Effect of different enclosure durations on aboveground vegetation in typical steppe on Loess Plateau

In this study, we analyzed community structure, species diversity, and succession dynamics of the aboveground vegetation in different enclosure durations of a typical steppe on the Loess Plateau. We conducted field surveys and laboratory analyses to disclose the dynamic variation of aboveground vegetation during the natural restoration process. The results showed that both the biomass and thickness of litter increased, the total community increased initially and then gradually decreased, and the community density decreased with increasing fencing years. The total aboveground biomass and grass biomass both increased initially and then gradually decreased, and were the highest in grasslands with 32 years grazing exclusion. Species richness increased first and then decreased after the grasslands were fenced. There was no significant effect of fencing year on the Simpson diversity and Pielou evenness indices (P>0.05). The natural restoration under fencing management followed a general pattern, in which 1) forbs dominated in the early succession stage, 2) Stipa bungeana gradually became dominant, and 3) the development of S. bungeana stabilized.