bluuebunny/crossref_metadata_2025 huggingface dataset:
Religion and Authority in a Korekore Community
Authors: Bourdillon M. F. C.
Published: April 2006

Opening Paragraph

In her lucid and persuasive Henry Myers Lecture on ‘The power of rights’ (Man, 1977), Professor La Fontaine argues that since the Gisu themselves cite transition from one status to another as the purpose of their initiation rites, this transformation cannot logically explain them. Taking up Maurice Bloch's idea that religion is concerned with inequality and hierarchy (1974; 1977), La Fontaine argues convincingly that the explanation of Gisu initiation rites lies in their functions of validating traditional knowledge and of maintaining traditional authority. The relationship between religion and political power had been noticed before but it had not previously been applied to the field of rites of passage nor had the mechanism of the supportive role of traditional knowledge been so clearly analysed.
Sacrifice and Social Structure among the Kuranko
Authors: Jackson Michael
Published: April 2006

Sacrifice and Divination

The Kuranko term for sacrifice issarake(from the Arabicsadaqa). Any gift, offering or material object over which invocations to spirits are made is a sacrifice.Sarakethus includes offerings made to the three major categories of spirit: (1)AlaorAltala(God), (2)BəmbanuorFɔl' mɔryonu(‘Ancestors’ and ‘First/original people’ respectively), (3)Njεnnenu(Spirits of the wild or djinn). Sacrifice also includes material objects (medicines and fetishes) which are prayed over.
Some contradictions in missionizing
Authors: Wyllie R. W.
Published: April 2006

Opening Paragraph

In a recent paper Beidelman (1974: 235—249) has argued cogently for a more systematic study of missions on the part of students of colonial societies and has indicated, in a preliminary fashion, several analytical themes which might provide a general theoretical framework for such a study. The present paper is not offered as a comment on Beidelman's overall scheme but has a somewhat narrower focus, addressing itself to two aspects of missionary study mentioned by that author: the contradictions in missionizing and the nature of colonial society. Given the preliminary nature and schematic intent of Beidelman's paper it is understandable that the connections between these aspects are not made explicit. One of our tasks, therefore, will be to show how the contradictions revealed in the practice of missionizing relate to the kind of society in which missions typically operate. Like Beidelman, we illustrate our argument with references to the work of an African mission, in this case the Wesleyan Methodist mission in southern Ghana (formerly the Gold Coast).
Sexualité et Continence Prénuptiale chez les Toucouleur du Sénégal
Authors: Wane Yaya
Published: April 2006

Opening Paragraph

L'une des caractéristiques fondamentales de la société toucouleur traditionnelle est, assurément, la chasteté imposée à l'individu pendant une période prolongée de son existence. Car il apparaît que la sexualité, hormis dans le cadre pour ainsi dire exdusif du mariage, se présente généralement en termes de prohibition formelle. Peut-être convient-il de voir en cela l'effet naturel de la très stricte obédience islamique toucouleur, aux termes de laquelle tout contact sexuel illicite – done extra-conjugal – est une souillure si grave, que son expiation appelle l'Enfer et la carbonisation littérale du pécheur.
The History of Trade at Ikom, Eastern Nigeria
Authors: Harris Rosemary
Published: April 2006

Opening Paragraph

Ikom, on the Cross River and with a total population of just over 7,000 in 1953, lies near the boundary between Nigeria and southern Cameroons. It has been commercially important in recent years, as was indicated, for example, by the presence there in 1953 (the date of the last fairly reliable census) of over 1,500 Ibo. But the Ibo are newcomers, and this paper is concerned with examining earlier patterns of trade as they had developed down to the nineteen-twenties. More recently the people of Ikom have derived their prosperity from the exploitation of their soil, which is eminently suitable for producing cocoa. According to a visiting soil scientist in the 1960s, there are in the locality 140 square miles of suitable cocoa land, which in fact is so plentiful that although two-thirds of it was still held in a forest reserve there was in 1966 no public pressure to have any portion released for agriculture. The affluence based on cocoa is, however, recent; the traditional path to prosperity and influence was through participation in trade, especially trade with Mamfe to the east and with Calabar on the coast, principally along the Cross River.
Boys' circumcision and girls' puberty rites among the Swahili of Mafia Island, Tanzania
Authors: Caplan A. P.
Published: April 2006

Opening Paragraph

In the north of Mafia Island, the rites surrounding the circumcision of boys and the first menstruation of girls are no longer, if indeed they ever were, universally performed. This article attempts to explain this situation, and in so doing, draws on some of Turner's work on symbolism. In particular, his distinction between different levels of meaning expressed by symbols—the exegetical, the operational and the positional (1962)—is followed in a discussion of the political implications of performance or rejection of the rites.
Myth, Motive, and Selection in Southern African Rock Art
Authors: Vinnicombe Patricia
Published: April 2006

Opening Paragraph

Recent publications on the rock art of Africa have again focused attention on the tremendous wealth of painted and engraved sites in that continent (Brentjes, 1969; Cooke, 1969; Lee and Woodhouse, 1970; Rudner, 1970). At the same time, however, it is made all too clear that the collection of data is largely unsystematic and subjective and, because of the incomplete nature of the evidence, valid analysis or comparison is difficult. Small wonder, then, that there is such a diversity of often conflicting views on the significance of the art (Vinnicombe, 1972).
A Nineteenth-Century Ruhr in Central Africa
Authors: Warnier Jean-Pierre , Fowler Ian
Published: April 2006

Opening Paragraph

Over two hundred thousand cubic metres of slag and smelting debris, at least two hundred and seventy smelting sites, more than seven hundred recorded kaolin pits for building and lining furnaces, and probably half as many again not visited by us—these are a few figures that establish three villages of the Ndop Plain, in the highlands of Western Cameroon, as a nineteenth-century Ruhr in Central Africa. To this day, this all Sub-Saharan African record leaves Meroe, ‘the Birmingham of Africa’ well behind. Perhaps the record remains unbroken, however, just because scholars interested in African iron industries seem to have been unconcerned with the overall output of these industries.
Production, income and expenditure patterns of Yoruba smallholders
Authors: Flinn J. C. , Zuckerman Paul S.
Published: April 2006

Introduction

There is a growing acceptance of the position that low resource farmers act and make decisions in a manner consistent with economic ‘rationality’ (Helleiner, 1975; Schultz, 1964). As a result, agriculturalists are becoming increasingly concerned to design technological innovations which are consistent with the needs and means of low resource farmers (CIMMYT, 1980; Zandstra et at., 1980). In particular, constraints due to the quantity or intensity with which a farmer can cultivate his land (land and labour scarcity), his low asset level and access to credit, other demands of the household on the farm-family resources, and the uncertain environment (both natural and man-made) within which the smallholder operates, all influence his capacity and willingness to adopt what are thought to be ‘improved’ agricultural technologies (Clark and Haswell, 1970; Reynolds, 1975; Wharton, 1968).
Nyoro symbolism: the ethnographic record
Authors: Needham Rodney
Published: April 2006

Opening Paragraph

This paper is an attempt to establish certain contested facts about Nyoro symbolism. The need to do so results, in brief, from the following circumstances. Eight years ago I published an analysis of the significance of right and left in Nyoro symbolic classification (Needham 1967). John Beattie, who had done field research among the Nyoro, then brought out an article in which he contended that I had seriously misrepresented the nature of Nyoro representations of their own culture and history, ‘even in so far as these can be understood from readily available published sources’. His main concern in his critique, consequently, was ‘to set the Nyoro ethnographic record straight’ (Beattie 1968: 413).
A Summary-Report on the Oral Traditions of Yoruba Musicians
Authors: Thieme Darius L.
Published: April 2006

Opening Paragraph

This paper reports briefly on some oral traditions collected from Yoruba musicians in western Nigeria in 1964-6. These relate mainly to the origins of their musical instruments. The research sought to answer these questions: Do Yoruba musicians have an established body of traditional beliefs with respect to their instruments? If so, how can these beliefs best be collected for collation and comparative study?
Religious Courts, Community, and Ethnicity among the Swahili Of Mombasa: An Historical Study of Social Boundaries
Authors: Swartz Marc J.
Published: April 2006

Opening Paragraph

The purpose of this paper is to examine the role of Koranic courts in asserting and maintaining the boundaries of a social group, the Swahili, in Mombasa, Kenya. It is a basic thesis here that these Muslim tribunals, called Kadhis courts, have played an important role in maintaining the distinctiveness of the Swahili throughout much of their long history. There are other important elements in the boundary processes that separate the Swahili from their neighbors and several of these will be noted here, but primary attention is focused on the workings of the courts. Through controlling these courts the Swahili community is able to have a direct influence on some of the areas of life its members look upon as central to the community's proper functioning. The courts now deal almost exclusively with domestic affairs and, although they are available to all Muslims, their use is optional and anyone who wishes to may use the secular courts instead. Because of the optional status of the courts, their use is itself an assertion of group membership.
Home-Town: A Study of an Urban Centre in Southern Ghana
Authors: Middleton John
Published: April 2006

The Town and its Setting

Southern Ghana has for centuries been a region marked by continuous movement of population, both of groups and individuals; by ever-changing forms of social stratification; by urban centres of various kinds and sizes; and by trade with the outside world. Yet tradition and ‘custom’ are of great importance for the people. And despite marked economic and political development, kingship, matrilineal descent, and urbanism have remained central in most of the area in both national and local social systems.
De la forme culturelle au vecu des troubles psychiques en Afrique
Authors: Corin Ellen , Bibeau Gilles
Published: April 2006

Une des caractéristiques fondamentales de la vaste remise en cause que connaissent les valeurs de la culture occidentale est sans contredit le fait qu'elle a dépassé une réflexion sur elle-même et qu'elle va puiser ses éléments de renouvellement dans les autres cultures. C'est dans ce cadre que la médecine occidentale, confrontée à d'autres traditions médicales, s'interroge sur ses postulats fondamentaux et sur leur valeur universelle. Cette interrogation est particulièrement aigüe dans le domaine de la psychiatrie: contestée violemment par ceux-là même qui la pratiquent, elle est à la recherche de nouvelles coordonnées et de nouveaux modes de thérapie qui lui donnent prise sur un objet qu'elle a de plus en plus de peine à définir. Au sein de ces tâtonnements naissent une série de tentatives nouvelles de traitement dont certains pensent trouver un correspondant dans d'autres formes de psychiatrie, déjà enracinées dans toute une tradition. Ainsi, différents cliniciens sentent actuellement la nécessité de se laisser interpeler par la façon dont les sociétés africaines appréhendent et organisent le domaine des maladies mentales et de leur traitement.
‘Three's a crowd’: knowledge, ignorance and power in the context of urban agriculture in Rwanda
Authors: Pottier Johan
Published: April 2006

Opening Paragraph

The themes of knowledge and ignorance are explored in this article, as is their dialectic, in the light of the continuing failure of development efforts based on top-down procedures. My specific aim is to deliver a statement about the intricate relationship between knowledge, ignorance and power in the context of a Rwandan development project. I will demonstrate how ignorance is generated through agricultural extension and will argue that agronomic services rely on power structures reminiscent of the ‘old’ premise of social inequality (Maquet, 1961; for a summary of the debate on social inequality in Rwanda, see Reyntjens, 1985: 21–30). My concern will be to assess whether the project-induced creation of ignorance—such as the distorted portrayal of practices outside the project area—leads to the displacement of local knowledge and the adoption of new methods.
Mahdist faith and the legitimation of popular revolt in western Sudan
Authors: Kapteijns Lidwien
Published: April 2006

Opening Paragraph

This article is based on a wider study of the history of the western Sudan, in particular the border area between the historical sultanates of Dar Fur and Wadai (Kapteijns, 1985). The period under discussion is 1882–1930, from the successful struggle against foreign domination led by the Sudanese Mahdi to the firm establishment of British colonial rule in the western Sudan. The theme which this article explores for this area and period is that of popular revolt and Islamic (specifically Mahdist) ideology. The source materials for this study consist of Arabic correspondence from the Mahdist archives, oral data and British and French colonial records.
Swahili stratification and tourism in Malindi Old Town, Kenya
Authors: Peake Robert
Published: April 2006

The Leisure Class

At the turn of the century Veblen (1899) wrote on the socio-economic base of the leisure class. He suggested that, in addition to the ‘bourgeois’ and working classes identified in the nineteenth century, there existed an upper strata which was more than a mere anachronistic remnant of the preindustrial aristocracy, but was in fact reproduced by the developed industrial society.
Legacies of the Past? The Results of the 1980 Election in Midlands Province, Zimbabwe
Authors: Rich Tony
Published: April 2006

Opening Paragraph

Western journalists and other commentators offered two contrasting explanations for the results of the 1980 elections in Zimbabwe. The defeat of Bishop Abel Muzorewa's United African National Council (UANC) by the guerrilla parties was explained in terms of immediate and short-term intimidation. On the other hand, the victory of Robert Mugabe's Zimbabwe African National Union (Patriotic Front) (ZANU(PF)) over Joshua Nkomo's Patriotic Front was explained in terms of primordial history. The Shona and the Ndebele, it was held, were divided by 'traditional' tribal history–and in the elections the majority Shona voted for Mugabe and the minority Ndebele voted for Nkomo.
Enriching the landscape: social history and the management of transition ecology in the forest–savanna mosaic of the Republic of Guinea
Authors: Fairhead James , Leach Melissa
Published: April 2006

The mosaic of forest and savanna vegetation found along the northern margin of West Africa's moist forest zone has generally been understood in policy circles as a degraded and degrading forest landscape, following savannisation by its farming populations. Some ecologists have suggested that the vegetation mosaic may, however, be more stable, determined by soil differences, and others still that forest may be encroaching on savanna as a result of long-term climatic rehumidification. This article presents historical evidence from Kissidougou which shows that, contrary to scientific and policy orthodoxy there, forest areas have been increasing at the expense of savanna in recent times. The article outlines the local agro-ecological practices which have been enriching the landscape, and examines how the observed course of vegetation change this century can be accounted for in the articulation of these practices with political, economic, demographic and climatic changes. A retheorisation of ecology in the forest–savanna mosaic is offered which, in drawing on non-equilibrium dynamics, offers a better framework for understanding people's impact on forest–savanna ecology.
Recent advances in storage and flooding theory
Authors: Gani J.
Published: April 2006

The theory of storage processes, originally formulated by Moran [1] in 1954, has developed in the past fourteen years into a minor subfield of Applied Probability, closely allied to queueing theory. While dam models with discrete inputs are analogous to queueing processes, the essentially continuous nature of water inflows has distinguished generalized storage processes from queues. Indeed, some of the most complex of storage problems have arisen in the case of continuous flows.
Trends and fluctuations in species abundance and richness in Mediterranean annual pastures
Authors: Peco B. , Espigares T. , Levassor C.
Published: April 2006

Abstract. Floristic data collected from permanent plots during 14 consecutive years are used to model the frequency of the 62 most abundant species in relation to post‐ploughing succession, topography and rainfall in annual Mediterranean grasslands located in a Quercus rotundifolia dehesa. The interannual dynamics of species richness are also analysed. From 1980 to 1993, presence/absence data of grassland species were noted in five 20 cm X 20 cm permanent quadrats placed at random in 1980 in 14 permanent plots on a south‐facing slope along the topographic gradient. Weekly autumn rainfall data over the 14 years were analysed using a profile attributes index and Hybrid Multidimensional Scaling to arrange the years according to their autumn rainfall pattern. Generalized Linear Models were used to fit the species richness and species frequency according to topographic position, age since the last ploughing episode, total rainfall in the growing season and autumn rainfall pattern using a forward stepwise procedure. The richness model includes all of these variables, and reveals a relatively high goodness‐of‐fit (71 %). The fact that the meteorological factors play a key role in modelling richness forces us to include them if we wish to use richness as an indicator of the degree of disturbance in these highly fluctuating annual pastures. Models of species dynamics show that although roughly 33 % of the species have a successional behaviour, the majority are more dependent on temporal heterogeneity associated with rainfall or spatial heterogeneity linked to the topographic gradient.
Pollen and gene flow in fragmented habitats
Authors: Kwak Manja M. , Velterop Odilia , van Andel Jelte
Published: April 2006

Abstract. Habitat fragmentation affects both plants and pollinators. Habitat fragmentation leads to changes in species richness, population number and size, density, and shape, thus to changes in the spatial arrangement of flowers. These changes influence the amount of food for flower‐visiting insects and the quantity and quality of pollinations.

Seed set in small populations is often reduced and genetic variation is expected but not always found to be low. The majority of studies show that low flower densities have reduced pollination success and higher inbreeding. Density effects are stronger than size effects.

Most studies concluded that species richness in flower‐visiting insects is directly related to richness in plant species. However, the consequences of low insect species richness for pollination are not always clear, depending on the studied pollinator‐plant relationship. The effects of the presence of simultaneously flowering species are highly dependent on the circumstances and may range from competition to facilitation. Other flowering plant species may play a role as stepping stones or corridor in the connection between populations. In the absence of stepping stones even short distances between populations act as strong barriers for gene flow.

We illustrate the present review paper with own data collected for three plant species, rare in The Netherlands: Phyteuma spicatum ssp. nigrum (Campanulaceae), Salvia pratensis (Labiatae) and Scabiosa columbaria (Dipsacaceae). The species differ in their breeding systems and in the assemblage of visitor species. Data are shown on the effects of population size on species richness with consequences for seed set. Effects of flower density and isolation on pollen exchange are given. Since plant reproduction depends on the behaviour of individual insects and not on the overall behaviour of the species, the examples all point to individual insects and extrapolate to effects at the species level.
A View of NAPAP from North of the Border
Authors: Schindler D. W.
Published: April 2006

Despite widespread political interference with programs and confusion of science and policy, the NAPAP program has produced a number of sound, if not outstanding, publications documenting the effects of acidic deposition. NAPAP's outstanding strengths in aquatic science are in paleoecology and spatial surveys of chemistry. NAPAP has severe shortcomings in documentation of temporal trends, in deducing biological responses to acidification by organisms other than fish, in considering the effects of nitrogen deposition, and in considering results from countries other than the USA. Summaries of the NAPAP program in 1987 and 1990 underrepresent the extent of damage caused by acidification, as documented elsewhere in NAPAP's publications and by the peer—reviewed literature at large. Overall, it represents a mediocre return for a large amount of investment, and is a poor model for future large, multidisciplinary science projects.
Herbivory and Its Consequences
Authors: Dyer M. I. , Turner C. L. , Seastedt T. R.
Published: April 2006

We argue that herbivores often induce nonlinear or biphasic growth and development in plants. Collectively these individual responses translate into a system—level optimization curve wherein at low levels of herbivory overall community responses show increases in production potential, whereas extreme herbivory causes extreme reduction in productivity. The transition between these two states defines a point of optimal herbivory in respect to C and N processes.We present four case examples from the literature demonstrating such nonlinear responses, suggesting a widespread existence for this herbivore—plant phenomenon. The nonlinear responses appear to demonstrate temporal and spatial scale dependencies.
Grazing and Plant Performance
Authors: Trlica M. J. , Rittenhouse L. R.
Published: April 2006

Grazing is more than just defoliation of plants. The impact of herbivory affects ecosystem structure and function, both above and below ground. Ultimately, effects of herbivory are expressed to varying degrees at many levels of the ecosystem. Herbivory has been shown to affect plant physiology, morphology, and genetics. Plants have evolved many ways to avoid or tolerate herbivory. Whether plant overcompensate, equally compensate, or undercompensate to herbivory depends on pre— and post—harvest conditions of the plants and their environment. To be important to the manager, the magnitude of compensation must be greater than the inherent "noise" in the system. Natural resources managers use scientific information about herbivory to reduce ambiguity in decision—making in an environment of uncertainty. If an ecological response like compensation is to have practical application for the manager, the meaningful effects must occur on time and spatial scales that the manager can respond to with available resources.
Management of Weed Seed Banks with Microorganisms
Authors: Kremer Robert J.
Published: April 2006

Successful weed management in agroecosystems centers on manipulating the weed seed bank in soil, the source of annual weed infestations. Despite advances in aboveground weed control and decreases in the production of new seed, weed infestations continue to be generated from a small portion of the seed bank that persists as a result of dormancy and resistance to decay. Depletion of the persistent seeds using soil—applied chemicals to stimulate germination has received much attention while the search for microorganisms selective for seed decay has been largely overlooked. This paper provides an overview of the effects of microorganisms on weed seed viability relative to seed bank depletion, and how this information can be applied to weed management. Limited studies indicate that microorganisms associated with weed seeds can contribute to seed bank depletion through attraction to seeds by chemotaxis, rapid colonization of the spermosphere and production of enzymes and/or phytotoxins to kill seeds prior to germination. It is recognized, however, that the best opportunity for success will be through integration of selected microorganisms or microbial products with other approaches including germination stimulation, application of low rates of herbicides, manipulation of the soil environment (e.g., solarization), and biological control agents for effectively eliminating dormant, persistent seeds from soil. To achieve success, more in—depth research on microbial factors affecting weed seed banks is required.
A Spatial Simulation Model of Hydrology and Vegetation Dynamics in Semi‐Permanent Prairie Wetlands
Authors: Poiani Karen A. , Johnson W. Cater
Published: April 2006

The objective of this study was to construct a spatial simulation model of the vegetation dynamics in semi—permanent prairie wetlands. A hydrologic submodel estimated water levels based on precipitation, runoff, and potential evapotranspiration. A vegetation submodel calculated the amount and distribution of emergent cover and open water using a geographic information system. The response of vegetation to water—level changes was based on seed bank composition, seedling recruitment and establishment, and plant survivorship. The model was developed and tested using data from the Cottonwood Lake study site in North Dakota. Data from semi—permanent wetland P1 were used to calibrate the model. Data from a second wetland, P4, were used to evaluate model performance. Simulation results were compared with actual water data from 1797 through 1989. Test results showed that differences between calculated and observed water levels were within 10 cm 75% of the time. Open water over the past decade ranged from 0 to 7% in wetland P4 and from 0 to 8% in submodel simulations. Several model parameters including evapotranspiration and timing of seedling germination could be improved with more complex techniques or relatively minor adjustments. Despite these differences the model adequately represented vegetation dynamics of prairie wetlands and can be used to examine wetland response to natural or human—induced climate change.
The Role of Ecology in Biological Conservation
Authors: Brussard Peter F.
Published: April 2006

The emerging science of conservation biology represents an intersection of elements of ecology, genetics, biogeography, and many traditional applied disciplines such as wildlife management and forestry. Its major concern is providing a valid scientific basis for actions that will slow or stop the accelerating loss of biological diversity worldwide. Ecology's major contributions to conservation biology so far include the equilibrium theory of island biogeography and the theoretical relationship between population size and persistence time. In the future ecologists can contribute their skills to conservation biology in numerous ways; I suggest three in particular. These are investigating the autecology and natural history of rare species, testing hypotheses concerning population viability with carefully designed laboratory and field experiments, and working to establish and implement a national policy for the protection of biological diversity on United States public lands.
Conservation Genetics: Techniques and Fundamentals
Authors: Hedrick Philip W. , Miller Philip S.
Published: April 2006

Conservation genetics utilizes the tools and concepts of genetics and applies them to problems in conservation biology. For example, molecular genetic techniques, such as protein electrophoresis, and analysis of mitochondrial DNA and highly variable nuclear genes (including DNA fingerprinting), have been important in documenting the extent and pattern of genetic variation in endangered species. We review these techniques and their advantages and disadvantages, and give examples of their application to endangered species. For captive animal populations, pedigree analysis has become the basic approach to evaluate breeding priority of particular individuals. Several pedigree analysis techniques are commonly used, but peeling and gene dropping give the most information. We compared these techniques and illustrate their value with applications to the Guam Rail, Przewalski's horse, and other endangered captive animals. The rationale for much conservation genetic interpretation is base in evolutionary genetics. We discuss the avoidance of inbreeding depression and the maintenance of genetic variation–both primary conservation genetic goals–from this perspective. In addition, we suggest aspects of these factors that deserve greater attention in their overall application to conservation planning. Finally, we briefly mention three evolutionary topics–the relationship of heterozygosity and fitness, population bottlenecks, and outbreeding depression–that have implications for conservation genetics. Although simple interpretation in these areas is appealing, we feel that because they are only generally understood and often quite controversial, their application to endangered—species management should be carefully evaluated and monitored.
Remote Estimation of Crown Size, Stand Density, and Biomass on the Oregon Transect
Authors: Wu Yecheng , Strahler Alan H.
Published: April 2006

In this paper, we invert a canopy reflectance model using multispectral satellite data in order to estimate remotely the parameters of crown size, tree count density, cover, foliage biomass, and total standing biomass for nine coniferous forest stands on a transect of western and central Oregon (USA). Issues involved in the inversion of the model are topographic correction, component signature estimation, spatial pattern analysis, and direct biomass estimation. Retrieved parameters correlate well with observed values from ground measurements of the test sites. The model inversion technique is a useful tool for mapping and timber inventory of forests at large scales.
Bird Habitat Relationships in Natural and Managed Forests in the West Cascades of Oregon
Authors: Hansen Andrew J. , McComb William C. , Vega Robyn , Raphael Martin G. , Hunter Matthew
Published: April 2006

Ecologists have advocated retaining various densities of canopy trees in harvest units in Pacific Northwest forests. In contrast to clear‐cutting, this practice may better emulate the patterns of disturbance and structural complexity typical of natural forests in the region. Several ecological attributes, including vertebrate habitat diversity, are thought to be associated with stands of complex structure. The goal of this study was to determine bird abundance in canopy retention sites relative to other common stand types in the Pacific Northwest and to develop habitat functions for extrapolating bird abundance across current and future landscapes. We used data from five previous studies in the west central Cascades of Oregon to compare bird abundance and to develop habitat functions for forest birds across a wide range of natural and managed stand structures and ages. The 67 stands included clearcuts, retention sites, young closed‐canopy plantations, mature stands, and old‐growth stands. ANOVA revealed that 18 of the 23 species included in the analysis differed significantly in abundance among the stand types, with some species being primarily associated with each of the stand types. The habitat variables used to build habitat functions included tree density by size class, mean tree diameter, and variation in tree diameter. Linear, polynomial, and various nonlinear regression models were evaluated for each bird species. Significant habitat functions were generated for 17 of the 23 bird species. The analyses identified four habitat‐use guilds among the 17 bird species: open‐canopy; open‐canopy with dispersed large trees; structurally complex closed‐canopy; and structurally simple closed‐canopy guilds. This study is the first in the Pacific Northwest to compare bird abundances across natural stands, traditionally managed plantations, and stands managed under ecological forestry approaches. The results suggested that canopy tree retention benefits many, but not all, of the bird species we studied, Moreover, the nonlinear responses of bird abundance revealed thresholds in tree density at which bird abundance changed dramatically. Knowledge of these thresholds allow managers to design stands for specific biodiversity objectives. The habitat functions presented here can be used to predict bird abundance based on habitat measurements derived from field data, remotely sensed data, or output from computer models of forest dynamics.
Desert Plant Communities in Human‐Made Patches‐‐Implications for Management
Authors: Boeken Bertrand , Shachak Moshe
Published: April 2006

We measured productivity and diversity of annual plant communities in human—made pits and mounds (20 ° 30 ° 100 cm) in the Northern Negev of Israel. We differentiated the species according to propagule size, dispersal mode, and geographical distribution in Israel. Our results in 28 experimental units containing a pit, a mound, and a portion of the undisturbed surrounding "matrix" showed that species richness, total plant density, and biomass yield were higher in the pits and mounds than in the matrix. Soil moisture at 0—15 cm depth was higher in the pits, but lower in the mounds relative to the matrix. Species with larger propagules (>5 mm) became more abundant, and those with tinyseeds (<1 mm) became less abundant, in the human—made patches relative to the undisturbed matrix. Wind—dispersed species and those with secondary dispersal by runoff were denser in pits and mounds, while short—distance rain dispersers were more abundant in the matrix. "Edge" species, occurring in the study site at the edge of their geographical distribution in Israel, increased more in density, species richness, and biomass than general "core" species, for which the study site is in the center of their distribution. The annual plant community responded to changes in three environmental factors: (1) microtopographic structure from flat surface to mounds or pits, which function as traps for seeds; (2) soil surface texture from densely packed to loose soil in pits and mounds, which provide suitable sites for larger propagules; (3) soil moisture availability, increasing in the pits but decreasing in the mounds relative to the matrix. The relevance of the study was discussed in relation to (1) combating desertification, (2) sustainable arid land use, and (3) species conservation.
Ecology of Lyme Disease: Habitat Associations of Ticks (Ixodes Scapularis) In a Rural Landscape
Authors: Ostfeld Richard S. , Cepeda Obed M. , Hazler Kirsten R. , Miller Michael C.
Published: April 2006

Human activities often result in the creation of patchy landscapes, which may influence distribution and abundance of some wildlife species and their ectoparasites. Risk of exposure to Lyme disease is a function of the abundance of ticks (Ixodes scapularis, formerly I. dammini), which in turn may be determined by the distribution of key vertebrate hosts within landscapes. We used transect drag sampling and small‐mammal trapping to estimate, respectively, the abundance of host‐seeking and attached ticks in a rural landscape (southeastern New York) consisting of a mosaic of several discrete habitat types. Forested habitat types supported higher densities of host‐seeking ticks than herbaceous or shrub‐dominated habitats. However, in patches of little bluestem grass and gray dogwood shrubs, small mammals had high tick burdens despite low densities of host‐seeking ticks. There was an outbreak of larval ticks limited to oak‐dominated habitats in summer, 1992, which we postulate was related to unusually heavy acorn (mast) production attracting white‐tailed deer and attached adult deer ticks, in autumn 1991. This hypothesis was supported by low densities of larval ticks in oak patches in summer, 1993, following poor mast production the previous autumn. Instead, the 1993 larval peak shifted to maple‐dominated habitats, which may result from intensive use of these patches by deer in nonmast years. The abundance of host‐seeking nymphs was strongly correlated with the abundance of white‐footed mice the prior summer. Both the high tick burdens in little bluestem and dogwood patches, and shifting locations of larval outbreaks, appear to be functions of landscape configuration, especially patch size and juxtaposition.
Ecotone Dynamics and Boundary Determination in the Great Dismal Swamp
Authors: Carter Virginia , Gammon Patricia T. , Garrett Mary Keith
Published: April 2006

Data on hydrogeology, soils, and vegetation collected on four transects across the 48—km wetland—to—upland transition zone of the Great Dismal Swamp of Virginia/North Carolina, USA, were used to analyze changes along the moisture/elevation gradient, to characterize the wetland—upland ecotone, and to select tentative wetland—upland boundaries based on these three parameters. Transition zone vegetation was dominated by three facultative hydrophytes: Acer rubrum, Liquidambar styraciflua, and Nyssa sylvatica. On the basis of ordination performed on consecutive 25—m transect increments, each transect was divided into three zones: wetland, ecotone, and upland. The water table was within the root zone (0—30 cm below the ground surface) an average of 25—100% of the growing season at all well sites in wetland, <25—100% for most well sites in the ecotone, and <25—50% for well sites in upland. Soils were hydric in the wetland and ecotone, and histosols were found only in the wetland zone. Soils were generally nonhydric in the upland zone. Wetland boundaries determined on the basis of each parameter differed; they were within 38 m horizontal distance and 1.1 m vertical distance on the transects where all three boundaries could be determined. These boundaries were relatively close considering the length of the transects, the coarse resolution of the soils and hydrology data, and certain assumptions made during the analysis. On one of the remaining transects, the hydrology and soils boundaries differed by >100 m horizontal distance and 0.4 m vertical distance. Only a vegetation boundary was established on the fourth transect.
Episodic Acidification of Small Streams in the Northeastern United States: Episodic Response Project
Authors: Wigington P. J. , Baker J. P. , DeWalle D. R. , Kretser W. A. , Murdoch P. S. , Simonin H. A. , Van Sickle J. , McDowell M. K. , Peck D. V. , Barchet W. R.
Published: April 2006

The Episodic Response Project (ERP) was an interdisciplinary study designed to address uncertainties about the occurrence, nature, and biological effects of episodic acidification of streams in the northeastern United States. The ERP research consisted of intensive studies of the chemistry and biological effects of episodes in 13 streams draining forested watersheds in the three study regions: the Northern Appalachian region of Pennsylvania and the Catskill and Adirondack Mountains of New York. Wet deposition was measured in each of the three study regions. Using automated instruments and samplers, discharge and chemistry of each stream was monitored intensively from fall 1988 through spring 1990. Biological studies focused on brook trout and native forage fish. Experimental approaches included in situ bioassays, radio transmitter studies of fish movement, and fish population studies. This paper provides an overview of the ERP, describes the methodology used in hydrologic and water chemistry components of the study, and summarizes the characteristics of the study sites, including the climatic and deposition conditions during the ERP and the general chemical characteristics of the study streams.
Episodic Acidification of Coastal Plain Streams: An Estimation of Risk to Fish
Authors: Gerritsen Jeroen , Dietz Jonathan M. , Wilson Harold T.
Published: April 2006

Episodic acidification is common in poorly buffered streams of the coastal plain in the Chesapeake Bay watershed, and may harm sensitive life stages of migratory fish that spawn in small streams of the region. We developed a model to predict the risk of episodic acidification in these streams that is likely to be harmful to juvenile fish. Risk predictions were based on a multiple‐regression model of acidification episodes, coupled with distribution of precipitation in the coastal plain. The regression model had four independent variables: mean baseflow, acid‐neutralizing capacity (ANC), event rainfall, a 14‐d precipitation index, and a 120‐d precipitation index; this model explained 74% of the variance in episodic pH. Bulk rainfall pH was not a significant predictor. A 30‐yr precipitation record was used to generate input data to estimate cumulative frequencies of low‐pH episodes, which also took into account the standard error of the regression. The cumulative distribution of minimum pH in streams of given ANC was in turn used to estimate the risk that fish larvae would be exposed to one or more episodes below a critical, harmful pH. Results for blueback herring and alewife larvae suggest that risk of exposure to harmful episodes (below critical pH) is ≈ 35%, for the larval stage during an average spring, in streams with baseflow ANC of 200 μ molc/L. The risk was estimated to be as high as 80% in the same streams during a wet spring. For yellow perch larvae, the estimated risk in the same streams (baseflow ANC = 200 μ molc/L) is negligible, because the critical pH for yellow perch larvae is lower than that for the herrings. The risk analysis suggests that larval mortality of river herrings due to acidification may be substantial during wet years, with > 50% of coastal plain streams affected. Management of these species should consider the risks of occasional large losses of precruitment larvae.
Modeling Historical Patterns of Tree Utilization in the Pacific Northwest: Carbon Sequestration Implications
Authors: Harmon Mark E. , Garman Steven L. , Ferrell William K.
Published: April 2006

We have developed a model, HARVEST, that predicts the mass of woody detritus left after timber harvest in Pacific Northwest forests from 1910 to the present. Inputs to the model include the species, diameter at breast height, and age distribution of trees: the minimum tree size to be harvested; the minimum top diameter; and stump height and slope steepness. Model output includes the absolute amount and the proportion of bole biomass removed as well as that left as stumps, tops, breakage, and decay. The model also predicts the biomass of nonmerchantable parts such as branches, coarse roots, and fine roots left after harvest. Model predictions were significantly correlated to residue levels reported in the literature over this period. Both model output and historical data indicate that the total amount of aboveground woody residue left after logging has decreased at least 25% over the last century. This means that release of carbon to the atmosphere from woody residue has decreased by a similar amount.
Developing a Field of Landscape Ecotoxicology
Authors: Cairns John , Niederlehner B. R.
Published: April 2006

Since toxicants are spread over ecological landscapes, it seems likely that they have effects at that level of ecological organization. Landscape ecotoxicology examines the effects of toxic chemicals on larger scales than traditional environmental toxicology. This approach is characterized by the use of endpoints appropriate to the spatial scale across which a toxicant is dispersed, attention to interactions between physical and temporal patterns and the process of ecological impairment, and integration of multiple lines of evidence for toxicity at various scales. In addition, landscape ecotoxicology seeks predictive models in order to influence human actions before environmental damage occurs. Integrating information from damaged systems, toxicity tests, simulation models, and biomonitoring of healthy systems provides the best basis for decisions. Rapid progress in landscape ecotoxicology is expected as scientists incorporate tools, such as remote sensing and spatially explicit simulation models, and then calibrate these models using data from long‐term biomonitoring of large areas. Further integration into combined socio‐economic‐ecological models is also possible.
Phosphorus Loads to Surface Waters: A Simple Model to Account for Spatial Pattern of Land Use
Authors: Soranno P. A. , Hubler S. L. , Carpenter S. R. , Lathrop R. C.
Published: April 2006

Modeling nonpoint‐source phosphorus (P) loading from land to surface waters can be both complex and data intensive. Our goal was to develop a simple model that would account for spatial pattern in topography and land use using geographic information system (GIS) databases. We estimated areas of the watershed that strongly contributed to P loading by approximating overland flow, and modeled annual P loading by fitting three parameters to data obtained by stream monitoring. We calibrated the model using P loading data from two years of contrasting annual precipitation for Lake Mendota, a Wisconsin eutrophic lake in a watershed dominated by agriculture and urban lands. Land‐use scenarios were developed to estimate annual P loading from pre‐settlement and future land uses. As much as half of the Lake Mendota watershed did not contribute significantly to annual P loading. The greatest contribution to loading came from a heterogeneous riparian corridor that varied in width from 0.1 km to ≈ 6 km depending on topography and runoff conditions. We estimate that loading from pre‐settlement land use was one‐sixth of the loading from present land use. A future scenario, representing an 80% increase in existing urban land (from 9 to 16% of total watershed area, which would be reached in 30 yr with current land‐use trends), showed only modest increases in annual P loading but possible significant effects on water quality. If the watershed were to become entirely urbanized, P loading to the lake would double and potential effects on water quality would be severe. Changes in P loading were strongest with conversions of undisturbed vegetated lands, especially riparian areas, to either urban or agricultural uses. Variability in total annual rainfall leads to variability in the riparian area that affects P loading, with implications for policies intended to control nonpoint nutrient inputs.