Speculations on the application of foliar <sup>13</sup>C discrimination to reveal groundwater dependency of vegetation, provide estimates of root depth and rates of groundwater use

Abstract

Abstract. 15Groundwater-dependent vegetation is globally distributed, having important ecological, social and economic value. Along with the groundwater resources upon which it depends, this vegetation is under increasing threat through excessive rates of groundwater extraction.In this study we examined one shallow-rooted and two deep-rooted tree species at multiple sites along a naturally occurring 20 gradient in depth-to-groundwater. We measured (i) stable isotope ratios of leaves (δ 13 C), xylem and groundwater (δ 2 H and δ 18 O); and (ii) leaf vein density. We established that foliar discrimination of 13 C (∆ 13 C) is a reliable indicator of groundwater use by vegetation and can also be used to estimate rooting depth. Through comparison with a continental-scale assessment of foliar ∆ 13 C, we also estimated the upper limits to annual rates of groundwater use. We conclude that maximum rooting depth for both deep-rooted species ranged between 9.4 m and 11.2 m and that annual rates of groundwater use ranged ca 25 1400 -1700 mm for Eucalyptus camaldulensis and 600 -900 mm for Corymbia opaca. Several predictions about hydraulic and leaf traits arising from the conclusion that these two species made extensive use of groundwater were supported by additional studies of these species in central Australia.

Evaluation of Morpho-Physiological Traits Adjustment of Prosopis tamarugo Under Long-Term Groundwater Depletion in the Hyper-Arid Atacama Desert

“…Intrinsic water use efficiency, defined as the relationship between net photosynthesis and stomatal conductance (A n ; iWUE), integrated over time, and δ 13 C are positively associated (Farquhar et al, 1982 ). δ 13 C has been used in the study of iWUE of eucalyptus forests subjected to water table depth gradients (Zolfaghar et al, 2017 ), and in estimating root depth and groundwater use in different forest communities (Rumman et al, 2017 ).…”