The story of Coastal Douglas-fir forests: All about fungi

There is a mysterious world of diversity within the world of fungi; in the widely understudied CDF zone this mystery runs deeper than in many other regions of BC.

Coastal Douglas-fir forests (CDF) and associated ecosystems are widely known for their charismatic megaflora like towering western redcedars and twisting arbutus, yet these places are teeming with diversity under the forest canopy that often goes unnoticed. Fungi are widely varied and profoundly important for supporting and maintaining ecological processes from the micro to the macro scale. Yet, the true diversity of these species in the CDF zone remains poorly understood. As development pressure continues to rise and habitat fragmentation grows throughout the region, the opportunity to uncover the ecological histories of the landscape dwindles. 

In this article, Dr. Shannon Berch and Dr. Paul de la Bastide explain some of the deep relationships between fungi and other species and why it is so essential that we learn more about them.

Can you speak to the diversity of fungi species within the CDF? What are some characteristic species?

There have been few dedicated studies of fungal biodiversity in the CDF zone, partially due to the challenge of identifying undisturbed sites for long-term study. However, there has been one dedicated survey of macrofungi on Observatory Hill (site of the Dominion Astrophysical Observatory), located in Saanich, BC. This site is relatively undisturbed and is considered typical CDF zone habitat, including a number of rare plant species and a range of plant communities, from Douglas-fir dominated forest to Garry oak habitat. 

Starting in 2004 and lasting for many years, annual surveys of the 75-hectare study area by Oluna and Adolf Ceska identified about 1,166 species of fungi, with species of Cortinarius and Inocybe particularly abundant. These genera are in need of further study to document their occurrence and describe new species that likely exist within the CDF and other forest zones. Gilled mushrooms (order Agaricales) like Cortinarius and Inocybe spp. are an important component of the mycota in the CDF, along with other diverse fungal genera, such as Galerina, Mycena, and Russula, which are the focus of current molecular and taxonomic studies to describe their diversity in western North America. 

Jumbo gym, illustrated in photo 1, is a wood decay fungus found in the CDF and neighbouring forest types that forms clusters of huge, yellow-orange mushrooms. It is one of our largest and most noticeable forest mushrooms. 

Orange mushrooms growing on the side of a tree.
Gymnopilus ventricosus or “Jumbo gym” is a gilled mushroom in the order Agaricales. Photo by Paul De La Bastide.

What is the best time of year for seeing fungal sporophores?

Fungal sporophores (fungal structures that release sexual spores) vary greatly in their morphology and abundance; they may appear as mushrooms, puffballs, truffles, polypores and many other macroscopic forms. You are most likely to see sporophores in the autumn (late September to November) as temperatures decline and forest soils are refreshed with autumn rains, after the dry summers we typically experience in the CDF zone. If temperatures remain above freezing during the winter months, you may continue to find all sorts of sporophores in the forest, although they will be less abundant. 

White mushrooms growing in the grass.
Agrocybe praecox, or Spring Agrocybe, are some of the earliest appearing mushrooms in this region, typically first seen in spring as their common name suggests.  Photo by Paul De La Bastide.

Some fungi will produce perennial sporophores known as polypores or bracket fungi, and these may be seen year-round, growing on trees and fallen logs for a number of years as they decompose woody debris in a forest. Some species of fungi will consistently produce abundant sporophores year after year, while others will be seen only rarely. Sporophores are short-lived structures that tell us where a fungal species is living. Most of the time, fungi are hidden from our view, living as a mycelium somewhere in the soil, inside a host, or often in a woody substrate, depending on their ecological niche. It is not really known whether there is a direct correlation between the quantity of that fungal mycelium and the abundance of sporophores we see in the forest. It is also possible that the ecological role of a fungus and its stage of development may influence the formation and abundance of sporophores. The life cycles of many fungal species remain poorly understood, providing ample opportunities for future studies by enthusiastic mycologists!

What role do fungi play in maintaining ecological integrity?

Fungi have many ecosystem functions. Decomposer fungi break down dead organic matter including trees, twigs and leaves, animal carcasses and old mushrooms, thus releasing nutrients and sequestering carbon in forms that resist further decomposition. Mycorrhizal fungi of many types (ectomycorrhizal, ericoid, orchid, monotropoid, and arbuscular mycorrhizal), intimately interact with living plant host roots; generally, they provide nutrients and water from the soil in exchange for carbon from the photosynthetic plant host. One exception to this rule is found in plants called ghost pipes. These plants are not green because they lack the pigment chlorophyll. This means that ghost pipes cannot make their own energy through photosynthesis, so they rely on fungi that are mycorrhizal with trees such as Douglas-fir for energy transported from the green tree to the fungus and from the mycorrhizal fungus to the ghost pipe. They are therefore considered a mycoheterotrophic plant, supported by energy from green plant species delivered via the mycorrhizal mycelium that links the two plants. 

Orange mushroom growing on the forest floor.
Aleuria aurantia otherwise known as Orange Peel fungus has been understood to be a decomposer, but an isotope study revealed that it also may have a mycorrhizal function in the ecosystems where it occurs. Photo by Paul De La Bastide.
Conk mushroom growing on the forest floor.
Phaeolus schweinitzii also known as Dyer’s polypore, Dyer’s conk, or Schweinitzii Butt Rot is a tree pathogen. By Paul De La Bastide.

Parasitic fungi live within living hosts, gaining both energy from the host in the form of sugar and a safe, competition-free environment in which to live. Endophytic fungi occupy the living leaf tissue of host plants, taking sugar from the host; with most studied endophytic fungi it is unclear what the fungi might be providing to their hosts, although some fungi seem to help their host to suppress plant pathogens and repel herbivores. Pathogenic fungi attack living plants, animals, and other fungi, taking energy and carbon without providing benefit to the host, which ultimately leads to host decline and possibly death. The Dyer’s polypore, illustrated in photo 4, can be used to produce pigments for dyeing wool. Depending on the process used, the dyer’s polypore can dye wool bright yellow or gold, dark moss green with yellow tones, or a rich chocolate brown. Other fungi form lichens with a complex assembly of other organisms including cyanobacteria or microscopic algae, yeast and bacteria. 

Are there many fungi species endemic to the CDF?

Although a recent study of Garry oak mycorrhizal fungi highlighted the presence in the CDF of a community of fungi unique to oak and not shared with conifers, in fact, very little is known about the fungi in the CDF. Research in the neighbouring Coastal Western Hemlock zone on southern Vancouver Island has discovered that many important mycorrhizal associates of western hemlock are endemic to this region. Cosmopolitan species certainly are found here, but the endemic species play especially important roles in their host’s nutrition. Chances are good that further investigation of Garry oak mycorrhizal fungi will reveal species found only within the range of native west coast oaks. And that’s just the mycorrhizal fungi of oak. The many other plant species unique to the CDF associate with other kinds of mycorrhizal fungi and nothing is known of their diversity. Decomposer fungi, pathogenic fungi, and parasitic fungi are all native to the CDF and there is almost nothing published for the CDF on these essential parts of the ecosystem.

Mushrooms growing on the side of a log.
Trametes versicolor, popularly known as Turkey tail, is far from endemic to the CDF zone. It is one of BC’s most common and widespread polypores. Photo by Paul De La Bastide.

What is the likelihood that there are undiscovered species of fungi in the CDF region?

Chances are also good that there are undiscovered species of fungi in the CDF. We know that there is a community of mycorrhizal fungi unique to oak. Recently, Cortinarius vinaceobrunneus was described based on collections made with Quercus garryana in Washington state and in BC from the Cowichan Garry Oak preserve in Duncan. This and other recent descriptions of species new to science are likely just the tip of the iceberg. Many of the fungi detected in Garry oak mycorrhizas using DNA sequencing techniques found no matches in international sequence databases; this might mean that these sequences represent species new to science or species that have not yet been sequenced elsewhere and added to the databases. Either way, these are fungi that have largely been ignored and require further research. In Oregon, where much more research has been done, two truffle species were recently described uniquely from Garry oak. Garry oaks in urban areas have also been shown to harbour mycorrhizal fungi unintentionally introduced from Europe on horticultural stock. This includes, unfortunately, the Death Cap mushroom (Amanita phalloides), now found with urban Garry oaks and with Garry oaks growing far from urban influences. 

Are there any management recommendations you might have to maintain fungi diversity in this region?

Any considerations for the support of fungal diversity overlap closely with practices that will maintain the overall biodiversity of a CDF ecosystem. As a general rule, a forest or meadow ecosystem with a diverse plant community, uneven age composition of trees, a variety of woody debris, and microsite diversity will support a diverse fungal community that contributes to many vital ecosystem functions. Also of importance, disturbance is a part of any natural forest or meadow (e.g., fire, tree disease, the activities of resident wildlife) and the heterogeneity these events generate will in turn create a broader range of habitat for fungal species.

For example, controlled burns were routinely practiced by Coast Salish Peoples for thousands of years to maintain Garry oak meadows on southern Vancouver Island and limit the encroachment of competing shrub and tree species. This was done to favour the growth of understorey plant species, particularly common camas (Camassia quamash), whose edible bulbs are an important food crop. Over the past century, fire suppression has contributed to a decline in diversity and the gradual loss of such ecosystems, as encroaching native and invasive plant species dominate the understory of meadow habitat. Fortunately, periodic fires have been recognized as a natural occurrence on these sites and low intensity prescribed burns have been used on some protected Garry oak meadow habitats (e.g., the Cowichan Garry Oak Preserve) to restore native plant biodiversity. 

White mushroom growing in some moss.
Pseudohydnum gelatinosum or Toothed Jelly Fungus, is a member of the order Auriculariales which are understood to be wood decomposers. They are an essential part of forest ecosystem processes. Photo by Paul De La Bastide.

On the other end of the spectrum, urban forests that are small in area and fragmented, lack plant diversity and contain an abundance of invasive or non-native plant species, will typically exhibit a lower diversity of fungi taxa. The same will be true for forested lands managed for tree harvest on short rotations; these habitats display low plant diversity, usually have even-aged stands of only a few tree species and a more homogeneous habitat structure with less woody debris.

The predominance of private lands in the CDF zone and existing pressures for land development make the preservation of surviving forests and Garry oak habitats a major challenge. A big part of this equation will be public engagement to bring a greater awareness of and value to biodiversity protection in the remaining relatively intact lands, thereby providing benefits to all members of the biota in the CDF zone. It is likely that management strategies to support a more diverse flora and fauna will in turn provide benefits to the mycota of this zone. These management practices will overlap with the immediate priorities of reducing the impacts of climate change in the CDF. These practices will include supporting biodiversity in both urban and rural settings, managing forests, savannahs and meadows for water conservation and carbon sequestration, and favouring longer rotations and selective logging practices in forests managed for timber, none of which are new concepts in forest management.  

About the authors

Dr. Shannon Berch is Emerita Research Scientist with the BC Ministry of Environment, Associate Member, Botany, UBC, Adjunct Professor, Land and Food Systems, UBC and a Founding Member of the South Vancouver Island Mycological Society and the Truffle Association of BC.

Dr. Paul de la Bastide is a Research Associate in the Centre for Forest Biology, Department of Biology, at the University of Victoria. He has a keen interest in studies of symbiotic, endophytic and pathogenic fungi living in forest ecosystems and beyond. 

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Coastal wolf with a salmon in its month.
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