In theory, a community is defined as a set of species occupying the same place in the same period of time. If you have reason to believe that the same individual will not occupy more than one of your plots during your samplings, go ahead and consider plots as distinct communities.
A useful reference on this topic is:
Fauth, J.E., Bernardo, J., Camara, M., Resetarits Jr, W.J., Van Buskirk, J., & McCollum, S.A. (1996). Simplifying the jargon of community ecology: a conceptual approach. The American Naturalist, 147(2), 282-286.
Plots are not communities if they share the same environmental/physical conditions as others and have species that potentially interact with species in other plots, since these are the parameters define communities :)