Difference in spatial distribution patterns and population structures of Rhododendron hainanense between both sides of riparian bends

Aims Riparian zone is the intersection of stream and terrestrial ecosystem, which has rich biological diversity. Stream is usually curving because of water flush and topography effect. The flow velocity, sediment properties and plant propagule aggregation are different between inner and outer sides of the bend, which leads to differences in plant population structures and spatial distribution patterns between riparian bends’ both bank. Our aim was to reveal the differences in spatial distribution patterns and population dynamics of Rhododendron hainanense, a shrub endemic to Hainan and Guangxi of China, on each side of a stream.Methods Three nature reserves on Hainan Island were chosen as studied sites. In each site, two riparian bends were set as transects. The spatial distribution patterns and population dynamics of R. hainanense were compared for the convex versus concave banks by a method of “variance/mean method”.Important findings (1) Rhododendron hainanense populations were at increasing stage on convex banks, but at declining stage on concave banks. (2) Rhododendron hainanense populations were at growing stage on both upstream and downstream of convex banks, but the ages of the individuals on concave banks were not continuous. (3) The number of individuals of each age-class declined away from the top of bend or river bank. (4) At scale of 2 m × 2 m, the individuals showed an aggregation distribution on convex banks and their downstream, but a random distribution on the upstream of convex banks, and on concave banks and their upstream and downstream. The fast flow and steep slopes may be the main reason for the fewer individuals and declining population on concave banks than on convex banks.