Ripariums and paludairums are not the same thing.
Unlike many paludarium setups, ripariums do not have any real terrestrial area, so there isn't any place to plant upland plants.
This did not answer the question.
What is a terrestrial area? What defines that?
I'm not sure how you plan to decouple the linkage between the water and the land.
I suppose one could use the definition of the wetland soil, one that is 100% lacking in air space. So any region that has air space in the soil + some submersed growth would be defined as a paludarium?
Anything with no terrestrial root area(100% saturated sediments, water column) but emergent leaf/stem/shoot growth, would be a riparium?
Thing that bugs me is the riparium definition since is means something very different than your definition here versus the Biological side of things:
It includes both zones and the transition itself, not just one, in other words, riparium would be a better descriptor than paludarium.
"Marsh or swamp" is the descriptor for paludarium. Futhermore, "Marsh" and a "swamp" are very different to a wetlands ecologist.
It would seem more appropriate to use the term riparium
for a broader range and simply do away with the paludarium
term altogether. Perhaps that should be argued for rather than changing the definitions of each around.
Riparian is a river bank/stream bank, marshes are very different, but many of the plants chosen are marsh, not river plants. A few are swamp plants. Hydrophilic plants characterize these zones and not the % saturation of the sediment or submergence.
I think it would lead to much less confusion to keep the term boarder and then do away with the paludarium term, since it is less board and misnamed in general. Marsh/swamp plants really do not define what has been often called a pauldarium.