Long-term vegetation dynamics along altitudinal and longitudinal gradients in the Hyrcanian forest region (northern Iran) and the role of climate, sea level change, fire and anthropogenic impacts during the late Quaternary
Final Report Abstract
The Hyrcanian forest region in northern Iran, restricted by the Caspian Sea (CS) to the north and highlands of Alborz and Talysh Mountains to the south is a highly biodiverse region. The narrow forest belt constitutes the most important refugia and the last relicts of broad-leaved deciduous forests that covered the temperate zones of the northern hemisphere before the Quaternary. The Holocene vegetation and environmental history in this region is still little known. In this project we did for the first time transect studies in the Gilan Province. Palaeoecological investigations have been carried out at low-, mid-, and high-elevated areas as well as modern pollen rain studies. We applied multi-proxy studies (pollen, spores, charcoal, geochemical analysis, etc.) on different sediment cores and we did modern pollen rain studies on two altitudinal gradients. For modern pollen rain and vegetation studies from Hyrcanian lowland forests up to the slopes of the Alborz Mountains in Gilan Province we analysed pollen traps, which were installed for one year, and moss samples. Pollen analysis and DNA metabarcoding were applied to investigate the representation of the vegetation of the transects. The results showed that the different vegetation types are relatively well reflected in pollen rain. In total, 182 species from 57 families were identified by metabarcoding. The results derived from metabarcoding, of the rbcL and ITS2 loci, were more in line with the vegetation surveys around the samples than pollen grains identified by morphology, which reflect the more regional aspect of the vegetation. Three environmental records from the lowland suggest that late Holocene climatic fluctuations, changes in Caspian Sea level, but in particular the intensity of human activities are the most important factors controlling the dynamics of the northern Iranian coastal vegetation and wetlands during the last about 1500 years. The dominant alder swamps extension was different between coastal and inland sites during the past. The studies also indicate that the dynamics of the Hyrcanian lowland forests and local fire frequency were mainly co-dominated by human impacts and local climate conditions. Increased anthropogenic activities such as agriculture, constructions, and human-induced fires played an important role in the decline of the Hyrcanian forest. Due to the human activities by construction, the geochemical composition of the wetland deposits changed markedly. In the mid-elevated region (Annal Lake record, 700 m) between ca. 1690 and 1450 cal yr BP, occurred a mixed Hyrcanian forest with Alnus, Carpinus, Quercus, and Fagus, as well as patches of grassland areas. At ca. 1450 cal yr BP, the forest expanded and reduced the grassland areas until 65 cal yr BP. Different proxies indicate that humans were present in the studied area since the beginning of the recorded period. However, since 65 cal yr BP, here human impact increased markedly by deforestation and cattle grazing, and settlers probably changed from pastoralism to more farmers. In the high-elevated region (Punel record, 2284 m), the record started at 4300 cal yr BP with a wide variety of herbaceous plants and with the dominance of Poaceae. Arboreal plants increased slightly and suggest the expansion suggesting wetter conditions. After 1700 cal yr BP Poaceae decreased while Cichorioideae, Amaranthaceae, and Brassicaceae increased until 1000 cal yr BP. Cichorioideae reached its highest occurrence between 1700 to 1000 cal yr BP, reflecting drier conditions, an open landscape, and/or grazing activity. Although the forest showed an increasing trend between 4300-1700 cal yr BP, it decreased from 1700 to 1000 cal yr BP. Quercus and Fagus were markedly less frequent between ca. 1580 to 1000 cal yr BP. After 1000 cal yr BP, Poaceae became more frequent while Cichorioideae decreased. The forests re-expanded, and trees like Quercus, Fagus, and Carpinus betulus became more frequent in the forest. More substantial increase of Sordaria spores as well as Plantago lanceolata, suggest an increase of grazing for the last 1000 years. The other record (Kholash-Kouh Lake, 2000 m) showed for ca. 1176-1010 cal yr BP, a relatively high proportion of herbs. The forest mainly consist of Quercus, Juniperus, and Carpinus betulus. Since ca. 1100 cal yr BP, the reduction of the lower elevated forest was probably related to human settlements. The most abundant input of the macro-charcoal particles at the beginning of this period may indicate widespread fire on the local scale. Overall, the results provide new insight on the past vegetation, climate, fire and human impact in the western part of the Hyrcanian region and deliver background information for conservation and management of the Hyrcanian forest. The results are of high importance for Global Change issues, as well as nature conservation, forest and rangeland management, agriculture, archaeology and sustainable development.
Publications
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'Four millennia vegetational and environmental history of the NW Hyrcanian mountain region (North of Iran)'. 20th INQUA Congress 25th-31th July 2019 in Dublin, Ireland
Leila Homami Totmaj
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'Vegetation history of Hyrcanian forest and the climate dynamics in northern Iran'. 20th INQUA Congress 25th-31th July 2019 in Dublin, Ireland
Fang Gu
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2021. Four millennia of vegetation and environmental history above the Hyrcanian forest, northern Iran. Vegetation History and Archaeobotany, 30, 611-621
Homami Totmaj, L., Ramezani, E., Alizadeh, K., Behling, H.
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2021. Late Holocene Hyrcanian forest 1 and environmental dynamics in the mid elevated highland of the Alborz Mountains, northern Iran. Review of Palaeobotany and Palynology. 295
Homami Totmaj L., Alizadeh K., Giahchi P., Darvishi Khatooni J., Behling H.
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2021. Long-term persistence of steppe vegetation in the highlands of Arasbaran Protected Area, northwestern Iran as inferred from a pollen record. Palynology, 45, 15-26
Ramezani, E., Talebi, T., Alizadeh, K., Shirvany, A., Behnam Hamzeh’ee, B., Behling, H.
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2021. Vegetation Dynamics, Environmental Changes and Anthropogenic Impacts on the Coastal Hyrcanian Forests in Northern Iran. Journal of Coastal Research, 37, 611-619
Gu, F., Ramezani, E., Alizadeh, K., Behling, H.
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2022. Late Holocene paleoenvironmental changes inferred from multi-proxy studies of the Kholasht-Kouh Lake sediments in the Gilan mountains, northern Iran. Journal of Paleolimnology
Homami Totmaj L., Alizadeh K., Behling H.
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2022. Late Holocene vegetation and environmental changes of coastal wetlands in northern Iran: possible role of climate, human impact and Caspian Sea level fluctuations. 42 (5)
Gu, F., Alizadeh, K., Behling, H.
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2022. Long-term vegetation dynamics along altitudinal and longitudinal gradients in the Hyrcanian forest region (northern Iran) - The role of climate, fire and anthropogenic impacts during the late Quaternary. PhD dissertation, University of Göttingen
Homami Totmaj L.
