Four millennia of vegetation and environmental history above the Hyrcanian forest, northern Iran
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ORIGINAL ARTICLE
Four millennia of vegetation and environmental history above the Hyrcanian forest, northern Iran Leila Homami Totmaj1 · Elias Ramezani2 · Kammaledin Alizadeh1 · Hermann Behling1 Received: 15 January 2020 / Accepted: 9 November 2020 © The Author(s) 2020
Abstract Past vegetation, fire, and climate dynamics, as well as human impact, have been reconstructed for the first time in the highlands of the Gilan province in the Alborz mountains (above the Hyrcanian forest) for the last 4,300 cal yrs bp. Multi-proxy analysis, including pollen, spores, non-pollen palynomorphs, charcoal, and geochemical analysis, has been applied to investigate the environmental changes at 2,280 m a.s.l., above the Hyrcanian forest. Dominant steppe vegetation occurred in the study area throughout the recorded period. The formation of the studied mire deposits, as well as vegetation composition, suggest a change to wetter climatic conditions after 4,300 until 1,700 cal yrs bp. Fires were frequent, which may imply longlasting anthropogenic activities in the area. Less vegetation cover with a marked decrease of the Moisture Index (MI) suggests drier conditions between 1,700 and 1,000 cal yrs bp. A high proportion of Cichorioideae and Amaranthaceae, as well as the reduction of trees, in particular Fagus and Quercus, at lower elevations, indicate human activities such as intense livestock grazing and deforestation. Soil erosion as the result of less vegetation due to dry conditions and/or human activities can be reconstructed from a marked increase of Glomus spores and high values of K and Ti. Since 1,000 cal yrs bp, the increasing MI, as well as the rise of Poaceae and Cyperaceae together with forest recovery, suggest a change to wetter conditions. The occurrence of still frequent Cichorioideae and Plantago lanceolata along with Sordaria reflect continued intense grazing of livestock by humans. Keywords Late Holocene · Northern Iran · Multi-proxy studies · Hyrcanian mountain vegetation · Climate change · Human impact
Introduction Between the northern slopes of the Alborz Mountains and the southern coast of the Caspian Sea (CS) is a narrow belt, 20–70 km wide and ca. 800 km long, which is covered by broad-leaved deciduous Hyrcanian forest. It extends from the lowland up to > 2,000 m a.s.l. (Sabeti 1994; Sagheb-Talebi et al. 2014). However, above 2,000 m, the forests are mostly Communicated by T. Litt. * Leila Homami Totmaj leila.homami‑totmaj@uni‑goettingen.de 1
Department of Palynology and Climate Dynamics, Albrecht‑Von‑Haller Institute for Plant Sciences, University of Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany
Department of Forestry, Faculty of Natural Resources, Urmia University, Sero Boulevard, Nazloo, P.O. Box: 165, Urmia, Iran
2
replaced by forest/steppe or steppe vegetation. The area covers approximately 1.9 million ha and consists of three provinces from west to east, namely Gilan, Mazandaran, and Golestan (Fig. 1 II). Some of the Arcto-Tertiary species occurred in the Hyrcanian forest. Pterocarya
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