The drought effect on circadian dynamics of stem growth

Bc. Jorge Palmero Barrachina

Master's thesis

Abstract:

ABSTRACT Nowadays, Norway spruce (Picea abies (L.) Karst.) is the most threatened commercial tree species in Central Europe. The main reason for that is because of drought stress which is increasing both in frequency and intensity due to climate change. Automatic band dendrometers can evaluate tree water status and determine tree circadian phases. These two parameters are significantly correlated with growth and tree vitality. This study was focused on the description of circadian phases of Norway spruce during which years using data from 25 trees in Kostelec nad Černými Lesy, Czech Republic. Drought stress, bark beetle attack, and the combination between these two stress factors were evaluated. To calculate the distribution of circadian phases the package “dendrometeR” was used in the free software R studio. The drought stress was evaluated by comparing dry and control periods with the same day of the year. The effect of bark beetle attack was tested by using a generalised linear model with negative binomial distribution and likelihood-ratio test. Our description of the circadian phases showed that Norway spruce trees were physiologically active during the months of January to March. Months with less rainfall showed the smallest amount of Stem Radius Increment (SRI). The month of June showed the highest SRI values, being also the month with more precipitation. The duration of circadian cycles kept almost constant during these months. Contraction phase was significantly longer during the dry period. In terms of stem size variation, the expansion and SRI phases showed significantly lower values in the dry period. Healthy and attacked trees responded independently during the dry period. The evaluation of plant water status showed that trees were almost not transpiring during the dry period. Precipitation was the strongest meteorological variable that can influence the SRI. Sap flow was significantly correlated with contraction phase. We propose that bigger samples of bark beetle attacked trees with automatic dendrometers should be analysed after and before the attack.

Keywords

diurnal cycle, drought, stem growth, transpiration, dendrometer

Language used: English

Date on which the thesis was submitted / produced: 9. 4. 2022

Thesis defence

• Supervisor: doc. Ing. Ivana Tomášková, Ph.D.

Czech University of Life Sciences Prague

Faculty of Forestry and Wood Sciences

Master programme / field:
Forestry Engineering / Forest Engineering