bluuebunny/crossref_metadata_2025 huggingface dataset:
Akan Theory of Conception–Are the Fante Really Aberrant?
Authors: Chukwukere I.
Published: April 2006

Opening Paragraph

Among the Akan-speaking peoples of Ghana the fundamental notion about the nature and composition of man—a notion which has a significant bearing on their view of the relation between man and his social, natural and spiritual worlds combined—is that each person at his or her conception receives specific physical and spiritual elements from the genitor, genetrix and Nyame, the Supreme Being. These gifts are conceptualised as bogya (or mogya in the Asante dialect), sunsum and kra, equivalent English translations in literary and popular usage being ‘blood’, ‘spirit’ and ‘soul’ respectively.
Medicines and Fetishes in Igala
Authors: Boston John
Published: April 2006

Opening Paragraph

The Igala-speaking peoples of Nigeria live in the middle belt zone of that country, close to the confluence of the river Niger and the river Benue. Ancestor cults of various kinds are central to their religious system, but there is also an important cult of the earth as well as cults of diverse spirits known collectively as ẹbọ. The latter includes the spirit of smallpox, Iye, spirits associated with water, called Alijenu, and other spirits inhabiting the fringes of cultivated land. Culturally the Igala have many close affinities with the Yoruba from whom they are separated geographically by the intervening Niger and the settlements of other peoples. But the main emphases of Igala religion are slightly different from those of Yoruba religion. Thus the cult of ẹbọ which in a rudimentary way resembles the cult of orisha among the Yoruba occupies a more marginal place in Igala religion than the orisha cults do in the Yoruba system of belief. Ancestors and the earth cults play a more direct and central role in Igala than in Yoruba. One belief which appears to be basic to both systems of thought, however, is the belief in medicine, called ogwu in Igala. Yoruba beliefs about medicine have not been published in enough detail to make systematic comparison possible. But it is hoped that the account given here of the Igala side of the picture may stimulate further work on this potentially interesting comparison.
Political sovereignty, village reproduction and legends of origin: a comparative hypothesis
Authors: Verdon Michel
Published: April 2006

The Nature of Ewe Polities: The General Problem

The Ewe-speaking people live in the southern part of the Volta Region (Ghana) and Togo. They dwell in nucleated settlements (villages) of substantial sizes (varying from a few hundred to 16,000 inhabitants in Keta, their largest town). A group of such villages (from as few as one—hardly a group!—to as many as 116 in Anlo) form a larger entity dubbed ‘traditional area’ or ‘Division’ by the British colonial administrators. These Divisions were defined as ‘the groups of villages acknowledging a commonfiagaor otherwise-titled Paramount Chief', and there are over one hundred of them in the whole of Eweland. The prevailing ethnographic and administrative opinion has been to equate these Divisions or ‘traditional areas’ with the precolonial Ewe sovereign political groups.
Resource management in Sukumaland, Tanzania
Authors: Birley Martin H.
Published: April 2006

INTRODUCTION

The attention that has been devoted to Sukumaland, Tanzania, by development specialists has been attributed by De Wilde (1967) to the rapid expansion of livestock and cotton production in ways which have been the despair of professional agriculturalists and veterinarians. Cycles of drought, famine and disease have recurred at intervals of five to seven years while soil erosion has been an ever present phenomenon. Administrative responses to these problems have followed a cycle of education, persuasion, resettlement and coercion, to little avail. A number of studies, spanning many scientific disciplines, have sought to understand, change, or merely criticize, the existing state of affairs.
Social Theory and the Study of Christian Missions in Africa: A South African Case Study
Authors: Etherington Norman
Published: April 2006

Opening Paragraph

Christian missions in Africa have produced mountains of publications which, despite their collective mass often escape notice in the wider landscape of African studies. Some of the reasons for scholarly neglect are readily apparent. A secular age is inclined to under-rate the impact of religious forces born in another era; an anti-imperialist generation of scholars is repulsed by the generally unabashed cultural imperialism of nineteenth-century evangelists; the devolution of political power from white to black hands has produced an understandable preference for the study of purely African agents of change in the recent past. Myopia, embarrassment, and the looming presence of contemporary African nationalism all encourage a tendency to leave the study of missions to antiquarians and the professionally pious.
The Role of Traditional Marriage Habits in Population Growth: the Case of Rural Eastern Nigeria
Authors: Ukaegbu Alfred O.
Published: April 2006

Introduction

The demographic transition which occurred in the West before 1900 has been attributed to the practice of delayed marriage and a significant degree of celibacy (Hajnal, 1953; 1965). In Eastern Europe where this transition occurred much later, the nuptiality patterns have been associated with historical differences in control over the nuclear family by the extended family unit (Sklar, 1974). Sklar has noted that in the late marrying Czech, Baltic, and Polish provinces, nuclear families had long been residentially and economically separate from the wider kingroup, while in the early marrying Balkans, nuclear families were intertwined with ramified kin networks.
Medicine, fetish and secret society in a West African culture
Authors: Jedrej M. C.
Published: April 2006

Opening Paragraph

Certain aspects of van Gennep's (1908) analysis of the structure of ritual symbolism have in recent years been elaborated by E. R. Leach in a series of articles dealing with such topics as magic, the symbolism of time as well as initiation rites. This development has followed two related courses. Firstly, Leach has tended to emphasize the critical significance of rites of separation rather than van Gennep's overall schema involving rites of separation, rites of transition and rites of incorporation in effecting changes in the ritual status of persons (Leach 1970). Secondly, attention has been directed instead to the symbolic importance of the residues of such rites of separation (hair, foreskin, etc.) (Leach 1958) and, to a lesser extent, the agent effecting the separation (Leach 1961). The primary purpose of this article, however, is ethnographic rather than theoretical but in so far as the results of this empirical work tend to confirm the emerging analytical schema it is not without general interest and especially as the manner of this confirmation is not quite straightforward. It will be useful first of all to consider further and in general terms the issues indicated in these opening remarks.
Ancestors as Elders in Africa
Authors: Kopytoff Igor
Published: April 2006

Opening Paragraph

Ancestor cults and ancestor worship loom large in the anthropological image of sub-Saharan Africa and few would disagree with Fortes that ‘comparatively viewed, African ancestor worship has a remarkably uniform structural framework’ (Fortes, 1965: 122). The general pattern may be quickly summarized. Ancestors are vested with mystical powers and authority. They retain a functional role in the world of the living, specifically in the life of their living kinsmen; indeed, African kin-groups are often described as communities of both the living and the dead. The relation of the ancestors to their living kinsmen has been described as ambivalent, as both punitive and benevolent and sometimes even as capricious, In general, ancestral benevolence is assured through propitiation and sacrifice; neglect is believed to bring about punishment. Ancestors are intimately involved with the welfare of their kin-group but they are not linked in the same way to every member of that group. The linkage is structured through the elders of the kin-group, and the elders' authority is related to their close link to the ancestors. In some sense the elders are the representatives of the ancestors and the mediators between them and the kin-group.
Along the Line of Road: Expanding Rural Centres in Kenya's Coast Province
Authors: Parkin David J.
Published: April 2006

Introduction

In a large area stretching north and west from Mombasa and inland from Kenya's coast, into Kilifi District, a number of small tradin centres have come to express recent changes in the relationship of Muslims to non-Muslims. The area is generally divisible into three ecological zones, identified as fishing, farming, and cattle-herding. Until Kenya's independence in 1963 the coastal strip up to about ten miles inland fell under the suzerainty of the Sultan of Zanzibar and so was dominated by Muslims. In this coastal zone fishing was, and to a large extent still is, carried out by Muslims, and farmland was held in freehold tenure by Muslims, many of whom employed non-Muslims from the hinterland to work for them, often in exchange for the use ofsome fertile coastal land. Behind the ten-mile coastal strip, non-Muslims farmed and herded cattle on land held in customary tenure. The coastal zone was thus a Muslim stronghold, yet with many non-Muslims later identified as ‘squatters’, while the hinterland wasa non-Muslim area. Since 1963 many non-Muslim ‘squatters’have been given legal rights to the land they occupy in the coastal zone, in the form of settlement scheme plots. Non-Muslims have also, since the coastal strip ceased to fall under Muslim political control, moved into trade or house-letting in the small urban centres which have expanded or sprung up in the zone.
The social structure of the Sotho-speaking peoples of Southern Africa
Authors: Kuper Adam
Published: April 2006

Introduction

In the first part of this paper I discussed the Tswana, Southern Sotho, and Kgalagadi, and showed that among all these peoples a set of intertwined variables produces a consistent pattern of marriage choices and residential alignments. These peoples are organized in tribes, under chiefs who are linked in competition and through marriage with other close agnates. The chiefdom is divided into wards, ruled often by brothers, brothers' sons, or sons of the chief, and within each ward the dominance of the central core of competing and intermarrying agnates is duplicated. Men with patrilateral ties to those in power at each level are brought into alliance or competition with them, and their relationships may be transformed or reinforced by intermarriage. Outsiders are attached to these ruling agnatic cores at each level, and develop or reinforce matrilateral ties to them by contracting suitable marriages.
Interethnic clan identities among Cushitic-speaking pastoralists
Authors: Schlee Günther
Published: April 2006

Introduction

The linguistic and religious affiliation of the peoples of the arid lowlands of northern Kenya and adjacent areas of the Horn is very heterogeneous. Although most of the populations east of Lake Turkana speak languages which belong to the Lowland branch of the Eastern Cushitic sub-family, within this branch Oromo speech (Boran, Gabbra, Sakuye, Orma) is not mutually intelligible with Somaloid languages like Rendille and Somali. Even within the Somaloid group, successful communication between monolingual Rendille and Somali is normally difficult, but a high degree of bilingualism is found.
Pottery making in Ilorin: a study of the decorated water cooler
Authors: O'Hear Ann
Published: April 2006

Opening Paragraph

This is an examination of the history, characteristics and decline of the making of water coolers, formerly a speciality of Ilorin. In order to place this in context, a brief overview of Ilorin pottery making in general is first essayed, including its derivation, continuing importance and future prospects. The association of water cooler making with particular Ilorin compounds is noted, together with the mode of transmission of this skill. Five types of cooler are described, with a sketch of what can be reconstructed of their history and origins. The decline of Ilorin cooler making and sale is demonstrated, and the factors responsible are examined. In conclusion, an attempt is made to suggest the wider significance of the study.
Marriage payments, debt and fatherhood among the Bangoua: a Lacanian analysis of a kinship system
Authors: de Latour Charles-Henry Pradelles
Published: April 2006

This article is concerned with kinship relations among the Bangoua of a Bamileke chiefdom in Cameroon. It tries first to explain, with some Lacanian concepts, how a wife-taker enters into a symbolic debt after having made the required marriage payments. These are received by two wife-givers, the bride's father and her mother's father. It is then shown that this symbolic debt, linked with the marriage contract, is a guarantee against incest. This debt, owed to the mother's father, and the debt of reciprocity due to a man's own father, sheds new light on complementary filiation and on ancestor worship in Bangoua society. It appears that, for this patrilineal society, the main social law is linked to a symbolic order in language, and, paradoxically, is focused on the mother's lineage: her father (the mother's father for her children) aid ancestors.
The dynamics of witchcraft and indigenous shrines among the Akan
Authors: Parish Jane
Published: April 2006

This article deals with Akan perceptions of witchcraft at two different anti-witchcraft shrines. It is argued that contemporary fears about witchcraft symbolise moral uncertainties about identity, sociability and materialism. These ideas are expressed by means of a highly self-reflexive critique of the concepts of social admiration and transcultural consumption.
Street children in Harare
Authors: Bourdillon M. F. C.
Published: April 2006

After giving some general information about children working on the streets of Harare, the article discusses the way children live on the streets when the streets become their home. It gives some reasons for their being on the streets, describes how they organise themselves and how they earn a living, and comments on their values. The article goes on to point out that there are a variety of perspectives on where the problem of street children lies, and to outline possible lines of intervention.
Two approaches towards the relationship between plant species diversity and ecosystem functioning
Authors: van Andel Jelte
Published: April 2006

Abstract. The main question to be dealt with in the papers published in this Special Feature is to which extent plant species richness can be applied as a parameter in restoration projects to qualify the ecosystem's state. Before considering this problem, it should be recognized that this approach illuminates only one side of the coin; the other side is touched by the opposite question, asking which plant species are essential components of an ecosystem. These two approaches towards the relationship between species richness and ecosystem functioning are not mutually exclusive, but should not be confused either. In view of ecosystem functioning certain species may be considered redundant, while in view of evolutionary processes certain ecosystem processes may be considered redundant. Where do the two approaches meet and when should they be separated? This paper touches upon this question by referring to the dual hierarchy of ecological systems.
Application of Weed Seedbank Ecology to Low‐Input Crop Management
Authors: Forcella Frank , Eradat-Oskoui Kazem , Wagner Steven W.
Published: April 2006

Pesticide use in the United States is concentrated in the Corn Belt, mainly in the form of herbicides on corn (Zea mays) and soybean (Glycine max). If this chemical load to the environment is to be reduced, without appreciably affecting crop yields, an intimate understanding of weed ecology is necessary. For annual weeds in the U.S. Corn Belt, critical ecological information includes seedbank density, seed dormancy, seedling emergence, and environmental variables that regulate these factors. For three weeds (Setaria spp., Amaranthus retroflexus, and Chenopodium album) in Minnesota, this information is summarized and its application to weed management is illustrated. If weed seedbank densities (0—10 cm depth) are <100 seeds/m2 prior to spring tillage operations, subsequent seedling populations are too low (<40 seedlings/m2) to require control. Seedbanks ranging from 100—1000 seeds/m2 produce seedling populations (<400 seedlings/m2) that can be controlled mechanically. In contrast, pre—tillage seedbanks >1000 seeds/m2 typically result in such high seedling populations that nonchemical control measures alone cannot prevent large crop yield losses. About one—half of all arable fields harbor seedbanks with densities >1000 seeds/m2. The proportion of buried seeds giving rise to seedlings is controlled by seed dormancy, which in turn is governed partially by April temperatures (in Minnesota), whereas the timing of subsequent seedling emergence is determined by soil temperature and soil water. EMERG models simulate daily percentages of emerging weed seedlings for April through June, when most Corn Belt crops are sown. If seedbeds of fields with potential seedling densities of 100 seedlings/m2 are prepared and sown when simulated emergence exceeds °80% for C. album, 85% for A. retroflexus, and 99% for Setaria spp., then mechanical weed control sufficiently reduces weed populations and crop yield losses are negligible. Accordingly, mechanical weed control may be substituted economically for chemical control, but only when accompanied by adequate understanding of the ecology of pertinent weed species.
The Influence of Plant Nutrition on Biomass Allocation
Authors: Ingestad Torsten , Agren Goran I.
Published: April 2006

The influence of nutrition on the allocation of dry matter is investigated using data from previously published experiments with the forest tree species (Betula pendular Roth., Picea babies (L.) Karst., Pinus contorta Doug., and Pinus Sibbaldia L.) where the nutrient status of the plants was maintained constant over a considerable period of time and biomass increase (steady—state nutrition and growth). We demonstrated that the allocation patterns of a plant species under limiting nutrient conditions and at optimum can be derived from parameters that have been used to characterize relationships between nutrient status, nutrient uptake, and growth of the species. The properties of the plant that control biomass allocation are discussed on the basis of these findings.
Successful Biological Control of Ragwort, Senecio Jacobaea, by Introduced Insects in Oregon
Authors: McEvoy Peter , Cox Caroline , Coombs Eric
Published: April 2006

The purpose of our study was to estimate the variability in a biological control process on a regional scale, identify its causes, and quantitatively evaluate overall control success. We present evidence of the success of biological control of Senecio jacobaea (ragwort) in western Oregon following introduction of three natural enemies. First, observations from a single site showed that ragwort declined to <1% of its former abundance and has been replaced by a plant community composed predominantly of introduced perennial grasses. Second, a perturbation experiment showed that introduced insects, within one ragwort generation, can depress the density, biomass, and reproduction of ragwort to <1% of populations protected from natural enemies. Third, a 12—yr survey of 42 ragwort populations showed that strong and persistent depression of ragwort recurred at many sites and at different times. Three features of this case history may be useful in the development of ecological theory as an explanation and guide for biological control: (1) the impact of the natural enemies depends on the distribution of individual sizes and ages in the ragwort population; (2) the long—term dynamics of ragwort may be influenced by the presence of large persistent seed bank which is invulnerable to the natural enemies; and (3) the success of biological control of ragwort in western Oregon appears to be independent of variation in environmental conditions. Combining local, short—term experiments and regional long—term observations is a powerful method for demonstrating successful biological control.
Peat Accretion and N, P, and Organic C Accumulation in Nutrient‐Enriched and Unenriched Everglades Peatlands
Authors: Craft C. B. , Richardson C. J.
Published: April 2006

Recent (1964—1989) rates of peat accretion and nitrogen (N), phosphorus (P), and organic carbon (C) accumulation were measured in Everglades soils to characterize the effects of altered hydroperiod and nutrient regimes on the nutrient storage capacity of the Everglades ecosystem. Peat accretion was related to hydroperiod and phosphorus loading. Accretion rates were highest in areas of extended hydroperiod (2.8—3.2 mm/yr) and/or phosphorus enrichment (4.0 mm/yr) and lowest in areas of reduced hydroperiod (1.6—2.0 mm/yr). Rates of accumulation of nitrogen were 3.8—ll.6 g°m—2°yr—1 (X = 8.2 g°m—2° yr—1) and those of organic C were 54—161 g°m—2°yr—1 (X = 104 g°m—2°yr—1). Accumulation rates of N and organic C were primarily a function of peat accretion rates. Phosphorus accumulation was controlled by both peat accretion and increased soil P content. Soil P concentrations (1248 @m/g) in an area receiving N and P enriched agricultural runoff were 2—3 times higher than P levels at unenriched locations (432—764 mg/g). As a result, rates of P accumulation at this site (0.46 g°m—2°yr—1) were 2—8 times greater compared to unenriched Everglades soils (0.06—0.23 g.m—2@?yr—1). Inputs of P (0.53 g.m—2.yr—1) and N (15.5 g.m—2°yr—1) to the nutrient—enriched area of Water Conservation Area (WCA) 2A (via rainfall and surface flow) were nine and twelve times higher than inputs to the unenriched part of WCA 2A. As a result, the efficiency of P removal was lower at the enriched site (87%) than at the unenriched location (100%). Nitrogen removal efficiencies also were lower in the enriched area (75%) as compared to the unenriched area, where N accumulation in peat was 290—450% of the input. The difference in N storage efficiencies between the two sites may reflect differences in N fixation and denitrification in nutrient—enriched and unenriched Everglades peatlands. Our findings suggest that nutrient—enriched agricultural drainage has contributed to increased rates of peat accretion and phosphorus accumulation in areas of the northern Everglades that have been receiving agricultural drainage for the past 25—30 yr. The affected area has functioned effectively as a phosphorus sink, primarily due to increased organic P storage. However, the effects of nutrient loading, especially P, on the long—term stability of the Everglades ecosystem and on the long—term P storage potential of Everglades peats are poorly understood and are currently under investigation.
Overview of the Oregon Transect Ecosystem Research Project
Authors: Peterson David L. , Waring Richard H.
Published: April 2006

The Oregon Transect Ecosystem Research (OTTER) project is a study of ecosystem functions in coniferous forests using the methods of computer modeling, experimental and theoretical remote sensing, and ecological field and laboratory techniques. The study is focused on predicting the major fluxes of carbon, nitrogen, and water, and the factors that dynamically regulate them. The OTTER project was conceived to test two major questions: (1) Can a generalized ecosystem simulation model, designed to use mainly parameters available from remote sensing, predict the functioning of forests across an environmentally variable region? and (2) To what extent can the variables required by this model be derived from remotely sensed data? The scientific objectives and scope of the project demanded that a coordinated effort be made to link ground measurements with remote sensing and modeling requirements. OTTER was selected as a focus for a National Aeronautics and Space Administration (NASA)—sponsored Multi—sensor Aircraft Campaign (MAC; combining NASA aircraft and sensors with those of others) on the basis of experience gained in past ecosystem studies and remote—sensing projects, and the importance of the OTTER objectives to NASA's long—range science goals and plans. Having several independent approaches available, both on the ground and from various remote—sensing platforms, proved valuable in estimating and validating many of the critical variables. This experience and cross comparison should help simplify future studies of a similar nature. Edited data sets from the OTTER project are now available to the scientific community on optical disks or via on—line data banks at NASA (Washington, D.C., USA) and Oregon State University (Corvallis, Oregon, USA).
Tropical Rain Forest Conversion to Pasture: Changes in Vegetation and Soil Properties
Authors: Reiners W. A. , Bouwman A. F. , Parsons W. F. J. , Keller M.
Published: April 2006

The effects of converting lowland tropical rainforest to pasture, and of subsequent succession of pasture lands to secondary forest, were examined in the Atlantic Zone of Costa Rica. Three replicate sites of each of four land—use types representing this disturbance—recovery sequence were sampled for changes in vegetation, pedological properties, and potential nitrogen mineralization and nitrification. The four land—use types included primary forest, actively grazed pasture (10—36 yr old), abandoned pasture (abandoned 4—10 yr) and secondary forest (abandoned 10—20 yr). Conversion and succession had obvious and significant effects on canopy cover, canopy height, species composition, and species richness; it appeared that succession of secondary forests was proceeding toward a floristic composition like that of the primary forests. Significant changes in soil properties associated with conversion of forest to pasture included: (1) a decrease in acidity and increase in some base exchange properties, (2) an increase in bulk density and a concomitant decrease in porosity, (3) higher concentrations of NH4+, (4) lower concentrations of NO3—, (5) lower rates of N—mineralization, and (6) in some cases, lower rates of nitrification. Chemical changes involving cations associated with conversion from forest to pasture indicated increases in soil fertility under the pasture regimes, while changes associated with nitrogen indicated decreases in fertility. Physical changes in density and porosity were deleterious with respect to infiltration, percolation, aeration, and, ultimately, erodability. Beyond the practical aspects of land management, many of these changes are very important to carbon and nitrogen cycling and to the emission and consumption of biogenic trace gases.
Responses of Trace Gas Fluxes and N Availability to Experimentally Elevated Soil Temperatures
Authors: Peterjohn William T. , Melillo Jerry M. , Steudler Paul A. , Newkirk Kathleen M. , Bowles Francis P. , Aber John D.
Published: April 2006

We are conducting a field study to determine the long—term response of belowground processes to elevated soil temperatures in a mixed deciduous forest. We established 18 experimental plots and randomly assigned them to one of three treatments in six blocks. The treatments are: (1) heated plots in which the soil temperature is raised 5°C above ambient using buried heating cables; (2) disturbance control plots (cables but no heat); and (3) undisturbed control plots (no cables and no heat). In each plot we measured indexes of N availability, the concentration of N in soil solutions leaching below the rooting zone, and trace gas emissions (CO2, N2O, and CH4). In this paper we present results from the first 6 mo of this study. The daily average efflux of CO2 increased exponentially with increasing soil temperature and decreased linearly with increasing soil moisture. A linear regression of temperature and the natural logarithm of CO2 flux explained 92% of the variability. A linear regression of soil moisture and CO2 flux could explain only 44% of the variability. The relationship between soil temperature and CO2 flux is in good agreement with the Arrhenius equation. For these CO2 flux data, the activation energy was 63 kJ/mol and the Q10 was 2.5. The daily average uptake of CH4 increased linearly with increasing soil temperatures and decreased linearly with increasing soil moisture. Linear regression could explain 46% of the variability in the relationship between temperature and CH4 uptake and 49% of the variability in the relationship between soil moisture and CH4 uptake. We predicted the annual CO2 flux from our study site in 1991 using two empirical relationships: the relationship between air temperature and soil temperature, and the relationship between soil temperature and CO2 flux. We estimate that the annual CO2—C flux in 1991 was 712 g/m2 from unheated soil and 1250 g/m2 from heated soil. By elevating the soil temperature 5°C above ambient, we estimate that an additional carbon flux of 538 g°m—2°yr—1 was released from the soil as CO2.
Comparing Extinction Risk and Economic Cost in Wildlife Conservation Planning
Authors: Haight Robert G.
Published: April 2006

Planning regulations pursuant to the National Forest Management Act of 1976 require the USDA Forest Service to produce cost‐effective, multiple‐use forest plans that ensure the viability of native wildlife populations within the planning area. In accordance with these regulations, this paper presents a method for determining cost‐effective conservation plans for sensitive wildlife species. The method is a decision framework for determining what forest areas should be managed as habitat to meet a population viability constraint and what areas should be used for timber production to maximize the present value of revenue from timber yields. The viability constraint is a minimum probability of meeting a standard for the risk of population extinction. This viability constraint focuses regulatory decisions on two key parameters: the standard for extinction risk and the probability of attaining the standard. The decision model is used to estimate the economic costs of these parameters. Examples for single‐ and multi‐patch conservation problems show that the cost of habitat preservation increases as the standard for extinction risk becomes more stringent and as the required probability of attainment increases. Results from the decision model are useful for evaluating research and monitoring activities and determining the economically efficient risk standard.
Phosphorus Retention in Constructed Freshwater Riparian Marshes
Authors: Mitsch William J. , Cronk Julie K. , Wu Xinyuan , Nairn Robert W. , Hey Donald L.
Published: April 2006

Four constructed freshwater riparian marshes in northeastern Illinois, USA, each experimentally subjected to either high or low loadings of turbid river water over a 3‐yr period, were investigated for phosphorus retention and fate. Average phosphorus concentrations decreased by 64‐92% in low‐flow wetlands (to 11‐40 mg P/L) and by 53‐90% (to 12‐57 mg P/L) in high‐flow wetlands. Intensive sampling at 4‐h intervals during spring and summer of the final year showed phosphorus mass decreases of 81‐74% for low‐ and high‐flow wetlands, respectively. During this frequent sampling, inflow averaged 176 mg P/L, while outflows were 34 mg P/L for the low‐flow wetland and 45 mg P/L for the high‐flow wetland. Spatial patterns of isopleths showed clear gradients in high‐flow wetlands and near‐homogeneous concentrations in low‐flow wetlands. Annual budgets illustrated that most inflowing phosphorus was retained through sedimentation with some capacity for phosphorus retention by macrophytes and a lesser amount by microbial (periphyton and planktonic) communities. A simple Vollenweider‐type model predicted well the retention of phosphorus in these wetlands for low‐ and high‐flow wetlands with 3 yr of data, i.e., the model was calibrated and verified with six independent data sets. A mean deviation of only 9.3% between measured and simulated retention was found when the retention coefficient was k = 6.51 wk‐1. Adding a factor for seasonal temperature fluctuation did not improve the fit, whereas using a model where the retention is a function of flow provided the best overall fit to the data (mean deviation of 6.3% between data and predictions). These constructed wetlands retained about the same amount of phosphorus per unit area (0.5‐3 g P°m‐2°yr‐1) as have several other natural and constructed wetlands receiving similar concentrations of phosphorus.
Using Biodiversity Data to Assess Species‐Habitat Relationships in Glacier National Park, Montana
Authors: Debinski Diane M. , Brussard Peter F.
Published: April 2006

Biodiversity surveys are becoming increasingly popular. However, standard analysis techniques for these data have not yet been developed. This paper explores the use of multivariate ordination techniques for assessing species—habitat relationships using biodiversity data. The research was conducted in Glacier National Park, Montana, and birds and butterflies were chosen as the taxonomic groups of study. Biodiversity assessment sites were established throughout a range of habitats and monitored from 1987 through 1989. Presence/absence sampling over the total number of sampling sites was used to classify species commonness and rarity. Approximately 86% of the historically recorded butterflies and 70% of the historically recorded bird species have been observed in the 3 yr of sampling. During the 3 yr of this study there was a striking continuity of species richness per site. There was also a striking overlap between sites that support high species diversity and sites that support rare species. Principal components analysis and cluster analysis worked well in discerning species—habitat relationships. Elevation, structural diversity of the site, and moisture were the major factors explaining species distributions. A chi—square analysis also provided some insights into species—habitat relationships, showing birds were more habitat specific than butterflies. Habitat diversity analyses demonstrated a positive but nonsignificant correlation between remotely sensed spectral—class diversity of a site and species richness for both birds and butterflies. Aspect, slope, and elevation diversity had a negative or negligible relationship with species richness.
Environmental and Substrate Controls over Carbon and Nitrogen Mineralization in Northern Wetlands
Authors: Updegraff Karen , Pastor John , Bridgham Scott D. , Johnston Carol A.
Published: April 2006

Northern wetlands may be a potential carbon source to the atmosphere upon global warming, particularly with regard to methane. However, recent conclusions have largely been based on short‐term field measurements. We incubated three wetland soils representing a range of substrate quality for 80 wk in the laboratory under both aerobic and anaerobic conditions at 15° and 30°C. The soils were obtained from a Scirpus‐Carex‐dominated meadow in an abandoned beaver pond and from the surface and at 1 m depth of a spruce (Picea)‐Sphagnum bog in Voyageurs National Park, Minnesota. Substrate quality was assessed by fractionation of carbon compounds and summarized using principal components analysis. Nitrogen and carbon mineralization, the partitioning of carbon between carbon dioxide and methane, pH, and Eh were measured periodically over the course of the incubation. The responses of nitrogen mineralization, carbon mineralization, and trace gas partitioning to both temperature and aeration depended strongly on the substrate quality of the soils. Sedge meadow soil had the highest nitrogen and carbon mineralization rates and methane production under anaerobic conditions, and carbon mineralization under aerobic conditions, but the surface peats had the highest nitrogen mineralization rates under aerobic conditions. Methanogenesis was highest in the sedge soil but less sensitive to temperature than in the peats. A double exponential model showed that most of the variation in nitrogen and carbon mineralization among the soils and treatments was accounted for by differences in the size and kinetics of a relatively small labile pool. The kinetics of this pool were more sensitive to changes in temperature and aeration than that of the larger recalcitrant pool. Principal components analysis separated the soils on the basis of labile and recalcitrant carbon fractions. Total C and N mineralization correlated positively with the factor representing labile elements, while methanogenesis also showed a negative correlation with the factor representing recalcitrant elements. Estimates of atmospheric feedbacks from northern wetlands upon climatic change must account for extreme local variation in substrate quality and wetland type; global projections based on extrapolations from a few field measurements do not account for this local variation and may be in error.
The Effect of Site Environment on Forest Productivity in the Illinois Shawnee Hills
Authors: Fralish James S.
Published: April 2006

The relationship of total basal area to soil and topographic factors was studied in 47 undisturbed, mature, compositionally stable (climax) stands. Forward stepwise multiple linear regression was used to develop two predictive models. Effective soil depth, percentage stone, aspect, and slope position were predictor variables in model I. Soil profile available water capacity, slope position, and aspect were predictor variables in model II. Model I is the more practical and easily applied model in stands where soil depth can be rapidly determined; model II requires additional soil measurements but can be used to assess the more direct biological relationship between soil water and basal area. Models I and II accounted for 91 and 93% of the variation in stand basal area, respectively, and were validated with data from seven additional mature stands. Subsequently the models were used to predict potential (maximum) basal area in eight stands where it had been reduced by disturbance; the models also were used to evaluate the effect of farming on the productivity of fields abandoned in the 1930s. Presettlement basal area was estimated to have been between 18 and 26 m2/ha but soil loss due to erosion has reduced the potential basal area to 8—21 m2/ha should hardwood stands redevelop. For comparison with a standard site evaluation technique, 27 undisturbed Quercus alba stands were used to develop another multiple linear regression model to predict site index from site factors. Soil profile available water holding capacity, slope position, and aspect were predictor variables in model III, which accounted for 73% of the variation in site index, a substantial reduction in predictive value from model II, which predicts potential stand basal area using the same three variables. Simple regression indicated a strong positive linear relationship between stand basal area and site index (r = 0.85, P < .01). The strong relationship of stand basal area to soil and topographic factors and to standard site index measurements indicates that models to predict potential basal area may be used to evaluate site productivity in the Illinois Shawnee Hills.
Models to Evaluate Headstarting as a Management Tool for Long‐Lived Turtles
Authors: Heppell Selina S. , Crowder Larry B. , Crouse Deborah T.
Published: April 2006

Most turtle species suffer highly mortality in their first year, have a long juvenile period, and can live for decades once they reach adulthood. Conservationists have implemented a number of recovery plans for threatened turtle populations, including experimental headstart programs. Headstarting involves the captive rearing of hatchlings from eggs collected in the wild. The hatchlings are held for several months to help them avoid high mortality in their first year. It is hoped that these turtles survive and grow like wild turtles after release. The purpose of our study was to evaluate headstarting as a management tool for threatened turtle populations. We critically examined the population‐level effects of headstarting with a series of deterministic matrix models for yellow mud turtles (Kinosternon flavescens), a non‐threatened, well‐studied species, endangered Kemp's ridley sea turtles (Lepidochelys kempi). We show that management efforts focused exclusively on improving survival in the first year of life are unlikely to be effective for long‐lived species such as turtles. Population projections for both turtles predict that head‐starting can augment increasing populations when adult survival is returned to or maintained at high levels, provided that headstarted juveniles are as vigorous as wild turtles. However, when subadult and adult survival is reduced, headstarting cannot compensate for losses in later stages. Proportional sensitivity (elasticity) analyses of stage‐based matrix models indicated that annual survival rates for subadult and adult turtles are most critical; small decreases in the survival of older turtles can quickly overcome any potential benefits of headstarting. In general, the biological benefits of headstarting programs may be overestimated for turtles, and a careful examination of stage‐specific mortality sources, demography, and life history can guide us toward more effective management strategies.
Improving the Success of Wetland Creation and Restoration with Know‐How, Time, and Self‐Design
Authors: Mitsch William J. , Wilson Renee F.
Published: April 2006

The creation and restoration of new wetlands for mitigation of lost wetland habitat is a newly developing science/technology that is still seeking to define and achieve success of these wetlands. Fundamental requirements for achieving success of wetland creation and restoration projects are: understanding wetland function; giving the system time; and allowing for the self‐designing capacity of nature. Mitigation projects involving freshwater marshes should require enough time, closer to 15‐20 yr than 5 yr, to judge the success or lack thereof. Restoration and creation of forested wetlands, coastal wetlands, or peatlands may require even more time. Ecosystem‐level research and ecosystem modelling development may provide guidance on when created and restored wetlands can be expected to comply with criteria that measure their success. Full‐scale experimentation is now beginning to increase our understanding of wetland function at the larger spatial scales and longer time scales than those of most ecological experiments. Predictive ecological modelling may enable ecologists to estimate how long it will take the mitigation wetland to achieve steady state.
The Vegetation of Restored and Natural Prairie Wetlands
Authors: Galatowitsch Susan M. , van der Valk Arnold G.
Published: April 2006

Thousands of wetland restorations have been done in the glaciated mid‐continent of the United States. Wetlands in this region revegetate by natural recolonization after hydrology is restored. The floristic composition of the vegetation and seed banks of 10 restored wetlands in northern Iowa were compared to those of 10 adjacent natural wetlands to test the hypothesis that communities rapidly develop through natural recolonization. Restoration programs in the prairie pothole region assume that the efficient‐community hypothesis is true: all plant species that can become established and survive under the environmental conditions found at a site will eventually be found growing there and/or will be found in its seed bank. Three years after restoration, natural wetlands had a mean of 46 species compared to 27 species for restored wetlands. Some guilds of species have significantly fewer (e.g., sedge meadow) or more (e.g., submersed aquatics) species in restored than natural wetlands. The distribution and abundance of most species at different elevations were significantly different in natural and restored wetlands. The seed banks of restored wetlands contained fewer species and fewer seeds than those of natural wetlands. There were, however, some similarities between the vegetation of restored and natural wetlands. Emergent species richness in restored wetlands was generally similar to that in natural wetlands, although there were fewer shallow emergent species in restored wetlands. The seed banks of restored wetlands, however, were not similar to those of natural wetlands in composition, mean species richness, or mean total seed density. Submersed aquatic, wet prairie, and sedge meadow species were not present in the seed banks of restored wetlands. These patterns of recolonization seem related to dispersal ability, indicating the efficient‐community hypothesis cannot be completely accepted as a basis for restorations in the prairie pothole region.
Effects of Groundwater Decline on Riparian Vegetation of Semiarid Regions: The San Pedro, Arizona
Authors: Stromberg J. C. , Tiller R. , Richter B.
Published: April 2006

Groundwater depletion threatens many riparian ecosystems in arid and semi‐arid regions of the world. The aquifer that sustains Arizona's San Pedro River riparian ecosystem, for example, is threatened by regional groundwater declines and localized pumping from the alluvial aquifer. This paper demonstrates the important role of shallow groundwater in structuring the San Pedro River plant community, portions of which function as reference areas that indicate site potential for a globally rare forest type (Sonoran riparian Populus‐Salix forests). Several ecological indicators varied with depth to groundwater, including a weighted average wetland indicator score calculated for herbaceous and woody plant species, cover of plants within wetland indicator groups, and frequency of indicator plant species. These relationships can be used in a space‐for‐time substitution to predict consequences of groundwater decline. For example, the wetland indicator score changed sharply as depth to groundwater ranged from 0 to 4 m, and abundance of obligate wetland herbs (the group most sensitive to groundwater changes) declined sharply at groundwater depths below ≈ 0.25 m. Such sequential desertification of the riparian flora (i.e., loss or reduction in cover of species based on their probability of occurrence in wetlands) is one predicted response to groundwater decline. Other predicted impacts of groundwater decline include reduced establishment of Populus fremontii‐Salix gooddingii forests, and reduced cover of herbaceous species associated with the fine‐textured soils and shady conditions of floodplain terraces stabilized by these early seral tree species. High floodplain terraces (depth to groundwater of 5‐8 m) had wetland indicator scores below those of upland sites and were vegetated by species (e.g., Prosopis velutina and Sporobolus wrightii) with low sensitivity to groundwater changes.