Changes to C stocks in Scottish soils due to afforestation

Summary

This project was commissioned by Forestry Commission to provide more robust evidence and quantification of the changes in soil carbon stocks and other properties in land use conversion to forestry. The project was led by JHI and involved re-sampling of the sites from the National Scottish Soil Survey which have undergone land use change to forestry in the past 30-40 years.  A review of the soil data held in the Scottish Soils Database at The James Hutton Institute identified 40 sites on land owned by the Forestry Commission (FC) that had been afforested subsequent to the original description and sampling of the soil. These sites provided an opportunity to assess the extent of changes in soil carbon over time for a range of soil types and under different tree species.

Research objectives 

The aims of this project were to:

  • relocate these sites and collect new soil morphological data,
  • analyse the samples for a range of soil properties (but primarily soil organic carbon concentration),
  • assess and calculate the changes in soil carbon stocks

Fixed depth sampling alongside the traditional sampling by horizon (layers) was included as a way of attempting to integrate the BioSoil and NSIS sampling schemes in order to develop a more substantial database of afforested soils in Scotland.

Results

This research demonstrated that long-term afforestation of soils previously under moorland vegetation generally leads to an increase in soil carbon, expressed either on a total change or annual change basis and that this increase can largely be accounted for by the increase in thickness and carbon content of the litter layer. Data from this project will be used as input into models and site assessments to evaluate the amount of above- and below-ground carbon that is stored within the soils and trees. 

Status

Project completed in 2016, with further research ongoing.

Contact

Dr Elena Vanguelova

Funders and partners

Research collaborators include:

• CFS/FC Scotland

The James Hutton Institute

Forestry Commission policy

At the core of the Government's policy on sustainable forest management is the need to safeguard soil and water resources. Human actions, from local scale forest operations to international scale climate change and air pollution may compromise forest soil sustainability with consequential impacts on the freshwater environment. Poorly planned and managed forests can severely degrade soil and water resources, making forests more vulnerable to climate change. Good management, in contrast, seeks to maintain and enhance the natural protective functions of forests and the benefits they provide for society, including carbon sequestration, clean water and reduced flood risk. The overall objective of this programme is to evaluate through measuring, modelling and mapping the impacts of forests, woodlands and management practices on soil and water resources under a changing climate and changing pollutant emissions. It also aims to quantify the benefits of woodland creation for soil, water and flood management and evaluate the role of woodland in integrated catchment management. The findings will improve our understanding of the nature of these impacts and be used to help develop practices and guide future policy to secure the soil and water services that underpin the multiple benefits provided by forests.