Large plants are only part of the organisms that play a role in soil formation. For example, fungi are closely associated with the roots of many vascular plants by making available nutrients like nitrogen and phosphorus in a way that their host plants can utilize, and play an important role in returning organic matter to the soil by decomposing leaf litter. The list of organisms that interact with, and affect, soil is extensive, and it is these interactions that allow for the presence of paleosols to be inferred. Not only can particular organisms be interpreted from paleosols, but also ancient ecosystems. The soil interaction of plants is different from community to community. They each have distinct patterns of root traces, soil structure, and overall profile form. Identifying these features is useful for providing an overall assessment of the influence past organisms had on any particular paleosol. However, qualifying these general effects of organism activity can be difficult because the level of their expression is as related to their nature as it is to the amount of time available for soil formation. Even when fossils that are found in paleosols are understood, much more can be learned regarding their preservation, ecology, and evolution by studying the paleosols they inhabited.