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  • 1
    In: Global Change Biology, June 2017, Vol.23(6), pp.2154-2165
    Description: Eddy covariance () continues to provide invaluable insights into the dynamics of Earth's surface processes. However, despite its many strengths, spatial replication of at the ecosystem scale is rare. High equipment costs are likely to be partially responsible. This contributes to the low sampling, and even lower replication, of ecoregions in Africa, Oceania (excluding Australia) and South America. The level of replication matters as it directly affects statistical power. While the ergodicity of turbulence and temporal replication allow an tower to provide statistically robust flux estimates for its footprint, these principles do not extend to larger ecosystem scales. Despite the challenge of spatially replicating , it is clearly of interest to be able to use to provide statistically robust flux estimates for larger areas. We ask: How much spatial replication of is required for statistical confidence in our flux estimates of an ecosystem? We provide the reader with tools to estimate the number of towers needed to achieve a given statistical power. We show that for a typical ecosystem, around four towers are needed to have 95% statistical confidence that the annual flux of an ecosystem is nonzero. Furthermore, if the true flux is small relative to instrument noise and spatial variability, the number of towers needed can rise dramatically. We discuss approaches for improving statistical power and describe one solution: an inexpensive system that could help by making spatial replication more affordable. However, we note that diverting limited resources from other key measurements in order to allow spatial replication may not be optimal, and a balance needs to be struck. While individual towers are well suited to providing fluxes from the flux footprint, we emphasize that spatial replication is essential for statistically robust fluxes if a wider ecosystem is being studied.
    Keywords: Carbon ; Carbon Dioxide ; Co 2 ; Eddy Covariance ; Effect Size ; Flux ; Latent ; Replication ; Sensible ; Significant
    ISSN: 1354-1013
    E-ISSN: 1365-2486
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  • 2
    Language: English
    In: PLoS ONE, 02 November 2010, Vol.5(11), pp.1-12
    Description: It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (‘‘ecosystem engineers'') through the secretion of naturally adhesive organic material (EPS: extracellular polymeric...
    Keywords: Life Sciences ; Ecology, Environment ; Life Sciences ; Microbiology and Parasitology ; Sciences (General)
    ISSN: 1932-6203
    E-ISSN: 1932-6203
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  • 3
    Description: The Eden Estuary is a small, coastal inlet situated in Fife between the Tay and Forth Estuaries on the east coast of Scotland. A multidisciplinary case study of the estuary was conducted over a three year period observing the dynamic responses of biotic and abiotic behaviour to long term patterns of climate variability. Historical Trend Analysis (HTA) was combined with autocorrelation and spectral density analysis to identify trends, patterns and periodicity in natural cycles. River flow and wind direction data were cross-correlated with the North Atlantic Oscillation Index (NAOI) to link local responses to patterns of northern hemisphere circulation, and with Wolfe Sunspot Numbers representing variable solar activity as a potential driving mechanism for climate driven change. Assessment of the current state of ‘estuary health' used a proxy analysis of ecosystem function, combining Bray-Curtis similarity nMDS of macrofaunal community diversity with species functional traits. The observed estuary responses were subsequently projected onto the forecasted climate change scenarios reported by the IPCCAR4, UKCIP09 and to modelled projections of solar activity to propose future trajectories of change for the estuary. Autocorrelation analysis of river flow and wind direction data identified significant (95%) correlations corresponding to solar, lunar, planetary and volcanic events. Spectral density analysis similarly identified significant (〉95%) frequencies corresponding to known periods of solar activity, lunar cycles and Bruckner climatic cycles. Formal cross -correlation revealed significant (95%) relationships between both river flow and wind data with the NAOI, and using a longer times series, between river Thames annual flow and Wolfe sunspot numbers; correlating solar maximums with high flow. Periods consistent to Schwabe and Hale solar cycles were evident in the wind and river data however the NAOI only displayed Hale periodicity, inferring the river and wind data are not solely influenced (or potentially driven) by the NAO. No detrimental impact of estuary change was observed in the biotic responses inferring maintenance of estuary health. This study identifies potential driving mechanisms of estuary perturbation and whilst causal mechanisms can only be proposed, these observations form a baseline for future targeted modelling, monitoring and management.
    Keywords: 577.786
    Source: Networked Digital Library of Theses and Dissertations
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  • 4
    Language: English
    Description: The Eden Estuary is a small, coastal inlet situated in Fife between the Tay and Forth Estuaries on the east coast of Scotland. A multidisciplinary case study of the estuary was conducted over a three year period observing the dynamic responses of biotic and abiotic behaviour to long term patterns of climate variability. Historical Trend Analysis (HTA) was combined with autocorrelation and spectral density analysis to identify trends, patterns and periodicity in natural cycles. River flow and wind direction data were cross-correlated with the North Atlantic Oscillation Index (NAOI) to link local responses to patterns of northern hemisphere circulation, and with Wolfe Sunspot Numbers representing variable solar activity as a potential driving mechanism for climate driven change. Assessment of the current state of ‘estuary health' used a proxy analysis of ecosystem function, combining Bray-Curtis similarity nMDS of macrofaunal community diversity with species functional traits. The observed estuary responses were subsequently projected onto the forecasted climate change scenarios reported by the IPCCAR4, UKCIP09 and to modelled projections of solar activity to propose future trajectories of change for the estuary. Autocorrelation analysis of river flow and wind direction data identified significant (95%) correlations corresponding to solar, lunar, planetary and volcanic events. Spectral density analysis similarly identified significant (〉95%) frequencies corresponding to known periods of solar activity, lunar cycles and Bruckner climatic cycles. Formal cross -correlation revealed significant (95%) relationships between both river flow and wind data with the NAOI, and using a longer times series, between river Thames annual flow and Wolfe sunspot numbers; correlating solar maximums with high flow. Periods consistent to Schwabe and Hale solar cycles were evident in the wind and river data however the NAOI only displayed Hale periodicity, inferring the river and wind data are not solely influenced (or potentially driven) by the NAO. No detrimental impact of estuary change was observed in the biotic responses inferring maintenance of estuary health. This study identifies potential driving mechanisms of estuary perturbation and whilst causal mechanisms can only be proposed, these observations form a baseline for future targeted modelling, monitoring and management.
    Keywords: 577.786
    Source: The British Library
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