John Scullion

The effect of earthworms and arbuscular mycorrhizal fungi on growth of and 32P transfer between Allium porrum plants

Tuffen, F., Eason, W. R., Scullion, J. (2002). The effect of earthworms and arbuscular mycorrhizal fungi on growth of and 32P transfer between Allium porrum plants. Soil Biology and Biochemistry, 34, (7), 1027-1036. Arbuscular mycorrhizas; Hyphal interconnections; Interplant transfer; 32P; Earthworms

Completing the FACE of elevated CO2 research

We appraise the present geographical extent and inherent knowledge limits, following two decades of research on elevated CO2 responses in plant communities, and ask whether such research has answered the key question in quantifying the limits of compensatory CO2 uptake in the major biomes. Our synthesis of all ecosystem-scale (between 10 m(2) and 3000 m(2) total experimental plot area) elevated CO2 (eCO2) experiments in natural ecosystems conducted worldwide since 1987 (n=151) demonstrates that the locations of these eCO2 experiments have been spatially biased, targeting primarily the temperate ecosystems of northern America and Europe. We consider the consequences, suggesting fundamentally that this limits the capacity of the research to understand how the worlds major plant communities will respond to eCO2. Most notably, our synthesis shows that this research lacks understanding of impacts on tropical forests and boreal regions, which are potentially the most significant biomes for C sink and storage activity, respectively. Using a meta-analysis of the available data across all biomes, we show equivocal increases in net primary productivity (NPP) from eCO2 studies, suggesting that global validation is needed, especially in the most important biomes for C processing. Further, our meta-analysis identifies that few research programs have addressed eCO2 effects on below-ground C storage, such that at the global scale, no overall responses are discernable. Given the disparity highlighted in the distribution of eCO2 experiments globally, we suggest opportunities for newly-industrialized or developing nations to become involved in further research, particularly as these countries host some of the most important regions for tropical or sub-tropical forest systems. Modeling approaches that thus far have attempted to understand the biological response to eCO2 are constrained with respect to collective predictions, suggesting that further work is needed, which will link models to in situ eCO2 experiments, in order to understand how the worlds most important regions for terrestrial C uptake and storage will respond to a future eCO2 atmosphere.

Use of earthworm casts to validate FT-IR spectroscopy as a 'sentinel' technology for high-throughput monitoring of global changes in microbial ecology

Summary This study aimed to evaluate metabolic fingerprinting by Fourier transform infrared (FT-IR) spectroscopy as a technique for investigating microbial communities and their activities in soil. FT-IR spectra from earthworm casts, and other ‘biosamples’, were compared using multivariate cluster analyses. The work formed part of a wider study to quantify the risk of horizontal gene flow and to assess ecological impacts associated with the release of GM crops or recombinant micro-organisms. A range of samples, including pure cultures of similar soil bacteria, plant materials and earthworm casts of various ages and feeding regimes were analysed. A subset of the cast FT-IR data was compared with DGGE analysis of extracted DNA/RNA. Cluster analysis of FT-IR spectra was capable of differentiating between different bacterial, litter and cast samples. There was congruence between FT-IR and DGGE clustering for food type but not for cast age. Further detailed work on the microbial populations will be needed to investigate relationships between microbial and spectroscopy data.

Food quality and microbial succession in ageing earthworm casts: standard microbial indices and metabolic fingerprinting

Scullion, J., Goodacre, R., Elliott, G., Wei, H., Worgan, H., Gwynn-Jones, D., Griffith, G.W., Darby, R., Bailey, M., Clegg, C., Draper, J. (2003). Food quality and microbial succession in ageing earthworm casts: standard microbial indices and metabolic fingerprinting. Pedobiologia, 47, (5-6), 888-894. 7th International Symposium on Earthworm Ecology, Cardiff, Wales, 2002. Sponsorship: BBSRC/ NERC

Temporal and spatial influences incur reconfiguration of Arctic heathland soil bacterial community structure

Microbial responses to Arctic climate change could radically alter the stability of major stores of soil carbon. However, the sensitivity of plot-scale experiments simulating climate change effects on Arctic heathland soils to potential confounding effects of spatial and temporal changes in soil microbial communities is unknown. Here, the variation in heathland soil bacterial communities at two survey sites in Sweden between spring and summer 2013 and at scales between 0-1 m and, 1-100 m and between sites (> 100 m) were investigated in parallel using 16S rRNA gene T-RFLP and amplicon sequencing. T-RFLP did not reveal spatial structuring of communities at scales < 100 m in any site or season. However, temporal changes were striking. Amplicon sequencing corroborated shifts from r- to K-selected taxon-dominated communities, influencing in silico predictions of functional potential. Network analyses reveal temporal keystone taxa, with a spring betaproteobacterial sub-network centred upon a Burkholderia operational taxonomic unit (OTU) and a reconfiguration to a summer sub-network centred upon an alphaproteobacterial OTU. Although spatial structuring effects may not confound comparison between plot-scale treatments, temporal change is a significant influence. Moreover, the prominence of two temporally exclusive keystone taxa suggests that the stability of Arctic heathland soil bacterial communities could be disproportionally influenced by seasonal perturbations affecting individual taxa.

Treating landfill leachate using passive aeration trickling filters; effects of leachate characteristics and temperature on rates and process dynamics

Biological ammoniacal-nitrogen (NH(4)(+)-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 degrees C. Comparing leachates, rates of NH(4)(+)-N reduction (0.126-0.159 g m(-2) d(-1)) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072-0.194 g m(-2) d(-1)) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012-0.144 g m(-2) d(-1)) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029-0.319 g NH(4)(+)-N m(-2) d(-1) and 0.033-0.251 g C m(-2) d(-1) generally increasing with rising temperatures; rates at 3 degrees C were 9 and 13% of those at 30 degrees C for NH(4)(+)-N and TOC respectively. For the weak leachates (NH(4)(+)-N<140 mg l(-1)) complete oxidation of NH(4)(+)-N was achieved. For the strong leachates (NH(4)(+)-N 883-1150 mg l(-1)) a biphasic treatment response resulted in NH(4)(+)-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH(4)(+)-N to TON in bulk leachate. The temporal decoupling of NH(4)(+)-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH(4)(+)-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH(4)(+)-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors.

A new emphasis on root traits for perennial grass and legume varieties with environmental and ecological benefits

Abstract Grasslands cover a significant proportion of the agricultural land within the UK and across the EU, providing a relatively cheap source of feed for ruminants and supporting the production of meat, wool and milk from grazing animals. Delivering efficient animal production from grassland systems has traditionally been the primary focus of grassland‐based research. But there is increasing recognition of the ecological and environmental benefits of these grassland systems and the importance of the interaction between their component plants and a host of other biological organisms in the soil and in adjoining habitats. Many of the ecological and environmental benefits provided by grasslands emanate from the interactions between the roots of plant species and the soil in which they grow. We review current knowledge on the role of grassland ecosystems in delivering ecological and environmental benefits. We will consider how improved grassland can deliver these benefits, and the potential opportunities for plant breeding to improve specific traits that will enhance these benefits whilst maintaining forage production for livestock consumption. Opportunities for exploiting new plant breeding approaches, including high throughput phenotyping, and for introducing traits from closely related species are discussed.

Above‐ and below‐ground responses of Calamagrostis purpurea to UV‐B radiation and elevated CO2 under phosphorus limitation

UV-B radiation and elevated CO₂ may impact rhizosphere processes through altered below-ground plant resource allocation and root exudation, changes that may have implications for nutrient acquisition. As nutrients limit plant growth in many habitats, their supply may dictate plant response under elevated CO₂. This study investigated UV-B exposure and elevated CO₂ effects, including interactions, on plant growth, tissue chemistry and rooting responses relating to P acquisition. The sub-arctic grass Calamagrostis purpurea was subjected to UV-B (0 or 3.04 kJ m⁻² day⁻¹) and CO₂ (ambient 380 or 650 ppmv) treatments in a factorial glasshouse experiment, with sparingly soluble P (0 or 0.152 mg P per plant as FePO₄) a further factor. It was hypothesized that UV-B exposure and elevated CO₂would change plant resource allocation, with CO₂ mitigating adverse responses to UV-B exposure and aiding P uptake. Plant biomass and morphology, tissue composition and rhizosphere leachate properties were measured. UV-B directly affected chemical composition of shoots and interacted with CO₂ to give a greater root biomass. Elevated CO₂ altered the composition of both shoots and roots and increased shoot biomass and secondary root length, while leachate pH decreased. Below-ground responses to CO₂ did not affect P acquisition although P limitation progressively reduced leachate pH and increased secondary root length. Although direct plant growth, foliar composition and below-ground nutrient acquisition responses were dominated by CO₂ treatments, UV-B modified these CO₂ responses significantly. These interactions have implications for plant responses to future atmospheric conditions.

UV-B radiation induced changes in litter quality affects earthworm growth and cast characteristics as determined by metabolic fingerprinting

Gwynn-Jones, D., Huang, W., Easton, G., Goodacre, R., Scullion, J. (2003). UV-B radiation induced changes in litter quality affects earthworm growth and cast characteristics as determined by metabolic fingerprinting. Pedobiologia, 47, (5-6), 784-787.

Plant community composition and an insect outbreak influence phenol oxidase activity and soil–litter biochemistry in a sub-Arctic birch heath

AbstractRates of decomposition in Arctic soils are regulated by temperature and moisture, but substrate availability is dictated by vegetation inputs, which are also subject to biotic influences. Here, we examine how leaf and litter inputs from individual dwarf shrub species influence soil enzyme activity in a sub-Arctic heath community in Abisko, Sweden. We further consider how foliar damage via insect herbivory (and outbreak) affects the soil community and decomposition. During the peak growing season (July 2011), we assessed how shrub community composition (Empetrum hermaphroditum, Vaccinium myrtillus, V. uliginosum and V. vitis-idaea) determined litter and soil phenol oxidase activity. A periodic severe outbreak of autumn moth larvae (Epirrita autumnata) affected this community in the following year (July 2012), and we used this to investigate its impact on relationships with phenol oxidase activity, soil respiration, soluble NH4+ and soluble phenolics; the soluble factors being directly associated with inputs from insect larval waste (frass). Pre-outbreak (2011), the strongest relationship observed was higher phenol oxidase activity with E. hermaphroditum cover. In the outbreak year (2012), phenol oxidase activity had the strongest relationship with damage to the deciduous species V. myrtillus, with greater herbivory lowering activity. For the other deciduous species, V. uliginosum, soil NH4+ and phenolics were negatively correlated with foliar larval damage. Phenol oxidase activity was not affected by herbivory of the evergreen species, but there was a strong positive relationship observed between E. hermaphroditum community abundance and soil respiration. We highlight the dominant role of E. hermaphroditum in such sub-Arctic shrub communities and show that even during insect outbreaks, it can dictate soil processes.