Effect of stand age and management regime on genetic diversity of Thuidium cymbifolium in western China

Using random amplified polymorphic DNA (RAPD) markers, we examined genetic variability of the moss Thuidium cymbifolium (Thuidiaceae) sampled from three types of spruce (Picea asperata) stands: an intact stand, naturally regenerated stands after clearcut harvests, and planted stands after clearcut harvests in the Miyaluo area, western Sichuan of China. Stands of the latter two types were of various age since the last clearcut. Results showed that the population of T. cymbifolium from the intact stand displayed the highest level of genetic diversity, and populations from the planted stands exhibited significantly higher levels than the naturally regenerated stands. In planted stands, genetic variation within populations increased over time. These findings indicated that habitat destruction by forest harvesting led to the reduction in genetic variation within populations, but that given time, artificial reforestation after clearcut was effective in promoting the recovery of genetic diversity in the recolonized moss species. Therefore, lengthening the normal felling rotation of plantations should be favored to restore and conserve genetic diversity in recolonized species. In addition, thinning young plantations via selective logging may provide heterogenous microhabitats similar to those in the old stands, and thereby facilitate the development of bryophyte communities and the increase of genetic variation of the recolonized mosses.