Growth and morphological responses to water level variations in two Carex species from Sanjiang Plain, China

摘要

Sanjiang Plain is the largest freshwater marsh wetland in China.?Carex lasiocarpaand?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 inC. 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.