Some researchers have emphasized the importance of functional differences between species and the relationship between species in space and time rather than the effect of species richness per se on improving ecosystem functioning (Landis et al., 2000). Species from different functional groups differ significantly in their use and acquisition of resources (Reich et al., 2004). The loss or gain of functional types within a plant community can change the flow of energy and resource supply, thereby changing the productivity of the community and functioning of the ecosystem(Reich et al.,2012).