A basic concept that is the cornerstone to immerse oneself in the attempt to understand the functioning of Nature. We aim to work with Her, not against! 
Through the observation of natural phenomena, we can understand the reasons why the way of life typical of today's culture is so incredibly energy-intensive. The truth is that we are not opposing Nature, we have no reason to think we can bend it to our will, we are not something different!! We are an integral part of it.
"We are all leaves from the same tree. We are all waves from the same ocean." -Thich Nhat Hanh
Ecological Succession is the expression of the evolution of ecosystems over time. 
The classical theories of succession hold that a geographical area reaches out towards a particular and predetermined climax, or a stable stage of maturity, but this is not quite the case. The succession is cyclical. It has no beginning, no middle and no end; and not even an extended territoriality, but it depends a lot from ground to ground. It arises from a disturbing event, a destruction that, for a change, creates the opportunity for a new rebirth.
This non-linear model of succession therefore describes a mosaic of infinite corners of the world in slightly different states of maturity, depending on their own events and microclimates, belonging to a larger territory. 
"No matter what forms we observe, but particularly in the biological world, we should nowhere find anything lasting, immobile, complete; rather we will find something in constant motion." -Johann Wolfgang von Goethe
Wanting to empirically evaluate the development and transformation of an ecosystem, the succession brings a place towards the most flourishing expression of Life (microorganisms, plants and animals) suited to the present conditions (soil, water, air, light). Nutrients and minerals are accumulated, organic matter in the soil and species diversity increase, and the entire system grows towards health and wealth. 
It occurs in two main phases: one of accumulation, in which the conditions in which to thrive are created, and one of abundance, characterized by more complex and demanding organisms. Furthermore, Nature expresses itself over time in changing and different ways which, as mentioned above, are totally dependent on the pedoclimatic conditions of the specific part of land. It is therefore deduced that each area of the world tends towards a different maturity, be it forest, scrub, savannah, prairie or desert; the fundamental principle in common is that it represents the best manifestation of biology in relation to environmental conditions (chemical-physical-biological characteristics of the soil and climatic, including water).
Regardless of these technical denotations, a symbol of the extreme complexity (and beauty!) That surrounds us, I try to explain in a simple way the evolution of a bare land towards maturity.
Let's take the Po Valley, where I live (or the german plains, where most of you live) as an example, simplifying and considering it for its peculiar geographical area characteristics in a humid temperate / continental climate. In principle, a colonization system (bacteria, lichens, mosses, fungi) sets the stage; a group of placentas (“pioneer” plants, characterized by a short life cycle and a high rate of reproduction) thrive for a few years and, as the term suggests, prepare and care for; a secondary forest (shrubby and arboreal perennials) takes hold, integrating and reaching out; the definite stage of climax (huge and centenary trees) is established and supports a high biodiversity. 
You can universally see how organisms organize themselves in order to make the best use of any resource (Scarpetta only, no waste!!) and evolve into a self-regulating, self-maintaining and self-renewing system in the magnificence of biodiversity. This is the Law of Nature!!
Understanding this, we should not be surprised by the dynamics of modern agriculture (and society): the few plants that form the basis of the diet of billions of people grow in the very first phase of succession, requiring an enormous amount of work (energy input) to maintain succession at such an early, highly unstable stage, in which the drive for diversity, represented by weeds, insects and microorganisms, is enormous! And then down to "agricultural practice", based entirely on oil: repeated deep plowing, synthetic fertilizers, herbicides, pesticides, fungicides .. (waiting for CORONICIDE, aren't we?).
It is simply against Nature.. I repeat, we will never win it!!
"Man makes mistakes, Nature makes successes." -Aristotle
The "intermediate" state of succession is the most productive during the life of an ecosystem; here most of today's food-producing crops thrive. The amount of work required to maintain this stage is less than what we spend today on our annual monocultures.  Easily we realize the different applications in Permaculture that already exist, and work: agroforestry, mixed crops, food forest, synergistic gardens, syntropic agriculture .. The garden should be composed of a variety of microcosms in different states of succession, just like a true ecosystem, so as to require a lower human energy input for its maintenance and have a luxuriant overall stability.
In time and space, Life unfolds from and into Death in a harmonious dance that represents the most appropriate way to achieve the spontaneous process of evolution towards abundance. Nature knows no mistakes, it manifests itself in the best element to flourish: weeds are the expression of Regeneration in its most majestic form! It is therefore up to us to have the patience to observe, recognize and interact, through the design practice, in order to integrate elements useful for human sustenance, accelerate the process and let biodiversity reveal itself in respect of all its forms.
 Bill Mollison, "Permaculture, a designer's manual"
 Toby Hemenway, "The Garden of Gaia"
 Dave Jackie and Eric Toensmeier, “Edible forest gardens vol. I”
 Martin Crawford, “Creating a forest garden”
 Eric Toensmeier, “Paradise lot”
 Ernst Götsch – Syntropic agriculture