Urban forest regeneration: Responses of Scots pine seedlings to partial humus removal in mid-boreal N-enriched forests

Nitrogen (N) deposition results in accumulation of N-rich organic matter in urban forests. Partial removal of vegetation and humus layer (REMOVAL treatment) was used to reduce N content of soil and to improve the establishment and performance of planted Scots pine (Pinus sylvestris L.) seedlings in urban boreal forest sites. Corresponding rural sites of a similar forest type with background N deposition were used as a reference. The REMOVAL treatment increased shoot and root biomass of the seedlings, but did not affect fungal biomass in the roots. The treatment decreased peroxidase activity, an indicator of physiological stress, in roots, which suggests an overall improvement of soil conditions. Present results thus imply amelioration of stress in Scots pine roots in urban soil environment by partial removal of vegetation and the humus layer.

► Partial removal of vegetation and humus layer (REMOVAL treatment) was used to reduce N content of soil in urban boreal forest sites. ► A further aim was to improve establishment and performance of planted Scots pine (Pinus sylvestris L.) seedlings. ► REMOVAL increased shoot and root biomass of the seedlings, but did not affect fungal biomass in the roots. ► REMOVAL decreased peroxidase activity, an indicator of physiological stress, in roots, which suggests an overall improvement of soil conditions.