Summer of Fungi: Looking at Macrofungi Species Richness in Hemlock vs. Birch Forest

1 Sep

My summer research project with fungi began with my interest in the decline of the Eastern Hemlock (Tsuga canadensis) forest because of two exotic invasive insect species: the Hemlock Woolly Adelgid (Adelges tsugae) and Elongate Hemlock Scale (Fiorinia externa). These two insect pests are likely to cause the die-off of evergreen Eastern Hemlock forests in New England in coming years, resulting in a transition of the dominant tree type in many areas to deciduous Black Birch (Betula lenta). With the help of my SURF advisor Jesse Bellemare, I decided to look at macrofungi species richness in Hemlock versus Birch plots at the MacLeish Field Station and a site in Chesterfield MA. Fungi interact very closely with the trees in their habitat either as mycorrhizae (a symbiotic relationship in which fungi help increase trees’ absorption capabilities), parasites or as decomposers of wood debris and leaves. Given these close interactions, the decline of the Eastern Hemlock could have substantial effects on the fungi community of the Hemlock forest and how nutrients are cycled through these ecosystems.

One potential difference between the fungi communities of Hemlock and Birch forests is how dead wood will be decomposed.  There are two major types of wood decomposition that fungi use to extract nutrients from wood.  Brown rot fungi species are typically associated with conifer forests.  While feeding on dead conifer wood, these fungi do not degrade lignin, a key component of plant cell walls, leaving the wood somewhat intact and retaining organic carbon.  In contrast, white rot fungi species do degrade lignin, leaving highly decomposed wood behind. A change in forest type from coniferous Hemlock to deciduous Birch could change the principle form of decomposition carried out by fungi.  This change would have dramatic impacts on the amount of carbon stored in soil and other ecosystem processes.

The learning curve for identifying mushrooms or fungal “fruiting bodies” was steep. The terminology was bizarre, featuring terms like umbo (a central hump) and squamulose (having small scales), and the sheer number of species that I found in the study plots was initially overwhelming. I quickly realized that making spore prints would be a valuable tool for identification. Using a large piece of glass and plastic drinking cups, I left mushroom caps gill or pore side down overnight to shed their spores, yielding some lovely spore “prints” on the glass below them. These ranged in color from pure white to rusty brown. Once I started making spore prints and gaining more familiarity with the common species, identifying species became like a puzzle, putting the various pieces of information together yielded a genus or species. Crumbly flesh, white spores, red cap probably a Russula species. Basal bulb and veil probably an Amanita.

Amanita specimen.

Amanita specimen.

Spore print.

Spore print.

This first part of the summer was fairly quiet in terms of mushroom diversity, but around mid July the tame, small surveys I had been taking suddenly changed. Rain is a major determinant of fungal fruiting and the wet summer contributed to a massive fruiting. Instead of collecting 20 fruiting bodies per survey I was collecting 92, and sometimes they were very wet and slimy. It was around this time that I became familiar with the smell of rotting mushrooms, which is often very similar to the smell of rotting fish. Some of my samples were also infested with small invertebrates, like springtails, maggot-like worms and slugs. I was convinced on more than one occasion that I was going cause a lab infestation!

It was also around this time that I began to find some interesting and beautiful fruiting bodies. It was exciting to find unusual new species yet to occur in my surveys: coral fungi with delicate branches, small brain-like mushrooms, big colorful boletes that turned bright blue when damaged and Lactarius species that gushed latex when cut.

Lactarius specimen.

Lactarius specimen.

Spathularia velutipes.

Spathularia velutipes.

Ultimately my surveys revealed that the Birch and Hemlock did not differ in terms of overall species richness in the early- to mid-summer. This finding does not mean, however, that some macrofungi species are not dependent on Hemlock or Birch. In the fall semester, I plan to examine the frequencies with which abundant fungi species occur in Hemlock and Birch plots.

-Aliza Fassler is a sophomore student considering a major in Biology. She is originally from Greenfield, MA and loves being outside (even in the winter). Aliza is excited to continue working in the Bellemare lab this fall.

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