Modern surface pollen from three transects across the Southern Sonoran desert margin, Northwestern Mexico

Abstract

Surface pollen samples collected along three transects that cross the southern margin of the Sonoran Desert east of the Gulf of California reflect regional vegetation gradients but also show strong local variability, notably within the southern desert. Chenopodiaceae‐Amaranthaceae (Cheno‐Am) and Gramineae pollen dominate in tropical deciduous forest; Pinus and Quercus in temperate‐climate vegetation at high elevations; and Gramineae and High‐Spine Compositae in the central Sonoran Desert (>29° N). The ERA group (composed largely of Euphorbiaceae, Rutaceae, Anacardiaceae), Gramineae, Cheno‐Am, and High‐Spine Compositae pollen inter‐vary but dominate as a group in the southern desert; Cheno‐Am here may signal irrigated agriculture. Coastal sites differ from the above, with Cheno‐Am pollen strongly dominant in saline conditions.