Forest Topsoil Organic Carbon Declines Under Ash Dieback

Area of Science:

• Ecology
• Forestry
• Soil Science

Background:

• Tree diseases pose a growing threat to global woodland ecosystems.
• The impact of these diseases on soil carbon dynamics remains poorly understood.
• Ash dieback (Hymenoscyphus fraxineus) is a significant disease affecting ash trees.

Purpose of the Study:

• To evaluate the fifty-year trend in topsoil carbon.
• To assess the impact of ash dieback on soil organic matter (SOM).
• To quantify potential soil carbon loss due to ash dieback in Great Britain.

Main Methods:

• Field survey of ~100 woodlands across Great Britain in 1971, 2001, and 2022.
• Measurement of topsoil (0-15 cm) organic matter (SOM).
• Application of Beta mixture modelling within a Bayesian framework to analyze SOM distribution.

Main Results:

• Average SOM remained constant across all woodlands over fifty years.
• Woodlands with ash dieback showed lower SOM compared to those without.
• A modelled mean SOM difference of 1.23 percentage points was observed between plots with and without ash dieback.
• Estimated total topsoil carbon loss due to ash dieback in Great Britain is 6 MtCO2.

Conclusions:

• Ash dieback disease leads to a decline in topsoil organic matter.
• Understanding tree disease impacts is crucial for woodland carbon dynamics.
• The study highlights significant potential carbon loss from ash dieback in British woodlands.