Simulating dynamic and mixed-severity fire regimes: A process-based fire extension for LANDIS-II

Fire regimes result from reciprocal interactions between vegetation and fire that may be further affected by other disturbances, including climate, landform, and terrain. In this paper, we describe fire and fuel extensions for the forest landscape simulation model, LANDIS-II, that allow dynamic interactions among fire, vegetation, climate, and landscape structure, and incorporate realistic fire characteristics (shapes, distributions, and effects) that can vary within and between fire events. We demonstrate the capabilities of the new extensions using two case study examples with very different ecosystem characteristics: a boreal forest system from central Labrador, Canada, and a mixed conifer system from the Sierra Nevada Mountains (California, USA). In Labrador, comparison between the more complex dynamic fire extension and a classic fire simulator based on a simple fire size distribution showed little difference in terms of mean fire rotation and potential severity, but cumulative burn patterns created by the dynamic fire extension were more heterogeneous due to feedback between fuel types and fire behavior. Simulations in the Sierra Nevada indicated that burn patterns were responsive to topographic features, fuel types, and an extreme weather scenario, although the magnitude of responses depended on elevation. In both study areas, simulated fire size and resulting fire rotation intervals were moderately sensitive to parameters controlling the curvilinear response between fire spread and weather, as well as to the assumptions underlying the correlation between weather conditions and fire duration. Potential fire severity was more variable within the Sierra Nevada landscape and also was more sensitive to the correlation between weather conditions and fire duration. The fire modeling approach described here should be applicable to questions related to climate change and disturbance interactions, particularly within locations characterized by steep topography, where temporally or spatially dynamic vegetation significantly influences spread rates, where fire severity is variable, and where multiple disturbance types of varying severities are common.     

Database-driven models of the world's Large Marine Ecosystems

We present a new methodology for database-driven ecosystem model generation and apply the methodology to the world's 66 currently defined Large Marine Ecosystems. The method relies on a large number of spatial and temporal databases, including FishBase, SeaLifeBase, as well as several other databases developed notably as part of the Sea Around Us project. The models are formulated using the freely available Ecopath with Ecosim (EwE) modeling approach and software. We tune the models by fitting to available time series data, but recognize that the models represent only a first-generation of database-driven ecosystem models. We use the models to obtain a first estimate of fish biomass in the world's LMEs. The biggest hurdles at present to further model development and validation are insufficient time series trend information, and data on spatial fishing effort.     

Determine the most influencing stressors and the most susceptible resources for environmental integrated assessment

The paper presents a method to determine the most influencing stressors and the most susceptible resources for complex assessment problems involving multiple stressors impacting multiple resources over a region. The method is based on the concept of limiting priorities in a square matrix which capture the transmission of influence along all paths between stressors and resources in the matrix. The proposed method allows the relationship between stressors and resources to be looked at in both univariate and multivariate fashion, taking into account the interactions among the variables. Hypothetical and case study examples are given for illustration purpose. It shows that the proposed method is suitable for the determination of the most important stressors and the most susceptible resources, a common (but often uneasy) task in integrated environmental assessment.     

(Z)-Dodec-3-en-1-ol, a common major component of the trail-following pheromone in the termites Kalotermitidae

(Z)-Dodec-3-en-1-ol has been identified as the major component of the trail-following pheromone of nine species of Kalotermitidae belonging to six different genera, suggesting that this compound represents a common signal in this family of termites. The homogeneous nature of trail-following pheromones of Kalotermitidae well agrees with the monophyly of this family. It also supports the postulated position of this family as a sister group of the Rhinotermitidae and Termitidae, which also secrete C12-alcohols as trail-following pheromones. The significance of a trail pheromone in termites of the ‘one-piece’ life type, which spend their whole life within the same piece of wood, is discussed.     

Heavy metal distribution in soils near Palapye, Botswana: an evaluation of the environmental impact of coal mining and combustion on soils in a semi-arid region

Morupule Colliery near Palapye in eastern Botswana is the only coalmine in production in Botswana at present. Its coal is mainly used in the nearby coal-fired Morupule Power Station, which generates approximately 1,000 GWh of electricity per annum. After more than 30 years mining and more than 20 years of combustion, the sedimentation of outlet fly ash from the Morupule Power Station has increased concentrations of Cr, Ni, Zn and As by 13, 2.5, 16 and 5 ppm, respectively, in the fine portion (<53 μm) of surface soils for approximately 9 km downwind. Elements that have higher concentrations in coal have stronger small-particle association during coal combustion and are less mobile in surface soils, thus showing stronger contaminations in surface soils around the coal-fired plant. Although the degree of contamination of Cr, Ni, Zn and As from coal combustion in the Palapye area at present is low, it is necessary to monitor concentrations of these elements in surface soils routinely in the future. This study also reveals moderate Pb and Zn contaminations in the Palapye area. The former is due to the use of leaded petroleum in motor vehicle traffic and the latter is mainly due to the use of galvanized iron sheets in construction.     

A multiple motive perspective on strike propensities

Strike propensities refer to the extent to which union members are willing to engage in strikes. The present paper identifies four motivational explanations for individual propensity to strike: social exchange relationships between member and union, and member and company, economic circumstances, and social status. These four models complement each other, and together permit substantial integration of previous literature as well as suggesting new antecedents of strike propensities. We evaluated each model using survey data from 2548 unionized retail employees. While the economic model explained the most variance in strike propensity, each model accounted for a significant amount of unique variation in the members' strike propensities. Our organizational framework of the motivational explanations of strike propensity into four distinct but complementary motivational models and our addition of new predictor variables represent our study's major contributions. Implications for strike research and union member–union relations are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

TEN YEARS OF VEGETATION SUCCESSION ON A DEBRIS‐FLOW DEPOSIT IN OREGON1

ABSTRACT: We tracked vegetation succession on a debris‐flow deposit in Oregon's Coast Range to examine factors influencing the development of riparian plant communities following disturbance. Plots were stratified across five areas of the deposit (bank slump, seep, upper and lower sediment wedge, log jam) the first growing season after debris flow. At six times during the next ten years we estimated cover of vascular plants and tallied density of woody plants. Plant colonization occurred within two years. Total cover increased two‐to seven‐fold on the five areas within three years. Red alder and salmonberry were the dominant species, although weedy herbs persisted where woody species were lacking. Ordination of cover data showed that the five areas remained floristically distinct over time, while undergoing similar shifts related to the increasing dominance of alder and salmonberry. Rapid height growth of alder allowed it to outcompete salmonberry and effectively capture most areas by the tenth year, even where sprouts from transported rhizomes gave salmonberry an early advantage. Our results suggest that successional patterns were influenced by substrate variability, species composition of initial colonizers, propagule sources and their distribution, and species life‐history traits such as growth rate, competitive ability, and shade tolerance.     

USING REFERENCE SITES AND SIMPLE LINEAR REGRESSION TO ESTIMATE LONG‐TERM WATER LEVELS IN COASTAL PLAIN FORESTS1

ABSTRACT: The ability of regulators, resource managers, and consultants to assess accurately wetland hydrology is crucial when identifying and delineating wetlands. In this study, simple linear regression and long‐term (ten year) New Jersey Pinelands stream gaging and pitch pine lowland water‐level data sets were used to estimate long‐term hydroperiods at lowland test sites with short‐term (two year) records. Separate regression equations were developed for each test site using reference site data and stream gaging data, and two sets of equations for selected test sites were produced using two different short‐term periods of record. Test sites had long‐term records ranging from four to ten years, allowing validation of the regression models. Measured and predicted test site growing season water levels were similar regardless of which short‐term period of record was used. The results based on the stream gaging site data were similar, although the difference between measured and estimated growing season water levels was greater when this approach was used. Excellent agreement was found between measured and estimated frequencies of near‐surface saturation at test sites for each growing season month, and these relationships improved when cumulative, seasonal frequencies were considered. The reference wetland approach used in this study may have its greatest value in regions with both high development pressures and problem wetlands and may provide an effective way of resolving costly wetland delineation disputes.     

Intrinsic Value and Direct Duties: From Animal Ethics towards Environmental Ethics?

Three types of concern for animal welfare are widelyheld: Animals should feel well, they should function well, andthey should lead natural lives. The paper deals with a well-knownanswer to the question of why such concerns are morallyappropriate: Human beings have direct duties towards animals,because animals are beings that can flourish, the flourishing ofanimals is intrinsically or inherently valuable, and that whichis conducive to their flourishing is a legitimate object of moralconcern. Looking for a tenable conception of direct dutiestowards animals, the following questions are discussed: Whatshould we take it to mean that ``animal flourishing isintrinsically or inherently valuable?'' Under what conditions doesa living being's ability to flourish create direct duties towardsthis being? Is awareness or sentience required for there to bedirect duties towards a living being? Does such a requirementimply that moral concerns for animals would be limited to theirfeeling well, or does it also give way to having moral concernsfor their functioning well and leading natural lives? Can onetake into account considered judgements that claim that towardsdifferent animals we have moral duties that differ in kind and/orstrength? If environmental ethics cannot be based on theconception of direct duties here discussed, should one draw adistinction between duties towards ourselves, our fellow humanbeings, or animals, and duties regarding plants, or collectiveentities such as populations, species, and ecosystems?