Effect of terrestrial cyanobacterial mat "Ishikurage" on the growth of Japanese pampas grass in infertile devastated soils

Abstract

To investigate the effect of the terrestrial cyanobacterial mat "Ishikurage" on the growth of the Japanese pampas grass, Miscanthus sinensis, we conducted a pot experiment with two infertile soils, granitic soil and volcanic deposits. "Ishikurage", composed of Nostoc sp., was collected from the campus of Yamaguchi University. Four experimental treatments were conducted: control, treatment with ammonium nitrate, treatment with dry sterilized "Ishikurage", and treatment with live "Ishikurage". After three or four months, total dry weight of plants in the treatment with live "Ishikurage" as well as that in the treatment with ammonium nitrate was higher than the control treatment. That in the treatment with dry sterilized "Ishikurage" was the highest of all. From the results of the nitrogen dynamics, it was evident that the increase of plant growth in these terms resulted from the uptake of organic nitrogen leached from the dry sterilized "Ishikurage" into the soil and the nitrogen mineralized from that in the application with a dry sterilized one. The increase of total nitrogen in the pot in the treatment with live "Ishikurage" was the highest of all. This demonstrates the excretion of nitrogen fixed by live "Ishikurage" and the mineralization of "Ishikurage" itself. From these results, it is anticipated that "Ishikurage" can be used as an effective natural material resource of nitrogen for the rapid recovery of vegetation in infertile devastated sites. Live "Ishikurage" effectively increases the total nitrogen in an infertile ecosystem.