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Osborne, Bruce A.
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Osborne, Bruce A.
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Osborne, Bruce A.
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Now showing 1 - 10 of 22
- PublicationAssessing the sensitivity of fertilizer types and soil variables on nitrous oxide emissions in permanent grasslands using the DNDC model(2019-03-12)
; The adoption and use of improved methodologies including models that reflect more robust emissions accounting procedures and the identification of specific mitigation options for agricultural greenhouse gases are a global concern. In Ireland, country-specific N2O emission factors (EFs) are constrained primarily by short-term measurements and limited coverage of regulating factors. Simulation of N2O emissions from grassland silage plots managed for 42 years with different slurry treatments was performed using the DeNitrification-DeComposition (DNDC95) model. The objective was to assess the long-term impact of management practices on N2O fluxes and EFs, and the sensitivity of the outputs to key inorganic and organic fertilizer management and soil variables. The DNDC performed well for urea, cattle slurry and pig slurry applied at variable rates, delivering EFs on-average of 0.35±0.02, 1.80±0.28 and 1.53±0.41%, respectively. Variation in the derived-EFs could be explained by differences in nitrogen inputs (49%), rainfall (16%) and temperature (10%) and are close to national estimates. Sensitivity analysis of the model demonstrated that N2O EFs were higher with ammonium sulphate compared to CAN and urea fertilizers, and with urea-N at higher rates. The replacement of slurry either after the second or third silage cut by urea decreased EFs significantly. There was a strong correlation with the sensitivity of N2O EFs to soil texture, bulk density, pH and organic carbon (R2=0.96-0.99). The resulting-EFs ranged from 0.28 to 0.41% for urea, 1.12 to 2.07% for cattle slurry, and 1.05 to 1.65% for pig slurry, and the corresponding values on-average were 0.35±0.02, 1.74±0.17 and 1.39±0.12%. These findings show that DNDC95, although requiring more improvement, could provide an accurate representation of the effect of soils, climate and management practices on N2O fluxes and subsequent estimates of disaggregated EFs.114 - PublicationSpatially Related Sampling Uncertainty in the Assessment of Labile Soil Carbon and Nitrogen in an Irish Forest PlantationThe importance of labile soil carbon (C) and nitrogen (N) in soil biogeochemical processes is now well recognized. However, the quantification of labile soil C and N in soils and the assessment of their contribution to ecosystem C and N budgets is often constrained by limited information on spatial variability. To address this, we examined spatial variability in dissolved organic carbon (DOC) and dissolved total nitrogen (DTN) in a Sitka spruce forest in central Ireland. The results showed moderate variations in the concentrations of DOC and DTN based on the mean, minimum, and maximum, as well as the coefficients of variation. Residual values of DOC and DTN were shown to have moderate spatial autocorrelations, and the nugget sill ratios were 0.09% and 0.10%, respectively. Distribution maps revealed that both DOC and DTN concentrations in the study area decreased from the southeast. The variability of both DOC and DTN increased as the sampling area expanded and could be well parameterized as a power function of the sampling area. The cokriging technique performed better than the ordinary kriging for predictions of DOC and DTN, which are highly correlated. This study provides a statistically based assessment of spatial variations in DOC and DTN and identifies the sampling effort required for their accurate quantification, leading to improved assessments of forest ecosystem C and N budgets.
32Scopus© Citations 2 - PublicationPost-Invasion Recovery of Plant Communities Colonised by Gunnera tinctoria after Mechanical Removal or Herbicide Application and its Interaction with an Extreme Weather EventThe interventions that are required for both the control and post-invasion restoration of native plant communities depends on several factors, including the efficacy of the measures that are used and how these interact with environmental factors. Here, we report on the results of an experiment on the effects of mechanical removal and herbicide application on the invasive plant Gunnera tinctoria and how an extreme weather event impacted on the invader and on the recovery of native coastal grassland communities. Both removal protocols were largely effective in eradicating mature plants, but the mechanical removal treatment resulted in a major increase in the number of G. tinctoria seedlings, which was exacerbated by the extreme event. Nine months after removal, the number of native species had recovered to c. 80% of that in uninvaded grasslands. In contrast to seedlings, mature plants of G. tinctoria showed a significant reduction in above-ground production after the extreme weather event, although these had largely recovered after six months. Overall, our results indicate that post-control restoration of the plant community may be possible without further significant management interventions. Nevertheless, since some invasive plants survived, further monitoring is required to ensure that recolonisation does not occur.
34Scopus© Citations 1 - PublicationGreenhouse Gas Emissions and Crop Yields From Winter Oilseed Rape Cropping Systems are Unaffected by Management Practices(Frontiers Media, 2021-09-15)
; ; ; Winter oilseed rape is traditionally established via plough-based soil cultivation and conventional sowing methods. Whilst there is potential to adopt lower cost, and less intensive establishment systems, the impact of these on greenhouse gas emissions have not been evaluated. To address this, field experiments were conducted in 2014/2015 and 2015/2016 to investigate the effects of 1) crop establishment method and 2) sowing method on soil greenhouse gas emissions from a winter oilseed rape crop grown in Ireland. Soil carbon dioxide, nitrous oxide and methane emission measurements were carried out using the static chamber method. Yield (t seed ha−1) and the yield-scaled global warming potential (kg CO2-eq. kg−1 seed) were also determined for each management practice. During crop establishment, conventional tillage induced an initially rapid loss of carbon dioxide (2.34 g C m−2 hr−1) compared to strip tillage (0.94 g C m−2 hr−1) or minimum tillage (0.16 g C m−2 hr−1) (p < 0.05), although this decreased to background values within a few hours. In the crop establishment trial, the cumulative greenhouse gas emissions were, apart from methane, unaffected by tillage management when sown at a conventional (125 mm) or wide (600 mm) row spacing. In the sowing method trial, cumulative carbon dioxide emissions were also 21% higher when plants were sown at 10 seeds m−2 compared to 60 seeds m−2 (p < 0.05). Row spacing width (125 and 750 mm) and variety (conventional and semi-dwarf) were found to have little effect on greenhouse gas emissions and differences in seed yield between the sowing treatments were small. Overall, management practices had no consistent effect on soil greenhouse gas emissions and modifications in seed yield per plant countered differences in planting density.51Scopus© Citations 8 - PublicationBiological invaders: Always the bad guys?Invasive species are recognized as one of the major environmental problems worldwide and responsible for a myriad of impacts on ecosystems and ecosystem processes. Although many invasive species exert a range of detrimental effects a more nuanced approach is now emerging, which acknowledges that they can make a positive or beneficial contribution (Schlaepfer et al., 2011; Vimercati et al., 2020, 2022; Mantoani et al., 2022). Clearly, a positive impact may not always be beneficial (Vimercati et al., 2022) and nutrient enrichment due the introduction of an alien nitrogen-fixing plant species, for instance, could result in the loss of important resident species with low nutrient requirements.
51Scopus© Citations 3 - PublicationEvolving Interpolating Models of Net Ecosystem CO2 Exchange Using Grammatical Evolution(Springer, 2012-04-13)
; ; ; ; Accurate measurements of Net Ecosystem Exchange of CO2 between atmosphere and biosphere are required in order to estimate annual carbon budgets. These are typically obtained with Eddy Covariance techniques. Unfortunately, these techniques are often both noisy and incomplete, due to data loss through equipment failure and routine maintenance, and require gap-filling techniques in order to provide accurate annual budgets. In this study, a grammar-based version of Genetic Programming is employed to generate interpolating models for flux data. The evolved models are robust, and their symbolic nature provides further understanding of the environmental variables involved.373Scopus© Citations 7 - PublicationThe Impact of Modifications in Forest Litter Inputs on Soil N2O Fluxes: A Meta-AnalysisAlthough litter can regulate the global climate by influencing soil N2O fluxes, there is no consensus on the major drivers or their relative importance and how these impact at the global scale. In this paper, we conducted a meta-analysis of 21 global studies to quantify the impact of litter removal and litter doubling on soil N2O fluxes from forests. Overall, our results showed that litter removal significantly reduced soil N2O fluxes (−19.0%), while a doubling of the amount of litter significantly increased soil N2O fluxes (30.3%), based on the results of a small number of studies. Litter removal decreased the N2O fluxes from tropical forest and temperate forest. The warmer the climate, the greater the soil acidity, and the larger the soil C:N ratio, the greater the impact on N2O emissions, which was particularly evident in tropical forest ecosystems. The decreases in soil N2O fluxes associated with litter removal were greater in acid soils (pH < 6.5) or soils with a C:N > 15. Litter removal decreased soil N2O fluxes from coniferous forests (−21.8%) and broad-leaved forests (−17.2%) but had no significant effect in mixed forests. Soil N2O fluxes were significantly reduced in experiments where the duration of litter removal was <1 year. These results showed that modifications in ecosystem N2O fluxes due to changes in the ground litter vary with forest type and need to be considered when evaluating current and future greenhouse gas budgets.
24Scopus© Citations 1 - PublicationThe Effect of Cutting and Waterlogging on Plant-Related CO2 and N2O Fluxes Associated with the Invasive N-Fixing Species Gunnera tinctoriaThe overall impact that plant invasions have on greenhouse gas emissions (GHG) by plant-mediated effects and how these interact with environmental and management factors is largely unknown. To address this, we report on the effects of leaf removal and waterlogging, either singularly or in combination, on the fluxes of CO2 and N2O associated with the invasive species Gunnera tinctoria. Both the removal of leaves with and without flooding resulted in higher CO2 emissions due to reductions in photosynthesis. Whilst waterlogging alone was also associated with a reduction in photosynthesis, this was slower than the effect of leaf removal. Significant N2O emissions were associated with intact plants, which increased immediately after leaf removal, or seven days after waterlogging with or without leaf removal. We found positive correlations between CO2 and N2O emissions and petiole and rhizome areas, indicating a size-dependent effect. Our results demonstrate that intact plants of G. tinctoria are a source of N2O emissions, which is enhanced, albeit transiently, by the removal of leaves. Consequently, management interventions on invasive plant populations that involve the removal of above-ground material, or waterlogging, would not only reduce CO2 uptake, but would further compromise the ecosystem GHG balance through enhanced N2O emissions.
34 - PublicationTemperature Impacts the Response of Coffea canephora to Decreasing Soil Water AvailabilityClimate change is expected to result in more frequent periods of both low rainfall and above normal temperatures for many coffee growing regions. To understand how coffee reacts to such change, we studied the physiological and gene expression responses of the clonal variety C. canephora FRT07 exposed to water deficits under two different temperature regimes. Variations in the time-dependent impact of water deficits on leaf stomatal conductance and carbon assimilation were significantly different under the 27 °C and 27 °C/42 °C conditions examined. The physiological responses 24 h after re-watering were also different for both conditions. Expression analysis of genes known to respond to water deficits indicated that drought-related signaling occurred at both temperatures. Deeper insights into the response of coffee to water deficits was obtained by RNASeq based whole transcriptome profiling of leaves from early, late, and recovery stages of the 27 °C experiment. This yielded expression data for 13,642 genes and related differential expression analysis uncovered 362 and 474 genes with increased and decreased expression, respectively, under mild water deficits, and 1627 genes and 2197 genes, respectively, under more severe water deficits. The data presented, from a single clonal coffee variety, serves as an important reference point for future comparative physiological/transcriptomic studies with clonal coffee varieties with different sensitivities to water deficits and high temperatures. Such comparative analyses will help predict how different coffee varieties respond to changing climatic conditions, and may facilitate the identification of alleles associated with high and low tolerance to water deficits, enabling faster breeding of more climate-smart coffee trees.
231Scopus© Citations 11 - PublicationOpen minded and open access: introducing NeoBiota, a new peer-reviewed journal of biological invasions(Pensoft Publishers, 2011-08-11)
; ; ; ; The Editorial presents the focus, scope, policies, and the inaugural issue of NeoBiota, a new open access peer-reviewed journal of biological invasions. The new journal NeoBiota is a continuation of the former NEOBIOTA publication series. The journal will deal with all aspects of invasion biology and impose no restrictions on manuscript size neither on use of color. NeoBiota implies an XML-based editorial workflow and several cutting-edge innovations in publishing and dissemination, such as semantic markup of and enhancements to published texts, data publication, and extensive cross-linking within the journal and to external sources.153
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