Conservation Of Saprotrophic Fungi In Europe

Saprotrophic basidiomycetes are found in most terrestrial habitat types with forests being particularly species rich. Natural processes constantly affect populations, and species naturally go extinct from time to time, even in the absence of human intervention, while others split into several genetic distinct lineages resulting in the formation of new biological species.

The human use of European landscapes through recent millennia has dramatically influenced these processes. Most natural habitats have decreased in quality or quantity due to clearing of woods, agriculture, urbanisation and industrialisation. Sometimes humans have also created new habitat types or have increased the abundance of naturally rare habitats to the benefit of certain groups of fungi. For instance, the expansion of animal husbandry through the last 5,000 years strongly increased the extent of grasslands to the benefit of dung and grassland fungi. Similarly, the current use of woodchips in horticulture has lead to a strong increase for a number of saproxylic fungi, including invasive alien species (Shaw et al., 2004). Interactions between human and natural processes affecting fungal habitats are complex, and it is not feasible to distinguish sharply between natural versus artificial habitats. Rather these form a continuum from "virgin" habitat types (e.g. virgin forests) through semi-natural habitats (e.g. most grasslands and wooded meadows) to highly artificial habitats (e.g. crop fields, wood-chip covered garden strips). In this context also the time factor is important. Habitat types with a long local or regional history are more likely to host a distinct suite of locally adapted habitat specialists compared with more recent, typically human introduced habitats. Currently the most important forces affecting decomposer basidiomycetes in Europe are:

1. Intensified silviculture (removing of dead wood and veteran trees, conversion from native to exotic tree species, drainage of swamp forests, diminished forest grazing).

2. Intensified agriculture ("improving" grasslands by fertiliser additions and conversion to arable crops).

3. Decreasing animal husbandry in low fertile areas leading to forest re-growth.

4. Increased nitrogen deposition.

5. Climate change.

These factors affect fungal communities directly or indirectly in different ways. For the two latter factors probable effects on decomposer basidiomycetes in the field are uncertain, though there is evidence of changes in fruiting patterns as a result of climate change (Chapter 5). Nitrogen deposition is known to affect ectomycorrhizal species considerably (e.g. Peter et al., 2001a; Avis et al., 2003), and fertilisation experiments have even shown effects on decomposer communities

(Rühling and Tyler, 1991). Below we review conservation approaches for two important groups of basidiomycetes, grassland and saproxylic saprotrophs which include many species believed to be decreasing in Europe.

3.1 Grassland Species

Most grasslands can be considered semi-natüral because they depend on management to prevent them developing into scrub or forest. The history of grasslands in Europe, before the first animal husbandry has been much discussed (e.g. Svenning, 2002), but there is little doubt that the habitat types reached a maximum in the pre-industrialised farming era, from the 15th through to the beginning of the 20th century. Since then semi-natural grasslands has decreased dramatically in many countries (e.g. Bruun and Ejrn^s, 1998).

Without the use of artificial fertilisers most dry grasslands are nutrient poor because nutrients (phosphorus and nitrogen) are removed by the grazing animals. Grasslands may have a continuity of hundreds or maybe even thousands of years. Characteristic fungi of dry grasslands with long continuity are not least wax-caps (Hygrocybe, including Camarophyllus) and Entoloma species, especially of subgenus Leptonia, each group with ^50 species occurring in grasslands. In addition, a number of club fungi (Clavaria, Clavulinopsis, Ramariopsis) and Geoglossaceae (Geoglussum, Microglossum, Trichoglossum) occur in grasslands. Many other groups may be represented in dry grasslands, like puff balls and species of Galerina, Agaricus and Macroleptiota, but such species generally have broader ecological amplitudes or are associated with more nutrient-rich grassland types, and are not considered as indicators of valuable grassland sites with a long continuity.

In most European countries, the wax-caps are well investigated, and wax-cap species are rarely recorded as new to a country. The checklists of Entoloma species, however, are still incomplete in most countries. Most Hygrocybe species fruit in autumn, and continue until early winter. Some Hygrocybe species fruit from summer, but only when it rains. Entoloma species most commonly fruit in summer, and therefore their fruiting is less constant.

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