Plant winners and losers during grassland N-eutrophication differ in biomass allocation and mycorrhizas

Human activities release tremendous amounts of nitrogenous compounds into the atmosphere. Wet and dry deposition distributes this airborne nitrogen (N) on otherwise pristine ecosystems. This eutrophication process significantly alters the species composition of native grasslands; generally a few nitrophilic plant species become dominant while many other species disappear. The functional equilibrium model predicts that, compared to species that decline in response to N enrichment, nitrophilic grass species should respond to N enrichment with greater biomass allocation aboveground and reduced allocation to roots and mycorrhizas. The mycorrhizal feedback hypothesis states that the composition of mycorrhizal fungal communities may influence the composition of plant communities, and it predicts that N enrichment may generate reciprocal shifts in the species composition of mycorrhizal fungi and plants. We tested these hypotheses with experiments that compared biomass allocation and mycorrhizal function of four grass ecotypes (three species), two that gained and two that lost biomass and cover in response to long-term N enrichment experiments at Cedar Creek and Konza Long-Term Ecological Research grasslands. Local grass ecotypes were grown in soil from their respective sites and inoculated with whole-soil inoculum collected from either fertilized (FERT) or unfertilized (UNFERT) plots. Our results strongly support the functional equilibrium model. In both grassland systems the nitrophilic grass species grew taller, allocated more biomass to shoots than to roots, and formed fewer mycorrhizas compared to the grass species that it replaced. Our results did not fully support the hypothesis that N-induced changes in the mycorrhizal fungal community were drivers of the plant community shifts that accompany N eutrophication. The FERT and UNFERT soil inoculum influenced the growth of the grasses differently, but this varied with site and grass ecotype in both expected and unexpected ways suggesting that ambient soil fertility or other factors may be interacting with mycorrhizal feedbacks.     

Mercury in rivers in NW England: from rural headwaters to the heartlands of the historic industrial base

Total mercury (T-Hg) concentrations in rivers are described across a rural to urban/industrial and agricultural landscape gradient in NW England. T-Hg ranges between 0.2 and 230 ng L(-1). The regional median was 3.6 ng L(-1) with individual river medians ranging between 1.9 and 8.3 ng L(-1). Median T-Hg concentrations were sometimes moderately higher for the lowland areas and at higher flows. Our estimates suggest that the Ribble estuary receives 9.2 kg y(-1) and the Wyre estuary 0.7 kg y(-1). In order to examine regional inputs from urban/industrial components, regression analysis was undertaken by comparing three types of hydrochemical signature: suspended sediments (SS), which provide a measure of the particulate component, dissolved organic carbon (DOC) that provides an indication of humic/fulvic acids that are part of the organic colloids and strong chelating agents, and boron a marker of sewage effluents and population density. The results show high positive relationships of T-Hg with both SS and DOC, but no relationship with the urban/industrial signal. The regression analysis with T-Hg indicated on average a gradient of 0.33 ng mg(-1) for DOC and 0.2 ng mg(-1) for SS. They indicate the primary importance of a diffuse source of T-Hg. For the upland areas and cleaner river systems, the linkages between T-Hg and DOC were particularly strong, while for the lowland areas, the linkage with SS proved stronger. Analysis of a latter subset of data that partition the SS into organic and inorganic fractions indicated that the T-Hg was primarily linked with the organic fraction. Indeed, multiple regression of T-Hg with DOC and POM reveals gradients similar to other parts of the World.     

Performance of Greater Sage-Grouse Models for Conservation Assessment in the Interior Columbia Basin, U.S.A.

Abstract: Valid modeling of habitats and populations of Greater Sage-Grouse ( Centrocercus urophasianus) is a critical management need because of increasing concern about population viability. Consequently, we evaluated the performance of two models designed to assess landscape conditions for Greater Sage-Grouse across 13.6 million ha of sagebrush steppe in the interior Columbia Basin and adjacent portions of the Great Basin of the western United States (referred to as the basin). The first model, the environmental index model, predicted conditions at the scale of the subwatershed (mean size of approximately 7800 ha) based on inputs of habitat density, habitat quality, and effects of human disturbance. Predictions ranged on a continuous scale from 0 for lowest environmental index to 2 for optimal environmental index. The second model, the population outcome model, predicted the composite, range-wide conditions for sage grouse based on the contribution of environmental index values from all subwatersheds and measures of range extent and connectivity. Population outcomes were expressed as five classes (A through E) that represented a gradient from continuous, well-distributed populations (outcome A) to sparse, highly isolated populations with a high likelihood of extirpation (outcome E). To evaluate performance, we predicted environmental index values and population outcome classes in areas currently occupied by sage grouse versus areas where extirpation has occurred. Our a priori expectations were that models should predict substantially worse environmental conditions ( lower environmental index) and a substantially higher probability of extirpation ( lower population outcome class) in extirpated areas. Results for both models met these expectations. For example, a population outcome of class E was predicted for extirpated areas, as opposed to class C for occupied areas. These results suggest that our models provided reliable landscape predictions for the conditions tested. This finding is important for conservation planning in the basin, where the models were used to evaluate management of federal lands for sage grouse.     

The Nutrient Status of Some Graminaceous Species in Britain. 1. Molinia Caerulea (L.) Moench

Above-ground biomass biomass of Molinia caerulea from 36 sites throughout Britain was analysed for concentrations of elements (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn and Na), with matching analyses of soil nutrients, together with pH and LOI. Between-year and seasonal variation in the nutrients was also studied at one of the sites. the grass was found on acid sites ranging between pH 3.1 and 5.8. the soil humus content varied widely, and there were significant correlations between that and elements (N, P, K, Ca, Mg and Na) in the soil. Concentrations of calcium, magnesium, zinc and manganese in the plant material were significantly correlated with extractable levels in the soils. Between year variation in the plant nutrient concentrations at one site was of a similar order to variation between the sites. Generally there was less variation in nitrogen, phosphorus and potassium tissue levels than in calcium, magnesium, zinc and copper. Iron and sodium were the most variable. Tissue concentrations of nitrogen, phosphorus, potassium and copper declined throughout the growing season, whereas magnesium, calcium and iron built up until August/September after which a decline set in as the leaves senesced. the results are discussed in relation to the importance of standardizing the time of sampling, in comparison with concentrations of tissue levels in other plants and the growth strategy of this deciduous grass.     

Abundances and variability of tropospheric volatile organic compounds at the South Pole and other Antarctic locations

Multiyear (2000–2006) seasonal measurements of carbon monoxide, hydrocarbons, halogenated species, dimethyl sulfide, carbonyl sulfide and C₁–C₄ alkyl nitrates at the South Pole are presented for the first time. At the South Pole, short-lived species (such as the alkenes) typically were not observed above their limits of detection because of long transit times from source regions. Peak mixing ratios of the longer lived species with anthropogenic sources were measured in late winter (August and September) with decreasing mixing ratios throughout the spring. In comparison, compounds with a strong oceanic source, such as bromoform and methyl iodide, had peak mixing ratios earlier in the winter (June and July) because of decreased oceanic production during the winter months. Dimethyl sulfide (DMS), which is also oceanically emitted but has a short lifetime, was rarely measured above 5 pptv. This is in contrast to high DMS mixing ratios at coastal locations and shows the importance of photochemical removal during transport to the pole. Alkyl nitrate mixing ratios peaked during April and then decreased throughout the winter. The dominant source of the alkyl nitrates in the region is believed to be oceanic emissions rather than photochemical production due to low alkane levels.Sampling of other tropospheric environments via a Twin Otter aircraft included the west coast of the Ross Sea and large stretches of the Antarctic Plateau. In the coastal atmosphere, a vertical gradient was found with the highest mixing ratios of marine emitted compounds at low altitudes. Conversely, for anthropogenically produced species the highest mixing ratios were measured at the highest altitudes, suggesting long-range transport to the continent. Flights flown through the plume of Mount Erebus, an active volcano, revealed that both carbon monoxide and carbonyl sulfide are emitted with an OCS/CO molar ratio of 3.3 × 10^?3 consistent with direct observations by other investigators within the crater rim.     

Elemental and spectroscopic characterization of fractions of an acidic extract of oil sands process water

‘Naphthenic acids’ (NAs) in petroleum produced water and oil sands process water (OSPW), have been implicated in toxicological effects. However, many are not well characterized. A method for fractionation of NAs of an OSPW was used herein and a multi-method characterization of the fractions conducted.     

Metabolism of nC11 fatty acid fed to Trichoderma koningii and Penicillium janthinellum II: Production of intracellular and extracellular lipids

Abstract

Little is known about the fungal metabolism of nC₁₀ and nC₁₁ fatty acids and their conversion into lipids. A mixed batch culture of soil fungi, T. koningii and P. janthinellum, was grown on undecanoic acid (UDA), a mixture of UDA and potato dextrose broth (UDA+PDB), and PDB alone to examine their metabolic conversion during growth. We quantified seven intracellular and extracellular lipid classes using Iatroscan thin-layer chromatography with flame ionization detection (TLC-FID). Gas chromatography with flame ionization detection (GC-FID) was used to quantify 42 individual fatty acids. Per 150 mL culture, the mixed fungal culture grown on UDA+PDB produced the highest amount of intracellular (531 mg) and extracellular (14.7 mg) lipids during the exponential phase. The content of total intracellular lipids represented 25% of the total biomass-carbon, or 10% of the total biomass dry weight produced. Fatty acids made up the largest class of intracellular lipids (457 mg/150 mL culture) and they were synthesized at a rate of 2.4 mg/h during the exponential phase, and decomposed at a rate of 1.8 mg/h during the stationary phase, when UDA+PDB was the carbon source. Palmitic acid (C_16:0), stearic acid (C_18:0), oleic acid (C_18:1), linoleic acid (C_18:2) and vaccenic acid (C_18:1) accounted for >80% of the total intracellular fatty acids. During exponential growth on UDA+PDB, hydrocarbons were the largest pool of all extracellular lipids (6.5 mg), and intracellularly they were synthesized at a rate of 64 μg/h. The mixed fungal species culture of T. koningii and P. janthinellum produced many lipids for potential use as industrial feedstocks or bioproducts in biorefineries.     

Mate choice and the supernormality effect in female sticklebacks (Gasterosteus aculeatus)

Summary Female threespine sticklebacks Gasterosteus aculeatus from a marine population were presented simultaneously with two dummy males that differed in size. When the dummies were moved with a carousel apparatus in a way that roughly simulated a male courtship activity (circling) females responded to the dummies with following behaviour normally directed to courting males. Female sexual response was elicited more effectively by the larger (supernomal) dummy, even though it exceeded by 25% the length of the largest males in the study population. Females did not show complete preference for the larger dummy but allocated courtship effort in proportion to the sizes of the two dummies (Fig. 3). The relative projection areas of the two dummies provided the best predictor of how courtship was allocated between them, suggesting a perceptual basis on which females might select mates. This pattern of partial preference for the supernormal dummy occurred in females that exhibited either high or low amounts of following behaviour and is apparently independent of female responsiveness. Supernormality may therefore provide a mechanism whereby secondary sexual traits can be elaborated, even without evolutionary change in preference for those traits by the opposite sex.     

Aluminium in UK rivers: a need for integrated research related to kinetic factors, colloidal transport, carbon and habitat

Dissolved aluminium concentrations ([Al]) in the <0.45 μm filtered fraction are described for 54 UK river sites covering rural, acidic/acid sensitive, agricultural and urban typologies, and wide pH range (4 to 11). High [Al] occurred under acidic conditions and for acid runoff neutralised by bicarbonate rich groundwater. Thermodynamic analysis indicates Al hydroxide/hydroxy-silicate oversaturation at circumneutral pH across the rivers, but undersaturation at lower/higher pH. The oversaturation reflects in part the presence of Al bearing colloids as indicated by (1) [Al] being correlated with components associated with both lithogenic (Fe, Ti and lanthanides) colloids and organic carbon, (2) baseflow studies using cross-flow ultrafiltration and (3) comparison of our data with Acid Waters Monitoring Network (AWMN) information on labile and non-labile Al. Tree harvesting and emission reductions of SO(x) in acidic and acid sensitive catchments in mid-Wales led to acidification reversal, lower [Al] and changing [H(+)] - [Al] relationships. The [Al] decline was confined to acidic conditions while [Al] increased during the later part of the monitoring period with a peak around 2002 for moorland and forested systems. Colloidal production across the flow range was indicated late in the record by comparison of our data with information collected by the AWMN for a site in mid-Wales. This production seems interlinked with organic carbon and with dissolved CO(2) changes. In order for further understanding of Al hydrogeochemistry in river systems there is a need to integrate research that moves from equilibrium to kinetic and colloidal consideration including the critical issues of organic and inorganic controls within the context of bioavailability and aquatic stress. The colloidal Al may well be of low environmental concern to fish and other factors such as habitat may well be critical.     

Is There a Risk for Introducing Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Through the Legal Importation of Pork?

Since the appearance of porcine reproductive and respiratory syndrome virus (PRRSV) in the late 1980s, the virus has become endemic throughout the world, with only the countries of Sweden, Switzerland, Finland, Norway, Australia, and New Zealand historically free of PRRS virus. Biosecurity is maintained largely through restrictions on the importation of pigs and semen. The risk for a PRRSV outbreak via the legal importation of fresh/chilled/frozen pork from PRRSV-positive countries remains controversial. However, examination of the historical record shows that countries retained a PRRSV-negative status during the importation of more than 500,000 tons of fresh/chilled/frozen pork from PRRSV-positive trading partners. This review describes some of the unique properties of PRRSV, including the poor stability of the virus in the environment, the low probability for airborne transmission, and the inability to sustain infections in feral swine, which make PRRSV a poor candidate for disease introduction through the legal importation of pork.