Large-scale dataset from China gives new insights into leaf margin–temperature relationships

Leaf margin analysis (LMA) is an important method of estimating paleotemperatures from fossil leaf floras or modern floras. Although some calibration has been carried out based upon large-scale studies of modern forests, most of this research has been in North America and Europe, with relatively little calibration work in East Asia. In the present study, we used species range maps of 3116 native dicot trees of China to derive synthetic local floras for each county from the Chinese humid region, and compared the percentage of untoothed leaf margined species with several temperature and precipitation related parameters. The results confirm the generally strong relationship between the proportion of species with untoothed leaf margins and climatic parameters within China. Leaf habit (deciduous vs. evergreen) does not strongly affect this relationship. The transfer function obtained from China, while not identical, is similar to those obtained from other regions, and is affected by regional restrictions, such as complex topography and relic taxa. As such it clarifies the potential range of error inherent in the LMA method as applied to paleoclimate reconstruction. It is possible, however, that with the close similarity of the modern Chinese tree floras to Neogene floras in the Northern Hemisphere, the present estimate offers a better transfer function for reconstructing the Neogene paleoclimate in various regions without extremely cold conditions across the Northern Hemisphere.