Reestablishment of indigenous vascular diversity under fallow blanks of clear cutting Chinese fir plantations in the subtropical region of China

Fallow provides an important regeneration chance for many tree species after clear cutting,but its role in the restoration of forest fragments and conversion of timber plantation into continuous nature forest landscape is not clearly documented.To examine the role of fallow in reestablishing native tree diversities and assessing whether fallow can be used as a tool for the fast conversion of plantation to natural forest,the authors compared floristic diversity and community composition of vascular plants in 23 years old Chinese fir(Cunninghamia lanceolate(Lamb.) Hook.) plantations(>15 hm²,as the control;A),10 years old secondary forests((12 hm²),fallowing treatment;B) and two 120 years old matured secondary forests(>15 hm²,target;C) in the Huitong of Hunan Province,subtropical part of China.Resultsindicated that Pielou's evenness of plant species among forests was insignificantly different due to the studied parameters such as strata,canopy and understory and four life forms(herb,shrub,tree,and vine).However,species richness,Shannon diversity and Sørensen's index of dissimilarity were higher in fallowing immature secondary forest than those of the plantations of Chinese fir.Based on non-metric multidimensional scaling(NMS) ordinations,estimated values revealed clear separation between forest sites in different succession stages at each of four life forms,and further showed a significant effect on understory vegetation of Chinese fir plantations untill to old growth secondary forest,indicating an increasing beta diversity.Although regression analysis exhibited that herbaceous composition(represent by NMS 1 scores) had not affected tree species turnover,but the combined effects of herb with shrub and vine facilitated the regeneration of tree species.Therefore,results evidently indicate that the higher species variability during fallow after clear cutting timber trees is associated not only with the higher alpha diversity but also with the higher beta diversity,and show that fallow can be used as a tool for the conversion of plantation and enriching floral diversity.