Storms and windthrows have significant effects on soil GHG emissions and processes

The IBFRA conference is organised for the 20th time this year with a focus on Climate Resilient and Sustainable Forest Management. This bi-annual conference brings together researchers, companies, policymakers, and members of civil society to discuss the future of boreal forests.

One of the EU-funded project HoliSoils’ highlights in IBFRA is a poster presentation by Qian Li, a post-doctoral researcher from the Natural Resources Institute Finland (Luke). You can meet her on Wednesday 30th of August to hear about the new research results with the topic “Greenhouse gas (GHG) emissions, organic carbon pool and microbial biomass in peatland forests soils under disturbance”.

Two experiments to examine the impact of disturbances

One of HoliSoils’ project objectives is to understand the response of soil to natural disturbances, focusing on examining soil resilience and recovery. Storms and windthrows are important disturbances in boreal forests that cause damage to stand structure and can also impact on soil.

Forest soil contains more carbon than trees, while its response to disturbances has been less studied. To examine how soil carbon stock, greenhouse gas emissions and microbial community are affected by disturbances, experiments were conducted in a spruce-dominated nutrient-rich drained peatland forest site in southern Finland.

Two soil disturbance treatments were established in September 2021 and compared with a control site:

1) Surface soil was removed to simulate the effects of uplifting surface soil by uprooted trees

2) Soil surface was covered by residuals to simulate the excess nutrient input to soil by the canopy of felling trees

The greenhouse gas (CO2, CH4, and N2O) fluxes were measured throughout the snow-free period. After one year, soil samples from two treatment sites and the control site were taken to analyse inorganic nitrogen, stable and labile soil organic carbon (SOC) pool, tannins, and microbial biomass.  

The results after one year

In the first year after treatment, CO2 emissions from topsoil-removed plots decreased. The CH4 sink also declined, even switched to CH4 source when the water level was high, indicating the role of surface soil and its microbes in regulating GHG emissions. The CO2 and N2O emissions increased with residual cover, suggesting the nitrogen input and microclimate change affecting soil microbial processes. Fungal biomass and necromass markers decreased under both treatments compared with the control. However, the organic carbon pool remained stable in the first year of treatment.

“We found a fast response of GHG emissions and microbial community to disturbances, which could lead to a change in the soil C stock.”, says Qian Li

Such soil disturbances can also be found after harvesting or mechanical site preparation, thus causing high spatial variation of GHG emissions. Research results indicated that disturbances on soil have significant effects on soil GHG emissions and processes, and this should be taken into account in the models used for GHG inventory and scenarios.

Qian Li’s background is in peatland greenhouse gases (GHG) emissions and carbon (C) cycle under the effect of climate warming. In the HoliSoils project, her research focuses on how forest management and natural disturbances affect the GHG emissions and soil processes of peatland forests.

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