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Soil moisture depletion under simulated drought in the Amazon: impacts on deep root uptake
Author(s) -
Markewitz Daniel,
Devine Scott,
Davidson Eric A.,
Brando Paulo,
Nepstad Daniel C.
Publication year - 2010
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2010.03391.x
Subject(s) - throughfall , environmental science , soil water , water content , soil science , moisture , agronomy , hydrology (agriculture) , chemistry , geology , biology , geotechnical engineering , organic chemistry
Summary• Deep root water uptake in tropical Amazonian forests has been a major discovery during the last 15 yr. However, the effects of extended droughts, which may increase with climate change, on deep soil moisture utilization remain uncertain. • The current study utilized a 1999–2005 record of volumetric water content (VWC) under a throughfall exclusion experiment to calibrate a one‐dimensional model of the hydrologic system to estimate VWC, and to quantify the rate of root uptake through 11.5 m of soil. • Simulations with root uptake compensation had a relative root mean square error (RRMSE) of 11% at 0–40 cm and < 5% at 350–1150 cm. The simulated contribution of deep root uptake under the control was c. 20% of water demand from 250 to 550 cm and c. 10% from 550 to 1150 cm. Furthermore, in years 2 (2001) and 3 (2002) of throughfall exclusion, deep root uptake increased as soil moisture was available but then declined to near zero in deep layers in 2003 and 2004. • Deep root uptake was limited despite high VWC (i.e. > 0.30 cm 3 cm −3 ). This limitation may partly be attributable to high residual water contents ( θ r ) in these high‐clay (70–90%) soils or due to high soil‐to‐root resistance. The ability of deep roots and soils to contribute increasing amounts of water with extended drought will be limited.