{"refrec":{"BRefID":448628,"RR":"<b>Nelissen, M.; Willard, D.A.; Cittert, H.V.K.; Bowen, G.J.; Hollaar, T.; Sluijs, A.; Frieling, J.; Brinkhuis, H.</b> (2026). Widespread terrestrial ecosystem disruption at the onset of the Paleocene-Eocene Thermal Maximum. <i>Proc. Natl. Acad. Sci. U.S.A. 123(4)</i>: e2509231122. <a href=\"https://dx.doi.org/10.1073/pnas.2509231122\" target=\"_blank\">https://dx.doi.org/10.1073/pnas.2509231122</a>","BEntID":446466,"PublicFlag":1,"CheckedFlag":1,"wosflag":1,"vabbflag":1,"RefStringPartII":". <i>Proc. Natl. Acad. Sci. U.S.A. 123(4)</i>: e2509231122. <a href=\"https://dx.doi.org/10.1073/pnas.2509231122\" target=\"_blank\">https://dx.doi.org/10.1073/pnas.2509231122</a>","DocTypID":8,"DocType":"Journal article","MarineFlag":0,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Nelissen, M.; Willard, D.A.; Cittert, H.V.K.; Bowen, G.J.; Hollaar, T.; Sluijs, A.; Frieling, J.; Brinkhuis, H.","OrigTitleTranslFlag":0,"Authorstringtrunc":"Nelissen, M. <i>et al.</i>","Englishabstract":"The Paleocene-Eocene Thermal Maximum (PETM, similar to 56 Mya) interval was marked by massive C-13-depleted carbon emissions into the ocean/atmosphere system, manifested as a negative carbon isotope excursion (CIE) in sedimentary components, and similar to 5 degrees C global average warming. Episodes of hydrological perturbations and soil-erosion have been widely documented for the PETM but their link with vegetation-and carbon cycle changes remain poorly constrained. Here, we present organic microfossil evidence showing a strong increase in fern-dominated pioneer vegetation that replaced coniferous forests on the margin of the Norwegian Sea during the first millennia of the CIE. With the present stratigraphic constraints, the \"fern spike\" occurred simultaneously in terrestrial settings along the North Sea, Arctic Ocean, the US east coast and in southern Australia, indicating that pioneer vegetation persisted for several millennia following a partial collapse of previously stable terrestrial ecosystems. Both the ferns and influx of microcharcoal imply recurrent physical disturbance, including soil destabilization and erosion, potentially linked to droughts, wildfires, and strong hydrological forcing resulting from extreme climate change. Together with evidence for reworked clay minerals and ancient organic matter (kerogen), these findings show that highly disturbed terrestrial ecosystems were widespread across mid-and high-latitude regions globally. Carbon cycle model simulations suggest that a substantial loss of standing and buried biomass, along with oxidation of soil organic matter, acted as important positive feedbacks during the onset of the CIE. Additionally, enhanced kerogen weathering likely contributed as another major positive feedback throughout both the onset and main phase of the CIE.","AbstractOtherLang":null,"BibLvlCode":"AS","StandardTitle":"Widespread terrestrial ecosystem disruption at the onset of the Paleocene-Eocene Thermal Maximum","OrigTitleLangCode":"en","OrigTitleLangCodeExtended":"eng","OrigTitleLangID":15,"DateLastModified":{"date":"2026-09-30 01:42:46.907390","timezone_type":1,"timezone":"+02:00"},"AuthorKeywords":"carbon cycle;ferns;terrestrial feedback mechanism;climate change;Paleocene-Eocene Thermal Maximum;carbon-isotope excursion;sea-level rise;environmental-change;surface-temperature;methane hydrate;organic-matter;climate-change;boundary;marine;basin","OtherDescriptors":null,"Notes":null,"AnaPub":2026,"MonPub":null,"DateUpdate":"2026-09-28","DateCreate":"2026-09-28","SecASFANote":null,"ConfID":null,"PeerRev":1,"VlizCoreFlag":1,"WoScode":"WOS:001721040000001","VABBcode":null,"OpenAcc":0,"DOI":"10.1073/pnas.2509231122"},"refs":null,"anarec":{"AnaID":448628,"PubliDate":2026,"Pagination":"e2509231122","XtraPublOfAnaID":null,"ISBN":null,"Volume":"123","Issue":"4","BRefMon":null,"BRefMonRR":null,"BRefXtra":null,"BRefXtraRR":null,"SerBRefID":43690,"SerRR":"Proceedings of the National Academy of Sciences of the United States of America. The Academy: Washington, D.C..  ISSN 0027-8424; e-ISSN 1091-6490","StandardTitleSer":"Proceedings of the National Academy of Sciences of the United States of America","ISSN":"0027-8424","AbbrevSer":"Proc. Natl. Acad. Sci. 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