Effects of sediment burial disturbance on seedling emergence and growth of Suaeda salsa in the tidal wetlands of the Yellow River estuary

A greenhouse study was conducted to determine the effects of sediment burial on seedling emergence and growth of Suaeda salsa (L.) Pall. (Chenopodiaceae), a pioneer species in the tidal wetlands of the Yellow River estuary. From April to June in 2009, seeds of S. salsa were artificially buried at 0, 1, 2, 3, 4, 6 and 8 cm depths in plastic pots filled with unsterilized sediment. Results showed that the percent emergence, emergence time, seedling height, absolute height growth rate, relative height growth rate, stem diameter, number and length of branch, hypocotyl length and dry mass were significantly affected by burial depth. The percent emergence of seedlings had a significantly negative correlation with burial depth. Seedling emergence occurred from a maximum depth of 6 cm with most seedlings emerging from 0 cm depth. No seedlings emerged from 8 cm depth. The shortest emergence time occurred at 0 cm burial depth and seeds buried at 6 cm took significantly longer to emerge than those at other depths. With increasing burial depth, there was a stimulatory effect on seeding height, number and length of branch, stem diameter and dry mass, and simultaneously, the leaf: mass ratio increased, while stem: mass ratio decreased. The experiment also indicated that sediment burial disturbances could stimulate the hypocotyl below sediment to form adventitious roots, and the formation of larger root system would probably enhance seedling establishment, reflecting that the S. salsa seedlings had special adaptive strategy to the rapid sediment burial in the tidal wetlands of the Yellow River estuary.

Research Highlights
► The percent emergence had significantly negative correlation with burial depth.
► The highest emergence rate and shortest emergence time occurred at 0 cm burial depth.
► Sediment burial stimulated the morphological characteristics of seedlings.
► With increasing burial depth, the leaf-mass ratio increased, while stem-mass ratio decreased.
► Sediment burial disturbances stimulated the hypocotyl below sediment to form adventitious roots.