PS 25-86
Long-term demographic rates in temperate old-growth forests of Slovenia
In the temperate region of Europe, much of our understanding of late-successional (old-growth) forest dynamics is based on inferences from stand structure or historical reconstructions from dendroecological data. Very few studies have made direct long-term observations of demographic processes, yet such information is critical for understanding stand dynamics. We used data from a three-decade study of permanent plots located in 10 old-growth forest reserves distributed throughout Slovenia to examine long-term rates of mortality and recruitment. The forest reserves are dominated by Fagus sylvatica or mixtures of F. sylvatica and Abies alba. The study includes 19 plots ranging from 0.4–2 ha in size and more than 5000 tagged trees > 5 cm diameter at breast height (dbh). Following their establishment around 1980, some plots were remeasured in the 1990s, and all plots were remeasured between 2010–2013; measurements include dbh, mortality, and type of mortality.
Results/Conclusions
Preliminary results indicate that mortality and recruitment rates varied between species, among forest reserves, and over time. Among the forest reserves included in the preliminary analysis that were not damaged by windthrow, the overall annual mortality rate ranged from 0.7–1.4% for F. sylvatica and 0.5–1.9% for A. alba. In general, mortality rates were highest for the smallest (5–20 cm dbh) and largest (> 70 cm dbh) diameter classes, reaching up to 2.5%/yr for both species, although size-specific mortality rates varied widely among plots, reserves, and census periods. For reserves that had a second remeasurment in the 1990s, the annual mortality rate increased by more than 1% in the recent census period for trees > 70 cm dbh. Two of the reserves were damaged by windstorms, with indiviual events killing about 20% of the trees. Recruitment into the smallest diameter class was low for F. sylvatica (0–3.8%/yr), and completely lacking for A. alba. These results provide the first long-term estimates of demographic rates in temperate old-growth forests of Europe and will provide an important baseline to assess future rates of mortality due to global change.