A process-based model designed for filling of large data gaps in tower-based measurements of net ecosystem productivity

In this paper we present a simple hybrid gap-filling model (GFM) designed with a minimum number of parameters necessary to capture the ecological processes important for filling medium-to-large gaps in Flux data. As the model is process-based, the model has potential to be used in filling large gaps exhibiting a broad range of micro-meteorological and site conditions. The GFM performance was evaluated using “Punch hole” and extrapolation experiments based on data collected in west-central New Brunswick. These experiments indicated that the GFM is able to provide acceptable results (r² > 0.80) when >500 data points are used in model parameterization. The GFM was shown to address daytime evolution of NEP reasonably well for a wide range of weather and site conditions. An analysis of residuals indicated that for the most part no obvious trends were evident; although a slight bias was detected in NEP with soil temperature. To explore the portability of the GFM across ecosystem types, a transcontinental validation was conducted using NEP and ancillary data from seven ecosystems along a north-south transect (i.e., temperature–moisture gradient) from northern Europe (Finland) to the Middle East (Israel). The GFM was shown to explain over 75% of the variability in NEP measured at most ecosystems, which strongly suggests that the GFM maybe successfully applied to forest ecosystems outside Canada.     

The effects of landscape structure on space competition and alternative stable states

Many species that compete for space live on heterogeneous landscapes and interact at local scales. The quality, amount, and structure of landscapes may have considerable impact on the ability of species to compete or coexist, yet basic models of space competition do not include that level of detail. We model space competition between two species with positive feedback through recruitment facilitation, which creates the potential for alternative stable states to occur. We compare the predictions of a spatially implicit model with a simulation model that includes explicit space and landscape structure. We create structured landscapes in which we specify the amount of habitat and degree of fragmentation and ask how landscape structure, dispersal strategy, and scale affect the presence of alternative stable states, or bistability. We find that structured landscapes can reduce the range of parameter values that lead to bistability in our model, but they do not eliminate bistability. The type of landscape and the dispersal distance for each species also influence the amount of environmental change needed for abrupt community shifts to occur. Coexistence of the two competitors is possible under certain conditions when connectivity is low. Consequently, landscape structure may lead to considerable disparity between the predictions of simple models and actual dynamics on complex landscapes during environmental change.     

Use of structured expert judgment to forecast invasions by bighead and silver carp in Lake Erie

Identifying which nonindigenous species will become invasive and forecasting the damage they will cause is difficult and presents a significant problem for natural resource management. Often, the data or resources necessary for ecological risk assessment are incomplete or absent, leaving environmental decision makers ill equipped to effectively manage valuable natural resources. Structured expert judgment (SEJ) is a mathematical and performance‐based method of eliciting, weighting, and aggregating expert judgments. In contrast to other methods of eliciting and aggregating expert judgments (where, for example, equal weights may be assigned to experts), SEJ weights each expert on the basis of his or her statistical accuracy and informativeness through performance measurement on a set of calibration variables. We used SEJ to forecast impacts of nonindigenous Asian carp (Hypophthalmichthys spp.) in Lake Erie, where it is believed not to be established. Experts quantified Asian carp biomass, production, and consumption and their impact on 4 fish species if Asian carp were to become established. According to experts, in Lake Erie Asian carp have the potential to achieve biomass levels that are similar to the sum of biomasses for several fishes that are harvested commercially or recreationally. However, the impact of Asian carp on the biomass of these fishes was estimated by experts to be small, relative to long term average biomasses, with little uncertainty. Impacts of Asian carp in tributaries and on recreational activities, water quality, or other species were not addressed. SEJ can be used to quantify key uncertainties of invasion biology and also provide a decision‐support tool when the necessary information for natural resource management and policy is not available. El Uso de Juicio Experto Estructurado para Predecir Invasiones de Carpas Asiáticas en el Lago Erie     

Ecotoxicity of imidacloprid to soil invertebrates in two tropical soils with contrasting texture

Environmental Science and Pollution Research - Imidacloprid is one of the most commercialized insecticides in agriculture in the world, with a broad spectrum of action. However, little is known...     

Western Land Managers will Need all Available Tools for Adapting to Climate Change,Including Grazing: A Critique of Beschta et al.

In a previous article, Beschta et al. (Environ Manag 51(2):474–491, 2013) argue that grazing by large ungulates (both native and domestic) should be eliminated or greatly reduced on western public lands to reduce potential climate change impacts. The authors did not present a balanced synthesis of the scientific literature, and their publication is more of an opinion article. Their conclusions do not reflect the complexities associated with herbivore grazing. Because grazing is a complex ecological process, synthesis of the scientific literature can be a challenge. Legacy effects of uncontrolled grazing during the homestead era further complicate analysis of current grazing impacts. Interactions of climate change and grazing will depend on the specific situation. For example, increasing atmospheric CO₂ and temperatures may increase accumulation of fine fuels (primarily grasses) and thus increase wildfire risk. Prescribed grazing by livestock is one of the few management tools available for reducing fine fuel accumulation. While there are certainly points on the landscape where herbivore impacts can be identified, there are also vast grazed areas where impacts are minimal. Broad scale reduction of domestic and wild herbivores to help native plant communities cope with climate change will be unnecessary because over the past 20–50 years land managers have actively sought to bring populations of native and domestic herbivores in balance with the potential of vegetation and soils. To cope with a changing climate, land managers will need access to all available vegetation management tools, including grazing.     

Factors affecting vapour production in large scale evaporating liquid cascades

This paper presents a computational fluid dynamics (CFD) model of the evaporating liquid cascade produced in a large hydrocarbon storage tank overfilling incident. The model is first validated against the results of a unique series of full-scale experiments, in which liquid hexane was released from a 10 m high tower. Comparisons are presented for the temperature of both the liquid and vapour in the cascade, and the temperature of the vapour current. The validated model is then used to investigate the effects of different tank bund configurations, and the influence of an accumulating vapour layer on the vapour production process.     

Blast damage to storage tanks and steel clad buildings

The 2005 Buncefield vapour cloud explosion showed the huge cost associated with blast damage to commercial property surrounding a major explosion incident. In most cases there was serious disruption to business activity; in many cases the buildings had to be demolished or abandoned for long periods until extensive repairs were carried out.Another key feature of this and other recent vapour cloud explosions has been the damage done to storage tanks. The blasts almost invariably cause immediate top and bund fires in any tanks surrounded by the vapour – even if they contain relatively high flashpoint materials such as diesel.The first part of this paper describes the patterns of damage observed in buildings in the industrial estates around Buncefield. Methods for assessing the degree of external and internal damage are presented.The second part of the paper deals with failure modes and ignition of various types of liquid storage tank during vapour cloud explosions. Again, the Buncefield data provides excellent examples that illustrate the importance of tank design, fill level, location relative to the cloud, etc.     

Perceptions of Community Benefits from Two Wild and Scenic Rivers

Wild and Scenic Rivers provide a host of psychological, social, ecological, and economic benefits to local communities. In this study, we use data collected from recreational users of two Wild and Scenic Rivers to examine perceptions of the benefits provided by the rivers to local communities. Our purposes are (1) to determine if similar perceptions of community benefits exist across the two rivers, (2) to determine if individuals’ proximity to the rivers are related to the benefits they perceive, (3) to determine if individuals’ prior recreation experience on the river is related to variations in perceived benefits, (4) to determine if users’ sociodemographic characteristics are related to perceived community benefits, and (5) to determine if the influence of these characteristics on perceived community benefits is similar across the two resource areas. Perceived benefits were found to be analogous across both rivers as individuals consistently ranked ecological/affective benefits as well as tangible benefits similarly. Recreationists living further from the river ranked ecological and affective benefits as significantly less important than those individuals living closer to the river. Women perceived the community benefits produced by the resource areas to be significantly more important when compared to men. Significant relationships were also found between perceived benefits and recreationists’ previous use of the river, their age, and their level of education. With the exception of resource proximity and prior use history, the effects of user characteristics on perceived community benefits were not statistically different across the two rivers. These findings imply similar patterns of perceived community benefits exist across distinct resource areas and that the relationships between user characteristics and perceived benefits are also similar across the study rivers.