Ecohydrological niche segregation among desert shrubs in a gypsum-calcareous formation, north-western Iran

ABSTRACTBackground Xerophilic subshrubs exhibit multiple functional types and frequently show hydrological niche segregation. In the poorly studied Irano-Turanian gypsum deserts, knowledge of the ecohydrological strategies of different plant species is essential to understand community complexity in these vulnerable ecosystems.Aim We studied the ecohydrological strategies of five co-existing subshrub members of Caryophyllales, ascertaining if their rooting architecture, gypsum affinity or photosynthetic pathway determined their water uptake, and if gypsum crystallisation water could be a relevant water source for plants in different seasons.Methods We conducted soil and xylem sampling for isotope analyses in spring and summer and extracted water by cryogenic vacuum distillation. Oxygen and hydrogen isotope compositions were determined and compared with visual representation and Bayesian Mixing Models to determine species ecohydrological strategies.Results Species – season interactions were related to differences in xylem sap isotopic composition. Three basic strategies relying on contrasting the use of free topsoil moisture and deep soil water could be detected and were in part explained by rooting architecture. Plant gypsum affinity and photosynthetic pathways did not have a significant effect on the water sources used by the plants.Conclusions Ecohydrological niche segregation was explained partly by rooting architecture and species-specific traits. Gypsum crystallisation water was not used in summer by the studied species.KEYWORDS: Caryophyllalesdesert subshrubsgypsumIranniche segregationstable isotopeswater use AcknowledgmentsThis paper is in part the result of postdoctoral studies of AR and AS in the Halophytes and C4 Plants Research Laboratory, University of Tehran. The authors would like to express their gratitude to Maryam Malekmohammadi (Halophytes and C4 Plants Research Laboratory, University of Tehran) for her participation in fieldwork. Finally, the authors would like to thank three anonymous reviewers and the editor for their immense help and precious feedback to improve this manuscriptDisclosure statementNo potential conflict of interest was reported by the author(s).Author contributionsHA and SP designed the study; AS, HA, AR, IQ, HR and SP performed fieldwork; AR ran water extractions with contributions from IQ, LP and PF; LP and PF analysed data; HR performed the soil gypsum content analysis; LP and AR led manuscript writing with contributions from all authors.Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/17550874.2023.2255985Additional informationFundingThe study was supported by grants from the Research Council and International Office, University of Tehran, the European Union’s Horizon 2020 research and innovation programme (Project H2020-MSCA-RISE-GYPWORLD GA No. 777803), the Spanish Ministry of Science and Innovation (MICINN, PID2019-111159GB-C31), and the Spanish Research Council (CSIC, I-COOPB20231). The postdoctoral fellowship of AS was founded by the National Elite Foundation. LdP and SP received funding from FSE (Fondo Social Europeo)-Aragón2014–2020 of the Gobierno de Aragón, Spain, and MICINN (RyC fellowship RYC-2013-14164), respectively. JPF was supported by the Reference Group H09_20R (Gobierno de Aragón, Spain).