ForBio and UiB Dead Wood Course 2019
- The International Dead Wood Course 2019 which took place from 24th to 28th June the is successfully finished! It is the fourth time the program runs its course, and this time it took place at the beautiful forest of Voronezhsky State Nature Biosphere Reserve in Russia. During the week, advanced Master’s and PhD students from Russia and Norway, as well as participants from Finland, Lithuania and Latvia were studying dead wood as a habitat. Instructors from Norwegian, Finnish, Russian and Swiss universities and biodiversity organisations have taught all aspects of ecology and diversity of organisms living in this fascinating biotope. Experts from Voronezhsky Reserve have actively participated as local guides, introducing the course team into a variety of natural habitats around, as well as history and ecological aspects of Usmansky Forest.
Below, we present the course summary.
Voronezh Biosphere Reserve, Russia
June 23-28, Voronezh Natural Reserve, Russia
Maria Shumskaya, Kean University, NJ, USA
Dmitry Schigel, University of Helsinki, Finland
The IV International Dead Wood course took place at Voronezhsky State Nature Biosphere Reserve, Russia on 24–28 June 2019. The course was organized by Norwegian partners: University Museum of Bergen, Norwegian University of Life Sciences, Norwegian Institute for Nature Research, University of Oslo, and the Research School in Biosystematics – ForBio, as well as Russian partners: Voronezhsky State Nature Biosphere Reserve and Lomonosov Moscow State University. Additional support was provided by the University of Helsinki. Funding provided by Norwegian Agency for International Cooperation and Quality Enhancement in Higher Education (Diku).
The major scope of the course was to complement one of the four major books on dead wood biodiversity with the up-to-date lecture material, field experience and practical work, and provide network experience to the growing specialists in a variety of fields of ecology and conservation.
The intensive five-day course program was comprised of lectures, workshops, field trips, and at the end students were to take an obligatory book exam. A mixed group of more than twenty Norwegian and Russian students progressing with their Master’s and PhD education participated in this rigorous, flavorful coursework.
List of species observed by the course participants during the course field trips is shared via iNaturalist project.
The course program and certain lecture slides are available from the Dead Wood Course 2019 web-site.
- Sunday, June 23rd
The team of the course students and instructors has visited the Reserve Museum of Natural History and the Beaver’s Farm. The listeners were introduced by the Reserve’s staff Igor Vorobyov, Elena Starodubtseva and Natalia Romashova into the history of the Reserve, specific biotopes and protected areas, as well as successful stories of re-introduction into nature the endangered species of beavers and red deer.
- Monday, June 24th
Theme of the Day: Dead Wood as a Habitat
The coursework began on June 24th with the Welcome Speech of the Reserve’s President Anatoly Tarasov and continued with the overview on the Reserve’s history and biology by the senior researcher of the Reserve Elena Starodubtseva. The introductory lectures on dead wood as a habitat were to follow.
Dmitry Schigel, a docent of mycology from the University of Helsinki (Finland) and a scientific officer of the Secretariat of the Global Biodiversity Information Facility, who is a specialist on dead wood fungi and insect interactions, overviewed the dead wood as a habitat where all kingdom of life meet; both fungi, trees, insects and bacteria can utilize this substrate as a source of food or a habitat. Below is the summary of his talk.
Introduction into dead wood as a habitat
Specific nature of dead wood which is in its quite temporary existence and a limited amount of physical space, as well as scarce protein and an excess of hard-to-digest carbohydrates, requires certain adaptations to be developed in organisms that use it as habitat. Such biological species, called saproxylic, are quite diverse and numerous, but often cryptic; with the recent advancement in both morphological and molecular methods, cataloguing such species requires functional databases such as GBIF or UNITE. The nature of dead wood requires the saproxylic organisms to quickly disperse from one patch to another, both actively and passively (e.g. fungi via spores). These features are important to consider in forest management and conservation efforts. Current research in dead wood diversity is to answer the questions such as: are the saproxylic species all specialists? generalists? how do they disperse? how do they promote digesting of hardly edible carbohydrates?
Several important environmental and biotic determinants of wood decay that affect the biodiversity of dead wood at different times were discussed. A definition of a dead tree deserves special discussion. Once tree sap stops running and the roots become physiologically inactive and leaves stop photosynthesis, the tree can be officially recognized as dead (in contrast with a physiologically alive tree which naturally has a massive amount of dead cells, such as xylem cells). There is a range of intermediate states where living tree harbours specific dead wood microhabitats, such as dead branches and twigs, and hollows.
Biotic determinants of wood decay:
Once a tree is downed, it is still full of sugar in its phloem; the pioneer fungi (e.g. yeast) that utilize sugars arrive to the tree, consume all sugar and never come back. Once sugar is consumed, colonization of the tree continues with the fungi that can digest the hard carbohydrates of plant cell walls: cellulose, hemicellulose, lignin. First fungal guilds are to digest the most tough woody materials, and the next ones are rather more competitive to push out the previous guilds and proceed with the softer substrate. Brown rot fungi specialize in digesting cellulose, leaving brown lignin to be exposed, white rot fungi are excellent in digesting lignin leaving white cellulose behind, and soft rot fungi are less aggressive in digesting the cellulose; however, this ranking is simplified and does not reflect the complexity of enzymatic processes happening in the wood.
Some tunneling bacteria can degrade cellulose and lignin in wood, those are mostly aquatic species. Erosion bacteria can digest cellulose and lignin in marine environments and are anaerobic, resistant to the lack of oxygen.
Animal digestion of wood, or xylophagy, does not really exist in its pure form, but there are ways for the animals to participate in wood decay: 1) their gut symbionts digest wood, 2) they can ingest active enzymes from wood (wood wasps, Cerambycidae), 3) insects can secrete a complete enzyme system (hardly exists).
Decay phases can be roughly classified using 5 subdivisions from the first being the least decayed, and the fifth being the last stage of decay, with stages 3 and 4 being the longest of all phases. In the field, the decay stage is commonly tested by pushing a knife in a dead tree. Since different decaying zones exist in the same tree, the method is not ideal, but gives a quick estimate of an overall decay stage. Different fungal groups thrive at different decay stages; for example, most polypore fruit bodies appear at stage 3, while agarics typically surface at the decay stages 4-5. Late decay arrivers are not aggressive decayers and have a chance to reproduce after everything is decayed. The activation of the fruiting body formation in fungi is dictated by several factors, related to the limitations of the substrate: cold stress, light depletion, or nutrient depletion.
Environmental determinants of wood decay:
Wood decomposition rate depends on temperature, sun exposure (above ground), drainage (below ground), or water logging (peatland, rivers, lakes). Wood can provide lots of microhabitats depending on water content in a specific part, contact with soil, contact with air, rate of water evaporation and aeration. In addition, chemistry of various wood is different; the major differences lie between angiosperms and gymnosperms, thus dictating different rates of decay for each specific tree species. (Weedon 2009).
Evolution of saproxylic species and their diversity
In terms of evolution, saproxylic species appeared once lignification of the trees has developed. First, Ascomycota fungi progressed to assist with lignified plant stems; then yeast gut symbionts appeared, and Basidiomycetes followed up with their development. It is of a challenge to follow the evolution of fungi since fungi are not easily fossilized. Some, however, can be detected in droppings of insects.
Saproxylic beetles appear ca 275 mya, followed by parasitoids attracted by high concentration of insects on wood. Some hunting myxomycetes (e.g. Physarium) became saproxylic as well. At least 1 mln species on the planet is estimated to be saproxylic.
In the afternoon, the course team travelled around the Reserve using Cherepakhinsky Trails. The Reserve’s staff Igor Vorobyov and Elena Starodubtseva showed different biotopes to the group; the course mycologists and entomologists demonstrated various wood decay stages, and specialized fungi and insects during this trip around the nature built lab.
- June 25th
Theme of the Day: Dead Wood Fungi
Håvard Kauserud, a professor from the University of Oslo and a specialist in fungal ecology and evolution, started the morning coursework with the lecture on saproxylic fungi. He introduced fungi as members of the Opisthokonta supergroup which evolved 1.5 billion ya, with Ascomycetes and Basidiomycetes being the major decomposers. The major role of decomposing fungi is to release carbon trapped as carbohydrates in plants. Fungi can be identified several ways: by using a culture, morphologically by their fruiting bodies, or via the analysis of DNA. For the DNA analysis, Sanger sequencing or, most recently developed Next Generation Sequencing, can be utilized.
The life cycles of saproxylic fungi are adapted to the specifics of the dead wood habitat. Wood is a temporary sanctuary, so the spores of the fungi must be dispersed by wind or by insect vectors. The lack of efficient dispersal may limit the occurrence of specialist saproxylic fungi. The efficiency of spores dispersal depends on their size, time of release, light or freezing. Fungal bodies per se can be really old; e.g. Armillaria can form a 2500 yo fungal individual.
The lecture on saproxylic fungal population biology, dispersal, and evolution was continued by Inger Skrede, a researcher from University of Oslo and a specialist in speciation, population genomics, comparative fungal genomics, phylogeny and wood decay. She spoke on several methods that can be used to detect fungal population if we do not see their actual reproduction: 1) molecular markers from the genome, 2) vegetative compatibility/incompatibility, 3) mating experiments for cultivable fungi. Then she made the audience to think on how and where the reproductive barriers arise and what controls fungal mating. Interesting subjects to discuss were the differences between two populations compared to two species. It is an important question since different species or populations may have different ecology, ability to adapt to climate, or conservation needs. She then proceeded with examples:
Trichaptum abietinum: using molecular markers, multiple individuals of this species can be discovered on the same log forming a population. This species grows both in West Europe and North East America. These populations might be different; this can be checked by cultures and mating in the lab. Interestingly, the American population cannot mate with the European.
Fomitopsis pinicola: three groups in North America, cryptic species that do not form one clade.
Phellopilus nigrolimitatus: rare species, white rot, grows in old forest. Fruiting late. Can grow as many individuals on the same log. Shallow population structure. Division between Norway and Finland. Is genetic diversity in Finland affected by human activity?
Serpula lacrymans: this species grows mostly in houses, efficiently forming dry brown rot. There are populations in Japan, North American East, West Europe. The populations are very similar, probably distributed by humans.
Full genome sequencing is used to compare the populations. Japanese strains are different from the Europeans. Originally the fungus is from Himalayas!
Fungal decay ability is dictated by the chemistry of wood and depends on enzymes possessed by fungi, water amounts, temperature, pH, minerals, competition, and succession, thus directing the evolution of saproxylic fungi (see Evolution of wood decay, Floudas 2012; Riley 2014). White rot fungi are more common on angiosperms, while brown rot are mostly on gymnosperms (later evolved to generalists) (see Krah 2018). Improved understanding of fungal wood decay would allow us to: improve our understanding of C and N cycle, support biotech development, protect ecosystems, protect “in service” wood (houses).
Bonus: treated wood is usually treated with toxins that are not good for the environment. Furfurylated wood might be more environmentally friendly (it is an alcohol) (see Skrede 2019).
The lecture was ended with an active learning exercise: the students and instructors were offered to build a moving human sculpture to show two definitions they learned during the class. Four groups of the ad hoc performers enjoyed the experience under the Voronezh sun showing off their improvisation skills.
In the afternoon, a professor of mycology from the Lomonosov State University, Russia, Alexander Kurakov continued with a lecture on carbon and nitrogen cycling, and the role of dead wood and fungi in it. He first overviewed the pathways carbon circulating in forests and around the biosphere; carbon is emitted by the forests as CO2 via respiration of plants and humus/debris, adding to global warming, but is also conserved in the form of carbohydrates in debris, biomass and humus. Some of the CO2 is consumed by the ocean. In the forests, the carbon pool is larger than in other biomes; C turnover is higher in temperate and deciduous forests, and lower in taiga. Depositing of carbon in the tree matter and specifically in dead wood decreases the emission of carbon dioxide to the atmosphere. In a mature forest respiration and photosynthesis rates are equal, and dead wood stores most of the carbon in its organic form as lignin and cellulose. The average retention of carbon in wood is 500—600 years, if the maximum life of dead wood is 3000 years (hemlock in the rock mountains), in a boreal forest – 100-500 years, small branches – 2-20 years. Spruce forest can decompose cellulose matter the fastest and the most efficient way. A discussion on the role of forests in solving of global warming problem continued.
Forests also participate in cycling of nitrogen: microbes in humus and soil consume amino acids, nitrificate the amino groups into nitrates which are converted to N2O or N2 and escape the biosystem. Mineralized nitrogen also leaches as NO or N2O to the groundwater from soils. Fungi can participate in different N-related processes. Some dark fungi, for example, have melanin which contains nitrogen. Or, in spruce logs N fixation is increased in the last stages of decay because fungal decay of lignocellulose provides blocks of new stable N-containing substances to contribute for humus or protein-lignin formation.
Next, Elena Bilanenko, a professor of mycology from the Lomonosov State University, Russia, presented on composition of microscopic fungi and bacteria which participate in wood decomposition. She discussed Ascomycetes: yeast and staining molds, that grow on construction wooden structures surface, causing mostly cosmetic damage; with species like Trichoderma even protecting wood from other, aggressive wood decayers. Some staining fungi, however, in natural environments can act as tree pathogens. A quick overview on bacterial wood decay was also given.
The lecture session was followed by the practical session led by Ludmila Kalinina, a graduate student from the Komarov Botanical Institute (Russian Academy of Sciences), who explained about various morphological microscopic structures used in agaric fungi identification and the students proceeded with microscopic slides preparation and fungi identification.
Later in the evening, program assistants presented their work in the field of dead wood to the audience. Nina Fillipova, a senior researcher mycologist from the Yugra State Univrersity, Russia, presented on her work on analysis of fungal community in bog forest ecosystems of Western Siberia and her work as a curator of Yugra Region Fungarium. Ilya Viner, a graduate student from the University of Helsinki, has presented his current progress on lineage sorting in a common wood-decaying species Basidioradulum radula. Maria Shumskaya, Assistant Professor from Kean University, USA, has spoken on teaching of dead wood in US and presented a teaching module on analysis of dead wood fungi communities using software R. The module is an open education resource using a dataset collected by undergraduate students of Kean University. The course participants had a chance to work through the module and provided valuable feedback during this session.
- June 26th
Theme of the Day: Dead Wood Invertebrates
Tone Birkemoe, a professor of entomology from the Norwegian University of Life Sciences, has started the day with the introductory lecture into a diversity of insects living in dead wood. She overviewed various functions the insects can perform, such as 1) feeding on wood, bark, fungi, sap, each other (predators, parasitoids, parasites); 2) nesting in empty burrows from wood-boring beetles, in their own nests (ants, termites) in hollows (wasps, bees); 3) hiding for winter or during the day if they are nocturnal.
Insect groups that inhabit dead wood include beetles (Coleoptera), flies (Diptera), butterflies and moths (Lepidoptera), wasps, bees and ants (Hymenoptera), bugs (Hemiptera), termites, as well as soil fauna. Among beetles longhorn beetles, stag, bark, jewel, click beetles, weevils, anobiids, scarabids, and rove beetles can be found. 65% of the beetle families have saproxylic species. Out of flies (Dipterea), 48% of families have saproxylic species. Among butterflies and moths – fungus moth, cossidae (goat moth), clearwing moth (sessidae) live off dead wood.
Only few insects can kill a tree, and even if they attack a living tree it is rarely healthy trees; the trees are usually stressed from damage by heat and draught. Species that can live on living trees are bark beetles, emerald ash borer, Asian longhorn beetle, and goat moth.
Insect groups succeed each other while wood decay is progressing.
Phase 1 (year 1-2): dead wood is inhabited by species feeding on fresh inner bark or inoculated fungi, such as bark beetle, longhorn beetle, ambrosia beetle, wasps etc.
Phase 2 (year 2-10): insect species feed on remaining bark, growing fungi, initial decayed wood. Flat beetle species appear that do not make galleries. Many flies, such as wood-soldier flies, awl flies.
Phase 3 (year 2-50). Dead wood has no bark at this stage, so insects are feeding on fungi or wood or mixed. Longhorn beetles, stag beetles, Peltis grossa, jewel beetles, hoverflies and crane flies occupy dead wood.
Phase 4 (year 50-150). Dead wood is very soft and rotten, and is covered with moss. Insect species use dead wood for hiding and nesting (ants, ground beetles), soil fauna is present, stag beetles, click beetles, old house borers.
Such a diversity of saproxylic insects is explained by a large variation depending on microclimate and large biomass of dead wood. Also, many insect species depend on other species.
Rannveig Jacobsen, an entomologist from the Norwegian Institute of Life Sciences, continued with the lecture on insect-fungus interactions in dead wood, and presented her work on the influence of insects on the rate of wood decay.
After a short break, Anne Sverdrup-Thygeson, a professor of conservation biology at the Norwegian University of Life Sciences as well as a scientific advisor at the Norwegian Institute for Nature Research, lectured on the importance of late successional dead wood habitats, such as ancient trees and wood mould. She explained that old trees are very species rich, since they provide lots of different habitats and thus can be considered the arboreal megalopolis (Speight, 1989). Cavities in old trees are formed by Laetiporus sulphureus, Fistulina hepatica, and are enlarged by insects (Eledona agricola on Laetiporus, Triphylus bicolor on Fistulina hepatica). Wood mould, formed as a result of decay, is an incredibly nutritious substrate and is much easier to digest for multiple other insects.
Some insects, such as the hermit beetle (Osmoderma eremita), start life in hollow oaks. They are sensitive to landscape changes, depend on large/old trees. Some beetles are veteran tree specialists. They respond to changes in environment immediately, in a small scale (500 m), preferring decomposed deadwood.
In conclusion, removal of old trees is a threat to these specialist insects.
The lecture session was then continued by Steffen Roth, a professor from the University of Bergen, Norway, on Hemiptera (true bugs) that participate in wood decay, and by Alexander Ryss, a professor of the Zoological Institution, Russia, that overviewed Nematodes (round worms), their structure, classification and species inhabiting living and dead wood.
After lunch, the course team continued with the field trip around the Reserve looking for the saproxylic insects. Professors Birkemoe and Sverdrup-Thygeson led the trip. After a two hours session, students had a practical hour observing insects under binoculars and identifying the species. Later in the evening, professor Ryss demonstrated isolation of Nematodes from dead wood, and students explored isolated worms under the magnification, as well as various Nematode species on prepared slides.
During the same day, students have visited the Museum of Fire at the Reserve, where Elena Starodubtseva explained about the fire safety in the forest and ecological succession that happens after the fire.
- June 27th
The course team led by Igor Vorobyov has completed several field trips; one to the Museum of Pre-historic Men in Kostenki, and two into the natural sites with a lot of human disturbance: a forest growing on sides of a dry creek, and a young 9 years old pine forest forming on a site after a massive fire.
- June 28th
Theme of the Day: Dead Wood Conservation
Anne Sverdrup-Thygeson has started the day with the lecture on dead wood and conservation in Fennoscandia. She explained that forests suffer from a long-lasting human impact. Currently, only 1/3 of the forest is unmanaged, but the rest is managed. The forest can be disturbed at different scales: from heart-rot+wind competition (small scale), to beavers-insect outbreaks and large-scale fires. Forestry has changed Fennoscandian forest resulting in less old forest, less dead wood, reduced forest fire, and landscape changes. While modern conservation efforts led to an increase of dead wood, its overall amount is still severely small to continue to undisturbed sites. Main problems in today’s forest were identified as:
1. Low proportion of old forest
2. Amount and quality (diameter, decay stage, cause of death) of dead wood.
3. Landscape importance. Dead wood in surroundings can be more important than dead wood in forest stand; if the surroundings are severely disturbed, saproxylic beetles would not be able to get to the dead wood substrate.
Sylvie Barbalat from WWF Switzerland, continued with the lecture on dead wood conservation in Western and Central Europe. She overviewed the present situation with logging in Switzerland, and gave several examples on successful dead wood conservation efforts in National Parks which led to biodiversity increase.
Dmitry Schigel concluded the coursework with the lecture on dead wood and human interactions. Some interesting examples on human perception of hollow trees or woody debris were provided, and some insights into the legislation to consider dead wood, the topic which will likely to grow in importance at the future Dead Wood Courses.
The course was finished with a 1.5 hours long exam, where students were challenged to visually summarize everything they learned from the book of their choice and the course material, and also approach the decision makers with scientific argumentation of the importance and biodiversity value of dead wood habitats and of saproxylic species.
A dataset of species observed by the students and instructors of the International Dead Wood Course 2019 at Voronezhskiy State Reserve is published at the Global Biodiversity Information Facility web-site.
The dataset is published to demonstrate methods used in biological inventory and open biodiversity data publishing to the course participants, as well as the specialists working at the Reserve. In addition, the dataset contains information about fungal species that were not assessed by the Reserve before.
Photos: Dmitry Schigel, Igor Vorobyov, Kristina Polyanina, Anna Sapelnikova