Norm,

The original question was "why is water is so easy and prairie is so difficult?"

In ponds and lakes it is easy to establish the bottom of the food chain nutrients. You get a lot of help as per the other replys.

On land, the bottom of the food chain nutrients are harder to re-establish. I once poured a container of liquid nitrogen out on the grass behind the lab and it sterilized a three foot diameter area that took several years to regrow. Carbon must be broke down before it can be used and the microbes and much smaller animals that do it require a balanced diet and a balance environment that is normally established over a long long period. Prairies are a special problem as they lack certain nutrients to support higher level life forms such as trees. In my area, the prairies contain too much salt.

Bottom line, to re-establish any killed off land area, bring in healthy earth from healthy near by areas and spread over the killed off areas.

Dennis