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A doctoral student from the Netherlands defended her thesis
Today, on December 16, a doctoral student from the Netherlands, Floortje Vodde, defended her doctoral thesis at the Estonian Univeristy of Life Sciences. The title of the thesis is „Microsites and tree regeneration dynamics: prolonged storm effects in hemiboreal mixed forest”. Windstorm, among the main natural disturbance agents in central and northern Europe, is found to have controversial effects on the direction of forest succession. Storm severity explains part of the contradiction, but the composition and distribution of biotic and abiotic storm legacies may also play a role, she explained.
Post-disturbance regeneration performance was evaluated based on a series of field inventories in two mature spruce-broadleaf mixed forests on humid, eutrophic soils in Estonia. Two major storms hit the areas in 2001 and 2002 respectively. Regeneration was investigated in patches with different disturbance severities. The focal species were Norway spruce (Picea abies (L.) Karst.), silver and downy birch (Betula pendula Roth. and B. pubescens Ehrh.), black alder (Alnus glutinosa (L.) J. Gaertn.) and European rowan (Sorbus aucuparia L.).
The research allowed to conclude that pre-disturbance management affects future species composition and stand structure. Salvage logging of wind disturbed areas increases the share of shade-intolerant species. Local post-disturbance retention of coarse woody debris and targeted pre-commercial thinning are tools to promote certain groups of tree species. The presence of storm-induced microsites is expected to increase long-term tree species diversity on the stand level, due to the species’ preferences.
The supervisors of the thesis were Prof. Kalev Jõgiste and Prof. Dr. Ir. G.M.J. Frits Mohren, the opponent was Prof. Dr. Pasi Puttonen (Department of Forest Sciences, University of Helsinki, Finland)
Floortje got both her bachelor’s and master’s degree at the Univeristy of Wageningen, the Netherlands before beginning her doctoral studies at the Estonian University of Life Sciences in 2007. During her studies, she gave birth to two daughters.