For canopy trees you can; see under citations of my attached article. For herbs you cannot in the same way at mid-resolution. In this case, the plant diversity is mostly among herbs as is common in temperate and Mediterranean Europe.
Article From monospecific to mixed forest after fire?: An early fore...
What aspect of diversity are you trying to estimate? If it is structural diversity, there is some reason to believe that you can estimate this, especially if you have LiDAR data to help train a Landsat based model. If you are talking about species composition, then I am afraid you will be much more limited in your inference, as stated by Hein Van Gils.
Thank you! I preferably seek to estimate plant types as tree,shrub,bushes,grass. in this context, I research about the relation between plant community and geomorphic characteristic.