Substantial spatial heterogeneity in growing season dynamics across northern environments

Substantial spatial heterogeneity in growing season dynamics across northern environments | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Substantial spatial heterogeneity in growing season dynamics across northern environments Mika Rantanen, Pekka Niittynen, Matti Kämäräinen, Julia Kemppinen, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8955565/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Arctic tundra and boreal forest landscapes exhibit substantial microclimatic temperature variability, driven by strong topographic gradients, heterogeneous snowmelt patterns, and contrasting vegetation structures. However, this fine-scale variability is often poorly represented in reanalyses, climate models, and conventional weather station networks. In this study, we use a total of 347 microclimate loggers deployed across three regions in northern Fennoscandia during 2020–2024 to examine how the onset, end, duration, and degree days of the growing season vary across the landscapes. Our results show pronounced spatial variation in the onset of the growing season, particularly in the tundra environments, where the earliest and latest onsets differed by up to 40 days within the same season. In contrast, the end of the growing season often occurred abruptly at the three regions, likely driven by changes in large-scale weather conditions. Consequently, the spatial variability in growing season length was primarily driven by differences in its onset. Growing degree sums also varied markedly within areas, with differences of about 400°C days between the warmest and coldest places. The exceptionally warm summer of 2024 corresponded to conditions normally experienced several hundred kilometres further south, highlighting the unprecedented nature of this anomalous summer in northern ecosystems. The findings of this study demonstrate the value of dense microclimate observation networks that advance the understanding of microclimatic processes at ecological scales in cold ecosystems. growing season growing degree days microclimate northern Fennoscandia Full Text Additional Declarations No competing interests reported. Supplementary Files supplementarymaterialrantanen2026TAC.pdf Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 11 May, 2026 Reviewers agreed at journal 28 Mar, 2026 Reviewers agreed at journal 27 Mar, 2026 Reviewers invited by journal 27 Mar, 2026 Editor assigned by journal 25 Feb, 2026 Submission checks completed at journal 25 Feb, 2026 First submitted to journal 24 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8955565","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":613786399,"identity":"3e592b03-3303-4125-ac53-f123135a0e00","order_by":0,"name":"Mika Rantanen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYDACZjZkXoUcAxsD44MDRGnhAZNnjIFamA3wa2FA1sLYZgwyxQCvBt12tsQPjHvs8uzZzx58XDjPIJqPgZkRry1mh9kOSzA8Sy7m4clLNp65zSC3jYGZgYAW9gYJhgPMiT0MOWbSvNv+ALXwHyCkpfkHw4H6xB7+N+a/eecQZQvbMaAthxN7JHLMmHkbiNOSZpFw4Hhiz403xtI8x4BamAlpOX/M+MaHA9WJ7f05hp95agxy57c3M3/ApwUMElB4zATVj4JRMApGwSggBADfQ0Rh99LhUAAAAABJRU5ErkJggg==","orcid":"","institution":"Finnish Meteorological Institute","correspondingAuthor":true,"prefix":"","firstName":"Mika","middleName":"","lastName":"Rantanen","suffix":""},{"id":613786400,"identity":"23faa8e2-9ac7-4bda-8941-a18fbffc84cb","order_by":1,"name":"Pekka Niittynen","email":"","orcid":"","institution":"University of Oulu","correspondingAuthor":false,"prefix":"","firstName":"Pekka","middleName":"","lastName":"Niittynen","suffix":""},{"id":613786401,"identity":"22bd126b-446d-42e8-80f4-108133e00dc7","order_by":2,"name":"Matti Kämäräinen","email":"","orcid":"","institution":"Finnish Meteorological Institute","correspondingAuthor":false,"prefix":"","firstName":"Matti","middleName":"","lastName":"Kämäräinen","suffix":""},{"id":613786403,"identity":"5687a2ee-f14a-4952-8379-cd283542ebc9","order_by":3,"name":"Julia Kemppinen","email":"","orcid":"","institution":"University of Helsinki","correspondingAuthor":false,"prefix":"","firstName":"Julia","middleName":"","lastName":"Kemppinen","suffix":""},{"id":613786404,"identity":"6af5c9ab-bd97-49b4-a426-c9dfad2538a7","order_by":4,"name":"Tuuli Rissanen","email":"","orcid":"","institution":"University of Helsinki","correspondingAuthor":false,"prefix":"","firstName":"Tuuli","middleName":"","lastName":"Rissanen","suffix":""},{"id":613786405,"identity":"19a64e1b-79e9-452d-b218-56b154e9a06b","order_by":5,"name":"Vilna Tyystjärvi","email":"","orcid":"","institution":"University of Bonn","correspondingAuthor":false,"prefix":"","firstName":"Vilna","middleName":"","lastName":"Tyystjärvi","suffix":""},{"id":613786407,"identity":"ba4e0f56-ffc4-4895-97f4-f172d63ce28e","order_by":6,"name":"Miska Luoto","email":"","orcid":"","institution":"University of Helsinki","correspondingAuthor":false,"prefix":"","firstName":"Miska","middleName":"","lastName":"Luoto","suffix":""},{"id":613786408,"identity":"9d681abf-8671-4676-946d-726c40a1cfd2","order_by":7,"name":"Juha Aalto","email":"","orcid":"","institution":"Finnish Meteorological Institute","correspondingAuthor":false,"prefix":"","firstName":"Juha","middleName":"","lastName":"Aalto","suffix":""}],"badges":[],"createdAt":"2026-02-24 09:39:28","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8955565/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8955565/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105756161,"identity":"e2a6102d-20a9-4844-8b35-88bf45bc8b5b","added_by":"auto","created_at":"2026-03-30 16:36:19","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1496751,"visible":true,"origin":"","legend":"","description":"","filename":"manuscriptv1rantanen2026TACunlinked.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8955565/v1_covered_80662926-68a8-47fe-8389-e6add4690d21.pdf"},{"id":105756138,"identity":"e5533708-a5ed-4aba-b069-fa25b883e091","added_by":"auto","created_at":"2026-03-30 16:36:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1659155,"visible":true,"origin":"","legend":"","description":"","filename":"supplementarymaterialrantanen2026TAC.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8955565/v1/0a808344ae73a1ef7681b48f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Substantial spatial heterogeneity in growing season dynamics across northern environments","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"theoretical-and-applied-climatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taac","sideBox":"Learn more about [Theoretical and Applied Climatology](https://www.springer.com/journal/704)","snPcode":"704","submissionUrl":"https://submission.nature.com/new-submission/704/3","title":"Theoretical and Applied Climatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"growing season, growing degree days, microclimate, northern Fennoscandia","lastPublishedDoi":"10.21203/rs.3.rs-8955565/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8955565/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eArctic tundra and boreal forest landscapes exhibit substantial microclimatic temperature variability, driven by strong topographic gradients, heterogeneous snowmelt patterns, and contrasting vegetation structures. However, this fine-scale variability is often poorly represented in reanalyses, climate models, and conventional weather station networks. In this study, we use a total of 347 microclimate loggers deployed across three regions in northern Fennoscandia during 2020\u0026ndash;2024 to examine how the onset, end, duration, and degree days of the growing season vary across the landscapes. Our results show pronounced spatial variation in the onset of the growing season, particularly in the tundra environments, where the earliest and latest onsets differed by up to 40 days within the same season. In contrast, the end of the growing season often occurred abruptly at the three regions, likely driven by changes in large-scale weather conditions. Consequently, the spatial variability in growing season length was primarily driven by differences in its onset. Growing degree sums also varied markedly within areas, with differences of about 400\u0026deg;C days between the warmest and coldest places. The exceptionally warm summer of 2024 corresponded to conditions normally experienced several hundred kilometres further south, highlighting the unprecedented nature of this anomalous summer in northern ecosystems. The findings of this study demonstrate the value of dense microclimate observation networks that advance the understanding of microclimatic processes at ecological scales in cold ecosystems.\u003c/p\u003e","manuscriptTitle":"Substantial spatial heterogeneity in growing season dynamics across northern environments","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-30 16:33:27","doi":"10.21203/rs.3.rs-8955565/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-05-11T18:26:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"155020430784099490447194067634541312141","date":"2026-03-28T14:22:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"320303016278972370890885371541344232259","date":"2026-03-27T21:50:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-27T13:17:25+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-25T05:59:18+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-25T05:58:56+00:00","index":"","fulltext":""},{"type":"submitted","content":"Theoretical and Applied Climatology","date":"2026-02-24T09:21:39+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"theoretical-and-applied-climatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"taac","sideBox":"Learn more about [Theoretical and Applied Climatology](https://www.springer.com/journal/704)","snPcode":"704","submissionUrl":"https://submission.nature.com/new-submission/704/3","title":"Theoretical and Applied Climatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ee1c48f1-6f2d-49fb-a6a3-e34cb2f28bd1","owner":[],"postedDate":"March 30th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-11T18:26:38+00:00","index":31,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-30T16:33:28+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-30 16:33:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8955565","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8955565","identity":"rs-8955565","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}