Humans have created seed banks for preservation where seeds are stored under climate controlled conditions to ensure they remain dormant for planting in the future. But these seeds will have genetics that reflect the conditions they were made in, which maybe quite different by the time we get around to planting them. They will be frozen in time, in a way, limited in the genetic information they can utilize.
A soil seed bank is the cache of seeds that are naturally stored in the soil, remaining dormant until conditions are right for those particular seeds to grow. This is replenished with new seeds, best adapted to current conditions, every year, resulting in a collection of seeds reflecting adaptations over time.
By collecting seeds from different stands and planting them together, you can help dwindling populations by reinvigorating the local gene pool. Seeds that are produced in the generations following your plantings will have genetic traits waiting to be expressed that are conducive to more recent environmental conditions.
I have been calling this effort of seed sowing the encouragement of a living seed bank.
This is a way to foster the resilience of the soil seed bank, a chance to find expression for whatever adaptations maybe needed in the future.