Palynological reconstruction of late-Holocene vegetation, climate, and human impact in Kelardasht (Mazandaran province, N Iran)

This study reconstructs 850 years of vegetation dynamics, climate change, and human impact in Kelardasht (Mazandaran province, N Iran), based on a palynological study of Tepe Kelar mire (1080 m asl; N 36˚ 31′ 17′′; E 51˚ 11′ 57′′). The pollen record of Tepe Kelar shows substantial changes in vegetation as a function of human impact and climate. In the last millennium beech (Fagus), hornbeam (Carpinus), and oak (Quercus) have been the most abundant tree species in the forests surrounding the Kelardasht plain; however, due to increased human interference, oak has severely declined over the past 1-2 centuries. Maple (Acer), ash (Fraxinus), and elm (Ulmus) may have been accompanying tree species on the slopes facing Kelardasht. Our study indicates that alder (Alnus) and wingnut (Pterocarya) once were abundant on the plain, but that human-induced hydrological change, particularly drainage of wetlands, has decimated alder and eliminated wingnut. The dramatic decline of wingnut at around 700-800 BP has also been found in other palynological studies from the central Hyrcanian forests and from Colchis in western Georgia. Being synchronous with the so-called Mediaeval Climatic Anomaly, a regional climate change could also have been responsible for this phenomenon. The occurrence of several pollen types indicative of human presence, such as Juglans regia and Avena triticum, may point to human habitation in the area at least since 850 years ago. Substantially higher values of Sambucus ebulus, Polygonum aviculare, and Plantago lanceolata indicate intensified anthropogenic vegetation change and land use over the past 300-400 years.