About the Project
Tree death in extreme droughts and heatwaves has been widely reported across all major forest biomes over the last few years (e.g.Hartmann et al., 2018; Lewis et al., 2011; Peng et al., 2011; Stovall et al., 2019), and the frequency and severity of such events is expected to increase in many regions. Yet our ability to predict how our forests will respond to extreme heat and drought is very limited. Major unknowns are how much water do trees hold inside themselves, under what conditions do they draw on these internal stores, and how will this be impacted by future environmental change? Whilst these are apparently simple questions, the water held by trees remains largely ‘hidden’ both for individual trees, and across entire forests. Yet we know water content is closely linked to drought resilience (e.g. Rao et al., 2019) and the hydraulic strategies of trees (Konings and Gentine, 2017). In addition, forests of the future may use water differently, depending on their climate and levels of carbon dioxide to which they are exposed. Therefore, a better understanding of how much water trees hold and when they draw on it will help improve everything from local forest and water management, to models of global vegetation dynamics and climate interactions.
This project will look deeper into this hidden dimension of trees and the water they hold, and how this will change in the future, using multiple methods and techniques (e.g. sonic tomography, eddy flux, direct moisture sensing, modelling). In addition, it will provide a fantastic opportunity for the student to work at a globally unique experimental facility that is artificially enhancing the CO2 concentrations of an old growth oak forest in central UK (BIFoR FACE), and is producing ‘trees of the future’.
References
Ciruzzi, D. M., & Loheide, S. P. ( 2019). Monitoring tree sway as an indicator of water stress. Geophysical Research Letters, 46. https://doi.org/10.1029/2019GL084122
Hartmann, H., Moura, C., Anderegg, W., Ruehr, N., Salmon, Y., Allen, C., Arndt, S., Breshears, D., Davi, H., Galbraith, D., Ruthrof, K., Wunder, J., Adams, H., Bloemen, J., Cailleret, M., Cobb, R., Gessler, A., Grams, T., Jansen, S., Kautz, M., Lloret, F., O’Brien, M., 2018. Research frontiers for improving our understanding of drought-induced tree and forest mortality. New Phytol. 218, 15–28. https://doi.org/10.1111/nph.15048
Konings, A.G., Gentine, P., 2017. Global variations in ecosystem-scale isohydricity. Glob. Chang. Biol. 23, 891–905. https://doi.org/10.1111/gcb.13389
Lewis, S., Brando, P., Phillips, O.L., van der Heijden, G.M.F., Nepstad, D.C., 2011. The 2010 amazon drought. Science (80-. ). 331, 554.
Peng, C., Ma, Z., Lei, X., Zhu, Q., Chen, H., Wang, W., Liu, S., Li, W., Fang, X., Zhou, X., 2011. A drought-induced pervasive increase in tree mortality across Canada ’ s boreal forests. Nat. Clim. Chang. 1, 467–471. https://doi.org/10.1038/nclimate1293
Rao, K., Anderegg, W.R.L., Sala, A., Martínez-vilalta, J., Konings, A.G., 2019. Remote Sensing of Environment Satellite-based vegetation optical depth as an indicator of drought-driven tree mortality ☆. Remote Sens. Environ. 227, 125–136. https://doi.org/10.1016/j.rse.2019.03.026
Stovall, A.E.L., Shugart, H., Yang, X., 2019. Tree height explains mortality risk during an intense drought. Nat. Commun. 10, 4385. https://doi.org/10.1038/s41467-019-12380-6
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