Seasonal climate signals driving flowering of Robinia pseudoacacia in Piedmont (Italy): implications for apiculture under climate change

Seasonal climate signals driving flowering of Robinia pseudoacacia in Piedmont (Italy): implications for apiculture under climate change | 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 Seasonal climate signals driving flowering of Robinia pseudoacacia in Piedmont (Italy): implications for apiculture under climate change Fausto Carbonari, Chiara Epifani This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7957891/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Apr, 2026 Read the published version in International Journal of Biometeorology → Version 1 posted 4 You are reading this latest preprint version Abstract Flowering dynamics of Robinia pseudoacacia L. (black locust), a key honey plant in southern Europe, are highly sensitive to climate variability and thus serve as a reliable indicator of environmental change. Despite the ecological and economic importance of this species, long-term studies on its flowering behaviour remain limited in Italy. This study analyses a multi-decadal time series of flowering onset dates collected in Piedmont (1981–2025) and validated at the regional scale using data from the IPHEN – Italian Phenological Network (2011–2025). Seasonal thermal indices, derived from the AgERA5 dataset, were evaluated through linear regressions and Monte Carlo cross-validation. During 1981–2025, flowering onset advanced by about 0.5 days per year (p-value < 0.01), consistent with the local warming trend observed over the same period. Among the thermal indices tested, spring temperatures were the main drivers: a 1°C increase in the spring maximum temperature index (mTmax_spring) advanced flowering onset by more than 4 days on average. The winter index (mTmax_winter) also showed a significant, though weaker, negative association, suggesting that milder winters may contribute to earlier flowering, likely by modulating dormancy processes. In contrast, autumn correlations appeared to result from spurious trends linked to global warming. Validation with the IPHEN dataset confirmed the robustness of the spring signal and the predictive role of the winter index, which allows estimates as early as late February, with an average error of about 5 days. The results help clarify the climatic mechanisms driving flowering onset in black locust and provide practical insights for apicultural planning in a changing climate. Robinia pseudoacacia Flowering phenology Seasonal climate signals Thermal indices Apiculture Full Text Supplementary Files SupplementaryMaterial.pdf Cite Share Download PDF Status: Published Journal Publication published 14 Apr, 2026 Read the published version in International Journal of Biometeorology → Version 1 posted Reviewers agreed at journal 07 Nov, 2025 Reviewers invited by journal 06 Nov, 2025 Editor assigned by journal 28 Oct, 2025 First submitted to journal 27 Oct, 2025 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-7957891","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":541133955,"identity":"63f3b10d-eca3-46df-9bd4-d4508cf4671d","order_by":0,"name":"Fausto Carbonari","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Fausto","middleName":"","lastName":"Carbonari","suffix":""},{"id":541133956,"identity":"4f8b0c75-a8bf-428c-9d58-0731a8dfddaa","order_by":1,"name":"Chiara Epifani","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-1636-2116","institution":"CREA-AA-RM: CREA Centro di Ricerca Agricoltura e Ambiente","correspondingAuthor":true,"prefix":"","firstName":"Chiara","middleName":"","lastName":"Epifani","suffix":""}],"badges":[],"createdAt":"2025-10-27 12:17:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7957891/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7957891/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00484-026-03184-7","type":"published","date":"2026-04-14T15:57:03+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":96124677,"identity":"146a022c-1719-4067-b7f8-e27fb2382450","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"xml","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":5929,"visible":true,"origin":"","legend":"","description":"","filename":"ijbmIJBMD2500729.xml","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/5415f2615a9120d7943185b3.xml"},{"id":96124675,"identity":"3dad1c69-7d92-42ac-93b3-51172d616b74","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":1021,"visible":true,"origin":"","legend":"","description":"","filename":"IJBMD25007296252.go.xml","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/5c77bd80c4cb29ed9202f341.xml"},{"id":96250438,"identity":"faa009a7-8609-40d5-be6f-692b2aab6810","added_by":"auto","created_at":"2025-11-19 07:38:22","extension":"xml","order_by":3,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":856,"visible":true,"origin":"","legend":"","description":"","filename":"IJBMD2500729Import.xml","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/b08a60ab51b29ebc3e6e423a.xml"},{"id":96124679,"identity":"f60415b2-7608-418c-b983-aebfe2c4fae9","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"xml","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":152736,"visible":true,"origin":"","legend":"","description":"","filename":"IJBMD25007290enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/02e15323afbfdc87599e0067.xml"},{"id":96124682,"identity":"89209880-e7a4-4e0e-912c-54e6d9107f3d","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":103854,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/59545cc1a90fc4200e411d32.png"},{"id":96250957,"identity":"3f909361-a70e-4ed3-a478-4ff09897e921","added_by":"auto","created_at":"2025-11-19 07:39:09","extension":"png","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":72993,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/88cc272944662b59f241d1ed.png"},{"id":96124678,"identity":"48e13ef0-1813-483d-bb5d-3bf2997d6c51","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"png","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":69806,"visible":true,"origin":"","legend":"","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/c531b1bbe687cb8f1a063d9e.png"},{"id":96247964,"identity":"e9062551-ef87-4444-9163-8d5ef0f28bd4","added_by":"auto","created_at":"2025-11-19 07:27:55","extension":"png","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":37093,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/fd4631b1cbcce499660c4b6f.png"},{"id":96124683,"identity":"c90ca177-2b9b-4fce-8f77-27bbaf2858fc","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"png","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":24396,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/be612415299feac2b9e88414.png"},{"id":96124686,"identity":"d21159ae-cf46-4ce5-98a3-5dde01d984ec","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"png","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":25814,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/13cb926d1920d0b70faf0f4e.png"},{"id":96124684,"identity":"ca773bf3-667b-4509-880d-7dc5e7ab750b","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"xml","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":152729,"visible":true,"origin":"","legend":"","description":"","filename":"IJBMD25007290structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/48a1a2240f3f817bcd3f3abd.xml"},{"id":96124687,"identity":"6a65f89c-d664-411b-a7df-58c58b3ab0fd","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"html","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":162872,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/98c593ac215997319b7ffbda.html"},{"id":107352712,"identity":"c20db19b-7940-4cd7-8e99-141cfe8fe804","added_by":"auto","created_at":"2026-04-20 16:14:51","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":587468,"visible":true,"origin":"","legend":"","description":"","filename":"SeasonalclimatesignalsfloweringofRobiniapseudoacacia.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1_covered_7d880ebc-cdd2-4725-b5c4-0f79fcb28dcf.pdf"},{"id":96124681,"identity":"83101029-2f11-45c6-a373-d3cf9e3e2cc0","added_by":"auto","created_at":"2025-11-17 23:01:24","extension":"pdf","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":896979,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterial.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7957891/v1/de9e8e700af828f571670f03.pdf"}],"financialInterests":"","formattedTitle":"Seasonal climate signals driving flowering of Robinia pseudoacacia in Piedmont (Italy): implications for apiculture under climate change","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-biometeorology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijbm","sideBox":"Learn more about [International Journal of Biometeorology](http://link.springer.com/journal/484)","snPcode":"484","submissionUrl":"https://www.editorialmanager.com/ijbm/default2.aspx","title":"International Journal of Biometeorology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Robinia pseudoacacia, Flowering phenology, Seasonal climate signals, Thermal indices, Apiculture","lastPublishedDoi":"10.21203/rs.3.rs-7957891/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7957891/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFlowering dynamics of \u003cem\u003eRobinia pseudoacacia\u003c/em\u003e L. (black locust), a key honey plant in southern Europe, are highly sensitive to climate variability and thus serve as a reliable indicator of environmental change. Despite the ecological and economic importance of this species, long-term studies on its flowering behaviour remain limited in Italy. This study analyses a multi-decadal time series of flowering onset dates collected in Piedmont (1981\u0026ndash;2025) and validated at the regional scale using data from the IPHEN \u0026ndash; Italian Phenological Network (2011\u0026ndash;2025). Seasonal thermal indices, derived from the AgERA5 dataset, were evaluated through linear regressions and Monte Carlo cross-validation. During 1981\u0026ndash;2025, flowering onset advanced by about 0.5 days per year (p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.01), consistent with the local warming trend observed over the same period. Among the thermal indices tested, spring temperatures were the main drivers: a 1\u0026deg;C increase in the spring maximum temperature index (mTmax_spring) advanced flowering onset by more than 4 days on average. The winter index (mTmax_winter) also showed a significant, though weaker, negative association, suggesting that milder winters may contribute to earlier flowering, likely by modulating dormancy processes. In contrast, autumn correlations appeared to result from spurious trends linked to global warming. Validation with the IPHEN dataset confirmed the robustness of the spring signal and the predictive role of the winter index, which allows estimates as early as late February, with an average error of about 5 days. The results help clarify the climatic mechanisms driving flowering onset in black locust and provide practical insights for apicultural planning in a changing climate.\u003c/p\u003e","manuscriptTitle":"Seasonal climate signals driving flowering of Robinia pseudoacacia in Piedmont (Italy): implications for apiculture under climate change","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-17 23:01:19","doi":"10.21203/rs.3.rs-7957891/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-11-07T07:26:38+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-11-06T16:54:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-28T09:43:08+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Biometeorology","date":"2025-10-27T07:20:30+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-biometeorology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ijbm","sideBox":"Learn more about [International Journal of Biometeorology](http://link.springer.com/journal/484)","snPcode":"484","submissionUrl":"https://www.editorialmanager.com/ijbm/default2.aspx","title":"International Journal of Biometeorology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"34a25a66-0960-4a8a-9661-544b48a717f1","owner":[],"postedDate":"November 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-20T16:14:29+00:00","versionOfRecord":{"articleIdentity":"rs-7957891","link":"https://doi.org/10.1007/s00484-026-03184-7","journal":{"identity":"international-journal-of-biometeorology","isVorOnly":false,"title":"International Journal of Biometeorology"},"publishedOn":"2026-04-14 15:57:03","publishedOnDateReadable":"April 14th, 2026"},"versionCreatedAt":"2025-11-17 23:01:19","video":"","vorDoi":"10.1007/s00484-026-03184-7","vorDoiUrl":"https://doi.org/10.1007/s00484-026-03184-7","workflowStages":[]},"version":"v1","identity":"rs-7957891","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7957891","identity":"rs-7957891","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}