A scanning electron microscopy (SEM) study of sediments from Lake Cristol,southern French Alps, with special reference to the identification of Pinus cembra and other Alpine Pinus species based on SEM pollen morphology
T. Nakagawa et al., A scanning electron microscopy (SEM) study of sediments from Lake Cristol,southern French Alps, with special reference to the identification of Pinus cembra and other Alpine Pinus species based on SEM pollen morphology, REV PALAE P, 108(1-2), 2000, pp. 1-15
The scanning electron microscopy (SEM) pollen morphology of the major Alpin
e Pinus species was established, then the sediment cores from Lake Cristol
(2248 m a.s.l.), southern French Alps, were palynologically studied with th
e help of SEM. SEM was used in order to distinguish Pinus cembra pollen gra
ins from other Alpine Pinus species with higher reliability, and served to
reconstruct the Holocene vegetation history near the site with more accurac
y. Recent pollen grains of P. cembra, P. sylvestris, and P. uncinata were e
xamined by SEM in an attempt to establish the diagnostic characteristics of
P. cembra pollen. The cappa exine surface of P. cembra is smooth to slight
ly rugulate, whereas that of the other two species is verrucate to rugulate
and deeply sculptured. This difference in ornamentation is so significant
that it is possible to identify the fossil pollen grains of P. cembra with
SEM. Pollen analyses were carried out on the cores from Lake Cristol using
both light microscopy (LM) and SEM. Then both the macro remains in the core
s and the fossil trunks in the lake were C-14 dated. Pollen curves of P. ce
mbra obtained with LM and SEM showed considerably different trends. SEM res
ults explained the age distribution of the fossil trunks better than LM res
ults, showing the higher reliability of P. cembra identification by SEM. Th
e arrival of the species to the site is estimated around 5600 yr BP (late A
tlantic). Its abrupt disappearance is probably correlated with the deforest
ation around Roman times. Between those two epochs (from late Atlantic to e
arly Subatlantic), fluctuation of P. cembra in the vegetation around the si
te is represented by its curve in the pollen diagram and the age distributi
on of the fossil trunks. Comparison of the local history of P. cembra with
other nearby studied sites implies the SE to NW migration of the species du
ring its settlement into the Alpine region. (C) 2000 Elsevier Science B.V.
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