We analyzed the seasonal patterns of sap flow density (Q _s) and stem radius variation (SRV) of Spartocytisus supranubius, a dominant, endemic tree-like shrub of the mountain vegetation at high elevation in Tenerife, Canary Islands. We tested the hypotheses that drought and its effect on water status and on radial growth (RG) is primarily related to cool–wet-season precipitation preceding the current year rather than to the dry summer per se. During 2013 and 2014 Q _s and SRV were monitored with Granier-type sap flow sensors and automatic band dendrometers, respectively. Tree water deficit (ΔW) was extracted from SRV, and standard meteorological factors were used to calculate daily reference evapotranspiration (ET _r) and soil moisture deficit. In both years investigated Q _s was highest during the dry summer coinciding with periods of high ET _r, indicating that plants were able to tap water from deep soil layers originating from precipitation prior the current year’s growth. The high RG and low ΔW rates observed throughout both dry summers are consistent with a direct access of tap roots to deep soil water reserves. Seasonal variations in RG of S. supranubius were mainly determined by the course of Q _s and thus dependent on temperature and tree water status.

中文翻译：

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加那利群岛特内里费岛高寒区的树液的流动和季节性变化

我们分析了Spartocytisus supranubius的树液流动密度（Q _s）和茎半径变化（SRV）的季节性模式，Spartocytisus supranubius是加那利群岛特内里费岛高海拔山地植被的一种占主导地位的特有树状灌木。我们检验了以下假设：干旱及其对水状况和径向生长（RG）的影响主要与今年之前的凉湿季节降水有关，而不是与干旱的夏季本身有关。在2013年和2014年，分别使用Granier型树液流量传感器和自动带式密度计监测Q _s和SRV。树木缺水量（ΔW）是从SRV中提取的，并使用标准气象因子来计算每日参考蒸散量（ET _r）和土壤水分亏缺。在这两个年份中，在干旱的夏季和较高的ET _r期间，Q _s最高，这表明植物能够从今年生长之前的降水产生的深层土壤中提取水。在整个干旱的夏季都观察到较高的RG和较低的ΔW速率，这与直根直接进入深层土壤水储量相一致。S的RG的季节变化。上呼吸道主要由Q _s的过程决定 因此取决于温度和树木的水状态。