Field Journal: 13-19 January 2019

The weather was perfect for mushrooms this week. Temperatures ranged from a low of 48°F (9°C) to a high of 64°F (18°C) - nice and cool, especially in the shady spots, but not nearly cold enough to freeze. We had a couple of rain showers pass through, too - enough to keep the ground wet, but not the kind of deluge that drowns out fungal growth. Coupled with the short days of midwinter, this kind of weather results in a spectacular display of big mushrooms here in Roy's Redwoods, especially around the Coast Live Oaks and Douglas-firs.

Deathcap (Amanita phalloides)

I found a troop of about a dozen big Deathcaps growing under Coast Live Oak up along the Hansen Loop Trail. This species is responsible for the vast majority of fatal mushroom poisonings worldwide. Like other Amanita species, the Deathcap is mycorrhizal: The fungus forms a mutualistic relationship with the roots of trees. Most mycorrhizal fungi that produce mushrooms have mycelium that grows on the outside of roots, and they're known as ectomycorrhizal.

Deathcaps aren't native to California - they're originally from Europe, - but they've taken to our native Coast and Interior Live Oaks (and now Pines) so enthusiastically that the Deathcaps of northern California are the largest in the world.

Grisette (Amanita vaginata)

In addition to the threat of increased mushroom poisonings, the invading Deathcaps may also be out-competing and crowding out native mycorrhizal mushrooms, like the Grisette pictured above. Grisettes are an edible Amanita that are also associated with Live Oaks here. Deathcaps probably arrived in Northern California via imported rootstock (likely Cork Oak from Europe.)

Golden Milkcap (Lactarius alnicola)

Milkcaps are one of my favorite mushrooms to find, because their gills exude a milky latex when cut; you can see a few droplets of the Golden Milkcap's white latex on the left side of the mushroom above. While they're not known to be toxic, the Golden Milkcap tastes so intensely peppery that it's considered inedible. This fungus also forms ectomycorrhizal relationships. They can pair with conifers, alders, or oaks; this one is likely associated with Douglas-fir or Coast Live Oak.

Western Jack O'Lantern (Omphalotus olivascens)

The Western Jack O'Lantern is a common sight in these parts, usually growing on Live Oaks. This fungus is saprotrophic (feeds on decaying matter) and sometimes parasitic (when its host tree is still living.) They're showy mushrooms with bright yellowy-orange gills, which you can just barely see in the photo above, and they're sometimes used as a source of pigment for dyeing fiber purple or green. The spores are bioluminescent.

Sulfur Tuft (Hypholoma fasciculare)

Sulfur Tuft is another common saprotrophic fungus that's used in dyeing (they yield a nice yellow, no mordant necessary.) They tend to show up in especially shady spots, and their yellowy caps seem to glow in the darkness. These are growing on a fallen Coast Redwood tree.

Honey Mushrooms (Genus Armillaria)

Honey Mushrooms are springing up by the dozens all over the place in Roy's Redwoods right now. These fungi are parasitic, and infection will eventually result in the death of the host tree, either by way of root damage or girdling. These are growing on a living Peppernut (California Bay Laurel.)

Honey Mushrooms (Genus Armillaria)

Honey Mushrooms can continue to live and feed off of a tree after it dies, so they sometimes pop up in unexpected places, where the decaying wood is buried under leaf litter. They usually spread from infected trees to new hosts underground via root-like rhizomorphs rather than spores.

Blewit (Lepista nuda)

Saprotrophic fungi also live in the leaf litter that covers the ground, digesting and recycling the dead plant matter there. Blewits, which have been fruiting for a few weeks here, are one of these decomposers of duff...

Lepiota magnispora

...as are fungi in the genus Lepiota. The mycelium of these fungi - the threadlike structures that produce the mushroom & continue to live on after the mushroom has decayed - live in the leaf litter and topsoil. Saprotrophic fungi are a key part of the cadre of organisms (including yeasts, bacteria, worms, slugs, snails, and millipedes) that recycle dead plant material back into nutritive soil.

Western Witch's Hat (Hygrocybe singeri)

There's some debate about the eating habits of the Waxy Caps (genus Hygrocybe.) They've long been thought to be saprotrophic, but a couple of recent studies have suggested that at least some Waxy Cap mycelium is endophytic - that is, it lives inside a living plant, rather than on the outside (like the ectomycorrhizal Deathcaps.) Both studies (Tello et al. 2013 and Halbwachs et al. 2013) note the presence of Waxy Cap DNA inside plant roots.

Hygrocybe acutoconica

More recent research (Halbwachs et al. 2018) takes a closer look at carbon and nitrogen isotopes in Waxy Caps and points to a couple of interesting conclusions:

  1. Waxy Caps have a nitrogen isotope signature consistent with mycorrhizal fungi, and their carbon isotopes look more like biotrophic fungi (those that rely on a living organism for food) than saprotrophic fungi. This suggests that they may be endomycorrhizal - a fascinating idea, since most endomycorrhizae don't produce mushrooms.
  2. Nitrogen analysis of Waxy Caps further suggests that their source of nitrogen is unusual compared to other fungi. Test plots showed that application of nitrogen and lime fertilizer suppressed Waxy Cap mushroom development. This may be due to the fact that Waxy Caps are in direct competition with bacteria for nitrogen sources in the soil, and the sudden influx of fertilizer causes such an increase in bacterial growth that Waxy Caps are out-competed for nitrogen.
California Slender Salamander (Batrachoseps attenuatus)

The abundance of big, beautiful mushrooms means I haven't had much time to turn over logs to look for millipedes, molluscs, and salamanders. Luckily, my daughter's been photographing salamanders in Roy's Redwoods for a school project, and she kindly gave me permission to share this lovely California Slender Salamander with you. We've also seen Arboreal Salamanders (Aneides lugubris) and lots of Yellow-Eyed Ensatinas (Ensatina eschscholtzii xanthoptica.) Notably absent are the Rough-Skinned Newts (Taricha granulosa) that I usually spot when the seasonal creeks start running here. I'll be keeping an eye out for them.

Previously: 6 - 12 January 2019

Next: 20 - 26 January 2019

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