Abstract: Abstract Aim Different levels of tidal flooding have significant effects on mangrove sediment nutrients and stoichiometric characteristics, and plant fine root functional traits are important strategies to cope with nutrient changes. However, there is a lack of in-depth understanding on the correlation between mangrove sediment nutrient changes and fine root functional traits at different tide levels, and relatively few studies have been conducted to explore the nutrient acquisition strategies of exotic and native mangrove plants from the scale of fine root functional traits. Methods The study used native species Bruguiera sexangular and exotic species Sonneratia apetala to sample fine root and rhizosphere sediments at different tide levels. The relationship between fine root functional traits of two mangrove species and the content of nutrients and enzyme activities in rhizosphere sediments was analyzed. Important findings The results showed as follows: 1) The exotic species has higher nutrient acquisition requirements and stronger metabolic capacity than the native species, and both species are subject to a certain degree of nitrogen restriction. 2) Within a certain range, the conversion rates of nitrogen and phosphorus in sediments accelerate significantly with the increase of waterlogging degree, and the contents of ammonium nitrogen, nitrate nitrogen and available phosphorus in sediments increase with the increase of waterlogging time. 3) The specific root length of fine roots of the two species was significantly positively correlated with the nitrate nitrogen content in the sediment, indicating that the increase of sediment nutrient availability played an important role in promoting the root elongation of mangrove plants. This study can provide basic data and scientific refercne for the environmental protection of mangrove ecosystem and the development and utilization of biological resources.

Key words: Mangroves, Fine root functional traits, Intertidal elevation, Sediment nutrients, Nutritional restriction