Abstract: Bottom-up and top-down effects as well as intra and inter specific interactions drive plant growth and reproduction in the salt marsh. Compared to the bottom-up effect, however, the top-down effect has been largely overlooked. Phragmites australis is a dominant species, whose populations living in the high marsh are important and unique in the Yellow River Delta. To reveal the impacts of the top-down factor on the growth ofP. australisseedlings in the high marsh， we investigated the effects ofHelice tientsinensis herbivory on their growth by establishing 24 plots with a size of 2 m×2 m. The seedlings ofP. australis were heavily grazed and damaged by crab. In all plots, 52.41% of seedlings were not consumed by crabs, 27.04% of seedlings were mildly fed, and heavy herbivory by crab accounted for 20.54%. The growth of seedlings was significantly influenced by crab herbivory. Heavy herbivory by crab strongly reduced the height, leaf number and leaf length of seedlings. The top-down effects should be considered in the protection and management of P. australis vegetation in the Yellow River Delta.

Key words: forest management history, broad-leaved Korean pine forest, research history, Changbai Mountain Region.