8/21/22: Forest friends
A week out in the forestry plots led to many run-ins with the creatures of the forest. More fungi. Some amphibians. One human volunteer... After finishing this month's minirhizotron scanning session, I checked in with the maple trees that we saved from the tumultuous depths of the kiddie pool just but seven days ago. Who will survive? Who will root away with the final rose? Who will win the grand prize of a hundred thousand dollars and a lifetime of reality Tree.V. (ya know, the plant version of T.V.) guest appearances? Keep reading to find out. Plus, another look at mushrooms and and the importance of native plants for our butterfly buddies!
Data visualization and our waterlogged trees
After taking photosynthesis measurements of the maples this Wednesday, I had 8 complete sessions for both the maples and magnolias. The data shows a clear pattern of the waterlogged trees' assimilation rates dropping dramatically after waterlogging was initiated. The two species that were known to be more tolerant, silver maple and star magnolia, are also showing higher rebounds in their assimilation rates since being taken out of the pools. The next challenge was exploring ways to plot this data that clearly showed the relationships between waterlogging, assimilation rates, and time.
In the four figures below you can see the assimilation rates at different dates for each species, with separate lines representing control and waterlogged trees.
Many online resources are available for R and other programming languages. They can help you at every point of your data analysis. An online book that I have found extremely helpful is R for Data Science. It breaks up data science into six main stages: importing, tidying, transforming, visualizing, modeling, and communicating your data. This week I focused on the visualization component by playing around with different graphing options for how we can look at the comparisons between the waterlogged trees and their non-treated counterparts.
More on mushrooms
Last week you saw some examples of different species of mushrooms we found in the forestry plots. Before introducing you to any new forest friends, perhaps it would be best to give you a summary on why fungi are important for forest health and how we investigate their impact in the Root Lab.
Almost all the plants around you form a necessary symbiotic relationship with fungi. This relationship is called a mycorrhizal association ("myco" meaning fungi, "rhizo" meaning root). Fungi offer water and nutrients such as Nitrogen, Phosphorous, and Potassium to plants. They are in turn paid in carbohydrate currency by their green brethren. The benefits don't end there, mycorrhizal fungi also protect plants from other pathogens (not only in the roots, but also in the plant's foliage), increase plant resistance to heavy metal toxicity, and increase drought tolerance. What a list, I hope all of our besties keep us hydrated and heavy metal free too.
There are two main types of mycorrhizal fungi: ectomycorrhiza (EM) and arbuscular mycorrhiza (AM). Host specific types such as orchid mycorrhiza and ericoid mycorrhiza (forms associations with plants in Ericaceae family) also exist, but that's a rabbit-hole we can venture down in a future blog post. The differences in form and function of EM and AM fungi are pretty straightforward. EM fungi form a sock-like sheath over fine roots. Remember the mycelium I mentioned last week? The underground fungal network of threads? The individual segments making up the mycelia are called hyphae. For EM fungi, their hyphae penetrate the plant root wall, but don't enter into the root cells. AM hyphae make a longer trek inside their host's root all the way into the root cell. EM fungi more than compensate for their short trip into the root by traveling far and wide outside of the root, foraging the surrounding soil for resources. AM fungi prefer to stay close to their plant partner and don't extend as far into the soil. Another notable difference between mycorrhizal types is their reproductive strategies. EM fungi can produce macroscopic fruiting bodies (mushrooms!), whereas AM fungi produce spores within the soil and/or inside plant roots.
Ectomycorrhiza and arbuscular mycorrhiza colonization strategies are shown here. Check out this article in nature to learn more about the differences between EM and AM fungi.
All of our forestry plots are monospecific. This means that they contain only one tree species. For example, the white pine plot is only populated by white pine trees. We know that white pine is associated with EM fungi. In fact, all trees in the Pinaceae family (pines, spruces, firs, hemlocks, and more) associate with EM fungi. The same can be said for oak species. Remember the term "phenology" mentioned in a previous post describing how we use minirhizotron scanners to look at seasonal growth patterns of roots throughout the year? We are looking at fungal phenology using the same images. In addition, we can estimate colonization rates and how those differ between plots and soil depths. How does fungal abundance change throughout the season? Do mycorrhizal associations increase or decrease in response to environmental stressors such as drought? These are questions we can explore!
Check out some of the fungal friends we came across this week. Not all of these are ectomycorrhiza fungi. Some may be saprotrophic, which mean they feed on dead and decaying plant material.
The importance of native plants
Did you ID the butterflies in last week's update? On the left we had a giant swallowtail (Papilio cresphontes), and the blue dude on the right was a pipevine swallowtail (Battus philenor). Speaking of the pipevine swallowtails, in their larval stage they are very picky eaters. You know your three-year-old cousin who subsists on Goldfish crackers and string cheese? Pipevine caterpillars are even less dietarily adventurous than them. In Illinois, the only native options on the menu are three plants in the birthwort family: Dutchman’s pipe (Aristolochia durior), wooly Dutchman's pipe (Aristolochia tomentosa), and Virginia snakeroot (Aristolochia serpentaria).
Below you can see some pipevine swallowtail caterpillars on a Dutchman's pipe vine that they have almost fully devoured.
Birthworts are perennials that tend to grow as herbs, shrubs, or climbing vines. They have funky looking flowers whose shape resembles the human birth canal. Most interestingly, these plants have been used for the past 2,500 years in herbal medicines despite their high toxicity and carcinogenic effects. Of course these impacts were unknowable when Theophrastus, a student of Aristotle, first documented birthwort's medicinal uses around 300 BC (Grollman & Marcus, 2016). Still, the irony can be appreciated, and maybe there should have been an ancient Greek version of the FDA hanging around to test and approve the latest herbal remedies. If there was a GHA (Greek Herb Administration), and they somehow happened to have modern molecular technology thousands of years ahead of its time, they would have found the phytochemical responsible for birthwort's toxicity, aristolochic acid (AA). To read more about the history of AA and the tragic events that led to its discovery, check out this article.
So why, you ask, would pipevine swallowtails prefer to munch on toxic leaves? For protection! Through evolution, the caterpillars have adapted to accumulate AA in their tissue and even retain high amounts in their adult butterfly stage. This protects them from natural predators. This crucial function of AA in the survival of pipevine swallowtails is the reason they have highly specialized diets, and butterflies will only lay their eggs on the aforementioned birthwort species. This is all to say that many organisms, especially insects, depend on specific native plants to maintain their populations. This extremely informative and cool website I came across, West Cook Wild Ones, offers a great guide to butterfly gardening. The page I linked pairs over a dozen butterfly species with their native plants and also offers plant care suggestions.