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Table 1 Types and levels of retention with examples of types of key biotopes and key elements retained in the harvesting areas in NW Russian forests

From: Variable retention forestry in European boreal forests in Russia

Type of retention; amount or size General characteristics and purpose Time period
Uncut patches; 0.001–30 ha Mainly deciduous and low-diameter or decaying coniferous trees on paludified or unreachable sites with a high amount of CWD.
“No economic value”
Since the 1910s
Seed trees; 20–25 trees per ha in groups of 3–5 trees Mainly pine and spruce, left to ensure natural regeneration Since the 1930s
Understory, low-diameter trees; all possible viable seedlings Left to ensure natural regeneration and reach the target stocking level Since the 1930s
Coarse woody debris Snags and logs of different sizes, tree species, and decay classes.
“No economic value”
Since the 1930s
Key biotopes; the whole forest patch is completely preserved; ca. 0.1–100 ha Paludified patches; ecotones between peatlands and forests; forest “islands” in peatlands; forest patches on rocky sites or steep slopes, cliffs, and canyons; spruce-black alder and paludified spruce forests, pine forests of herb-sphagnum type; patches with uneven-aged structure and old trees; habitats of red-listed species of different taxonomic groups; places of capercaillie mating call Since 1978, with more types added afterwards
Buffer zones around key biotopes or elements, 20–50 m; buffer zones around trees with big nests, 300–500 m Buffer zones around ecotones between peatlands and forests; forest buffers around small water bodies; forests on steep slopes and cliffs and canyons; zones around badger and fox burrows; zones around trees with bird nests; forests around boulders of more than 6 m Since 2000
Key elements; completely preserved Trees of regionally rare species; red-listed tree species; old and decaying trees; snags; high stumps from naturally broken trees; trees with nests and hollows; uprooted trees; logs of different decay classes Since 2000
  1. Adopted from Romanyuk et al. (2001); Pautov et al. (2007); Raj et al. (2008); Andersson et al. (2009a); Yanitskaya (2010); Nikonov and Smirnov (2012); Markovsky and Iljina (2014); Methodological (2017); Moshnikov et al. (2019)