Ishtiaq, K. S., & Abdul-Aziz, O. I. (2015). Relative Linkages of Canopy-Level CO2 Fluxes with the Climatic and Environmental Variables for US Deciduous Forests. Environmental Management, 55(4), 943–960.
Abstract: We used a simple, systematic data-analytics approach to determine the relative linkages of different climate and environmental variables with the canopy-level, half-hourly CO2 fluxes of US deciduous forests. Multivariate pattern recognition techniques of principal component and factor analyses were utilized to classify and group climatic, environmental, and ecological variables based on their similarity as drivers, examining their interrelation patterns at different sites. Explanatory partial least squares regression models were developed to estimate the relative linkages of CO2 fluxes with the climatic and environmental variables. Three biophysical process components adequately described the system-data variances. The ‘radiation-energy’ component had the strongest linkage with CO2 fluxes, whereas the ‘aerodynamic’ and ‘temperature-hydrology’ components were low to moderately linked with the carbon fluxes. On average, the ‘radiation-energy’ component showed 5 and 8 times stronger carbon flux linkages than that of the ‘temperature-hydrology’ and ‘aerodynamic’ components, respectively. The similarity of observed patterns among different study sites (representing gradients in climate, canopy heights and soil-formations) indicates that the findings are potentially transferable to other deciduous forests. The similarities also highlight the scope of developing parsimonious data-driven models to predict the potential sequestration of ecosystem carbon under a changing climate and environment. The presented data-analytics provides an objective, empirical foundation to obtain crucial mechanistic insights; complementing process-based model building with a warranted complexity. Model efficiency and accuracy (R 2 = 0.55–0.81; ratio of root-mean-square error to the observed standard deviations, RSR = 0.44–0.67) reiterate the usefulness of multivariate analytics models for gap-filling of instantaneous flux data.
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Malone, S. L., Barr, J., Fuentes, J. D., Oberbauer, S. F., Staudhammer, C. L., Gaiser, E. E., et al. (2016). Sensitivity to Low-Temperature Events: Implications for CO2 Dynamics in Subtropical Coastal Ecosystems. Wetlands, 36(5), 957–967.
Abstract: We analyzed the ecosystem effects of low-temperature events (< 5 A degrees C) over 4 years (2009-2012) in subtropical short and long hydroperiod freshwater marsh and mangrove forests within Everglades National Park. To evaluate changes in ecosystem productivity, we measured temporal patterns of CO2 and the normalized difference vegetation index over the study period. Both water levels and distance from the coast influenced the ecosystem response to low-temperature events. Photosynthetic capacity, or the maximum CO2 uptake rate, and sensitivity to low-temperature events were much higher in mangrove forest than in freshwater marsh ecosystems. During low-temperature events photosynthetic capacity was enhanced in freshwater marsh while it declined in mangrove forests, and respiration rates declined across Everglades ecosystems. While the long hydroperiod freshwater marsh gained 0.26 g CO2 m(-2) during low-temperature events, the mangrove forest had the greatest C lost (7.11 g CO2 m(-2) low-temperature event(-1)) followed by the short hydroperiod freshwater marsh (0.37 g CO2 m(-2) low-temperature event(-1)). Results suggest that shifts in the frequency and intensity of weather anomalies with climate change can alter C assimilation rates in Everglades ecosystems through effects on the photosynthetic capacity of existing species, which might lead to changes in species composition and ecosystem productivity in the future.
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Wanninkhof, R., & Trinanes, J. (2017). The impact of changing wind speeds on gas transfer and its effect on global air-sea CO2 fluxes. Global Biogeochem. Cycles, 31(6), 961–974.
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