Increasing use of bioenergy in Sweden will lead to an increase in the recyc
ling of wood ash to forest soils. Among anticipated negative effects of woo
d-ash recycling are salt- and/or pH shocks that would be detrimental to gro
und vegetation and the soil biota and an increase in release of heavy metal
s, in particular cadmium (Cd). In the present study, the population density
of enchytraeids was used as an indicator of wood-ash effects in a series o
f held experiments in stands of Norway spruce (Picea abies (L.) Karst.), or
mixed Norway spruce and Scots pine (Pinus sylvestris L.), in Sweden. The a
bundance of enchytraeids in wood ash, wood ash + ammonium nitrate or wood a
sh + lime treatments was not significantly different from that in untreated
controls. Treatment with a high dose (8 t ha(-1)) of a hardened and crushe
d ash with high content of readily soluble salts caused a downward movement
of the enchytraeids from the upper 0-1 cm of the soil profile. At one site
the Cd content in the dominating enchytraeid species Cognettia sphagnetoru
m increased in the year after ash application, but decreased again during t
he following two years to the same level as in the control. The results ind
icated that the earthworm population might increase after wood-ash applicat
ion. It is concluded that none of the ash types used in the experiments is
likely to cause any pH or salt shock to the enchytraeids if applied in dose
s recommended to compensate for harvest of slash.