Fungal assemblage and leaf litter decomposition in riparian tree holes and in a coastal stream of the south-west India

Abstract

Assemblage of aquatic hyphomycetes and decomposition of banyan leaf litter (Ficus benghalensis) were assessed in riparian tree holes and in a tropical coastal stream during rainy season up to 8 weeks in south-west coast of India. Although fungal assemblage was similar, leaf decomposition and leaf chemical changes differed between tree holes and the stream. Out of the 18 aquatic hyphomycetes, 17 were common on leaf litter in tree holes and the stream. Anguillospora longissima, Flagellospora curvula, Lunulospora curvula, Triscelophorus acuminatus and T. konajensis were the top five species in tree holes and the stream. The species richness was the highest during the second week in tree holes (11 species) and the sixth week in the stream (14 species), while the conidial output was the highest in tree holes and the stream during sixth week. The daily decay coefficient (k) was significantly faster in streams than in tree holes. Mass loss of banyan leaves between tree holes and the stream was positively correlated with conidial output by the aquatic hyphomycetes. The estimated half-life (t50) of leaf decomposition ranged between 70 days (stream) and 128 days (tree holes). Organic carbon in leaf litter gradually decreased, while nitrogen content decreased up to 1–2 weeks and then gradually increased over the incubation period. Ergosterol showed a gradual increase in tree hole litter, while it attained its peak in 4 weeks and declined thereafter in the stream litter. Loss of phosphorus concentration was rapid in the stream than in tree holes. Total phenolics concentration in leaves decreased rapidly in the stream than in tree holes. However, low dissolved oxygen in water and the slow release of phenolics from the leaf litter showed negative impact on the fungal activity and the rate of leaf decomposition in tree holes.