Measuring the impact of sewage effluent on the macroinvertebrate community of an upland stream: The effect of different levels of taxonomic resolution and quantification

Abstract Benthic macroinvertebrates were sampled from four sites on upland streams in the Wentworth Falls area of the Blue Mountains, NSW. One site received effluent from a sewage treatment plant and the others were reference sites. Five replicate collections were taken from each site on four occasions at intervals of 3 months. Macroinvertebrate community data were analysed using univariate (ANOVA) and multivariate (NMDS) techniques and comparisons were made between analyses at different levels of taxonomic aggregation and using different methods of data transformation. Similar patterns were observed at both species and family levels, and even the order level showed a clear community response to effluent input. Binary (presence/ absence) data provided similar results to quantitative data for the species and family levels. However, when binary data were used at the order level, the distinctions between the reference sites became blurred. We discuss the implications of these findings for environmental monitoring.     

Rapid assessment of rivers using macroinvertebrates: A procedure based on habitat-specific sampling,family level identification and a biotic index

Abstract This paper describes a simple and inexpensive procedure for the rapid biological assessment of water quality in rivers and streams in eastern Australia. The procedure involves the standardized collection of samples of 100 macroinvertebrates from defined habitat types within a water body. Specimens are identified to family level only and a biotic index is calculated. Proposed future testing and evaluation are described, and the limitations of the rapid approach are discussed.     

Environmental and economic analysis of the fully integrated biorefinery

Cellulosic biofuel systems have the potential to significantly reduce the environmental impact of the world's transportation energy requirements. However, realizing this potential will require systems level thinking and scale integration. Until now, we have lacked modeling tools for studying the behavior of integrated cellulosic biofuel systems. In this paper, we describe a new research tool, the Biorefinery and Farm Integration Tool (BFIT) in which the production of fuel ethanol from cellulosic biomass is integrated with crop and animal (agricultural) production models. Uniting these three subsystems in a single combined model has allowed, for the first time, basic environmental and economic analysis of biomass production, possible secondary products, fertilizer production, and bioenergy production across various regions of the United States. Using BFIT, we simulate cellulosic ethanol production embedded in realistic agricultural landscapes in nine locations under a collection of farm management scenarios. This combined modeling approach permits analysis of economic profitability and highlights key areas for environmental improvement. These results show the advantages of introducing integrated biorefinery systems within agricultural landscapes. This is particularly true in the Midwest, which our results suggest is a good setting for the cellulosic ethanol industry. Specifically, results show that inclusion of cellulosic biofuel systems into existing agriculture enhances farm economics and reduces total landscape emissions. Model results also indicate a limited ethanol price effect from increased biomass transportation distance. Sensitivity analysis using BFIT revealed those variables having the strongest effects on the overall system performance, namely: biorefinery size, switchgrass yield, and biomass farm gate price.     

Disturbance, rainfall and contrasting species responses mediated aboveground biomass response to 11 years of CO2 enrichment in a Florida scrub-oak ecosystem

This study reports the aboveground biomass response of a fire-regenerated Florida scrub-oak ecosystem exposed to elevated CO₂ (1996–2007), from emergence after fire through canopy closure. Eleven years exposure to elevated CO₂ caused a 67% increase in aboveground shoot biomass. Growth stimulation was sustained throughout the experiment; although there was significant variability between years. The absolute stimulation of aboveground biomass generally declined over time, reflecting increasing environmental limitations to long-term growth response. Extensive defoliation caused by hurricanes in September 2004 was followed by a strong increase in shoot density in 2005 that may have resulted from reopening the canopy and relocating nitrogen from leaves to the nutrient-poor soil. Biomass response to elevated CO₂ was driven primarily by stimulation of growth of the dominant species, Quercus myrtifolia , while Quercus geminata , the other co-dominant oak, displayed no significant CO₂ response. Aboveground growth also displayed interannual variation, which was correlated with total annual rainfall. The rainfall × CO₂ interaction was partially masked at the community level by species-specific responses: elevated CO₂ had an ameliorating effect on Q. myrtifolia growth under water stress. The results of this long-term study not only show that atmospheric CO₂ concentration had a consistent stimulating effect on aboveground biomass production, but also showed that available water is the primary driver of interannual variation in shoot growth and that the long-term response to elevated CO₂ may have been caused by other factors such as nutrient limitation and disturbance.     

Interactions between plant growth and soil nutrient cycling under elevated CO2: a meta-analysis

free air carbon dioxide enrichment (FACE) and open top chamber (OTC) studies are valuable tools for evaluating the impact of elevated atmospheric CO₂ on nutrient cycling in terrestrial ecosystems. Using meta‐analytic techniques, we summarized the results of 117 studies on plant biomass production, soil organic matter dynamics and biological N₂ fixation in FACE and OTC experiments. The objective of the analysis was to determine whether elevated CO₂ alters nutrient cycling between plants and soil and if so, what the implications are for soil carbon (C) sequestration. Elevated CO₂ stimulated gross N immobilization by 22%, whereas gross and net N mineralization rates remained unaffected. In addition, the soil C : N ratio and microbial N contents increased under elevated CO₂ by 3.8% and 5.8%, respectively. Microbial C contents and soil respiration increased by 7.1% and 17.7%, respectively. Despite the stimulation of microbial activity, soil C input still caused soil C contents to increase by 1.2% yr^?1. Namely, elevated CO₂ stimulated overall above‐ and belowground plant biomass by 21.5% and 28.3%, respectively, thereby outweighing the increase in CO₂ respiration. In addition, when comparing experiments under both low and high N availability, soil C contents (+2.2% yr^?1) and above‐ and belowground plant growth (+20.1% and+33.7%) only increased under elevated CO₂ in experiments receiving the high N treatments. Under low N availability, above‐ and belowground plant growth increased by only 8.8% and 14.6%, and soil C contents did not increase. Nitrogen fixation was stimulated by elevated CO₂ only when additional nutrients were supplied. These results suggest that the main driver of soil C sequestration is soil C input through plant growth, which is strongly controlled by nutrient availability. In unfertilized ecosystems, microbial N immobilization enhances acclimation of plant growth to elevated CO₂ in the long‐term. Therefore, increased soil C input and soil C sequestration under elevated CO₂ can only be sustained in the long‐term when additional nutrients are supplied.     

Agrarian legacy in soil nutrient pools of urbanizing arid lands

Today's worldwide expansion of dry land cities consumes cultivated and native ecosystems, providing laboratories for investigating imprints of former land use in places where people now live. Around Phoenix, USA, we compared soil nutrient pools in residential yards converted from farms with nutrient pools in yards developed on native desert. Organic matter, carbon (C), nitrogen (N), and soluble ions were >2-fold greater in yards that were previously agrarian than in yards that were not. These pools remain elevated 40 years after land conversion to residential use. Present N accumulation (1.5 g m⁻² yr⁻¹) is not affected by prior land use, suggesting that rates of residential fertilizer application and retention are not affected by antecedent soil fertility. Bioavailable, inorganic phosphorus (P_av) is elevated in soil with a recent agrarian past, but this signal disappears after 10–30 years of residential use owing to an accumulation of P_av in never-farmed yards. Our results indicate a 'direct agrarian legacy,' wherein agrarian amendment of nutrient pools endures urbanization, more so than an 'indirect legacy,' wherein present land management is molded by former land use. Agriculture in dry lands thus sequesters material in soils, and—as we also found higher material contents in residential soils than in contemporary agrarian soils—residential land use simply adds to the agrarian legacy these soils already bear. Intense human use of arid lands may cause increases in material pools in soils, a condition with potential global consequence.     

The influence of microhabitat on availability of drifting invertebrate prey to a net-spinning caddisfly

SUMMARY. 1. Invertebrate drift was sampled at both a rockface and a deep pebble riffle site in streams draining both a clearcut and a forested catchment.
2. A sampler was designed to separate the bottom 2 cm of flow, encompassing the effective range of caddisfly (Hydropsychidae: Trichoptera) catchnets. from upper flow.
3. No significant difference in drift density (numbers per cubie metre) was seen between sites within each stream. However, numbers per square centimetre intake area per day at the rockface sites were 4 times higher in the clearcut and 10 times higher in the forested stream than at the pebble-riffle site.
4. Rockface habitat which had highest drift availability was also the site of maximum secondary production of the predaceous collector- filterer Parapsyche cardis in both streams studied.
5. Increased sediment load in the clearcut stream may influence the efficiency of utilization of invertebrate drift by collector-filterers.     

Myxomycetes from the Kimberley Region, Western Australia

An account of the Myxomycetes of the Kimberley Region of north Western Australia is presented. It is based on collections obtained mainly from the Napier and Oscar Ranges during the Kimberley Research Project, 1988. The thirty-two collections represent eighteen species, four of which are new records for Australia and twelve new to Western Australia. All but one are new to the Kimberley region, from where only four species were previously known.