Carbon turnover in forest and grassland soils - will global warming turn carbon sinks into sources?

Soil sustainability PhD studentship summary.
Eleanor Swain, University of Newcastle, 2008-2011.


Coalburn Forest
Coalburn Forest. A typical afforested Sitka Spruce stand.

This project is designed to study the fundamental processes controlling carbon cycling in soil within natural and managed ecosystems. This study aims to provide a detailed and comprehensive SOM characterisation across a broad range of plant sources, degradation states and environmental conditions in peatlands and afforested peatlands using THM in the presence of TMAH. This will allow an increased understanding of SOM storage and transformations during land use change, from pristine peatland to afforested peatland.


Northern peatlands cover an area of around 350x106 ha, and store around one-third of global soil carbon (C) (Gorham, 1991) and as a result are very important carbon sinks. The afforestation of these carbon rich peatlands has been the largest land use change in Great Britain over the past 100 years, with 315,000 ha of shallow peatlands planted with coniferous forest (Hargreaves et al., 2003). However, the effect this may have on the carbon storage is unknown.

In order to obtain a clearer picture of the processes occurring after afforestation, it is vital to understand the range of both lignins and polyphenolic compounds (e.g. from peat mosses) present prior to the land use change. This will allow us to determine the role of aged peat moss phenolics on the current soil organic carbon, and be aware that the markers found in the pristine peat can be used as tracers within the afforested peat.

This project uses thermally assisted hydrolysis and methylation (THM) in the presence of labelled and 13C-labelled tetramethylammonium hydroxide (TMAH) in order to identify intact lignin, demethylated lignin and non-lignin phenols.

Key hypotheses

The increasing mass of litter quantity as a direct result of afforestation, will lead to an accumulation of lignins and tannins, and thus an increasing soil organic carbon stock:
→ Compare a pristine peat ecosystem to an afforested peat ecosystem

Determine the role of aged peat moss phenolics on soil organic carbon in afforested habitats:
→ Establish peat moss phenolic fingerprint.

Land preparation prior to afforestation will cause a peak of phenolic compounds at depth due to horizon inversion, thus creating a stable carbon sink:
→ Using Harwood as our land preparation site.

Determine if self seeded Sitka Spruce affect the phenolic composition and carbon storage down the profile:
→ Analyse a chronosequence from open bog through to peat under self seeded Sitka spruce (Wark Forest).


Dr Eleanor Swain
University of Newcastle