The diet is the most likely cultural aspect that will be affected by this region's vegetation.
Explanation:
The region that is described is obviously a rural region, where agriculture dominates. As said, the soil is very fertile but only suitable for few plants to be grown and at a high quality. While the people living here will naturally be slightly more isolated and have their own unique cultural traits, the most affected by agriculture will be their diet.
Since people are able to produce high quality and high quantity of only a few plants, it is easy to assume that those few plants will be dominant in their diet. Living in a rural environment will also mean that the available agricultural products from other places will not be in a very high number, so the people will use their own products. This will result in the development of numerous specialties based on the few dominant plants, creating a unique cuisine in the region.
