Waxcap grassland

Waxcap grassland is a type of short-sward, nutrient-poor grassland that supports a diverse range of larger fungi, particularly waxcaps (species of Hygrocybe and related genera), which are characteristic of such habitats. Waxcap grasslands are principally found in Europe, where they are declining due to agricultural practices. Consequently, the fungal species are of conservation concern, and efforts have been made in the United Kingdom and elsewhere to protect both the grasslands and their characteristic fungi. Thirty European species of waxcap grassland fungi are currently assessed as globally "vulnerable" or "endangered" on the IUCN Red List of threatened species.

The association of waxcaps with unimproved (nutrient-poor) grasslands was first noted in 1949 in the Netherlands, but current interest was stimulated by a series of papers published by Dutch mycologist Eef Arnolds in the 1980s. Arnolds not only confirmed the association of waxcaps with unimproved grasslands, but also noted the rapid decline of such habitats in the Netherlands. Similar studies were subsequently undertaken elsewhere in Europe, initially in Denmark and the United Kingdom.

Waxcap grasslands are characterised by being unimproved (unfertilised and nutrient-poor), with a short sward due to grazing or mowing. They are also moss-rich and long-established, not having been recently sown. They occur in both upland and lowland areas and may be found on acidic, neutral, or calcareous soil. They support a wide range of characteristic larger fungi, but may not be equally species-rich in plants.

Larger fungi characteristic of waxcap grasslands include agarics (gilled mushrooms) belonging to the genera Cuphophyllus, Gliophorus, Gloioxanthomyces, Hygrocybe, Neohygrocybe, and Porpolomopsis (waxcaps), Entoloma (pinkgills), Dermoloma, Pseudotricholoma, Camarophyllopsis, and Hodophilus; clavarioid fungi (club and coral fungi) belonging to the genera Clavaria, Clavulinopsis, and Ramariopsis; and earthtongues belonging to the genera Geoglossum, Glutinoglossum, Microglossum, and Trichoglossum.

In 1995, Rald proposed a simple method of counting the number of waxcap species present at a given site in order to assess its value as a waxcap grassland. He suggested that sites with 17 or more species were of national importance, those with 9–16 species were of regional importance, those with 4–8 species of local importance, and those with 3 or fewer of no importance. This system was modified by Rotheroe and others to include all the characteristic macrofungi, not just waxcaps.

Known as the "CHEG" system, this is widely used in survey work today. The acronym "CHEG" stands for the main groups of relevant fungi: C - the clavarioid species (club and coral fungi); H - species of Hygrocybe and related genera (waxcaps); E - Entoloma species (pinkgills); and G - the geoglossoid fungi (earthtongues). More recently the modified term "CHEGD" has been used to include species of Dermoloma, Pseudotricholoma, Camarophyllopsis, and Hodophilus which also inhabit these grasslands.

Over the past 75 years, more than 90% of unimproved grasslands in Western Europe have been lost, primarily due to agricultural intensification through ploughing, reseeding, manuring, and the application of fertilizers and other chemicals. The maintenance of a short sward through grazing or mowing and the subsequent removal of cuttings has also been shown to be important for waxcap fruiting. It has been found that hay cutting in July, followed by aftermath grazing or mowing to 3 cm is optimal. In 1988, Arnolds estimated that only around 200 hectares of unimproved waxcap grasslands remained in the Netherlands.

As a result, both the unimproved, nutrient-poor grasslands and the larger fungi that are characteristic of such grasslands are of conservation concern. Currently, 30 waxcap-grassland species are classified as globally "vulnerable" or "endangered" on the IUCN Red List of Threatened Species.