Ancient DNA and multimethod dating confirm the late arrival of anatomically modern humans in southern China.

The expansion of anatomically modern humans (AMHs) from Africa around 65,000 to 45,000 y ago (ca. 65 to 45 ka) led to the establishment of present-day non-African populations. Some paleoanthropologists have argued that fossil discoveries from Huanglong, Zhiren, Luna, and Fuyan caves in southern China indicate one or more prior dispersals, perhaps as early as ca. 120 ka. We investigated the age of the human remains from three of these localities and two additional early AMH sites (Yangjiapo and Sanyou caves, Hubei) by combining ancient DNA (aDNA) analysis with a multimethod geological dating strategy. Although U-Th dating of capping flowstones suggested they lie within the range ca. 168 to 70 ka, analyses of aDNA and direct AMS 14C dating on human teeth from Fuyan and Yangjiapo caves showed they derive from the Holocene. OSL dating of sediments and AMS 14C analysis of mammal teeth and charcoal also demonstrated major discrepancies from the flowstone ages; the difference between them being an order of magnitude or more at most of these localities. Our work highlights the surprisingly complex depositional history recorded at these subtropical caves which involved one or more episodes of erosion and redeposition or intrusion as recently as the late Holocene. In light of our findings, the first appearance datum for AMHs in southern China should probably lie within the timeframe set by molecular data of ca. 50 to 45 ka.

[Growth response of Abies fargesii to climate in Shennongjia Mount of Hubei Province, Southeastern China].

A well-replicated Abies fargesii tree-ring width chronology in the Shennongjia Mount was developed to investigate its radial growth response to climate variables (e.g., monthly mean tempe- rature and total precipitation) and other growing season indicators (e.g., cumulative temperature, continuous days, initial and final dates). Correlation analyses showed that the tree-ring width was positively correlated to the mean temperatures of February, April and September, and negatively correlated to the total precipitation of September, prior September and prior December. The analyses between the chronology and other growing season parameters showed that tree growth responded positively to the cumulative temperature and continuous days of the growing season. The correlation was the highest when the growing season was defined as the days above the temperature threshold of 9.0 °C. Defined this way, the growing season typically started in late-May and ended in mid-September, lasting about 120 days. Correlation analyses were also conducted between the tree-ring growth and the initial and final dates of the growing season. Results showed that correlation was the highest for initial dates defined at 9.0 °C (with the coefficient of -0.25 and p-value close to 0.05), and for final dates defined at 9.3 °C (with the coefficient of 0.33 and p-value less than 0.05). All these results indicated that the sensitive temperature threshold for photosynthesis of A. fargesii was around 9.0 °C. The year 1978 marked an abrupt shift of climate in southeast China. We compared A. fargesii growth between pre-1978 and post-1978 periods. Results showed that as temperature rose, the growing season was lengthened with both earlier initial dates and later final dates. Longer growing season increased the A. fargesii growth in the Shennongjia Mount, southeastern China.

[High altitude Pinus taiwanensis Hayata growth response to climate in Jiulongshan and Guniujian, Southeastern China].

Two robust Pinus taiwanensis Hayata tree-ring width chronologies were developed at high elevation sites in Jiulongshan Natural Conservation Area (JLS01), southeastern Zhejiang Province and Guniujiang (GNJ01), southern Anhui Province, China. The reliable period was 1884-2010 for JLS01 and 1837-2008 for GNJ01, based on subsample signal strength (SSS) threshold value of 0.8. Meteorological data were monthly mean temperature, monthly total precipitation and monthly mean relative humidity, monthly total cloud cover, as well as monthly sunshine duration. The data from the meteorological stations around the sampling sites were averaged to represent regional climate, which were used in the correlation analyses with the tree-ring chronologies. The correlation analyses indicated that summer (prior June-July and current June) hydrothermal condition was the main limiting factor on radial tree growth at the two high elevation sites. For JLS01 chronology, significant positive correlations were found with prior June-July temperature and sunshine duration, significant negative correlations with prior June-July and current June precipitation and relative hu- midity, and total cloud cover of prior July. GNJ01 chronology was significantly positively correlated with prior July temperature as well as prior July and current June sunshine duration, negatively correlated with prior July and current June precipitation and relative humidity, as well as total cloud cover of prior June. These results showed that relatively high temperature could promote radial growth, whereas high precipitation, together with high relative humidity, high cloud cover and low sunshine duration, could limit the photosynthesis and thus restrain the radial tree growth.