Pollen signal of modern vegetation registered in surface soil samples along an elevation gradient from Iztaccíhuatl volcano, central Mexico

Vegetation History and Archaeobotany https://doi.org/10.1007/s00334-024-01007-6 ORIGINAL ARTICLE Pollen signal of modern vegetation registered in surface soil samples along an elevation gradient from Iztaccíhuatl volcano, central Mexico Erandi Rodríguez-Pérez1 · Lorenzo Vázquez Selem2 · Núria Cañellas-Boltà1 Susana Sosa3 · Socorro Lozano-García3 · Encarni Montoya1 · María del Carmen Trapote1 · Received: 9 April 2024 / Accepted: 26 June 2024 © The Author(s) 2024 Abstract Characterising the vegetation-pollen signal is a crucial task for enhancing the interpretation of fossil pollen records. This study analyses 28 surface soil samples collected in the surroundings of Iztaccíhuatl volcano, between 2,650 and 4,024 m asl. Pollen zones and ordination analysis were assessed to establish a qualitative connection between the pollen signal and the distribution of plant communities along the elevation gradient. The results show: (i) the predominant pollen type in the pollen assemblage is Pinus; (ii) pollen grains of Quercus and Alnus are present along the elevation gradient, even at high elevations where the parental plants are not typically found; (iii) samples taken between 2,650 and 3,338 m asl., where fir forests dominate, exhibit higher values of Abies pollen compared to samples above 3,405 m asl.; (iv) the locallydispersed pollen of the hemiparasite Arceuthobium results key in identifying the presence of pine forests; and (v) pollen taxa such as Apiaceae, Eryngium, Valerianaceae, and Caryophyllaceae are linked to higher elevations, specifically where the plant communities of Pinus hartwegii and alpine grassland occur. The study suggests that the pollen signal along the elevation gradient is useful to characterise the main plant communities of the study site (fir forest, pine forest and alpine grassland). Additionally, the percentage variations of Abies in the pollen signal below 3,600 m asl. show the reduction of fir forest communities resulting from recent human activities in the area. Keywords Iztaccíhuatl-Popocatépetl National Park · Modern analogues · Plant communities · Pollen assemblages · Trans Mexican Volcanic Belt · Tropical mountain Introduction Modern vegetation-pollen signal studies have long been acknowledged as essential for accurately interpreting fossil pollen records (Birks and Birks 1980; Ortega-Rosas et Communicated by W. Gosling. Encarni Montoya Erandi Rodríguez-Pérez 1 Geosciences Barcelona (GEO3BCN), CSIC, Barcelona, Spain 2 Instituto de Geografía, Universidad Nacional Autónoma de México, Mexico City, Mexico 3 Instituto de Geología, Universidad Nacional Autónoma de México, Mexico City, Mexico al. 2008). This understanding helps to infer historical environmental and biotic trends, providing insights to anticipate biotic responses to, for instance, a future greenhouse world (Jackson and Williams 2004). Research has documented a strong connection between the pollen signal and different plant communities, the presence of the parental taxa and/or changes in functional composition (e.g. Gosling et al. 2005; Lu et al. 2008; Niemann et al. 2010; van der Sande et al. 2021; Basumatary et al. 2024). Modern vegetation-pollen signal studies have also registered human impact on vegetation and land use (Franco-Gaviria et al. 2018; JiménezZamora et al. 2024; Shi et al. 2024). However, the relationship between vegetation and pollen is affected by (i) variability of pollen production between different taxa and from year to year, pollination syndromes, and dispersion capabilities (Bush 1991; Bush and Rivera 1998; Gosling et al. 2009); (ii) deposition and type of analysed samples (Zhang et al. 2020; Fang et al. 2022); and (iii) the landform and elevation of the study sites (Ortega-Rosas 13 Vegetation History and Archaeobotany et al. 2008; Castro-López et al. 2021). Therefore, considering these factors of variability in the pollen-vegetation relationships, it is advisable to expand the knowledge worldwide, in order to understand the particularities of each study region. So far, the modern vegetation-pollen signal research has been especially focused on high latitudes (e.g. Minckley et al. 2008; Mishra et al. 2022; Boutahar et al. 2023); however, the Neotropical regions have been patchily covered compared to temperate zones to date. Particularly in Mexico, several studies have examined the vegetationpollen signal. The first studies focused on using modern pollen signal to enhance palaeoenvironmental reconstructions in specific regions of interest. Notable examples include research in the southeast of Mexico (Islebe et al. 2001; Franco-Gaviria et al. 2018), the central region (Ohngemach and Straka 1983; Correa-Metrio et al. 2012; Chang-Martínez and Domínguez-Vázquez 2013; Lozano García et al. 2014), and the northeast (Ortega-Rosas et al. 2008). In recent years, research has also focused on exploring the quantitative relationship between environmental gradients and the pollen signal (Correa-Metrio et al. 2011), the impact of altitude and climate on the distribution of vegetation in patchy landscapes (Castro-López et al. 2021), and in the context of landscape connectivity and plant diversity conservation (Domínguez-Vázquez et al. 2023). Within Mexico, the Trans Mexican Volcanic Belt (TMVB) is considered a region of high biodiversity and endemism (Myers et al. 2000; Villaseñor et al. 2006), as well as part of the transition between Neotropical and Nearctic regions (Morrone and Márquez 2001). Considering the biological importance of the region, several studies focusing on biodiversity evolution and late Quaternary trends have been carried out (e.g. Mastretta-Yanes et al. 2015; CaballeroRodríguez et al. 2017). Additionally, natural protected areas have been established in this region (Toledo 2005; Figueroa and Sánchez-Cordero 2008; Aguilar-Tomasini et al. 2020). Nevertheless, more information is required to understand the drivers that promote high diversity in the zone and create better conservation strategies. This research presents the analysis of pollen assemblages from surface soil samples collected around the Iztaccíhuatl volcano. These samples were obtained along an altitudinal transect spanning elevations from 2,650 to 4,024 m asl (hereafter referred to as m). The main aim is to analyse the pollen deposition in surface soil samples from the current plant communities. Specifically, this research focuses on: (i) Establishing a qualitative relationship between the pollen signal and the distribution of plant communities along the elevational gradient; (ii) identifying potential indicator taxa and/or taxonomic groups for reconstructing plant communities; (iii) assessing the influence of altitude as a determining factor on the pollen signal, and (iv) evaluating 13 if the effect of human activities on the plant communities is displayed on the pollen signal. Furthermore, this research will enhance future palaeoecological interpretations serving as a detailed (...truncated)