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

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 locally-dispersed 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.