Not experienced with PG ARK, but some information from the "official" guide.
Increasing the density of a resource in a biome will decrease the distance between instances of that resource, in that biome.
For example raising Jungle Tree Density will decrease the distance between jungle trees.
The only parameter I expect to impact bushes will be Grass Density for various biomes (ex. Jungle Grass Density).
All of this of course requires you to create a new procedurally generated ark.
The alternative would be to increase the gather rate, which would cause each bush to give more fiber and berries.