ABSTRACT

The Myristica swamps of the Western Ghats, a biodiversity hotspot, are unique ecosystems that play a critical role in flood control, groundwater maintenance and biodiversity conservation. These swamps, dominated by endemic species like Myristica fatua and Gymnacranthera canarica, are relics of ancient forests, while the adjoining evergreen forests exhibit high species diversity with a dense canopy. Arbuscular Mycorrhizal (AM) fungi, crucial for nutrient uptake and plant resilience, were studied in these ecosystems to understand their distribution and ecological dynamics during 2023-2024 by selecting Kathlekan and Thorme in the Sirsi forest division of Uttara Kannada.
Soil analysis revealed similar characteristics in both ecosystems, with slightly acidic, silty clay loam soils and low nutrient levels. AM fungal spore density being higher and more variable in the evergreen forest, with spore densities ranging from 105.50 to 181.33 spores per 100g of soil across both ecosystems. A total of 114 AM fungal morphotypes were identified, classified into 30 species across five genera, with Glomus and Acaulospora being dominant.
In the Myristica swamp, AM fungal root colonization was high and uniform across tree species (82-84%), while the evergreen forest exhibited more variability in colonization rates (76-91%). Diversity indices showed that the evergreen forest had higher AM fungal diversity and species richness compared to the swamp forest. Correlation analysis revealed a strong positive relationship between relative abundance and isolation frequency in both ecosystems, although the relationships between spore density, root colonization and species richness were complex and varied between the two forests. These findings underscore the distinct AM fungal communities in the Myristica swamp and adjoining evergreen forests, emphasizing the need for further research and conservation efforts to protect these ecologically significant habitats.