There are two main processes of material flow in the ecosystem. One is the geological circulation process, also called geochemical circulation process, which refers to the material circulation process between the continent and the ocean. The rocks on the land surface become fine particles after weathering and release soluble materials. Some fragments and soluble substances, washed and leached by precipitation, finally flow into the ocean with flowing water and deposit to the ocean floor, forming various sedimentary rocks. In the long geological years, due to the crustal movement and sea land changes, the rocks at the bottom of the ocean rise to land again, and the rocks are weathered again. This process takes a very long time and covers a very wide range, that is, the geological cycle of materials. It is the basis of small biological cycle, but it only forms soil parent material.
The other is the biological small cycle, that is, the cycle process formed by various chemical substances in the biosphere between plants, animals and soil (microorganisms) through the transmission medium atmosphere or water. The biological small cycle is a small segment of the geological large cycle, mainly the life activity process of green plants. It absorbs the co in the atmosphere two And water and inorganic salts in the soil, forming a huge plant organism; Plants return to the soil in the form of dead branches and leaves, or absorb and excrete through the feeding, digestion and excretion of animals. After the animals die, they are decomposed by various microorganisms and stored in the soil humus, which can also be absorbed and utilized by plants to form the bioaccumulation and Mineralization process 。 The biological small cycle is not completely reversible, but is in continuous development and evolution. The quantitative analysis of material flow process is an important method to study and evaluate the state of an ecosystem and predict the development and change trend of the ecosystem. The substance in the material flow will neither produce nor disappear in the flow process, and the flow is recyclable. Therefore, in ecology, the concept of material circulation is more common than that of material flow. 
