The ecology of six Rhododendron species (Ericaceae) with contrasting local abundance and distribution patterns in Hong Kong, China

Six native Rhododendron species grow in the degraded, fire-prone landscape of Hong Kong: R. simsii and R. farrerae are common and widespread, R. moulmainense is relatively restricted, and R. championiae, R. hongkongense, and R. simiarum are rare. For all species except the rare R. simiarum, there was direct or indirect evidence of regrowth after fire, but only the two smallest and commonest species grow in sites which are frequently burned. Both flowered within 18 months of a fire. Most populations of all species, except R. simiarum, had a deficiency of individuals in the smaller basal circumference classes. Seedlings were found only in three out of four plots of R. simiarum, and one of R. farrerae. A few seedlings of the other rare species were seen in open, litter-free microsites outside the study plots, but no seedlings of the most common species, R. simsii, were seen anywhere. In logistic regression models, one or more measures of plant size were significant positive predictors of flowering at least once in the three year study period for all species, while percentage cover by surrounding vegetation had a significant negative impact on all except R. simsii and R. farrerae, for which no populations are strongly-shaded. Although the absence of current recruitment is not necessarily a cause for concern in long-lived species that can resprout after fire, we recommend that active vegetation management should be tried to enhance the survival and reproduction of R. moulmainense, R. championiae and R. hongkongense, and that new populations of these species and R. simiarum should be created.