Structure and Dynamics of Herbage Synusia in Sapotou Planted Vegetation for Fixing Sand Dunes

The species structure and importance value dynamics of annual plants in herbage synusia during a growth period have been observed, and the ecological mechanisms of these changes have been analyzed also. The conclusions are as follows: (1) \%Eragrostis poaeoides\% is the dominant species in herbage synusia, and it contributes more than other species in individual number, coverage and importance value; (2) A lot of annual plants seeds germinate after sufficient rain, but all annual plant populations decline along with lack of rainfall. \%Eragrostis poaeoides\% and \%Chloris virgata\% decrease more than \%Setaria ruthenica\% viridis, \%Bassia dasyphylla\% and \%Corispermum declinatum\%. The amount of every species in synusia change little in the later of growth period because of more rainfall. (3) The amount and frequency of \%Setaria ruthenica\% viridis, \%Bassia dasyphylla\% and \%Corispermum declinatum \%change little through whole growth season and their relatively coverage increase along with time. (4) Structures and dynamics of herbage synusia are correlated with rainfall.