Text by Lauri Laanisto
Author: Taavi Paal
Title: Immigration limitation of forest plants into wooded landscape corridors
Supervisor: Dr Jaan Liira, University of Tartu, Estonia
Dissertation was accepted for the commencement of the degree of Doctor
philosophiae in plant ecology and ecophysiology at the University of Tartu on
March 6, 2017 by the Scientific Council of the Institute of Ecology and Earth
Sciences, University of Tartu.
Opponent: Prof. Lander Baeten, Ghent University, Belgium
Commencement: Council hall of the University of Tartu, 18 Ülikooli Street,
Tartu, on 10 May 2017 at 10.15 a.m.
Full text of the thesis can be found here.
Thesis is based on following publications:
Liira, J. & Paal, T. (2013) Do forest-dwelling plant species disperse along
landscape corridors? Plant Ecology 214:455–470. (link to full text)
Paal, T., Kütt, L., Lõhmus, K. & Liira, J. (2017) Both spatiotemporal
connectivity and habitat quality limit the immigration of forest plants into
wooded corridors. Plant Ecology 218:417–431. (link to full text) (link to blog post)
Lõhmus, K., Paal, T. & Liira, J. (2014) Long-term colonization ecology of
forest-dwelling species in a fragmented rural landscape – dispersal versus
establishment. Ecology and Evolution 4(15):3113–3126. (link to full text)
Paal, T., Zobel, K. & Liira, J. Plant traits indicate that various ecological
filters limit forest species use of wooded green corridors. Manuscript.
Large-scale agricultural and sylvicultural activities have led to the fragmentation and isolation of both ancient and recent forests in landscape. In afforested areas, the formation of forest-specific vegetation is impeded by the inhospitable surrounding agricultural matrix and by poor dispersal ability of many forest plants. Landscape corridors are proposed as a means to increase the connectivity between species source and target habitats, therein wooded corridors should enhance the dispersal of forest-specific species. The aim of this thesis was to evaluate the functionality of wooded landscape corridors as dispersal enhancing landscape elements for forest plants of deciduous forests. The results of this thesis indicate that wooded corridors in their present state do not perform well as dispersal enhancing structures for specialist forest plants. Even in well-connected corridors, most of forest specialists colonised only the first 5–10 m of the corridor, and only very few species could migrate to isolated corridors. Mainly those forest plants are successful that utilise long-distance dispersal vectors, such as mammals or birds, and those that can tolerate habitat edge mediated conditions dominating in corridors. Positive signals of the use of corridors by forest-dwelling plants were mostly created by shade tolerant generalist species. Analysis results showed that forest species can be supported only by wide corridors that are directly connected to ancient (source) forest, and those that have structures reducing edge effects. Such structures are formed in corridors with a double line of mature trees (e.g. old alleys) that have wide-arching canopies and lateral side branches. Landscape planning and conservation management of rural landscapes should target first on existing wooded corridors before planting new tree lines, as the formation of suitable habitat conditions takes decades or centuries.