Jose Angel Morales Sanchez studied how bryophytes and lichens tolerate climate change in his docoral thesis

The thesis was supervised by Associate Professor Kristiina Mark and Professor Ülo Niinemets of the Estonian University of Life Sciences. The opponent was Professor Alicia V. Perera-Castro (University of the Balearic Islands, Spain).

Intracellular water is essential for the functioning of living organisms. Water loss generally causes cellular damage and, in severe cases, can lead to the death of the organism. Bryophytes and lichens are among the few organisms capable of surviving complete desiccation and resuming their vital functions upon rehydration. However, desiccation tolerance varies considerably among species. Knowledge of how this trait adapts to different climatic conditions remains limited.

The doctoral thesis investigated the physiological responses of bryophytes and lichens to cycles of drying and rewetting and examined how these responses depend on environmental conditions. The study evaluated existing research methodologies and analysed changes in photosynthesis, carbon balance, chlorophyll fluorescence, and volatile organic compound (VOC) emissions.

The results showed that protocols currently used to assess desiccation tolerance are highly variable. To improve comparability among studies, there is a need for standardized measurement methods and broader taxonomic and ecological coverage. As part of the thesis, a novel gas-exchange system developed by the research group was tested. The system enables real-time monitoring of physiological changes during drying and rehydration cycles through an innovative in-chamber humidification system. This approach improved the monitoring of recovery processes and made it possible to link physiological measurements with volatile compound emissions.

The improved methodology was also used to assess the long-term effects of elevated carbon dioxide (CO₂) concentrations on desiccation tolerance in bryophytes. The results demonstrated that although photosynthesis increased temporarily under elevated CO₂, the effect was not sustained over time, and desiccation tolerance declined in all four bryophyte species studied by the end of the experimental period.

The doctoral thesis provides an important overview of the current state of research on desiccation tolerance in bryophytes and lichens and highlights the importance of standardized methodologies and multi-species studies for understanding and predicting the impacts of climate change.

The doctoral thesis is available in the Estonian University of Life Sciences digital repository, EMÜ DSpacelink opens in new page.