Do Postfire Mulching Treatments Affect Plant Community Recovery in California Coastal Sage Scrub Lands?

In recent years, the use of postfire mulch treatments to stabilize slopes and reduce soil erosion in shrubland ecosystems has increased; however, the potential effects on plant recovery have not been examined. To evaluate the effects of mulching treatments on postfire plant recovery in southern California coastal sage scrub, we conducted a field experiment with three experimental treatments, consisting of two hydromulch products and an erosion control blanket, plus a control treatment. The area burned in 2007, and treatments were applied to six plot blocks before the 2008 growing season. Treatment effects on plant community recovery were analyzed with a mixed effects ANOVA analysis using a univariate repeated measures approach. Absolute plant cover increased from 13 to 90% by the end of the second growing season, and the mean relative cover of exotic species was 32%. The two hydromulch treatments had no effect on any plant community recovery response variable measured. For the erosion control blanket treatment, the amount of bare ground cover at the end of the second growing season was significantly lower (P = 0.01), and greater shrub height was observed (P < 0.01). We conclude that postfire mulch treatments did not provide either a major benefit or negative impact to coastal sage scrub recovery on the study area.     

Emission reductions from woody biomass waste for energy as an alternative to open burning

Woody biomass waste is generated throughout California from forest management, hazardous fuel reduction, and agricultural operations. Open pile burning in the vicinity of generation is frequently the only economic disposal option. A framework is developed to quantify air emissions reductions for projects that alternatively utilize biomass waste as fuel for energy production. A demonstration project was conducted involving the grinding and 97-km one-way transport of 6096 bone-dry metric tons (BDT) of mixed conifer forest slash in the Sierra Nevada foothills for use as fuel in a biomass power cogeneration facility. Compared with the traditional open pile burning method of disposal for the forest harvest slash, utilization of the slash for fuel reduced particulate matter (PM) emissions by 98% (6 kg PM/BDT biomass), nitrogen oxides (NOx) by 54% (1.6 kg NOx/BDT), nonmethane volatile organics (NMOCs) by 99% (4.7 kg NMOCs/BDT), carbon monoxide (CO) by 97% (58 kg CO/BDT), and carbon dioxide equivalents (CO2e) by 17% (0.38 t CO2e/BDT). Emission contributions from biomass processing and transport operations are negligible. CO2e benefits are dependent on the emission characteristics of the displaced marginal electricity supply. Monetization of emissions reductions will assist with fuel sourcing activities and the conduct of biomass energy projects.     

The Recovery of Ammonia and Hydrogen Sulflde from Ground-Level Area Sources Using Dynamic Isolation Flux Chambers: Bench-Scale Studies

Abstract

Controlled bench-scale laboratory experiments were conducted to evaluate the recovery of ammonia (NH₃) and hydrogen sulflde (H₂S) from dynamic isolation flux chambers. H₂S (80–4000 ppb) and NH₃ (5000–40,000 ppb) samples were diffused through the flux chamber to simulate ground level area source emissions while measuring the inlet and outlet flux chamber concentrations simultaneously. Results showed that the recovery of H₂S during a 30-min sampling time was almost complete for concentrations >2000 ppb. At the lowest concentration of 80 ppb, 92.55% of the H₂S could be recovered during the given sampling period. NH₃ emissions exhibited similar behavior between concentrations of 5000–40,000 ppb. Within the 30-min sampling period, 92.62% of the 5000-ppb NH₃ sample could be recovered. Complete recovery was achieved for concentrations >40,000 ppb. Predictive equations were developed for gas adsorption. From these equations, the maximum difference between chamber inlet and outlet concentrations of NH₃ or H₂S was predicted to be 7.5% at the lowest concentration used for either gas. In the calculation of emission factors for NH₃ and H₂S, no adsorption correction factor is recommended for concentrations >37,500 ppb and 2100 ppb for NH₃ and H₂S, respectively. The reported differences in outlet and inlet concentration above these ranges are outside the full-scale sensitivity of the gas sensing equipment. The use of 46–90 m of Teflon tubing with the flux chambers has apparently no effect on gas adsorption, because recovery was completed almost instantaneously at the beginning of the tests.     

A Comparison Study of Various Types of Ozone and Oxidant Detectors Which Are Used for Atmospheric Air Sampling

Four continuous automatic analyzers for measurement of atmospheric levels of ozone were used in a calibration and field study. These were (1) a colorimetric instrument based upon detection of iodine released from neutral potassium iodide reagent, {2) a coulometric instrument utilizing the polarization current as a measurement of iodine released by ozone in a cell contacted by potassium iodide reagent, (8) a galvanic cell measuring bromine release by ozone, and (4) an ultraviolet photometer. Some ozone determinations by the manual rubber cracking procedure were included. After calibration with ozone the average relative response to atmospheric ozone levels for each instrument was determined using the colorimetric oxidant analyzer as an arbitrary standard. These responses ranged from 77 percent for the galvanic cell 90 percent for the photometer. The instrument of choice for any given application would seem to be governed by requirements for precision specificity, portability, reliability, and ease of operation.     

Site-specific water quality guidelines: 1. Derivation approaches based on physicochemical, ecotoxicological and ecological data

Generic water quality guidelines (WQGs) are developed by countries/regions as broad scale tools to assist with the protection of aquatic ecosystems from the impacts of toxicants. However, since generic WQGs cannot adequately account for the many environmental factors that may affect toxicity at a particular site, site-specific WQGs are often needed, especially for high environmental value ecosystems. The Australian and New Zealand Guidelines for Fresh and Marine Water Quality provide comprehensive guidance on methods for refining or deriving WQGs for site-specific purposes. This paper describes three such methods for deriving site-specific WQGs, namely: (1) using local reference water quality data, (2) using biological effects data from laboratory-based toxicity testing, and (3) using biological effects data from field surveys. Two case studies related to the assessment of impacts arising from mining operations in northern Australia are used to illustrate the application of these methods. Finally, the potential of several emerging methods designed to assess thresholds of ecological change from field data for deriving site-specific WQGs is discussed. Ideally, multiple lines of evidence approaches, integrating both laboratory and field data, are recommended for deriving site-specific WQGs.     

Use of toxicity identification evaluations to determine the pesticide mitigation effectiveness of on-farm vegetated treatment systems

Evidence of ecological impacts from pesticide runoff has prompted installation of vegetated treatment systems (VTS) along the central coast of California, USA. During five surveys of two on-farm VTS ponds, 88% of inlet and outlet water samples were toxic to Ceriodaphnia dubia. Toxicity identification evaluations (TIEs) indicated water toxicity was caused by diazinon at VTS-1, and chlorpyrifos at VTS-2. Diazinon levels in VTS-1 were variable, but high pulse inflow concentrations were reduced through dilution. At VTS-2, chlorpyrifos concentrations averaged 52% lower at the VTS outlet than at the inlet. Water concentrations of most other pesticides averaged 20-90% lower at VTS outlets. All VTS sediment samples were toxic to amphipods (Hyalella azteca). Sediment TIEs indicated toxicity was caused by cypermethrin and lambda-cyhalothrin at VTS-1, and chlorpyrifos and permethrin at VTS-2. As with water, sediment concentrations were lower at VTS outlets, indicating substantial reductions in farm runoff pesticide concentrations.     

Accumulation of lead by the lichen

Summary The lichen Stereocaulon dactylophyllum,occurring on a metalliferous spoil tip, was found to accumulate various elements within parts of the apothecium, such as the subhymenium and the fertile hymenium. The hymenium was particularly contaminated by lead, and this may subsequently affect ascospore viability. Certain elements were present on the external surface of the thalli and apothecia; the percentage composition of the elements within the apothecium differed from that on the outside of the apothecium. Fourteen elements were recorded from samples of the metalliferous spoil, the subhymenium and the hymenium; the ranking of elements varied in the samples as also did the percentage contributions of the various elements. The lichen is an important accumulator of elements derived from various sources, including the atmospheric transport of particulates emanating from the spoil tip. It may be speculated that the elements, including the toxic ones, will subsequently be accumulated within organisms belonging to various trophic levels; rotifers which are present on both the apothecia and thalli are likely to be affected. Dr F. Brian Pyatt is Head of the Ecology Section in the Department of Life Sciences at Nottingham Polytechnic, where Mr D. Lacy is a member of the Department of Chemistry and Physics. Mr E.H. Beaumont was until recently in the Department of Zoology at the University of Oxford, and Mr D.M. Storey is a member of the Department of Biological Sciences at the University of Salford, UK.     

Constructing Interpretable Environments from Multidimensional Data: GIS Suitability Overlays and Principal Component Analysis

In landscape planning applications, practitioners and governmental agencies are often faced with a broad array of clientele and constituents having particular land use requirements and needs, ranging from biological conservation to urban development, generating complex multidimensional regional planning goals and objectives. Under this often complex situation, investigators are searching for methods to intelligently simplify complicated spatial environments and render them into interpretable and practical settings. While numerous investigators have studied the generation of a single suitability map, we were interested in addressing the problem of coping with a set of many suitability maps. We applied a data reduction method, principal component analysis, across 15 suitability overlays representing diverse landscape requirements to search for simplified explanations indicating the latent structure of the landscape. The study area was located in a moraine landscape of southern Michigan. We discovered that the 15 suitability overlays could be reduced to seven dimensions, containing 65% of the original data structure and that the seven dimensions reflect a structure where a variety of land uses each have their own optimal spatial locations, indicating low to moderate competition between potentially conflicting land uses and rendering a more easily understood environment. This approach did not render a simple elegant solution but it did reduce the complexity associated with combining many suitability maps.     

Ecological role for pteroenone,a novel antifeedant from the conspicuous antarctic pteropod Clione antarctica (Gymnosomata: Gastropoda)

Dense populations of the antarctic pteropod Clione antarctica (Smith) offer a rich source of potential nutrients and energy to planktivorous predators. Nonetheless, antarctic fish do not prey on C. antarctica. Employing flash and high-pressure liquid chromatographic techniques, a linear -hydroxyketone, pteroenone (C₁₄H₂₄O₂) was isolated from whole tissues of C. antarctica. When embedded in alginate food pellets at ecologically relevant concentrations, pteroenone caused significant feeding deterrence in Pagothenia borchgrevinki and Pseudotrematomas bernacchii, two antarctic fish known to feed on planktonic organisms. Concentrations of pteroenone were variable between pteropods (0.056 to 4.5 mg ml^-1 tissue), but even those individuals with the lowest natural concentration contained levels five-fold greater than the lowest effective feeding-deterrent concentration (0.012 mg ml^-1 alginate). Chemical analysis indicated that the primary dietary item of the carnivorous C. antarctica, the shelled pteropod Limacina helicina, does not contain pteroenone. This suggests that C. antarctica does not derive this defensive compound from its diet. This is the first example of a defensive secondary metabolite in a pelagic gastropod.     

A knowledge-based approach to regional acidification modelling

Data from over 2000 stations and knowledge from experts on atmospheric transport, soil geochemistry, lake chemistry, wetland processes and acidification modelling were assembled in an expert system. The data were grouped by aggregates of tertiary watersheds based on water chemistry knowledge. A set of expert rules was used to determine which of six existing models was most appropriate for a given set of data. Comparison of computed and observed alkalinity indicated median relative errors from 11.3–17.9%, with regression slopes ranging from 0.91–1.18 and regression coefficients between 0.82 and 0.99. The expert model performance was further confirmed with paleolimnological data and other independent sets of data. The sensitivity of the predicted alkalinity was illustrated by changing some of the rules. Given that the rules were acceptable by experts and produced reasonable agreement with observations, the knowledge-based system seemed a viable approach to the impact assessment of acidic deposition.