Characteristics of the early secondary succession after landslides in a broad-leaved deciduous forest in the south Minshan Mountains

- Species diversity increased rapidly then slowed down during 8 years after landslide.
- Species turnover rates were high at first and then decreased since the third years.
- Species composition changed greatly during the first two years and then stabilized.
- Leading species became diversified with years and species substitution was obvious.

Landslide has been recognized as the major disturbance to the natural vegetation and a key driver of the forest succession in the mountains of the Southwest China. An integrative understanding of the early succession following landslide disturbance is important to explain the formation and maintenance of the species diversity, and useful to the forest ecosystem management and ecological restoration strategies designing. To explore the characteristics of the early secondary succession on landslides, we monitored the plant community on landslides within the Longxi-Hongkou National Nature Reserve, Dujiangyan County, Sichuan Province, China. We set 64 permanent quadrats (2 m × 2 m) on two landslides with similar geography conditions formed in September 2009. Species richness, percent cover, and the height of the each vascular plants in all quadrats were investigated in each spring, summer and autumn from 2010 to 2017. Species richness, cumulative species richness, and Shannon-Weiner index were calculated to describe the dynamics of the species diversity. Jaccard similarity index and species turnover rate were calculated to describe the changes of species composition and species turnover. Our results showed that the species diversity of the vascular plants increased rapidly during the first four successional years and then slowed down since the fifth year. We found a delay effect that the increase rate of the species richness and cumulative species richness peaked earlier in landslide scale than that in 2 m × 2 m quadrat scale. Species turnover rates were high during the first two years and then decreased since the third years. Species composition of both woody and herbaceous species changed greatly during the first three years, but tended to be relatively stable since then. The leading species in the 2 m × 2 m quadrats became more and more diversified in both herb and shrub layer, and substitution of leading species was obviously observed. Our findings suggested that under the set of particular environmental conditions, e.g. a nearby rich-species pool, high precipitation, suitable soil humidity, and moderate atmosphere temperatures, a crashed plant community caused by disasters could flourish again rapidly as long as no any intense disturbances occurred. The high recruitment of the plant species on the landslides also explains partly how the rich biodiversity is formed and maintained in the study area.