Pinus heldreichii and Pinus peuce forests of the Pirin Mountains in Bulgaria

We investigated the forest communities of Pinus heldreichii and Pinus peuce in the Pirin Mountains in Bulgaria. Both Pinus species are sensitive relicts with a very limited range, primarily in the Balkan Peninsula. Anthropogenic activities and global climate change pose serious challenges to their conservation. We have subjected 189 published and unpublished relevés from newly conducted field research to numerical analysis. Then we corroborated them by comparison with the previously identified and published syntaxa in neighbouring countries. The results indicated that the Pinus heldreichii communities form part of the Festuco penzesii-Pinetum heldreichii ass. nov. with two subassociations: typicum and seslerietosum coerulantis subass. nov. These communities are distinctly oromediterranean, characterised by their floristic composition and occurrence on marbles. In contrast, we classified the Pinus peuce communities in the Pirin Mts. at the community level as the Festuca valida-Pinus peuce community. These extrazonal boreomontane communities are also distributed at high elevations, but in contrast to the Pinus heldreichii communities, they occur on silicate terrains. Pinus heldreichii associations have a limited range, and due to their canopy openness and occurrence on marbles and serpentine terrains, they support many regional and even local endemics. Although Pinus peuce communities are also divided into geographically isolated groups, the high constancy of characteristic species of boreomontane forests calls this classification into question, suggesting that a comprehensive revision of Pinus peuce forests within their range is needed.