Abstract

Yan LU

Sanjiang Plain is the largest freshwater marsh wetland in China. Carex lasiocarpa and Carex limosa are two dominant species in the area. The niche of C. limosa is similar with C. lasiocarpa and both species always distribute in the same region. However, the distribution area of C. limosa is far smaller than that of C. lasiocarpa. The aim of the study is to determine whether C. lasiocarpa had superiority in plant growth than C. limosa in the condition of submergence. To this end, plant growth and root morphologies were investigated in two Carex species. Experimental treatments included three water levels (0, 10 and 20 cm) . Relative growth rates in C. lasiocarpa (0.038 g g -1 d -1 ) were much higher than that in C. limosa (0.030 g-1 d -1 ) under 20 cm water level. There existed more severe effects in biomass accumulations in C. limosa (dropped 77%) than that in C. lasiocarpa (dropped 52%) when comparing 20 cm water level to 0 cm water level. Enhanced water level could enhance root porosity (C. lasiocarpa 20.4% and C. limosa 21.5%) in both species but form shorter roots in C. limosa. Higher relative shoot growth rate could be found in C. lasiocarpa under deep water conditions. These data could explain why the two species had the same niche but different distribution areas in Sanjiang plain.