Influence of herbaceous competitors on early growth in direct seeded Fagus sylvatica L. and Quercus robur L.

Compared to planting of bare-rooted seedlings, direct seeding of broadleaves for afforestation of farmland has the potential of becoming an effective low-cost alternative. In an experiment carried out in an abandoned field in the southernmost part of Sweden, four treatments including herbicide; herbicide in combination with fertilization; mowing and undisturbed control were applied. Growth and the development of direct seeded beech ( Fagus sylvatica L.) and oak ( Quercus robur L.) were monitored over three years and interpreted according to resources availability. Herbaceous competitors clearly decreased growth in seedlings. Mowing treatment had no effect on seedling growth and development when compared to the undisturbed control treatment. Soil and leaf water potentials indicated that herbaceous vegetation competed with the seedlings mainly for soil water. Moreover, fertilization in combination with herbicide treatment had no additional effect on growth or leaf nitrogen levels. The results indicate that seeded beech and oak are equally sensitive to herbaceous competition although oak was more deeply rooted than beech.