Authors: Orumaa, Argo; Tullus, Tea;Tullus, Arvo ;Köster, Kajar;Metslaid, Marek;

Since forest fires frequency is expected to increase, it is important to understand effects of fires to forest ecosystems. We investigated the impacts of forest fire on understorey vegetation that accounts for a large part of the total plant species richness of forest ecosystems. Our research was carried out in northwestern Estonia, where six different stands dominated by Scots pine (Pinus sylvestris L.) were burned 12, 21, 38, 69, 80 and 183 years ago. Effects of time since fire and environmental factors (soil and light variables) on the richness, diversity and cover of vascular plant and bryophyte layers, and on the richness of different species groups were evaluated. Compositional variation was analysed with non-metric multidimensional scaling, Multi-response Permutation Procedures, and Indicator Species Analysis. In vegetation plots, 70 species (31 vascular plant and 39 bryophytes) were found. The cover of the bryophyte and vascular plant layers increased with longer time since fire. There was also compositional differences in the recently burned vs long-time ago burned areas. In conclusion, time since fire impacted compositional patterns of understorey vegetation, although time-related trends in species richness were less evident.