Examining diel patterns of soil and sap flow from the single-tree to hillslope scale
Abstract
The feedbacks among forest transpiration, soil moisture, and subsurface flowpaths are poorly quantified. We investigate how soil moisture is affected by daily transpiration using geophysical methods on highly instrumented trees and the surrounding soil throughout the growing season at the Boulder Creek Critical Zone Observatory and the H.J. Andrews in Oregon. Multiple lines of evidence, including measurements of sap flow, matric potential, groundwater levels, moisture content, streamflow, and multiple geophysical methods show diel variability that changes seasonally. We find that periods of high sap flow within the diel cycle are coincident with decreases in ground electrical conductivity and soil moisture due to drying of the soil during moisture uptake, and that self-potential measurements are sensitive to tree water use. Seasonal variations in time lags between transpiration and soil moisture, groundwater, electrical conductivity, and stream water help to distinguish between processes controlling evapotranspiration and groundwater fluxes. We use numerical and statistical models to interpret these data.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNS43A..01S
- Keywords:
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- 0416 Biogeophysics;
- BIOGEOSCIENCESDE: 0999 General or miscellaneous;
- EXPLORATION GEOPHYSICSDE: 1824 Geomorphology: general;
- HYDROLOGYDE: 1835 Hydrogeophysics;
- HYDROLOGY