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Drought and bark beetle disturbances drive contrasting water, organic matter and nutrient fluxes of beech, maple, and spruce in Central Germany

Year: 2026

Type: article

Abstract: Extreme climate events are increasingly impacting Central European forests. The 2018 drought and heat wave intensified tree mortality and bark beetle outbreaks. We examined how these disturbances altered water, organic-matter (OM), and nutrient fluxes in mixed beech ( Fagus sylvatica )–maple ( Acer pseudoplatanus ) forests and Norway-spruce ( Picea abies ) stands on shallow, calcareous soils in central Germany. From 2018–2020 we collected bi-weekly samples of throughfall, stemflow, and free-draining lysimeter samples from different soil depths. The samples were analysed for pH, electrical conductivity (EC), dissolved and particulate organic carbon (DOC; POC), total dissolved nitrogen (DN), and nutrients. Linear mixed-effects models revealed strong species responses: mixed beech-maple exported more DN and calcium to deeper soil layers than spruce stands, whereas spruce had significantly higher DOC fluxes at all depths. Radiocarbon signatures indicated that spruce DOC is dominated by recent carbon inputs, while beech/maple DOC incorporates older, previously more stabilized OM. Drought-induced premature leaf fall, subsequent re-wetting events, bark-beetle infestation, and canopy opening contributed to amplify export of OM and nutrients to deeper soil horizons. Bark-beetle infestation of spruce stands mobilized phosphorus from the organic layer. Tree species, the post-drought monitoring phase, and soil depth together explained more than 65% of the variance in water, DOC, DN, Ca, pH, and EC fluxes, confirming that species-specific controls dominate post-drought biogeochemical dynamics. These findings underscore the vulnerability of common Central European forests to the combined pressures of drought and biotic stressors and highlight the importance of incorporating species-specific considerations into forest management adaptations.

Source: Forest Ecology and Management

DOI: 10.1016/j.foreco.2026.124183

Authors: Karin Potthast, Alexander Tischer, Marie-Cécile Gruselle, Susan Trumbore, Beate Michalzik

Institutions: German Centre for Integrative Biodiversity Research, Friedrich Schiller University Jena, ThüringenForst, Norwegian Institute of Bioeconomy Research, Max Planck Institute for Biogeochemistry

Language: English

Topic: Soil Carbon and Nitrogen Dynamics

Subfield: Soil Science

Field: Agricultural and Biological Sciences

Domain: Life Sciences

SDGs: Life on land, Climate action

Open Access status: hybrid

Estimated APC paid: $3,560