Natural gap dynamics in a Central European mixed beech—spruce—fir old-growth forest

Abstract

We provide a study on long-term canopy gap dynamics in the Źofin Virgin Forest (total area 98 ha), which has been strictly protected since 1838. Our aims were i) to describe the size distribution of gaps at a given time; ii) to determine the area where dynamic processes occurred within a given period; and iii) to determine the role of deciduous versus coniferous trees in gap formation. The fate of individual gaps was followed in a 47-ha beech-dominated part of the reserve by analyzing aerial photographs taken in 1971, 1983, 1991, and 2004. The role of individual trees in canopy gap dynamics was studied by combining gap distribution maps with stem position maps of 1975 and 1997 for a 10-ha sample plot. We showed that i) total gap area (9–11%) and average gap size (88–99 m2) was stable during the 33-y study period; ii) canopy dynamics occurred in 0.1% of the area annually; iii) most gaps were created by the simultaneous death of 1–3 canopy trees; iv) death of deciduous trees played a more important role in the creation of gaps than their proportion among dead trees would suggest; and v) tree size and neighbourhood also determined if a dead tree became a gap maker.