Interview: The significance of ectomycorrhiza for Shorea robusta treesSubmitted by editor on 14 November 2023.
Nordic Journal of Botany interviewed Dr. Jitender Thakur about his study Selection of efficient ectomycorrhizal fungi for improved growth, biomass and nutrient uptake of Shorea robusta seedlings which is currently available to read as an Early View article. Together with his co-author Narender Singh Atri, Dr. Thakur isolated and identified three ectomycorrhizal associates of Shorea robusta, also called Sal tree, in the northwest Himalayas, India. The Sal tree forests are environmentally and ecologically important to the region, however, poor regeneration has led to a decrease in forest cover. Read below how ECM inoculation can help the recovery of the Sal forest!
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How did you get into researching Shorea robusta?
I got into researching Shorea robusta because of its ecological and economic importance. I am particularly interested in researching Shorea robusta because of its potential to help address some of the major challenges facing the region, such as climate change, deforestation, and poverty. For example, Sal forests can help to mitigate climate change by sequestering carbon dioxide from the atmosphere. Sal trees can also be used to restore degraded forests and provide sustainable livelihoods for local communities.
Sal forest density has significantly reduced during the past years and is one of the major problems of forest department and ministry of environment. That is why protection and afforestation of Sal tree is necessary. The Sal nursery industry is also facing problems because the seeds require immediate sowing along with appropriate ectomycorrhizal fungal symbionts. Mycorrhiza have been reported to improve the seedling establishment and performance as it facilitates the mobilisation of immobile nutrients including nitrogen (N) and Phosphorus (P) for the plants.
In view of the problems associated with the establishment of S.robusta seedlings the present investigations have been centred around identification of ectomycorrhiza (ECM) associates of S.robusta and to study the impact of ECM on regeneration and growth of this plant.
What is the significance of Shorea robusta?
Shorea robusta, also known as Sal, is a significant tree species for a number of reasons.
Ecological importance: Sal forests are home to a wide variety of plants and animals and they play a vital role in the region's biodiversity and ecosystem services. Sal forests help to regulate the climate, protect water resources and prevent soil erosion. Sal forests can be used to restore degraded land. Sal trees are relatively fast-growing and can tolerate a wide range of soil and climatic conditions.
Socio-economic importance: Sal timber is a valuable economic resource, used for a variety of purposes including construction, furniture making, paper production, timber, fuelwood and fodder. Sal timber is known for its strength, durability and resistance to decay. The tree is also used to make honey, oil for cooking and lighting, tannin, leaf plates and bowls and for medicinal purposes.
Cultural importance: Sal trees have a long history of cultural and religious significance in the region. Sal wood is used to make temples and other religious structures and Sal leaves are used in traditional ceremonies and festivals.
Shorea robusta is a truly remarkable tree, with a wide range of benefits for people and the environment. It is important to conserve and manage Sal forests sustainably so that they can continue to provide these benefits for generations to come.
What are the ecological challenges for Shorea robusta forests?
Sal forest density has significantly reduced during the past years. The overall change has been estimated to be 42.11 % of the total forested area. The primary reason for decreasing Sal forest cover has been attributed to the poor regeneration. The Sal seeds start germinating just before seeds detaches from the tree. Therefore, these seeds immediately need appropriate moisture conditions, nutrients and fungal associates for their establishment. The Sal nursery industry is also facing problems because of recalcitrant nature of the seeds which require immediate sowing along with appropriate ectomycorrhizal fungal symbionts.
Are there anthropological threats?
Yes, there are anthropological threats to Shorea robusta forests. These threats include:
Deforestation: People clear Sal forests for agriculture, development, and mining projects. This is the biggest threat to Sal forests.
Overgrazing: Livestock overgraze Sal forests, damaging seedlings and saplings and preventing them from growing into mature trees.
Fuelwood collection: People collect fuelwood from Sal forests for cooking and heating. Over-harvesting of fuelwood can deplete Sal forests and make them more vulnerable to other threats.
Non-timber forest product collection: People collect non-timber forest products (NTFPs) such as honey and medicinal plants from Sal forests. Over-harvesting of NTFPs can damage Sal forests and reduce their productivity.
Forest fires: Forest fires are a major threat to Sal forests, especially during the dry season. Forest fires can damage or destroy large areas of Sal forests.
These activities can lead to the loss of Sal trees, the fragmentation of Sal forests, and the degradation of Sal forest ecosystems.
You cultivated three ECMs from established S. robusta roots. Are there more? Are these the main ECMs?
Yes, there are more ECMs that can be cultivated from established S. robusta roots. In fact, there is a wide diversity of ECMs that are associated with S. robusta trees. Some of the most common ECMs that can be cultivated from S. robusta roots belong to genus Russula, Lactarius, Amanita, etc.
Do they play different roles and do they occur separately or simultanously?
Yes, the different ECMs that are associated with S. robusta trees play different roles. Some ECMs specialize in helping the tree to uptake specific nutrients, while others specialize in protecting the tree from diseases and pests.
All of these ECMs can occur on the roots of the same tree and they can all work together to improve the health and productivity of the tree.
Researchers are still learning about the specific roles that different ECMs play in S. robusta forests. However, it is clear that ECMs play an important role in the health and productivity of S. robusta trees.
Why do you think you found Lactarius which was not found in other studies?
In India, ECM studies are exclusively focused on the temperate and boreal ecosystems, whereas there is little information on ECM communities of tropical and sub-tropical ecosystems. As far as the study of ECM association of these fungi with Sal trees is concerned, not much work is available and many associated ECMs are not yet identified.
Have you considered testing inoculation with a combination of ECMs?
In the present study I have not tested the inoculation with combination of ECMs. I am currently planning to conduct experiments to test the effects of inoculating Shorea robusta trees with a combination of ECMs. I am particularly interested in testing the effects of inoculating trees with a combination of ECMs that specialize in different things, such as ECMs that specialize in phosphorus uptake and ECMs that specialize in disease resistance.
I believe that inoculating Shorea robusta trees with a combination of ECMs could be a promising way to improve the health and productivity of these trees. This could also help to make Shorea robusta forests more resilient to climate change and other threats.
What is the significance of your findings?
My findings on the diversity and importance of ECMs in Shorea robusta forests are significant for a number of reasons.
They provide new insights into the role of ECMs in S. robusta forests. ECMs are known to play an important role in the health and productivity of trees, but my findings suggest that they may play an even more important role in S. robusta forests than previously thought.
Three ECM associates of Shorea robusta are confirmed using synthesis of ectomycorrhiza viz. Russula kanadii, R. cyanoxantha and Lactarius shiwalikensis. The results also confirm the role of Russula kanadii, R. cyanoxantha and Lactarius shiwalikensis in the macro- and micro-nutrition of Shorea robusta. All the symbionts evaluated resulted in remarkable increase in the nutrient content of the Sal seedlings. ECM infections have also resulted in the inhibition of translocation of heavy metals from roots to shoots, which otherwise have negative effect on the growth of Sal seedlings. From the result of this study, it becomes clear that it is possible to replace chemical fertilisers by ECM fungi in the nursery production of S. robusta. In addition, it was established that the use of these selected ECM fungi can be an effective and more environmentally friendly approach to Sal nursery growth. Thus, ECM colonisation is particularly important when the targeted production of S. robusta seedlings is for disturbed and/or arid ecosystems. The ECM inoculation can result in a decreased time to planting, less fertilizer input, higher seedling survival and healthy growth resulting in better quality S. robusta nursery stock with reduced production cost.
The results highlight the importance of conserving ECM diversity. ECM diversity is important for the health and resilience of S. robusta forests. By conserving ECM diversity, we can help to ensure that S. robusta forests are able to withstand the challenges of climate change and other threats.
The results suggest new ways to manage S. robusta forests sustainably. My findings suggest that inoculating S. robusta trees with a combination of ECMs could be a promising way to improve the health and productivity of these trees. This could also help to make S. robusta forests more resilient to climate change and other threats.
These findings have the potential to make a significant contribution to the management of S. robusta forests and to the conservation of this important ecosystem.
Anything else you would like to mention about your studies?
I would like to mention that my studies are still ongoing. I am currently working to further investigate the diversity and importance of ECMs in Shorea robusta forests. I am also working to develop new methods for cultivating ECMs from S. robusta roots and to test the effects of inoculating S. robusta trees with a combination of ECMs.
I am excited about the potential of my research to improve the management of Shorea robusta forests and to promote their sustainable use. Shorea robusta forests are a vital part of the ecosystem and they provide a wide range of benefits to people and the environment. By conserving and managing Shorea robusta forests sustainably, we can help to ensure that these benefits continue to be provided for generations to come.