13.1 Ecosystem mycology

13.1 Ecosystem mycology

  • Fungi are the saprotrophs that perform the decomposition processes that contribute to organic and inorganic nutrient cycling. Clearly, fungal decomposition of dead organic matter, be it wood or other plant litter, animal dung, or cadavers and bones, is an essential ecosystem function because it maintains soil nutrient availability (see below). But there is another significant contribution along the way: fungi that decay wood soften the timber sufficiently to allow small animals (birds, reptiles, amphibians, insects and mammals) to make burrows and nests.
  • Fungal products aggregate soil particles and organic matter, improving drainage and aeration; and by so doing they create habitat diversity for many other organisms (see our discussion of glomalin in Section 6.8).
  • Fungi serve as both prey and predators of many soil organisms, including bacteria, other fungi, nematodes, microarthropods, and insects (Wall et al., 2010; Crowther et al., 2012; Menta, 2012; Ngosong et al., 2014) (see Sections 1.5, 11.2, and Chapter 15).
  • Mushrooms and truffles are consumed by many animals including large mammals like primates, deer, and bears, and many small mammals rely on mushrooms and truffles for nearly their entire food supply. The fungal mycelium is an equally important nutritional resource for many microarthropods (see Section 11.2).
  • The significance of fungi in nature means that changes in the composition and functioning of fungi in a community can have sweeping effects on the diversity, health and productivity of our natural environment; molecular methods (‘metagenomics’) are now allowing this to be studied directly (Lindahl & Kuske, 2013). Although it is species of fungi, bacteria, nematodes, and arthropods that typically dominate terrestrial ecosystems in terms of species richness, most conservation work is unfortunately concentrated on vertebrates and vascular plants. Yet there is evidence that land management practices can affect fungal diversity.

In most environments, most of the larger, showy and fleshy mushrooms that are readily seen, as well as truffles beneath the surface, are mycorrhizal. Obviously, diversity of mycorrhizal species will be influenced, if not determined, by plantings of their potential hosts. However, management practices can also affect the diversity of saprotrophic fungi; indeed, in Northern Europe intensive management of forest is associated with decline in species diversity of wood-degrading saprotrophic fungi. This appears to result from management regimes that remove woody debris from managed forests. Diversity of such species is positively correlated with both the quality and quantity of woody debris left in a forest and coarse woody debris even promotes the abundance and diversity of truffles. It is counterproductive to allow this to occur as change in the diversity and abundance of wood-degrading fungi will adversely affect the recycling of key nutrients and the provision of ecological niches in the managed community.

The result is that the influence extends beyond the plant communities to all those other organisms that interact with fungi, from insects and slugs that depend on fungi for food, to the vertebrates that eat the invertebrates. And, of course, it’s not just the commercial forests to which this applies. Amenity land (public garden and park land) is an increasingly important aspect of the urban environment which so many of us inhabit, but here, too, excessive tidiness can adversely affect the biodiversity and diminish the recreational value of the resource (Czederpiltz et al., 1999; Floren et al., 2015; Juutilainen et al., 2014; Heilmann-Clausen et al., 2017).

In Chapters 14 to 16 we will add detail to the brief descriptions given above of the ways that fungi contribute to the Earth’s ecosystems. In this Chapter we will concentrate attention on some saprotrophic activities to begin with, but our main topic will be the various associations between plants and fungi.

Updated July, 2018