Caroline Jobin
email: caroline.jobin@mines-paristech.fr

Sophie Hooge

Pascal Le Masson

) ; Le Masson

The logics of double proof in

Keywords: Design theory, Design process, Process modelling, Experimentation, Proof of concept

INTRODUCTION

Since its introduction in the United States aeronautics and aerospace ecosystem in the 1960s, proof of concept (PoC) has progressively become a gold standard early test step in design processes [START_REF] Bendavid | A 'living laboratory' environment for exploring innovative RFID-enabled supply chain management models[END_REF][START_REF] Cooper | The agile-stage-gate hybrid model: a promising new approach and a new research opportunity[END_REF]. In the mid-2010s, les Sismo, which is a French independent design studio founded in 1997, adopted this terminology and transformed it into a service offering for its clients. Les Sismo consists of about 20 designers who articulate the skills necessary for the creation, strategy, and realisation of humanist projects for private and public organisations. Les Sismo is renowned for its expertise in PoC for service and experience design in the French design community. In 2018, les Sismo shared that it found PoCs to be valuable not only for validation but also exploration. It declared that its PoCs identify some scientific experimentation codes, but did not state them. By contrast, it declared that its PoCs generate results richer than those from scientific experimentation, but did not explain the additional cognitive value achieved compared with scientific experimentation or the manner in which this occurred. Only snippets of additional information can be found in the literature because, to the best of our knowledge, no rigorous, systematic, and scientific research on this notion has been undertaken. The research community has interpreted the massive adoption of PoC by various actors and ecosystems in recent years as a trivial phenomenon; however, in our view, it contains an interesting research object. We believe that the success of PoC can be explained by its original ability to combine the proof of the known and proof of the unknown. Our purpose in this paper is to investigate this double nature of PoC.

I. LITERATURE REVIEW AND EXPERIMENTATION DESIGN MODELLING

Validation and Exploration: Beyond Negative Interference, Towards Positive Interference

The literature suggests that there are several possible forms of experimentation (see, for instance, [START_REF] Gillier | Experimenting in the unknown: lessons from the Manhattan project[END_REF]. In particular, the design literature has focused on distinguishing between explorationbased experimentation and validation-based experimentation [START_REF] Mahmoud-Jouini | Unpacking the notion of prototype archetypes in the early phase of an innovation process[END_REF][START_REF] Blomkvist | Existing prototyping perspectives: considerations for service design[END_REF][START_REF] Cross | Engineering design methods[END_REF][START_REF] Nicolaÿ | Experimenting and prototyping the design of complex services[END_REF]Lenfle, 2019, Jensen at al., 2017). These typologies reflect a good practice of the scientific method [START_REF] Hacking | Representing and intervening: introductory topics in the philosophy of natural science[END_REF], which recommends that researchers should first explore and then validate [START_REF] Simpson | What weather modification needs-a scientist's view[END_REF]. Such a sequential approach is supported by the fact that exploration and validation are identified as two mechanisms that are mutually detrimental. Exploration induces biases in the validation process and, by contrast, validation induces barriers in the discovery process [START_REF] Guilford | Creative abilities in the arts[END_REF][START_REF] March | Exploration and exploitation in organizational learning[END_REF]; that is, the literature almost systematically presents the interaction between exploration and validation as destructive, to use the language of wave theory. The massive literature that supports this thesis suggests that this case exists, but we question whether this thesis can be extended. We question whether other interaction scenarios can be considered, for example, a neutral or synergistic interaction in which the performance of the validation and exploration processes performed simultaneously is, respectively, identical to or greater than the performance of the processes performed separately. Additionally, we question whether these typologies are theoretical impossibilities or are waiting for empirical cases to be described. A peripheral part of the literature claims that other arrangements of validation and exploration is possible [START_REF] Gillier | Experimenting in the unknown: lessons from the Manhattan project[END_REF][START_REF] Löfqvist | Design processes and novelty in small companies: a multiple case study[END_REF]. Some literature, both old and recent, underlines the importance of the scientific method, that is, a systematic, rigorous, and organised activity as a means of discovery [START_REF] Jobin | What does the proof-of-concept (POC) really prove? A historical perspective and a cross-domain analytical study[END_REF][START_REF] Lakatos | The methodology of scientific research programmes[END_REF]Le Châtelier, 1936;[START_REF] Mees | The organization of industrial scientific research[END_REF][START_REF] Perrin | La nouvelle espérance[END_REF]. However, these studies remain at the statement level and lack a rigorous framework for modelling the production of knowledge associated with the validation and exploration mechanisms. Therefore, we consider what validation and exploration mechanisms are at work in PoC, and the associated conditions.

Experimentation Modelling: Contributions of Statistical Theory Enriched by Design Theory

For a long time, the literature on statistical tests has clarified widely disseminated validation logic [START_REF] Dagnelie | La planification des expériences : choix des traitements et dispositif expérimental[END_REF][START_REF] Emmert-Streib | Understanding statistical hypothesis testing: the logic of statistical inference[END_REF][START_REF] Neyman | On the problem of the most efficient tests of statistical hypotheses[END_REF]. This logic contains a design hypothesis: we can design at least one unit, and identify and measure some of its characteristics, called variables. Statistical test theory presupposes, more broadly, an intrinsic design activity (e.g., hypothesis design) and sometimes requires design effort when available tools are not appropriate (e.g., a new observation instrument), but suggests that these elements are given. Moreover, in the test theory framework, the knowledge bases on which the experimentation rely also remain largely implicit. A clarification study could better underline the gap between what was known and unknown before and after experimentation and therefore trace the accumulation or expansion of knowledge. More generally, it could also provide a better understanding of both what happens during experimentation and the results obtained, particularly when they are not as expected. The latest advances in design theory [START_REF] Le Masson | Design theory[END_REF][START_REF] Hatchuel | Design theory: a foundation of a new paradigm for design science and engineering[END_REF] may contribute to this explication effort, and integrate and complete the experimentation modelling provided by test theory and [START_REF] Thomke | Experimentation matters: unlocking the potential of new technologies for innovation[END_REF]. Concept-knowledge (C-K) theory [START_REF] Hatchuel | CK design theory: an advanced formulation[END_REF] was chosen for formalising a general framework to monitor the reasoning mechanisms of exploration and validation in experimentation [START_REF] Hatchuel | Beyond models and decisions: situating design through generative functions[END_REF] because of its most advanced ability to account for the generativity of a design process [START_REF] Hatchuel | A systematic approach of design theories using generativeness and robustness[END_REF][START_REF] Hatchuel | Design theory: a foundation of a new paradigm for design science and engineering[END_REF]. C-K theory models the design process through the dual expansion of the concept space and knowledge space. Knowledge (K) is a logical proposition that can be assessed as true or false.

A concept (C) is a desirable proposition that has no logical status in the existing knowledge space (i.e., neither true nor false).

Proposal for a General Framework of Experimentation Design based on C-K Theory

The general framework in Figure 1is based on the following notation. The initial concept is characterised by a partially unknown entity (X), which verifies a set of properties (P), for instance, "common spaces that re-enchant the customer". The expansion of the concept space is performed through the generation of a set of properties (Pi), for instance, "by improving check-in", i = 1,…, n and j = 2,…, n.

Research Approach

Based on this general framework of experimentation design, we highlight three typologies of learning mechanisms associated with proof models. We call these proof models proof of the known, proof of the known and proof of an independent unknown, and proof of the known and proof of a dependent unknown. For each of these models, we attempt to identify these learning mechanisms in PoC cases conducted by les Sismo. We selected five cases of les Sismo's PoC following theoretical sampling. In a sense, we chose them for their ability to illustrate the three proof models and not for their potential for generalisation or representativity [START_REF] Eisenhardt | Theory building from cases: Opportunities and challenges[END_REF].

Data Collection and Analysis

The data collection was performed as part of an intervention research study [START_REF] Hatchuel | Collaborating for management research, from action research to intervention research in management[END_REF][START_REF] Radaelli | Intervention research as management research in practice: learning from a case in the fashion design industry[END_REF] conducted by the authors from October 2018 at les Sismo. We use five client project cases to illustrate the proof models: one to illustrate the mechanism of the proof of the known (Illustration 1.1), two to illustrate the mechanism of the proof of the known and proof of an independent unknown (Illustrations 2.1 and 2.2), and two to illustrate the mechanism of the proof of the known and proof of a dependent unknown (Illustrations 3.1 and 3.2). Regarding Illustrations 1.1, 2.1, 2.2, and 3.1, PoC took place between February 2016 and October 2017. Data collection for retrospective analysis was performed between October 2018 and April 2019 through formal and informal interviews with project managers and co-founders. These data were triangulated and supplemented by information from working documents and project deliverables found in les Sismo's digital archives. For Illustration 3.2, a longitudinal study [START_REF] Åhlström | Longitudinal field studies[END_REF] was conducted by the first author between November 2018 to April 2019. The design of the PoC started in December 2018 and PoC took place in March 2019. Given that the launch of the project was in January 2018, interviews with members of the project team were conducted and information was collected from internal documents (e.g., working documents, minutes of meetings with clients, and deliverables) prior to November 2018. The data from November 2018 was collected through frequent participation in working sessions with the project team or in pairs with the project manager, active participation during the two days of testing, and follow-up on the elaboration of restitution and list of recommendations. For each illustration, we used the same description structure based on the general framework proposed: concept and hypothesis design, hypothesis embodiment and observation device design, embodiment and observation device confrontation and hypothesis validation, and outcomes.

III. THREE PROOF MODELS AND ASSOCIATED ILLUSTRATIONS

Type 1: Proof of the Known

Reasoning Mechanism 1

This first proof model describes experimentation for which the learning process is limited to the validation or invalidation of a set of hypotheses, for example, performing an operation from the C space to the K space, that is, a conjunction in the terms of C-K theory. The reasoning mechanisms of this type of experimentation are the very essence of a statistical test. Test theory foresees two possible outcomes, that is, the rejection of the null hypothesis in favour of the alternative hypothesis or the rejection of the alternative hypothesis in favour of the null hypothesis, that produce an extension or sophistication of theories and models. Moreover, there is a third transitory case in which the test is inconclusive, that is, sometimes the data tend towards the null hypothesis validation and sometimes the data tend towards the alternative hypothesis validation. This case requires the designer/experimenter to verify its experimental design, and if necessary, use the identification of a new variable to revise its experimental design to conduct a better controlled experimental process in the hope of validating the hypothesis. This proof model relies on sequential logic: exploration and then validation.

Illustration 1.1
Concept and hypothesis design. The client organisation was a French hotel chain that offers short-and medium-term rental apartments in cities. In the mid-2010s, the organisation was challenged by new protean competition and changing consumption patterns. In this context, the organisation initiated several projects, such as the renovation of its aparthotels. Unfortunately, this massive investment did not result in significant improvement in the opinion and brand identification of its clients. In 2016, the brief delivered to les Sismo was to help the organisation to transform common spaces to re-enchant customers. Les Sismo started its mission by conducting observations and interviews in the common areas of a hotel (e.g., corridors, lifts, parking, and rubbish bin area). It conducted an observation relevant to an inquiry in the rubbish bin area. Indeed, it observed that almost-new objects were abandoned next to the rubbish bins. By pushing the investigation with employees, les Sismo learned that this observation was not an isolated case, and a large number of clients stayed for several months for professional reasons. These professional customers enjoyed customising their apartments with accessories (e.g., cushions, curtains, small furniture, and frames). Les Sismo proposed an object library in the hotel lobby containing items that clients could borrow free of charge and without a time limit simply by notifying an employee. These objects would allow clients to customise or equip their apartment to make their stay more pleasant. The project sponsors were resistant to this idea because they feared that the items would be stolen. The project sponsors finally conceded that they should not automatically dismiss the concept based on this hypothesis, but the hypothesis had to be validated using field experimentation. Hypothesis embodiment and observation device design. Les Sismo bought and installed a library containing about 20 items (e.g., lamps, frames, mirrors, fitness weights, and cushions) in the lobby of a hotel in the chain. The service was promoted at the reception desk and through a sign on the library stating "items to borrow for personalising your apartment". The PoC lasted six months. The objects were tracked during the six months by the receptionists using a very simple and low-cost system. Each item was labelled with a code (three letters and two digits) and referenced in an Excel spreadsheet. When a client wanted to borrow an item, a receptionist retrieved the associated code and registered it in the Excel spreadsheet. The receptionists regularly compared the library inventory and the data in the Excel spreadsheet. Les Sismo conducted observations and interviews during the first week to survey the client experience in relation to the object library. Embodiment and observation device confrontation and hypothesis validation. During the test period, no theft was reported, to the great surprise of the client sponsors, which allowed les Sismo to invalidate the client's hypothesis. The original evaluation setup enabled the observation of a phenomenon that was even further from the sponsors' view of their clients: the receptionists tracked an increase in the quantity of objects through the contributions of some clients. Outcomes. The PoC allowed les Sismo to invalidate the client's hypothesis and validate its own hypothesis. The PoC permitted the validation of the desirability and viability of the concept. At the end of the PoC, the test establishment decided to integrate the object library in a sustainable manner in terms of both the content and logistics. At the end of 2020, two-thirds of the aparthotel network implemented the object library, which represents about 80 establishments.

Type 2: Proof of the Known and Proof of an Independent Unknown

Reasoning Mechanism 2

This second proof model describes experimentation that not only allows hypothesis validation but also reveals unknown peripheral variables, that is, variables that do not have a direct impact on the outcome of the hypothesis validation. Such a discovery requires the prior design of an extended observation device and model to enable this capture, and clarification of knowledge bases to enable its recognition as a novelty. In this proof model, validation and exploration are performed in parallel. The exploration mechanism relies on the validation mechanism, but does not interfere with it. The designer/experimenter takes advantage of the experimental scenario to explore the periphery.

Illustration 2.1

Concept and hypothesis design. The client organisation was a major European hotel group that faced similar challenges to those presented in the previous illustration. The group asked les Sismo to help it to reinvent the hosting experience in one of its hotel brands to attract new customers, particularly Millennials. The inspiration phase highlighted that Millennials want to save money, even if it means more work for them. The ideation phase gave rise to the hypothesis that a collaborative economy could be implemented by asking clients to perform certain tasks in return for economic savings. Les Sismo wanted to test what tasks customers were willing to perform and how they wanted to be rewarded. Hypothesis embodiment and observation device design. For a few days, the clients of a hotel in the chain were offered the possibility of undertaking some tasks (e.g., make the bed, vacuum, wash windows, and carry out small repairs) in exchange for a €5 voucher that could be used in a selection of shops nationally. Tasks were calibrated to last no more than 30 minutes and did not require training. Each task had a checklist and the required items or tools. These kits evolved during the week. The hotel's employees were responsible for explaining the test, in addition to the promotion of daily tasks, checking each accomplished task, and rewarding clients. During the test week, there was a follow-up of the tasks performed by clients and the discount vouchers provided. In a complementary manner, les Sismo conducted observations and interviews with clients and employees. It investigated why the clients were more willing to perform some tasks, and their motivation. Embodiment and observation device confrontation and hypothesis validation. Twenty vouchers were given away in a holistic manner. Only "basic" and "self-contained" tasks were performed. Indeed, clients only performed tasks they were familiar with and did not perform tasks that could have an impact on someone other than themselves. One guest vacuumed a corridor, but every other task (small repairs, painting jobs, and window washing) remained undone. Regarding the possibility of making a bed, 90% of clients took the sheets and accepted making their beds and 50% declared that they would have done this without a reduction. Les Sismo learned that people accepted making their beds to ensure that it was done according to their expectations and, above all, to control the cleanliness of the mattress. Outcomes. The PoC clarified the field of validity of the concept relative to the possibility of the client performing certain tasks in exchange for a reduction. Furthermore, the PoC revealed a peripheral variable: the importance to the client of easily checking the cleanliness of the mattress.

Illustration 2.2

Concept and hypothesis design. The client organisation was a state agency in charge of employment. Its role is to compensate job seekers and guide them back to work, and to guide companies in their recruitment. In connection with its strategic plan for 2020, the organisation developed a new digital pathway for job seekers that was a great success. The agency wanted to replicate this success in the physical pathway of job seekers. Therefore, the agency launched a consultation in 2016 to obtain help with the development of a new agency model for its 1,000 local offices across the country. This consultation was won by les Sismo. Based on the inspiration phase conducted by les Sismo, a work axis emerged about a warmer and more reassuring welcome, and gave rise to a co-creation workshop dedicated to this theme. Propositions were made about furniture, decoration, space design, posture, and speech. Les Sismo formulated the hypothesis that meetings between counsellors and job seekers would be warmer if they were side by side rather than face to face. When les Sismo began to survey the employees, strong reactions emerged from some counsellors who categorically refused this new posture. As the discussion progressed, les Sismo understood that there were two types of meetings. The first type was dedicated to guiding the job seeker on his/her way back to work. The second type was dedicated to the discussion of financial support. This type of meeting was sometimes difficult, particularly regarding overpayments. It was not uncommon for the tone to rise and the job seeker to become aggressive. The side-by-side posture was therefore a source of fear for counsellors who had regularly experienced this type of scenario. The traditional desk and face-to-face posture had the merit of creating a safe distance. Hypothesis embodiment and observation device design. These first interviews helped les Sismo to narrow the test sample. The PoC was conducted only for the first type of meeting in a voluntary agency for one week. The advisory areas were equipped with tables of different shapes (rectangular, square, and round) to test new postures. Two types of seats were installed around this table: a fixed seat for the job seeker and a mobile seat for the advisor, which allowed him/her to choose a position around the table. To facilitate the different types of positions during the interview, the advisors were equipped with portable computers. During the test week, les Sismo conducted observations of meetings between advisors and job seekers when possible, and interviewed them both to evaluate the advantages and disadvantages of each table shape. The criteria covered the exchange quality, screen sharing, freedom of movement, position ergonomics, and feeling of security. The last criterion was added following preliminary discussions. Embodiment and observation device confrontation and hypothesis validation. The PoC generated information on the effects of this new posture; both positive (enhancement of human contact, apprehension reduced by conviviality, pleasant and peaceful environment for all, and dynamic and pedagogical posture) and negative (delicate proximity to difficult people, lack of ergonomics and practicality because of the table legs, and nuisance caused by the open architecture). A very interesting critical variable was indicated by advisors: the sound level. Being closer naturally invited job seekers to speak less loudly, which tended to reduce aggression and therefore, create a climate of confidence and serenity. Outcomes. The PoC allowed not only the validation of a new posture and the furniture characteristics that could promote and ease it, but also the identification of an unknown peripheral variable, which was the sound level.

Type 3: Proof of the Known and Proof of a Dependent Unknown

Reasoning Mechanism 3

This third proof model describes experimentation that reveals unknown variables that play a significant role in the outcome of hypothesis validation through invalidation or inconclusiveness. In the sense of test theory, it describes the identification of an unknown moderating variable, that is, a variable that changes the strength or direction of the effect between the two variables of interest. Such a discovery requires extended prior exploration (e.g., alternative hypotheses, embodiment and observation devices and models, and sampling) to enable the unknown variable to be captured. The discovery forces the designer/experimenter to clarify the validity conditions of the theory or model on which the hypotheses are based. This new known variable may be seen as an additional variable to be controlled or measured in future experimentation or as a source of innovation. This new known variable forces the designer/experimenter to revise knowledge previously considered as established, that is, a K-reordering; and design undecidable hypotheses, models, and theories, that is, perform an operation from the K space to the C space, that is, a disjunction in the terms of C-K theory. In this proof model, validation and exploration are combined, and both mechanisms positively interfere with each other.

Illustration 3.1

Concept and hypothesis design. The client organisation was a cooperative supermarket chain. An internal innovative challenge underlined the issue that it was difficult for some customers (e.g., older adults and frail people) to carry heavy items, and raised the idea of developing a new service to offer support to customers with heavy loads. Les Sismo was asked by the headquarters of the organisation to prototype and test the concept in 2016. The service concept can be divided into three main steps: scanning the labels of the heavy items using the supermarket's mobile application, presenting the barcodes in the mobile to the cashier for scanning, and collecting the heavy items at the supermarket's drive-through. The client organisation and les Sismo hypothesised that customers wanted this service to secure the development of the mobile application and its associated logistics. Hypothesis embodiment and observation device design. The service concept was prototyped without the mobile application and implemented during five days at a supermarket in the chain. Service prototyping and delivery required few technical and human resources. The labels of 30 selected items were printed and positioned near the price tag using basic plastic supports. Customers who wanted support to carry these items could pick up the labels and present them to the cashier. The cashier then informed les Sismo representatives, who were wearing T-shirts flocked with the logo of the service concept and wings, who collected the items from the supermarket shelves. They transported the items to the drive-through via roller bins that the supermarket already had and put the items in the boot of the customer's car. For five days, les Sismo conducted observations and interviews with the supermarket's customers. The first hours and days were very disappointing, to the great surprise of the client organisation and les Sismo, because few people used the service. Les Sismo was so persuaded of the relevance of the concept that it made adjustments throughout the week. For example, it tried to improve communication about the service by increasing the service promotion devices and contact points (e.g., on the shopping trolley and at the supermarket's reception desk). Embodiment and observation device confrontation and hypothesis validation. The PoC generated a first key piece of information that could have probably been identified by a prior observation step. When fragile people plan to purchase heavy items that they buy exceptionally (e.g., a bag of barbecue charcoal), they come with a relative, and the shopping session almost becomes an excuse to have company. This learning pushed les Sismo to refocus on items that people bought more regularly (pack of water or milk). The PoC generated a second key piece of information that derived from a strange observation. Les Sismo observed an older adult who came to the supermarket at the beginning of the week and strongly refused the service. The same older adult came back a few days later and begged for the service. Les Sismo associated this reversal with the presence and absence of his wife on his first and second visits, respectively. Les Sismo understood that the customer wanted, with a certain amount of pride, to show his wife that he was still able to carry heavy loads. Similarly, one parent shopping with a child did not tend to accept the service, although it was free of charge. Although the service added an additional step in the parent's journey (a stop at the withdrawal zone), the refusal was more related to the fact that the parent wanted to show that he/she was doing well on his/her own. Once the self-esteem variable was discovered, it helped les Sismo to clarify the following incomprehensible results: people who seemed to be in good shape used the service, whereas people who seemed to be vulnerable refused the service. Indeed, this provided an explanation of why people generally refused or accepted the service. People with good self-esteem tended to accept the service, whereas people with poor self-esteem viewed the service as disturbingly highlighting their vulnerability and therefore tended not to accept the service. Outcomes. The PoC allowed an invalidation of the concept for the initial target and, in that sense, led the client organisation to abandon the project while the investment in the project was very low. By contrast, the PoC allowed the identification of a critical variable (self-esteem of the customer), which interfered with the test and caused some clients to decline the service.

Illustration 3.2

Concept and hypothesis design. The client organisation was a global leader in urban mobility that develops, operates, maintains, and modernises innovative public transport systems. One of the goals reported in its strategic plan for 2025 was to place the travelling experience at the heart of its actions. In connection with this ambition, the client organisation launched a call for tender at the end of 2017 to find help to rethink the traveller's experience at the level of its information and sales areas, which take the form of a traditional counter. Les Sismo won this call for tender. The inspiration and ideation phase led les Sismo to formulate a hypothesis. It believed that the traveller's experience could be improved by the agent having a warmer posture, and that this new posture could be promoted by a new configuration of the counter furniture and area (in the same vein as Illustration 2.2). Hypothesis embodiment and observation device design. Two configurations with different degrees of opening were prototyped. One of the configurations was embodied by a triangular counter with a completely open counter space and no difference in floor height compared with the remainder of the space. The prototyped counter furniture and area were installed during one day in a large network station in a reformed space. Another counter located nearby was closed to maximise the flow of travellers to the test area. A volunteer employee was seconded from his position to participate in the test. Before taking up the position, he was quickly briefed about the actions he could perform in the context of the test (e.g., he could only sell metro tickets). The issue related to queue management had already been identified, and to investigate this issue, different devices were added for the test (e.g., belt barriers) and different configurations were tested. Three designers were dedicated to the observation of the behaviour of travellers and employees during the day of the test of this second configuration. They had different viewpoints of the test area and station. They interviewed volunteer travellers in the station who either tested or did not test the new experience. Embodiment and observation device confrontation and hypothesis validation. Regarding the hypothesis that the traveller's experience would be improved by giving the agent more freedom of movement, the test data were inconclusive. Travellers perceived the agent to be more dynamic and available in general with this new configuration. However, this new configuration induced agent behaviour that les Sismo had imagined, but not its consequences. The agent tended to move away more or less strongly from the counter space to better advise travellers. Returning to the perimeter close to the counter was not a reflex for the agent, but he continued to keep the counter in sight. He only returned to the counter area if someone started to wait there. The issue is that this counter configuration was so disruptive that few people understood that if they waited in this test area an agent would come soon. By contrast, on the way back, the agent was often intercepted by travellers, which created competition and therefore tension for travellers who were still waiting wisely near the counter. Les Sismo had thought about the problem of queue management at the counter level, but not at the station level. As queue management was already an observation criterion and because of les Sismo's observation model and device, les Sismo quickly became aware of this issue. It made this knowledge a lever for creating value through the creation of a new post: a "mobile agent" who was not associated with a counter and could provide an additional service in the station. This new position could limit the pitfall observed because the agent could pass the baton to the mobile agent if the advice required great mobility. Outcomes. The PoC clarified the area of validity of the concept: the PoC showed the relevance of opening the counter, but not too much. Indeed, the other configuration tested that was semi-open was more appreciated by travellers and agents. Finally, the PoC revealed the interdependence between agent mobility and queue management, and generated new creative ideas.

IV. CONCLUSION AND DISCUSSION

In this paper, we investigated the question of what design logic might enable the combination of exploration and validation in proof of concept. We first used design theory to build an experimentation design framework. This framework highlighted a typology of proof logics in experimentation related to proof of the known and proof of the unknown. The key characteristics of these proof models are presented in Table 1. Furthermore, we found that the initial experimentation design influenced the type of proof models that could be achieved. If a minimum experimentation design was required to validate the hypothesis (proof of the known), additional design activity had to be performed to enable the proof of the unknown (e.g., extending the observation model and formulating a variety of hypotheses). The search for proof of the known is a necessary but insufficient condition for proof of the unknown. The more the designer/experimenter systematically explains the design alternatives and the associated knowledge (expansion), the more new concepts and knowledge will be generated. Second, we succeeded in identifying the three logics in PoC cases conducted by les Sismo that were used in this paper as illustrations of the proof models. Experimentation design modelling and proof of the known support why les Sismo felt that its PoC followed scientific reasoning. The mechanism for the proof of the known was found in both scientific experimentation and les Sismo's PoC. Moreover, the clarification of the three proof models provided a better understanding of how PoC can sometimes do more than a statistical test, which is a gold standard for scientific experimentation that focuses only on the proof of the known. In this sense, the PoC may have generative properties superior to scientific experimentation. However, the reverse may also be true if the PoC is not well designed and conducted; the proof of the known can therefore be reduced or aborted, and consequently, similarly for the proof of the unknown. The mechanisms highlight the difficulty in managing the PoC. Indeed, many dimensions are mixed: some are related to the concept space and others to the knowledge space, and often associated with very varied bases of knowledge. Strong expertise is therefore needed to avoid falling back into the paradigm of a negative interaction between exploration and validation. Work remains to be done to investigate the most appropriate context for each of the three logics and explain further the differences between design activities regarding them. We used different client case studies to illustrate the three mechanisms, but further work should show that they are compatible, that is, these three mechanisms can be found in the same PoC, but this makes PoC management even more complex. Finally, the modelling of the PoC as a double proof, that is, proof of the known and proof of the unknown, enriches the unique representation of PoC as a tool for the go/no-go decision [START_REF] Bendavid | A 'living laboratory' environment for exploring innovative RFID-enabled supply chain management models[END_REF][START_REF] Cooper | The agile-stage-gate hybrid model: a promising new approach and a new research opportunity[END_REF]. Indeed, beyond being a milestone in the design process, PoCs can help with structuring the design process that must deal with the complex process of accumulation of knowledge and rediscussion of certain knowledge, similar to experimentation in the unknown. The mechanisms associated with the double proof provide a better understanding of how PoCs can gradually validate dimensions, question the relevance of dimensions, and discover new dimensions to be tested.

Figure 1 :

 1 Figure 1: General framework of experimentation design based on C-K theory

Table 1 .

 1 Key characteristics of the three proof models

Proof Typology Arrangement of Exploration and Validation Mechanisms How Knowledge was Proved How the Concept was Proved

	Proof of the known Sequential: exploration	Extension/sophistication	N/A
		then validation	of theories and models
	Proof of the known	Parallel: experimentation	Extension/sophistication	Identification of, for
	and proof of an	is an opportunity for	of theories and models	example, unknown
	independent	peripheral exploration		peripheral variables
	unknown			and hypotheses
	Proof of the known	Combinatorial: validation	Reconsideration of, for	Regeneration of, for
	and proof of a	and exploration	example, variables,	example, variables,
	dependent unknown	synergistically interfere	hypotheses, models, and	hypotheses, models,
			theories	and theories


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Ali Pourmand

Lake Neor reveals how mountain vegetation responded to 7000 years of hydroclimate variability in northwestern Iran

Keywords: climate change, Holocene, Irano-Turanian vegetation, Peatland, PCA Adonis vernalis, Alc: Alchemilla, Aln: Alnus, Ali: Alisma, And: Androsace chamaejasme, Api: Apiaceae, Art: Artemisia, Bet: Betula, Bra: Brassicaceae, Cal: Callitriche stagnalis, Carpe: Carpesium, Carp: Carpinus, Car: Caryophyllaceae, Cas: Castanea sativa, Cel: Celtis, Cen nig: Centaurea nigra, Cen sol: Centaurea solstitialis, Che: Chenopodiaceae, Cic: Cichorioideae, Cir: Cirsium, Cou: Cousinia, Cra: Crassulaceae, Cyp: Cyperaceae, Eph: Ephedra distachya, Eup: Euphorbia, Fab: Fabaceae, Fag: Fagus, Gal: Galium, Hip vul: Hippuris vulgaris, Jug: Juglans, Lac: Lactuceae, Lem: Lemna minor, Lin: Linum, Lot: Lotus, Lys: Lysimachia vulgaris, Mat: Matricaria, Ole: Olea, Oxa: Oxalis stricta, Pap: Papaver rhoeas, Pin: Pinus, Pla cor: Plantago coronopus, Pla lan: Plantago lanceolata, Plu: Plumbaginaceae, Poa: Poaceae, Pri: Primula algida, Pte: Pterocarya fraxinifolia, Que: Quercus, Ran: Ranunculus, Res: Reseda lutea, Rha: Rhamnaceae, Ros: Rosaceae, Rum: Rumex acetosa, Sal: Salix, Salv: Salvia verticillata, Sam: Sambucus nigra, Scr: Scrophulariaceae, Sen: Senecio, Sol: Solanum nigrum, Spa: Sparganium erectum, Tam: Tamarix, Tha: Thalictrum, Ulm: Ulmus,

Palynological and geochemical analyses provide valuable information about modern and past climatic regimes and vegetation. The impact of climate and humans on past vegetation in the semi-arid areas of northwestern Iran has received increased interest in the wake of warming temperatures in the Middle East. Palynological and down-core XRF elemental abundances from a peat core from Lake Neor enabled a reconstruction of vegetational changes of the past 7000 years over the highlands of northwestern Iran. Periods of increased arboreal pollen (AP) types and high (Artemisia + Poaceae)/Chenopodiaceae ratios along with low titanium abundances, high percentages of total organic carbon, more negative δD values, and higher carbon accumulation rates suggest a relatively wet climate. These conditions have persisted during the periods 6700-6200, 5200-4450 and 3200-2200 cal a BP. The overall low AP values, substantial rise of Chenopodiaceae, high Ti abundances and low values of palaeo-redox proxies, are all evidences of a drier climate, as has been reconstructed for the periods 6200-5200 and 4030-3150 cal a BP and the last 2200 years. An important feature of the last centuries is the increase of anthropogenic and pastoral indicator pollen types. Our results may provide basic data to predict future trends in vegetation dynamics under future climate change in western Asia.

Introduction

The area in west Asia that covers modern Turkey, the Caucasus and Iran is home to rich and highly diverse flora [START_REF] Mittermeier | Global biodiversity conservation: the critical role of hotspots[END_REF][START_REF] Frey | Flora and vegetation, including plant species and larger vegetation complexes in Persia[END_REF][START_REF] Zohary | Geobotanical foundations of the Middle East[END_REF]. The Iranian northwest, in particular, has attracted the attention of a number of investigators who pursue the history of human activities in the region [START_REF] Van Zeist | Palynological investigations in Western Iran[END_REF][START_REF] Bottema | A late Quaternary pollen diagram from Lake Urmia (northwestern Iran)[END_REF][START_REF] Klein | Les pozzines àCarex orbicularis Boott subsp. kotschyana del'Alborz central (Iran): groupement à la charnière des regions euro-siberienne et iranotouranienne[END_REF][START_REF] Djamali | A Late Holocen pollen record from Lake Almalou in NW Iran: evidence for changing land-use in relation to some historical events during the late 3700 years[END_REF][START_REF] Ponel | Fossil beetles as possible evidence for transhumance during the middle and late Holocene in the high mountains of Talysch (Talesh) in NW Iran[END_REF][START_REF] Ramezani | Long-term persistence of steppe vegetation in the highlands of Arasbaran protected area, northwestern Iran, as inferred from a pollen record[END_REF] and its floral diversity [START_REF] Zohary | Geobotanical foundations of the Middle East[END_REF][START_REF] Assadi | Noteworthy plant records for the flora of Iran[END_REF][START_REF] Ghahremaninejad | Floristic study of steppe parts of Lissar protected area (N Iran)[END_REF]. Understanding the relationship between climate, environmental and human factors that shaped the vegetation of the past is key to reconstructing the origin, history and trajectories of existing terrestrial ecosystems in this region [START_REF] Birks | Ecological palaeoecology and conservation biology: controversies, challenges, and compromises[END_REF][START_REF] Dearing | Climate-human-environment interactions: resolving our past[END_REF]. Multiproxy palaeoecological studies are particularly helpful in developing a comprehensive framework of the forces and responses that drive environmental transformations over extended periods of time (Zacharyet al., 2010).

Among terrestrial environments, peatlands have shown great potential to preserve high-resolution archives of changes in palaeoecological conditions. They have been used to reconstruct abrupt changes in climatic and environmental conditions during the late Quaternary, particularly the Holocene, as well as the cultivation and later fruit tree cultivation, e.g. Prunus, Juglans and Olea, was common around the highlands of the lake in the Talysh Mountains [START_REF] Ponel | Fossil beetles as possible evidence for transhumance during the middle and late Holocene in the high mountains of Talysch (Talesh) in NW Iran[END_REF]. [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF] recovered a 7.5 m core from the southwestern peripheral peatland of Lake Neor, approximately 200 m to the east of the Neor B core (not shown in Fig. 1), and using a high-resolution multiproxy approach, they reconstructed the aeolian input and palaeoenvironmental conditions of the region for the past 13 000 years. The authors identified an abrupt transition from the Last Glacial to the Holocene followed by more favourable climatic conditions with increased moisture. The Early Holocene was a wet period during which brief periods of high atmospheric dust input had occurred around 8200-8000 and 7600-7400 cal a BP. The transition to the middle-late Holocene was found to coincide with the longer and more frequent dry periods, during which the northwestern region of Iran, including the Lake Neor area, experienced at least eight episodes of dry climate with high atmospheric dust content (see Fig. 5 in [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF]. over the Late Glacial and the Early Holocene, leading to an earlier establishment of forest vegetation in those areas [START_REF] Roberts | Vegetational, lake-level, and climatic history of the Near East and Southwest Asia[END_REF]. A more recent study further expanded the vegetation and climate history of northwestern Iran to include the last glacial and interglacial cycles (cf. [START_REF] Djamali | A late Pleistocene long pollen record from Lake Urmia, NW Iran[END_REF]. According to this study, a steppe of Artemisia and Poaceae, in which Chenopodiaceae also played a major role, prevailed in northwestern Iran during both the penultimate and last glaciations. The vegetation succession at the transition of Late Glacial to Early Holocene in the area is represented by Hippophaë rhamnoides, Ephedra, Betula, Pistacia and finally Juniperus and Quercus.

In addition to the record from Lake Urmia, a number of palaeoecological studies have been carried out in the Lake Neor basin in northwestern Iran. [START_REF] Ponel | Fossil beetles as possible evidence for transhumance during the middle and late Holocene in the high mountains of Talysch (Talesh) in NW Iran[END_REF] studied a 3 m long sedimentary core, covering the past 6500 years, from the northeastern corner of the lake for beetle assemblages of coprophilous and coprophagous species and pollen. These records that were also consistent with archaeological evidence showed that the early practice of cereal and Fabaceae The study of the aeolian input to Neor during the Holocene has also revealed a shift in dust sources due to the southward migration of the Westerlies from the Younger Dryas to the Early Holocene [START_REF] Sharifi | Early-Holocene greening of the Afro-Asian dust belt changed sources of mineral dust in West Asia[END_REF]. In order to investigate the aeolian effects on the deposition of high-altitude lacustrine basins in western Asia, [START_REF] Kazancı | Aeolian control on the deposition of high altitude lacustrine basins in the Middle East: The case of Lake Neor, NW Iran[END_REF] used modern meteorological records and showed that the sedimentation of Lake Neor was affected by dust storms leading to a considerable amount of deposition of airborne particles. [START_REF] Aubert | Late glacial and early Holocene hydroclimate variability in northwest Iran (Talesh Mountains) inferred from chironomid and pollen analysis[END_REF] also reconstructed the palaeohydrological and climatic history of Lake Neor from the end of the Late Glacial to the Middle Holocene (15 500-7500 cal a BP), identifying four main hydrological phases using subfossil chironomid and pollen assemblages from a core collected from the south of the lake.

The studies summarised above have examined the hydroclimatic changes and human activities at the end of the Late Glacial to the Early Holocene based on geochemical proxies, chironomid and pollen assemblages. A similar multiproxy hydroclimatic reconstruction is, however, missing for the Middle to Late Holocene of northwestern Iran. The aim of the present study is to build on prior investigations by looking at the potential influence of climatic fluctuations on vegetation in the highlands of northwestern Iran. We present a pollen record from the southern part of the lake to investigate human activities and vegetation changes based on the combined interpretation of pollen and geochemical-based results over the past 7000 years.

Study area

Neor (37°55′-38°01′ N, 48°34′-48°36′ E; ~2500 m a.s.l.) is a seasonally recharged freshwater lake in the Talysh (Talesh) Mountains in the western extension of the Alborz (Elborz) orogenic belt in northwestern Iran (Fig. 1). Lake Neor is the largest lacustrine basin in the high mountains of the Middle East [START_REF] Kazancı | Aeolian control on the deposition of high altitude lacustrine basins in the Middle East: The case of Lake Neor, NW Iran[END_REF]. It is situated about 10 km to the west of the deciduous broadleaved Hyrcanian forest in a tectonic basin that formed during the Eocene due to the interaction of the Neor Fault and another fault in the western wing of the lake [START_REF] Madadi | Study of the geomorphological evolution of the Neor Lake in Ardabil region, NW Iran[END_REF]. The lake surface area varies seasonally between 2.1 and 2.4 km 2 [START_REF] Madadi | Study of the geomorphological evolution of the Neor Lake in Ardabil region, NW Iran[END_REF]. The southern and southwestern banks of the lake consist of a peripheral peatland with an estimated surface area of 1.5-2 km 2 .

The primary moisture sources of the Lake Neor basin are systems that originate from the Mediterranean Sea and the Black Sea. Precipitation mainly occurs during the winter season through westerly storm tracks as part of the mid-latitude westerlies [START_REF] Schiemann | Seasonality and interannual variability of the westerly jet in the Tibetan Plateau region[END_REF][START_REF] Nagashima | Millennial-scale oscillations of the westerly jet path during the last glacial period[END_REF]. Based on recent bioclimatic classification for Iran [START_REF] Djamali | Application of the Global Bioclimatic Classification to Iran: implications for understanding the modern vegetation and biogeography[END_REF], the climate of the area is Mediterranean continental. Climate data over a 23-year period from the Neor meteorological station indicates that the mean annual temperature and precipitation of Neor are 3.6 °C and 353 mm, respectively (Fig. 1b). The annual number of freezing days is 128. The dry season extends from June to October and the average temperatures of the hottest (August) and coldest (February) months are 16.5 and -10 °C, respectively. Lake Neor is strategically located in a region rife with diverse local microclimates due to drastic changes in elevation within relatively short distances. Physiognomically, Lake Neor is surrounded by mountain steppes, thorn-cushion plants, grasslands/meadows, cliffs and riparian vegetation types ranging in elevation between 1800 and 3200 m (see Fig. 1c). In terms of biogeography, the eastern area of the lake extends to the Hyrcanian forests in northern Iran, which is part of the Euro-Siberian phytogeographic region. The southern and western parts of the lake fall into the Irano-Turanian region [START_REF] Ghahremaninejad | Floristic study of steppe parts of Lissar protected area (N Iran)[END_REF][START_REF] Kh | A preliminary floristic study of Neor high altitude wetland, Ardebil province, NW Iran[END_REF][START_REF] Naqinezhad | Syntaxonomy and biogeography of the Irano-Turanian mires and springs[END_REF]. Asteraceae, Poaceae, Brassicaceae, Fabaceae, Rosaceae, Caryophyllaceae and Ranunculaceae are the richest families of vascular plants of Lake Neor's steppes and surrounding ecosystems [START_REF] Ghahremaninejad | Floristic study of steppe parts of Lissar protected area (N Iran)[END_REF]. The littoral wetlands surrounding the lake host an array of rare and protected vascular plants such as Sparganium emersum, Sparganium natans, Ranunculus peltatus and Utricularia minor. Figure 2 illustrates some of the main vegetation communities of the southern part of the lake during the growing season of spring and summer.

Materials and methods

Coring

An 8 m long core (Neor B; see Fig. 1b,c) was recovered during a lake lowstand in September 2008 using a Russian split-borer from the southwestern part of the wetland at 38°01′ N and was irradiated for 20 s (for 10 kV and 30 kV passes) and 30 s (for 50 kV pass) of integration time at 5 mm intervals using a window 5 mm high by 12 mm wide. The Canberra WinAxil software with standard software settings and spectrum-fit models were used to process the raw XRF spectra. The elemental abundances are reported as the intensity of each element in counts per second (cps). The data were calibrated using runs of a JR-1 standard (Geological Survey of Japan) before and after each analysis session.

Total organic content

The total organic content (TOC) data are cited from [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF]. In short, 400 subsamples were analysed along the 7.5 m core. Inorganic carbon was removed from homogenised samples by acidification using 10% HCl according to the procedure described by [START_REF] Hedges | Carbon and nitrogen determinations of carbonate containing solids[END_REF]. Between 2 and 15 mg of pretreated sample was transferred into precleaned tin cups and total organic carbon was measured with a Thermo Scientific Flash 2000 CHN analyser at the Virginia Institute of Marine Science (VIMS).

Results

Lithostratigraphy and 14 C chronology

The core segments appeared homogeneously composed of organic sediment with occasional variations in texture. The core consisted of dark gyttja at the bottom section, a mixture of dark gyttja and peat in the middle section between 2 and 3.75 m, and fine peaty material in the uppermost 2 m (Fig. 3). No mineral fraction was visible with the naked eye along the core.

The age model for the core in this study, based on the calibrations described above, is presented in Fig. 3 and encompasses the Middle Holocene (ca. 6700 yr cal BP) to Late Holocene (Table 1).

The accumulation rate calculated based on the same age-depth model ranged between 1.2 and 1.7 mm/a.

Inorganic proxy record

Down-core abundances of refractory conservative elements (Ti, Al), mobile elements (Ba), and redox-sensitive elements 48°34′23″ E. The sediment was described by visual inspection and under stereomicroscope. The lower 3 m of the core were analysed and published by [START_REF] Aubert | Late glacial and early Holocene hydroclimate variability in northwest Iran (Talesh Mountains) inferred from chironomid and pollen analysis[END_REF]. Here we focus on the upper 5 m of the core.

Chronology

The chronology of the core is based on five accelerator mass spectrometry radiocarbon ages. Samples containing organic matter were processed at the Poznań Radiocarbon Laboratory for age determination. The radiocarbon ages were calibrated with Intcal13 calibration curve [START_REF] Reimer | IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP[END_REF] using the Clam package [START_REF] Blaauw | Methods and code for 'classical' age-modelling of radiocarbon sequences[END_REF] included in R version 3.0.1 (R Core Team 2012) at two standard deviations.

Palynology

Twenty-one subsamples were collected at 20 cm intervals along the core at the Institut Méditerranéen de Biodiversité et d'Ecologie (IMBE). Palynological sample preparation followed the standard method suggested by [START_REF] Faegri | Textbook of pollen analysis[END_REF], which includes treatment with sodium hydroxide (NaOH) followed by hydrochloric acid (HCl), sieving with 160 µ mesh, treatment with concentrated hydrofluoric acid (HF) and finally acetolysis. In order to calculate pollen concentrations (grains/g), Lycopodium tablets were added to the samples before processing [START_REF] Stockmarr | Tablets with spores used in absolute pollen analysis[END_REF]. A CX31 Olympus light microscope was used for pollen identification and counting at 400×, and for difficult pollen grains, 1000× magnification. Pollen and spores were identified and named (M): [START_REF] Moore | Pollen Analysis, Second Ed[END_REF], (B): Beug ( 2004) and (ZB): van Zeist and [START_REF] Van Zeist | Palynological investigations in Western Iran[END_REF] as well as the pollen reference slides of the Faculty of Natural Resources, Urmia University. Pollen diagrams were produced using Tilia software version 2.0.41 [START_REF] Grimm | TILIA Software[END_REF].

We refrain from using Amaranthaceae sensu APG IV [START_REF] Chase | An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV[END_REF] in this paper because of the paucity of Amaranthaceae sensu stricto in Irano-Turanian flora (cf. [START_REF] Dehghani | A pollen rainvegetation study along a 3600 m mountain-desert transect in the Irano-Turanian region; implications for the reliability of some pollen ratios as moisture indicators[END_REF].

We used the (Artemisia + Poaceae)/Chenopodiaceae ratio ((A + P)/C) as a moisture pollen index (cf. [START_REF] Shumilovskikh | Landscape evolution and agro-sylvo-pastoral activities on the Gorgan Plain (NE Iran) in the last 6000 years[END_REF].

Principal component analysis

To obtain information regarding similar pollen composition among different pollen zones, as well as to determine which pollen taxa exhibited similar reactions in a pollen percentage diagram, detrended correspondence analysis (DCA) and principal component analysis (PCA) were conducted using CANOCO 4.5 software based on the square-root-transformed pollen percentage data (calculated on the basis of the arboreal pollen (AP) + nonarboreal pollen (NAP) pollen sum; see Palynological data, below). The DCA showed that the pollen percentage data have a predominantly linear structure, resulting in the use of a linearbased PCA (ter Braak 1987). In the PCA, the data were speciescentred. Furthermore, the variables AP, NAP, (A + P)/C and charcoals were passively projected in the diagram.

XRF core scanning

The analytical procedures for measuring the relative abundances of elements in the peat core were similar to those described in [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF]. Briefly, down-core variations of the relative elemental abundances of Al-U were measured using an AVAATECH XRF core scanner in the Palaeoclimatology Lab in the Marine Geoscience Division, Rosenstiel School of Marine and Atmospheric Science (MGS-RSMAS). All core sections were scanned three times (10 kV, 1000 mA, no filter; (Fe, Mn, V and Mo) measured by XRF-scanning at an average resolution of ~7 years are presented in Table S1. A previous study by [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF] showed that the ombrotrophic nature of the peat has been sustained throughout the past 13 300 years. Considering the absence of any significant riverine input to this high-altitude peat mire, the authors suggested that the elevated intensities of lithogenic elements (e.g. Ti and Al) correspond to the deposition of atmospheric mineral dust over the study area. They also concluded that mineral dust particles have not been mobilised since deposition, based on the high correlation between the abundances of refractory conservative elements and both mobile and redox-sensitive elements. As suggested by [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF][START_REF] Sharifi | Early-Holocene greening of the Afro-Asian dust belt changed sources of mineral dust in West Asia[END_REF], we used down-core abundances of Ti as a proxy for dust input during the dry period (Fig. 7). Down-core variation in Ti (Fig. 7) shows at least three periods of prolonged high Ti abundances during 6300-5200 cal a BP, 4500-2900 cal a BP, and 1300-present. Elemental ratios such as Mo/V, Mn/Al, Mo/Al, Ba/Al and Fe/Al are widely used as palaeo-redox proxies to reconstruct fluctuations in lake levels [START_REF] Calvert | Elemental proxies for palaeoclimatic and palaeoceanographic variability in marine sediments: interpretation and application[END_REF][START_REF] Martinez-Ruiz | Paleoclimate and paleoceanography over the past 20,000 yr in the Mediterranean Sea Basins as indicated by sediment elemental proxies[END_REF][START_REF] Martínez-Ruiz | Millennial-to centennial-scale climate periodicities and forcing mechanisms in the westernmost Mediterranean for the past 20,000 yr[END_REF]. Higer Mo/V, Mn/Al, Mo/Al, Ba/Al and Fe/Al ratios are correlated with lower Ti abundances (Fig. 7).

Palynological data

The palynological data are presented in the following two forms:

i. percentage values relative to pollen sum, i.e. total count for AP and NAP types (excluding wetland types) (Fig. 4). ii. concentration values for a selection of taxa (Fig. 5).

Pollen assemblage zones (PAZs) were identified using CONISS cluster analysis [START_REF] Grimm | CONISS: a FORTRAN 77 program for stratigraphically constrained cluster analysis by the method of incremental sum of squares[END_REF]. On this basis, the pollen diagrams were divided into three zones and four subzones (Figs. 4 and5). In the following, we describe the distribution of the above PAZs separately as a function of time to show the terrestrial upland vegetation and local hydrological change.

PAZ NEOR-I (460-290 cm; 6710-4030 cal a BP) This zone may be split into two subzones based on CONISS cluster analysis, i.e. NEOR-Ia (460-420 cm; 6710-6150 cal a BP) and NEOR-Ib (420-290 cm; 6150-4030 cal a BP). The characteristic feature of the first subzone is rather high values of AP types, particularly Quercus, Fagus and Salix (Fig. 4). Other important, albeit less frequent pollen taxa include Betula, Celtis, Carpinustype, Ulmus and Ephedra distachya-type. Artemisia and Chenopodiaceae are the predominant pollen types across the studied record. Other mentionable NAP types are Cirsium, Thalictrum, Ranunculus and Caryophyllaceae. With values up to 8.4, the (A + P)/C ratio culminates in this subzone. Of wetland types, Cyperaceae is the main constituent. Less frequent aquatic types are Lemna minor, Callitriche stagnalis, Sparganium erectum and Lysimachia vulgaris.

The next subzone is mainly characterised by decreased AP types and an increase of Poaceae and Chenopodiaceae. (A + P)/C ranges between 1.5 and 4.6. Cyperaceae substantially increases and remains the most abundant wetland types throughout the record.

Concentration values of the main constituents of the record, Artemisia, Chenopodiaceae, Poaceae and Cyperaceae, show prominent peaks in NEOR-Ia (Fig. 5).

PAZ NEOR-II (290-150 cm; 4030-2215 cal a BP)

This zone was divided into two subzones, NEOR-IIa (290-230 cm; 4030-3150 cal a BP) and NEOR-IIb (230-150 cm; 3150-2215 cal a BP). The main features of the first subzone are the raised values of Chenopodiaceae (Fig. 4) and relatively low values of Artemisia and Poaceae ((A + P)/C ratios: 0.8-1.6), which are also observed in the pollen concentration diagram (Fig. 5).

The subzone NEOR-IIb is characterised by the predominance of Artemisia and Poaceae ((A + P)/C ratios: 3.3-4). Other notable features of this section of the record include a slight increase of Quercus, and the continuous, though low value, curves of Carpinus-type and Betula. We see substantial values of Artemisia, Chenopodiaceae, Poaceae and Cyperaceae at the beginning of the subzone in the concentration diagram. From this point up to the end of the record, the concentration values of all groups of pollen types decrease dramatically.

PAZ NEOR-III (150 cm to the core top; 2215 cal a BP to present)

With the exception of a small peak in the middle, the AP curve represents its lowest values throughout the record. Compared with the former zones, this section of the record shows the lowest diversity of AP taxa; Quercus, Fagus and Ephedra distachya-type to name a few. Artemisia and Poaceae decline relative to the previous subzone, whereas Chenopodiaceae produces a prominent peak in the lower half and remains the major constituent of the entire zone (Fig. 4). Another notable feature of this zone is the significant peak of Apiaceae in the lowermost spectrum, which is followed by a rise of Caryophyllaceae and, to a lesser extent, Fabaceae. Overall, NAP types diversify towards the upper spectra of this zone and of this group, Centaurea solstitialis and Plantago lanceolata types should be noted. The (A + P)/C ratios show values between 0.5 and 1.9, respectively; a notable decline relative to the previous zone. Another characteristic feature of this zone is the prominent peaks of microscopic charcoals in its lower half. Cyperaceae peaks at the beginning of the zone but gradually declines thereafter. Most other wetland pollen types disappear towards the surficial samples in this terminal zone. age-model differences between the current pollen dataset and the geochemical data from [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF]. This, however, does not impact our interpretation of both datasets on a millennial time scale.

Interpretation of the pollen ratios

In a steppe environment such as the Lake Neor basin, AP indicates long-distance transport, whereas non-arboreal pollen (NAP) must reflect the vegetation composition of the surrounding landscape (i.e. regional pollen deposition, Janssen 1973).

In the search for an appropriate bioclimatic index in such environmental conditions, the ecological characteristics of the main pollen types (respective plant taxa) are shown to be particularly helpful (El-Moslimany 1990).

The co-occurrence of Poaceae and Artemisia species in the modern steppes surrounding Lake Neor on one hand, and a more or less parallel trend in the frequencies of their corresponding pollen types in the fossil pollen record (Fig. 4) on the other, may point to their largely similar ecological requirements. Characterised by shallow root systems, grasses grow vigorously in climates with summer rainfall (El-Moslimany 1990). In addition, several orophytic Artemisia species, including A. haussknechtii, A. persica and A. austriaca, flourish in wetter localities in northwestern Iran [START_REF] Zavvar | Palynological analysis of the Late-Holocene vegetation and climate of Ganli-Gol wetland near Urmia, northwestern Iran[END_REF][START_REF] Ramezani | Long-term persistence of steppe vegetation in the highlands of Arasbaran protected area, northwestern Iran, as inferred from a pollen record[END_REF]. High pollen frequencies of Chenopodiaceae in pollen diagrams may stem from xeric, halophytic or even ruderal communities [START_REF] Dehghani | A pollen rainvegetation study along a 3600 m mountain-desert transect in the Irano-Turanian region; implications for the reliability of some pollen ratios as moisture indicators[END_REF]. As no halophytic chenopods occur in the area of Lake Neor [START_REF] Ghahremaninejad | Floristic study of steppe parts of Lissar protected area (N Iran)[END_REF][START_REF] Kh | A preliminary floristic study of Neor high altitude wetland, Ardebil province, NW Iran[END_REF], the high pollen proportion of Chenopodiaceae in our pollen record can arguably be interpreted as the prevalence of dry climatic conditions that may have coincided with anthropogenic disturbances. We conclude that the (A + P)/C ratio positively correlates with climatic condition (i.e. higher ratios correlate with wetter periods and vice versa).

The interval of 6710-6200 cal a BP

The relatively high diversity and abundances of AP types (Fig. 4), in particular of those attributable to Quercus, Fagus, Carpinus and Betula and, to a lesser extent, Alnus, Ulmus and Pterocarya,

Principal component analysis

Together, the first two principal components explained 43.9% of the variation in the pollen data (axis 1: 34%; axis 2: 9.9%). The first axis of the PCA indicates a humidity gradient with opposing variables in two sides of the diagram (Fig. 6). The second axis is well represented by such pollen types as Thalictrum and Cirsium along with a number of disturbance indicator pollen types, such as Centaurea solstitialis, Plantago lanceolata, Euphorbia, Solanum nigrum and Carpesium. Cyperaceae are important on both first and second axes (see Discussion).

Discussion

The climatic and/or anthropogenic factors that exerted control over vegetation and hydrological changes in the highlands of northwestern Iran since the Mid-Holocene can be better understood with a multiproxy approach using a combination of pollen and geochemical data. Redox-sensitive and mobile (Mo, Mn, V, Fe and Ba) elements in aquatic environments behave differently under oxic and suboxic-anoxic conditions and form soluble/insoluble species in the water column [START_REF] Th | Trace-element behavior and redox facies in core shales of Upper Pennsylvanian Kansas-type cyclothems[END_REF][START_REF] Calvert | Geochemistry of Recent Oxic and Anoxic Marine Sediments Implications for the Geological Record[END_REF]. The relative abundances of these elements compared with Al, which is primarily of terrigenous origin, [START_REF] Martinez-Ruiz | Paleoclimate and paleoceanography over the past 20,000 yr in the Mediterranean Sea Basins as indicated by sediment elemental proxies[END_REF][START_REF] Gámiz | Sea surface temperature variations in the western Mediterranean Sea over the last 20 kyr: a dual-organic proxy (UK'37 and LDI) approach[END_REF] can be used as a proxy for water availability or wet/dry conditions in lake settings such as Neor. Contrasting the geochemical proxies with variations in pollen assemblages that represent predominantly wet conditions to those that thrive under drier climate suggest four major phases in the evolution of the hydroenvironment and landscape of the Lake Neor area since the Mid-Holocene (Fig. 7). These phases are defined by visual comparison of the variations in all environmental proxies. Admittedly, the age model established based on 19 radiocarbon dates in [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF] and this study (calibrated based on five radiocarbon dates) on the same depth interval of two different core locations from Lake Neor show some discrepancies in the TOC, δD and carbon accumulation rate data due to differences in age models. We therefore recognise that the apparent lag between plant response to climate variability may in part be due to and Callitriche spp. (Fig. 4) suggest a higher water table in this marginal part of the lake during the Mid-Holocene. With a slight difference in timing, which, as discussed above, may be due to differences in the age model between the two cores, the geochemical proxy data show low abundances of Ti and relatively high ratios of Mo/V, Mn/Al and Mo/Al. These ratios correlated with high TOC percentages, more negative δD values and higer carbon accumulation rates from [START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF] (Fig. 7), all suggesting a rather wet period for this part of the record. The inferred wet period is supported by the PCA analysis, where the high values of AP, Artemisia, Poaceae and (A + P)/C on the left side of the diagram (Fig. 6) indicate a humid period for the subzone NEOR-Ia, which is further characterised by the occurrence of local aquatic taxa. Pollen records from the eastern Mediterranean [START_REF] Rossignol-Strick | Sea-land correlation of pollen records in the Eastern Mediterranean for the glacial-interglacial transitions: Biostratigraphy versus radiometric time-scale[END_REF][START_REF] Rossignol-Strick | The Holocene climatic optimum and pollen records of sapropel 1 in the eastern Mediterranean, 9000-6000 BP[END_REF] suggest that a wet period prevailed from 9000 to 6000 cal a BP. Speleothem δ 18 O during this period refer to their long-distance transport most likely from the Hyrcanian region, 10 km east of the lake. However, considering the pollen production and dispersal properties of the above taxa [START_REF] Djamali | A late Pleistocene long pollen record from Lake Urmia, NW Iran[END_REF][START_REF] Ramezani | Pollenvegetation relationships in the central Caspian (Hyrcanian) forests of northern Iran[END_REF], one may conclude that the forest stands comprising these trees were likely distributed closer to the Neor site than in modern times. At the same time, relatively high values of Salix pollen may be interpreted as the expansion of willows (Salix spp.) on the southern banks of Lake Neor or along a palaeo-gallery forest south of the lake. Potentially closer expansion of the Hyrcanian forests in this period may suggest a wetter-than-present climate for the Lake Neor basin and its surrounding areas. This argument is further supported by the low values of Chenopodiaceae and the high (A + P)/C ratio during this time (see Fig. 4). Furthermore, the relative abundances of pollen types attributable to aquatic plants such as Lemna minor, Sparganium spp. (e.g. S. erectum) Mn/Al, Ba/Al, Fe/Al, and an increase in TOC and carbon accumulation rates, as well as low values of Ti abundances (Fig. 7). The remarkable expansion of Cyperaceae and Poaceae (Fig. 4) may indicate the expansion of the peatland during this time interval. [START_REF] Robinson | A review of palaeoclimates and palaeoenvironments in the Levant and Eastern Mediterranean from 25,000 to 5000 years BP: setting the environmental background for the evolution of human civilisation[END_REF] proposed a Mid-Holocene wet phase around 5000 cal a BP in the Levant. Also, the study of sediment cores from the Dead Sea shore shows a short wet interval at 5100 cal a BP [START_REF] Migowski | Holocene climate variability and cultural evolution in the Near East from the Dead Sea sedimentary record[END_REF]. It is worth mentioning that the observed transition in regional vegetation (i.e. the rise of chenopods and decreased (A + P)/C ratio at the boundary of pollen zones NEOR-Ib and NEOR-IIa; see Fig. 4) took place some time between 4300 and 3800 cal a BP, a time interval known as the 4.2 ka event (Fig. ,7). This time interval is also marked by the rapid change in δD values, indicating a shift toward less negative values (drier conditions). Following a recent formal subdivision of the Holocene into Greenlandian, Northgrippian and Meghalayan stages/ages (cf. [START_REF] Walker | Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period): two new Global Boundary Stratotype Sections and Points (GSSPs) and three new stage/subseries[END_REF], the 4.2 ka event has been considered as "a time stratigraphic marker horizon for defining the base of the Meghalayan Stage/Age" [START_REF] Walker | Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period): two new Global Boundary Stratotype Sections and Points (GSSPs) and three new stage/subseries[END_REF]. In the midand low latitudes, this event is frequently associated with a marked aridification phase, referred to sometimes as the 4.2-3.9 ka BP megadrought [START_REF] Weiss | Global megadrought, societal collapse and resilience at 4.2-3.9 ka BP across the Mediterranean and west Asia[END_REF][START_REF] Walker | Formal subdivision of the Holocene series/epoch: a summary[END_REF]. The collapse of the Akkadian Empire in Mesopotamia and the Early Bronze Age settlements in Anatolia appear to relate to a shift toward a remarkable dry climate [START_REF] Cullen | Climate change and the collapse of the Akkadian empire: evidence from the deep sea[END_REF][START_REF] Weiss | Global megadrought, societal collapse and resilience at 4.2-3.9 ka BP across the Mediterranean and west Asia[END_REF]). However, no evidence for a severe drought has been detected for this time in the Lake Zeribar and Lake Mirabad records in western Iran [START_REF] Stevens | Timing of atmospheric precipitation in the Zagros Mountains inferred from a multi-proxy record from Lake Mirabad, Iran[END_REF], possibly due to the relatively low resolution of these studies.

The interval of 4030-3150 cal a BP

The low values of AP types and Artemisia, significant increase of Chenopodiaceae and substantial decrease of (A + P)/C ratios (Figs. 4,7) associated with the rise of Ti abundances and exceedingly low values of palaeo-redox proxies all confirm the values from the Soreq cave in Israel also revealed several short wet periods, 20 to 100 years long, from 6800 to 6100 cal a BP [START_REF] Bar-Matthews | Sea-land oxygen isotopic relationships from planktonic foraminifera and speleothems in the Eastern Mediterranean region and their implication for paleorainfall during interglacial intervals[END_REF][START_REF] Bar-Matthews | Mid-Holocene climate variations revealed by high-resolution speleothem records from Soreq Cave. Israel and their correlation with cultural changes[END_REF].

The interval of 6200-5200 cal a BP

This interval is characterised by decreased AP values and increased Chenopodiaceae along with lowered (A + P)/C ratios (Fig. 4). This is largely in line with the geochemical data (Fig. 7). With the exception of three distinctly low intervals, the Ti abundances remain at the highest levels observed during the entire record, whereas Mo/V, Mn/Al, Ba/Al and Mo/Al drop to near background levels along with a substantial decline in TOC percentages and carbon accumulation rates. The δDvaluesare also trending toward less negative values. Based on the PCA analysis, the values of NAP, charcoal particles and dry habitat indicators such as Ephedra distachya-type and Chenopodiaceae show high values on the left side of the first PCA axis (Fig. 6). The data accordingly suggest a relatively prolonged period of dry climatic conditions for this interval. We postulate that the higher percentages of Cyperaceae could correspond to a dry climate, where the resulting low lake level and exposure of marginal lands might have led to the expansion of sedge vegetation. With that said, based on the geochemical data, this dry period is expected to have been interrupted by three short wet periods, which correlates well with the eastern Mediterranean record from the Soreq cave [START_REF] Bar-Matthews | Mid-Holocene climate variations revealed by high-resolution speleothem records from Soreq Cave. Israel and their correlation with cultural changes[END_REF][START_REF] Sharifi | Abrupt climate variability since the last deglaciation based on a high-resolution, multiproxy peat record from NW Iran: The hand that rocked the Cradle of Civilization[END_REF]. A severe 600 year-long drought would have persisted in western Iran centred at around 5500 cal a BP according to [START_REF] Stevens | Timing of atmospheric precipitation in the Zagros Mountains inferred from a multi-proxy record from Lake Mirabad, Iran[END_REF], possibly correlating to the inferred dry period in the Lake Neor region.

Between 5200 and 4450 cal a BP The Lake Neor basin experienced wetter conditions based on a small rise in AP values, which was also accompanied by increased (A + P)/C ratios along with prominent peaks of prevalence of arid conditions for this period. This notion is supported by low values (2.3-3.0 g C m -2 a -1 ) of carbon accumulation rates during this time frame (Fig. 7). Based on decreased values of Quercus pollen along with increased values of δ 18 O, a rise in the Mg/Ca ratio and higher values of charcoal, [START_REF] Wick | Evidence of Lateglacial and Holocene climatic change and human impact in eastern Anatolia: high-resolution pollen, charcoal, isotopic and geochemical records from the laminated sediments of Lake Van, Turkey[END_REF] propose for eastern Turkey (the Lake Van area) increased aridity for the period 4000-2100 cal a BP. The authors, however, do not exclude the role of human impact. A cooling climate spanning the period 4000-3000 cal a BP in the Tsalka area (lower Javakheti, Georgia), could have resulted in a lowered timberline and the replacement of the oak savanna by a coniferous association of pine and fir [START_REF] Connor | Environment and society in the late prehistory of Southern Georgia, Caucasus. In Les cultures du Caucase (VIe-IIIe millénaires avant notre ère) e Leurs relations avec le Proche-Orient[END_REF].

The interval of 3150-2215 cal a BP This time period is characterised by significant values of Artemisia, a substantial decline in Chenopodiaceae and rather high values for (A + P)/C ratios in pollen percentage and concentration diagrams (Figs. 4,5). A notable decrease in aeolian input (Ti abundances) during the period 2900-2200 cal a BP, which was accompanied by increased palaeo-redox proxies and an increasing trend in the values of TOC% and carbon accumulation rates (Fig. 7; see also Fig. 3 which shows more organic/peat content) all suggest a rather wet period. In the Lake Maharlou basin, southwestern Iran, [START_REF] Brisset | Late Holocene hydrology of Lake Maharlou, southwest Iran. inferred from high-resolution sedimentological and geochemical analyses[END_REF] suggest for the period 3800-2000 cal a BP a relatively high terrigenous input into the lake interpreted as an overall positive hydrological balance, corresponding to higher river flow and lower water loss through evaporation. This time frame was similarly recorded as a wet period in Lake Tecer, central Turkey [START_REF] Kuzucuoğlu | Mid-to late-Holocene climate change in central Turkey: the Tecer Lake record[END_REF].

In contrast, most records from the eastern Mediterranean propose a dry climate for this interval (e.g. [START_REF] Roberts | The tempo of Holocene climatic change in the eastem Mediterranean region: new highresolution crater-lake sediment data from central Turkey[END_REF][START_REF] Roberts | Stable isotope records of Late Quaternary climate and hydrology from Mediterranean lakes: the ISOMED synthesis[END_REF][START_REF] Schilman | Global climate instability reflected by Eastern Mediterranean marine records during the late Holocene[END_REF][START_REF] Wick | Evidence of Lateglacial and Holocene climatic change and human impact in eastern Anatolia: high-resolution pollen, charcoal, isotopic and geochemical records from the laminated sediments of Lake Van, Turkey[END_REF][START_REF] Kaniewski | Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes[END_REF][START_REF] Ocakoğlu | A 2800-year multi-proxy sedimentary record of climate change from Lake Çubuk (Göynük, Bolu, NW Anatolia)[END_REF][START_REF] Ramezani | Long-term persistence of steppe vegetation in the highlands of Arasbaran protected area, northwestern Iran, as inferred from a pollen record[END_REF]. Nevertheless, palynological study from the southern Caucasus [START_REF] Messager | Late Quaternary record of the vegetation and catchment-related changes from Lake Paravani (Javakheti, South Caucasus)[END_REF] cf. Lake Paravani in Fig. 1a) reports a significant vegetation change between 3200 and 2000 cal a BP. This period corresponds to the decline of Abies and Pinus and the progressive expansion of Picea, a deforestation phase and expansion of steppe vegetation attributable to an arid climate and human impact. Details, therefore, remain unclear when comparing biological and geochemical datasets and require more in-depth comparison using closely comparable age models to resolve.

The interval of 2215 cal a BP to present

The past 2200 years are charactersied by declining values of Quercus pollen and the scarcity of most AP types; while Chenopodiaceae and Ephedra distachya-type reach their maximum values throughout the entire record (Fig. 4). Ephedra distachya-type pollen is considered as an indication of dry climatic conditions [START_REF] Prentice | Reconstructing biomes from palaeoecological data: a general method and its application to European pollen data at 0 and 6 ka[END_REF][START_REF] Wick | Evidence of Lateglacial and Holocene climatic change and human impact in eastern Anatolia: high-resolution pollen, charcoal, isotopic and geochemical records from the laminated sediments of Lake Van, Turkey[END_REF][START_REF] Zhao | Application and limitations of the Artemisia/Chenopodiaceae pollen ratio in arid and semi-arid China[END_REF][START_REF] Ramezani | Long-term persistence of steppe vegetation in the highlands of Arasbaran protected area, northwestern Iran, as inferred from a pollen record[END_REF]. This period coincides with rather frequent episodes of high Ti abundances, low values of palaeo-redox proxies, more fluctuations in δD values, carbon accumulation rates and TOC% (Fig. 7), suggesting the recurrence of a dry climate in the Neor Lake basin area as was also proposed for the Arasbaran highlands in northwestern Iran (see Fig. 8). [START_REF] Wick | Evidence of Lateglacial and Holocene climatic change and human impact in eastern Anatolia: high-resolution pollen, charcoal, isotopic and geochemical records from the laminated sediments of Lake Van, Turkey[END_REF] link the cold and arid conditions of eastern Anatolia over the period 2200-1500 cal a BP to low sun activity which could have increased the need for plant utilisation for energy and heat production. This may have driven the vegetation toward drought-tolerant species, which are among the secondary destructive elements (cf. [START_REF] Zohary | Geobotanical foundations of the Middle East[END_REF]. We may accordingly ascribe the prominent peaks of charcoal particles during 2200-1800 cal a BP to successive local fires, which were likely human-induced.

Reconstructing the Late Holocene vegetation and climate history of the area southwest of Lake Urmia [START_REF] Talebi | The Late-Holocene climate change, vegetation dynamics, lake level changes and anthropogenic impacts in Lake Urmia region, NW Iran[END_REF], relatively cold and arid conditions along with fluctuating lake water levels and development of steppe vegetation have been proposed for the period between 2500 and 1500 cal a BP. In a palynological study in the Arasbaran area, northwest of Ardabil Province (Fig. 1a), [START_REF] Ramezani | Long-term persistence of steppe vegetation in the highlands of Arasbaran protected area, northwestern Iran, as inferred from a pollen record[END_REF] reported the potential for a severe drought, with the regional prevalence of steppe-like vegetation for the period 1400-1020 cal a BP (see also Fig. 8). A dry period centred at around 1500 cal a BP is recorded from Lake Mirabad in western Iran [START_REF] Stevens | Timing of atmospheric precipitation in the Zagros Mountains inferred from a multi-proxy record from Lake Mirabad, Iran[END_REF]. A synchronous dry period has been proposed in studies from neighbouring regions. Studying sediments from the Aegean Sea, [START_REF] Ehrmann | Clay minerals in late glacial and Holocene sediments of the northern and southern Aegean Sea[END_REF] inferred a dry period lasting from 1700 to 1000 cal a BP for the north and south catchments of the sea. Also, palaeoclimate reconstruction studies in Anatolian lakes suggest centennial-scale dry climatic conditions for the period between 1800 and 1300 cal yr BP (see [START_REF] Ocakoğlu | A 2800-year multi-proxy sedimentary record of climate change from Lake Çubuk (Göynük, Bolu, NW Anatolia)[END_REF].

Towards the last few centuries, the Neor Lake pollen diagram shows the expansion of steppe and/or anthropogenic-type vegetation in the studied area, as one might have expected. This can be inferred from the relative increase of such pollen types as Ephedra distachya, Centaurea solstitialis and Plantago lanceolata (see Fig. 4). To reiterate, the second axis of the PCA is mostly represented by a number of disturbance pollen taxa such as Centaurea solstitialis type, Plantago lanceolata type, Euphorbia, Solanum nigrum, Cirsium and Carpesium, which could be attributed to azonal anthropogenic landscapes (see e.g. [START_REF] Zohary | Geobotanical foundations of the Middle East[END_REF]) rather than specific climatic conditions. [START_REF] Djamali | A Late Holocen pollen record from Lake Almalou in NW Iran: evidence for changing land-use in relation to some historical events during the late 3700 years[END_REF] postulate that Centaurea solstitialis-type pollen might indicate cereal cultivation and pollen of Plantago lanceolata-type can be considered as an indicator for grazing expansion in the highlands of northwestern Iran. Today, the vegetation around Lake Neor is under strong grazing activity as evidenced by the presence of many ruderal plants including different Rumex and Plantago species [START_REF] Ghahremaninejad | Floristic study of steppe parts of Lissar protected area (N Iran)[END_REF][START_REF] Kh | A preliminary floristic study of Neor high altitude wetland, Ardebil province, NW Iran[END_REF].

Today, the nomado-pastoral seasonal settlers spend their summer in the lake region and their activities have a large impact on the naturally growing vegetation. Similar nomadopastoral activities may have been practised for more than a millennium [START_REF] Ponel | Fossil beetles as possible evidence for transhumance during the middle and late Holocene in the high mountains of Talysch (Talesh) in NW Iran[END_REF], and were intensified after the arrival of Turkish nomadic people during the Middle Ages and contributed to the maintenance of an overgrazed open steppe landscape. Similarly, intensified human activities as the major driver of the establishment and maintenance of modern vegetation and land use changes has also been proposed for the Lake Urmia and Lake Almalou regions [START_REF] Djamali | A Late Holocen pollen record from Lake Almalou in NW Iran: evidence for changing land-use in relation to some historical events during the late 3700 years[END_REF][START_REF] Mokarizadeh | Palynological reconstruction of 1700 years vegetation dynamics in suburban Urmia, northwestern Iran: the role of climate and humans[END_REF][START_REF] Talebi | The Late-Holocene climate change, vegetation dynamics, lake level changes and anthropogenic impacts in Lake Urmia region, NW Iran[END_REF].

Conclusion

Palynological and geochemical data obtained from a peripheral peatland south of Lake Neor enabled reconstruction of local and regional vegetation history of this part of northwestern Iran under the influence of climate change and human activities over the past 7000 years. The Neor pollen record is overwhelmingly composed of pollen types attributable to Artemisia spp., Chenopodiaceae and Poaceae, a typical feature of Irano-Turanian montane steppes. Frequent rather wet (6710-6200 cal a BP;5400-4600 cal a BP; 3200-2200 cal a BP) and dry (5800-5400 cal a BP; 4030-3200 cal a BP; 2200 cal a BP to present) cycles were recorded over the past seven millennia. However, long-term human activity in the area can be deduced from the occurrence of anthropogenic pollen indicators such as Centaurea solstitialis-type and Plantago lanceolata-type and the Late Holocene prominent peaks of charcoals.

On the basis of the PCA analysis, climate change (from wet to dry conditions) seemed to be the main environmental gradient affecting vegetation composition in the area. However, the second important gradient as characterised by disturbance pollen types, was probably driven by climateindependent factors such as grazing, mowing and other types of land use. Overall, our pollen record indicates that over the past seven thousand years, despite a few wet periods, dry climatic conditions and Irano-Turanian steppe vegetation prevailed in the highlands of northwestern Iran. We find that the multiproxy approach we employed in this study, albeit not free from age-model caveats, provided a more comprehensive image of how plants responded to abrupt climate change. However, the role of anthropogenic influence on plant diversity in the Lake Neor basin area over the last two millennia remains far from being fully explored. The different nature of the proxies (biological versus physico-chemical) suggests that an accurate interpretation of these datasets

Figure 1 .

 1 Figure 1. Geographical location of Lake Neor in northwestern Iran showing the position of other sites discussed in the text (a, b) and a closer view of the study area with the main regional vegetation types (c). The core studied by Sharifi et al., 2015 (not shown) was retrived 200 meters away to the east of Neor B. The map was produced using Landsat 8 (2019) natural colour composite. [Color figure can be viewed at wileyonlinelibrary.com].

Figure 2 .

 2 Figure 2. The main vegetation communities in the marginal peatland of Lake Neor. Top left: aquatic vegetation at coring locaton; top right: extensive wet meadows surrounding the lake with large Carex tussocks; bottom left: grazing effects of local cattles in surrounding meadows of the lake; bottom right: a view of Lake Neor and its surrounding steppes. [Color figure can be viewed at wileyonlinelibrary.com].

Figure 3 .

 3 Figure3. Lithostratigraphy and age-depth model for the studied peat core from Lake Neor. The age-depth model was developed with the CLAM software (Blaauw 2010) using a smooth splineinterpolated method and the ''IntCal13'' 14C calibration curve[START_REF] Reimer | IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP[END_REF].[Color figure can be viewed at wileyonlinelibrary.com].

Figure 5 .

 5 Figure 5. Pollen concentration (grains/g per 100) diagram for Lake Neor. [Color figure can be viewed at wileyonlinelibrary.com].

Figure 7 .

 7 Figure 7. Palaeoecological data coordination: pollen and geochemical records of Lake Neor core. [Color figure can be viewed at wileyonlinelibrary.com].

Figure 8 .

 8 Figure 8. Tentative correlation between palynological spectra in Neor-B core (this study) and other pollen records from northwestern Iran.[Color figure can be viewed at wileyonlinelibrary.com].

Table 1 .

 1 Radiocarbon dates and calibrated ages for peat core from Lake Neor.

				Conventional 14 C age	Midpoint calibrated age (a BP) ± 2σ	Accumulation rate
	Laboratory code Depth (cm)	Material	(RCYBP)	error	(mm a -1 )
	Poz-SE-B-11	52.5	Peat bulk	920 ± 30	901 ± 66	1.7
	Poz-SE-B-10	152.5	Peat bulk	2285 ± 30	2186 ± 114	1.3
	Poz-SE-B-9	252.5	Peaty	3085 ± 30	3443.5 ± 105.5	1.2
			gyttja bulk
	Poz-SE-B-8	372.5	Peat bulk	4775 ± 35	5451.5 ± 91.5	1.7
	Poz-SE-B-7	472.5	Peat bulk	5990 ± 40	6519.5 ± 255.5	1.2

Figure 4. Pollen percentage diagram for the Neor site showing terrestrial (AP+NAP) and wetland types. The actual values are displayed in black silhouette curves with a 10-time exaggeration (depth bars). For better visualization, the (A+P)/C ratios are also exaggerated 10-times. [Color figure can be viewed at wileyonlinelibrary.com].

Acknowledgements. This study was partly funded by the French project ANR PALEO-PERSEPOLIS (ANR-14-CE35-0026-01). We wish to thank the Management of the Iranian National Institute for Oceanography and Atmospheric Sciences (INIOAS) and particularly Drs Hamid Alizadeh Lahijani and Abdolmajid Naderi-Beni for their support during the fieldwork. We are grateful to Dr Hadi Beygi (Urmia University), Dr Mateusz Płóciennik (Unversity of Lodz, Poland) and Taravat Talebi (University of Groningen) for contributing in the preparation of Figs. 1 and8. Drs Philippe Ponel, Majid Shah-Hosseini and Mr Assadollah Taheri are acknowledged for their assistance during the fieldwork. Dr Mahmoud Bidarlord (Watershed Management and Forests and Rangelands Research Department, AREEO, Rasht, Iran) is thanked for helpful discussions on the main vegetation communities of the study area and for useful comments on Fig. 1. The manuscript was greatly improved by comments from two anonymous reviewers, for which we are very grateful.

Data availability statement

All pollen data will be made available in European pollen database.

Supporting information

Additional supporting information can be found in the online version of this article.

Author contributions-Khadijeh Alinezhad: Fieldwork; pollen analysis; writing preliminary draft. Elias Ramezani: Research design; fieldwork; pollen analysis and interpretation; writing, review and editing (lead). Morteza Djamali: Research design; fieldwork; interpretation of pollen data; review and editing. Arash Sharifi: Geochemical analysis; writing, review and editing. Alireza Naqinezhad: Fieldwork; ordination analysis; writing, review and editing. Cyril Aubert: Age-depth model; review. Emmanuel Gandouin: Interpretation of ordination; review. Ali Pourmand: Geochemical analysis; review and editing.