Differences in functional and xylem anatomical features allow Cistus species to co-occur and cope differently with drought in the Mediterranean region

Abstract

A significant increase in drought events frequency is predicted for the next decades induced by climate change, potentially affecting plant species mortality rates and distributions worldwide. The main trigger of plant mortality is xylem hydraulic failure due to embolism and induced by the low pressures at which water is transported through xylem. As the Mediterranean basin will be severely affected by climate change, the aim of this study was to provide novel information about drought resistance and tolerance of one of its most widely distributed and common genera as a case study: the genus Cistus. Different functional and anatomical traits were evaluated in four co-occurring Cistus species in the Mediterranean Montado ecosystem. Soil water availability for each species was also assessed to evaluate if they show different ecological niches within the area. Results showed physiological and xylem anatomical differences between the four co-occurring species, as well as in the soil water availability of the sites they occupy. Despite the significant differences in embolism resistance across species, no trade-off between hydraulic safety and efficiency was observed. Interestingly, species with narrower vessels showed lower resistance to embolism than those with higher proportions of large conduits. No correlation, however, was observed between resistance to embolism and wood density. The four species showed different water-use and drought-tolerance strategies, occupying different ecological niches that would make them cope differently with drought. These results will allow us to improve the predictions about the expected changes in vegetation dynamics in this area due to ongoing climate change.

Assessing inter- and intraspecific variability of xylem vulnerability to embolism in oaks

“…Jacobsen et al (2005) found that the effect of vessel density on embolism resistance is due to its role in modifying fiber properties in wood. A reverse pattern was observed in the genus Cistus , where species with narrow vessels were found to be more prone to xylem embolism in the Mediterranean region (Torres-Ruiz et al ., 2017b). Gleason et al (2016) tested this trade-off across many angiosperms and gymnosperm species and found a positive correlation between hydraulic conductivity and P 50 and concluded that there is a weak tradeoff between hydraulic efficiency and safety among species.…”

Living on the edge: A continental‐scale assessment of forest vulnerability to drought

“…When we considered only Eucalyptus species, additional patterns emerged; most notably, D h and maximum K s were related negatively to P 50 . This suggests that both metrics of the postulated trait coordination along an axis of hydraulic safety and efficiency, represented by embolism resistance and conduit diameter as referenced above (Cai & Tyree, 2010; Ellmore & Ewers, 1985; Hargrave et al, 1994), or as embolism resistance and maximum conductivity (Martínez‐Vilalta et al, 2002; Tyree et al, 1994; Zimmermann, 1983), which researchers have struggled to conclusively demonstrate (Gleason et al, 2016; Torres‐Ruiz et al, 2017), do emerge among closely related species—likely obscured by divergent environmental adaptations in the larger plant community.…”

Genetic differentiation in functional traits among European sessile oak populations

“…the xylem pressure inducing 50% of PLC, were obtained by averaging the values of 13 to 15 samples per provenance. The P 50 value is commonly used as a proxy for tree drought resistance: the lower the P 50 value, the more drought tolerant the species (Delzon 2015, Torres-Ruiz, Cochard, Fonseca, et al 2017.…”