models based on dominant processes that are well enough understood for the predictions of those models to be taken seriously.
Preserving Biodiversity: Species, Ecosystems, or Landscapes?
Authors: Franklin Jerry F.
Published: April 2006

Efforts to preserve biological diversity must focus increasingly at the ecosystem level because of the immense number of species, the majority of which are currently unknown. An ecosystem approach is also the only way to conserve processes and habitats (such as forest canopies, belowground habitats, and hyporheic zones) that, with their constituent species, are poorly known. Continued concern with species is essential, however. Landscape—level issues also need much greater attention. Designing an appropriate system of habitat reserves is one landscape—level concern. Understanding and appropriately manipulating the landscape matrix is at least equal in importance to reserves issues, however, since the matrix itself is important in maintaining diversity, influences the effectiveness of reserves, and controls landscape connectivity.
Invasion Resistance to Introduced Species by a Native Assemblage of California Stream Fishes
Authors: Baltz Donald M. , Moyle Peter B.
Published: April 2006

Assemblages of native stream fishes in California show a remarkable ability to resist invasion by introduced fishes as long as the streams are relatively undisturbed by human activity. Previous studies had indicated a high degree of spatial (microhabitat) segregation among the native fishes, which was confirmed by a principal components analysis of microhabitat use data from Deer Creek, a tributary of the Sacramento River. A null modelling study using the same data set was performed to see if competition was a major force structuring the assemblage, because theoretical studies had indicated that a competitively structured assemblage should be most able to resist invasions. The null models indicated that competition was not the major structuring force, so it is likely the assemblages are structured through a combination of morphological specialization (reflecting evolutionary history), predation, and some competition. The assemblages resist invasion through both environmental and biotic factors. Predation seems to be an especially important biotic factor.
Contrasting the Tolerance of Wild and Domesticated Tomatoes to Herbivory: Agroecological Implications
Authors: Welter Stephen C. , Steggall John W.
Published: April 2006

Application of plant life—history theory to strategies for breeding crop plants for sustainable agriculture remains relatively unexplored. We determined the relative tolerance of wild and domesticated tomatoes to simulated herbivory and evaluated plant characteristics that may contribute to tolerance. Wild and domesticated tomatoes were subjected to different levels of defoliation ranging from 0 to 70%. Single defoliation events at lower levels (15—30%) did not significantly affect total fruit mass produced in either wild or domesticated tomatoes. Increased defoliation resulted in significant reductions in total fruit mass per plant and mean mass per fruit. Reduction in fruit output by the cultivar was °3 times greater than the wild tomato for the first 8 wk of fruit production, whereas the loss in seasonal fruit production by the cultivar was 1.7 times greater than the wild tomato. We concluded that domestication of tomatoes may have decreased their relative tolerance to herbivory. Possible mechanisms for decreased tolerance include differences in leaf area index, light capture curves, and the relative allocation pattern to vegetative growth vs. reproductive structures. Optimization of potential life—history trade—offs between tolerance to herbivory and maximum fruiting abilities are proposed for cultivars of sustainable agriculture.
Modifying Scent‐Marking Behavior to Reduce Woodchuck Damage to Fruit Trees
Authors: Swihart Robert K.
Published: April 2006

Woodchucks (Marmota monax) damage fruit trees by gnawing on main stems during scent marking, a behavior unrelated to feeding. I tested whether damage could be reduced by providing alternative sites for scent marking or by applying predator odor to trees. Nearly all hardwood stakes supplied as alternative sites for scent marking were used, and the elapsed time from activation of a burrow until onset of damage to an adjacent tree was significantly greater for sites with stakes. However, the mean level of damage to trees was not significantly reduced. Impregnating hardwood stakes with sodium chloride increased their use as gnawing sites relative to untreated stakes, presumably due to dietary sodium deficits incurred by woodchucks during spring. Use of NaCl—treated stakes did not reduce damage to adjacent trees, however. Application of a predator odor, bobcat urine, as a topical spray reduced mean levels of gnawing by 98.3% relative to untreated trees, and placement of bobcat urine in capillary tubes at the bases of trees also resulted in significant reductions in damage over a 3—mo period.
The Lowland‐to‐Upland Transition‐‐Modelling Plant Responses to Environmental Change
Authors: Woodward F. I.
Published: April 2006

A published correlative model has predicted that the distributional limits of plants and vegetation zones on mountains will increase in altitude with global warming. I test this hypothesis using results from published experimental studies. Investigations and models of the responses of leaf growth to temperature are in accord with the prediction. However, the individualistic responses of species to CO2 enrichment indicate that the prediction is unlikely to be true for all species: growth is stimulated by CO2 enrichment for some species but not for others. Wind speed generally increases with altitude on mountains, and plants from high altitude tend to be more wind resistant than species from the lowland. Therefore it is expected that, particularly on wind—swept mountains, global warming will not necessarily be followed by the spread of lowland species into the uplands.
Material Fluxes Across Wetland Ecotones in Northern Landscapes
Authors: Johnston Carol A.
Published: April 2006

The spatial and temporal distribution of sediment, nutrients, and cations in a 2—ha wetland near Shawano, Wisconsin (USA) was used to evaluate the effect of wetland ecotones on water— and windborne fluxes at ecosystem and landscape scales. Within the wetland ecosystem the ecotones studied were beach ridges deposited by post—glacial White Clay Lake, and stream levees deposited by a second—order stream flowing through the wetland. Snow, soil, and surface water data collected from a 52—point sampling grid were geostatistically analyzed to derive contour plots of within—wetland concentrations. Wind—blown snow form the frozen lake surface accumulated in the wetland behind a low beach ridge to a depth of >65 cm, nearly 7 times the depth at wind—protected areas of the wetland. As a result of this snow accumulation, areas to the lee of the beach ridge annually received 10% more water and 1.5% more inorganic N from direct precipitation than did other areas of the watershed. The use of geostatistical plots to analyze wetland surface waters revealed that: (1) within—wetland spatial variability was high on every sampling date except early snowmelt; (2) on a given sampling date, concentration patterns differed for different elements, sometimes substantially; (3) with the exception of NO3—N, the spatial patterns for a given material changed considerably over time; and (4) many of these spatial patterns were interpretable on the basis of observed water flow patterns and wetland ecology. In general, there was a decrease in the concentrations of inorganic solids and most ions, and an increase in Ca++ and chemical oxygen demand with distance from the stream. Overbank fluxes contributed P to the wetland during spring and fall floods, but diluted ambient P concentrations during snowmelt events. During snow—free periods there was a sharp gradient in NO3—N concentrations from a streamside value of °5 mg/L to <0.4 mg/L in wetland areas >45 m from the stream. Measurement of the concentration gradient perpendicular to the stream indicated NO3—N disappearance rates of 6.6 g/100 m of distance during the spring flood. Soil concentrations of mineral matter and P were highest in areas of the wetland closest to the stream; soil concentrations of ammonium and nitrate were spatially disaggregated, and related to levee elevation. At the watershed scale the wetland retained and/or denitrified 15.2% of the total solids, 13.7% of the N, and 14.2% of the P fluxes from the watershed, thus benefitting the water quality of White Clay Lake.
The Decline of the Steller Sea Lion in the Northeast Pacific: Demography, Harvest or Environment?
Authors: Pascual Miguel A. , Adkison Milo D.
Published: April 2006

When apparent declines in population numbers are observed, biologists are confronted with the challenge of determining if such behavior conforms to the expected dynamics of the population or if, on the contrary, the decline reflects some pathological change in the environment that requires management actions. Experimental investigations are often impractical for large free—ranging populations such as fish or large mammals. Consequently, biologists need to get the best possible answer from the limited data available. In this paper we combine deterministic and stochastic modeling, together with statistical estimation techniques, to explore the likelihood of various hypotheses for the decline of Steller sea lions in the North Pacific. Our results show that deterministic transient population behavior, historical pup harvesting, and short—term environmental stochasticity are unlikely causes for the decline. The elimination of these alternatives leads us to agree with previous authors, who suggest that some long—term change in the environment or a novel catastrophe is responsible for the decline.
Demographic Models and Reserve Designs for the California Spotted Owl
Authors: Andersen Mark C. , Mahato Dipak
Published: April 2006

The California Spotted Owl (Strix occidentalis occidentalis), like the more well‐known Northern Spotted Owl (Strix occidentalis caurina), appears to be in decline over at least a part of its geographic range. Two different types of reserve design have been implemented to protect Spotted Owls. The Spotted Owl Habitat Area (SOHA) system uses a fairly large number of small reserves; each SOHA is capable of supporting 1‐3 nesting owl pairs. The Habitat Conservation Area (HCA) plan proposes a smaller number of fairly large reserves, each including 10‐20 active Spotted Owl nests. The HCA reserve design strategy has been incorporated into current conservation planning for the Northern Spotted Owl. The Technical Assessment Team of the California Spotted Owl Assessment project has recommended preserving existing SOHAs within a lightly harvested matrix as an interim policy for conservation of the California Spotted Owl. In this paper we present results from two demographic models of the California Spotted Owl. The first model is based on a simple formulation of a birth–death process; the second model is a somewhat more detailed simulation model. The models are intended to provide a comparison of the SOHA and HCA reserve‐design strategies. We are particularly interested in the ability of the two reserve designs to withstand recurring environmental catastrophes in the form of forest fires. The HCA strategy always leads to longer persistence times than the SOHA strategy. The essential difference between the two strategies appears to lie in the shape of the function that gives the probability of colonization of an empty nest site. These results have several implications for the conservation of California Spotted Owls and for conservation biology in general. (1) Some variant of the HCA reserve design strategy may be preferable to the interim strategy being proposed for conservation of the California Spotted Owl. (2) Simple, parameter‐sparse models like ours can yield results comparable to those of more complex and detailed models. (3) Models that include the effects of catastrophic environmental perturbations have great potential for application in conservation biology.
Thermal Effects of Short Radio Waves on Migrating Birds
Authors: Kleinhaus Shani , Pinshow Berry , Frumkin Ron , Ruppin Raphael , Margaliot Menachem
Published: April 2006

Shortwave broadcast stations emit electromagnetic radiation and may thus affect organisms in their vicinity. On the basis of the design of a planned Voice of America station in the Arava Valley, Israel, and the station's broadcast specifications, we examined its potential as a hazard to migratory and resident birds. We built a computer model to estimate the thermal effects of the station's projected radio‐frequency (RF) radiation on birds within its radiation canopy during horizontal flapping flight, during takeoff, and at rest. Our model indicated that small‐ to medium‐sized birds would not be in thermal danger during flight through the station's RF radiation canopy. Large birds that take off through the station's radiation canopy might incur an increase in their total heat load. Yet, even were no thermoregulatory mechanisms available, the possible rise in body temperature would be within the bird's sustainable range. With heat dissipation mechanisms available, and as long as the body surface: air temperature gradient remained in the bird's favor, even the largest bird would be able to contend with the heat increment imposed during takeoff through the radiation canopy. Large birds landing on antenna structures might become vulnerable to overheating, but it is likely that these birds would depart rather than remain where they are uncomfortably hot. Our approach can be generalized to assess the impacts of shortwave radio stations on wildlife in their surroundings.
Larval Striped Bass Condition in a Drought‐Stricken Estuary: Evaluating Pelagic Food‐Web Limitation
Authors: Bennett William A. , Ostrach David J. , Hinton David E.
Published: April 2006

Estuarine food webs are frequently altered by human interventions, including freshwater diversions, toxic compounds, and introduced species. From 1988 through 1991 we examined the external morphological and internal histopathologic condition of larval striped bass (Morone saxatilis) to evaluate the potential importance of starvation to fish recruitment in the San Francisco Bay estuary. During a recent drought (1987‐1992), fish populations declined markedly, concurrent with dramatic reductions in phytoplankton and zooplankton food for larval fishes. Such patterns suggest pelagic food is limited during times of low freshwater input; therefore, larval starvation may limit recruitment. However, toxic compounds in agricultural runoff are also less diluted in low‐outflow years, enhancing their potential impact. Histopathology enabled us to identify their possible effects. In the laboratory, indices of larval morphology and eye and liver tissue condition reflected starvation after 2 d of food deprivation. From 1988 through 1991 >90% of 980 field‐caught specimens were classified morphologically as feeding larvae. Histopathological evaluation indicated that all field‐caught specimens (N = 500) had food in their guts and lacked tissue alterations consistent with starvation. However, liver alterations consistent with toxic exposure were seen in 26‐30% of the field‐caught larvae from 1988 through 1990, dropping to 15% in 1991. While our findings implicate toxic exposure as a factor in the relationship between low freshwater input and poor year‐class success of striped bass, reductions of toxic runoff and improvement in larval liver condition in 1991 did not improve larval survival. This suggests the potentially greater importance of interactions with food limitation and predation as well as the futility of pursuing single‐factor explanations for recruitment failure. The potential obfuscation of food limitation by toxic exposure also indicates the need for interdisciplinary approaches to distinguishing anthropogenic intervention from estuarine food‐web processes.
Interactions of Anglers and Walleyes in Escanaba Lake, Wisconsin
Authors: Carpenter Stephen R. , Munoz-Del-Rio Alejandro , Newman Steven , Rasmussen Paul W. , Johnson Brett M.
Published: April 2006

Interactions of anglers and walleyes (Stizostedion vitreum vitreum) were analyzed by fitting difference equations to a 33—yr time series from Escanaba Lake, Wisconsin. Fish population dynamics were density—dependent, and harvest by anglers followed a sigmoid functional response. The deterministic form of the model was stable and suggested that the fishery could withstand relatively high exploitation rates. The stochastic form of the model compared management strategies using the probabilities of increased or decreased fish and angler populations and the probability that fish populations will fall below a threshold level. These calculations exposed high risks associated with management strategies based on deterministic, equilibrium equations. The probabilities of sustaining both the fish stock and angler effort increase if harvest rates are reduced below the optimum derived from deterministic models. Consideration of angler dynamics reduced the prediction error of fish stock forecasts and substantially altered risk assessments and management recommendations. If angler dynamics were ignored, the optimal exploitation rate and the risk of overfishing would be overestimated. Lake sport fishery assessments can be improved by coupling models of fish dynamics at the scale of individual lakes with angler models at the larger scale of lake districts.
Population Dynamics of a Reintroduced Asiatic Wild Ass (Equus Hemionus) Herd
Authors: Saltz David , Rubenstein Daniel I.
Published: April 2006

Reintroduction is the release of animals into an area where they were extirpated or have significantly declined. Little is known about the factors that determine the success of failure of ungulate reintroduction. We studied the dynamics of a reintroduced Asiatic wild ass (Equus hemionus) population for 10 yr (1983‐1993) following the first successful release into the wild. A total of 14 adult females and 14 adult males were released into a nature reserve in the Negev Desert of southern Israel. Over this 10‐yr span the female population has grown to only 16 adults. Reproductive success of reintroduced females was low in the first 5 yr following release (0.0‐0.8 foals·female‐1·yr‐1), but increased to 0.5‐1.0 foals·female‐1·yr‐1 in the last 5 yr. Reproductive success of wild‐born females ≥3 yr old was higher than that of reintroduced females of similar ages, and ranged from 0.5‐1.0 foals·female·‐1yr‐1. Our study and data from the E. hemionus studbook suggest that young nonprimiparous females produced primarily males, while primiparous and old females produced primarily females. We attribute the low reproductive success following reintroduction to the stress caused by capture, transport, and release procedures; we consider the age‐dependent progeny sex ratio within the framework of Trivers and Willard's (1973) maternal allocation hypothesis. We conclude that the slow growth of the female population was due to: (a) low reproductive success of females in the early years following reintroduction, and (b) a male‐skewed progeny sex ratio among prime‐aged reintroduced females. A simple stochastic Leslie matrix model suggests that high survival and improved reproductive success of reintroduced females at later stages of the study, and the reproductive success of wild‐born females, make the population relatively unsusceptible to extinction from random demographic processes. In‐depth knowledge of the dynamics of reintroduced populations is vital for the correct assessment of their viability. We offer suggestions for increasing the efficacy of future wild ass reintroductions.
Riparian Silvicultural System Design and Assessment in the Pacific Northwest Cascade Mountains, USA
Authors: Berg Dean Rae
Published: April 2006

Active management of riparian zones can be economically as well as ecologically beneficial. Restoration of riparian forests is simulated with forest growth models. Logs were generated using the model to be of sufficient size to resist annual floods in salmon habitat streams on the west side of the Pacific Northwest Cascade mountains. The economic feasibility is reported at real interest rates. Economic viability depends on the initial volume removed, costs of regeneration and monitoring, volume of thinnings, and interest rate. Harvest operations allow for the restoration of forest structure and composition that is beneficial for salmonid habitat in areas where the primary forest has been replaced with early seral hardwood species and fiercely competitive shrubs. This silvicultural system restores natural functions of riparian forests of watersheds in the Pacific Northwest.
Do Barren Zones and Pollen Traps Reduce Gene Escape From Transgenic Crops?
Authors: Morris William F. , Kareiva Peter M. , Raymer Paul L.
Published: April 2006

As genetically engineered crop varieties near widespread cultivation, both agronomic and environmental concerns mandate the development of effective strategies for isolating transgenic varieties from related non—transgenic varieties or cross—fertile weeds. We present the results of the first field experiment designed to test the effectiveness of two containment strategies that are commonly used in field trials of transgenic crops: (1) an isolation zone devoid of vegetation to discourage emigration of insect pollinators from transgenic plots; and (2) trap crops (non—transgenic varieties of the same crop planted adjacent to the transgenic plot that can "cleanse" emigrating pollinators of transgenic pollen). In conjunction with field trials of genetically engineered canola (Brassica napus) conducted by Calgene, Inc., in California and Georgia, we varied both the width of the barren zone and the presence or absence of a trap crop, and measured the effects on gene escape. Escape was easily detected since the genetic construct inserted into the transgenic canola contained a gene that rendered seedlings resistant to the normally lethal antibiotic kanamycin. Our results suggest that barren zones 4—8 m in width may actually increase seed contamination over what would be expected if the intervening ground were instead planted entirely with a trap crop. When trap crops occupied a limited portion of the isolation zone separating transgenic and non—transgenic varieties, the effectiveness of the trap depended on the width of the isolation zone: they reduced gene escape when the two varieties were separated by 8 m, but increased escape across a 4—m isolation zone. We conclude that, for the relatively short isolation distances we examined, the most effective strategy for reducing the escape of transgenic pollen is to devote the entire region between transgenic and non—transgenic varieties to a trap crop.
Plant Species Diversity in Natural and Managed Forests of the Pacific Northwest
Authors: Halpern Charles B. , Spies Thomas A.
Published: April 2006

With the exception of the tropics, nowhere has the relationship between resource management and conservation of biological diversity been more controversial than in the Pacific Northwest region of the United States. Widespread loss and fragmentation of old—growth ecosystems have stimulated critical review and revision of existing forest management policies. However, studies of the consequences of forest management for plant species diversity are sorely lacking. We present data from permanent—plot and chronosequence studies in managed and unmanaged forests of western Oregon and Washington to describe the early responses of understory communities to forest harvest, and to suggest how post—harvest practices that alter natural successional processes may influence long term patterns of diversity and species occurrence. Permanent—plot studies of early succession in old—growth Pseudotsuga forests suggest that changes in understory diversity are fairly short—lived following clear—cut logging and slash burning. Populations of most vascular plant species recover to original levels prior to canopy closure. However, diversity may remain depressed for more than two decades on severely burned sites, and some species may experience local extinction. Evidence of the effects of post—harvest practices on vascular plant diversity is limited by an absence of community—level studies in older, managed forests. Chronosequence studies of natural forest stands indicate that, following canopy closure, vascular plant species diversity tends to increase with time, peaking in old growth. Few understory species are restricted to, or absent from, any stage of stand development (i.e., young, mature, or old growth). However, many species differ significantly in their abundance among stages. A majority of these showed greatest abundance in old growth. Changes in levels of resources (increased shade), changes in the spatial variability of resources and environments (increased horizontal and vertical heterogeneity), and species' sensitivity to fire and slow rates of reestablishment/growth may drive these trends during natural stand development. Silvicultural prescriptions that maintain or foster spatial and temporal diversity of resources and environments will be most effective in maintaining plant species diversity. Practices associated with intensive, short—rotation plantation forestry, that preclude or delay the development of old—growth attributes, may result in long—term loss of diversity. Ultimately, it may be necessary to manage some stands on long rotations (150—300 yr) to maintain understory species that require long periods to recover from disturbance.
Effects of Carbon, Fertilizer, and Drought on Foliar Chemistry of Tree Species in Interior Alaska
Authors: Yarie John , Van Cleve Keith
Published: April 2006

Changes in foliar chemistry resulting from changes in forest‐floor and mineral‐soil moisture availability, forest‐floor microbial energy supply, and nitrogen availability were investigated across the successional sequences in both upland and floodplain landscape positions. Three amendments, sugar, sawdust, and nitrogen fertilizer (NH4NO3) were applied to a series of three upland and four floodplain successional sites. The sugar and sawdust treatments were designed to increase the carbon: nitrogen ratio (C/N) of the forest floor to values typical of black spruce sites (C/N = 50). The nitrogen fertilizer treatment was designed to equal estimated yearly N mineralization in an attempt to double available nitrogen in the forest floor. A moisture exclusion treatment was designed to remove all summer rainfall from the treatment plots. Foliar phosphorus concentrations were higher in the upland sites than on the floodplain. No consistent differences were reported among successional stages within a landscape unit. The effect of either sugar or sawdust treatment was to decrease foliar phosphorus concentrations. Sugar produced more significant differences than did sawdust. Sugar treatments decreased foliar nitrogen in all tree species except for white spruce, while fertilizer tended to increase foliar nitrogen. In the second year following treatment there was not an increase in foliar nitrogen concentration resulting from fertilizer treatment.