Comparative diversity and composition of nitrogen-fixing cyanobacteria in three different land use systems of upper Assam

Abstract

Three contrasting land use systems: reserve forests, rice fields and coal fields located at Upper Assam region of North East India were explored for documenting diversity and species composition of N₂-fixing cyanobacteria. Altogether 24 taxa (16 heterocystous and 8 non-heterocystous) belonging to nine different genera were isolated. The Shannon’s diversity index was highest in rice fields (1.946), followed by reserve forest (1.485) and coal fields (0.975). Results of relative abundance revealed the dominance of Nostoc and Anabaena in the reserve forests and rice fields, whereas both were missing in the coal contaminated sites. Oscillatoria was the dominant genus and the species belonging to this genus were abundant in coal field areas. Canonical Correspondence Analysis revealed that environmental factors and physico-chemical properties cumulatively decided the composition and distribution of cyanobacteria in different land use systems of the region.

Key Words: Diversity, Cyanobacteria, Land use, Reserve forest, Rice fields, Coal fields