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Toward a Closure of Catchment Mass Balance: Insight on the Missing Link From a Vegetated Lysimeter
Author(s) -
Asadollahi Mitra,
Nehemy Magali F.,
McDonnell Jeffrey J.,
Rinaldo Andrea,
Benettin Paolo
Publication year - 2022
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2021wr030698
Subject(s) - environmental science , hydrology (agriculture) , advection , transpiration , drainage , vegetation (pathology) , water balance , drainage basin , soil water , soil science , geology , ecology , geography , geotechnical engineering , medicine , photosynthesis , physics , botany , cartography , pathology , biology , thermodynamics
Plant transpiration plays a significant role in the terrestrial cycles, but the spatiotemporal origins of water used by plant remains highly uncertain. Therefore, the missing link to fully characterize the water mass balance, for any control volume including significant vegetated surfaces, is identifying and quantifying the key factors that control the age of water used by plants. Here, we bring together an age‐based ( tran ‐SAS) and a physically based (HYDRUS‐1D) model contrasting information gleaned from soil, drainage, and xylem samples at stand scale. In particular, we focus on the relative role of advection, dispersion, and root distribution on the age of water uptake and drainage. We suggest that the interplay of advective and dispersive forces, subsumed by the local Péclet number, drives the age composition of drainage even in the case of extreme uptake rates. The vegetation influence on the age of drainage is mainly exerted by diversifying the subsurface transport pathways resulting in large dispersivity and spatial heterogeneity of soil hydraulic parameters. We introduce a uniform‐equivalent root length for vegetation and show that its ratio to the effective size of the subsurface water storage controls the age selection of water uptakes. Our results are suggestive of a route forward toward a general toolbox to upscale mass balance closures for catchments embedding large and diverse plant assemblages.