New records of relationship between soil macro elements and the distribution of heterocystous cyanobacteria in paddy fields, wheat fields and woodland in Golestan province

Heterocystous cyanobacteria play a significant contribution in maintaining soil fertility. Despite the occurrence of paddy fields, wheat fields and woodland in north Iran, less attention has been paid to the role of cyanobacteria in these ecosystems. In this study an attempt was made to growing soil inoculums on BG-11 medium. Their incidence with N, P, K, C, pH and EC of soils was also determined. Totally twenty species were identified in paddy fields, twelve in wheat fields and three in woodland. The results showed that species of Nostoc and Anabaena are ubiquitous in all sites except one of paddy field stands, where its EC was the highest and Calothrix stagnalis was the only species found in the stand. It is suggested that this strain is probably resistance to salinity. This is supported by statistical analysis of species and colonies number with EC that showed negative correlation. The forest had higher percentage of N, P, K, and C than other regions differed mainly in number of species and also there isn’t any branching species in this region. The scarcity of cyanobacteria in forest can be probably limited by low pH and EC. However soil analysis showed that phosphorous amount has a highly positive correlation with the frequency of cyanobacteria in all of stands.