Retention of trees at final harvest - evaluation of a conservation technique using epiphytic bryophyte and lichen transplants

Some trees are commonly retained as a conservation measure during forest harvest. However, their actual contribution to maintaining biodiversity is poorly known. In Swedish forests, aspen Populus tremula supports a rich epiphytic flora. The bryophyte Antitrichia curtipendula and the lichen Lobaria pulmonaria, used in forest inventories as indicators of long forest continuity and presence of red-listed species, were used in a transplantation experiment. Transplants on groups of retained aspen trees in clearcuts were compared with transplants on scattered trees in clearcuts and on aspens in uncut mature forests. The survival and 'vitality' of a total of 2240 transplants were recorded 20-25 months after transplantation, where 89% of the lichen transplants remained, as compared with 99% for the bryophyte. Both species had high vitality in clearcuts, although the bryophyte was most vital in the forest. The lichen had significantly higher vitality on groups of trees as compared with scattered ones. Vitality was significantly higher on the north than on the south sides of retained trees for both species. The results indicate that retained trees can form biodiversity links during forest succession after final harvest and that they are beneficial to at least some species considered to be sensitive to forest operations. (C) 1999 Elsevier Science Ltd. All rights reserved.