What is a Mother Tree?

Mother Trees are large trees within a forest that act as centralized hubs supporting communication and nutrient exchange amongst trees. Using a vast underground fungal network, called the mycorrhizal network, Mother Trees supply seedlings with the resources they need to grow.

Watch Dr. Simard’s TEDTalk to find out more about how trees communicate using the mycorrhizal network.

Why are Mother Trees important?

Research has shown that the connections between Mother Trees and neighbouring trees act as a protective and regenerative element of the forest. Keeping these relationships intact by maintaining the network of connections helps ensure that forests will be more resilient to changes and be productive, healthy and diverse and around for many generations to come.

What is the Mother Tree Research Project?

The Mother Tree Project is a long-term experiment testing forest cutting and planting methods in order to learn how to create resilient forests for the future. The guiding principle is to retain Mother Trees and their connections to protect biodiversity, carbon storage and forest regeneration as climate changes.

Why are you doing this research?

The goal of the project is to provide scientific data to help direct management of forests under a changing climate. Specifically, we are doing experiments to try and determine retention levels and seedling mixes across various climates that will result in successful forest regeneration.

Learn more about our research.

Who is involved in the project?

Led by Dr. Suzanne Simard of the University of British Columbia (UBC), the Mother Tree Project brings together academia, government, forestry companies, research forests, community forests and First Nations to test forest renewal practices.

Learn more about Dr. Simard and the Mother Tree Project Team.

Who is funding your research?

The primary source of funding to establish the project was a Natural Sciences and Engineering Research Council (NSERC) Strategic Project Grant which was received in October 2015.

Additional funding was provided by Forest Enhancement Society of British Columbia (FESBC) in 2017 to expand the scope of the project to include forest carbon storage, fire risk and wildlife impacts as well as to include First Nations stakeholders.

We received funding in 2019 from the Forest Carbon Initiative (FCI) to do in-depth carbon measurements as well as to monitor the planted and natural regeneration.

How is your project connected to forestry and logging?

The Mother Tree project is building on the research on tree communication and connections to design forest practices that help reduce stress in forests and maintain the natural connections between trees that support forest health.

The experiment is looking at various forestry practices – from variable levels of tree retention during harvesting to a range of seedling mixes during replanting – which can be implemented by foresters to create healthier, more productive, and more resilient forests.

How is your project connected to climate change?

Climate change is causing significant stress on our forests. As climate change continues, forestry practices will need to be adapted in order to accommodate the increasing stress this change is having on the health and productivity of our forests.

Forests are repositories of biodiversity (for example, wildlife, trees, plants, fungi, microbes) and they store carbon (for example, in trees, plants, soils, and logs) helping offset rising atmospheric CO2 levels. Diverse forests have been shown to store more carbon than monocultures. Biodiversity and carbon storage are thus indicators of forest health. The Mother Tree Project is studying how these properties are affected by climate change and forest harvesting.

By experimenting with a range of forestry practices in different climates, the Mother Tree Project aims to identify successful practices within each climatic region. These practices can then be applied in regions where the climate is expected to become similar to the experimental sites.

Do Common Mycorrhizal Networks (CMN’s) Exist?

Yes.

Common Mycorrhizal Networks (CMN’s) have been shown occur in forests where they have been intensively studied. In addition to many published articles about CMN’s, the following studies have mapped below ground connections using advanced molecular tools: Beiler et al. (2010, 2012, 2015) and Van Dorp et al. (2020) in interior Douglas-fir forests of British Columbia, and Lian et al. (2006) in pine forests of Japan.

All of these studies found that CMN’s connect the trees together.

Other lines of evidence using DNA sequencing and microscopy suggest CMN’s exist in forests elsewhere in the world. This has been documented in several reviews, the most exhaustively by Horton et al. (2016).

Most countries that contain the highest richness of tree species do not have the wealth of resources such as in Canada to conduct intensive studies such as those by Beiler, Van Dorp or Lian. Moreover, top scientific journals do not generally publish science that is an extension of previous discoveries, thereby de-incentivizing repetition of this type of research.

Is There Evidence Resources Transfer Through CMN’s?

Yes.

The Simard Lab studies have shown repeatedly that resources transfer among trees through myriad pathways, including the CMN, mycorrhizal roots and the soil. Resources found to transmit through these belowground pathways include carbon, nitrogen and water (e.g., Simard et al. 1997a, 1997b, 1997c; Schoonmaker et al. 2007; Philip et al. 2010; Teste et al. 2009 and 2010; Bingham and Simard 2011; Deslippe and Simard 2011 (shrubs); Song et al. 2016; Deslippe et al. 2016 (shrubs)). 

Resource transfer through CMNs is a variable process because forests are naturally dynamic and diverse. The Simard Lab studies have shown that the amount of resource transfer through CMN’s varies depending on such things as the size, origin, water relations, phenology and shade status of the trees, as well as the disturbance history and aridity of the forest. 

A thorough review of resource transfer through CMNs is available in Simard et al. (2016).

DO CMN’s INCREASE SEEDLING PERFORMANCE?

Yes.

Seedlings’ establishing in Douglas-fir forests are primarily colonized by the CMN that already exists among the trees (and less frequently by spores in the soil). If the seedlings do not become colonized, they do not survive (Barker et al. 2013, 2014). To become colonized, new seedlings must link into the mycelium of the existing tree or plant hosts.

Three Simard Lab studies intensively examined CMN effects on seedling performance (survival and growth) in Douglas-fir forests. These studies found that performance of seedlings (especially survival) increased where they had full access to the CMN. This was particularly pronounced when the seedlings had established from seed (rather than planted as plugs), were within 2.5 to 5 meters of mature trees, or were growing in drier soils or more arid climates (Teste and Simard 2008, Teste et al. 2009, Bingham and Simard 2011 and 2012). 

The multi-aged structure of the Douglas-fir forests examined by Beiler et al. (2010, 2012, and 2015) showed that young trees had established within the CMNs of the overstory trees.  Birch et al. (2020) resampled Beiler’s study forest eight years later, and found that growth of the mature trees increased with the number of CMN connections to other trees.  

In other words, these studies provide evidence that young and old trees in Douglas-fir forests benefit from the CMN.

Birch et al. (2020) further found that along with growth, the variability in growth of the old trees declined with numbers of connections. This provides additional evidence that CMNs can mediate resource distribution among trees.

DO TREES RECOGNIZE KIN?

Yes.

In forests, seed dispersal is physically limited, so seeds tend to germinate near parent trees, with seedlings often growing near kin. The recognition of relatives, or kin-recognition, has been well studied in plants and is understood to involve signaling via roots and mycorrhizas (e.g., Dudley et al. 2013, Anten and Chen 2021) as well as volatile organic compounds (Karban 2015, Hussain et al. 2019). 

The Simard Lab has found evidence that kin recognition occurs in Douglas-fir forests, is mediated by roots and mycorrhizas, and is also affected by insect damage.  

These results were published in two journal papers, one review paper (Pickles et al. 2017, Asay et al. 2020, Gorzelak et al. 2015), and three graduate theses (Asay 2012 and 2019, Gorzelak 2017). As we mourn the tragic passing of our friend and colleague, Dr. Amanda Asay, we will continue to publish from this body of work.

As interest and attention to this novel area of research increases, evidence for kin recognition in forests elsewhere in the world continues to grow (e.g., Takigahira and Yamawo 2019, Hussain et al. 2019).

SHOULD FOREST PRACTICES CHANGE?

Yes.

Extensive clearcutting of forests around the world has caused massive declines in biodiversity, amplified climate change and contributed to the collapse of keystone species. In the Pacific Northwest, species as diverse as salmon, orca and mountain caribou, are directly affected by poor forestry practices and policy. Indigenous people have suffered the greatest losses, with displacement from their territories, resources and cultures, and diminished forest resiliency. 

Research on CMNs, as well as other studies on forest regeneration, biodiversity and resource cycling, all show that mature trees are crucial to the integrity and resilience of the forests. Leaving mature trees standing when harvesting is essential for protecting carbon pools, biodiversity and the myriad ecosystem services. 

Industrial forest management has failed to acknowledge or protect this diversity – as identified in the recent provincial Old Growth Strategic Review, and there is a collective move in British Columbia today to radically shift the balance and move to ecosystem health management. 

WHERE DID THE TERM ‘WOOD-WIDE WEB’ COME FROM?

The phrase was coined by the editors of Nature when they published the cover article, Net transfer of carbon between ectomycorrhizal tree species in the field, in August 1997.

References

Anten, N.P.R., Chen, B.J.W. (2021). Detect thy family: Mechanisms, ecology and agricultural aspects of kin recognition in plants. Plant, Cell and Environment 44: 1059– 1071. 

Asay, A.K. (2013). Mycorrhizal facilitation of kin recognition in interior Douglas-fir (Pseudotsuga menziesii var. glauca). UBC MSc Thesis. Mycorrhizal facilitation of kin recognition in interior Douglas-fir (Pseudotsuga menziesii var. glauca) – UBC Library Open Collections 

Asay, A.K. (2019). Influence of kin, density, soil inoculum potential and interspecific competition on interior Douglas-fir (Pseudotsuga menziesii var. glauca) performance and adaptive traits. UBC PhD Dissertation. Influence of kin, density, soil inoculum potential and interspecific competition on interior Douglas-fir (Pseudotsuga menziesii var. glauca) performance and adaptive traits – UBC Library Open Collections

Asay, A.K., Simard, S.W., Dudley, S.A. (2020). Altering neighborhood relatedness and species composition affects interior Douglas-fir size and morphological traits with context-dependent responses. Frontiers in Ecology and Evolution 8: 314. 

Barker, J.S., Simard, S.W., Jones, M.D., Durall, D.M. (2013). Ectomycorrhizal fungal community assembly on regenerating Douglas-fir after wildfire and clearcut harvesting. Oecologia 172: 1179- 1189.

Barker, J.S., Simard, S.W., Jones, M.D. (2014). Clearcutting and wildfire have comparable effects on growth of directly seeded interior Douglas-fir. Forest Ecology and Management 331: 188-195.

Beiler, K.J., Durall, D.M., Simard, S.W., Maxwell, S.A., Kretzer, A.M. (2010) Mapping the wood- wide web: mycorrhizal networks link multiple Douglas-fir cohorts. New Phytologist 185: 543-553.

Beiler, K.J., Simard, S.W., Lemay, V., and Durall, D.M. (2012). Vertical partitioning between sister species of Rhizopogon fungi on mesic and xeric sites in an interior Douglas-fir forest. Molecular Ecology 21: 6163-6174

Beiler, K.J., Simard, S.W., Durall, D.M. (2015). Topology of Rhizopogon spp. mycorrhizal meta-networks in xeric and mesic old-growth interior Douglas-fir forests. Journal of Ecology 103(3): 616- 628.

Bingham, M.A., Simard, S.W. (2011). Do mycorrhizal network benefits to survival and growth of interior Douglas-fir seedlings increase with soil moisture stress? Ecology and Evolution 3(1): 306-316.

Bingham, M.A., and Simard, S.W. (2012). Ectomycorrhizal networks of old Pseudotsuga menziesii var. glauca trees facilitate establishment of conspecific seedlings under drought. Ecosystems 15: 188-199.

Birch, J.D., Simard, S.W., Beiler, K., Karst, J. (2021). Ectomycorrhizal network connectivity is associated with greater growth of adult interior Douglas-fir. Journal of Ecology 109: 806-818.

Deslippe, J.R., Simard, S.W. (2011). Below-ground carbon transfer among Betula nana may increase with warming in Arctic tundra. New Phytologist 192(3): 689-698.

Deslippe, J.R., Hartmann, M., Grayston, S.J., Simard, S.W., Mohn, W.W. (2016). Stable isotope probing implicates Cortinarius collinitus in carbon transfer through ectomycorrhizal mycelial networks in the field. New Phytologist 210: 383-390.

Dudley, S.A., Murphy, G.P., File, A.L. (2013). Kin recognition and competition in plants. Functional Ecology 27: 898-906.

Gorzelak, M.A. (2017). Kin-selected signal transfer through mycorrhizal networks in Douglas-fir. UBC PhD Dissertation. Kin-selected signal transfer through mycorrhizal networks in Douglas-fir – UBC Library Open Collections

Horton, T.R. Mycorrhizal Networks. Springer, Netherlands. Ecological Studies 224, ISBN 978-94-017-7394-2.

Hussain, I., Rodriguez-Ramos, J.C., Erbilgin, N. (2019). Spatial characteristics of volatile communication in lodgepole pine trees: Evidence of kin recognition and intra-species support. Science of the Total Environment 692: 127-135,

Karban, R. (2015) Plant Sensing and Communication, Chicago: University of Chicago Press. 

Lian, C, Narimatsu, M., Nara, K., Hogetsu, T. (2006). Tricholoma matsutake in a natural Pinus densiflora forest: correspondence between above- and below-ground genets, association with multiple host trees and alteration of existing ectomycorrhizal communities. New Phytologist 171: 825-836.

Pickles, B.J., Wilhelm, R., Asay, A.K., Hahn, A., Simard, S.W., Mohn, W.W. (2016). Transfer of 13C between paired Douglas-fir seedlings reveals plant kinship effects and uptake of exudates by ectomycorrhizas. New Phytologist 214: 400-411.

Philip, L.J., Simard, S.W., Jones, M.D. (2011). Pathways for belowground carbon transfer between paper birch and Douglas-fir seedlings. Plant Ecology & Diversity 3: 221-233.

Roach, W.J., Simard, S.W., Defrenne, C.E., Pickles, B.J., Lavkulich, L.M., Ryan, T.L. (2021) Tree diversity, site index, and carbon storage decrease with aridity in Douglas-fir forests in western Canada. Frontiers in Forests and Global Change 4: 682076.

Robinson, A.J., Defrenne, C.E., Roach, W.J., Dymond, C.C., Pickles, B.J., Simard, S.W. (2022). Harvesting intensity and aridity are more important than climate change in affecting future carbon stocks of Douglas-fir forests. Frontiers in Forests and Global Change 5: 934067.

Schoonmaker, A.L., Teste, F.P., Simard, S.W., Guy, R.D. (2007). Tree proximity, soil pathways and common mycorrhizal networks: their influence on utilization of redistributed water by understory seedlings. Oecologia 154: 455-466.

Simard, S.W., Perry, D.A., Jones, M.D., Myrold, D.D., Durall, D.M., Molina, R. (1997). Net transfer of carbon between tree species with shared ectomycorrhizal fungi. Nature 388: 579-582.

Simard, S.W., Molina, R., Smith, J.E., Perry, D.A., Jones, M.D. (1997). Shared compatibility of ectomycorrhizae on Pseudotsuga menziesii and Betula papyrifera seedlings grown in mixture in soils from southern British Columbia. Canadian Journal of Forest Research 27: 331-342.

Simard, S.W., Perry, D.A., Smith, J.E., Molina, R. (1997). Effects of soil trenching on occurrence of ectomycorrhizae on Pseudotsuga menziesii seedlings grown in mature forests of Betula papyrifera and Pseudotsuga menziesii.  The New Phytologist 136: 327-340.

Simard, S.W., Durall, D.M., Jones, M.D. (1997). Carbon allocation and carbon transfer between Betula papyrifera and Pseudotsuga menziesii seedlings using a 13C pulse-labeling method. Plant and Soil 191: 41-55.

Simard, S.W., Jones, M.D., Durall, D.M., Perry, D.A., Myrold, D.D., Molina R. (1997). Reciprocal transfer of carbon isotopes between ectomycorrhizal Betula papyrifera and Pseudotsuga menziesii. New Phytologist 137: 529-542.

Simard, S.W., Asay, A.K., Beiler, K.J., Bingham, M.A., Deslippe, J.R., He, X., Philip, L.J., Song, Y., Teste, F.P. (2015). Resource transfer between plants through ectomycorrhizal networks In: T. R. Horton (ed.). Mycorrhizal Networks. Springer, Netherlands. Ecological Studies 224, pp. 133- 176. ISBN 978-94-017-7394-2.

Simard, S.W., Roach, W.J., Defrenne, C.E., Pickles, B.J., Snyder, E.N., Robinson, A., Lavkulich, L.M. (2020). Harvest intensity effects on carbon stocks and biodiversity are dependent on regional climate in Douglas-fir forests of British Columbia. Frontiers in Forests and Global Change 3: 88.

Simard, S.W., Roach, W.J., Beauregard, J., Burkart, J., Cook, D., Law, D., Schacter, T., Murphy-Steed, A., Zickmantel, A., Armstrong, G., Fraser, K.M., Hart, L., Heath, O.R.J., Jones, L., Sachs, N.S., Sachs, H.R., Snyder, E.N., Tien, M., Timmermans, J. (2021). Partial retention of legacy trees protect mycorrhizal inoculum potential, biodiversity and soil resources while promoting natural regeneration of interior Douglas-fir. Frontiers in Forests and Global Change 3: 620436.

Song, Y.Y., Simard, S.W., Carroll, A., Mohn, W.W., Zheng, R.S. (2015). Defoliation of interior Douglas-fir elicits carbon transfer and defense signaling to ponderosa pine neighbors through ectomycorrhizal networks. Scientific Reports 5, 8495.

Takigahira, H., Yamawo, A. (2019). Competitive responses based on kin-discrimination underlie variations in leaf functional traits in Japanese beech (Fagus crenata) seedlings. Evolutionary Ecology 33(4): 521–531.

Teste, F.P., Simard, S.W. (2008). Mycorrhizal networks and distance from mature trees alter patterns of competition and facilitation in dry Douglas-fir forests. Oecologia 158: 193-203.

Teste, F.P., Simard, S.W., Durall, D.M. (2009). Role of mycorrhizal networks and tree proximity in ectomycorrhizal colonization of planted seedlings. Fungal Ecology 2(1): 21-30.

Teste, F.P., Simard, S.W., Durall, D.M., Guy, R.D., Jones, M.D., Schoonmaker, A.L. (2009). Access to mycorrhizal networks and tree roots: importance for seedling survival & resource transfer. Ecology 90: 2808-2822.

Teste, F.P., Simard, S.W., Durall, D.M., Guy, R., Berch, S.M. (2010). Net carbon transfer occurs under soil disturbance between Pseudotsuga menziesii var. glauca seedlings in the field. Journal of Ecology 98: 429-439.

Twieg, B., Durall, D.M., and Simard, S.W. (2007). Ectomycorrhizal fungal succession in mixed temperate forests. New Phytologist 176: 437-447.

Van Dorp, C., Simard, S.W.,  Durall, D.M. (2020). Resilience of Rhizopogon-Douglas-fir mycorrhizal networks 25 years after selective logging. Mycorrhiza 30: 467-474.