In Europe Geoglossum difforme is rare and strongly confined to (often acid) semi-natural grasslands in the lowlands of northern Europe, mainly around the North Sea. Griffith et al. (2013) estimated a habitat loss of 90% over the last 75 years for the CHEG-fungi (grassland fungi of the groups Clavariaceae, Hygrocybe s.l., Entoloma and Geoglossaceae) as a whole in Western Europe (i.e. loss in seminatural grasslands, based on available information). These habitats are declining and getting bad quality due to changing agricultural practices, development projects and pollution (nitrogen deposition). In N America the species mainly grows in forests. Habitat quality has also become impaired and the decline in population size over this time could be even higher. This decline in habitat is ongoing and expected to continue over the next 50 years. GBIF lists about 500 occurrences, and about half of this in N America. The species is assumed to have a population of more than 20000 mature individuals. In Europe, the habitat loss and population decline is assumed to be >50% in 50 years (past, present and future) (approximately three generations: one generation is assumed to be about 17 years). At a global scale (i.e. Europe + N America) the decline is assumed to be 30-50% taken into account the population reported i N America (GBIF 2019). The species meets the threshold for EN (A2c+3c+4c) in Europe, and at a global scale VU (A2c+3c+4c).
G. peckianum is a synonyme (Hustad et al 2013, not applied in Index Fungorum 10.03.2019) and this name is used in some European countries (Germany, partly in UK). The status of GBIF occurences in N America compared to Europe is uncertain, but for the time being we assume that they are conspecific. Provisionally, a few occurrences from Japan and New Zealand are regarded as probably related species.
This is in Europe a species of mostly acid and often heathlike semi-natural grasslands in the lowlands and coastal areas around the North Sea, habitats which are strongly declining due to changing agricultural practices, development projects, and airial nitrogen deposition. In N America the species also occurs in forests. It is endangered (EN) in three countries and critically endangered (CR) in two countries.
The species is known from Europe, Russia and N America. In Europe it occurs in many countries in the lowland, coastal areas around the North Sea (most important: Scandinavia, UK, Germany, France). In Scandinavia the species is found most often in the southern, coastal parts of Norway, Sweden and Denmark, in the boreonemoral and southern boreal vegetation zone. Information from different continents; N America (e.g. Grund & Harrison 1967, GBIF 2019), Japan (Imai 1941, GBIF 2019) and New Zealand (GBIF 2019) makes need of molecular methods to confirm which species are involved. Meanwhile we accept the occurrence in N America, but regard the occurrences in Japan and New Zealand as probably related species, like the situation in some other earth tongues (see e.g. Hustad et al. 2013).
According to GBIF (2019) there are totally about 500 occurrences, with about the half in N America. Based on available information on trends in seminatural grasslands, Griffith et al. (2013) estimated a habitat loss of 90% over the last 75 years for the CHEG-fungi (grassland fungi of Clavariaceae, Hygrocybe s.l., Entoloma and Geoglossaceae) as a whole in Western Europe. According to the Food and Agriculture Organization of the United Nations (FAO), the area of grasslands in the EU declined by 12.8% over 13 years (1990-2003). Also other sources point to a habitat loss in seminatural grasslands of roughly 1% per year in Europe over a longer time, although the data quality is not always very good. In N America the species occurs in forests and the population trend is here poorly known, but forest habitat decline over 50 years could be in the interval 10-20%. In the seminatural grasslands of north European coastal lowland we assume a total habitat loss and population decline of >50% over the same period. As the habitat quality is also declining (especially in the main habitat – seminatural grasslands in European lowlands), this underline a high population decline. Over the whole distribution range we assume a total habitat loss and population decline of 30%-50% over the last 50 years. This trend is ongoing and expected to continue in the future.
Population Trend: Decreasing
The European population of Geoglossum difforme grows in mycologically rich but nutrient-poor semi-natural grasslands, often on acid soil in grasslands surrounded by heath. Semi-natural grasslands are rapidly disappearing due to changes in land use (see Threats and Polulation and trends). In Norway, almost all localities of the species are in semi-natural grasslands and none in forests (Jordal et al. 2016), and similar patterns are found in other countries. In N America, habitat information is sparse; in wooded ravine in Nova Scotia (Grund & Harrison 1966). The nutrient strategy is unknown but it could have some kind of biotrophy or mycorrhiza, like waxcaps (Nitare 1988).
Habitat destruction and abandoning are the main threats to seminatural grasslands including the calcareous ones. The most important process is probably withgrowing due to ceased grazing/mowing of old seminatural grasslands as part of intensification of agriculture. Further modern cultivation methods like use of fertilizers, pesticides and plowing. Also some places changed land use with the construction of roads, industrial areas, settlements etc. Decline is expected to continue, as at least the areas of seminatural grasslands are of little economic importance in modern agriculture. Most CHEG grasslands (see Population and trends) are among types redlisted as VU, EN or CR in the EU red list of habitats (Jansen et al. 2016).
The habitats should be protected against destruction due to intensification of agriculture or development plans. The maintaining of seminatural grasslands demands yearly grazing or mowing. If grazing by heavy animals destroys part of the soil, light animals like sheep should be recommended. Habitat conservation by governmental support to traditional agricultural practices is most important, this exists in many countries to maintain extensive areas of agricultural areas, and should be extended to larger areas than today. The species is suggested as a priority species in Norway (Jordal 2013).
Further ecological research is needed to clarify the nutrient strategy of grassland fungi. Management plans are needed. Habitat trends should be monitored.
The species is not known to be used.
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