bluuebunny/crossref_metadata_2025 huggingface dataset:
Marriage Payments, Household Structure, and Domestic Labour-Supply among the Barma of Chad
Authors: Reyna Stephen
Published: April 2006

Opening Paragraph

This paper investigates the relationship between marriage payments, household structure, and domestic labour-supply among the Barma of the Republic of Chad. Recently, Netting has noted that ‘…household composition among farmers varies with the type and amount of labor required for effective crop production’ (1974: 29). Netting is supported by evidence from Europe (Chayanov: 1966; Symes: 1972); Africa (Jones: 1949; Basehart: 1973; Netting: 1968; Reining: 1970; Udo: 1965); Asia (Barth: 1959; Befu: 1968; Leach: 1961; Moerman: 1968; Yang: 1945); South America (Webster: 1973); North America (Bennett: 1969); and the Pacific (Sahlins: 1957). Implicit in this literature is the realization that the household structural types prevalent in societies are those which provide adequate labour supplies in specific ecosystems with particular agrarian technologies. While this research indicates that differing agrarian societies require varying labour supplies, it does not in general showhowthey achieve these supplies. This paper demonstrates how marriage payments may operate to regulate different aspects of household structure to provide adequate labour to the Barma domestic unit.
Households and the political economy of small-scale cash crop production in south-western Nigeria
Authors: Clarke Julian
Published: April 2006

Opening Paragraph

The emergence of small-scale cash crop producers throughout West Africa is of central importance to those historians, anthropologists and sociologists who are working on change in the political economies of various parts of West Africa.
The Establishment of the Medina in Dakar, Senegal, 1914
Authors: Betts Raymond F.
Published: April 2006

Opening Paragraph

While the social history of Dakar, Senegal, exhibits many of the characteristics common to most Eurafrican cities on the West coast, the rather abrupt manner in which the policy of residential segregation replaced the earlier pattern of co-existence, if not integration, of the African and European populations merits particular attention. The establishment of the Medina—the ‘native quarter’, to employ the colonial idiom of the day—was the most decisive and significant action taken by the French authorities in the history of the city. Yet this decision resulted from no carefully considered change in administrative policy, which had been somewhat laissez-faire in residential matters, but rather was hastily urged after the outbreak of a severe epidemic of bubonic plague in 1914. What began medically was to become, however, a major social and urban problem.
A note on the Asante akonkofo: a non-literate Sub-elite, 1900–1930
Authors: Arhin Kwame
Published: April 2006

Opening Paragraph

Following the growing interest in recent years in social stratification in Asante in the nineteenth and twentieth centuries (Arhin, 1983a: 2–22; 1983b: 475; McCaskie, 1983: 23–44; Wilks, 1975: 166–719), this note offers a preliminary study of a body of men who became known in Kumasi and the capital towns of the other Asante chiefdoms – in particular Bekwai, Juaben and Mampon – as the akonkofo in the first phase of colonial rule, 1896–1930. The argument of the paper, written in the light of the views of Daaku (1970, 1971) is that the akonkofo, an intermediary group between office holders and non-holders of office (Arhin, 1983a) could emerge as a distinctive sociopolitical category only in the colonial period. The first section of this article, on the origin of the akonkofo, describes the factors that inhibited the rise of ‘merchant princes’ in Asante before colonial rule; the second, on the akonkofo in Kumasi, offers a kind of social portrait of the akonkofo; and the third section, on the position of the akonkofo in Asante society, examines the relationship of the akonkofo to traditional authority. My sources are archival and written. I have also recorded interviews with Barima Owusu-Ansah, over seventy-five years old, and a leading authority on Asante law and constitution, and with Baffour Osei Akoto, senior spokesman (okyeame) of the Asantehene and just turned seventy, as well as conversations with sundry officials at the Asantehene's court.
Fighting over property: the articulation of dominant and subordinate legal systems governing the inheritance of immovable property among Blacks in Zimbabwe
Authors: Cheater A. P.
Published: April 2006

Opening Paragraph

Law, particularly the law of property, may indeed be an instrument of the ruling class for the reproduction of any given social and economic formation, but few anthropologists have pursued this line of argument. Instead of examining how law was actually generated within particular political and economic contexts, anthropologists concerned with property law in colonial Africa tended to take for granted its existence at a particular point in time, and either to emphasise the institutional duality of colonial and indigenous assumptions and procedures concerning property or to stress the universal elements of legal behaviour despite these institutional differences.
Divorce in Abutia
Authors: Verdon Michel
Published: April 2006

Opening Paragraph

Like most southern Ghanian populations, the Abutia Ewe – one of the numerous ‘village leagues’ which compose the northern part of Eweland (Volta region)– have experienced far-reaching transformations in the last century, and nowhere more radically than in their matrimonial practices. In this article, I wish to concentrate on two aspects of these practices, namely the definition of marriage and the incidence of divorce.

Indeed, an adequate analysis of divorce requires some heuristic tools which enable us to decide whether particular couples are ‘married’ or not, a procedure made extremely difficult in the case of Abutia because of the changes in their definition of marriage. In the first part of the article, I shall briefly survey these changes and discuss the definitional problems they raise and, in the second, present the main findings of a quantitative survey which helps to measure the impact of the changes discussed. It also reveals that divorce was in fact common before 1890, when German colonial rule was imposed. In the third and last part I seek to explain this marital instability in ‘pre-colonial’ Abutia.
Islam in Senegalese literature and film
Authors: Cham Mbye B.
Published: April 2006

Opening Paragraph

In few other places in the creative traditions of sub-Saharan Africa is the factor of Islam more prominent and influential than in Senegal. Manifested in form and subject matter and spanning a wide cross-section of talent in both the traditional and modern media of creative expression, this prominence and influence can be attributed to a number of factors ranging from the artistic maturity, religious sensibility, intellectual astuteness and ideological orientation of individual artists, to the more general impact that Islam as a dominant religious force is perceived to have had on secular life in Senegal. These factors to a large extent determine the various ways in which individual Senegalese artists define themselves and their art vis-è-vis Islam in particular and society in general. These definitions are creatively translated into choice of form, thematic focus and, to use a cliché, ‘message’.
Breaking up the bottlenecks in food-crop and cotton cultivation in northern Côte d'Ivoire
Authors: Bassett Thomas J.
Published: April 2006

Introduction

It is widely recognised that seasonal labour bottlenecks present major obstacles to peasant farmers seeking to expand agricultural output in sub-Saharan Africa. Evidence from Nigeria and Sierra Leone, for example, reveals that labour shortages and limited income to hire off-farm labour have historically constrained rural producers from intensifying and enlarging their agricultural operations (Norman et al., 1979: 42–7; Watts, 1983: 202–3; Richards, 1985: 96). Many attempts by colonial and contemporary African States to promote food crop and export crop production failed, in part, because of peasant resistance to the threat of subsistence insecurity associated with labour conflicts in the agricultural calendar. Richards's (1986) study of the failure of a series of labour-intensive wet rice cultivation projects in central Sierra Leone illustrates the degree to which peasant agricultural practices represent adjustments to labour-supply problems. Given the pervasiveness and importance of seasonal labour constraints in African agricultural systems, it is surprising that ‘few studies have provided insights into the adjustment in labor use resulting from the introduction of cash crops and new technologies’ (Eicher and Baker, 1982: 99).
Ethnography and the closing of the frontier in Lower Congo, 1885–1921
Authors: MacGaffey Wyatt
Published: April 2006

Opening Paragraph

The research that led to the writing of this paper began with a puzzle. The four volumes of K. E. Laman's Kongo ethnography (1953–68) are based on texts written by BaKongo. Who were these men and why is there no explicit reference to them in the books? The lack of any indication of who wrote what and on what authority deprives this ethnography of much of its potential value (Janzen, 1972). In search of biographical information, I turned to the bulletin Minsamu Miayenge (MM), published by the Swedish Missionary Society (SMF) from 1892 onwards. From its pages emerged a clear sense of a group of men whose position in the nascent colonial order explained both their ethnographic ambitions and their subsequent disappearance from the record.
Cattle raiding and household demography among the Kuria of Tanzania
Authors: Fleisher Michael L.
Published: April 2006

Among the agro-pastoralist Kuria people inhabiting the Tarime District lowlands of northern Tanzania, many young men are engaged in cattle raiding, which constitutes a primary means of generating cash income. Data from a sample of sixty-four Kuria cattle raiders reveal that three-quarters of them grew up in natal households having more sons than daughters, strongly suggesting that it is the need for the sons of a household to acquire their own bridewealth cattle by means other than through sisters' marriages that constitutes the strongest predictor of which young men will opt to become cattle raiders.
Lua-lia, the ‘fresh funeral’: founding a house for the deceased among the Kasena of north-east Ghana
Authors: Abasi Augustine Kututera
Published: April 2006

For the Kasena, life finds in death both its measure and its renewal. Indeed, the dead survive through their descendants and in the world of ancestors. Funeral practices are very elaborate. They not only reflect the social, cultural, religious and psychological values and preoccupations shared by the group but are also a way of elaborating upon them. Social and cultural life is re-invigorated through a person's death and funerals, while the dead person is himself the foundation of his descendants' life.

This article, drawing from fieldwork in the author's native area, focuses, in particular, on first funerals for adults. Detailed description is followed by the analysis of surprising similarities between birth and funeral rites. It then examines the ‘house’ or the ‘bedroom’ built in the ground – either in the maternal bedroom itself, or in a neighbouring field towards the east – in order to welcome death as an extension, as a founder in the depths of the survivors' dwelling.
Style in modern Nigerian Art music: the pioneering works of Fela Sowande
Authors: Omojola 'Bode
Published: April 2006

The Nigerian musical landscape changed significantly following the advent of Christian missionary activity and British colonial administration in the later nineteenth century. New idioms of musical practice which have evolved as a result of this historical process include a new tradition of religious, Christian, music, urban syncretic popular styles, new operatic forms and European-derived art/ classical music. This article focuses on one of these emerging styles, Nigerian art music, as reflected in the life and works of its most notable pioneer, Fela Sowande. After a brief historical background, the article discusses the circumstances of Sowande's life and the beliefs which shaped his composing career and his compositional style. In discussing elements of style in Sowande's works, it examines the nature of the interaction between African and European elements, a stylistic feature which constantly recurs in his works. The article ends by discussing the need to consolidate the growth of this new idiom by putting in place institutional structures within which it can develop.
III. Walter Gore
Authors: Gore Paula Hinton
Published: April 2006

The hurly-burly of the sea has the tang of the salt sea-waves the return of fishermen from the sea
Linear least squares prediction in non-stochastic time series
Authors: Finch P. D.
Published: April 2006

Many problems arising in the physical and social sciences relate to processes which happen sequentially. Such processes are usually investigated by means of the theory of stationary stochastic processes, but there have been some attempts to develop techniques which are not subject to the conceptual difficulties inherent in the probabilistic approach. These difficulties stem from the fact that in practice one is often restricted to a single record which, from the probabilistic point of view, is only one sample from an ensemble of possible records. In some instances such a viewpoint seems artificial, and for some time series it is questionable whether any objective reality corresponds to the idea of an ensemble of possible time series. For example, as noted in Feller (1967), a theory of probability based on a frequency interpretation cannot meaningfully attach a probability to a statement such as “the sun will rise tomorrow”, because to do so one would have to set up a conceptual universe of possible worlds.
Blue Data Books ‐ an encouraging new instrument for restoration and conservation
Authors: Gigon Andreas , Langenauer Regula
Published: April 2006

Abstract. In order to stress successes in restoration and conservation of species, regionally, nationally or globally, a new instrument has been developed, the ‘Blue Lists’, ‘registers of those Red List species that show a durable overall stabilization or increase of abundance in the region (nation, world) considered’. ‘Blue Data Books’ include additional information on the ecology, conservation, and promotion of the species. For describing the overall change of abundance of every individual species six categories are defined. Furthermore, the effects of nature conservation techniques (NCT) on a species are evaluated using six additional categories. In a test area of 3 431 km2 in northern Switzerland, information was compiled on the change in abundance of the 708 Red List species of higher plants (spermatophyta) over the last 10‐15 yr. Overall, 33% of these species showed a stabilization or even increase in abundance; these are Blue List species; ca.20% showed a decline and for almost 50% the change in abundance is not known. NCTs have been successfully applied to more than 50 % of all the species, at least locally. For about a further 30%, the required NCTs are known but have not yet been tried out. If these techniques were applied on a large scale, the decline of very many species in the test area could be stopped.
Making Ecological Information Practical for Resource Managers
Authors: Risser Paul G.
Published: April 2006

There has been a tendency for ecologists to present results from ecological studies and then be critical of resource managers because the best available scientific information was not incorporated into decisions about natural resources. This unfortunate situation must be remedied by ecologists, who should explicitly consider the ways in which results can be applied to management issues. Ecologists and resource managers should collaborate to establish the topical framework in which concepts such as growth compensation/overcompensation should be considered. Finally, under presettlement conditions, the tallgrass prairie probably produced overcompensation under lightly to moderately grazed conditions.
Canopy Architecture of Natural and Planted Cordgrass Marshes: Selecting Habitat Evaluation Criteria
Authors: Zedler Joy B.
Published: April 2006

In order to set standards for restoration or mitigation "success" of salt marsh habitat designed for an endangered southern California bird, I explored the bird's nesting requirements, compared constructed habitats that lack the bird with natural habitats that support it, and selected habitat assessment criteria that best distinguish suitable and unsuitable nesting habitats. Selected attributes of canopy architecture are recommended for assessing the suitability of intertidal cordgrass (Spartina foliosa) marshes for the endangered Light—footed Clapper Rail (Rallus longirostris levipes) of southern California. Nests are built at °145 cm above Mean Lower Low Water (MLLW = 0 tidal datum), with nest rims at °165—170 cm MLLW; however, extreme high water is 232 cm MLLW during the March—July nesting season, and tidal inundation is a major cause of nest failure. Cordgrass that is >60 cm tall appears necessary for birds to weave a canopy that allows the nest to float upward, but not away, as the tide rises. Cordgrass height distributions and density data describe attributes of canopy architecture that assess Clapper Rail habitat value better than previously used measures (i.e., cover, biomass, mean height, maximum height). Height histograms differ for planted marshes (which do not support Clapper Rails) and natural marshes. The constructed marshes have few plants over 60 cm, while most stems in natural marshes exceed 60 cm. In natural marshes, cordgrass heights increase with freshwater flooding and nitrogen enrichment. Reference data from natural marshes that are used by Clapper Rails indicate that the standard for "suitable habitat" should be a density of at least 100 stems/m2 with at least 90 stems/m2 >60 cm, of which at least 30 stems/m2 are >90 cm in height. High interannual and spatial variability indicates the need for several (e.g., 20) years of data for assessment purposes and a large data base for reference wetlands.
Effects of Climate Change on Plant Respiration
Authors: Ryan Michael G.
Published: April 2006

Plant respiration is a large, environmentally sensitive component of the ecosystem carbon balance, and net ecosystem carbon flux will change as the balance between photosynthesis and respiration changes. Partitioning respiration into the functional components of construction, maintenance, and ion uptake will aid the estimation of plant respiration for ecosystems. Maintenance respiration is the component most sensitive to changes in temperature, CO2, protein concentration and turnover, water stress, and atmospheric pollutants. For a wide variety of plant tissues, maintenance respiration, corrected for temperature, appears to be linearly related to Kjeldahl nitrogen content of live tissue. Total and maintenance respiration may decline under CO2 enrichment, but the mechanism, independence from changes in protein content, and acclimation are unknown. Response of respiration to temperature can be modelled as a Q10 relationship, if corrections for bias arising from daily and annual temperature amplitude are applied. Occurrence and control of the cyanide—resistant respiratory pathway and acclimation of respiration rates to different climates are poorly understood, but may substantially affect the reliability of model estimates of plant respiration.
Sucrose Repellency to European Starlings: Will High‐Sucrose Cultivars Deter Bird Damage to Fruit?
Authors: Brugger Kristin E. , Nol Pauline , Phillips Calista I.
Published: April 2006

European Starlings (Sturnus vulgaris) are often pests in commercial fruit crops in North America and Europe. Because starlings slack the digestive enzyme sucrase and cannot digest sucrose, they may develop an aversion to high—sucrose fruits. In water—tube drinking trials, we tested captive starlings with aqueous solutions of 15% (mass/volume) mixed sugars to identify the level of sucrose required to develop a conditioned feeding aversion when digestible sugars are present. In one—tube tests, starlings decreased intake of 11.25 and 15% sucrose solutions relative to their pretest intake of a 15% glucose—fructose mixture. In two—tube tests with sucrose solutions paired against a digestible glucose—fructose solution, starlings decreased preferences for the sucrose solutions as sucrose concentrations increased. These data suggest that the presence of digestible nutrients mitigates the effect of sucrose in sucrase—deficient birds and that a fruit cultivar would require @> 11.25% sucrose to repel starlings.
Disappearance and Compressibility of Buried Pine Wood in a Warm Temperate Soil Environment
Authors: Gholz H. L. , Krazynski L. M. , Volk B. G.
Published: April 2006

The rate of disappearance of buried pine wood in Florida was found to be 15%/yr.As consumption by microorganisms and termites proceeded, the wood also became more compressible. After only 5 yr, consumption and compression could account for 60—70% loss of original volume of wood under pavement near the surface of an embankment. This large volume loss occurring in a relatively short time period may be responsible for many surface deformations in pavements and weaknesses in other embankments where wood may occur as a contaminant.
Aggregating Fine‐Scale Ecological Knowledge to Model Coarser‐Scale Attributes of Ecosystems
Authors: Rastetter Edward B. , King Anthony W. , Cosby Bernard J. , Hornberger George M. , O'Neill Robert V. , Hobbie John E.
Published: April 2006

As regional and global scales become more important to ecologists, methods must be developed for the application of existing fine—scale knowledge to predict coarser—scale ecosystem properties. This generally involves some form of model in which fine—scale components are aggregated. This aggregation is necessary to avoid the cumulative error associated with the estimation of a large number of parameters. However, aggregation can itself produce errors that arise because of the variation among the aggregated components. The statistical expectation operator can be used as a rigorous method for translating fine—scale relationships to coarser scales without aggregation errors. Unfortunately this method is too cumbersome to be applied in most cases, and alternative methods must be used. These alternative methods are typically partial corrections for the variation in only a few of the fine—scale attributes. Therefore, for these methods to be effective, the attributes that are the most severe sources of error must be identified a priori. We present a procedure for making these identifications based on a Monte Carlo sampling of the fine—scale attributes. We then present four methods of translating fine—scale knowledge so it can be applied at coarser scales: (1) partial transformations using the expectation operator, (2) moment expansions, (3) partitioning, and (4) calibration. These methods should make it possible to apply the vast store of fine—scale ecological knowledge to model coarser—scale attributes of ecosystems.
Evaluation of Population Trend Estimates Calculated Using Capture‐Recapture and Population Projection Methods
Authors: Bart Jonathan
Published: April 2006

Concern has arisen recently that Northern Spotted Owl (Strix occidentalis) populations may be declining faster than suspected by Spotted Owl biologists. This is based on recent estimates by the USDI of the annual rate of change in population size (i.e., population trend) calculated using capture–recapture and population projection methods. These original reports estimated change in the territorial population but used an inappropriate demographic model which did not incorporate immigration from the floater population. This approach, however, would be appropriate for estimating trend in the total population (floaters and territorial birds) if the model assumptions were met. This raises the possibility that Northern Spotted Owl populations are declining at approximately the rate reported in the USDI studies (6‐8% per year) rather than at the rate previously suspected (1‐3% per year). I investigated this issue using a stochastic computer simulation in which population trends were estimated with capture–recapture and population projection methods and compared to the true population trends in the simulation. Factors that might cause bias in the trend estimate were identified and set to simulate the smallest and largest likely bias. The most important of these factors were the floater population and permanent emigration from the study site. Results showed that population trends in the simulation were underestimated by 0.03 to 0.13. Thus if the true annual rate of change in population size were 0.99 (i.e., a decline of 1%/yr), the estimate of 0.99 provided by the USDI studies would be 0.86 to 0.96. The simulations also provided new evidence, based on the past and current size of the floater population, indicating that Northern Spotted Owl populations have probably been declining at an average rate of ≤3% per year during the past few decades. My analysis indicates that the USDI studies should not be interpreted as providing evidence that owl populations are declining faster than previously assumed. We need careful investigation of trend estimates based on capture–recapture and demographic analyses before they are used as the basis for management decisions.
Air Pollution and Forest Ecosystems: A Regional to Global Perspective
Authors: Taylor George E. , Johnson Dale W. , Andersen Christian P.
Published: April 2006

Changes in the atmospheric concentrations of a number of air pollutants over the last century are hallmarks of the magnitude and extent of human impact on the environment. Some of these changes are important to ecologists because many pollutants, acting singly or in combination, affect ecological systems in general and forests in particular. The greatest concern lies with chronic levels of tropospheric ozone, cumulative deposition of hydrogen ion, nitrogen, and sulfur via wet and dry processes, a select number of airborne chemicals (e.g., mercury) that tend to bioaccumulate in continental landscapes, and ultraviolet—B radiation through the loss of stratospheric ozone. Because the atmospheric residence time of most pollutants of concern to ecologists is measured on time frames extending from a few weeks to decades, pollutant distribution and effects are regional to global in dimension. We present evidence that ambient levels of some air pollutants in North America are affecting managed and unmanaged forests, and that the two most important pollutants are tropospheric ozone and chronic nitrogen loading. Further evidence indicates that while concentrations of some air pollutants have been declining over the last decade in North America, others are expected to remain unchanged or increase, including tropospheric ozone. We conclude that air pollution is affecting many North American forests and some remote forests around the globe. In the immediate future, the concern for air pollution effects on forests and associated natural resources will broaden to include interactions with changes in climate and pollution effects in the world's developing countries. There has been a rapid evolution in air pollution studies in ecology, shifting away from the agricultural paradigm of single—factor experimentation toward new methodologies that are ecologically and multidisciplinarily based. This shift has been promoted by the recognition that air pollution is one of several factors influencing forest productivity, community dynamics, and biogeochemistry, and that effects arise through long—term exposures. This evolution in methodologies will become even more marked in the future as new ecological approaches are adopted and an understanding is developed of how air pollution interacts with changes in climate. One of the most promising methodologies is process level modeling, which utilizes the large base of data in tree physiology and forest ecology, watershed chemistry, and atmosphere— forest canopy meteorology to develop models of tree physiology and growth and to subsequently scale these investigations to the levels of forest stands and landscapes.
Small Mammals in Managed, Naturally Young, and Old‐Growth Forests
Authors: Carey Andrew B. , Johnson Murray L.
Published: April 2006

Forest managers in the Pacific Northwest are faced with new challenges of providing for all wildlife in managed forests. Our objective was to elucidate the factors governing the composition and biomass of forest floor mammal communities that are amenable to management. We sampled small mammal communities in forests of various management histories on the Olympic Peninsula and contrasted our results with those of other large studies in the Pacific Northwest. Forest floor mammal communities in forests >35 yr old in the Western Hemlock Zone of Washington and Oregon are composed of 5‐8 characteristic species. These include Sorex trowbridgii (numerically the most dominant); one species each of Clethrionomys, the Sorex vagrans complex, and Peromyscus; and Neurotrichus gibbsii. Species composition changes from south to north, and the communities on the Olympic Peninsula contain two or three additional species compared to communities to the south. Communities in naturally regenerated and clearcutting regenerated (managed) young forests are similar in composition to those in old growth, old growth, however, supports 1.5 times more individuals and biomass than managed forest. Community diversity seems related to the south‐north moisture‐temperature gradient that is reflected in increased diversity of canopy conifers, development of forest floor litter layers, accumulation of coarse woody debris, and abundance of herbs, deciduous shrubs, and shade‐tolerant seedlings (as opposed to understories dominated by evergreen shrubs). Previous work found few habitat variables that were good predictors of species abundance in natural young and old‐growth stands. Naturally regenerated young stands had higher levels of coarse woody debris than old growth. Managed stands had much lower abundance of coarse woody debris and tall shrubs than old growth. Understory vegetation (herbs and shrubs) and coarse woody debris accounted for a major part of the variation in abundance of six of eight species in managed stands, but only two species in old growth. Management of Western Hemlock Zone forest for conservation of biodiversity and restoration of old‐growth conditions should concentrate on providing multispecies canopies, coarse woody debris, and well‐developed understories.
Landscape Ecology and Diversity Patterns in the Seasonal Tropics from Landsat TM Imagery
Authors: Rey-Benayas Jose M. , Pope Kevin O.
Published: April 2006

We examine patterns of landscape diversity in the seasonal tropical forests of northeastern Guatemala with analyses of Landsat Thematic Mapper (TM) imagery. Our primary objective is to demonstrate that TM analyses, without extensive field data, provide valuable information on landscape diversity patterns to aid conservation and development plans. A principal components analyses indicates that the major source of variability at the scale of TM resolution (°30 m) is related to TM band 4 (TM4) radiance, and that the second and third most important sources are related to TM bands 5 and 7, respectively. Cluster analysis of TM4, TM5, and TM7 radiance produced six distinct land‐cover types, which follow a topographic gradient. Both TM radiance and the radiance coefficient of variation (CV) are significant in discriminating land‐cover types. The primary source of variability within upland forests is related to TM4, and the primary sources of variability within lowland swamps are related to TM5 and TM7. We infer from these results that green leaf biomass is the most important variable in discriminating between land‐cover types in the uplands, and that canopy closure and degree of senescence are the most important variables in the lowland swamps. We also examined patterns of landscape diversity reflected in three landscape indices: the number of land‐cover types (LCT), the Shannon‐Weaver index of landscape evenness (S‐W), and a topographic index (TI). The strongest correlations were found for TM4 radiance and TI (r = 0.94, n = 30, P < 0.0001) and S‐W (r = ‐0.72, n = 30, P < 0.0001), and between TM4 radiance CV and LCT (rs = 0.67, n = 30, P < 0.0001). Thus, TM4 provides a good measure of landscape diversity. We found a perfect nonparametric correlation (rs = 1, n = 6) between TM4 radiance CV within a land cover type and the type's TI rank, which probably reflects increasing canopy heterogeneity between lowland swamps and upland forests. Finally, we demonstrate the potential of TM‐based land‐cover maps and diversity indices in designing and monitoring nature reserves.
Forest Age Structure and Development Following Wildfires in the Western Olympic Mountains, Washington
Authors: Huff Mark H.
Published: April 2006

Fire is an important disturbance agent influencing forest composition and structure in Pacific Northwest ecosystems. I examined the effects of a long fire‐return interval on forest development, composition, and tree age structure for a post‐fire sere on the west slope of the moist Olympic Mountains. Similar sites that burned in 1978, 1961, 1870, 1799, and circa 1465 were selected. Tree cores and size characteristics were collected from two randomly located 0.25‐ha plots at each site. Fires usually burned catastrophically, killing most overstory vegetation. Pioneer tree species were Douglas‐fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla); western hemlock assumed numerical dominance early in the sere. Forest reestablishment after fire was slow, taking ≥50 yr to complete establishment of shade‐intolerant Douglas‐fir. Understory establishment of western hemlock increased 150 yr after fire, although conditions that enhance its long‐term survival may occur ≈300 yr or more after fire. Establishment of western hemlocks existent at the 1465 fire site peaked ≈365‐424 yr after the fire; individuals establishing 150‐300 yr after the fire occurred much less frequently. Fire exclusion would shift the replacement sequence toward a wet, very‐low‐frequency fire regime, favoring western hemlock over Douglas‐fir.
Response of a Wetland Vascular Plant Community to Disturbance: A Simulation Study
Authors: Ellison Aaron M. , Bedford Barbara L.
Published: April 2006

We developed a spatial computer simulation model of the vascular plant community of a freshwater wetland in south‐central Wisconsin. This model, based on the aggregation of an unwieldy collection of species into a manageable number of functional "species‐types", is used to investigate the responses of wetland plant communities to anthropogenic disturbance that resulted in alterations in wetland hydrology. The results of the model are in general (rank‐order) agreement with 7 yr of observed changes in vegetation structure of a sedge meadow and shallow marsh adjacent to a 1000‐MW coal‐fired power plant near Portage, Wisconsin. Sensitivity analysis of the model revealed that functional species' responses to disturbance depended most heavily on seed germination and dispersal characteristics, a result predicted qualitatively by the wetland succession model of van der Valk (1981). Although analyses of the model presented here appear to verify the model, validation of the model will depend on the collection of similar long‐term data sets at disparate sites. This model may be of use in predicting the consequences of anthropogenic disturbance on other freshwater wetlands.
Engineered Genes in Wild Populations: Fitness of Weed‐Crop Hybrids of Raphanus Sativus
Authors: Klinger Terrie , Ellstrand Norman C.
Published: April 2006

The transfer of engineered genes (transgenes) from crops to natural populations will depend first on mating between the crop and related weeds and then upon the relative fitness of the weed—crop hybrid. While weed—crop hybridization is known to occur readily under agricultural conditions, almost nothing is known of the fitness of the hybrids produced. Therefore, we measured the relative fitness of weedy radishes and their sibling weed—crop hybrids under field conditions. Specifically, we compared germination success, time to first flowering, fruit production, seed production, and frequency of transmission of the crop allele to seed progeny. Hybrids showed significantly greater fruit and seed production, and equaled weeds in all other measured characters. Thus, in this experiment, the fitness of hybrids exceeded that of their wild siblings. These results suggest that, in at least this system, neutral or advantageous transgenes introduced into natural populations will tend to persist.
Vegetation Disturbance and Maintenance of Diversity in Intermittently Flooded Carolina Bays in South Carolina
Authors: Kirkman L. K. , Sharitz R. R.
Published: April 2006

We manipulated the fire regime and soil disturbance in four grass—dominated Carolina bay wetlands during a prolonged drought period and examined vegetation composition and cover within dominant vegetation types prior to and after treatments. We used the seedling emergence technique to determine the role of the seed bank in the recovery process. Burning did not affect richness, evenness, or diversity (all vegetation types combined); however, soil tillage increased diversity, including both evenness and richness. Percent similarity of the vegetation before and after disturbance was greater in the burning treatment than in the tillage treatment, probably due to greater disruption of the rhizomes of the perennial vegetation by tillage. Vegetation types varied in degree of recovery, although dominance was not altered by either treatment. Several native fugitive species increased following disturbance, indicating that species coexistence in these Carolina bay wetlands depends on the life history characteristics of residual vegetation, as well as that of seed bank species. The seed bank (72 600 seedlings/m2) was larger and species richness (108 species) was greater than reported for most other freshwater wetlands. No differences in species richness, evenness, or diversity were detectable among the seed banks associated with different vegetation types in the bays. The floristic composition of the seed bank did not resemble the standing vegetation in patches dominated by large perennial grasses (Panicum hemitomon, Leersia hexandra, and Andropogon virginicus). In contrast, seed bank samples associated with vegetation dominated by an annual forb (Iva microcephala) or the small perennial grasses Panicum wrightianum or P. acuminatum var. unciphyllum more closely reflected the standing vegetation. Species appear to persist with recurring and multiple disturbances because of seed banks, rhizomes, morphological plasticity during inundation, sexual reproduction following inundation, and perenniality coupled with early sexual maturity. Conservation management of intermittently inundated wetlands should incorporate techniques to foster maintenance of endemic species richness and the recruitment of rare species. During periods of drought, it may be desirable to disturb the aggressive perennial vegetation to allow recruitment of less common species.
Management of Tropical Biodiversity
Authors: Lugo Ariel E.
Published: April 2006

Increasing demands for products and services from tropical forests require solutions that conserve biodiversity while responding to human needs. I review various paradigms of tropical forest resiliency and fragility to focus attention on the management of biodiversity. The management of tropical biodiversity is possible within the context of land use programs that focus on ecosystem management. New ecological paradigms of tropical‐forest resiliency underpin tropical‐ecosystem management. They can and/or should replace paradigms that highlighted ecosystem fragility and led to the belief that tropical forests cannot be managed. To lead the way in tropical‐ecosystem management, ecologists must also consider social, political, and economic factors that affect the way people relate to the biota. Ecosystem management will require use of modern technology to mitigate the negative consequences of poor development and land use practices. In spite of efforts to preserve ecosystems as they occur today, species composition of future tropical forest landscapes will be different than today's.
Use of a Native Insect as a Biological Control for an Introduced Weed
Authors: Sheldon Sallie P. , Creed Robert P.
Published: April 2006

We have evaluated the potential of a North American aquatic weevil, Euhrychiopsis lecontei, to serve as an agent of biological control for an exotic weed, Eurasian watermilfoil (Myriophyllum spicatum), which is currently found throughout much of the United States and in some southern provinces of Canada. We have found this weevil on M. spicatum in lakes where populations of the exotic weed have declined. We introduced weevils into enclosures in two lakes dominated by M. spicatum. In both lakes there was 50% less M. spicatum biomass in enclosures with weevils than in enclosures without weevils. Also, in control enclosures, M. spicatum formed a canopy on the water surface as it did outside the enclosures, while there was no plant canopy in any of the weevil enclosures. In laboratory feeding trials we quantified the effects of weevils on ten native aquatic plants including a native watermilfoil, Myriophyllum sibiricum. Weevils did not have a significant effect on the increase in plant length or final dry mass of any native plant, however the weevils did feed on the native watermilfoil. All native plants added new leaves, leaf whorls, or side branches under all weevil densities. The results from these studies suggest that a North American insect may be a suitable control agent for this introduced aquatic weed. Native biological control agents, when they can be found, offer potential advantages over classical biological control agents; they may have little impact on non‐target native species that have coexisted with the control agent, and may save the time and expense of foreign research and quarantine procedures.
The Statistical Evaluation of Ecological Indicators
Authors: Murtaugh Paul A.
Published: April 2006

Ecological indicators are easily measured surrogates for underlying properties or responses of a system that are difficult to measure accurately and reliably. Methods from signal detection theory can be used to assess the usefulness of such indicators, based on pilot data sets in which some gold standard of the underlying response has been measured. For responses that can naturally be dichotomized (e.g., absent vs. present, or acceptable vs. unacceptable), we can estimate an indicator's sensitivity (the probability of a positive indicator, given that the true response is positive) and specificity (the probability of a negative indicator, given that the true responses is negative). These properties, together with the prevalence of the response in the population being studied, determine the indicator's predictive value (e.g., positive predictive value is the probability of a positive response, given that the indicator is positive). Applications of this methodology are described for two examples: the use of satellite imagery to infer oceanic pigment concentrations, and the use of baseline levels of acid‐neutralizing capacity (ANC) to anticipate acidification episodes in lakes and streams.
Assessing Population Responses to Multiple Anthropogenic Effects: A Case Study with Brook Trout
Authors: Marschall Elizabeth A. , Crowder Larry B.
Published: April 2006

Population declines are often caused by multiple factors, including anthropogenic ones that can be mitigated or reversed to enhance population recovery. We used a size‐classified matrix population model to examine multiple anthropogenic effects on a population and determine which factors are most (or least) important to population dynamics. We modeled brook trout (Salvelinus fontinalis) in southern Appalachian mountain streams responding to multiple anthropogenic effects including the introduction of an exotic salmonid species (rainbow trout, Oncorhynchus mykiss), a decrease in pH (through acidic deposition), an increase in siltation (from roadbuilding and logging), and an increase in fishing pressure. Potential brook trout responses to rainbow trout include a decrease in survival rate of small fish, a change in density dependence in survival of small fish, and a decrease in growth rates of all sizes. When we included these responses in the population model, we found that population size tended to decrease with an increase in small‐fish growth rate (producing a population with fewer, but larger, fish). In addition, changes in patterns of density‐dependent survival also had a strong impact on both population size and size structure. Brook trout respond to decreases in pH with decreased growth rate in all size classes, decreased survival rates of small fish, and decreased egg‐to‐larva survival rates. This combination of effects, at magnitudes documented in laboratory experiments, had severe negative impacts on the modeled population. If siltation effects were severe, the extreme increase in egg‐to‐larva mortality could have strong negative effects on the population. However, even very strong increases in large fish mortality associated with sport harvesting were not likely to cause a local extinction. In all of these cases, the interaction of drastic changes in population size structure with randomly occurring floods or droughts may lead to even stronger negative impacts than those predicted from the deterministic model. Because these fish can reproduce at a small size, negative impacts on survival of the largest fish were not detrimental to the persistence of the population. Because survival of small juveniles is density dependent, even moderate decreases in survival in this stage had little effect on the ultimate population size. In general, a brook trout population will respond most negatively to factors that decrease survival of large juveniles and small adults, and growth rates of small juveniles
Integrating Ecology and Economics via Regional Modeling
Authors: Russell Clifford S.
Published: April 2006

This paper identifies two possible meanings for the notion of integration of disciplines: (1) strong, in which the old disciplines are, in effect, merged, and a new discipline emerges using some combination of the insights of the old ones; and (2) weak, in which each discipline continues to use and refine its own paradigm, appropriate to the system it studies, but in which they together create combined models of the interactions between the two systems. I then argue that strong integration will never be possible for ecology and economics but that weak integration is possible, useful in the world of environmental policy development, and intellectually challenging. The meaning and challenges of weak integration are explored further by reference to a multidisciplinary regional environmental modeling exercise of 20 yr ago–the Delaware Estuary Region air and water pollution control model constructed at Resources for the Future. Finally, the problem setting assumed for the Delaware (short‐term, steady‐state, conventional pollutants) is contrasted with the new problems that cry out for integrated modeling (long‐term, stochastic, exotic pollutants with poorly understood chronic effects).
Perspectives on Economics and Ecology
Authors: O'Neill R. V.
Published: April 2006

This paper was prepared as concluding remarks presented at a symposium, Ecological economics: building a new paradigm for sustainability, organized by R. Costanza and R. V. O'Neill and held at the 7‐11 August 1994 annual meeting of the Ecological Society of America.