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Geophysical subsurface imaging for ecological applications

Jayawickreme, DH, EG Jobbágy, RB Jackson
New Phytologist
Journal Volume/Pages: 
Ecologists, ecohydrologists, and biogeochemists need detailed insights into belowground properties and processes, including changes in soil water, salts, and other elements that can influence ecosystem productivity and functioning. Relying on traditional physical sampling and observation techniques for such insights can be costly, time consuming, and infeasible, especially if the spatial scales involved are large. Geophysical imaging provides an alternative or complement to traditional sampling approaches to gather subsurface variables across time and space. In this paper, we review aspects of geophysical imaging, particularly electrical and electromagnetic imaging that may benefit ecologists seeking clearer understanding of subsurface properties and dynamics. Using electrical resistivity imaging, for example, we have been able to quantify the effect of land-use conversions to agriculture on salt mobilization and leaching across kilometer-long transects and to depths of tens of meters, spatial scales that have been difficult to tackle with customary approaches. Advances in ground penetrating radar and other geophysical imaging methods in the recent years have also created opportunities for subsurface imaging with sufficient detail to map small (≥5cm diameter) animal burrows and plant roots, observe soil-water and vegetation spatial correlations in small watersheds, as well as shallow water estuaries and marshes, and quantify changes in groundwater storage at local to regional scales using geophysical data from ground and space based platforms. Ecologists should benefit from adopting these minimally invasive, scalable imaging technologies to explore the subsurface and advance our collective research.
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