Most fungi people record in the Bos are common. The forest plan counts about 500 fungus species in the Bos, 28 of them on the national Red List.C The rare ones named in the record are mostly from one place: the peat-moss reedland on the banks of the Amstelveense Poel, which is closed to visitors.
| Species | Red List 2008 | What the record says |
|---|---|---|
| Veenmosbundelzwam Pholiota henningsii | Severely endangered. Found in only 2 atlas squares (5×5 km) nationally in 1993–2007; its spread fell an estimated 97%. Red List, p. 39 | Present at the Poel in the early 2000s, on four plots in 2004.C Found again on 26 October 2024, last recorded on 26 September 2025 (waarneming.nl). |
| Bruinschubbige gordijnzwam Cortinarius pholideus | Endangered. Red List, p. 22 | Recorded at the Poel in 2004.C |
| Zaagselhertezwam Pluteus petasatus | Endangered. Red List, p. 39 | A newcomer in the Poel survey, identified by a professional mycologist in Leiden.C |
| Kabouterwasplaat Hygrocybe insipida | Vulnerable. Red List, p. 29 | Named in the 2007 Poel survey.C |
| Prachtmycena Mycena crocata | Sensitive: very rare nationally (8 atlas squares of 5×5 km in 1993–2007), with no clear decline. Red List, p. 36 | More than a hundred on one excursion in the Bos in 2019.C 176 records on waarneming.nl. |
| Smalsporige poederparasol Cystolepiota adulterina | Not on the 2008 list | Called "uiterst zeldzaam", known from two km squares. Found in the Bos for years and taken for a common species until it was identified under the microscope.C |
The Veenmosbundelzwam. Volunteer Ger van Zanen last searched for it in 2007. After he died, nobody went back to look.C In autumn 2024 Beatrice Mantel and Inge Somhorst of the Dutch Mycological Society went in with Sasja Voet, the ecologist of the Amsterdamse BosC, crossing six ditches on a plank.C They found it two steps into the plot.C Its relatives, the bundelzwammen, live on wood; this one lives on peat moss, and nobody knows exactly why.C Besides the Bos, it is now known from the Westeinderplassen and from Weerribben-Wieden.C
C opens the passage in the source, with the cited words highlighted. The Vroege Vogels quotes come from the article and radio fragment of 3 November 2024; the radio quotes are from a machine transcript. Red List status: Basisrapport Rode Lijst Paddenstoelen 2008 (Arnolds & Veerkamp, Dutch Mycological Society), the list the ministry adopted in 2009. Plooivlieswaaiertje, Krulhaarkelkzwam and Groene glibberzwam, also found in the Bos, were on the earlier 1996 list but not on the 2008 one. The "500 species, 28 on the Red List" count goes back to a 1994 survey whose species list is not public, so we cannot yet say which 28 species it means.
A force-directed view of every relationship described below — trees (dark), mycorrhizal partners (orange), pathogens (red), saprotrophs (purple), lichens (lime), and the environmental factors the lichens read. Drag any node. Hover for details. Toggle categories on/off below.
Outside-of-the-Bos factors (Schiphol, the A9/A10, regional livestock NH₃) connect to the same lichen species you'd find on a tree-trunk inside the forest. The graph is the bridge.
Nine of the ten most-recorded fungi in the Amsterdamse Bos are wood-decomposers. The list reads less like a mycological census than like an inventory of dead wood.
| Obs. | Species | Role | Substrate |
|---|---|---|---|
| 629 | Trametes versicolor · Turkeytail | Saprotroph (bracket) | Dead hardwood — oak, beech |
| 491 | Hypholoma fasciculare · Sulphur tuft | Saprotroph (gilled) | Stumps, fallen logs |
| 422 | Coprinellus disseminatus · Fairy inkcap | Saprotroph | Rotting stumps |
| 407 | Polyporus squamosus · Dryad's saddle | Saprotroph | Dying / dead deciduous |
| 403 | Trametes gibbosa · Lumpy bracket | Saprotroph (bracket) | Dead beech |
| 398 | Ganoderma lipsiense | Saprotroph (bracket) | Old standing hardwood |
| 379 | Daldinia concentrica · King Alfred's cakes | Saprotroph | Dead ash, dead birch |
| 305 | Auricularia auricula-judae · Jelly ear | Saprotroph | Elder + dead deciduous |
| 305 | Lacrymaria lacrymabunda · Weeping widow | Saprotroph | Soil, grass, path edges (not wood) |
| 298 | Piptoporus betulinus · Birch polypore | Saprotroph (bracket) | Dead birch — host-specific |
This is what a forest looks like once it is old enough to die honestly. The 1934–1970 plantings have entered the phase where standing and lying deadwood accumulates faster than it disappears. The bracket fungi — Trametes versicolor at the top, Ganoderma, Polyporus, Piptoporus, Fomes — are the visible part of that turnover. The forest's most-recorded mycology is its compost layer.
When this dead-wood guild arrived cannot be read from these records. Most species were first recorded after 2000 because recording itself took off then, not necessarily because the fungi did: Dryad's saddle and Fairy inkcap were already recorded in the Bos in October 1976, and honey fungus (Armillaria mellea in the broad sense) in 1988. (waarneming.nl records for the Bos)
Corrected 9 October 2026: this section used to say the guild assembled "around 2005, when Armillaria mellea first appeared". The records above contradict that, so it was removed. Counts updated to the current records.
Beneath the visible canopy runs a parallel forest of ectomycorrhizal exchange. Below are 25 pairings between fungi recorded in the Bos and the trees they are known to partner with. They cluster around four hosts, and the partners barely overlap.
Not yet confirmed: these pairings come from what each species is known to do elsewhere. No document about the Bos shows each pair here, and the claim behind them is still under review. Read them as likely, not as recorded.
Oak is the centre of the underground network — more than twice the partners of anything else. Beech is the secondary hub. Birch runs a small parallel ecosystem with its own specialists, headed by Amanita muscaria (the iconic red-and-white vliegenzwam, 62 observations across the Bos). Boletus edulis appears under both oak and beech; Amanita muscaria also partners with pine. Otherwise the host-segregation is near-total.
One fungus, one tree, one hill: Tricholomopsis rutilans (Koningsmantel) is recorded in the Bos at De Heuvel (waarneming.nl), under the Corsican pines.C It is not a partner of the pine but a decomposer of dead conifer wood (Fungi of Temperate Europe), so it follows the pines' dead wood rather than their roots.
Corrected 9 October 2026: this used to call the Corsican pine the Koningsmantel's "obligate host" and list it as a partnership. It is a wood decomposer.
Pathogens are how the underground partnership ends and the dead-wood economy begins. The graph carries three such edges, and one of them is the bridge between layer two and layer three.
| Pathogen | Obs. | Host | Host obs. | Reading |
|---|---|---|---|---|
| Armillaria mellea · honingzwam | 101 | Quercus robur | 89 | Parasitises living oak, then continues as saprotroph in the dead wood it produced. |
| Heterobasidion annosum · dennenmoorder | 32 | Pinus sylvestris | 8 | Conifer root-rot. Pathogen observations outnumber host — the rot is being logged through its effect. |
| Rhytisma acerinum · inktvlekkenziekteV | 39 | Acer pseudoplatanus | 204 | Black tar-spots on sycamore leaves. A biosemiotic sign — the fungus the leaf wears. |
The Armillaria switch. The same organism is the mycorrhizal partner of Quercus robur and its eventual killer. After the kill it does not leave — it continues to live in the standing and lying dead wood, now as a bracket-fungus saprotroph. One species rotates through all three layers of this story.V
The numbers in the second row are quietly diagnostic. The conifer pathogen Heterobasidion annosum has more observations than its host: 32 vs 8. People are not logging the rot directly — they're logging dying pines and the fungus they find on them. The pathogen has become more recordable than the tree.V
A lichen flora is a slow-motion air-quality station. The Bos's reads, today, as "high regional nitrogen deposition, no recovery signal yet."V
| Obs. | Species | What the graph tags it as |
|---|---|---|
| 125 | Xanthoria parietina · groot dooiermosV | NH₃-high indicator — the orange nitrophyte on every Bos tree |
| 71 | Lecidella elaeochroma | Pollution-tolerant |
| 67 | Ramalina farinacea | Moderate N-tolerant fruticose |
| 66 | Phlyctis argena · whitewash lichen | Acidic bark, moderate pollution |
| 65 | Flavoparmelia caperata | Moderate-tolerance shield |
| 62 | Physcia adscendens | NH₃-high indicator |
| 52 | Parmelia sulcata | N-tolerant |
| 47 | Parmotrema perlatum | Moderate tolerance |
| 41 | Cladonia fimbriata · trumpet lichen | Terricolous, peat & bark |
| 35 | Evernia prunastri · eikenmosV | NH₃-low recovery indicator |
| 27 | Physconia grisea | Best NH₃ indicator (Frati 2007) |
| 27 | Candelaria concolor · candleflame | Nitrogen-tolerant |
Six nitrophytes against one recovery indicator. The species the graph tags as NH₃-high (Xanthoria parietina, Physcia adscendens, Physcia tenella, Physconia grisea, Phaeophyscia orbicularis, Hyperphyscia adglutinata) all flourish. The single species that would signal recovery — Evernia prunastri, oakmoss — sits at 35 observations, less than a third of Xanthoria.V
The clean-air bellwethers — Usnea spp., Lobaria pulmonaria, Hypogymnia physodes — have zero records in the polygon.V
This is consistent with the geography: Schiphol sits ~5 km north of the Bos, the A9 runs along its southern edge, and the A10 frames the city behind it. The Bos's lichen flora is reading those sources accurately, in slow motion — its dominance pattern matches what would be predicted by the regional NO₂/NH₃ deposition maps from RIVM.
computing…
A graph of when in the year these fungi were spotted is not a graph of when fungi fruit. It is a graph of when people walk the Bos looking for them.
The bars are the observation curve. The dashed lime line is an estimate of when the fungi actually fruit, projected onto the same 19,531-record total — averaged from European temperate-forest mycology phenology (Boddy & Heilmann-Clausen 2008; KNNV NL Paddenstoelenwerkgroep summary).V
The curve is not bell-shaped. It is a near-vertical spike in autumn. October alone accounts for 40 % of the entire dataset — against a biologically estimated ~18 %. September → October → November together: 68 % observed vs ~45 % expected. June bottoms out at 1.3 % observed, against ~5 % expected.
The shape of the gap is the project's central biosemiotic finding: this is not the forest's biology. It is the calendar of human attention. The mycology clubs run their forays in October. KNNV's Paddenstoelenwerkgroep schedules its excursions in autumn. Foragers walk after the first rains. waarneming.nl sees the resulting upload spike. Fungi that fruit briefly in May, or that persist year-round on bark, are equally present in the forest — but observers aren't there to log them.
Lichens spike in February (453) and November (510) — precisely when fungi are scarce. The same observers walk the same paths, but pivot their attention to whatever the bark is wearing rather than what is fruiting beneath. The August trough at 13 records is the year's quietest moment: observers are chasing summer fungi, not staring at lichen.
Two graphs of the same forest, the same network of observers, one running inversely to the other. The fungi calendar peaks where the lichen calendar troughs and vice versa. The forest is being read at every month of the year — but never by the same kind of looking at once.
Trees host three biological systems at once. The Bos's fungi and lichens make all three readable in the same dataset.V
The pathogens are the rotating door between layer two and layer three. Armillaria mellea can live off an oak's roots, kill it, and go on feeding on the dead wood. The same organism crosses the boundary.
It is fully into its decomposition phase — the inventory leads with bracket fungi, not pioneer species.
Its underground network is not yet documented: the fungus-tree pairings above are likely, not recorded.
Its above-ground air quality is poor, and the lichen flora reads it accurately — high-N indicators outnumber recovery indicators ~6:1.
Its rarest fungi sit outside the planted forest: on peat moss in the reedland at the Amstelveense Poel.
Every reading on this page comes either from citizen-science records (the species lists) or from sensors at the bos perimeter (the live air-quality post, ~600 m from the southern edge). The agent has no measurement inside the canopy itself.
A small in-canopy sensor stack — particulate, NO₂, CO₂, humidity — mounted somewhere in the interior of the bos would be the next honest step. It would let the agent compare what the air does at the edge with what the trees actually breathe, and would close the loop between the perimeter station and the lichen layer. Hardware exists for ~€300–500; what's missing is a host site, a power feed, and permission. Marked here as a future, not a promise.