G. Norberg et al., Control of heather (Calluna vulgaris (L.) Hull) by steam treatment: Effects on establishment and early growth of Scots pine, NEW FOREST, 21(2), 2001, pp. 187-198
Following boreal forest ecosystem disturbance, such as fire and clear-cutti
ng, the ericaceous species Calluna vulgaris often becomes completely domina
nt and may convert forestland into heathland. Calluna is known to effective
ly exclude other vegetation and causes ``growth check'' or stagnation of co
nifer seedlings to result in poor tree regeneration. In this study we inves
tigated the use of steam treatment as an alternative method for vegetation
control of Calluna vulgaris. Scots pine (Pinus sylvestris L.) establishment
and growth were recorded in both a planting and a seeding experiment. Stea
m treatment was compared with mechanical soil scarification and intact vege
tation in the planting experiment and with intact vegetation in the seeding
experiment. The results show that the vegetation is still strongly reduced
five years after the treatment. The steam treatment strongly favoured the
establishment and growth of both seeded and planted Scots pine. The planted
seedlings grown in the steam treated plots had a dry weight more than twic
e as high when compared to scarified plots. Seedling height and basal diame
ter were also highest for seedlings grown in steamed plots. Seedlings plant
ed in scarified plots did not grow as well during the first years possibly
due to injuries caused by frost heaving. The seeding experiment showed an i
ncreased establishment and growth of Scots pine seedlings in steam treated
plots compared to in intact vegetation.