Part one: what's life?

Essentially, Twith the word "Humus" we intend the meeting point of two oo opposing processes: of degradation and construction of organic molecules/bodies (organic = built around a skeleton of carbon atoms). Referring to the dominant biologic occur in the organic and organo-mineral parts of these soil. Referring to these rather biological processes, it i soil scientists and biologists preferable  to use the more rigorous terms of biodegradmineralisation an(return to mineral components) and humification, respectively. Naturally you find humus in the (genesis of new organic molecules). The more organic and richer in organisms top part of a soil. This part is the soil is called  Humipedon is the point where the phenomena of life and death meet. Any dead body or body partstructure naturally falls to the ground and is here decomposed there. It is not even that easy to tell when a body is dead. A falling leaf, for example, can we say that it is more dead on the ground than when it was already yellow on the tree? If we leave aside these "border areas", wdefine when a structure is dead. Yellow leaves on a tree, for example, are they still dead? We can probably say that when a leaf reaches the ground it is dead and is on on the way to become something else. The future of a bodyleaf under degradation is new life. To parted in two: mineralisation and humification, both necessary to build new living structures. To stay alive, youa living complex must firloose part of its components, which must die to produce new input (Figure 1). Or vice versa, as in the question: "Was the chicken or the egg born first?"

Figure 1. To stay alive, pecople must mplex structure must partially die^[1]. In a single persHon's time, an individual is born, grows and dies. Even in the time of the generation of a population. But wever, something almost miraculous happens: the nextw generation never starts from the same point asof the previous one, but from something differentgeneration; it starts from a re-elaborated base. It is this something differentnew base that evolves linearly over time, regardless of the life of the iindividual or the populations' life. In this long-term process, the humus is found between one generation and another, between the death of the first and the life of the second. For this reason it is intriguing as a concept. There are scientists who claim that humus does not exist^[2],characterise the period of time that separates dying and nascent generations. For this that there are molecules that change, but never humus. But if we think in this way, then we human beings don't even exist, because we aason the humus concept is an intriguing mattere jus^[2] t molecules that change over time too. Not attracted even Erwin Schrödinger was able to answer 's spirithe^[3].

If quwestion, and no one else did better than him^[3]. consider that life Thbe final impression is that to be able to live well is not necessary to know what life is.

The gins with a first "living cell", the early Earth was devoid of life if we consider that life begins with a first "living cell". A name has also been found for itthis hypothetic primordial "living cell": LUCA (Last universal common ancestor: https://www.imperial.ac.uk/news/120606/who-what-luca/ ). Problem: to make a cell you need cell is made of complex components that couldthemselves might be considered "already alive". It is objected that in order to be alive it is necessary to On one side, a living structure should be able of auto-reproduce. Unfortunately, even an atom is so complextion; on the other side, if studied in its elementary components, that we have not yet understood what it is made of, except by activating our imagination. Weven a physical atom is so complex and moving, we don't know if an atom is "alive"whether it is composed of micro-creatures. At the larger molecular level, thinking that a DNA molecule ismight be somewhat "alive" is not considered  completely absurd. Although not everyone agrees that viruses are aliveliving beings (https://www.scientificamerican.com/article/are-viruses-alive-2004/ ). There are scientific reasons to think that the molecules that make up the genes of each DNA command natural evolution^[4]. Are those selfish genes alive? 

We love be thinking that a Miller-Urey's soup^[45] might was a soil at its origins, an archaic correspond to a primordial soil, a very liquid primordial humipedon. Certainly there is organic matter in the black space of the universe^[56]. It is very likely that organic molecules from space were also present on the surface of planet Earth when LUCA was generated. Before LUCA there wasere only a Miller-Urey soupps, probably at different stages of evolution. Admitting this does not only mean that this is how life was born, but also that it may continue to generate like this at present time; that LUCA was born in an "embryo of "-soil"; that this soil embryo-soils still exists today and continues to generate life, even if conditions have changed. It is assumed that at the origin, every new ecosystems. In their soup, Miller-Urey did not found living embryo is a tiny Miller-Urey soup. In beings but molecules remaining separate. We know that Miller-Urey's soup no living beings are born but ecosystems, ecosystems that contain parts of living beings or complete living beings that are not separate fromcontinued to evolve and to change until the conditions of the soup allowed a functional construction called LUCA to generate. We know the following steps in larger and larger soup-ecosystems. Citing only the crossing stones: Margulis^[7] witheir environment of genesis. We know the story for the next steps. Citing only the nerve centers of history, Darwin's evolution her symbiotic primordial entities; Darwin's ecological vision of the evolution as a consequence of adaptation of individual characters within changing natural populations of species^[68], containexplad in ecosystems as defined by LovelockTansley^[79], explained for the chemical-physical aspects at the planet level and by Margulis^[8] for the biby Lological ones at the level of living primordial entities, connected to the rest of the living as in the observations of Darwinock^[10]. From the point of view of a soil scientist, the process of "genesis and evolution of ecosystems" is still active and should be seek in a sort of "humipedon", even at present day. Mitosis, first, and meiosis, later, might be the result of a controlled evolution of Miller-Urey soup. That all cells are Miller-Urey soups evolving into larger ecosystems. A pure biologist point of view can be take a similar when they way when investigateing the boundaryies between life and death in cells. Usually the concept of apoptosis comes into play^[11][12], whichand on the one hand killsil allows to kill/erase and on the other to create/modify cells, organs or whole organism, in equilibrium at each respective scale and within evolving specific environments. Diseases and cancer can be placed in a context of evolution^[9][1013].

Part two: Humus systems

UnA humus system is an abstract category in which soil scientists set all humipedons that show a similar aspect and functioning.  Imagine a specialist who has seen all the hhumus lover who studied many humipedons inall around the world and who wishes to tell others about them. Recall that the humiped is the superficial part of the soil, the first centimeters of soil, those that if you open a hole, you see that they are darker than the rest ofant to inform a friend on this: "in submerged areas I saw  thick, organic and dark humipedons; in less humid environments I saw humipedons inhabited by earthworms which incorporate to the soil. If one asks this specialist to describe all fallen litter; in dry zones the hiumipedons he has encountered, he will have to classify them, put them in different boxes. Roughly he will say: "I sawwere full of insects, mites, springtails and litter accumulates at the surface of the soil as it was a roof for their home; on mountain rocks exposed to sun wind and rein I found thin crusty microbial humipedons in the water and they are usually very thick, organic and dark; then I saw buckets: in some tvery different from those grey thick and silty forming in at the bottom of rivers and lakes or seas .... "

There were earthworms, in others insects, mites, springtails; others were in unthinkable plachumipedons cover all planet Earth surface. They were first classified in humus types^[14][15], on the highest rockn in humus forms^[16], ian the world but also in the depths of the oceans .... "On planet earthd finally in humus forms grouped in humus systems^[17]. tThe following have been provisionally described: 5  five systems in fresh water, 2 in salt water, 5 in dry enot submerged environments, five in submerged areas, two at the sea-side, six in very specific environments and 6 in" strange "environments and 2 anthropogenic. See photographs in Humipedons. See c(pioneer or primordial ecosystems), and two conditioned or man-made. Classification and distinctive characters in the Morpho-Functional Classification of the Planet's Humipedons.

Part three: Humus Forms

Once yoHu know how to recognize humipedons, you want to see if within the category there are are all different "forms of them", i.e. humipedons that , even within the samea humus system can be different from the other but not so. The thickness of the litter layer can be very different to end in another system. For example humipedons of the even within a same Mull system that never have  leaves on the surface. You wonder "they too are made from e. Why? Leaves may be more or less palatable, earthworms, I see their droppings here and there ... why in this forest the earthworms eat all the have preferences and do not eat all species of leaves quickly, while in this other they don't? And it turned out that there are more palatable leaves than others, that some specie, the number of earthworms is connected to many soil variables (compaction, acidity, humidity ...) and influences the thickness of trees seem to want their leaves to be undigested to earthworms, that he litter on which these animals feed, leaves remain a long time on poisoned soils .... In short, it is interesting to describe and be abbe able to individuate some different forms of humuhumus forms in each humus system. Eventually, going into detail, t the planet Earth is covered with humipedons which can be cclassified into "humus systems", which in turn can be subdivided into detailed in "humus forms" (Figure 2).

Figure 2. Humus systems and humus forms^[1]. The figure shows an open profile divided into horizons. Each humus system is characterized by specific diagnostic horizons. Depending on the thickness of these horizons, humus forms can be identified within each humus system. The subdivision of the Moder system into three forms of humus has been illustrated on the figure. Hemimoder, Eumoder and Dysmoder. Eumoder is the "central" humus forms, corresponding to a typical Moder. To know more: https://www.sciencedirect.com/journal/applied-soil-ecology/vol/122/part/P1 ; https://www.sciencedirect.com/journal/applied-soil-ecology/vol/122/part/P2. TheAn Andre is also anoid and iOS application (TerrHum) to take to the fiis available for freeld^[18]. thaIt helps to recognize these diagnostic horizons^[11] and humus systems and forms in the field.