Diversity of lichens and bryophytes in hybrid aspen plantations in Estonia depends on landscape structure

The importance of single-species forest plantations in sustaining biodiversity could be bigger than expected. We described the diversity of lichens and bryophytes in 15 midterm (16- to 17-year-old) hybrid aspen (Populus tremula x Populus tremuloides) plantations in Estonia. Species richness and composition data were linked with environmental and landscape-scale variables. Altogether, 44 lichen and 37 bryophyte species were recorded from plantations; richnesses of bryophytes and lichens were positively correlated. Lichen species composition was significantly affected by landscape-scale parameters (distance to the nearest present forest, distance to the nearest forest continuously occurring in the same place since the 1930s, and forest area in the study plot vicinity in the 1930s). Bryophyte species composition was affected mainly by light conditions and forest area in the 1930s. Among lichens, the sexual crustose species functional group dominated in midterm plantations; appearance of asexual lichens of different growth forms is expected during the next years. Our results indicate the importance of long-term availability of good-quality forests as sources of propagules. Short-rotation hybrid aspen plantations can provide temporary habitats for forest species and thus in part contribute to preserving landscape-scale biodiversity, if they are close to possible colonization sources. Green-tree retention in plantations will probably raise the biodiversity value of those short-term communities.