Mushrooms

As was just noted, mushrooms are the fruiting bodies of certain types of fungi. Most of the biomass of these fungi consists of fine, thread-like hyphae, which grow extensively throughout the organic-rich substrate of their ecosystem. These fungi periodically develop spore-producing, reproductive structures known as mushrooms, under conditions of a favorable environment in terms of temperature and moisture, coupled with the accumulation of sufficient energy and nutrient reserves to support the reproductive effort. It may take years for these favorable circumstances to develop, and consequently mushroom populations in forests, prairies, fields, and other habitats can be highly variable in abundance.

Species of mushroom-producing fungi exploit various types of microhabitats. The most important of these are the surface soil and organic litter, large-dimension woody debris, mycorrhizae, and animal dung. These are discussed below:

1. The hyphae of many species of fungus grow extensively through the soil and surface organic matter, such as the forest floor and the organic mat of prairies and savannas. These hyphae are the vegetative tissues of saprophytic fungi, which are an important component of the decomposer food web of their ecosystem.
2. Many other species of fungi are saprophytes that grow in decaying wood, such as logs and branches lying on the forest floor, standing dead trees (these are known as "snags"), and rotting heartwood of living trees. Some of these fungi become significant economic "pests," for example, by causing dry-rot of the wooden components of buildings.
3. Many species of fungus grow in a close association with the roots of higher plants, in a mutualistic symbiosis known as a mycorrhiza. The mycorrhizal mutualism is very important to the nutrition of the plant, because of the greatly enhanced access to nutrients that is provided, particularly to phosphate.
4. An additional habitat that may be exploited by mushroom-producing fungi includes piles of animal dung, especially the organic-rich manure of herbivores. These are known as coprophilous fungi.