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.