The genus Cedrus (the true cedar) (Pinaceae) is well known for its horticultural use. There are now only four living species in Cedrus. Even though extant Cedrus survives in China, it has a much narrower distribution range than in the past. A single species, C. deodara, grows naturally in China where it is restricted to a small area in extreme southwestern Tibet
Prof. Zhou Zhekun’s team of Xishuangbanna Tropical Botanical Garden (XTBG), together with their collaborators, described a new species, namely Cedrus angusta sp. nov. T. Su, Z. K. Zhou et Y. S. Liu, based on cone scales from the Upper Pliocene Sanying Formation of Yunnan Province in southwestern China, where it is outside the present distribution range of living Cedrus. They also discussed the shrinking distribution of Cedrus in response to the late Cenozoic change in climate.
Fossil specimens were uncovered from Longmen village, Yongping County, western Yunnan Province, southwestern China (25°30′48″ N, 99°31′11″ E). All the fossil specimens were collected over six fieldwork excursions between 2008 and 2010, and are deposited in the Paleobotany Laboratory of XTBG. Specimens of the living species of Cedrus were checked in Herbaria. Fossil pollen records of Cedrus from Yunnan were compiled from previous literature.
The researchers concluded that Cedrus disappeared from southwestern China because of the strength of the Asian winter monsoon during the Quaternary, which formed a much drier winter than the winter during the Neogene in southwestern China, and also drier than the winter in the distribution regions where living Cedrus exist. Because the seeds of Cedrus tend to germinate immediately when they mature in the autumn, the young seedlings of Cedrus would be unable to survive under such a prolonged dry period. Consequently, Cedrus disappeared in southwestern China.
The study indicated that the topography in southwestern China acted as a vital refuge for many plants during the Quaternary, but that other species gradually disappeared due to the intensification of the monsoonal climate.
The study entitled “The intensification of the East Asian winter monsoon contributed to the disappearance of Cedrus (Pinaceae) in southwestern China” has been published online in Quaternary Research.