Photographic Art

Today's BPotD is the second in the series of BPotD's contribution to the 2010 UBC Celebrate Research Week.

Lindsay organized today's entry, selected the links, and introduces Dr. Suzanne Simard:

Dr. Suzanne Simard is a professor with the UBC Faculty of Forestry, where she lectures on and researches the role of mycorrhizae and mycorrhizal networks in tree species migrations with climate change disturbance. Networks of mycorrhizal fungal mycelium have recently been discovered by Professor Suzanne Simard and her graduate students to connect the roots of trees and facilitate the sharing of resources in Douglas-fir forests of interior British Columbia, thereby bolstering their resilience against disturbance or stress and facilitating the establishment of new regeneration.

Dr. Simard writes:

Mycorrhizal fungi form obligate symbioses with trees, where the tree supplies the fungus with carbohydrate energy in return for water and nutrients the fungal mycelia gather from the soil; mycorrhizal networks form when mycelia connect the roots of two or more plants of the same or different species. Graduate student Kevin Beiler has uncovered the extent and architecture of this network through the use of new molecular tools that can distinguish the DNA of one fungal individual from another, or of one tree's roots from another. He has found that all trees in dry interior Douglas-fir (Pseudotsuga menziesii var. glauca) forests are interconnected, with the largest, oldest trees serving as hubs, much like the hub of a spoked wheel, where younger trees establish within the mycorrhizal network of the old trees. Through careful experimentation, recent graduate Francois Teste determined that survival of these establishing trees was greatly enhanced when they were linked into the network of the old trees.Through the use of stable isotope tracers, he and Amanda Schoonmaker, a recent undergraduate student in Forestry, found that increased survival was associated with belowground transfer of carbon, nitrogen and water from the old trees. This research provides strong evidence that maintaining forest resilience is dependent on conserving mycorrhizal links, and that removal of hub trees could unravel the network and compromise regenerative capacity of the forests.

In wetter, mixed-species interior Douglas-fir forests, graduate student Brendan Twieg also used molecular tools to discover that Douglas-fir and paper birch (Betula papyrifera) trees can be linked together by species-rich mycorrhizal networks. We found that the mycorrhizal network serves as a belowground pathway for transfer of carbon from the nutrient-rich deciduous trees to nearby regenerating Douglas-fir seedlings. Moreover, we found that carbon transfer was enhanced when Douglas-fir seedlings were shaded in mid-summer, providing a subsidy that may be important in Douglas-fir survival and growth, thus helping maintain a mixed forest community during early succession. This is not a one-way subsidy, however; graduate Leanne Philip discovered that Douglas-fir supported their birch neighbours in the spring and fall by sending back some of this carbon when the birch was leafless. This back-and-forth flux of resources according to need may be one process that maintains forest diversity and stability.

Mycorrhizal networks may be critical in helping forest ecosystems deal with climate change. Maintaining the biological webs that stabilize forests may help conserve genetic resources for future tree migrations, ensure that forest carbon stocks remain intact on the landscape, and conserve species diversity. UBC graduate student Marcus Bingham is finding that maintaining mycorrhizal webs may be more important for the regeneration and stability of the dry than wet interior Douglas-fir forests, where resources are more limited and climate change is expected to have greater impacts. Helping the landscape adapt to climate change will require more than keeping existing forests intact, however. Many scientists are concerned that species will need to migrate at a profoundly more rapid rate than they have in the past, and that humans can facilitate this migration by planting tree species adapted to warm climates in new areas. UBC graduate student Brendan Twieg is starting new research to help us understand whether the presence of appropriate mycorrhizal symbionts in foreign soils may limit the success of tree migrations, and if so, to help us design practices that increase our success at facilitating changes in these forests.

Daniel adds: Some housecleaning bits to add. Dr. Simard noted that a version of today's BPotD appeared in the Faculty of Forestry's newsletter Branch Lines, here: Simard, S.W. (2010) Why research matters to the forest systems of BC (PDF). Branch Lines, 20: 4-5. Dr. Simard also contributed the photograph of Cantharellus formosus. The illustration of the fungi and tree is courtesy of Shannon Wright. The schematic of the fungal network is by Kevin Beiler, and was published in: Beiler KJ, Durall DM, Simard SW, Maxwell SA, Kretzer AM. 2010. Architecture of the wood-wide web: Rhizopogon spp genets link multiple Douglas-fir cohorts. New Phytologist, 185: 543-553.

Today starts the annual series featuring research at the University of British Columbia as part of Celebrate Research Week. Note: the photograph of the plant was not submitted as part of the entry, but I added it for illustrative purposes: Macaranga peltata by J.M. Garg of Wikimedia Commons.

Lindsay introduces Dr. Reinhard Jetter:

Dr. Reinhard Jetter is an Associate Professor with joint appointment in both the Botany and Chemistry Departments at UBC. He also holds the Canadian Research Chair in Natural Plant Products. His research projects focus on plant biochemistry, especially on the mechanisms with which plants defend themselves against herbivores and adverse climatic conditions.

Dr. Jetter writes:

We use gas chromatography and mass spectrometry to analyze the chemical composition of plant surfaces. The chemical profiles differ greatly between species and between different organs of the same plant, in some cases even within one organ - for example between the upper and the lower sides of the same leaf. This can be seen in one of our projects where we found that the leaves of diverse Macaranga species are covered with compounds forming a smooth coating (first image via scanning electron microscope), whereas the stems of the same plants exhibit a surface that is very rough due the presence of microscopic crystals (inset image).

The crystals make those stem surfaces slippery for walking insects, and so help to protect the plant against many small herbivores. Slippery surfaces are difficult to scale only when they are inclined or even vertical, but would be useless on horizontal organs. So it makes a lot of sense that the plants make crystals only for the stems and not for the leaves. How do plants manage to be so efficient in the use of this defence mechanism? We found out that the slippery crystals consist of special compounds called triterpenoids, which are very similar to cholesterol. They are being made solely for this purpose, and we are currently investigating the genes and enzymes involved in their synthesis.

In other projects, the Jetter lab is studying the biochemistry of skins of crops (rye, tomato) and model species such as Kalanchoe daigremontiana ( commonly known as "mother of thousands") and Arabidopsis thaliana (thale cress). We want to understand how each species makes and accumulates different chemical compounds at the surface of its organs, and what their individual biological functions are.

Daniel adds: As an aside to local readers, I'll be giving a lecture on Monday: Biodiversity of Southern Alaska and Yukon. This is part of our education theme for this month on "Biodiversity and the North". The BPotD series on the topic will take place later in March.

It's early March, so it's time for my mind to drift to thoughts of visiting California for wildflowers and gardens. This photograph is from my 2008 foray, when I visited the Arboretum at the University of California Santa Cruz.

The UCSC Arboretum is famed for its extensive southern hemisphere collections. Accordingly, this vine / climber is a species from Western Australia, Kennedia nigricans, variously known as black kennedia, black coral-pea, black-bean or snakevine. As Wikipedia notes, Kennedia nigricans is a "vigorous" plant used for covering embankments or structures (and this was the case at UCSC Arboretum, where it enveloped a trellis if I recall correctly). As noted by Rodger Elliot, though, in Australian Plants Online: Australian Climbing Plants: "...it is worth considering...using climbers by letting them wander through other plants. There are many Australian climbers which are not overly vigorous which are ideal for this purpose but you need to be selective. If you try this with Kennedia nigricans, K.retrorsa or K.rubicunda you'll find that not only will other plants in the garden be swamped but your fence may also be overcome and end up lying horizontal! I've seen K.nigricans kill a forest oak (Allocasuarina torulosa) just by smothering it." Given that individuals can reach at least 4m high and have a spread of 6m, it seems a species to be judiciously used in cultivated situations.

Nearly 80% of the world's antibiotics (including antibacterials and antifungals) are derived from soil-borne bacteria, primarily from the genus Streptomyces. However, it is also known that some streptomycetes can live within plants as endophytic bacteria. Not all plant species have endophytic streptomycetes, and the minority that do typically only have one or two species. In one survey of Kennedia nigricans, though, thirty-nine species were discovered: Scanning electron microscopy of some endophytic streptomycetes in snakevine - Kennedia nigricans (Castillo et. al., 2006, doi:10.1002/sca.4950270606). Of the thirty-nine, seven were found to have antibacterial or antifungal properties.