'Farming in Nature's Image' is a simple and very successful concept. It means working with nature, making decisions based on what would happen in the natural world if Man wasn't interfering.
Mob grazing is one example - I've already talked about the massive herds of grazing animals that used to roam the grasslands of Europe, Asia and America and which mob grazing, albeit on a small scale, tries to emulate.
The growing of cover crops is another example. Nature hates bare soil. She will do her utmost to cover it, firstly with fast growing weeds, forbs and brassicas, then with legumes and grasses and finally, if the climate is favourable, with bushes and trees. Nature also hates monocultures. They are never seen in the natural world. Instead, different species fill different micro-niches in the same area, the result being a mixture of small and tall, leafy and woody plants all occupying the same area of land.
Planting cover crops is an attempt to mimic this, and as Gabe and Jay both emphasised, the more variety the better. Within their cover-crop seed blends, they aim for a mixture of warm season broadleaves, warm season grasses, cool season broadleaves and cool season grasses, to ensure growth at different times of the year and under many different weather conditions. The ratios of each will depend on the crops grown previously, the crops to be grown afterwards, and the current levels of biological activity in the soil.
Ideally, cover crops are 'harvested' by mob-grazed animals (again, it's believed that the more variety of species - cows, sheep, hens, deer, etc - the better). A proportion of the cover crop will be trampled, forming the vital litter covering on the soil. The remainder of the cover crop will be consumed, digested and excreted as dung and urine, mixed with high numbers of microorganisms from the gut - the latter is the vital additional biology the soil needs to spring into life.
The principles of 'farming in nature's image' are simple: Look at what happens in a natural environment and use this to guide management decisions. Don't fight nature, it's so complex and has so many options, it will always win in the end. Instead, the message was clear, work with nature and you will reap dividends.