Experimental evidence on biodiversity impacts of variable retention forestry, prescribed burning, and deadwood manipulation in Fennoscandia

Abstract

Intensive forest management has been applied in most Fennoscandian forests for a period of almost one felling rotation. This paradigm has produced even-aged and even-structured forests of different successional stages that cover about 90% of forest land. At the same time, wildfires have been nearly eliminated in most of the Fennoscandian nature. Consequently, hundreds of species are red-listed because of forest management. To support these species, forest management requires improvements. Variable retention forestry and habitat restoration have been suggested to mitigate negative effects of forest management on biodiversity, and these have been practiced to some extent during the past few decades. Here, we review experimental results on the effects of variable retention and two restoration measures (prescribed burning and artificial addition of coarse woody debris) on different species groups in Fennoscandia. Our key findings are as follows: (i) Many species respond positively to felling within a few years, apparently due to released and often ephemeral resources, such as fresh residue and stumps. Species associated with shady conditions are negatively impacted, but any retention supports many of these, and their species composition remains almost unaffected with 50-70% retention of the initial tree volume. (ii) These effects remain detectable for at least 10-30 years or, according to some studies, nearly 100 years, e.g., in polypore fungi. (iii) Initial effects of prescribed burning on most species groups (apart from pyrophiles) are negative, but within 10-15 years post-fire sites begin to support many rare and threatened deadwood-dependent species. Epiphytic lichens, however, remain negatively affected. (iv) Artificial addition of deadwood (mostly high stumps) supports a wide spectrum of deadwood-dependent species, but the species composition differs from that of naturally died trees. (v) Moisture and micro-habitat variation are crucial for forest species at harvested sites, at least in forests dominated by Norway spruce. We conclude that felling method as such is of little importance for threatened forest species, although retention mitigates many negative effects. These species require microclimatic continuity, and maintenance and active increase of legacies, such as deadwood of different qualities (species, downed/standing, snag/log/stump, decay stage), very old trees, and tree species mixtures.

Continuous-cover management and attractiveness of managed Scots pine forests

“…The logging methods include selection cutting, gap cutting and modifications of clear cutting, all characterized by maintaining a significant proportion of trees throughout the logging cycle (e.g., Puettmann et al 2009, Koivula et al 2014. Experimental evidence suggests that even modest retention of living trees in harvested blocks is beneficial for biodiversity (Koivula & Vanha-Majamaa 2020). Also, based on landscape preference research, retention methods may be preferred over clear cutting by citizens who use forests for aesthetic pleasure, recreation, hunting or collecting (Ribe 1989 and references therein).…”

Ecological perspectives on variable retention forestry

“…Finally, they identify several important future research directions for VRF, including a switch of focus towards the landscape as well as the species population level. In the last paper, Koivula and Vanha-Majamaa (2020) review experimental results from 22 replicated experiments on the effects of variable retention and two restoration measures (prescribed burning and artificial addition of coarse woody debris) on different species groups in Fennoscandia. They show that 50-70% retention of the initial tree volume would be necessary to prevent changes in the species composition associated with shady conditions.…”

Sienestystä pohjoisilla puupelloilla: metsien moninaiset taloudet ja plantaasiosentrismin ongelma

“…Tällä hetkellä erityisesti nopeakiertoinen kuitupuun tuotanto ohjaa kiihdyttämään metsien ajallisia rytmejä sekä syrjäyttämään puuntuotannolle merkityksettömiä lajeja tavoilla, joita voi monien ei-inhimillisten eliöiden kannalta pitää väkivaltaisina ja peruuttamattomina häiriöinä (ks. Koivula & Vanha-Majamaa 2020;Säynäjäkangas & Kellokumpu 2020). Häiriöt ilmenevät metsien ikärakenteen ja lajikirjon yksipuolistumisena, metsäautoteiden halkomina elinympäristöinä ja uhanalaistettujen lajien keskittymisenä sirpaleisille luonnonsuojelualueille.…”

“…2020, 2): korvasienet ja marjakasvit käyttävät hakkuiden myötä lisääntyneitä ravinteita, valoa ja lämpöä (ks. Koivula & Vanha-Majamaa 2020), ja keräilijät ottavat talteen näin syntyviä puuntuotannolle tarpeettomia tuotteita ja metsäautoteillä kulkiessaan valjastavat metsäteollisuuden infrastruktuuria uuteen käyttöön. Tässä mielessä keräilyn suhde plantaasitalouksiin on kommensalistinen: puuplantaaseja hyödynnetään keräilyssä ilman, että niille tuotetaan haittaa, tai jopa plantaasituotannon imagolle suotuisasti.…”