Catchment-scale land-use change is recognised as a major threat to aquatic biodiversity and ecosystem functioning globally. In the UK uplands rotational vegetation burning is practised widely to boost production of recreational game birds, and while some recent studies have suggested burning can alter river water quality there has been minimal attention paid to effects on aquatic biota. We studied ten rivers across the north of England between March 2010 and October 2011, five of which drained burned catchments and five from unburned catchments. There were significant effects of burning, season and their interaction on river macroinvertebrate communities, with rivers draining burned catchments having significantly lower taxonomic richness and Simpsons diversity. ANOSIM revealed a significant effect of burning on macroinvertebrate community composition, with typically reduced Ephemeroptera abundance and diversity and greater abundance of Chironomidae and Nemouridae. Grazer and collector-gatherer feeding groups were also significantly less abundant in rivers draining burned catchments. These biotic changes were associated with lower pH and higher Si, Mn, Fe and Al in burned systems. Vegetation burning on peatland therefore has effects beyond the terrestrial part of the system where the management intervention is being practiced. Similar responses of river macroinvertebrate communities have been observed in peatlands disturbed by forestry activity across northern Europe. Finally we found river ecosystem changes similar to those observed in studies of wild and prescribed forest fires across North America and South Africa, illustrating some potentially generic effects of fire on aquatic ecosystems.
Atmospheric CO2 concentrations have risen 40% since the start of the industrial revolution. Beginning in 1996, the Duke Free-Air CO2 Enrichment experiment has exposed plots in a loblolly pine forest to an additional 200 microL/L CO2 compared to trees growing in ambient CO2. This paper presents new belowground data and a synthesis of results through 2008, including root biomass and nutrient concentrations, soil respiration rates, soil pore-space CO2 concentrations, and soil-solution chemistry to 2 m depth. On average in elevated CO2, fine-root biomass in the top 15 cm of soil increased by 24%, or 59 g/m2 (26 g/m2 C). Coarse-root biomass sampled in 2008 was twice as great in elevated CO2 and suggests a storage of approximately 20 g C x m(-2) x yr(-1). Root C and N concentrations were unchanged, suggesting greater belowground plant demand for N in high CO2. Soil respiration was significantly higher by 23% on average as assessed by instantaneous infrared gas analysis and 24-h integrated estimates. N fertilization decreased soil respiration and fine-root biomass by approximately 10-20% in both ambient and elevated CO2. In recent years, increases in root biomass and soil respiration grew stronger, averaging approximately 30% at high CO2. Peak changes for root biomass, soil respiration, and other variables typically occurred in midsummer and diminished in winter. Soil CO2 concentrations between 15 and 100 cm depths increased 36-60% in elevated CO2. Differences from 30 cm depth and below were still increasing after 10 years exposure to elevated CO2, with soil CO2 concentrations >10000 microL/L higher at 70- and 100-cm depths, potentially influencing soil acidity and rates of weathering. Soil solution Ca2+ and total base cation concentrations were 140% and 176% greater, respectively, in elevated CO2 at 200 cm depth. Similar increases were observed for soil-solution conductivity and alkalinity at 200 cm in elevated CO2. Overall, the effect of elevated CO2 belowground shows no sign of diminishing after more than a decade of CO2 enrichment.
Wagner syndrome (WS) is an autosomal dominant vitreoretinopathy affecting various ocular features and is caused by mutations in the canonical splice sites of the VCAN gene, which encodes the large chondroitin sulfate proteoglycan, versican. We report the identification of novel splice acceptor and donor-site mutations (c.4004-1G>C and c.9265+2T>A) in two large WS families from France and the United Kingdom. To characterize their pathogenic mechanisms we performed qRT-PCR experiments on RNA from patient-derived tissues (venous blood and skin fibroblasts). We also analyzed RNA from the original Swiss family reported by Wagner (who has the previously reported c.9265+1G>A mutation). All three mutations resulted in a quantitative increase of transcript variants lacking exons 7 and/or 8. However, the magnitude of the increase varied between tissues and mutations. We discuss altered balance of VCAN splice variants in combination with reduction in glycosaminoglycan protein modifications as possible pathogenic mechanisms.
Acidification can result in the mobilisation and release of toxic inorganic monomeric aluminium (Al) species from soils into aquatic ecosystems. Although it is well-established that conifer trees enhance acidic atmospheric deposition and exacerbate soil and water acidification, the effect of broad-leaved woodland on soil and water acidification is less clear. This study investigated the effect of broadleaf woodland cover on the acid-base chemistry and Al species present in stream water, and processes controlling these in the acid-sensitive area around Loch Katrine, in the central Highlands, Scotland, UK, where broadleaf woodland expansion is occurring. A nested sampling approach was used to identify 22 stream sampling locations, in sub-catchments of 3.2-61 ha area and 0-45% broadleaf woodland cover. In addition, soils sampled from 68 locations were analysed to assess the influence of: (i) broadleaf woodland cover on soil characteristics and (ii) soil characteristics on stream water chemistry. Stream water pH was negatively correlated with sub-catchment % woodland cover, indicating that woodland cover is enhancing stream water acidification. Concentrations of all stream water Al species (monomeric total, organic and inorganic) were positively correlated with % woodland cover, although not significantly, but were below levels that are toxic to fish. Soil depth, O horizon depth and soil chemistry, particularly of the A horizon, appeared to be the dominant controls on stream water chemistry rather than woodland cover. There were significant differences in soil acid-base chemistry, with significantly lower O horizon pH and A horizon base saturation and higher A horizon exchangeable Al in the wooded catchments compared to the control. This is evidence that the mobile anion effect is already occurring in the study catchments and suggests that stream water acidification arising from broadleaf woodland expansion could occur, especially where tree density is high and acid deposition is predominantly in dry or occult forms.
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