The combination of high leaf hydraulic safety and water use efficiency allows alpine shrubs to adapt to high-altitude habitats

Leaf hydraulic traits are considered the key determinants of gas exchange and therefore affect species distributions along environmental gradients, but the patterns of leaf hydraulic traits and their associations with gas exchange across altitudinal gradients remain largely unknown. Here, we measured leaf hydraulic traits, gas exchange, leaf anatomical traits and plant size traits in two dominant alpine shrubs (Caragana jubata and Salix gilashanica) across an altitudinal gradient from 3100 to 3700 m. The findings indicated that with increasing altitude, both shrub species exhibited an increase in leaf hydraulic safety (more negative Kleaf P50), a decrease in leaf hydraulic efficiency (Kleaf-max) and an increase in intrinsic water use efficiency (WUEi), thus allowing them to adapt to higher altitude habitats. The more negative Kleaf P50 was associated with a greater ratio of major to minor vein density (VLAmaj/VLAmin), the lower Kleaf-max was associated with a lower minor vein density (V..., Study site and shrub species
This study was conducted in the Pailugou catchment of the Qilian Mountains (100°17´E, 38°24´N), Gansu Province, Northwest China. The altitude of this catchment ranges from 2700 m to 3700 m. Meteorological variables, including the growing season temperature (GST, °C), growing season precipitation (GSP, mm) and relative humidity (RH, %) were recorded by an automatic forest ecological station (the four monitoring points are at 2700 m, 2900 m, 3300 m and 3700 m) from 2018-2021. The vapor pressure deficit (VPD, kPa) was calculated via the following equations based on the meteorological data:VPD=0.61078×e(17.27×GST)/ (GST+237.3) ×(1-RH)(Tang et al., 2023). The GST decreased from 11.5°C to 6.0°C, the GSP decreased from 337.1 mm to 153.1 mm, the RH ranged from 57.4% mm to 64.6% and the VPD ranged from 0.58 kPa to 0.33 kPa from 2700 m to 3700 m during the growing season (see Figure S1 in Supporting Information).
The vegetation types are semiarid mountain steppe, moun..., , # The combination of high leaf hydraulic safety and water use efficiency allows alpine shrubs to adapt to high-altitude habitats

[https://doi.org/10.5061/dryad.p5hqbzkz1](https://doi.org/10.5061/dryad.p5hqbzkz1)

## Description of the data and file structure

We have submitted our raw data, including the leaf hydraulic traits, gas exchange, leaf structural and plant size traits from two dominant alpine shrubs (*Caragana jubata* and* Salix* *gilashanica*) across a broad altitudinal range (3100–3700 m) in the Qilian Mountains to reveal the patterns of leaf hydraulic traits and their relationships with gas exchange and to advance our understanding of the mechanisms of species distribution along altitudinal gradients.

Data_table contains 18 morphological, anatomical and physiological traits and results of analysis of variance for the difference across altitude (one-way ANOVAs) in Caragana jubata and Salix gilashanica

PH: Plant height (cm)

LA: Leaf area (cm2)

VLAmaj: Major vein len...