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

Abstract

Water extraction from the underground aquifers of the Pampa del Tamarugal (Atacama Desert, Chile) reduced the growing area of Prosopis tamarugo, a strict phreatic species endemic to northern Chile. The objective of this work was to evaluate the effect of various architectural and morpho-physiological traits adjustment of P. tamarugo subjected to three groundwater depletion intervals (GWDr): <1 m (control), 1–4 m and 6–9 m. The traits were evaluated at three levels, plant [height, trunk cross-section area, leaf fraction (fGCC), and crown size], organ [length of internodes, leaf mass per unit area (LMA), leaflet mass and area], and tissue level [wood density (WD), leaf 13C, 18O isotope composition (δ), and intrinsic water use efficiency (iWUE)]. In addition, soil water content (VWC) to 1.3 m soil depth, pre-dawn and midday water potential difference (ΔΨ), and stomatal conductance (gs) were evaluated. At the deeper GWDr, P. tamarugo experienced significant growth restriction and reduced fGCC, the remaining canopy had a significantly higher LMA associated with smaller leaflets. No differences in internode length and WD were observed. Values for δ13C and δ18O indicated that as GWDr increased, iWUE increased as a result of partial stomata closure with no significant effect on net assimilation over time. The morpho-physiological changes experienced by P. tamarugo allowed it to acclimate and survive in a condition of groundwater depletion, keeping a functional but diminished canopy. These adjustments allowed maintenance of a relatively high gs; ΔΨ was not different among GWDrs despite smaller VWC at greater GWDr. Although current conservation initiatives of this species are promising, forest deterioration is expected continue as groundwater depth increases.

Squandering water in drylands: the water‐use strategy of the phreatophyte Ziziphus lotus in a groundwater‐dependent ecosystem

“…A similar DTGW threshold for groundwater use was also reported for the deep‐rooted phreatophyte Corymbia opaca in arid regions of Australia (Rumman et al, 2018). The consistency of our results with those of previous studies supports the use of leaf Δ 13 C as potentially indicative of rooting depth and groundwater access in Z. lotus and other species of GDEs in arid regions (Zolfaghar et al, 2014; Garrido et al, 2018; Rumman et al, 2018). Furthermore, these findings allow for establishing a threshold use of groundwater that could reflect the maximum rooting depth of the species for optimal functioning in dryland GDEs.…”

“…An example of such vulnerable species are phreatophytes that support groundwater‐dependent ecosystems (GDEs) (Kløve et al, 2014; Eamus et al, 2015, 2016) and whose decoupled productivity from climate conditions represents a critical ecosystem function for drylands. Exploring the physiological response of such phreatophytes along groundwater depth gradients is key to understanding their response to reductions in water availability (Garrido et al, 2018), both as consequence of climate change and the increase in human demand for groundwater.…”

Improved physiological performance in grapevine (Vitis viniferaL.) cv. Cabernet Sauvignon facing recurrent drought stress

“…Subsequently, a subsample of each replicate and treatment was weighed on an Precisa 125A analytical balance (Precisa Gravimetrics, Dietikon, Switzerland) and placed in tin capsules (0.002-0.003 g). The isotope composition of each sample was determined through a standard procedure with an isotope ratio mass spectrometer model INTEGRA2 (Sercon, Crewe, England) with an accuracy of 0.3‰ (as described by Garrido et al 2018). Carbon isotope values were referenced to its internationally accepted reference standard, Vienna Pee Dee Belemnite (Dawson et al 2002).…”

Los microsatélites revelan una alta diferenciación genética entre las poblaciones nativas de Geoffroea decorticans en el desierto de Atacama chileno

“…Burkart, Prosopis alba Griseb, Prosopis flexuosa DC, Prosopis burkartii Muñoz, Prosopis strombulifera (Lam.) Benth and Geoffroea decorticans Burkart (Burkart, 1976;Calderon et al, 2015;Carevic et al, 2015;McRostie et al, 2017;Garrido et al, 2018;Contreras et al, 2018). Indeed, G. decorticans, locally known as "chañar", has a wide geographic distribution across the Atacama Desert.…”

“…This species can be found in northern Chile, from 18°29'S to 30°2'S of latitude, and in the 3-3,000 meters above sea levels (masl) range (Contreras et al, 2018). Despite this, genetic studies on arid zones' forests and resources including G. decorticans are scarce and scattered (Calderon et al, 2015;Contreras et al, 2018;Garrido et al, 2018). Chañar reproduces by seeds or by gemiferous roots (Giménez et al, 2013).…”