DOI: 10.5061/dryad.tb2rbp05n
title: Data from: Amazonian pollen assemblages reflect biogeographic gradients and forest cover

description: Aim: We aim to assess i) how pollen assemblages vary across biogeographic
 and environmental gradients, ii) the source area of pollen assemblages
 from lake sediment samples, and iii) which pollen taxa can best be used to
 quantify deforested landscapes. Location: Amazonia Taxon: Plantae Methods:
 Pollen assemblages (N = 65) from mud-water interface samples (representing
 modern conditions) of lake sediment cores were analysed and compared with
 modern gradients of temperature, precipitation, and elevation. Pollen
 assemblages were also compared with local scale estimates of forest cover
 at 1, 2, 5, 10, 20, and 40 km buffers around each lake. Results: Over 250
 pollen types were identified in the samples, and pollen assemblages were
 able to accurately differentiate biographic regions across the basin,
 corresponding with gradients in temperature and precipitation. Poaceae
 percentages had a significant negative relationship with forest cover
 estimates, which were stronger at the 1 km buffer and weaker as buffer
 sizes increased. Main conclusions: The diverse Amazonian pollen
 assemblages strongly reflect environmental gradients, and percentages of
 Poaceae best reflect local scale variability in forest cover. Our results
 of modern pollen-landscape relationships can be used to provide a
 foundation for quantitative reconstructions of climate and deforestation
 in Amazonian landscapes.
description: A total of 65 sites located within Amazonia sensu stricto (Eva et
 al., 2005) were used in our analysis (Fig. 1, Table S1). Samples from new
 sites (n = 44) were collected with a Universal corer during 2018 and 2019
 (Table S1). Samples from previously published sites (n = 21) were
 collected with a Colinvaux-Vohnout piston corer or a Universal corer
 (Table S1) (Bush et al., 2020). Our sites were located within evergreen
 tropical rainforests (n = 56) and from savannas close to the ecotone with
 forests (n = 9) (Fig 1a). Thirty-three of the forested sites were situated
 within terra firme soils and 22 on floodplains (Table S1). The sites
 included permanent lakes, oxbow lakes, and flooded marshes in the
 Brazilian savannas (Table S1). From each of the 65
 sites, we collected the upper 1 cm of sediment (mud-water interface) for
 pollen analysis. Pollen samples were prepared in the Paleoecological
 Laboratory at the Institute for Biodiversity and Ecosystem Dynamics,
 University of Amsterdam, Netherlands or in the Neotropical Paleoecology
 Laboratory at Florida Institute of Technology, USA, and followed standard
 procedures as documented in Faegri and Iversen (1989). A total number of
 300 to 500 pollen grains were counted to generate a pollen assemblage for
 each sample, and tablets of <em>Lycopodium clavatum</em>
 spores were added prior to sample preparation to allow for calculations of
 pollen concentration (Stockmar, 1971). Pollen identification of the new
 samples was at a lower taxonomic resolution than the previously published
 samples, and data were harmonized (e.g., merged to a higher taxonomic
 resolution) prior to analysis (e.g., Bush et al., 2020).