Tree retention as a conservation measure in clear-cut forests of northern Europe: a review of ecological consequences

Figures & data

Table I. Legislation and certification regulations relating to tree retention in Finland, Norway and Sweden.

Legislation
Finland	No special requirements for retention trees. Forestry Act lists seven key habitats (mostly <1 ha) where main habitat characteristics must remain; Nature Conservation Act regulates some additional key habitats, including large, solitary trees.
Norway	Leave at least five retention trees per hectare, preferably in groups. Key habitats must be safeguarded. The ecological function of transition zones along waterways, and between forest and other land, must be ensured.
Sweden	Older trees must be left standing on felling sites, preferably in groups. Protective buffer zones must be left adjacent to water, etc. No logging on non-productive forest land. Avoid damaging sensitive habitats and sites with rich flora and fauna.
Certification FSC
Finland	FSC Working Group in place and a national standard approved with conditions. Only very little (10,000 ha) FSC-certified forest (2008). (www.finland.fsc.org)
Norway	No Norwegian FSC Standard yet (in process), but one group certification unit (71,500 ha) with provisional arrangements^a (B. M. Eidahl, personal communication). Retention levels follow the Living Forest Standard (see below, under PEFC Norway).
Sweden	10 million ha certified (45% of productive forest land).^a Retain all snags, windthrows and other trees that have been dead for more than a year plus all such dead wood originating from high biodiversity trees that have been dead for less than a year. Retain retention trees in a way that they will amount to at least 10 old, large, live trees in the next forest generation; prioritize high biodiversity value trees. Create at least three high stumps or girdled trees per hectare. Retain care-demanding patches, edge zones, groups of trees and biodiversity value trees. (www.fsc-sweden.org)
Certification PEFC
Finland	21.9 million ha is certified (at the end of 2008, mainly group certification) out of 23 million ha. Based on the national Finnish Forest Certification System (FFCS). Leave snags, windfalls and at least five retention trees (minimum 10 cm dbh) per hectare, including trees with high biodiversity value. Leave buffer zone along water, at least 3–5 m (careful logging allowed). (www.pefc.fi)
Norway	7.5 million ha certified (mainly group certification) (www.pefcnorge.org) out of 7.4 million ha productive forest land (12 million ha forested land in total). Based on the national Living Forest Standard (Living Forest 2007), combined with ISO 14001 or EMAS: Leave on average 10 retention trees per hectare (minimum 20 cm dbh), including trees with high biodiversity value. If risk of windthrows, high stumps of spruce and aspen may be created and counted. Leave standing dead deciduous trees, large dead pines and natural high stumps of all tree species. Leave downed coarse woody debris older than 5 years.
Sweden	8 million ha certified (37% of productive forestland).^a Should be set aside: live conservation trees (deviating, old, large-diameter, deciduous trees, hollow trees, etc.) in a way that they amount to 10 retention trees per hectare, some created high stumps per hectare, some representative logs per hectare, retention patches, and protective zones to sensitive habitats. (www-pefc.se)
Monitoring
Finland	National Forest Inventory surveys a network of permanent plots every ~10 years, focusing on economically valuable timber. Dead wood and woodland key habitats are included in the recent surveys, but retention trees are not separated. Forest enterprises, Metsähallitus (administrator of the public land) and private forest owners association monitor a sample of clear-cuts annually. Notes on retention trees and other environmental issues are taken. Unprocessed raw data are not usually available.
Norway	The Norwegian National Forest Inventory survey parameters related to productivity and environmental concern on 12,700 permanent plots on a 5-year rotation basis, including occurrence of certain habitats important for biodiversity, retention trees and retention in the form of riparian buffer zones. In addition, the Norwegian Agricultural Authority (SLF) is responsible for an annual county-wise survey of regeneration and environment (retention trees, riparian buffer zones) on a number of randomly selected clear-cuts.
Sweden	The Swedish Forest Agency in its monitoring programme Polytax surveys a number of randomly selected clear-cuts each year regarding compliance with the law regarding environmental concern, including tree retention. This is done qualitatively as well as quantitatively.
Note: FSC=Forest Stewardship Council; PEFC=Programme for the Endorsement of Forest Certification; dbh=diameter at breast height.
^a Several properties are certified according to FSC and PEFC, i.e. it is not possible to sum area information from FSC and PEFC.

Table II. Studies on different types of tree retention and organism groups in Finland, Norway and Sweden: studies on cost-efficiency, riparian buffer zones (biodiversity aspects) and ecosystem function are also listed, although they were less emphasized in the review.

	Natural high stumps/logs	Created high stumps/logs	Single live trees	Retention groups
Structures	Ranius & Kindvall (2004), Ekbom et al. (2006)	Ranius & Kindvall (2004), Schroeder et al. (2006)		Esseen (1994), Hautala et al. (2004), Hautala & Vanha-Majamaa (2006), Jönsson et al. (2007)
Beetles and other invertebrates	Kaila et al. (1997), Martikainen (2001), Sippola et al. (2002), Sverdrup-Thygeson & Ims (2002), Brunet & Isacsson (2009a, b)	Jonsell & Weslien, (2003), Jonsell et al. (2004, 2005), Lindhe & Lindelöw (2004), Lindhe et al. (2005), Wikars et al. (2005), Abrahamsson & Lindbladh (2006), Gibb et al. (2006), Johansson et al. (2006), Schroeder et al. (2006), Hedgren, (2007), Hjältén et al. (2007), Lindbladh et al. (2007), Abrahamsson et al. (2008), Fossestøl & Sverdrup-Thygeson (2009), Sverdrup-Thygeson & Birkemoe (2009)	Sverdrup-Thygeson & Birkemoe (2009)	Siira-Pietikäinen et al. (2001, 2003), Koivula (2002), Hyvärinen et al. (2005, 2006), Pitkänen et al. (2005, 2008), Martikainen et al. (2006a), Matveinen-Huju et al. (2006, 2009), McGeoch et al. (2007), Djupström et al. (2008), Siira-Pietikäinen & Haimi (2009)
Birds				Söderström (2009)
Bryophytes			Hazell & Gustafsson (1999)	Jalonen & Vanha-Majamaa (2001), Vanha-Majamaa & Jalonen (2001), Perhans et al. (2007, 2009)
Lichens			Hazell & Gustafsson, (1999), Hedenås & Ericson (2003), Hedenås et al. (2007), Hedenås & Hedström (2007), Elfving & Jakobsson (2006)	Perhans et al. (2007, 2009)
Macrofungi	Junninen et al. (2007)	Lindhe et al. (2004)
Vascular plants			Jakobsson & Elfving (2004), Elfving & Jakobsson (2006)	Jalonen & Vanha-Majamaa (2001), Vanha-Majamaa & Jalonen (2001)
Cost-efficiency	Ranius et al. (2005), Jonsson et al. (2006, 2010)), Wikberg et al. (2009)
Riparian buffer zones	Hylander et al. (2002, 2004, 2005), Mönkkönen & Mutanen (2003), Hågvar et al. (2004), Hylander (2005), Hylander & Dynesius (2006)
Ecosystem function	Jacks & Norrström (2004), Jakobsson & Elfving (2004), Lauren et al. (2005), Pitkänen et al. (2005, 2008), Elfving & Jakobsson (2006), Martikainen et al (2006b), den Herder et al. (2009), Löfgren et al. (2009)

Figure 1.  Publications in peer-reviewed journals on biodiversity related to tree retention, in Finland, Norway and Sweden.

Figure 2.  A retention patch, Norway. (Photographer: Anne Sverdrup-Thygeson.)

Figure 3.  An artificial (left) and a natural (right) high stump. Sweden. (Photographer: Lena Gustafsson.)

Ranius , T. and Kindvall , O. 2004 . Modelling the amount of coarse woody debris produced by the new biodiversity-oriented silvicultural practices in Sweden . Biological Conservation , 119 : 51 – 59 .

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Schroeder , L. M. , Ranius , T. , Ekbom , B. and Larsson , S. 2006 . Recruitment of saproxylic beetles in high stumps created for maintaining biodiversity in a boreal forest landscape . Canadian Journal of Forest Research , 36 : 2168 – 2178 .

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Hautala , H. , Jalonen , J. , Laaka-Lindberg , S. and Vanha-Majamaa , I. 2004 . Impacts of retention felling on coarse woody debris (CWD) in mature boreal spruce forests in Finland . Biodiversity and Conservation , 13 : 1541 – 1554 .

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Brunet , J. and Isacsson , G. 2009a . Influence of snag characteristics on saproxylic beetle assemblages in a south Swedish beech forest . Journal of Insect Conservation , 13 : 515 – 528 .

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Brunet , J. and Isacsson , G. 2009b . Restoration of beech forest for saproxylic beetles—Effects of habitat fragmentation and substrate density on species diversity and distribution . Biodiversity and Conservation , 18 : 2387 – 2404 .

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Jonsell , M. , Schroeder , M. and Weslien , J. 2005 . Saproxylic beetles in high stumps of spruce: Fungal flora important for determining the species composition . Scandinavian Journal of Forest Research , 20 : 54 – 62 .

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Abrahamsson , M. and Lindbladh , M. 2006 . A comparison of saproxylic beetle occurrence between man-made high- and low-stumps of spruce (Picea abies) . Forest Ecology and Management , 226 : 230 – 237 .

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Pitkänen , A. , Törmänen , K. , Kouki , J. , Järvinen , E. and Viiri , H. 2005 . Effects of green tree retention, prescribed burning and soil treatment on pine weevil (Hylobius abietis and Hylobius pinastri) damage to planted Scots pine seedlings . Agricultural and Forest Entomology , 7 : 1 – 12 .

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