Modern pollen rain–vegetation relationships along a forest–steppe transect in the Golestan National Park, NE Iran

Abstract

Pollen rain–vegetation relationships were studied over a forest–steppe transect in Golestan National Park, NE Iran. The surface pollen percentages were compared to the phytosociological composition of the respective vegetation types in 18 sampling points using both descriptive and numerical approaches. Hyrcanian lowland forests are characterized by pollen assemblages dominated by Quercus, Carpinus betulus and low amounts of Zelkova carpinifolia. Both Parrotia persica and Z. carpinifolia show a very low pollen representation in modern pollen samples, an under-representation that should be taken into account in the interpretation of fossil pollen diagrams. Transitional communities between the forest and steppe including Acer monspessulanum subsp. turcomanicum, Crataegus and Paliurus scrubs, Juniperus excelsa woodlands and shrub–steppe patches are more difficult to distinguish by pollen assemblages but are characterized by higher values of the dominant shrub species. The transitional communities at the immediate vicinity of the forest show also a substantial amount of grass pollen. Many insect-pollinated taxa are strongly under-represented in pollen rains including most of the rosaceous trees and shrubs, and Rhamnus, Paliurus, Acer and Berberis. Artemisia steppes are characterized by very high values of Artemisia pollen and the quasi-absence of tree pollen.