What are the effects of even-aged and uneven-aged forest management on boreal forest biodiversity in Fennoscandia and European Russia? : A systematic review protocol

This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details. Author(s): Title: Year: Version: Copyright: Rights: Rights url: Please cite the original version: CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ What are the effects of even-aged and uneven-aged forest management on boreal forest biodiversity in Fennoscandia and European Russia? : A systematic review protocol © The Author(s) 2019 Published version Savilaakso, Sini; Häkkilä, Matti; Johansson, Anna; Uusitalo, Anne; Sandgren, Terhi; Mönkkönen, Mikko; Puttonen, Pasi Savilaakso, S., Häkkilä, M., Johansson, A., Uusitalo, A., Sandgren, T., Mönkkönen, M., & Puttonen, P. (2019). What are the effects of even-aged and uneven-aged forest management on boreal forest biodiversity in Fennoscandia and European Russia? : A systematic review protocol. Environmental Evidence, 2019(8), Article 17. https://doi.org/10.1186/s13750-019-0160-8 2019 Savilaaksoetal. Environ Evid (2019) 8:17 https://doi.org/10.1186/s13750-019-0160-8 SYSTEMATIC REVIEW PROTOCOL What are theeffects ofeven-aged anduneven-aged forest management onboreal forest biodiversity inFennoscandia andEuropean Russia? Asystematic review protocol Sini Savilaakso1,3* , Matti Häkkilä2, Anna Johansson1, Anne Uusitalo4, Terhi Sandgren5, Mikko Mönkkönen2 and Pasi Puttonen3 Abstract Background: Biodiversity is vital for human well-being, but is threatened by human actions world-wide. In the boreal zone, harvesting and management of forests on an industrial scale is the most important factor driving habitat change and degradation. Over time different forest management regimes have been implemented but their impact on biodiversity at different spatial and temporal scales has not been systematically reviewed although non-systematic reviews on the topic exist. The aim of this article is to describe a protocol for a systematic review to synthesise and compare the impacts of two different forest management systems on biodiversity at different spatial and temporal scales. The topic for the systematic review arose from the discussions with the Finnish forestry sector and was further defined in a stakeholder workshop. Research questions addressed by the systematic review protocol are: (1) What are the stand-level effects of even-aged and uneven-aged forest management on boreal forest biodiversity in Fennoscandia and European Russia? (2) What is the effect of these same forest management systems on biodiversity at landscape level? Methods: Animal, plant, and fungal diversity is addressed. Bibliographic databases and organizational websites will be searched, and internet search engines will be utilized to find relevant literature. The searches will be conducted in English, Finnish, Swedish, and Russian. Articles will be screened regarding the inclusion and exclusion criteria at title, abstract, and full-text stage. The validity of included studies will be evaluated against appraisal criteria and studies categorized based on their risk of bias. A narrative synthesis will be conducted to describe the findings. If enough quantitative data can be retrieved from the studies, a meta-analysis will be conducted. Keywords: Clear-cut, Continuous cover forestry, Landscape, Species diversity, Species richness © The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/ publi cdoma in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Open Access Environmental Evidence *Correspondence: [email protected] 1 Metsäteho Oy, Vernissakatu 1, 01300 Vantaa, Finland Full list of author information is available at the end of the article Page 2 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 Background In the boreal zone, harvesting and management of forests on an industrial scale is the most important factor driving habitat change and degradation [1]. In addition to regular harvesting, removal of stumps and harvesting residues for energy wood has increased in recent decades because of the current climate policies in Europe [2] but also in North America [3]. Stump removal increases the degree of disturbance by decreasing the amount of dead wood dramatically [4, 5] and may therefore lead to stronger responses of the dead-wood dependent species. There are lots of studies on the impacts of forest harvesting on different species groups in Fennoscandia, and long-term monitoring shows declines of biological communities, for example in many forest bird populations [6, 7]. Also, species assemblages may not be maintained in protected areas if they are embedded in heavily managed landscape [8, 9]. Under these circumstances the management of productive forests is a key aspect for maintaining biodiversity. A common forest management regime in the whole boreal zone has long been even-aged management (Table1) [10]. In Finland, for example, even-aged management was the primary management regime in forestry dictated by law for more than 60years, until the year 2014, when uneven-aged management regime was enabled again [11]. As boreal forests in their natural state are usually heterogenic with trees and stands of different species, ages and size, even-aged management simplifies the forest structure which is noticed to have negative impacts on biodiversity [12]. To slow down the decline of forest species diversity alternative management regimes have been taken into practice. Retention forestry [13] is usually similar to even-aged management, but some old trees, dead or living, or small stands of trees are retained in harvest to create structural diversity [14, 15]. In uneven-aged management, i.e. continuous-cover forestry, harvested patches are usually smaller than in even-aged management, mature trees or tree groups are selected for harvesting, and younger trees are left to grow [10]. Uneven-aged forest management aims for more heterogeneous stand structures, assumed to be less damaging to forest biodiversity than clear-cuts [16]. Even though even-aged management is still the most common harvesting method in Finland, Sweden and Norway, the public interest towards uneven-aged forest management has increased in the last decades [17–21]. In European Russia, most final feellings are clear-cuts and continuous cover forestry with selective logging method is more widely used only in western parts of the country in Murmansk and Leningrad regions [22]. Despite the rising public interest, the adoption of uneven-aged forest management in Finland, Sweden and Norway has been relatively modest. There is a strong, ongoing debate on economic profitability of uneven-aged management, with studies showing that at least in some forest types uneven-aged management would be more profitable than even-aged management [23, 24]. Similarly, recent scientific studies suggest that uneven-aged management provides higher values for some biodiversity aspects but even-aged management for others [10, 25]. Therefore, it is not surprising that there is no strong consensus between stakeholders on the impacts of these two forest management regimes on biodiversity [26]. The topic for the systematic review arose from the discussions with the Finnish forest industry on their evidence needs related to sustainability issues. In Table 1 Definitions ofdifferent forest management regimes.Also, common synonyms forthemain term are given Forest management regime Synonyms Definition Even-aged forest management clear-cutting, clear-felling Management method that produces relatively homogenous forest structures. Forest rotation is controlled by planting, thinning and regeneration felling. During the regeneration felling all the trees in the area are removed. Retention forestry Management method almost similar to even-aged management, but some individual trees (dead or alive) or tree groups are left standing during the regeneration fell. This aims to enhance the structural diversity of the harvesting area. Uneven-aged forest management continuous cover forestry, selective cutting/felling, selection cutting/felling, partial cutting/felling, gap cutting/felling, patch cutting/felling Management method where only some of the trees are removed in one harvest. Forest regenerates through the trees left standing and no plantation is needed. The forest structure stays heterogenous and this can be achieved by cutting single trees (selective felling) or tree groups (gap felling). Page 3 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 Finland 91% of forests are in commercial timber production [27] and hence, forest industry has large influence on forest biodiversity. Specifically, three forestry companies (Metsä Group, Stora Enso Oyj, and UPMKymmene Oyj), industry representative group Finnish Forest Industries, and the state-owned enterprise Metsähallitus, which is responsible for the management of one-third of Finland’s surface area, participated in the discussions that lead to the broad definition of the topic. The topic was further defined in a stakeholder workshop that was held 23 August 2018. Purposive selection based on known contacts, snowballing, and internet search were used to compile a list of stakeholders following recommendations by Haddaway etal. [28]. An open invitation to participate in the workshop was published on the website of the Evidence-Based Forestry in Finland initiative 24 July 2018 and sent by email to 35 stakeholder organisations (Additional file1) with a notice that it can be further shared with interested individuals and organisations. A reminder email was sent 2weeks later to those individuals and organisations that had not responded. In the end, 13 individuals from 12 stakeholder organisations participated in the workshop (Additional file1). At the workshop, the topic, research questions, initial theory of change, PECO-based search terms, and factors creating heterogeneity were presented and discussed. Based on the discussion with the participants the topic was narrowed to the two research questions that are presented in this protocol. The participants also suggested sources of grey literature and potential sources for unpublished data. Comments and suggestions of the participants related to other elements discussed have been integrated into the protocol. Objective ofthereview The objective of the review is to systematically review and synthesise results of the studies on the impacts of even-aged and uneven-aged forest management on biodiversity, specifically species of different taxa, at different spatial and time scales. Figure1 shows a simple theory of change of the impacts of forest harvesting on biodiversity. The review will focus on Fennoscandia (Finland, Sweden and Norway) and European Russia. The geographical scope of the review was discussed at the stakeholder workshop and is based on the similarity of the forests, including tree species, and their management. The review has two key research questions: 1. What are the stand-level effects of even-aged and uneven-aged forest management on boreal forest biodiversity in Fennoscandia and European Russia? 2. What is the effect of forest management on boreal forest biodiversity in Fennoscandia and European Russia at landscape level? The impacts of even-aged and uneven-aged forest management regimes will be compared to each other as well as to forest areas where no intervention has taken place to give a full picture of the impacts. The first question focuses on the impact of different forest management regimes on alpha diversity whereas the second question focuses on gamma diversity. Most of the biodiversity studies are standlevel studies focused on species richness and other alpha diversity measures, which commonly decrease in response to harvesting. However, it is important to know whether the stand-level habitat loss means an overall loss of biodiversity at a larger scale or whether biodiversity is maintained despite a temporary loss of a habitat in one or more places in the landscape that is formed by the different forest stands. The question components are outlined in Table2. Methods This protocol follows the guidelines of Collaboration for Environmental Evidence and complies with the ROSES reporting standards. The ROSES form is included as an Additional file2. Searching forarticles Search string A list of search terms relating to the PECO components was proposed at the stakeholder meeting and validated by the participants (Table3). Fig. 1 Simplified depiction of impact pathways influencing species assemblages over time. Clear-cut is a typical management practice for even-aged forest management whereas uneven-aged forest management retains continuous forest cover. In practice, the dichotomy between even-aged and uneven-aged forest management regimes is less distinct than depicted here due to effect modifiers such as the number of retention trees, gap size, and felling style Page 4 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 Based on the five categories, a search string was formulated using Boolean operators ‘OR’, ‘AND’ and ‘NEAR’. The performance of the search string was tested using a test list of 20 articles collected from previous reviews and from experts (Additional file3). The testing was conducted primarily in the Web of Science (Core Collection) but also included testing in Scopus and CAB Abstracts (Additional file4). After scoping and taking reviewer suggestions into account, the search string was modified into its current form. The final search string in English is: #1 TS = ((Boreal NEAR/5 (forest* OR zone OR tree*)) OR taiga OR spruce* OR picea OR pine* OR pinus OR birch* OR aspen* OR populus). #2 TS = (Finland OR Finnish OR Swed* OR Norw* OR Russia* OR Fennoscan* OR Scandin* OR “north* europ*” OR “nord* countr*”) and TS = (forest* OR tree*). #3 TS = (clear-cut* OR clearcut* OR clearfell* OR clearfell* OR “clear fell*” OR even-aged OR uneven-aged). #4 TS = (forest* NEAR/5(“continu* cover*” OR “natural* regenerat*” OR multiage* OR alternativ* OR “common* sens*” OR unmanaged OR managed OR sustainabl*)). #5 TS = (silvicult* NEAR/5(“continu* cover*” OR “natural* regenerat*” OR multiage* OR alternativ* OR “common* sens*” OR unmanaged OR managed OR sustainabl*)). #6 TS = (Regenerat* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (select* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (partial* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (alternat* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (retent* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (conserv* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (gap* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (patch* NEAR/5 (cut* OR fell* OR harvest* OR log*)) OR TS = (dispers* NEAR/5 (cut* OR fell* OR harvest* OR log*)). #7 TS = (biodiversi* OR fauna OR flora OR fungi OR eukaryot* OR vertebrat* OR invertebrat* OR animal* OR plant* OR arthropod* OR lichen* OR insect* OR bird* OR mammal* OR vegetat* OR bryophyte* OR amphibian* OR reptile*). #8 TS = (species NEAR/5 (divers* OR rich* OR assemb* OR abund*)). #9 #2 OR #1. #10 #6 OR #5 OR #4 OR #3. #11 #8 OR #7. #12 #11 AND #10 AND #9. The search string will be translated to other search languages. It will be simplified by reducing the number of search terms to search organizational websites and to conduct internet searches where the search interface often has more limited capacity regarding search strings. Boolean operators will be used to combine main search terms whenever the search engine allows it. The used search strings will be recorded and published as additional information in the review report. A search alert will be set in bibliographic databases to screen articles that are published before the data synthesis commences. The number of articles retrieved through the search alerts will be reported in the review report. Languages The systematic review will include studies published in English, Finnish, Swedish, and Russian. The selection of languages is based on the geographical scope of the systematic review and limited by the language skills of the review team. Organisational websites will be searched in the primary language the website is published except the websites in Norwegian, which will be searched in English. Table 2 Components ofthereview questions Subject Exposure Comparator Outcomes Boreal forest Even-aged or uneven-aged forest management No intervention; Other forest management Biodiversity indicators, such as species diversity, richness, individual abundance Table 3 Search terms proposed atthestakeholder meeting Forest type (subject) Taxa ofinterest Intervention Comparator Outcomes Boreal, spruce, pine Vegetation, plant, fungi, bird, polypore, insect, beetle, mammal, arthropod Clear-cut, clearcut, clearfell, clearfell, even-aged, uneven-aged, continuous cover, regeneration fell, management Protected area, national park, nature reserve, natural forest, primary forest, selective harvest, retention cut, partial harvest, old-growth, mature Diversity, richness, assemblage, abundance Page 5 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 In addition, if the publications section includes studies published in other of the review languages (e.g. main website language is Swedish but there are also unique publications in English), the search will be conducted in those languages as well. Bibliographic searches The following bibliographic searches will be conducted: • CAB Abstracts (https ://www.cabi.org/); Keyword search from 1973 onwards. • Directory of Open Access Repositories (https ://doaj. org/); ‘Search all’ field will be used with not further limitations. • Digital Dissertations Library of Russian State Library (http://diss.rsl.ru/). • Doria (https ://www.doria .fi/). • Helka—University of Helsinki Catalogue (https :// helka .finna .fi/); All fields will be searched with no further limitations. • Jultika—University of Oulu repository; All fields will be searched with no further limitations. • JYX—Publication archive of the University of Jyväskylä. • Russian Science Citation Index on the Web of Science (https ://clari vate.com/); Topic search, access from 2005 onwards. • Russian Scientific Electronic Library (https ://elibr ary. ru/). • Scopus (https ://www.scopu s.com/home.uri); Title, abstract, and keyword search. • Swedish University Dissertations (http://www.avhan dling ar.se/). • UTUPub—University of Turku repository. • Web of Science Core collection (https ://clari vate. com/); Topic search covering all years within Science Citation Index Expanded (1945-present), Social Sciences Citation Index (1956-present), Arts & Humanities Citation Index (1975-present), Conference Proceedings Citation Index-Science (1990-present), Conference Proceedings Citation Index-Social Science & Humanities (1990-present), Emerging Sources Citation Index (2015-present). Search engines • Google Scholar (https ://schol ar.googl e.com/); Title search will be conducted with the function ‘at least one of the words’. • Google (https ://www.googl e.com/). The internet searches will be conducted in ‘private’ mode to prevent the influence of previous browsing history and location on search results. The results will be organised by relevance. After the first 50 hits, results will be checked until relevant articles are no longer retrieved as advised in Livoreil etal. [29]. The date and number of hits received and searched will be recorded and included in the review report. Organisational websites The websites of the specialist organisations listed below will be searched. The Russian websites will be searched manually due to the low performance of the “search” function to find relevant hits based on scoping of the organisational websites. If the organisation is publishing a journal, the site of the journal will also be searched if the journal is not already included in some of the bibliographic databases searched. • All-Russian Research Institute of Silviculture and Mechanization of Forestry (http://www.vniil m.ru) • Bellona Foundation (http://bello na.ru/) • BiodivERsA—the network programming and funding research on biodiversity and ecosystem services across European countries and territories (https :// www.biodi versa .org/) • Biodiversity Conservation (Russia) (http://www.biodi versi ty.ru/) • Centre for Economic Development, Transport and the Environment (Finland) (https ://www.ely-kesku s.fi/) • Community Research and Development Information Service (https ://cordi s.europ a.eu/home_en.html) • Confederation of European Forest Owners (http:// www.cepf-eu.org/) • Convention on Biological Diversity (https ://www. cbd.int/) • European Forest Insititute (https ://www.efi.int/) • Federal Forestry Agency (Russia) (http://rosle shoz. gov.ru/) • Federal State Budget Education Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov (http://vgltu .ru/) • Finnish Association for Nature Conservation (https ://www.sll.fi/) • Finnish Environment Insititute (http://www.syke.fi/) • Finnish Forest Association (https ://smy.fi/) • Finnish Forest Centre (https ://www.metsa kesku s.fi/) • Finnish Forest Foundation (http://www.metsa saati o.fi/) Page 6 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 • Finnish Nature League—Luonto-Liitto (http://www. luont oliit to.fi/) • Finnish Society of Forest Science (http://www.metsa tiete ellin enseu ra.fi/) • Food and Agriculture Organization of the United Nations (http://www.fao.org/home/en/) • Forestry Research Institute of Sweden (https ://www. skogf orsk.se/) • Foundation for Strategic Environmental Research (Sweden) (https ://www.mistr a.org/) • Greenpeace Finland (http://www.green peace .org/ finla nd/fi/) • Greenpeace International (https ://www.green peace .org/inter natio nal/) • Greenpeace Russia (https ://www.green peace .org/ russi a/ru/) • Greenpeace Sweden (http://www.green peace .org/ swede n/se/) • International Boreal Forest Research Association (http://ibfra .org/). • International Union for Conservation of Nature (https ://www.iucn.org/) • International Union of Forest Research Organizations (https ://www.iufro .org/) • IVL Swedish Environmental Research Institute (https ://www.ivl.se/). • Metsähallitus (http://www.metsa .fi/) • Metsäteho (http://www.metsa teho.fi/) • Ministry of Agriculture and Food (Norway) (https :// www.regje ringe n.no/no/dep/lmd/id627 /) • Ministry of Agriculture and Forestry (Finland) (https ://mmm.fi) • Ministry of the Environment (Finland) (http://www. ym.fi) • Ministry of the Environment and energy (Sweden) (https ://www.reger ingen .se/sveri ges-reger ing/miljo – och-energ idepa rteme ntet/) • Ministry of Natural Resources and Environment of the Russian Federation (http://www.mnr.gov.ru/) • Natural Resources Institute Finland (https ://www. luke.fi/) • NOLTFOX—Northern European Database for LongTerm Forest Experiments (http://noltf ox.metla .fi/) • Northern Research Institute of Forestry (http://www. sevni ilh-arh.ru) • Norwegian Forest Research Institute (http://www. skogf orsk.no/) • Norwegian Institute of Bioeconomy Research (NIBIO) (https ://www.nibio .no/) • Norwegian Institute for Nature Research (https :// www.nina.no/) • Norwegian Society for the Conservation of Nature, Friends of the Earth Norway (https ://natur vernf orbun det.no/) • Norwegian State Forest and Land Corporation (https ://www.stats kog.no/) • Regional Public Nature Conservation Organization of Karelia (Russia) (http://spok-karel ia.ru/) • Research institute of Sweden (https ://www.ri.se/) • Royal Swedish Academy of Agriculture and Forestry (http://www.ksla.se/) • Russian Academy of Sciences (http://www.ras.ru/) • Centre for Forest Ecology and Productivity (http:// cepl.rssi.ru/) • Forest Research Institute of Karelian Research Centre (http://fores try.krc.karel ia.ru/) • Ural Branch, Institute of Biology of Komi Scientific Centre, Department of Forest Science (https ://ib.komis c.ru/rus/) • Russian Center for the Protection of Forests (http:// rcfh.ru/) • Russian Institute of Continuous Education in Forestry (http://vipkl h.ru/) • Saint-Petersburg Forestry Research Institute (http:// spb-niilh .ru/) • Saint-Petersburg State Forest Technical University (http://spbft u.ru/) • SNS Nordic Forest Research (http://nordi cfore stres earch .org/) • Skydda Skogen (http://skydd askog en.se/sv/) • Stockholm Environment Institute (https ://www.sei. org/) • Swedish environmental protection agency (http:// www.natur vards verke t.se/) • Swedish Forest Agency (https ://www.skogs styre lsen. se/) • Swedish Forest Society (https ://www.skogs salls kapet .se/) • Swedish Forestry Association (https ://www.skoge n.se/) • Swedish Research Council Formas (http://www. forma s.se/) • Swedish Society for Nature Conservation (https :// www.natur skydd sfore ninge n.se/) • Tapio (http://tapio .fi/) • United Nations Forum on Forests (http://www. un.org/esa/fores ts/) • WWF Finland (https ://wwf.fi/) • WWF Global (http://wwf.panda .org/) • WWF Russia (https ://wwf.ru/) • WWF Sweden (http://www.wwf.se/) Page 7 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 Supplementary searches Citation chasing will be undertaken to supplement the search. A call for unpublished data will be published on the website of the Evidence-Based Forestry in Finland project (http://npmet sa.fi/en/front page/) and sent directly to stakeholder organisations that may have unpublished data on the topic. Also, data will be asked from individuals suggested at the stakeholder workshop. Search record database The search results will be exported into separate files using a reference management software. If the document cannot be exported into a reference management software, a record will be created manually into a separate file. Once all the searches have been conducted, the reference files will be merged, and duplicates will be removed before commencing article screening. Article screening andstudy eligibility criteria Screening process Articles will be screened by three people at the title, abstract, and full text level. At the title stage, a random set of 100 articles will be independently screened by all three screeners. If their screening decisions are in agreement, i.e. they would include/exclude the same articles, rest of the articles will be divided among the screeners. If their screening decisions differ, discrepancies in inclusion decisions are discussed to facilitate consistency before another 100 articles will be independently screened. The process will be repeated until 95 to 100% screener agreement is achieved. The process will be repeated at the abstract stage with a random set of 50 articles. If a screener is unsure whether to include an article, it will be moved to the next stage. Articles at the full text stage will be screened by all three screeners except for studies in Russian that will be screened by only one person at all stages. To check that inclusion criteria is used consistently, the Russian speaker will talk the other screeners through the decision process on a random set of 20 articles at each of the screening stages. The review may include articles published by the authors of the review. Their inclusion in the review at the screening and critical appraisal stage will be jointly determined by the other authors in accordance with the eligibility and appraisal criteria. Eligibility criteria The eligibility criteria are based on the PECO components, study design and geographical location of the studies (Tables4 and 5). Only studies conducted in Finland, Sweden, Norway and European Russia will be included. At each stage of the screening a separate file will be created of the excluded articles. At the full text stage, a reason for exclusion will be recorded, and a list of the excluded articles with the reason for rejection will be included as additional information in the review report. If there are multiple articles from one study site (i.e. linked articles), they will be appraised as a group to avoid inclusion of duplicate data following Frampton etal. [30]. True duplicate studies will be removed, and the rest will be screened as a single unit to consider all available data pertinent to the study when making eligibility decisions. Study validity assessment All studies included in the full text stage will be critically appraised and categorized as ‘low’, ‘medium’ or ‘high’ risk of bias. The assessment is based on the following factors (Table6): Table 4 The eligibility criteria for article screening forthestudy question 1 Question elements Eligibility criteria Population Included: Boreal forests in Fennoscandia and European Russia Exposure Included: Even-aged and uneven-aged management Comparators Included: Different forest management regimes, including retention forestry, and areas with no intervention, including protected forest areas, national parks Excluded: Non-forest lands, e.g. agricultural areas, parks in urban areas, wooded fields, e.g. christmas tree plantations Outcomes Included: Species richness, species diversity, abundance Excluded: Community composition indices Study design Included: Before-after (BA), control-intervention studies (CI), and studies combining both (BACI). Also, randomized controlled trials (RCT). Table 5 The eligibility criteria for article screening forthestudy question 2 Question elements Eligibility criteria Population Included: Boreal forests in Fennoscandia and European Russia Exposure Included: Even-aged and uneven-aged management Comparators Included: Forest areas with no intervention, including, protected forest areas, mature production forest, national parks Outcomes Included: Species richness and abundance Study design Included: Before-after (BA), control-intervention studies (CI), and studies combining both (BACI). Also, randomized controlled trials (RCT). Page 8 of 10 Savilaaksoetal. Environ Evid (2019) 8:17 • Study design. • Sampling. • Accounting for potential effect modifiers and heterogeneity. • Data analysis methods. Studies that fulfil any one of the criteria in the category ‘high’ will be excluded. Also, studies with insufficient methodological description will be excluded if sufficient clarifying details are not received by contacting the author of the study. All the studies will be assessed by two persons, and any inconsistencies or uncertainties discussed with other research group members. Data coding andextraction strategy Data from included studies will be extracted and recorded in an Excel spreadsheet (Additional file5) and will be made available as supplementary information of the systematic review. Data will include study meta-data (study characteristics) and data on outcomes, e.g. sample size, mean, standard deviation (SD), and standard error (SE) (see Additional file5 for a full list). Data on test statistics that can be converted into effect size metrics will be collected in case data on outcome mean, SD or SE is not available. Also, data on effect modifiers and potential sources of heterogeneity will be extracted to enable statistical exploration of the relationship between outcomes and sources of heterogeneity at the data analysis stage. All the extracted data will be published as supplementary information of the review. If an article contains independent results from more than one study, these will be treated as separate studies in data extraction. Authors of the studies will be contacted to retrieve any missing information or data. Data will be extracted by more than one person. Hence, a set of five studies will be coded together to ensure consistency. If there are conflicting decisions on what data to extract, the decisions will be discussed among the group. Also, any uncertainties regarding data extraction will be discussed among the group. Data from the studies in Russian will be extracted by one person only. The person will discuss any uncertain decisions with the research group members. Potential effect modifiers andreasons forheterogeneity To understand possible variation in the effects of studies better, possible effect modifiers will be extracted from the studies. As the studies included in this systematic review may have been completed in a relatively large area, there are several factors that may cause heterogeneity among studies, such as climatic conditions and geographic location of the study site. Also, temporal variation is expected. The year a study was conducted may influence the results as forest management has changed over the years. Also, time passed since intervention was started may cause variation depending on the timing and nature of harvests as well as natural succession of vegetation after harvests. Energy wood harvesting, i.e. removing stumps and branches beyond regular harvesting may have various impacts on biodiversity mainly by reducing the amount of dead wood [2, 31]. Habitat connectivity can be an important factor in the dispersal of species across the landscape, and there are several estimates that can be used to quantify connectivity. In case the used connectivity estimates differ between the included studies, we will instead use categories low, medium or high in the data analysis. Below is a non-comprehensive list of potential effect modifiers and sources of heterogeneity. Additional effect modifiers and sources of heterogeneity may be identified from the studies included in the review. The list was Table 6 Critical appraisal criteria toassess studies inthefull text stage Factor Low Medium High Study design Experimental studies (includes also quasi-experimental studies) Observational studies Case studies Sampling Large sample size Sampling method suitable for the population of interest Properly conducted randomisation of study areas Random sampling of study subjects Control and intervention areas matched Small to medium sample size Sampling method suitable for the population of interest Control and intervention areas comparable based on their ecological characteristics Sampling method not suitable for collecting data on the population of interest Accounting for heterogeneity and potential effect modifiers Effect modifiers identified, and data collected on them Effect modifiers identified and considered in relation to the results Effect modifiers not identified or considered Data analysis methods Methods appropriate Methods appropriate Methods not appropriate