Climatic reconstruction at the Miocene Shanwang basin, China, using leaf margin analysis, CLAMP, coexistence approach, and overlapping distribution analysis.

The reconstruction of the climate in the Miocene Shanwang basin is an important link in understanding past climate and environmental changes in East Asia. A recent study showed that the mean annual temperature (MAT) estimates derived from leaf margin analysis (LMA) and the Climate Leaf Analysis Multivariate Program (CLAMP) conflicted with and were remarkably lower than those estimated by the coexistence approach (CA). Overlapping distribution analysis (ODA), a new method introduced here, is used to reconstruct the Shanwang Miocene climate based explicitly on local plant distribution data and associated meteorological stations. The Shanwang flora (17-15.2 Ma) suggests a MAT of 10.9-14.5°C and a mean annual precipitation (MAP) of 1107.3-1880.0 mm. This result is closer to the values derived from CLAMP and LMA than that obtained by CA. This report is the first comprehensive intercomparison of foliar physiognomic and nearest living relative climate proxies in a Chinese context and provides important cross validation of results.

Eucommia (Eucommiaceae), a potential biothermometer for the reconstruction of paleoenvironments.

The living trees of Eucommia ulmoides, an endemic species in China, grow from 200 to 1700 m above sea level, within the geographic range from 102° E to 118° E and from 25° N to 35° N. Spring temperatures in these regions vary from 12.3°C to 20.1°C. A physiological study (using germination tests) of E. ulmoides has been undertaken to test the role of spring temperature as a factor controlling the distribution of Eucommia. Results show that the spring temperature is a limiting factor for Eucommia seed germination and hence for the distribution pattern of the genus. The suitable range of temperature for seed germination, established experimentally, is from 13°C to 22°C, with an optimum of 18°C. Specimens of fossil Eucommia cf. ulmoides, preserved as a branch segment and leaves, showing the distinctive latex, were found in Middle Miocene sediments of Shanwang Formation, Shandong Province, East China. If the climatic tolerances documented here for E. ulmoides are extrapolated to Shanwang, they are in fact consistent with other predictions of the paleoclimate at this site, indicative of the potential value of Eucommia as a biothermometer. These Miocene fossils, and one previously described Eocene fruit specimen, prove the former existence of Eucommia in China in addition to North America and Europe. This confirms that the genus is not a recent arrival in China and extends our understanding of the past biogeography of the genus.