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In addition to its mission of participative and sustainable reforestation, the arboRise foundation has the statutory objective of “experimenting with natural reforestation methods that enhance biodiversity“. That’s why we asked ourselves how we could use mushrooms to make our trees grow.

We’ve known for several years that trees and fungi interact. In a nutshell:

• Some fungi link up with tree roots via their mycelium to help each other.
• Trees provide sugar to fungi in exchange for water and mineral salts
• Trees that benefit from this grow better

There are three types of fungi:

Saprophytes

• Saprophytic (or saprophagous) fungi feed on dead or decomposing organic matter. They play an essential role in the decomposition of dead organic matter, such as leaves, branches and plant debris. By breaking down complex organic matter into simpler compounds, they release nutrients into the soil.
• Although direct interactions between saprophytic fungi and mycorrhizal fungi are limited, saprophytic fungi contribute to the availability of nutrients, which can benefit mycorrhizal fungi by providing organic substrates. Since saprophytes feed on dead matter, they are not known to attack the seeds of living trees directly.
• Generally speaking, in cultivated soils, 20% of saprophytes and 80% of bacteria remain. When the field is left fallow, the saprophytic fungi grow and the pathogens disappear. So these saprophytic fungi play an important role in revitalising soil that has been impoverished by cultivation.

Endomycorrhizal fungi

• The mycelia of endomycorrhizal fungi penetrate plant roots and form structures called “arbuscules” or “vesicles” inside the root cells of the host plant. Thanks to this symbiosis, these fungi improve the removal from the external environment of the mineral nutrients they provide to their plant partner, the tree.
• In tropical zones, endomycorrhizal fungi dominate, although agriculture has a very negative impact on these arbuscular fungal communities (Arbuscular mycorrhizal fungal communities in sub-Saharan Savannas of Benin, West Africa, as affected by agricultural land use intensity and ecological zone). They are more common in the Sahelian-Sudanese zone, where the climate is drier, and associate with tree species such as :

• Endomycorrhizae generally do not produce sporocarps (what are commonly known as “mushrooms”, visible on the surface, which contain the spores needed for reproduction) and are therefore only present in the soil, around the roots of host plants. To collect inoculum, part of the root of the host tree must be removed.
• Endomycorrhizal fungi reproduce mainly asexually, producing spores inside the roots of the plants with which they form a symbiosis. These spores, known as arbuscules, are specialised structures that enable the fungus to propagate within the root cells of the host plant.

Natural inoculum is the simplest and least expensive way of achieving mycorrhization, and there is a very simple technique :

• A few weeks before the start of the rains, fill a sock with rice and bury it under a mature tree of the Parkia, Pterocarpus, Khaya, Prosopis, Erythrophelum, Daniellia, Anogeissus or Adansonia species (there is a high probability that this tree harbours endomycorrhizal fungi in its roots).
• Dig up the soil after a few weeks: the rice is full of mycorrhizae (white filaments). But be careful: the hyphae of the mycelium are fragile and must not be cut. A hypha isolated from the mycelial network will not survive. So remove the sock and the soil around it
• Bury this soil sock in the most humid part of the soil in the reforested area, close to the sown seeds. As soon as the seeds germinate, they will bind with the mycelium of the fungus, which will help them to grow.

Ectomycorrhizal fungi

• Ectomycorrhizal fungi are capable of mobilising and transferring to the host plant nutrients trapped in the soil’s organic matter (carbon, but also nitrogen, particularly that found in chitin). They regulate the balance between CO2 in the atmosphere and the amount of nitrogen in the soil by accelerating or reducing photosynthesis. They inhibit respiration in the soil by micro-organisms, reducing the outflow of carbon from ecosystems. Finally, the litter from ectomycorrhizal trees decomposes slowly due to the presence of secondary compounds that slow down the degradation of organic matter, helping to sequester carbon in the soil. These ectomycorrhizal symbioses therefore play a key role in climate regulation. Ectomycorrhizae also play a major role in the absorption of minerals such as phosphorus and potassium.
• Ectomycorrhizal fungi are rarer. They tend to be found in the tropical rainforests of the Guinean zone, where they associate with tree species such as Afzelia, Isoberlinia and Uapaca. This is particularly true of Isoberlinia and Uapaca, which grow on poor, leathery soils.
• In Guinea Forestière, ectomycorrhizal fungi are most often found in the Russula, Amanita and Lactarius genera. Ectomycorrhizal fungi have sporocarps (the fungi visible on the surface of the soil), so it’s easier to harvest their spores!
• The particular advantage of ectomycorrhizal fungi is their ability to supply organic nitrogen from the soil to the tree.

How can ectomycorrhizal fungi be used?

• Natural inoculum is the simplest and least expensive way of achieving mycorrhization. It can take the form of soil and humus from old plantations containing ectomycorrhizae, crushed sporophore, spores or excised roots. Inoculation of nurseries with spores has been the most common practice due to the number of spores available from fungi that fruit abundantly in forests and plantations.
• In practice, roots can be praline-coated with a spore suspension or sprinkled with dry spores. Seeds can also be coated with spores just before sowing.
  • Harvest mature ectomycorrhizal fungi from Afzelia, Isoberlinia or Uapaca forests around May.
  • Look for a dark place, away from light
  • Place 10 mushrooms in each 10-litre bucket of water
  • Crush and mix until you obtain a liquid purée of mushroom flesh full of spores
  • Leave to infuse for 24 hours
  • Add a spoonful of sugar to the solution and stir
  • Soak the tree seeds in the mushroom purée and mix
  • Sow the praline seeds

An interesting observation: Among the 40 species of arboRise trees, the early season species are more likely to use mycorrhizae:

This is not surprising: January-February is the dry season and March is the hottest month. So it’s very useful for these tree species, which suffer from the climate, to be able to associate with fungi underground that provide them with water in exchange for sugars.

What are we going to test in 2024?

• The NGO AGIDE in Togo, headed by Mr Kossi Agbalenyo, is a specialist in the use of mycorrhizae in agriculture and reforestation. MYCOTRI, a 100% natural product marketed by AGIDE, contains spores of saprophytic fungi, which we will use to coat our tree seeds. These fungi will decompose the organic matter present in the reforested land and reduce the quantity of bacteria in soil that has been impoverished by cultivation. This will encourage the arrival of ectomycorrhizal and endomycorrhizal fungi, which will promote the growth of our trees.
• We are going to encourage a few interested land families to test both methods on their fields:
  • grow endomycorrhizal fungi using the sock method
  • grow ectomycorrhizal fungi to make spore mash and soak the seeds in it

To find out more :

A book: The ectomycorrhizal fungi of forest trees in West Africa, Amadou Bâ, Robin Duponnois, Moussa Diabaté and Bernard Dreyfus, 2017.

Watch lectures by Marc-André Selosse, a soil microbiologist specialising in mycorrhizae:

Biological Functioning of Soils: https://www.youtube.com/watch?v=DAOdifyrfp4

• Mycorrhizae and mycorrhizal networks : From 4’47’20 to 5’35’30 (ectomycorrhizae: 4’56”30)
• Tropical forest diversity and succession: from 5’43’57 to 5’51’46
• Mycorrhizae and competition between species: 5’53’52 to 6’07’35 (depending on the mix of tree species per village, the results will differ with Mycotri because it will favour certain species which will take advantage over others).
• Mushrooms are also in the leaves! : 6’24’27 à 6’29’00

Mycorrhization – Mycorrhizae

• Ectomycorrhizae https://www.youtube.com/watch?v=pmjWysrPyJI
• Contribution of non-organic minerals by ectomycorrhizae: https://www.youtube.com/watch?v=6KbnCzU9yRM
  • 4’20”: some ectomycorrhizae can provide the tree with mineral resources
  • 8’37”: inoculation difficult only with spores… “mycorrhizal fungi are often found in dead wood because dead wood stores the water that the fungi seek”, “in tropical zones decomposition is strong and endomycorrhizal fungi are sufficient”).
• Applications https://www.youtube.com/watch?v=pJPze25Vods 6’12” renaturation of agricultural land: reforesting land cultivated with artificial fertilisers is difficult because there are no mycorrhizae left. Mycorrhizae must be added to nursery plants.

Seed harvesting began in the villages in the second group (you’ll recall that the 26 villages are divided into three groups corresponding to the ripening period of the trees: the first group of villages harvests seeds from trees ripening in January-February, the second group harvests seeds from trees ripening in March-April and the third group harvests seeds from trees ripening in May-June).

The harvesting technique differs depending on the tree species. Here, on the Uapaca Somon, the women use long, light bamboos at the end of which they attach blades to pluck the clusters of seeds from the top of the tree.

For other species, the women collect the seeds that have fallen to the ground:

All the seed families have been fitted with large tarpaulins to make it easier to collect the seeds (see news item ‘Equipment for the families’). In these images, the harvesters are not using them.

The seeds will then be dried before being taken to the village for counting and mixing.

The Guinean families involved in the project are extremely poor. They lack clothes and tools, even for their usual farming activities. In the first year of the project, the participants had asked for a distinctive sign that they belonged to the project, which we provided, although we were sceptical about its real usefulness. In the second year, we provided tarpaulins for the seed families and boots for the field families:

• The large ARBORISE-GUIDRE tarpaulins are placed under the seed tree to collect the seeds, for the duration of the harvest phase.
  • The tarpaulin makes the seeds clearly visible and facilitates harvesting.
  • Above all, it protects against animals that might hide in the grass or branches under the trees.
  • It also protects against abrasions caused by thorny grasses.
• ARBORISE-GUIDRE boots protect the lower legs of land families as they move around and work on sowing, clearing and establishing protective strips.

In 2023, following the local stakeholder consultation, we opted for a more detailed approach: each family was given the opportunity, by means of a questionnaire, to choose the individual equipments that would be most useful to them. As you can see below, the choices were mainly for tarpaulins, mackintoshes and boots:

To foster collaboration and solidarity, we also proposed collective equipments in each village. The seed families, mostly women, opted for fences and the field families, mostly men, chose ploughs:

But why did the women choose fences? In most villages, the women work together to set up market-gardening areas where they grow vegetables (onions, aubergines, etc.), each on a small plot, rather like allotments. These market garden areas need to be protected from livestock and wild animals, usually by wooden fences. In tropical regions, this dead wood decomposes very quickly because of the humidity in the rainy season and because of insects. The women therefore have to continually fetch wood to maintain the fence, and this takes up a lot of their time, on top of all the other tasks they have to perform. It’s easy to see why mesh is useful: it’s more durable and saves a lot of time.

Transporting 326 tarpaulins, 160 mackintoshes, 57 pairs of boots, 104 rolls of netting and 25 ploughs is no mean feat, especially on Guinean roads. But the small bus, packed to the rafters, fulfilled its mission perfectly:

The equipments arrived in Linko, where it was divided into 26 batches (one for each village):

In the end, each Community Management Committee received the collective equipment in its village, and each family received the individual equipment it had ordered. We could verify this in the villages of Linko, Kala, Sékamadou and Koyola during our field visit in March.

All in all, our project is helping to make work in the communities safer and less arduous, and to put smiles on people’s faces:

January 16 is Saint Marcel’s day, the saint of the seed growers. That’s for sure a good day to launch the 2024 campaign in the sub-prefecture of Linko.

This will be the third and final year of the reforestation cycle in the Commune Rurale of Linko. Next year sees the start of a new three-year cycle in the neighbouring sub-prefecture of Damaro. But before that, there’s still a lot to do:

• First of all, we need to check that the 2023 work has been completed and that the land reforested to date has been properly marked and protected by effective firebreaks.
• Then we need to repeat the fire prevention and land maintenance instructions.
• This is also an opportunity to highlight the good examples: the model protective strips, the high germination rates, the hedgerows provided, and so on.
• Finally, it’s time to start harvesting seeds, plan delivery dates, identify new plot families and so on

The objective of the 2024 campaign in Linko is to restore more than 500 hectares with a 5’000’000 seeds of 40 native tree species.

It was during this first tour of the villages in the first group that Mrs Saran Keita, in Fanzan, showed us the superb pigeon pea seedlings sown in May 2023, whose harvest looks very promising, as her smile proves:

Bringing together all the families in Linko’s arboRise family cooperative has several objectives:

1. foster mutual trust between families
2. provide a forum for exchanging best practice
3. enable the families concerned to decide for themselves, without any involvement from arboRise, how the income from the carbon credits is to be distributed.

This deserves some explanation.

At the outset, some people thought that the project would somehow create competition between family plots and distribute more money to the families on whose plots the trees grow best. A form of rivalry between families and villages was then perceptible, with each criticising the others, convinced that they belonged to those who were doing well (an attitude not so different from what we see in Europe, where everyone considers themselves to be very virtuous in terms of CO2 emissions, compared with the others).

The auditor of our carbon certification standard will not be measuring the biomass of each of the 6,000 hectares that we will have reforested in 9 years’ time. He or she will measure the carbon on a representative sample. And the project’s carbon income will be calculated on the basis of this sample.

If, by chance, there are only lots with a high density of trees in the sample, everyone will be happy: the sample average will be high and all families – not just the families whose lots have been measured – will be able to receive high incomes. But if the sample includes plots whose trees have been cut down, everyone will suffer.

The average biomass measured in the sample is therefore a common good shared by all the families. All the families have an interest in helping each other to ensure that all the plots of land are in good health and that this common good bears fruit. This is why the cooperative was created: to provide a structure that facilitates this collaboration for the next 27 years. In this way, the arboRise project strengthens community solidarity (see our ethical charter). The hand that calls for help is transformed into a chain of people helping each other:

The statutes of the cooperative initiated by arboRise draw heavily on the research of Elinor Ostrom, winner of the Nobel Prize in Economics for her work on the good governance of common goods. In particular, they aim to guarantee gender parity within the Cooperative Committee, the body of the Cooperative that will propose the income distribution key to the members. Don’t hesitate to ask us for more details about the profit-sharing mechanism, if you’re interested.

Founding a co-operative means bringing together all the co-operators, 265 people in our case. Plus the representatives of the Community Management Committees in each village and other representatives of the authorities… in the end, there were more than 300 of us.
300 guests, for whom we had to provide accommodation, food, a meeting place, etc. etc. And all this in the middle of the bush.

Once again, our partner GUIDRE performed this task brilliantly. The families from the most remote villages arrived the previous evening and were accommodated by families in Linko. The rural radio station was able to broadcast a round table discussion with some of the beneficiaries (photo bottom right). And everything went smoothly on the day of the inaugural meeting. It must be said that we had anticipated things well, having prepared the event with the Community Management Committees in May. A big THANK YOU to our partner GUIDRE for its professionalism and commitment.

The next step is to support the process of electing the Cooperative’s governing bodies at the next Annual General Meeting.

To increase the environmental impact of a carbon project, the Gold Standard requires each project to define a conservation perimeter equivalent to 10% of the project area. This area must be protected from any exploitation activity and is not eligible to receive income from carbon credits. It is truly a perimeter dedicated to biodiversity.

This is easier said than done, because in the case of arboRise it means finding more than 180 hectares for each cycle of 1,500 hectares. Fortunately, the communities we work with are very interested in preserving their environment. They know exactly which areas of the village are important. These include

• the spring heads (where water gushes out of the ground), which are very fragile and vital for providing the water needed in the village: for cooking, for market gardening, for cleaning, etc.
• sacred forests, which often surround the villages and into which it is forbidden to penetrate under threat of very serious trouble. These remnants of primary forest are real reservoirs of biodiversity, providing food for animals and seeds for the surrounding area. These forests are also under threat as modernity replaces ancestral traditions.
• groves where the ritual initiations of young men and women take place.
• wetlands: streams, marshes, low-lying areas, etc. that are often home to wildlife.

These sensitive and precious areas are currently only protected by tradition and its guardians. Under the Forestry Code, the Guinean government provides support for communities wishing to protect certain areas. It is possible to put these areas under protection, which legally protects them for 99 years. In practical terms, this means that these areas are now also under the protection of the State, represented by the Water and Forestry Department of the Ministry of the Environment and Sustainable Development. Penalties are provided for anyone guilty of damaging these protected areas.

Each village deliberated to identify the area or areas to be protected, usually sacred forests. These areas were then geo-referenced by our partner GUIDRE, whose director is regional manager of the ICCA consortium. Each village made an official request to the Water and Forestry Department for the areas to be set aside, and finally the Prefect of Kérouané signed the 25 certificates for the areas to be set aside, covering a total area of almost 200 hectares, thus protecting them from anthropic pressure.

Map of conservation areas:                                                                              A prefectoral certificate:

For the past year, we have been measuring NDVI, i.e. biomass on reforested land, using images from the European Union’s Sentinel II satellite. To validate this tool, we need to ensure that the satellite measurement values match the reality observed in the field.

That’s what we wanted to find out during our latest supervisory visit. We visited 15 sites to be reforested in 2021 and 2022, some of the most extreme in terms of biomass measured by satellite: basically the best and worst sites. Of this non-representative sample, the observations on 11 plots correspond to the satellite values (70%). For the remaining 4 sites, the satellite values are too negative in 3 out of 4 cases.

Satellite measurements could therefore be used to help our beneficiaries by telling them where their land is situated, in terms of biomass, in relation to all the other land. This will enable them to take informed action, for example by enriching their plots with new seeds or wildings if the biomass is below average.

Here are a few examples of good matches:

Field 2021-034, near Oussoudougou. The good NDVI value for February 2023 in the dry season (0.211) reflects the reality on the ground:

Field  2021-015, near Diaragberela. The poor NDVI value for February 2023 in the dry season (0.156) reflects reality in the field:

Field  2021-016, near Diaragberela. The relatively good NDVI value for February 2023 in the dry season (0.203) reflects reality in the field:

Field  2021-056, near Konko. The poor NDVI value for February 2023 in the dry season (0.143) reflects the reality on the ground:

Field  2021-044, near Fansan. The poor NDVI value for February 2023 in the dry season (0.183) reflects reality on the ground:

Field  2021-031, near Talinko. The poor NDVI value for February 2023 in the dry season (0.174) reflects the reality on the ground:

Field 2022-035, near Talinko. The good NDVI value for February 2023 in the dry season (0.262) reflects the reality on the ground:

And here are the 4 cases of non-correlation:

Field 2021-004, near Linko. The NDVI value for February 2023 in the dry season (0.152) is poor and does not fully reflect the reality on the ground, which is better, perhaps due to the effect of the rainy season:

Field 2021-009, near Linko. The NDVI value for February 2023 in the dry season (0.163) is poor and does not at all reflect the reality on the ground, which is much better:

Field 2022-150, near Linko. Field observations do not correspond with the correct NDVI value for February 2023 in the dry season (0.226):

Field 2022-191, near Diaragberela. Observations in the bushy terrain do not correspond to the incorrect NDVI value (0.182):

The Scientifica science fair hosted arboRise on 2 and 3 September 2023. Organised by ETHZ and the University of Zurich, it is the largest science popularisation event in Switzerland.

Thanks to the research fund made available by ETH for Development, we were able to carry out a number of important field research projects.

1️⃣ https://arborise.ch/experimentation-sur-les-boulettes-de-graines/?lang=en
2️⃣ https://arborise.ch/premiers-resultats-de-lexperience-sur-les-seedballs/?lang=en
3️⃣ https://arborise.ch/experience-des-seedballs-resultats-finaux/?lang=en
4️⃣ https://arborise.ch/parties-de-jeu-a-diaradouni/?lang=en

Thank you to ETH4D for inviting us to the Scientifica stand. We were able to share our learnings with many visitors 👨‍👩‍👧‍👦 and also hold promising discussions with potential future partners!

We’re really pleased to have been able to contribute to science-based natural solutions through this research.

Is a tree planted to save the planet really worth it? We sometimes hear this question. So, true or false?

“Planting trees takes a lot of time.”

True and false. True: a forest takes around thirty years to reach its maximum size. What we forget is that it’s precisely during these early years that trees absorb the most CO2! After that, a mature forest conserves carbon. It still absorbs carbon, of course, but it releases almost as much in the form of decomposing dead wood. So a reforestation project has an immediate impact on the climate.

“In the beginning, trees are very small.”

True. The trees we plant reach 2 meters after 3 years. But what we forget is that there are a lot of them: about one small tree every 3 square meters, bearing in mind that we sow 10,000 seeds per hectare (one hectare = 10,000 square meters), of which 6,000 germinate and about half survive after 3 years. 3,000 little trees on one hectare is a lot of biomass! And our tree-planting project covers 500 new hectares a year, so 1,500,000 saplings a year!

“Tree plantations are fragile.”

True. But a nuclear power plant shut down because of technical problems or because there isn’t enough water in the rivers to cool it down, is also fragile. A dam without water because it stops raining is just as fragile. A photovoltaic panel on a cloudy day is just as fragile. We have to stop believing that nature is more fragile than technology. Nature will outlive us, not our machines.

“Reducing CO2 emissions is better than planting trees.”

True and false. Of course it’s important not to continue emitting carbon into the atmosphere, because if we exceed 380 Gigatons of CO2 by 2032, the average temperature on earth will rise dangerously. So it’s important to give up fossil fuels, increase energy efficiency and consume less. But sooner or later, all that carbon will have to be removed from the atmosphere! And that can only be done with each tree planted.