Multiple strategies for drought survival among woody plant species

Abstract

Summary1. Drought-induced mortality and regional dieback of woody vegetation are reported from numerous locations around the world. Yet within any one site, predicting which species are most likely to survive global change-type drought is a challenge. 2. We studied the diversity of drought survival traits of a community of 15 woody plant species in a desert-chaparral ecotone. The vegetation was a mix of chaparral and desert shrubs, as well as endemic species that only occur along this margin. This vegetation boundary has large potential for drought-induced mortality because nearly all species are at the edge of their range. 3. Drought survival traits studied were vulnerability to drought-induced xylem cavitation, sapwood capacitance, deciduousness, photosynthetic stems, deep roots, photosynthetic responses to leaf water potential and hydraulic architecture. Drought survival strategies were evaluated as combinations of traits that could be effective in dealing with drought. 4. The large variation in seasonal predawn water potential of leaves and stem xylem ranged from À6Á82 to À0Á29 MPa and À6Á92 to À0Á27 MPa, respectively. The water potential at which photosynthesis ceases ranged from À9Á42 to À3Á44 MPa. Architecture was a determinant of hydraulic traits, with species supporting large leaf area per sapwood area exhibiting high rates of water transport, but also xylem that is vulnerable to drought-induced cavitation. Species with more negative midday leaf water potential during the growing season also showed access to deeper water sources based on hydrogen isotope analysis. 5. Drought survival mechanisms comprised of drought deciduousness, photosynthetic stems, tolerance of low minimum seasonal tissue water potential and vulnerability to drought-induced xylem cavitation thus varied orthogonally among species, and promote a diverse array of drought survival strategies in an arid ecosystem of considerable floristic complexity.

Plant resistance to drought depends on timely stomatal closure

“…Overall, the model analysis presented here demonstrates that multiple measurable drought resistance traits can be integrated into a consistent and thermodynamically reliable formal framework to define drought‐induced mortality (Pivovaroff et al . ). This modelling approach must be validated carefully against the temporal dynamics of water potential, hydraulic conductance, data for embolism proper, and experimental and field mortality for different species.…”

Stomatal behaviour and stem xylem traits are coordinated for woody plant species under exceptional drought conditions

“…For example, when water was available and atmospheric demand was low, such as during cool and wet winter climatic conditions, midday water potentials converged among study species (Figure ). However, when temperatures warmed and water became limiting, the diversity of drought response mechanisms associated with these traits led to a wide range of minimum seasonal water potentials (Pivovaroff, Pasquini, et al, ). For example, deeply rooted, drought deciduous, and riparian species had high (less negative) minimum seasonal water potentials and less resistant xylem.…”

“…A recent study conducted in a southern California native shrubland found that shallow‐rooted species with cavitation resistant xylem experienced the highest mortality levels due to drought, whereas deeply rooted species with xylem vulnerable to cavitation had lower mortality levels (Venturas et al, ). This differential mortality among co‐occurring species due to varying drought survival strategies (Pivovaroff, Pasquini, et al, ) may result in changes in community composition and ultimately biodiversity loss. However, predicting mortality remains a challenge for vegetation models due to wide variation in premortality physiological changes among species (Anderegg et al, ; Garcia‐Forner, Sala, Biel, Save, & Martinez‐Vilalta, ; McDowell, ; McDowell et al, ; Pivovaroff, Pasquini, et al, ; Sevanto, Xu, & Way, ).…”

Prevalence and magnitude of groundwater use by vegetation: a global stable isotope meta-analysis

“…This fundamental understanding of water uptake and transport from roots to shoots underlies the utility of stable isotopes in plant water uptake investigations17. While many site-based studies have now been completed18192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114…”