Abstract: Glehnia littoralis is an endangered rare plant species, with natural habitats along the sandy seashore of eastern China. At a sandy coast of Jiaonan, Qingdao, we investigated the pattern and structure of wild G. littoralis populations that grew before and behind an artificial beachridge, so as to elucidate the recruiting mechanism of the wild G. littoralis and relevant responses to such a beach ridge. The results showed that G. littoralis individuals seaward before the ridge were clumped at spatial scales less than 2.5 m. Adults positively associated with seedlings at finer spatial scales, and might associate neutrally, but not negatively at larger scales. G. littoralis individuals behind the ridge had their aggregative scales and degrees shrunk or weakened, and spatial associations between adults and seedlings turned to be loose or even negative at most scales. The ridge was believed to have affected structures of G. littoralis populations as well. The populations before the ridge exhibited higher relative density, seedling abundance and fruiting rates, i.e., recruiting normally, but behind the ridge, they behaved otherwise. The evidence justified that such a beach ridge has adverse effects on recruitment of G. littoralis populations, presumably because it can prevent seawater from inundating and dispersing seeds of G. littoralis along the seashore.

Key words: generalized additive model (GAM), the tropical Atlantic Ocean, longline fishery, Tweedie distribution, Pseudocarcharias kamoharai