Coordination between water uptake depth and the leaf economic spectrum in a Mediterranean shrubland

Abstract

1. Water is the most limiting resource for plant survival and growth in arid environments, but the diversity of water-use strategies among coexisting species in dryland communities is not well understood. There is also growing interest in assessing whether a whole-plant coordination exists between traits related to water-use and the leaf economic spectrum (LES).2. We used water stable isotopes (δ 2 H, δ 18 O) to quantify water uptake proportions from different soil depths by 24 species in a Mediterranean shrubland. Leaf traits associated with water-use efficiency, stomatal regulation (δ 13 C, δ 18 O) and the LES (SLA, N, P, K concentrations) were also measured. We assessed potential trade-offs between the above-mentioned leaf traits, water uptake depth and their relationship with species abundance.3. We found distinct ecohydrological niche segregation among coexisting species.Bayesian models showed that our shrubland species used a median of 37% of shallow soil water (0-30 cm) and 63% of deep water (30-100 cm). Still, water source proportions varied considerably among species, as shallow soil water-use ranged from a minimum of 6.4% to a maximum of 68%. Interspecific variability in foliar carbon investment (SLA) and nutrient concentrations was remarkably high, indicating diverse nutrient-use strategies along the LES. Leaf δ 18 O, δ 13 C and δ 15 N values also differed widely among species, revealing differences in stomatal regulation, water-use efficiency and nitrogen acquisition mechanisms.After accounting for evolutionary history effects, water uptake depth was coordinated with the LES: species using shallower soil water from fertile topsoil layers exhibited a more acquisitive carbon-and nutrient-use strategy, whereas water uptake from deeper but less fertile soil layers was linked to a more conservative nutrient-use strategy. Leaf-level water-use traits significantly influenced species abundance, as water-savers with tight stomatal regulation and high water-use efficiency were dominant. Synthesis.Greater utilisation of water stored in nutrient-rich topsoil layers favoured a more acquisitive nutrient-use strategy, whereas a deeper water uptake

Isotopic offsets between bulk plant water and its sources are larger in cool and wet environments

“…A comparison of the isotopic composition of plant water with that of its potential sources has served to infer groundwater uptake in arid and semi-arid environments (e.g. Illuminati et al, 2022;Thorburn et al, 1995;Yin et al, 2015), characterize seasonal shifts in root water up-take across the soil profile (Eggemeyer et al, 2009;Schwendenmann et al, 2015), or unveil the use of alternative water sources such as dew or fog (Burgess and Dawson, 2004). In the past decade, methodological advances, such as novel statistical tools (Stock et al, 2018) and high throughput of samples using laser-based instruments (Martín-Gómez et al, 2015), have allowed for significant increases in the spatiotemporal resolution of water isotope data sets that can be used to infer plant water sources.…”

Effects of post oak (Quercus stellata) and smooth brome (Bromus inermis) competition on water uptake and root partitioning of eastern redcedar (Juniperus virginiana)

“…We found separation of soil-moisture depletion zones by the different treatment combinations, but our study suggests that factors other than water impact the ability of J. virginiana to co-exist with grasses and other woody species. Furthermore, our data suggest that ecohydrological niche separation among coexisting plant species may not occur in the early life stages of woody species and competition for water may change as the plants adopt different plant water-use strategies [48].…”

“…virginiana to co-exist with grasses and other woody species. Furthermore, our data suggest that ecohydrological niche separation among coexisting plant species may not occur in the early life stages of woody species and competition for water may change as the plants adopt different plant water-use strategies [ 48 ].…”

Disentangling the Role of Forest Structure and Functional Traits in the Thermal Balance of the Mediterranean–Temperate Ecotone

“…Furthermore, we found that climatic water availability and the plant water use strategy exert additional controls on the forest thermal balance, probably through transpiration cooling. The coordination of rooting depth and other plant functional traits linked to water‐use strategies (Illuminati et al., 2022) may underlie the association of the considered traits with the response to increased VPD during hot spells, that included canopy cooling in the driest stands of the most drought‐resistant species (Figure 6h). Finally, we also showed that forest structural characteristics related to surface roughness such as tree height and cover, stand density, and albedo also influence the forest thermal balance, as they affect heat dissipation mechanisms (Muller et al., 2021).…”