Tree age distributions in old-growth forest sites in Vienansalo wilderness, eastern Fennoscandia

Abstract

The age and size of trees was sampled and measured on eight sample plots (0.2 ha each) within a Pinus sylvestris -dominated boreal forest landscape in Vienansalo wilderness, Russian Karelia. The fi re history of these plots was obtained from a previous dendrochronological study. All the studied sample plots showed a wide and uneven distribution of tree ages, but the shape of the age distributions of trees as well as tree species composition varied substantially. Trees over 250 years of age occurred in every studied plot, despite its small size. This suggests that old Pinus were common and rather evenly distributed in the landscape matrix. The oldest Pinus tree was 525 years of age. The correlations between tree age and size were often weak or even nil. In Pinus the correlation between age and diameter was stronger than that between age and height. In the dominant tree species Pinus and Picea, the largest trees were not the oldest trees. The tree age distributions together with the fi re history data indicated that the past fi res have not been stand replacing, as many of the older Pinus had survived even several fi res. Tree age classes that had regenerated after the last fi re were most abundant and dominated by Picea and/or deciduous trees, while the trees established before the last fi re were almost exclusively Pinus. The results suggest that periodic occurrence of fi re is important for the maintenance of the Pinus-dominated landscape. This is because fi re kills most Picea and deciduous trees and at the same time enhances conditions for Pinus regeneration, facilitated by available seed from the continuous presence of old fi re-tolerant Pinus trees.

Tree diameter distributions in natural and managed old Pinus sylvestris-dominated forests

“…The fact that these two dbh-distribution patterns were common in natural stands can evidently be related to the occurrence of fire, and the characteristics of postfire succession (Engelmark and Hytteborn, 1999). In Pinus-dominated forests, the largest trees typically survive low-severity fires, which have been common in the Vienansalo area (Lehtonen and Kolström, 2000;Kuuluvainen et al, 2002;Lampainen et al, 2004). Fires are followed by abundant regeneration, thus giving rise to bi-or multimodal dbh-distributions (Kolström and Kellomäki, 1993;Engelmark et al, 1994Engelmark et al, , 1998Kuuluvainen et al, 2002).…”

“…This obviously leads to increased variability in tree sizes, and the development of multimodal, decreasing or irregular tree diameter distributions. This appears to be often the case among the boreal forests of Fennoscandia, where stands with unimodal diameter distributions do not appear to be common in natural conditions (Lähde et al, 1991;Kuuluvainen, 2002;Kuuluvainen et al, 2002).…”

“…In Fennoscandia, for example, low-or moderate-severity fires are common. Such fires kill the smaller trees, while the larger Pinus sylvestris L. trees usually survive, because of their thick heat-insulating bark (Kolström and Kellomäki, 1993;Wirth et al, 1999;Kuuluvainen, 2002;Kuuluvainen et al, 2002;Lampainen et al, 2004). On the other hand, in storms the situation is reversed, as large trees have a higher probability of falling compared to small trees (Brewer and Merritt, 1978;Canham et al, 2001).…”

Dead standing pine trees in a boreal forest landscape in the Kalevala National Park, northern Fennoscandia: amount, population characteristics and spatial pattern

“…However, this requires information on height of the intact tree, which together with tree diameter is then used to determine the stem taper. To obtain intact heights for snapped dead pines, we fitted Näslund's (1936) height curve to an independent DBH-height dataset from the same region, from Kuuluvainen et al (2002), and used this to predict the height of the intact trees (i.e., snapped trees prior to snapping). Volume integrals were then computed, using functions for the R statistical computing environment (R Core Team 2016), by .…”

Bird species dynamics in a managed southern boreal forest in Finland

“…In managed boreal forests, the habitat is changing continuously due to succession and humancaused alteration. Natural succession in boreal forests of Fennoscandia is rather slow, with old-growth forests prevailing (Kuuluvainen et al, 2002;Pennanen, 2002), whereas logging and forest management cause rapid changes in the structure of forest stands and forest landscapes.…”