Key message

The lack of elevational changes in electrical resistivity in Pinus cembra trunks indicated consistent growth and hydraulics across elevations. Though, electrical resistivity tomograms exhibited pronounced temperature-driven seasonal changes.

Abstract

Alpine conifers growing at high elevation are exposed to low temperatures, which may limit xylogenesis and cause pronounced seasonal changes in tree hydraulics. Electrical resistivity (ER) tomography enables minimal invasive monitoring of stems in situ. We used this technique to analyze Pinus cembra trunks along a 400 m elevational gradient up to the timberline and over seasons. Furthermore, ER data of earlywood across tree rings were compared with the respective specific hydraulic conductivity (K_S), measured on extracted wood cores. ER tomograms revealed pronounced changes over the year and a strong correlation between average ER (ER_mean) and air and xylem temperatures. Surprisingly, no elevational changes in ER_mean, earlywood ER or K_S were observed. ER data corresponded to variation in earlywood K_S, which decreased from the youngest (ca. 4–5 cm²s⁻¹ MPa⁻¹) to the oldest tree rings (0.63 ± 0.22 cm²s⁻¹ MPa⁻¹). The lack of changes in ER data and earlywood K_S along the study transect indicated consistent growth patterns and no major changes in structural and functional hydraulic traits across elevation. The constant decrease in earlywood K_S with tree ring age throughout all elevations highlights the hydraulic relevance of the outermost tree rings in P. cembra. Seasonal measurements demonstrated pronounced temperature effects on ER, and we thus recommend a detailed monitoring of trunk temperatures for ER tomography.

中文翻译：

---

洞察松树树干：通过电阻率断层扫描进行水力学分析。

 关键信息

西伯拉松树干的电阻率没有随海拔变化而变化，这表明不同海拔地区的生长和水力保持一致。不过，电阻率断层图显示出明显的温度驱动的季节性变化。

 抽象的

在高海拔地区生长的高山针叶树暴露在低温下，这可能会限制木质生长并导致树木水力学发生明显的季节性变化。电阻率 (ER) 断层扫描可以对茎进行原位微创监测。我们使用这种技术来分析沿 400 m 海拔梯度直至林线的松树树干以及整个季节的情况。此外，将跨树轮的早材的 ER 数据与在提取的木芯上测量的各自的比导水率 ( K _S ) 进行比较。 ER 断层扫描显示一年中发生了明显的变化，并且平均 ER（ER_平均值）与空气和木质部温度之间存在很强的相关性。令人惊讶的是，没有观察到 ER_平均值、早材 ER 或K _S的海拔变化。 ER 数据对应于早材K _S的变化，其从最年轻的年轮（约 4–5 cm ² s ^-1 MPa ^-1 ）到最老的年轮（0.63 ± 0.22 cm ² s ^-1 MPa ^-1 ）下降。沿研究样带的 ER 数据和早材K _S没有变化，表明生长模式一致，并且整个海拔的结构和功能水力特征没有重大变化。所有海拔地区早材K _S随树木年轮年龄不断减少，凸显了P. cembra最外层树木年轮的水力相关性。季节性测量表明温度对 ER 有显着影响，因此我们建议对躯干温度进行详细监测以进行 ER 断层扫描。