How does soil water potential limit the seasonal dynamics of sap flow and circumference changes in European beech?

Abstract

We focus on the analysis of sap flow and stem circumference changes in European beech (Fagus sylvatica, L.) in relation to available soil water and weather conditions during the growing seasons 2012 and 2013. The objective was to examine how soil water potential affects growth and transpiration of a mature beech stand situated at the lower distributional limit of beech in Slovakia. To be able to evaluate beech response to soil water shortage, we irrigated a group of 6 trees during the period of pronounced drought, while the control group of other 6 trees remained exposed to actual weather conditions. Mean air temperatures of both seasons were considerably above the long-term average and the temporal pattern of precipitation differed between the years. During the whole growing season 2012, beech samples transpired an average volume of 6.9 m3 of water in the control and 7.7 m3 in the irrigated group. A slightly higher average volume was found in the growing season 2013 under both treatments (7.7 m3 in control and 10.5 m3 in irrigated trees). In the drought period 2012, when the irrigation experiment was commenced, the sap flow in the control group was reduced by 30% as compared with the irrigated group. In 2013, a 38.1% difference in sap flow was observed between the groups. Sap flow in the non-irrigated trees decreased with reducing soil moisture, and ceased at soil water potential -0.6 MPa. In both treatments and years, we found significant correlations between hourly sap flow and investigated weather variables. A reduction in stem circumferences of the control trees, which was observed during stem shrinkage phase, was up to 19% in 2012 and 10% in 2013. We conclude that stem circumference shrinkage during the peak of soil drought was induced by the cessation in the sap flow process.

Sap flow in response to rainfall pulses for two shrub species in the semiarid Chinese Loess Plateau

“…This is consistent with previously reported results (Gallé et al, 2007;Sánchez-Blanco et al, 2002). The reason for the increment of water potential drops maybe that droughtinduced embolism is promptly refilled after rainfall (Sitková et al, 2014). In fact, the leaf provides probably the best environment for refilling of embolized conduits (Salleo et al, 2001) due to the relative abundance of inorganic ions and other osmolytes that could be used to generate positive pressures as well as possessing large amounts of metabolic energy to drive ion movement.…”

Identifying the relationships of climate and physiological responses of a beech forest using the Standardised Precipitation Index: a case study for Slovakia

“…This solution is based upon the published results (Ježík et al, 2015;Sitková et al, 2014) that confirmed the significant impact of soil water potential (which in the figurative sense means drought) on physiological responses of tree species, in our case European beech. The search for the highest correlation followed the methodological procedure presented above.…”

Drought and irrigation affect transpiration rate and morning tree water status of a mature European beech (Fagus sylvatica L.) forest in Central Europe

“…The area belongs to the oak–beech altitudinal forest belt, and the soil is classified as Haplic Cambisol (Humic, Eutric, Endoskeletic, and Siltic) formed on volcanic parent material. A more detailed description of soil properties at the Bienska study site is given in Sitková et al ().…”