Fine root vitality decline results in reduced branch formation in mature beech stands after drought

Climate change is deteriorating the health, growth and thus functioning and services of forests through ongoing droughts and an increase in the severity of these effects is predicted. Although fine roots can serve as an early indicator of drought stress, we still lack a basic understanding of how tree fine root vitality is reflected in aboveground tree morphology.

Our study uses multitemporal fine root data obtained by sequential coring, as well as high-resolution tree crown data obtained by terrestrial laser scanning in mature European beech (Fagus sylvatica L.) stands. First, we assessed which fine root vitality traits are affected by drought, and second, evaluated the relationship between fine root vitality and crown vitality. The models included trees within three different radial distances (5, 8 or 10 m) from the fine root sampling point and different tree collectives (all or only (co)dominant trees) (Fig. 1).

We found that fine root necromass, fine root biomass to necromass ratio and turnover were correlated with drought. Mainly fine roots in the upper 10 cm of soil affected the crown vitality of beech trees within a 5-m radius of the fine root sampling point, highlighting the tree-centred horizontal distribution of fine roots and shallow rooting pattern of beech. A decreased fine root vitality in the upper soil in the previous growing seasons led to decreased crown vitality.

Including fine root inventories in forest monitoring protocols could substantially improve our understanding of the status and trends of forests and enable forest management to deal more effectively with the growing pressure on forests.

Koller, A.; Azekenova, A.; Feger, K.-H.; Kalbitz, K.; von Oheimb, G. (2026): Fine root vitality decline results in reduced branch formation in mature beech stands after drought. In: Forest Ecology and Management 605. DOI: 10.1016/j.foreco.2026.123506.

Additional information to the BENEATH experiment:
Julich, S.; Azekenova, A.; Wordell-Dietrich, P.; Schäfferling, R.; Koller, A.; Kniesel, B.; Fontenla-Razetto, G.; Zeh, L.; Feger, K.-H.; von Oheimb, G.; Kalbitz, K. (2025): Theoretical and Methodological Framework for Monitoring Feedback Mechanisms Among Soil Moisture Dynamics, Soil Organic Matter and Deadwood in Forests. In: Journal of Plant Nutrition and Soil Science. DOI: 10.1002/jpln.12008.