In China, the floristic composition of subtropical mountain mixed evergreen and deciduous broad-leaved forests is characterized by its Tertiary relict element. The Shennongjia National Nature Reserve (31º21′20"–31º36′20" N, 110º03′05"–110º33′50" E) is an important part of south-central China biodiversity hot-spot and is rich of Tertiary relicts and endemic plants. Euptelea pleiospermum and Cercidiphyllum japonicum are dominant relict tree species of the riparian plant communities in the Shennongjia Mountains. Knowledge of the processes that determine population dynamics is of importance to conserve and manage the extant Tertiary relict forests.

Xinzeng Wei and Dong He, two researchers from Wuhan Botanical Garden, CAS, investigated the survival status and population dynamics of the two subtropical mountain riparian Tertiary relict tree species in the Shennongjia Mountains. This study covered several aspects, in particular seed germination, relationships between plant communities and environments, population structure, and regeneration characteristics. Seed germination experiment revealed that E. pleiospermum has elaborate mechanisms (i.e. non-deep dormancy, special requirement of substrate moisture content, and particular mechanism to detect gap or disturbance) to adapt to the mountain riparian habitats. Community survey and multivariate analysis demonstrated that Tertiary relict tree species arefavored by the mild and moist microclimate, but current conditions in subtropical mountain riparian habitats probably do not really provide optimal ecological conditions for them. Population census and growth ring analysis pointed out that prolific sprouting, which can compensate for the sporadic seedling recruitment, may prevent Tertiary relict tree species from expanding their geographical distribution ranges.

This work was supported by the National Natural Science Foundation of China (No. 30570331 and 30670368). Some of the results have been published in Seed Science and Technology, Flora, Chinese Journal of Plant Ecology, and Journal of Wuhan Botanical Research.