Forest ditch cleaning and its effect on mobilization of an old soil carbon store

In order to convert to a fossil-free society, one suggested strategy is to improve the forest productivity. A higher forest productivity will, in addition to increasing the forest raw material, also mitigate climate change in a cost-effective way by increasing carbon sequestration in biomass and soils.

One way to maintain or improve forest productivity is to improve the drainage by ditch cleaning. However, by physically disturbing the near-stream zone in combination with lowering the groundwater table of the catchment, ditch cleaning could potentially mobilize an old and previously stable carbon store from deeper soil horizons or from peat-rich areas. Such a mobilization of aged carbon could have a negative feedback on the climate and in turn have consequences for current forest management strategies.

The project aims to answer:

1. What are the effects of forest ditch cleaning on the age composition of terrestrial carbon being exported to surface waters?
2. If ditch cleaning results in a mobilization of aged carbon, when does it occur and for how long do the mobilization last?

During the project intensive monitoring of ground and stream water will be made within controlled experimental catchments where both forest harvest and ditch cleaning will be conducted.

Participants from SLU

• Alberto Zannella
• Karin Eklöf
• Hjalmar Laudon
• Eliza Hasselquist
• Marcus Wallin