Make Goldenrods Great Again!

Image: Wikimedia Commons

It’s important to remember that the parts of a forest or a prairie that we can see above ground are probably less than a half of the ecosystem’s total biomass; almost all of the fungal biomass is beneath the ground.

Some mycorrhizal fungi appear to only associate with certain plant species while others are less discriminating. About 80% of all plant species (including all trees) associate with mycorrhizae; the plants that don’t are the rushes, sedges, nettles, mustards, goosefoots, and pinks. Some plants are so dependent on mycorrhizae that they can’t live without them: the orchids are one such group. While most mycorrhizal relationships appear to be mutualistic, with both partners benefiting from the interaction, many orchids appear to be parasitic on the fungi!

The most parasitic orchids are the coralroots (Corallorrhiza spp.). These species are vascular plants that can no longer photosynthesize, as indicated by the fact that they are orange instead of green. Coralroot orchids parasitize mycorrhizal fungi, which form relationships with pine (Pinus spp.) trees. Thus all of the sugars the coralroot uses to fuel its growth come from the pine trees (via the mycorrhiza), and the water and minerals it needs come from the fungus (Zelmer and Smith 1995).

Ferguson, B.A., T.A. Dreisbach, C.G. Parks, G.M. Filip, and C.L. Schmitt. 2003. Coarse-scale population structure of pathogenic Armillaria species in a mixed-conifer forest in the Blue Mountains of northeast Oregon. Canadian Journal of Forest Research 33:612-623.

Song Y.Y., S.W. Simard, A. Carroll, W.W. Mohn and R.S. Zeng. 2015. Defoliation of interior Douglas-fir elicits carbon transfer and stress signalling to ponderosa pine neighbors through ectomycorrhizal networks. Scientific Reports, 5 8495. DOI: http://dx.doi.org/10.1038/srep08495

Wohlleben, P. 2016. The hidden life of trees: What they feel, how they communicate discoveries from a secret world. Greystone Books.

Zelmer, C.D. and R.S. Currah. 1995. Evidence for a fungal liaison between Corallorrhiza trifida (Orchidaceae) and Pinus contorta (Pinaceae). Canadian Journal of Botany 73:862-866.

Have you ever wondered why the only fresh mushrooms you can get in stores are button, cremini, and portabello (all different varieties and stages of Agaricus bisporus)? Or why the fancy mushrooms, like morels (Morchella spp.) and chanterelles (Cantharellus spp.) are generally only available dried? And why are those dried mushrooms so expensive anyway? Can’t they just plant them in a field like wheat? To understand the answer to these questions, you need to know a few things about what mushrooms really are.

A long time ago scientists classified all organisms as either “plants” or “animals” largely based on whether they had a means of locomotion. For this reason, mushrooms (a.k.a. fungi), were classified as “plants”. Soon, however, scientists began to realize that fungi were not actually like plants at all: they produced spores instead of seeds, and most importantly, they weren’t green. Turns out fungi don’t produce their own food like plants do; they need to “eat” plants or animals-either living or deceased. In this way, they are actually more like animals.

Some fungi are parasites on plants, animals, protists or other fungi. You may be familiar with fungal crop parasites like corn smut (Ustilago maydis), rusts (e.g. Puccinia spp.), powdery mildew (e.g. Podosphaera spp.), ergot (Claviceps purpurea) or the infamous potato blight (Phytophthora infestans). In fact, some parasitic fungi even feed on people. Ever had jock itch (Tinea cruris), athlete’s foot (Tinea pedis) or a “yeast” (Candida albicans) infection? If so, a fungus was feeding on you. Gross!

However, some fungi are what botanists call “mycorrhizal”, literally Latin for “fungus root”. Mycorrhizal fungi form symbiotic associations with various wild plants, often trees. The hyphae wrap around plants’ roots and absorb some of the sugar that the plant produces via photosynthesis. In exchange, the fungus provides the tree with water and hard to get nutrients like phosphorus. So ultimately the relationship seems to be beneficial to both parties. Many of the wild mushrooms that we love are mycorrhizal and associated with conifers like pine (Pinus spp.): pine mushrooms (aka Matsutake) (Tricholoma matsutake), delicious milkcaps (Lactarius deliciosus) and porcinis (Boletus edulis). Chanterelles are associated with several species of conifers and deciduous trees. Truffles (Tuber spp.), on the other hand, prefer deciduous trees like oaks (Quercus spp.) and hazelnuts (Corylus spp.). Some morels (Morchella spp.) will grow on decaying organic matter like the button mushrooms but other species are mycorrhizal.

Image: Delicious milkcaps (Lactarius deliciosus) are mycorrhizal associates of pine trees. ©MM

So any attempt to cultivate these species would require growing a forest of appropriate tree hosts, inoculating the soil and hoping that they will eventually produce mushrooms. Although this sounds simple, there are many mysterious things going on in the soil that we barely understand and the factors that trigger mushroom production are one of them. In my next blog, I will be exploring some of the fascinating relationships between mycorrhizal fungi and Manitoba’s wild plants.

When Manitoba became part of Canada in 1870 the stage was set for one of the largest land transformations in history. In the last 150 years nearly all of Manitoba’s wild prairies fell to the plough. The little patches that remain as ranch land, private nature preserves, and federal and provincial crown lands are home to a suite of increasingly rare organisms, among them two spectacular prairie orchids: Western Prairie Fringed Orchid (Platanthera praeclara) and Small White Lady’s-slipper (Cypripedium candidum).  Models of these two species are on display in the Manitoba Museums’ Legacies of Confederation: A New Look at Manitoba History exhibit.

In addition to their very specific habitat requirements these orchids produce seeds that are so tiny that there is virtually no nutrition available for young seedlings. In order to grow they need to form an association with a special fungus, called a mycorrhiza, which will help them get water and nutrients from the soil. The dependence of these two orchids on insect pollinators and soil fungus, along with the loss of habitat, has led to their endangerment.

It’s hard to believe that there was a time when people thought that species extinction was impossible. Humanity underestimated the power that our technology gave us over nature, and to some degree we still do. A conservation ethic did not really emerge until it was clear that there were no “lost worlds” left where rare species might still linger. The extinction of several Canadian bird species including the Labrador Duck (Camptorhynchus labradorius), Great Auk (Pinguinus impennis), Eskimo Curlew (Numenius borealis) and Passenger Pigeon (Ectopistes migratorius), largely due to overhunting, finally made Canadians understand our destructive capabilities and helped inspire the modern wildlife conservation movement. One of the benefits of confederation has been our collective will to ensure that some of Canada’s forests, tundra, prairies, lakes and ocean habitats are protected for all Canadians to benefit from–the 2-legged and the 4-legged and even the ones with no legs at all.