Mendy Smith, Colorado State University
Osvaldo Sala, Arizona State University (Drought-Net)
Kim Novick, Indiana University (MMSF)
Many climate models predict increases in the frequency of droughts but the consequences of drought on ecosystem carbon dynamics are difficult to predict. Rising temperatures may increase carbon uptake by lengthening the growing season, yet droughts may decrease carbon uptake owing to photosynthetic declines. Further, soil microbes, which control CO2 and CH4 fluxes, are temperature- and moisture-sensitive. We’re investigating the carbon consequences of drought in ecosystems that have not historically experienced severe water shortages (e.g., hardwood forests).
Many regional and global climate models predict increases in the frequency of droughts resulting from reduced rainfall and high temperatures. To the extent that droughts reduce carbon uptake and storage by forests, droughts may amplify the effects of climate warming. The goals of Drought-Net are to establish an international network of scientists with a common interest in quantifying the impacts of drought on ecosystems. Our goal is to build this network in order to advance our general understanding of how terrestrial ecosystems may vary in their response to drought, and more specifically to assess the mechanistic basis for differential sensitivities of terrestrial ecosystems to drought.
Temperate forests are the largest terrestrial sinks of atmospheric CO2 globally but the extent to which these forests will sequester carbon in the wake of climate change remain poorly known. While rising temperatures could increase C uptake by plants by lengthening the growing season, a greater frequency and intensity of droughts could decrease C uptake by plants owing to photosynthetic declines. Further, microbes – which control greenhouse gas fluxes from soils – are both temperature- and moisture-sensitive. We are currently quantifying the carbon consequences of drought by measuring the response of tree growth (using long-term biometric plots and root in-growth cores) and forest carbon balance (measured by eddy co-variance and remote sensing) to changes in soil water availability. A primary focus of this research is to investigate differences in tree species’ sensitivities to water stress at the leaf-level (using a boom lift) and stem-level (using sap flux probes and dendrometer bands).