Abstract
BackgroundAfter their death, Scots pine trees can remain standing for decades and sometimes up to 200 years, forming long-lasting and ecologically important structures in boreal forest landscapes. Standing dead pines decay very slowly and with time develop into ‘kelo’ trees, which are characterized by hard wood with silvery-colored appearance. These kelo trees represent an ecologically important, long lasting and visually striking element of the structure of natural pine-dominated forests in boreal Fennoscandia that is nowadays virtually absent from managed forest landscapes.MethodsWe examined and mapped the amount, structural features, site characteristics and spatial distribution of dead standing pine trees over a ten hectare area in an unmanaged boreal forest landscape in the Kalevala National Park in Russian Viena Karelia.ResultsThe mean basal area of dead standing pine trees in the forested part of the landscape was 1.7 m2∙ha−1 and the estimated volume 12.7 m3∙ha−1. From the total number of standing dead pine trees 65% were kelo trees, with a basal area of 1.1 m2∙ha−1 and volume of 8.0 m3∙ha−1, the remainder consisting of standing dead pines along the continuum between a recently dead tree and a kelo tree. Overall, standing dead pines were distributed throughout the study area, but there was a tendency towards spatial clustering up to <100 m distances. Standing dead pines were most commonly situated on flat ground or in the mid slope in the local topography. In addition, standing dead pines contributed to substrate diversity also by commonly having charred wood and broken tops. Based on the presence of dead pine snags in different stage of transition from a recently dead pine to a kelo with silvery surface, it seems evident that the process of kelo recruitment was continuously in action in the studied landscape.ConclusionsKelo trees are an omnipresent feature in natural pine-dominated forest landscapes with important contribution to forest structural and substrate diversity. Because of their longevity and extremely slow turnover dynamics and importance for biodiversity, protection of vulnerable kelo tree populations, and ensuring their continuous recruitment, should be of high priority in forest restoration and sustainable management.
Highlights
After their death, Scots pine trees can remain standing for decades and sometimes up to 200 years, forming long-lasting and ecologically important structures in boreal forest landscapes
In the Fennoscandian boreal forest, it is not uncommon for pines to live for 400–500 years or more (e.g., Leikola 1969; Zackrisson 1977; Engelmark et al 1994), and following their death, it may take decades for the standing dead pines to develop the characteristic appearance of a kelo tree (Leikola 1969)
We examined whether the occurrence of kelo trees can be explained by environmental factors such as local topography and tree density, and amount of stumps from past selective logging; the area has been the source of construction wood for a small nearby village that has been inhabited since the sixteenth century
Summary
Scots pine trees can remain standing for decades and sometimes up to 200 years, forming long-lasting and ecologically important structures in boreal forest landscapes. Standing dead pines decay very slowly and with time develop into ‘kelo’ trees, which are characterized by hard wood with silvery-colored appearance. These kelo trees represent an ecologically important, long lasting and visually striking element of the structure of natural pine-dominated forests in boreal Fennoscandia that is nowadays virtually absent from managed forest landscapes. In boreal Fennoscandia, large dead-standing silvery-colored Scots pine trees are called kelo trees or kelos (Niemelä et al 2002) They are an omnipresent and visually spectacular feature of the structure of pristine pine-dominated forests (Fig. 1; Keto-Tokoi and Kuuluvainen 2014). When the kelo trees eventually fall over they become another special type of habitat structure for different species (Niemelä et al 2002)
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