Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna

Cristiano Vignola; Martina Hättestrand; Anton Bonnier; Martin Finné; Adam Izdebski; Christos Katrantsiotis; Katerina Kouli; Georgios C. Liakopoulos; Elin Norström; Maria Papadaki; Nichola A. Strandberg; Erika Weiberg; Alessia Masi

doi:10.1371/journal.pone.0271548

Peer Review History

Original SubmissionMarch 31, 2022
9 May 2022 Decision Letter - Andrea Zerboni, Editor PONE-D-22-09509Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake LernaPLOS ONE Dear Dr. Vignola, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. ==============================The two reviewers greatly appreciated your work and the suggest some minor changes. Among the others, the only moderate to major revision is from Rev.1 who suggests to discuss the paper by Suzanne Jahns as a good reference for your manuscript. I agree with this suggestion and invite you to revise pat of your discussion. 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Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: N/A Reviewer #2: N/A ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). 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You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: This is a well-executed, high quality study of landscape history in an area of notable archaeological importance, primarily based on pollen data. Two of the strengths of the study are firstly, the multi-proxy methodology which allows direct comparison with independent indicators of past climate change from the same core (as reported by Katrantsiotis et al, 2019, GloPlaCha) and, secondly, detailed evaluation of land cover change in terms of the known historical and archaeological record for this region. Although the paper could be published as it is, I think that the authors miss an opportunity by not making systematic comparison with other pollen records from southern Greece and, in particular, with a previous pollen study from Lake Lerna by Suzanne Jahns. They state (Line 165) that “We have … chosen not to provide any direct comparisons between the old and the new record from ancient Lake Lerna”. In fact, no comparison at all is made with the Jahns study in the Discussion section of the paper! Below I outline some of the reasons why the authors should reconsider this. At the least I would like to see one or two additional diagrams comparing selected pollen taxa from the new and old cores, and potentially with other sites. This would widen reader interest in the paper and almost certainly increase its citations. 1. The old (Jahns) pollen diagram has been widely cited (>100 citations) and the data are archived in the European Pollen Database. A critical evaluation in the light of the new core would therefore aid researchers so that the old core results are not misused. Jahns’ chronology is based on 14C dates on bulk sediment samples but this does not necessarily mean that they are incorrect. In fact, as figure 2 of Vignola et al shows, there is no evidence of age offset between dates on bulk sediment and those on plant macrofossils. More important is the fact that the middle section of the old core included a 14C age reversal. Jahns selected the older 14C date as “correct” rather than the younger one, more or less arbitrarily. However, palynological comparison with the new core suggests that this may have been the wrong choice. The main rise in Olea pollen in the new core dates to the early 1st first millennium BCE, not the early 2nd millennium BCE as Jahns suggested for the old core. 2. Comparison of the two pollen cores could also help with interpretation of the new one, for example, in relation to the very abrupt change in pollen assemblages at the zone 1-2 boundary (~200 cm). Although a peak in Pinus and Abies pollen is found in both cores dating to the late 1st millennium BCE, the change is much less abrupt in the old core, suggesting that there may be a hiatus at this point in the new core. This would be supported by the δd23 curve which indicates maximum aridity at this time, potentially linked to desiccation of the ground surface at the core site. In short, two core records may be better than one core in reconstructing regional environmental history. In terms of the wider landscape history, the most striking mismatch with the historical-archaeology record is the surprisingly weak anthropogenic footprint during the Mycenaean period, especially for tree crops like Olea. Although the authors do allude to this, it might be worth greater emphasis. Is this also true for other pollen records near to Late Bronze Age palace settlements; e.g. Pylos? Minor points The authors should compare their results with another recently published study of sediment cores from Lake Lerna (Koskeridou et al 2022). The location of other regional pollen/palaeo sites mentioned should be shown in figure 1; e.g., Stymphalia No mention is made of δd23 methods (even if just to cite 2019 paper by Katrantsiotis in GloPlaCha) Reference cited Koskeridou, E., Thivaiou, D., Psarras, C., Rentoumi, E., Evelpidou, N., Saitis, G., Petropoulos, A., Ioakim, C., Katopodis, G., Papaspyropoulos, K. and Plessas, S., 2022. The Evolution of an Ancient Coastal Lake (Lerna, Peloponnese, Greece). Quaternary, 5(2), p.22. Reviewer #2: This is an interesting paper dealing with the high-resolution study of mid-late Holocene vegetation dynamics in the Argive Plain, NE Peloponnese, aiming at evaluating the relationship between palaeoclimatic fluctuations, human impact and the evolution of the local plant ecosystem. The study area is a striking example of the long-term interaction between human communities and the environment; here, several studies on local palaeoenvironmental changes throughout the Holocene have been done (among them, the reference pollen study at Lake Lerna by Jahns, properly mentioned in the current ms that also raised the dating issues of Jahns’ record), but all lacking the details that can be provided by the current methodological advancements. This research article presents the palynological study of the new sediment core from the ancient Lake Lerna. Based on pollen, NPP and microcharcoal analyses of 84 pollen samples covering the last 5000 years and complementary archaeological, historical and climatic data, the study establishes a cogent connection between climatic and cultural, political, and socio-economic factors in outlining the environmental history of the study area. In this palynological paper, the Authors clearly explain the research topic and methodology; the study design is appropriate to evaluate vegetation patterns and the discussion is based on well-argued data compared to up-to-date relevant studies. In general, beyond the suitability of the studied sediment core, the strong points of the ms are the accurate microscopic analyses and the well-argued interpretation of data that prove the good Authors’ background on past socio-environmental dynamics. The paper could represent a good reference and a new stimulating contribution to the understanding of the complexity of the Mediterranean landscape transformations. Below, I remark just on few points/typos that should be corrected before being published: - Chapter 2.2 = according to botanical nomenclature, please add the author’s name to the plant species name. - Results = I would approximate the decimals of concentration values (e.g. 22,409 pollen grains/g = 22,400 p/g). - L. 478 = ‘Ericaceae’ not in italics. - Conclusions = I suggest including the noteworthy presence of Betula in the Lake Lerna pollen diagram. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: Yes:** Neil Roberts Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0271548.r001
Revision 1
30 Jun 2022 Author Response Reviewer #1 This is a well-executed, high quality study of landscape history in an area of notable archaeological importance, primarily based on pollen data. Two of the strengths of the study are firstly, the multi-proxy methodology which allows direct comparison with independent indicators of past climate change from the same core (as reported by Katrantsiotis et al, 2019, GloPlaCha) and, secondly, detailed evaluation of land cover change in terms of the known historical and archaeological record for this region. Although the paper could be published as it is, I think that the authors miss an opportunity by not making systematic comparison with other pollen records from southern Greece and, in particular, with a previous pollen study from Lake Lerna by Suzanne Jahns. They state (Line 165) that “We have … chosen not to provide any direct comparisons between the old and the new record from ancient Lake Lerna”. In fact, no comparison at all is made with the Jahns study in the Discussion section of the paper! Below I outline some of the reasons why the authors should reconsider this. At the least I would like to see one or two additional diagrams comparing selected pollen taxa from the new and old cores, and potentially with other sites. This would widen reader interest in the paper and almost certainly increase its citations. 1. The old (Jahns) pollen diagram has been widely cited (>100 citations) and the data are archived in the European Pollen Database. A critical evaluation in the light of the new core would therefore aid researchers so that the old core results are not misused. Jahns’ chronology is based on 14C dates on bulk sediment samples but this does not necessarily mean that they are incorrect. In fact, as figure 2 of Vignola et al shows, there is no evidence of age offset between dates on bulk sediment and those on plant macrofossils. More important is the fact that the middle section of the old core included a 14C age reversal. Jahns selected the older 14C date as “correct” rather than the younger one, more or less arbitrarily. However, palynological comparison with the new core suggests that this may have been the wrong choice. The main rise in Olea pollen in the new core dates to the early 1st first millennium BCE, not the early 2nd millennium BCE as Jahns suggested for the old core Thank the reviewer for the comment. Actually, Jahns selected the younger date (3180 � 185 at 251-255 cm) to build her age-depth model, thus any shift between the two record is accountable. We changed the discussion of the ages from Jahns 1993 and took into account difference in local conditions of the two coring sites (e.g. sedimentation rate) starting from the useful suggestion of the reviewer. We also included comparisons with the old core throughout the text, providing a critical interpretation of the vegetation changes in the study area based on all the available data from lake Lerna. 2. Comparison of the two pollen cores could also help with interpretation of the new one, for example, in relation to the very abrupt change in pollen assemblages at the zone 1-2 boundary (~200 cm). Although a peak in Pinus and Abies pollen is found in both cores dating to the late 1st millennium BCE, the change is much less abrupt in the old core, suggesting that there may be a hiatus at this point in the new core. This would be supported by the δd23 curve which indicates maximum aridity at this time, potentially linked to desiccation of the ground surface at the core site. We tried to take into consideration the possibility of soil exposing in our site due to the increased aridity. But the evidence of a sediment hiatus in the new core from comparing the pine/fir peaks is not clear to us. Thanks to the reviewer’s comment, we improved the text. In short, two core records may be better than one core in reconstructing regional environmental history. In terms of the wider landscape history, the most striking mismatch with the historical-archaeology record is the surprisingly weak anthropogenic footprint during the Mycenaean period, especially for tree crops like Olea. Although the authors do allude to this, it might be worth greater emphasis. Is this also true for other pollen records near to Late Bronze Age palace settlements; e.g. Pylos? The human impact during Mycenaean period in our record is mainly displayed by the reduction of thermophilous vegetation and the increase of API, suggesting the land clearance for grazing activities. We think that the scarce presence of Olea pollen at that time can be interpreted as the result of not widespread distribution of olive groves in the Argive Plain. The only exception is represented by a peak of Olea around 1200 BCE when the cultivation could have reached the southeastern part of the plain. Similar evidence has been found at Vravron in Attica, where the nearby settlement grew during Mycenaean times but the onset of olive cultivation is recorded just after this period. On the contrary, in the pollen record of Osmanaga lagoon (Gialova in the text), close to the important city-state of Pylos, the increase in Olea pollen starts during the Late Helladic and confirms the expansion of groves near the basin. We improved the text as suggested by the reviewer. Minor points The authors should compare their results with another recently published study of sediment cores from Lake Lerna (Koskeridou et al 2022 = Koskeridou, E., Thivaiou, D., Psarras, C., Rentoumi, E., Evelpidou, N., Saitis, G., Petropoulos, A., Ioakim, C., Katopodis, G., Papaspyropoulos, K. and Plessas, S., 2022. The Evolution of an Ancient Coastal Lake (Lerna, Peloponnese, Greece). Quaternary, 5(2), p.22.). Thank the reviewer for presenting this new study from Lake Lerna. We referred to it in the text, although a direct comparison with our record is not possible due to 1) the lack of an age depth-model and 2) the absence of major vegetation changes in the new sequence. The location of other regional pollen/palaeo sites mentioned should be shown in figure 1; e.g., Stymphalia The reviewer is right, we added the other sites mentioned in Fig. 1a when they are present in the portion of Greece shown by the map. No mention is made of δd23 methods (even if just to cite 2019 paper by Katrantsiotis in GloPlaCha) We have referred to the original publication (Katrantsiotis et al. 2019) when mentioning the methodology for isotopic analysis in the discussion and Fig.7 caption as well. Reviewer #2 This is an interesting paper dealing with the high-resolution study of mid-late Holocene vegetation dynamics in the Argive Plain, NE Peloponnese, aiming at evaluating the relationship between palaeoclimatic fluctuations, human impact and the evolution of the local plant ecosystem. The study area is a striking example of the long-term interaction between human communities and the environment; here, several studies on local palaeoenvironmental changes throughout the Holocene have been done (among them, the reference pollen study at Lake Lerna by Jahns, properly mentioned in the current ms that also raised the dating issues of Jahns’ record), but all lacking the details that can be provided by the current methodological advancements. This research article presents the palynological study of the new sediment core from the ancient Lake Lerna. Based on pollen, NPP and microcharcoal analyses of 84 pollen samples covering the last 5000 years and complementary archaeological, historical and climatic data, the study establishes a cogent connection between climatic and cultural, political, and socio-economic factors in outlining the environmental history of the study area. In this palynological paper, the Authors clearly explain the research topic and methodology; the study design is appropriate to evaluate vegetation patterns and the discussion is based on well-argued data compared to up-to-date relevant studies. In general, beyond the suitability of the studied sediment core, the strong points of the ms are the accurate microscopic analyses and the well-argued interpretation of data that prove the good Authors’ background on past socio-environmental dynamics. The paper could represent a good reference and a new stimulating contribution to the understanding of the complexity of the Mediterranean landscape transformations. Below, I remark just on few points/typos that should be corrected before being published: Chapter 2.2 = according to botanical nomenclature, please add the author’s name to the plant species name. Ok, done. Results = I would approximate the decimals of concentration values (e.g. 22,409 pollen grains/g = 22,400 p/g). Ok, done. L. 478 = ‘Ericaceae’ not in italics. Thanks, we modified it. Conclusions = I suggest including the noteworthy presence of Betula in the Lake Lerna pollen diagram. Thank the reviewer for this suggestion, we have stressed the presence of Betula in the conclusion. Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0271548.r002
4 Jul 2022 Decision Letter - Andrea Zerboni, Editor Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna PONE-D-22-09509R1 Dear Dr. Vignola, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Andrea Zerboni, Ph.D. Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0271548.r003
Formally Accepted
6 Jul 2022 Acceptance Letter - Andrea Zerboni, Editor PONE-D-22-09509R1 Mid-late Holocene vegetation history of the Argive Plain (Peloponnese, Greece) as inferred from a pollen record from ancient Lake Lerna Dear Dr. Vignola: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Prof. Andrea Zerboni Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0271548.r004

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