https://doi.org/10.1177/0959683619838024 The Holocene 1–4 © The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0959683619838024 journals.sagepub.com/home/hol Introduction Pollen proportions, classically used to reconstruct past vegetation, are affected by inherent biases. In addition to the nonlinearity between pollen proportions and vegetation abundances, the pol- len–vegetation relationship is influenced by factors such as the size and type of sedimentary basins and inter-taxonomic differ- ences in pollen productivity and dispersal characteristics (Pren- tice, 1985; Sugita, 1994). Over the last few decades, advances in the theory of pollen analysis have helped overcome some of these fundamental issues. The nonlinearity issue was first dealt with the R-value model (Davis, 1963) and by the Extended R-Value (ERV) model (Parsons and Prentice, 1981; Prentice and Parsons, 1983; Sugita, 1994). Those models have led to more objective ways of estimation of relative pollen productivity of plants that are neces- sary for quantitative reconstruction of past vegetation (see synthe- sis of Broström et al., 2008 and Mazier et al., 2012). Sugita (2007a, 2007b) introduced the landscape reconstruction algo- rithm (LRA) – a theory-based approach for quantitative recon- struction of past vegetation and land cover using pollen records from lakes or bogs surrounded by continuous vegetation cover. The LRA consists of two models, REVEALS model (Regional Estimates of VEgetation Abundance from Large Sites) and LOVE (LOcal Vegetation Estimates), to quantify regional and local past vegetation abundance. By relaxing some of model assumptions, this study aims to show the applicability of REVEALS for recon- struction of windward vegetation along coastal areas using pollen records from lagoons. The REVEALS model aims to reconstruct vegetation compo- sition within 50–100 km radii using pollen records from large sites (100–500 ha). To convert raw pollen counts into regional vegetation abundance, REVEALS requires parameter inputs such as site size (radius) and type, fall speed of pollen, pollen produc- tivity estimates, and their standard errors. The model requires a pollen dispersal and deposition function to describe the amount of pollen remaining airborne at increasing distances from single point source. It assumes the wind above the canopy to be the main agent of pollen transport. Palynologists have used Sutton’s (1953) equation for atmospheric diffusion of small particles on a two- dimensional plane, released from a point source at ground level (Prentice, 1985; Tauber, 1965); it is a particular form of analytic Gaussian-plume model (Jackson and Lyford, 1999) for assessing diffusion in turbulent air within the planetary boundary layer (Sutton, 1947, 1953). The proposed models of pollen deposition using Sutton’s model are site-type-dependent. Prentice (1985) adapted Sutton’s model for pollen deposition on wetland (bogs and marshes); it estimates pollen deposition at the center of a sedimentary basin where the horizontal mixing after deposition is negligible. Sugita (1993) modified Prentice’s model later for pol- len deposition on the entire surface of a basin; this model is appro- priate for lakes, because it is assumed that redistribution of pollen occurs in lakes before sedimentation caused by water circulation and sediment focusing (e.g. Davis, 1973). Extending the applicability of the REVEALS model for pollen-based vegetation reconstructions to coastal lagoons Julien Azuara, 1 Florence Mazier, 2 Vincent Lebreton, 1 Shinya Sugita, 3 Nicolas Viovy 4 and Nathalie Combourieu-Nebout 1 Abstract Quantitative reconstruction of past plant abundance from fossil pollen data is still a challenging task for palynologists. During the last decades, mechanistic methods have been developed to convert pollen assemblages from peat and lake deposits into vegetation abundance at regional and local scale. Coastal areas are particularly sensitive to climate and environmental hazards. Thus, quantitative estimates of past vegetation are important to better understand their history and address potential effects of future environmental changes. However, assumptions of the mechanistic models of pollen dispersal and deposition originally designed for near-circular lakes and bogs located inland are violated when applied to coastal sites because of different basin shape and wind direction distribution. This study investigates how to adapt a model of pollen dispersal and deposition developed for lakes to coastal lagoons. A new geometry is defined, and it is demonstrated how some of the major formulas from previous models can be used without any modification in this singular context. Keywords coastal sites, demonstration, palynology, pollen data, REVEALS model, vegetation quantitative reconstruction Received 14 July 2018; revised manuscript accepted 1 February 2019 1 UMR 7194 CNRS, HNHP, Muséum national d’Histoire Naturelle, France 2 UMR 5602 CNRS, Géode, Université Jean Jaurès, France 3 Insitute of Ecology, Tallinn University, Estonia 4 UMR 8212 CNRS, IPSL-LSCE, France Corresponding author: Julien Azuara, UMR 7194 CNRS, HNHP, Muséum national d’Histoire Naturelle, 1 rue R Panhard, 75013 Paris, France. Email: julien.azuara@mnhn.fr 838024HOL 0 0 10.1177/0959683619838024The HoloceneAzuara et al. research-article 2019 Report