Tag Archives: Forest Trees

Changing Forest Dynamics in Harsh Environments IUFRO Meeting 2014

I’ve been to a few IUFRO meetings for tree genomics and the molecular biology of tree-microbe interactions and have found the IUFRO meetings to be very worthwhile and well organized.  An upcoming meeting — Changing Forest Dynamics in Harsh Environments — will address climate change of forests with regard to many factors.  This meeting will be held in Québec, Canada, during August 18th to 22nd, 2014.

changing forest meeting image

Some of the themes of the symposium will be focused on “changes in disturbance regimes, post‐disturbance recovery dynamics, trends in tree growth, landscape‐level changes in structure and composition, and forest management under a changing climate”.

For more information visit the meeting website or the meeting announcement flyer.

Drought-Induced Decline in Mediterranean Truffle Harvest

Some of my favorite foods are truffles, and perhaps the best tasting truffle – in my humble opinion – is the famous Périgord Black Truffle, also known as Tuber melanosporum, which is known as a prized delicacy capable of fetching a pretty penny.

me holding truffle

Tuber melanosporum is an important ectomycorrhizal fungus that can be cultivated with crop trees such as Hazelnut, and other truffles can be cultivated with other nut trees such as Pecan.  Despite a concerted effort to understand the biology of T. melanosporum, both through a genome sequence and other molecular tools to understand population biology – as well as government efforts to promote cultivation with nut trees – harvests of the Périgord Black Truffle have been declining since the 1970s.  There has been no agreement in what has been causing this decline from a community of researchers.

truffle climate change paper header

In a brief report entitled “Drought-Induced Decline in Mediterranean Truffle Harvest” in the journal Nature Climate Change, Büntgen et al. recently described how climate change may be affecting truffle production, either directly, or by affecting the biology of the truffle’s host trees.  Such measurements are challenging in numerous regards; inspecting climate data is difficult enough, but reports of truffle harvesting are scarce for many reasons, one of which is the fact that many successful truffle collectors are reluctant to give information about their productive grounds.

truffle climate paper figure

The authors correlated climate details from 12 climate models with truffle harvests from various parts of Europe (namely Aragón in Spain, Périgord in southern France, and Piedmont and Umbria in Northern Italy).  They observed that tree ring growth in Oak trees and truffle production were correlated and showed that increased measurements of summer evapotranspiration could explain both the reduction in plant growth and truffle production.

The authors hypothesize that tree and fungus competition for summer soil moisture may be reducing the production on truffle sporocarps.  Unless the present course of climate change is reversed, it is expected that truffle harvests in Europe will continue to decline.  This is bad news not just for the truffles and trees, but the people who enjoy both.

UPDATE: The New York Times have posted an article (December 20th) entitled “$1,200 a Pound, Truffles Suffer in the Heat

Genetics Of Fagaceae & Nothofagaceae Meeting, October 2012

The IUFRO (International Union of Forest Research Organizations) working group has organized the “Genetics of Fagaceae & Nothofagaceae” meeting to be held in Bordeaux, France from October 9th to 12th, 2012.

This meeting will build upon a successful “Genomics of Forest and Ecosystem Health in the Fagaceae (Beech Family)” meeting held in North Carolina Research Triangle Park in 2009.

The aim of this international conference is to present new scientific findings in the area of genetics and genomics of species within the Fagaceae and Nothofagaceae.

Registration is open.

Eastern Hemlock, the Hemlock Woolly Adelgid, and Mycorrhizal Fungi: Citizen Science?

Many of you know that I am located in Pennsylvania, but you may not be aware that the state tree of Pennsylvania is the Eastern Hemlock (Tsuga canadensis). Hemlock is not high on the list of valuable trees – the wood is moderately important in the pulp/paper and woodworking industries and it was once highly valued for tannins optimal for leather treatment.  As a symbol for the state of Pennsylvania and for its ecosystem services – which include being a carbon sink, habitat for wildlife, and foundation for ecosystem water retention and purification – the tree is extremely important.

forest service photo

Eastern Hemlock is facing a serious threat to its existence: the Hemlock Woolly Adelgid (Adelges tsugae).  The Hemlock Woolly Adelgid is a Hemipteran insect (think tube feeders, like Aphids, which are somewhat closely related) so the pest typically feeds by sucking on plant juices from the phloem, which drains water and photosynthate from the plant.  Like other tube feeding insects, the Adelgids are sloppy eaters and spill plant juices all over the place, so the plant looses more nutrients and water than just what the insect feeds on.The woolly part of the Adelgid protects its body and eggs and maintains a microclimate to survive harsh temperatures and weather.  This protective hairy covering is also somewhat impermeable to pesticides and biocontrol agents.

photo 1

When I was on the West Coast of the US working with the Forest Service, we frequently came across a native Woolly Adelgid, which occupies the Pacific rim.  Adelgids were only first identified on Eastern Hemlocks in 1951 near Richmond, Virginia, probably introduced from nursery stock –like many other invasive species.  Using phylogenetic techniques researchers have identified that the Hemlock Woolly Adelgid populations introduced in the Eastern US trace to those from Southern Japan, not from the Pacific Northwest of the US.

EH range

The mortality of Eastern Hemlock has become so severe that Congress has become interested.  Just this past week (see also here and here), Glenn Thompson, a Republican from Pennsylvania’s 5th District, Dean of Penn State’s College Of Agricultural Sciences Bruce McPheron, Kurt Gottschalk from the US Forest Service, and Penn State Entomology professor Kelli Hoover held an open public forum to discuss the Hemlock Woolly Adelgid on Pennsylvanian Eastern Hemlocks.  Many are worried that the Hemlock Woolly Adelgid (along with other aggressive invasive pests such as the Gypsy Moth, Sirex Wood-Wasp, Asian Long-horned Beetle, and the Emerald Ash Borer) will enter the category of pests that have progressed to complete destruction of a host with little to no choice except to cut down dead trees (i.e. Chestnut Blight and Dutch Elm Disease).  Obvious discussions have centered on the fact that the cost of treatment or management greatly exceeds what some deem the cost of the commodity.

american forests photo

Perhaps you can see – knowing a little about my research interests – where I am going with this: with massive tree mortality I am interested in what is happening to the obligate mycorrhizal symbionts of the Eastern Hemlock.  There’s not much data on fungal specificity for the Eastern Hemlock – most of what I know is either anecdotally passed on to me or based on my own observations.  Collectively, we really don’t have much understanding on the magnitude of fungal diversity in general, but we’re completely at a loss regarding the below-ground fungal diversity associated with Eastern Hemlock.  Lactarius purpureus, one of my favorite mushrooms from a genus near and dear to my heart, is obligately associated with Eastern Hemlock; it forms mycorrhizae with no other plants.  There is a handsome purple-capped white-stemmed Russula, something close to R. xerampelina, but not exactly like it, that is also found only associated with Eastern Hemlock.  Is anyone certain of any others?

One report in a recent meeting proceedings described five genera, which included Lactarius (16 species), Amanita (13 species), Russula (six species), Tricholoma (four species), and Cortinarius (four species), that were all collected in large mono-dominant Eastern Hemlock forests.  Whether or not these fungi are obligate symbionts of Eastern Hemlock have yet to be determined, but that list is a start, nonetheless.

I have been collecting under Hemlock in one form or another for about 15 years –not a long period of time I admit – but I have been hard pressed to find some of these fungi in the same locations in recent years.  These mushrooms seemed common in past years in some specific locations, but I haven’t collected Lactarius subpurpureus for many years now.  I have observed Hemlock Woolly Adelgid in all of these locations.  Trees that have insect infestations do not have extra photosynthate to provide to the fungal symbionts.  A lack of carbon for the fungus should translate into a lack of, or at least lessened, reproductive fruiting.  An opposing argument is that trees that are losing photosynthate are more reliant on symbionts for nutrient uptake to compensate for nutrient loss, so there would be a greater reliance on, and therefore more frequently observed, mycorrhizal roots.


There’s a lot of stochasticity involved with finding mushroom fruiting bodies.  I am just one observer, observing one location at a time – and let’s not forget huge variations in local weather and timing of rainfall during the short window when most fungal sporocarps fruit.  It’s not uncommon for some fungi to go decades uncollected at the same location.  As a result, I spent some time, about 5 years ago, trying to access public foray records over the past 50 or so years to see if there has been a noticeable decrease in the collection of Hemlock associated macrofungi.  The problem is that there really isn’t much in the way of public foray records to access on the Internet and I gave up on the idea of documenting recent fruiting records under Eastern Hemlock.  Some researchers, such as Pat Leacock, David Lewis, & Greg Mueller at Chicago’s Field Museum, have done a great job working with national amateur mushroom societies, such as NAMA’s Voucher Collection Project, and many small local groups to make foray data available.  There’s just not enough data available to address the types of questions I am interested in here concerning the fungi associated with Eastern Hemlock.

This recent public interest in the demise of Eastern Hemlock has again kick-started my thinking about fungi associated obligately with Hemlock.  Amateur mycological and botanical societies could play a huge role in documenting species presence at forays and weekend gathering, as well as playing a leading role in establishing multi-year surveys of hemlock fungal symbionts.

Would anyone like to provide any input here?

Are there resources that I am unaware of that are provided by amateur scientists?

Would anyone like to start a citizen science brigade with me to survey in and around Eastern Hemlock for fungi (particularly Lactarius subpurpureus)?


UPDATE: I have received a few questions about the photos posted here.  If you click on a photo, the link will take you to the source of the photo.

The two photos of the Hemlock Wooly Adelgid infestations on Eastern Hemlock (the photo where I am showing you the underside of the hemlock branch and the photo just about this comment showing the top portion of the branch) were taken from a tree right outside my office on the campus of Penn State.  Some of these trees have been sprayed with a pesticide (not sure which one) in previous years, but the Hemlock Woolly Adelgid infestations have continued.  The future of these campus trees is uncertain.

Check out the re-blog on the great site: The Hyphal Tip!