Abstract:

Objective: This study aims to uncover the water adaptation strategies of desert shrubs by exploring their xylem anatomical traits, xylem functional trade-offs, and the impact of phylogenetic and meteorological factors on their anatomical structure. Additionally, this research also aims to establish a theoretical foundation for vegetation preservation and restoration in degraded desert ecosystems. Method: In this study, 18 typical desert shrubs were used as experimental objects, and their xylem anatomical characteristics were examined and compared with those of woody plants across the globe. The typical characteristics of desert shrub xylem were analyzed. The trade-offs between the“mechanical safety, storage, and hydraulic efficiency”of the xylem were assessed using a structural equation model (PLS-PM). The interspecific variability was investigated by integrating phylogenetic analysis and climate factors in the natural distribution areas. Result: 1) Compared with the average of woody plants around the world, desert shrubs displayed a higher vessel fraction, axial parenchyma fraction, and a lower fiber fraction. Compared with the global average of angiosperms, desert shrubs exhibited a higher vessel density and smaller vessel hydraulic diameter. The combination of increased vessel density and reduced hydraulic diameter resulted in the maximum theoretical hydraulic conductivity of desert shrubs being basically consistent with the global average. 2) There were significant variations in wood anatomical characteristics among 18 desert shrubs, and the anatomical traits of plants in the same family showed a certain degree of aggregation in principal component analysis. However, apart from the significant phylogenetic signal observed in vessel density, the phylogenetic signals of other traits were not significant. 3) There was a significant trade-off between mechanical safety and hydraulic efficiency and storage capacity, and there was no significant correlation between hydraulic efficiency and storage capacity. Vessel density was negatively correlated with mean annual temperature, mean temperature of wettest quarter, and mean temperature of warmest quarter, while vessel diameter and vessel wall thickness were positively correlated with those climate factors. On the other hand, annual precipitation did not have a significant effect on anatomical traits. Precipitation seasonality exhibited a significantly positive correlation with vessel wall thickness. However, no significant correlation was observed between annual precipitation, wettest quarter precipitation, warmest quarter precipitation, and anatomical anatomy. Conclusion: The xylem of desert shrubs exhibits drought adaptation features that contribute to reduced mechanical support, increased storage capacity, and maintained hydraulic efficiency. The vessel features of these shrubs are significantly influenced by phylogeny and meteorological factors, while other anatomical traits show no significant effects.

Key words: vessel, fiber, parenchyma, functional trade-offs, climate factor, phylogeny