Population characteristics of old forest associated epiphytic lichens in Picea abies plantations in the boreal rainforest of Central Norway

Abstract

The boreal rainforest in Central Norway is rich in rare and (or) red-listed epiphytic lichens but is subject to forest harvesting. Natural old Picea abies (L.) H. Karst. forests have been replaced increasingly by dense, even-aged plantations. This study aims at increasing our knowledge about populations of old forest associated lichens in P. abies plantations. In differently aged plantations, we measured occurrence of six lichen species and the population size and reproductive effort of five lichen species. We found that the success of colonizing plantations differed because of species-specific constraints and needs, and that species occurrence depended on stand age and branch quality. A high number of reproducing thalli and small juvenile thalli of the cyanolichen Lobaria scrobiculata (Scop.) DC. and the pendulous lichen Ramalina thrausta (Ach.) Nyl. suggest effective recruitment within plantations. The populations of the cyanolichens Lobaria pulmonaria (L.) Hoffm. and Pseudocyphellaria crocata (L.) Vain. were too small to be viable and demand special concern to survive in managed forests. The abundance of old forest associated lichens in a managed boreal rainforest could be promoted by a varied and heterogeneous branch structure, increased rotation periods (increase the value of plantations as propagule sources), small clearcuts and retention trees (shorten the distance between sources of propagules and target substrate), and maintaining Salix and Sorbus trees (important host trees for cyanolichens and thereby important dispersal sources).