Holocene vegetation and climate changes inferred from pollen record of Nordenskiöld Land (West Spitsbergen Island)

Pollen analysis is one of the methods that allow revealing ecological and climatic changes in the
past based on vegetation reconstruction. Spitsbergen (Svalbard) archipelago, as well as other
regions of the Arctic, is difficult for creation of regional models of vegetation and climate
development during the Holocene. This is primarily due to the limited distribution, low thickness
and relative young ages (usually this is the late Holocene) of organogenic deposits, which are
most suitable for palynological studies.
Nordenskiöld Land is located in the central part of the West Spitsbergen Island and different the
most favorable climatic conditions. The largest number of sites suitable for paleobotanical
researches is located here. The Coles valley has length about 12 km, well-developed profile and
situated on the north shore of Nordenskiöld Land. The field campaign with studying of
floodplain peat sediments from Coles River valley was carried out in August 2018. Two sites
(K18-15, K18-16) were studied on the remains of first terrace. Excavated deposits are
represented by leafy peat of varying degrees of decomposition with silt lenses. The laboratory
studies of sediments included radiocarbon dating, pollen and non-pollen palynomorph analyses.
They were carried out in Laboratory of St-Petersburg State University and Russian chemical-
analytical Lab on the Spitsbergen archipelago.
The pollen analysis of two sections from Coles River valley allowed us to reconstruct
paleovegetation changes. Samples from K18-15 site contain more mineral components and more
pollen and spores than samples from K18-16 site. This is probably due to the inflow of pollen
with water. The main components of spore-pollen spectra are Poaceae, Cyperaceae, Salix and
Betula sect. Nanae. The relationship between these taxa shows a different degree of moisture of
the study area under the dominance of the grass - sedge tundra. Thus, a significant influence on
the formation of spores and pollen spectra in the studied deposits is played by the dynamics of
the sedimentation.
Results of radiocarbon dating showed that studied deposits formed during mid and late
Holocene.
A generalization of all available palynological data on the Nordenskjöld land made it possible to
construct a scheme of dwarf birch (Betula sect. Nanae) distribution during the Middle and Late
Holocene. A comparison of received data with our previous data and published data from
Nordenskiöld Land shows the asynchronous of appear and distribution of shrubs on these area
from ~5000 to ~2500 yrs ago.