Senior Research Fellow Jaan Liira, University of Tartu
Professor John-Arvid Grytnes, PhD, University of Bergen
Forests are among the most-threatened ecosystems in Europe. Severe human impact has reduced forest cover and decreased the habitat quality in remaining stands. Even in Estonia-where forests cover about half of the country-habitat quality is often diminished. Throughout history a large number of rural manor parks have been established across Estonia. The landscape setting and history of these parks make for a unique study system to disentangle the colonisation ecology of forest species. Therefore, the aim of this thesis was to identify factors affecting colonisation ecology of forest-dwelling species and the ecological value of old rural manor parks.
This thesis shows that old rural manor parks can contribute to forest biodiversity. Especially the closed-canopy parts of parks harbour forest specific species and stand characteristics typical to old-growth nemoral forests. Many of these habitat properties are rare in contemporary mature forests. The results also show that forest species are able to colonise forest-like habitats when given enough time, a suitable landscape setting and favourable habitat conditions. At a landscape level this means ensuring the availability of species source habitats and supporting habitat connectivity. A favourable habitat is sufficiently large in size and has limited light conditions suitable for forest species. In addition to the sufficient closure of the tree canopy layer, it is important to have some shading by shrub and lower tree layers. Plant species that were successful in colonising park habitats were adapted to tolerate shade and flowered early in the growing season, but also had a higher requirement for soil nutrient and higher values for a ruderal life strategy.
To support forest specialist species in parks, park management levels needs to be kept moderate or aim at mimicking broad-leaved forest conditions. Therefore it is important to support a diverse stand structure by retaining old or damaged trees and by avoiding early-season mowing.