Riparian C₄ Plants on the Mainstream of the Yellow River:Assemblage Characteristics and Their Indication on the Effects of Reservoirs

We conducted an investigation into the plant assemblage of the Yellow River’s mainstream between September 16th and October 31st,2008.The total of 34 C₄ plant species were recorded,belonging to 9 families and 24 genera,which corresponded to 27%,28% and 25% of the total species,families,and genera respectively.Further analyses indicated that:(1)Gramineae and Cyperaceae were the dominant taxa in the area,contributing 61% of the C₄ plants in species number.(2)The number of C₄ plant species increased from the upper to the lower reaches of the river,while the standing crops and the C₄/C₃ ratio in the middle reaches were higher than those in the upper and lower reaches.(3)The number of C₄ plant species and C₄/C₃ ratio were correlated with altitude,annual air temperature,precipitation,and discharge,while the biomass of C₄ plants only had a significant correlation with annual precipitation.(4)The C₄/C₃ ratio in the reservoir region was higher than that in adjacent regions,which suggests this ratio may be an indication of vegetation dynamics under the disturbance of reservoirs.