Soil moisture plays a key role in hydrological, biogeochemical and energy budgets of terrestrial ecosystems. Accurate soil moisture measurements in the Amazon are difficult due to logistical constraints. Realistic soil moisture data in the Amazon are greatly needed for improving our understanding of ecohydrological processes within tropical forests and for improving models of these systems in the face of changing environmental conditions.
1. First Time Domain Reflectometers (TDR) soil moisture calibration in an old-growth forest in the Central Amazon.
2. Interannual thirty-minute observations of soil moisture up to 14.2-m depth.
3. The Topp model underestimated volumetric water content by 22 to 42%.
4. Dry season morning-night fluctuation of soil moisture were observed
Depth-specific Time Domain Reflectometers (TDR) were calibrated using local soils in a controlled laboratory producing a novel calibration. The sensors were later installed to their specific calibration depth in a 14.2 m pit. The widely used Topp model underestimated the site-specific volumetric water content (θv) by 22-42% indicating significant error in the model when applied to these well-structured, clay rich tropical forest soils. The calibrated wet- and dry-season θv data showed a variety of depth and temporal variations highlighting the importance of soil textural differentiation, root uptake depths, as well as event- to seasonal-precipitation effects.
Contacts (BER PM): Daniel Stover, SC-23.1, Daniel.Stover@science.doe.gov (301-903-0289)
PI Contact: Robinson Negron-Juarez, LBNL, Robinson.firstname.lastname@example.org
This research was supported as part of the Next Generation Ecosystem Experiments-Tropics, funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, under contract number DE-AC02-05CH11231. Laura Borma would like to acknowledge Go-Amazon (2013/50531-2) for retrofitting the pit structure.
Negrón-Juárez, S. Ferreira, M. Mota, B Faybishenko, M. Monteiro, L. Candido, R. Ribeiro, R. de Oliveira, A. de Araujo, J. Warren, B. Newman, B. Gimenez, C. Varadharajan, D Agarwal, L. Borma, J. Tomasella, N. Higuchi, J. Chambers. Calibration, Measurement and Characterization of Soil Moisture Dynamics in a Central Amazonian Tropical Forest. Vadose Zone Journal, 2020. DOI:10.1002/vzj2.20070
Data available at http://dx.doi.org/10.15486/ngt/1602141