Text S6. Palynology analysis
Two hundred and forty-eight subsamples were taken for pollen analysis
from KHQ-14 at no more than 15 cm vertical increments. Samples were
prepared for pollen analysis using standard preparation techniques
including alkali digestion, hydrofluoric acid digestion and acetolysis
with the addition of a known quantity of Lycopodium spores and
enumerated using an OLYMPUS optical microscope at 400× magnification.
Two hundred and twenty-seven samples counted comprised in excess of 400
pollen grains. Cereal-like Poaceae pollen (potentially from rice, either
wild or cultivated) was distinguished on the basis of size (diameter
>37 µm). Quercus pollen was also differentiated into
deciduous and evergreen sources. NPPs were identified and expressed in
concentration form. Microscopic charcoal fragments were counted and
expressed as concentration and flux (number of grains
cm2 yr-1). Undifferentiable
chitinous linings of foraminifera enumerated. Terrestrial pollen data
were square root transformed prior to numerical zonation using the
CONISS module in Tilia, in the meantime, taking sedimentary facies into
account. Four zones were divided and the zone boundaries extended to
include charcoal and NPP data (Fig. S6).
A total of 127 pollen and spore types were enumerated, 80 to genus
level. The relative high abundance of Pinus and deciduousQuercus, in addition to a small number of aquatic herbs, fern and
algae, in zone KHQ-P1 (from -24.40 to -20.85 m OD), represent cool and
slightly wet climate and terrestrial environment. After then, arboreal
taxa predominated, notably Pinus and deciduous and evergreen
forms of Quercus , indicating the climate was warm and wet,
subtropical condition. Among the non-arboreal taxa, pollen from Poaceae
(≤37µm) and Typha, is most abundant. The herb and NPPs assemblage
during ca. 9,300–8,250 cal BP in zone KHQ-P2 (from -20.85 to
-6.50 m OD), mainly consisting Poaceae, Typha ,Concentricystes and Polypodiaceae, represents a freshwater fern
condition. The saline hydrologic condition appeared during ca.8,240–7,600 cal BP, incorporating upper zone KHQ-P2 and entire KHQ-P3
(from -6.50 to -2.65 m OD), being indicated by a rise concentration of
dinoflagellate cysts and foraminifera linings. A decrease pollen
concentration, in addition to the relatively high charcoal flux values
associated with KHQ-P3 may represent the clearance of vegetation,
involving the use of fire, by humans some distance from the coring site.
KHQ-P4 (from above -2.65 m OD, or post ca. 7600 cal BP) is
characterised by an initial recovery and then decline in Pinusand Quercus pollen, continued although strongly varying
abundances of small-sized Poaceae pollen and the remains ofSpiniferites, and increased levels of Artemisia and
Chenopodiaceae. Both of the latter likely represent the expansion of
saltmarsh locally. The continued presence of Typha throughout
KHQ-P4, suggest the influence, perhaps on an intermittent basis, of
shallow, freshwater conditions. Fluctuations of temperature and
precipitation during and after the occupation of Kuahuqiao, as revealed
by pollen data, did exist, but not to the extent that would have caused
fatal effects to human societies.