Abstract
Currently, there is no consensus on how growing conditions affect the heartwood formation in Scots pine. Comparing the results obtained by different authors is difficult due to methodology differences and poor descriptions of the objects used. We selected two sample plots in (1) a blueberry pine forest on nutrient-rich and moist soil and (2) a lichen pine forest on nutrient-poor and dry soil and performed their detailed characterization. The sample plots were located 22 km apart in the middle taiga subzone (Karelia Republic, northwest Russia). In each sample plot, we selected five dominant trees (model trees), from which we took cores at different trunk heights (0.3, 1.5, 4.5, 7.5 and 10.5 m). The cores were treated with 2,6-dichlorophenolindophenol to identify the heartwood zone. Additionally, samples were taken to study the structural features of the transition zone between sapwood and heartwood. In both forest types, the number of heartwood rings depended on the cambium age, and the patterns of parenchyma cell death did not differ in the transition zone. These facts point to a predominantly internal regulation of the heartwood formation in Scots pine. The heartwood radius and its proportion on the cross-sections were significantly higher in the blueberry pine forest than in the lichen pine forest, despite the relative values of the annual ring width. Further research is needed to develop successful Scots pine heartwood width models under a wide range of conditions.
Highlights
Scots pine is an economically important species in many European and Asian countries [1]
In trees growing on poor soils, the nutrient content in sapwood can be comparable to that in trees growing on rich soils [21,22]
Different letters indicate a significant difference at p < 0.05
Summary
Scots pine is an economically important species in many European and Asian countries [1]. Scots pine is a eurybiont that grows in a wide range of conditions, from the tundra border in the north to the forest-steppe in the south [23,24] It can form completely different forests — from highly productive oxalis pine forests to sparse dry lichen and waterlogged sphagnum forests [25,26]. Several studies have shown that the heartwood proportion in the trunk in more productive forest types is higher than in less productive stands of Scots pine trees of the same age [42,43]. This article presents the results of the heartwood study in Scots pine trees at the age of 70–80 years, growing in closely located areas in blueberry (Myrtillus) pine forest and lichen (Cladonia) pine forest. A detailed sample plot description, the use of the exact sampling and processing techniques and the same set of measured parameters will allow comparison of the results obtained for different forest types, both within the project framework and in the future
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