Insect herbivory and propagule pressure influence Cirsium vulgare invasiveness across the landscape

A current challenge in ecology is to better understand the magnitude, variation, and interaction in the factors that limit the invasiveness of exotic species. We conducted a factorial experiment involving herbivore manipulation (insecticide-in-water vs. water-only control) and seven densities of introduced nonnative Cirsium vulgare (bull thistle) seed. The experiment was repeated with two seed cohorts at eight grassland sites uninvaded by C. vulgare in the central Great Plains, USA. Herbivory by native insects significantly reduced thistle seedling density, causing the largest reductions in density at the highest propagule inputs. The magnitude of this herbivore effect varied widely among sites and between cohort years. The combination of herbivory and lower propagule pressure increased the rate at which new C. vulgare populations failed to establish during the initial stages of invasion. This experiment demonstrates that the interaction between biotic resistance by native insects, propagule pressure, and spatiotemporal variation in their effects were crucial to the initial invasion by this Eurasian plant in the western tallgrass prairie.     

Jamaica in the World Aluminum Industry, 1938–1973: Carlton E. Davis Jamaica Bauxite Institute, Kingston, 1989, $20.00

The Climax molybdenum mine, once dominant in a burgeoning molybdenum market, is now beset with a cyclical market showing little secular growth, lower prices from growing byproduct production, the development of other lower cost primary mines and idle capacity. It has abandoned its resources and closed most of its operations.     

Spatial Distribution of Soil Attributes in the Concórdia River Watershed in Southern Brazil

Using geographic information system, soil sampling, and statistical analysis to map anthropogenic effects on soil     

Bedded Sediment Conditions and Macroinvertebrate Responses in New Mexico Streams: A First Step in Establishing Sediment Criteria

Excess fine sediments in streambeds are among the most pervasive causes of degradation in streams of the United States. Simple criteria for acceptable streambed fines are elusive because streambed fines and biotic tolerances vary widely in the absence of human disturbances. In response to the need for sediment benchmarks that are protective of minimum aquatic life uses under the Clean Water Act, we undertook a case study using surveys of sediment, physical habitat, and macroinvertebrates from New Mexico streams. Our approach uses weight of evidence to develop suggested benchmarks for protective levels of surficial bedded sediments <0.06 mm (silt and finer) and <2.0 mm (sand and finer). We grouped streams into three ecoregions that were expected to produce similar naturally occurring streambed textures and patterns of response to human disturbances. Within ecoregions, we employed stressor response models to estimate fine sediment percentages and bed stability that are tolerated by resident macroinvertebrates. We then compared individual stream sediment data with distributions among least‐disturbed reference sites to determine deviation from natural conditions, accounting for natural variability across ecoregion, gradient, and drainage area. This approach for developing benchmark values could be applied more widely to provide a solid basis for developing bedded sediment criteria and other protective management strategies in other regions.     

Miniaturized test system for soil respiration induced by volatile pollutants

A miniaturized method based on 96-well microtitre plates was developed and used to study respiration in pristine and contaminated soils following addition of volatile substrates. Small soil samples were exposed to fuel components, which were volatilized from spatially separate reservoirs of 2,2,4,4,6,8,8-heptamethylnonane (HMN) as an organic carrier. Respiration was determined as CO(2) production by means of a pH-indicator and bicarbonate-containing agar, or as (14)CO(2) evolution from (14)C-labelled substrates. Substrate concentrations inducing maximum microbial activity or inhibition were determined and CO(2) production profiles examined by multivariate analysis. When high concentrations of fuel components were applied, distinction of hydrocarbon exposed soils from unexposed soil was achieved within 6 h of incubation. With low concentrations, adequate distinction was achieved after 24 h, probably as a result of community adaptation. Nutrient limitation was identified with the (14)C method for toluene, and the optimal N and P amendment determined. Further potential applications of this rapid and inexpensive method are outlined.     

Batch-test study on the dechlorination of 1,1,1-trichloroethane in contaminated aquifer material by zero-valent iron

Chlorinated aliphatic hydrocarbons are common groundwater contaminants. One possible remediation option is in-situ reductive dechlorination by zero-valent iron, either by direct injection or as reactive barriers. Chlorinated ethenes (tetrachloroethene: PCE; trichloroethene: TCE) have received extensive attention in this context. However, another common groundwater pollutant, 1,1,1-trichlorethane (TCA), has attracted much less attention. We studied TCA reduction by three types of granular zero-valent irons in a series of batch experiments using polluted groundwater, with and without added aquifer material. Two types of iron were able to reduce TCA completely with no daughter product concentration increases (1,1-dichloroethane: DCA; chloroethane: CA). One type of iron showed slower reduction, with intermediate rise of DCA and CA concentrations. When evaluating the formation of daughter products, the tests on the groundwater alone showed different results than the groundwater plus aquifer batches: DCA did not temporarily accumulate in the batches with added aquifer material, contrary to the batches without added aquifer material. 1,1-dichloroethene (DCE, also present in the groundwater as an abiotic degradation product of TCA) was also reduced slower in the batches without added aquifer material than in the batches with aquifer material. Redox potentials gradually decreased to low values in batches with aquifer material without iron, while the batches with groundwater alone maintained a constant higher redox potential. Either adsorption processes or microbiological activity in the samples could explain these phenomena. Polymerase Chain Reaction (PCR: a targeted gene probe technique) for chlorinated aliphatic compound (CAH)-degrading bacteria confirmed the presence of Dehalococcoides sp. (chloroethene-degraders) but was negative for Desulfobacterium autotrophicum (a known co-metabolic TCA degrader). DCA reduction was rate determining: first-order half-lives of 300-350 h were observed. TCA was fully removed within hours. CA is resistant to reduction by zero-valent iron but it is known to hydrolyze easily. Since CA did not accumulate in our batches, it may have disappeared by the latter mechanism or it may not have formed as a major daughter product.     

Correction to: The time of concentration application in studies around the world: a review

Environmental Science and Pollution Research -