Effects of retained trees on tree growth and field vegetation in Pinus sylvestris stands in Sweden

As a result of legislation and forest certification schemes, retention of dead and live trees has become common in forest management. This study investigated the effect of retained Scots pines (Pinus sylvestris L.) on production and field vegetation in the new stand. Stem volume per hectare and field vegetation composition at different distances from retained trees were examined for 60 trees on 25 sites at latitudes 55-68 degrees N. The mean ages of the new stands were 30-90 years. The volume of the new stand was reduced within 5-10 in from retained trees. Site fertility, as expressed by the field vegetation, had a large impact on the reduction. The loss of production in the new stand with 10 evenly dispersed retained trees per hectare was estimated at 3.0% on average pine sites and varied in an interval from 1.6 to more than 10% depending on site fertility. The loss was not significantly influenced by the size and growth of retained trees or development stage of the new stand. In the field vegetation, species indicating poor soil conditions were more common close to retained trees, while species demanding higher fertility were less common.